FR2840605A1 - Manufacture of alkanes used as fuel, involves contacting alkane starting material with metal catalyst comprising metal(s) and specific metal bonded to hydrogen atom(s) and/or hydrocarbon radical(s) - Google Patents

Abstract

An alkane starting material is reacted with metal catalyst (2) comprising metal(s) and metal (Me) bonded to hydrogen atom(s) and/or hydrocarbon radical(s), to obtain alkane. An Independent claim is included for activation of metal catalyst.

Description

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 The present invention relates to a process for the manufacture of alkanes using, in particular, catalytic reactions for the homologation of alkanes.

 Alkanes are generally difficult to implement in reactions because of their high chemical inertness, and are mainly used as fuels and energetic materials.

 Numerous studies have been developed for the purpose of converting alkanes to their lower homologs, in particular by hydrogenolysis reactions, that is to say carbon-carbon bond cleavage and hydrogen addition reactions. each portion. These reactions are carried out by contacting alkanes with hydrogen in the presence of a hydrogenolysis catalyst generally chosen from transition metal catalysts, in particular in the form of a mass, or in the form of films or metal particles, in particular supported on oxides.

 More recently, there has been a need to transform alkanes into their higher homologues, in particular with the aim of upgrading light alkanes, especially methane. Such transformations can be obtained by homologation reactions making it possible to convert light alkanes into heavier alkanes, in particular by means of metal catalysts capable of carrying out carbon-carbon and carbon-carbon linkage scission and recombination reactions and possibly carbon-carbon bonds. metal and carbon-hydrogen. Various methods are provided for carrying out such reactions. In particular, the metathesis of alkanes can be carried out in higher and lower homologues, according to the process described in international patent application WO 98/02244. Cross metathesis of alkane can also be carried out in the presence of an organometallic compound, according to the process described in international patent application WO 00/27781. It is also possible to incorporate methane into alkanes, according to the process described in international patent application WO 01/0477. It has been noted that the catalytic activity of these reactions

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 of approval decreased gradually over time, presumably by an aging effect of the catalysts used.

 US Pat. No. 5,414,176 describes a process for converting methane to higher hydrocarbons, especially C2 to C5 alkanes, in the presence of a catalyst known as a hydrogenolysis catalyst and comprising, in particular, a transition metal dispersed on a diene-based support. refractory oxide. The process is based on a basic cycle of operations that are repeated continuously and regularly with an extremely short cycle time ranging from 12 to 480 seconds.

The elementary cycle comprises successive contacting of the catalyst with a stream of methane and then a stream of hydrogen. The contacting of the catalyst with these two streams makes it possible to carry out the adsorption and the conversion of the methane, and then the desorption of the products obtained. It is specified that all the alkanes which are thus produced are adsorbed as olefins, and that the hydrogen stream makes it possible to convert the olefins to alkanes. Thus, the hydrogen used in this process acts as a reagent in the manufacture of higher hydrocarbons. It is not mentioned that this process meets a need for activation of the catalyst which would progressively undergo aging over time.

 It has now been found an improved alkane manufacturing process and especially more efficient. It makes it possible to use metal catalysts more efficiently, in particular able to perform carbon-carbon bond scission and recombination reactions and possibly carbon-metal and carbon-hydrogen bonds, in particular metathesis and cross-metathesis catalysts. and / or methane-olysis of one or more alkanes. This process makes it possible to reduce or slow the aging of these catalysts during the manufacture of alkanes, or in particular to regenerate or activate these catalysts, or in particular to maintain the activity of these catalysts in metathesis and metathesis reactions. cross-talk and / or methane-olysis of alkanes, at levels especially higher than those normally expected in such reactions in the absence of any treatment of these catalysts.

 The subject of the invention is a process for the manufacture of alkanes comprising contacting at least one initial alkane with a metal catalyst containing

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 at least one metal, Me, bonded to at least one hydrogen atom and / or at least one hydrocarbon radical, characterized in that during the production of alkanes, the catalyst is brought into contact with hydrogen.

 The subject of the invention is also a process for activating a metal catalyst intended to manufacture alkanes and containing at least one metal, Me, bonded to at least one hydrogen atom and / or at least one hydrocarbon radical, characterized in that during the production of alkanes by contacting the catalyst with at least one initial alkane, the catalyst is contacted with hydrogen.

 By activation of a catalyst, it is also generally possible to understand, according to the present invention, catalyst regeneration, or maintenance of catalyst activity in metathesis, cross-metathesis and / or methanolysis reactions. alkanes at levels higher than expected in such reactions in the absence of any catalyst treatment.

 In the process according to the present invention, hydrogen may optionally be used together with an in situ hydrogen forming agent, as described later.

 FIG. 1 is a schematic representation of a device making it possible to implement the process according to the invention in which the production of alkanes and the activation of the catalyst by hydrogen take place simultaneously and preferably continuously in a single zone.

 Figure 2 is a schematic representation of an improved device compared to that illustrated in Figure 1, for implementing the method according to the invention and including a single zone in the gas phase.

 FIG. 3 is a schematic representation of a device making it possible to implement the process according to the invention in which the production of alkanes and the activation of the catalyst by hydrogen take place simultaneously and preferably continuously in two separate areas.

 FIG. 4 is a schematic representation of an improved device compared to that illustrated in FIG. 3, making it possible to implement the method according to

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 the invention in which the manufacture of alkanes and the activation of the catalyst are carried out in two distinct gaseous phases.

According to the present invention, the manufacture of alkanes comprises contacting at least one initial alkane with a catalyst. The initial alkane (s) may be chosen from linear alkanes and branched alkanes, for example from linear C2 to C80 alkanes, preferably from C2 to C30, in particular from C2 to C20, in particular from C2 to C17, from linear alkanes of C18 to C80, preferably C21 to C80, especially C31 to C80, from branched C4 to C80 alkanes, preferably C4 to C30, especially C4 to C20, in particular C4 to C17, and from branched alkanes of C18 to C80, preferably C21 to C80, especially C31 to C80. The linear or branched C18 to C80 alkanes, preferably C21 to C80, especially C31 to C80, generally constitute the so-called waxes, in particular petroleum waxes, such as linear or branched paraffin waxes ( or linear or branched macrocrystalline waxes) or linear or branched microcrystalline waxes, and synthetic waxes, such as Fisher-Tropsch waxes and polyolefin waxes, for example polyethylene waxes, polypropylene waxes, poly waxes alpha-olefin and heavy poly-alpha-olefin waxes. The linear or branched alkanes generally correspond to the general formula
CnH2n + (1) wherein n is a number ranging from 2 to 80, preferably from 2 to 30, especially from 2 to 20, in particular from 2 to 17, or from 18 to 80, preferably from 21 to 80, in particular from 31 to 80, or from 4 to 80, preferably from 4 to 30, especially from 4 to 20, in particular from 4 to 17.

 The initial alkane or alkanes may also be chosen from cycloalkanes substituted with at least one linear or branched alkane chain, for example from said substituted C4 to C80, preferably C4 to C60, cyanoalkanes, or from said substituted C4 to C30 cycloalkanes. preferably from C4 to C20, in particular from C4 to C14, and from said substituted C5 to C80 cycloalkanes, preferably from C21 to C80, especially from C31 to C80. By cycloalkanes is generally meant cycloparaffins or cyclanic hydrocarbons, or cyclic alkanes, especially

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mono-, or bi- or poly-cyclic alkanes. Among the substituted cycloalkanes, it is especially possible to use those having at least one linear or branched alkane chain having from 1 to 12, preferably from 1 to 6 carbon atoms. The substituted cycloalkanes and in particular the substituted monocyclic alkanes may correspond to the general formula
CmH2m (2) in which m is a number ranging from 4 to 80, preferably from 4 to 60, in particular from 4 to 30, in particular from 4 to 20 or from 4 to 17, or from 18 to 80, preferably from 21 to 80, especially from 31 to 80.

dans laquelle x est un nombre égal ou supérieur à 2, de préférence allant de 2 à 20, et y est un nombre égal ou supérieur à 0, de préférence allant de 0 à 58, notamment de 0 à 28. The substituted cycloalkanes and in particular the substituted monocyclic alkanes may also correspond to the general formula

wherein x is a number equal to or greater than 2, preferably from 2 to 20, and y is a number equal to or greater than 0, preferably from 0 to 58, especially from 0 to 28.

 Among the substituted cycloalkanes, it is possible to use methylcycohexane, ethylcycohexane, n-propylcyclohexane, isopropylcyclohexane, n-butylcyclohexane and isobutylcyclohexane, as well as derivatives of decahydronaphthalene substituted with at least one linear or branched alkane chain, said chain which may have from 1 to 12, preferably from 1 to 6 carbon atoms.

 The initial alkane (s) may also be selected from methane and mixtures of methane with at least one of the other initial alkanes mentioned above, in particular one or more other alkanes selected from linear alkanes, branched alkanes or substituted cycloalkanes. , such as those mentioned above.

 The initial alkane (s) may be, preferably, selected from ethane, propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, isohexane, methyl- 2-pentane, methyl-3-pentane, dimethyl-2,3-butane, nheptane, isoheptane, n-octane and isooctane, and methane and mixtures of methane with less initial alkanes mentioned above.

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 The initial alkane or alkanes may preferably be chosen from liquefied petroleum gases or LPG (mixtures of propane and butanes, known by the term: liquefied petroleum gas or LPG), natural gas (a mixture containing essentially methane), wet gas or wet natural gas (a mixture of methane and higher homologues of methane, such as C2 to C5 or C3 to C4 alkanes, especially a mixture of methane and propane, known under the term wet gas or wet natural gas), natural gas liquids or NGLs (mixtures of ethane, propane, butanes, pentanes, natural gasoline and condensates, known as natural- gas liquids or NGL), and the synthesis crude (a mixture of C5 and higher alkanes, in particular a mixture of C5 alkanes, known as syncrude).

 In a variant of the process according to the invention, the production of alkanes which results from the bringing into contact of at least one initial alkane with the catalyst can be carried out by subjecting, as principal step, the alkane (s). initial, such as linear or branched alkanes or substituted cycloalkanes mentioned above, to a metathesis reaction of carbon-carbon bonds, in the presence of the catalyst and optionally at least one other initial alkane, in particular according to the process described in International Patent Application WO 98/02244. In particular, it may be to react the linear or branched alkane or the substituted cycloalkane by metathesis reaction on itself to obtain the higher and lower homologous alkanes. It may also be to react between them at least two different initial alkanes and selected from linear or branched alkanes or substituted cycloalkanes, so as to obtain the higher and lower homologous alkanes resulting from metathesis reactions of carbon-carbon bonds . In this case, the metathesis reaction is carried out with a mixture of at least two different initial alkanes. In the metathesis reactions of one or more initial alkanes, it is preferred to use a catalyst containing at least one metal, Me, bonded in particular to at least one hydrogen atom. The metathesis reaction can be carried out at a temperature ranging from 25 to 300 ° C., preferably from 100 ° to 200 ° C., and in particular under an absolute pressure ranging from 10 3 to 10 MPa. It is preferably carried out continuously.

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 In another variant of the process according to the invention, the production of alkanes can be carried out by subjecting, as main step, the initial alkane (s), such as the linear or branched alkanes or the substituted cycloalkanes mentioned above, to a cross-metathesis reaction comprising contacting the initial alkane (s) with the catalyst containing at least one metal, Me, linked to at least one hydrocarbon radical, in particular to obtain at least one final alkane, higher or lower homolog of the initial alkane. The cross-metathesis reaction can be carried out according to the process described in international patent application WO 00/27781. Generally, the cross metathesis reaction is obtained in particular by cleavage of the hydrocarbon radical of the catalyst and recombination of said radical with at least one other radical resulting from a cleavage of the initial alkane. The cross metathesis reaction can be carried out at a temperature ranging from 20 to 400 ° C., preferably from 100 ° to 300 ° C., and in particular under an absolute pressure ranging from 10 3 to 10 MPa. It is preferably carried out continuously.

 In another variant of the process according to the invention, the production of alkanes may result, as a main step, in contacting the methane with one or more other initial alkanes, such as linear alkanes or branched or substituted cycloalkanes mentioned above, and especially having at least 3 carbon atoms with the catalyst. In this case, the initial alkanes used in the manufacture of alkanes consist of methane and at least one of the other initial alkanes such as those described above. The contacting can be carried out, in particular, by using a mixture of methane with at least one of the other initial alkanes, such as those described above and in particular alkanes C2 to C6, or C2 to C5 or C2 to C4, or C3 to C6, or C3 to C5, or C3 to C4, or C4 to C6, or C4 to C5, or C5 to C6, or C5, for example a a mixture such as natural gas, wet gas or wet natural gas, or a mixture of natural gas with LPG, LNG or synthetic crude. The contacting can then comprise contacting this mixture with the catalyst. The contacting can be carried out so as to form at least one final alkane having a number of carbon atoms equal to or greater than 2, in particular according to the method described in the patent application.

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 International patent WO 01/0477. The reaction which results, according to this method, from bringing methane into contact with at least one other initial alkane and incorporating methane into the other initial alkane is generally referred to as a methaneolysis reaction. The contacting may be carried out at a temperature ranging from -30 to +400 ° C., preferably from 0 ° to 300 ° C., in particular from 20 ° C. to 200 ° C., and in particular under an absolute pressure ranging from 10 -3 to 30 MPa, preferably from 10-1 to 20 MPa, in particular from 10-1 to 10 MPa. The production of alkanes resulting from the methane-olysis reaction is particularly advantageous when the bringing into contact is carried out under a methane partial pressure equal to or greater than 0.1 MPa, preferably chosen in a range from 0.1 to 100 MPa, especially 0.1 to 50 MPa, in particular 0.1 to 30 MPa or 0.2 to 20 MPa. A catalyst capable of catalyzing a cleavage reaction and / or carbon-carbon bond recombination and / or carbon-hydrogen bonding and / or carbon-metal bonding may be used. The production of alkanes is preferably carried out continuously.

 In another variant of the process according to the invention, the production of alkanes may result, as a main step, in bringing the methane into contact with the catalyst, preferably containing at least one metal, Me, chosen from transition metals, lanthanides and actinides. In this case, the initial alkane is constituted by methane. From this contact, it follows that the methane reacts essentially with itself by a coupling reaction of methane. The contacting is preferably carried out so as to form ethane, with in particular an ethane selectivity of at least 65% by weight relative to the carbonaceous products formed during the manufacture of alkanes. It may be carried out at a temperature ranging from -30 to +800 ° C., preferably from 0 ° to 600 ° C., in particular from 20 ° to 500 ° C. and in particular from 50 ° to less than 450 ° C., for example from 50 ° to 400 ° C. or 50 to 350 ° C., and in particular under an absolute total pressure ranging from 10 3 to 100 MPa, preferably from 0.1 to 50 MPa, in particular from 0.1 to 30 MPa or from 0.1 to 20 MPa, in particular from 0.1 to 10 MPa. It is preferably carried out continuously.

 The manufacture of alkanes as described in one of the preceding embodiments may be carried out in the presence of one or more inert agents, in particular

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 liquid or gaseous, especially in the presence of one or more inert gases such as nitrogen, helium or argon. It can also be carried out batchwise or, preferably, continuously.

 The Periodic Table of Elements listed below is the one proposed by IUPAC in 1991 and found, for example, in David R's CRC Handbook of Chemistry and Physics, 76th Edition (1995-1996). Lide, published by CRC Press, Inc. (USA).

 According to the present invention, the catalyst is contacted with hydrogen during the manufacture of alkanes. In particular, it has been observed that such contacting has the effect of slowing down or reducing the aging of the catalyst over time, and consequently of maintaining the activity of the catalyst during the manufacture of alkanes at levels higher than those expected in the absence of any catalyst treatment.

 The contacting of the catalyst with the hydrogen can be carried out in various ways. It can be, first of all, carried out by adding hydrogen to the catalyst and optionally by in situ formation of hydrogen, especially in the presence of the catalyst. In particular, the in situ formation of hydrogen can be carried out using an in situ hydrogen forming agent. The agent may preferably be chosen from agents capable of releasing hydrogen, in particular by a physical action such as desorption, and from agents capable of forming (or producing) by chemical reaction of the hydrogen, especially in the presence of the catalyst. In situ formation of hydrogen can be achieved by contacting the agent with the catalyst. In practice, the contacting of the catalyst with hydrogen and optionally with the agent can be carried out by adding hydrogen and optionally the agent to the catalyst, or the opposite, that is to say by addition from the catalyst to hydrogen and optionally to the agent, or else by simultaneous additions of the catalyst, hydrogen and optionally the agent.

 Among the in situ forming agents of hydrogen, it is possible to use agents capable of releasing hydrogen, in particular by a physical action such as desorption. These agents may be solids containing in particular

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 the hydrogen absorbed or adsorbed in them. They can be chosen from metals and alloys of metals capable of reversibly accumulating hydrogen (and thus in particular to restore at least a portion of the accumulated hydrogen), preferably from metal hydrides and particularly from hydrides of metal alloys, especially in bulk form (in particular in non-supported or non-dispersed form on a solid support). The metals involved in particular in the metal hydrides and in particular in the hydrides of metal alloys can be chosen from lanthanides, actinides and metals of Groups 2 to 12, preferably 2 to 11 of the Table of the Periodic Table of Elements, in particular the transition metals of groups 3 to 11, preferably 3 to 10, especially 3 to 6 of said Table. More particularly, the metal hydrides may be chosen from binary hydrides, in particular from lanthanide hydrides, actinide hydrides and transition metal hydrides, such as titanium hydrides or lanthanum hydrides. The metal hydrides may also be chosen from hydrides known as intermetallic hydrides or metal alloys, in particular hydrides of transition metal alloys of Groups 3 to 11 with possibly other metals from Groups 2, 12 and 13 of the Table. of the Periodic Table of Elements, such as iron / titanium or lanthanum / nickel hydrides. The in situ formation of hydrogen can thus be carried out by subjecting one of these agents capable of releasing hydrogen at a temperature and / or a pressure such that the agent releases hydrogen, in particular in the presence of hydrogen. catalyst.

 Among the in situ forming agents of hydrogen, it is also possible to use agents or reagents capable of forming hydrogen by chemical reaction, in particular by a spontaneous chemical reaction in the presence of the catalyst. One of these preferred agents is methane, especially when used in the presence of the catalyst.

In particular, it has been observed that the methane put in contact with the catalyst can form in situ hydrogen and ethane, by a coupling reaction, preferably non-oxidizing methane.

 The quantity of hydrogen and optionally in situ forming agent of hydrogen, such as methane, used with the catalyst is chosen from

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 so that it is sufficient to activate the catalyst, or in particular to reduce or slow down the loss of catalyst activity during the manufacture of alkanes, or more particularly to maintain the activity of the catalyst in the manufacture of alkanes at a higher level than expected in the absence of any catalyst treatment. The contacting can be carried out under a hydrogen partial pressure ranging from 10-3 to 102 MPa, preferably from 0.1 to 50 MPa. When hydrogen is used in the presence of the initial alkane (s), the amount of hydrogen may be such that the molar ratio of hydrogen to the initial alkane (s) is 10-6 / 1 to 10-1 / 1, especially from 10-5 / 1 to 10-2 / 1. The possible amount of in situ forming agent of hydrogen or in particular of methane, used in addition to hydrogen, may be such that the molar ratio between the agent or the methane and the other alkane or initial alkanes is 10 -1/1 to 106/1, preferably from 102/1 to 10511, in particular from more than 5.102 / 1 to 5.104 / 1, in particular from 103/1 to 104/1.

 The placing in contact (or activation) of the catalyst with hydrogen may be carried out at a temperature ranging from -30 to 800 ° C., preferably from 0 ° to 600 ° C., in particular from 20 ° to 500 ° C., in particular 20 to 400 ° C. C. The absolute total pressure upon contacting may be from 10-3 to 102 MPa, preferably from 0.1 to 50 MPa. The duration of the contacting depends in particular on the temperature and the hydrogen pressure exerted during this contacting, and possibly on the nature of the in situ hydrogen forming agent. The duration of the contacting may be at least 1 minute, preferably at least 10 minutes, especially at least 30 minutes and may be up to 72 hours, preferably up to 48 hours, and in particular may be at most equal to the duration of the manufacture of alkanes, in particular when this bringing into contact is carried out in the presence of the initial alkane (s). This contacting can on average last in the times mentioned above, when it is carried out continuously.

 The placing in contact (or activation) of the catalyst with hydrogen (and optionally with the in situ forming agent of hydrogen) can be carried out in the presence or in the absence of the initial alkane or alkanes, particularly involved in the manufacture of alkanes. By alkane (s) (or initial) is meant in particular the methane and / or the initial alkane or alkanes, such as linear or branched alkanes or

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 cycloalkanes previously described and engaged in particular in the manufacture of alkanes according to the invention. The placing in contact (or activation) of the catalyst with the hydrogen (and optionally with the agent) may also be carried out batchwise or preferably continuously. It can also be carried out in the presence of one or more inert agents, in particular liquid or gaseous, in particular of one or more inert gases such as nitrogen, helium or argon.

 The placing in contact (or activation) of the catalyst with the hydrogen (and optionally the agent) can advantageously be carried out in the presence of or initial alkanes, engaged in particular in the manufacture of alkanes. This means that the catalyst is contacted simultaneously with the hydrogen (and optionally the agent) and with the initial alkane (s). This also means that the catalyst is brought into contact so that the production of alkanes and the activation of the catalyst by hydrogen (and optionally the agent) are carried out together and simultaneously, and that the setting zone in contact (or activation) of the catalyst with hydrogen (and optionally the agent) corresponds to or merges with the reaction zone of the manufacture of alkanes. In practice, the process of the invention may comprise the additions of or initial alkanes and hydrogen (and optionally the agent) to the catalyst. These additions may preferably be carried out simultaneously and / or continuously.

 When in a discontinuous production of alkanes, the bringing into contact (or activation) of the catalyst with hydrogen (and optionally with the in situ forming agent of hydrogen) is carried out in the presence of the initial alkane (s), it can then be carried out discontinuously. In this case, the production of alkanes and the activation of the catalyst are carried out together and simultaneously and discontinuously in the same zone. It is also possible, conversely, to continuously carry out the contact (or activation) of the catalyst with the hydrogen (and optionally the agent). In the latter case, discontinuous or sequential additions of or initial alkanes to the catalyst can be achieved while hydrogen (and optionally the agent) is continuously added to said catalyst.

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 However, it is preferred to make the alkanes continuously. Thus, when in a continuous production of alkanes, the bringing into contact (or activation) of the catalyst with hydrogen (and optionally the in situ forming agent of hydrogen) is carried out in the presence of or initial alkanes it can then be carried out continuously.

In practice, in this case, it is possible to carry out continuous and simultaneous additions of or initial alkanes and hydrogen (and possibly the agent) to the catalyst. Conversely, when in a continuous manufacture of alkanes, the bringing into contact (or activation) of the catalyst with hydrogen (and optionally the agent) is carried out in the presence of or initial alkanes, it can be then carried out discontinuously. In practice, in the latter case, discontinuous or sequential additions of hydrogen (and optionally of the agent) can be made to the catalyst, while at the same time the initial alkane (s) are continuously added thereto. Such discontinuous or sequential additions can be carried out regularly over time, or in such a way that the activity of the catalyst during the continuous manufacture of alkanes is maintained at a predetermined level and in particular greater than that expected in the absence any catalyst treatment.

 Alternatively, in the absence of or from the initial alkanes, it is possible to bring the catalyst into contact with the hydrogen (and optionally the in situ hydrogen forming agent). This means that the catalyst contacted with the initial alkane (s) in the production of alkanes is separated from the alkanes, in particular from the unreacted initial alkanes and the alkanes produced, before it is brought into contact with the alkane. hydrogen (and possibly with the agent). The zone of contacting (or activation) of the catalyst with hydrogen (and optionally the agent) may be identical or, more generally, different from the reaction zone where the alkanes are manufactured. If, however, the zone is identical, it means that the same zone can work alternately to make alkanes and activate the catalyst. It is also possible alternatively to use at least two separate zones containing the catalyst and operating in parallel and alternately and time-shifted between the production of alkanes and activation of the catalyst. Thus, for example, in the case where each zone operates in parallel and alternatively in the manufacture of alkanes and

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 in catalyst activation, by contacting the catalyst respectively with the initial alkane (s) and with hydrogen (and optionally with the agent), the first zone can operate in the manufacture of alkanes while simultaneously the second zone operates in activation of the catalyst, then vice versa when each zone alternates between manufacture and activation. Such a method is particularly advantageous when it is carried out continuously.

 When in a discontinuous production process of alkanes, the bringing into contact (or activation) of the catalyst with hydrogen (and optionally the in situ forming agent of hydrogen) is carried out in the absence of or initial alkanes, it can be carried out both discontinuously and continuously. In the case of discontinuous contact (or activation) of the catalyst with hydrogen (and optionally with the agent), the process may comprise the following successive steps, in particular carried out in a repetitive manner: a) recovering the catalyst contacted with the initial alkane (s) at the end of a discontinuous production of alkanes, (b) separating the catalyst thus recovered from the alkanes and in particular from the initial alkanes which have not reacted and alkanes produced, (c) contacting or activating the catalyst thus separated with the hydrogen (and optionally the in situ hydrogen forming agent), (d) optionally separating the catalyst (s) activated, at the end of the discontinuous contacting or activation, and (e) bringing the catalyst back into contact with the initial alkane (s) in another discontinuous production of alkanes.

 Conversely, when in a discontinuous production process of alkanes, the contacting (or activation) of the catalyst with hydrogen (and optionally the in situ hydrogen forming agent) is carried out in the following manner: absence of or initial alkanes, it can then be carried out continuously. In this case, the process may comprise the following successive steps, carried out in particular in a repetitive manner: (a) recovering the catalyst put in contact with the initial alkane or alkanes at the end of a discontinuous production of alkanes, (b ) separating the catalyst thus recovered, alkanes and in particular the unreacted initial alkanes and alkanes produced, (c) adding and mixing the thus separated catalyst to a part of the catalyst in contact (or

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 activated) continuously with hydrogen (and optionally the in situ forming agent of hydrogen), in particular to activate the catalyst, (d) take and recover a portion of the catalyst thus brought into contact (or activated) with continuously, (e) optionally separating the portion of the catalyst thus collected and recovered, hydrogen (and optionally the in situ hydrogen forming agent), and (f) contacting the portion of the catalyst with the or the initial alkanes in another batch production of alkanes.

 It is generally preferred to make the alkanes continuously. Thus, when in a process for the continuous production of alkanes, the bringing into contact (or activation) of the catalyst with hydrogen (and optionally the in situ forming agent of hydrogen) is carried out in the absence of or initial alkanes, it may be carried out batchwise or, preferably, continuously. In the case of discontinuous contact (or activation) of the catalyst with hydrogen (and optionally with the agent), the process may comprise the following successive stages, carried out in particular in a repetitive manner: recovering a portion of the catalyst contacted with the initial alkane or alkanes in a continuous production of alkanes, (b) separating the portion of the catalyst thus collected and recovered, alkanes and in particular or initial alkanes that have not reacted and alkanes produced, (c) contacting (or activating), in a discontinuous manner, the portion of the catalyst thus separated with hydrogen (and optionally the in situ forming agent of hydrogen), (d) optionally separating from this or these the portion of the catalyst thus contacted or activated, at the end of discontinuous contact (or activation), and (e) bringing the portion of the catalyst back into contact with the initial alkane (s) in the process. continuous operation of alkanes.

 Conversely, when in a process for the continuous production of alkanes, the contacting (or activation) of the catalyst with hydrogen (and optionally with the in situ forming agent for hydrogen) is carried out in the absence of the initial alkane (s), it can then be carried out continuously. In this case, the process may comprise the following successive steps, carried out in particular in a repetitive manner: (a) taking and recovering a portion of the catalyst put in contact with the alkane (s)

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 initial steps in a continuous manufacture of alkanes, (b) separating the portion of the catalyst so withdrawn and recovered, alkanes and in particular the initial or unreacted alkanes and alkanes produced, (c) adding and mixing the portion of the catalyst thus separated at a portion of the catalyst in contact (or activated) continuously with hydrogen (and optionally the in situ forming agent of hydrogen), in particular to activate the catalyst, (d) take and recover a portion of the catalyst thus brought into contact (or activated) continuously, (e) optionally separating the portion of the catalyst thus collected and recovered, hydrogen (and optionally the in situ forming agent of hydrogen), and f) contacting the portion of the catalyst with the initial alkane (s) in the continuous production of alkanes.

 The practice of the present invention can be carried out in a variety of ways and is highly dependent on how the catalyst is brought into contact with the hydrogen (and optionally with the agent), especially if it is carried out in the presence or in the absence of the initial alkane or alkanes, in particular involved in the manufacture of alkanes.

 More particularly, when the bringing into contact (or activation) of the catalyst with hydrogen (and optionally with the in situ forming agent of hydrogen) is carried out in the absence of or initial alkanes, engaged in particular in the manufacture of alkanes, it is then performed separately from contacting the catalyst with the initial alkane or alkanes. In this case, the two catalyst contacts can be carried out in at least two distinct zones: in particular a reaction zone where the manufacture of alkanes is carried out, in particular by contacting the catalyst essentially with the initial alkane (s). and an activation zone where in particular the catalyst is brought into contact essentially with hydrogen (and optionally with the agent). These two distinct zones may be interconnected by one or more transfer zones, capable in particular of transferring at least a portion of the catalyst from one zone to the other.

 Thus, the production of alkanes and the activation of the catalyst can effectively be carried out separately in two distinct zones, and the process according to the invention can then be carried out batchwise or, preferably, continuously. By

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 elsewhere, the two distinct zones may in particular be connected to each other by a first catalyst transfer zone connecting the zone of contacting (or activation) of the catalyst with hydrogen (and optionally with the agent) at the reaction zone for producing alkanes, and by a second catalyst transfer zone connecting the alkane production reaction zone to the zone of contacting (or activation) of the catalyst with hydrogen (and optionally with 'agent). One of the two transfer zones or preferably the two transfer zones can be implemented batchwise or preferably continuously, especially when the two separate areas of the process are themselves implemented continuously. At least one of the two transfer zones may comprise a pipe or an elevator chosen in particular from mechanical hydraulic pipes and risers (with the aid of a non-aqueous liquid, in particular a hydrocarbon liquid, such as an alkane). ) or preferably tires. The transfer of the catalyst in a pipe or elevator, hydraulic or preferably pneumatic, can be achieved by means of a carrier fluid, in particular a carrier liquid or preferably a carrier gas, chosen in particular from at least one of the liquid constituents or gas present in the area where the transfer is directed. Such a method has the advantage of facilitating the transfer of the catalyst and improving the reliability and regularity of the process. At least one of the two transfer zones may be preceded by a zone separating partially or totally the catalyst from the other liquid or gaseous constituents, entrained with the catalyst outside the zone from which the catalyst originates. The other component (s) thus entrained and separated from the catalyst are preferably returned to the zone from which the catalyst originates. This method has the advantage of being able to independently produce the production of alkanes and the activation of the catalyst, without notably creating disturbances in one or the other of the two zones. It also makes it possible to increase the yield of the process.

 It is also possible to use the two distinct alkane production and catalyst activation zones according to other variants, especially when they are interconnected by two transfer zones such as those described above. Thus according to a variant, it is possible to realize in a first zone the

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 manufacture of alkanes in the absence of hydrogen (and of in situ hydrogen forming agent, such as methane), in particular by bringing the catalyst into contact with one or more initial alkanes containing in particular at least two atoms while in a second distinct zone, the catalyst is brought into contact (or activated) with hydrogen (and optionally with the agent, such as methane) in the presence, if any, of one or more initial alkanes, identical or different from those used in the first zone and containing in particular at least one carbon atom, and that simultaneously at least a portion of the catalyst is transferred from one zone to the other. According to another variant, in a first zone it is possible to carry out, in the absence of alkane, contacting (or activation) of the catalyst with hydrogen (and optionally with the agent forming in situ hydrogen, chosen in particular other than methane), while in a second distinct zone, the manufacture of alkanes in the presence of hydrogen (and optionally of the agent, such as methane) is carried out by contacting the catalyst with a catalyst. or several initial alkanes containing in particular at least one carbon atom, and simultaneously at least a portion of the catalyst is transferred from one zone to the other. One or the other of these variants can advantageously be carried out continuously.

 The two distinct areas of the process can be implemented in a variety of ways. In particular, the manufacture of alkanes, carried out by bringing the catalyst into contact with the initial alkane or alkanes, can be carried out in a reaction zone in the liquid phase or in the gas phase. In the first case, the reaction zone in the liquid phase may comprise a liquid phase consisting essentially of the initial alkane (s), in particular in the liquid state under the contacting conditions, and / or with one or more liquid inert agents. The liquid phase may preferably be a liquid suspension containing solid particles, in particular essentially consisting of the catalyst in a solid form, preferably in a powder form or granules. The reaction zone in the liquid phase may comprise a reactor or a loop in the liquid phase, in particular a reactor or a loop for suspension in the liquid phase, preferably provided with one or more means chosen from stirring means, in particular for suspension, means of exchange of

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 heat, heating and / or cooling, self-cooling, condensing, circulation, recycling and separation of the products engaged and / or manufactured, in particular gaseous, liquid and solid, and insulation and recovery of manufactured products.

 The manufacture of alkanes may also be carried out in a reaction zone in the gaseous phase comprising in particular a gaseous phase consisting essentially of the initial alkane (s), in particular in the gaseous state under the conditions of contacting with the catalyst, and optionally by one or more inert gases such as nitrogen, helium or argon. In this case, the gas phase reaction zone can comprise a reactor or a gas-phase loop, chosen in particular from fluidized bed and / or mechanically stirred reactors, fixed-bed reactors and circulating-bed reactors, the bed being able to essentially consist of the catalyst, in particular in a solid form, preferably in a powder form or granules. The gas phase reactor may be provided with one or more means chosen from means for heat exchange, heating and / or cooling, condensation, stirring, circulation, recycling and separation of the engaged products. and / or manufactured, especially gaseous, solid and possibly liquid, and insulation and recovery of manufactured products.

 Thus, the production of alkanes can be carried out in a reaction zone, in particular in the liquid phase or preferably in the gas phase, as described above. In this case, the process according to the invention may comprise the following steps, carried out in particular continuously: (a) introducing the initial alkane (s) into the reaction zone, (b) bringing the initial alkane (s) into contact with the catalyst, present or introduced into said zone, (c) withdrawing from said zone a portion of the alkanes produced, bringing with them a portion of the initial alkanes or unreacted, (d) partially or completely separate the portion of alkanes produced of the portion of initial or unreacted alkanes, and (e) return preferably to said zone the part thus separated from or from the initial unreacted alkanes, which part is thus in particular brought into contact with the catalyst.

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 The placing in contact (or activation) of the catalyst with hydrogen (and optionally the in situ forming agent of hydrogen) can be carried out in an activation zone in the liquid phase or, preferably, in the gas phase. . In the case of an activation zone in the liquid phase, this may comprise a liquid phase which may consist essentially of at least one liquid inert agent. The liquid phase may preferably be a suspension containing solid particles, in particular essentially consisting of the catalyst in a solid form, preferably in a powder form or granules. The activation zone in the liquid phase may comprise a reactor or a loop in the liquid phase, in particular a reactor or a loop for suspension in the liquid phase, provided in particular with one or more means chosen from stirring means, in particular for suspension , the heating and / or cooling, self-cooling, condensing, circulation, recycling and separation means of the engaged, manufactured and / or activated products, in particular gaseous, liquid and solid, and insulation and recovery of manufactured and / or activated products.

 It is preferred to carry out the activation of the catalyst in a gas phase activation zone which may comprise a gaseous phase consisting essentially of hydrogen, optionally by the in situ forming agent of hydrogen, such as methane, and optionally with one or more inert gases such as nitrogen, helium or argon. The gas phase activation zone can comprise in particular a reactor or a gas-phase loop, chosen in particular from fluidized bed and / or mechanically stirred reactors, fixed bed reactors and circulating bed reactors, the bed being able to essentially consist of the catalyst, especially in a solid form, preferably in a powder form or granules. The gas phase reactor may be provided with one or more means chosen from means for heat exchange, heating and / or cooling, condensation, circulation, recycling and separation of the products engaged, manufactured and / or or activated, in particular gaseous, solid and possibly liquid, and isolation and recovery of products manufactured and / or activated.

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 Thus, the activation may advantageously be carried out in an activation zone in the gaseous phase, as described above, and especially continuously. In this case, the process according to the invention may comprise the following steps, preferably carried out continuously: (a) introducing the catalyst into an activation zone in the gas phase traversed by a stream of hydrogen (and possibly in situ forming agent for hydrogen, such as methane), in particular so as to bring the catalyst into contact with and activate with hydrogen, the stream preferably being recycled in said zone, and the catalyst thus introduced forming, in particular, a in particular fluidized bed and traversed by said stream, (b) withdrawing and recovering from said zone a portion of the catalyst thus activated, carrying with it a portion of the hydrogen and optionally the agent, (c) optionally partially separate or totally the portion thus withdrawn and recovered from the catalyst, from the part of the hydrogen and possibly from the agent thus entrained, withdrawn and recovered, and (d) return from ference in said zone the portion of the hydrogen and optionally the thus separated Agent, which is thus particularly recontacting with the catalyst.

 Conversely, when the placing in contact (or activation) of the catalyst with hydrogen (and optionally with the in situ forming agent of hydrogen) is carried out in the presence of or initial alkanes, engaged in particular in the production of alkanes, the contacting of the catalyst with hydrogen (and optionally with the agent) and with the alkane (s) can then be carried out in a single zone.

Thus, the manufacture of alkanes and the activation of the catalyst can be carried out together and simultaneously in a single zone, and preferably continuously. The single zone may be a liquid phase zone or, preferably, a gas phase zone.

 In the case of a single zone in the liquid phase, it may comprise a liquid phase consisting essentially of the initial alkane (s) and possibly one or more liquid inert agents. The liquid phase may preferably be a suspension containing solid particles, in particular consisting essentially of the catalyst, especially in solid form, of

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 preferably in a powder form or granules. The single zone in the liquid phase may comprise a reactor or a loop in the liquid phase, preferably a reactor or a loop for suspension in the liquid phase, as described above, and possibly provided with one or more means chosen from the means for stirring in particular for suspension, means for heat exchange, heating and / or cooling, self-cooling, condensation, circulation, recycling and separation of the products engaged, manufactured and / or activated, in particular gaseous , liquids and solids, and insulation and recovery products manufactured and / or activated.

 In the case of a single zone in the gaseous phase, this may comprise a gaseous phase consisting essentially of the initial alkane (s), hydrogen, optionally by the in situ hydrogen forming agent) and optionally by one or more inert gases, such as nitrogen, helium or argon. The single zone in the gas phase may comprise a reactor or a gas-phase loop, preferably chosen from fluidized bed and / or mechanically stirred reactors, fixed-bed reactors and circulating-bed reactors, the bed preferably consisting of essentially by the catalyst especially in a solid form, preferably in a powder form or granules. The gas phase reactor is preferably provided with one or more means chosen from heat exchange, heating and / or cooling, self-cooling, condensation, circulation, recycling and separation means. engaged, manufactured and / or activated products, especially gaseous, liquid and solid, and insulation and recovery products manufactured and / or activated.

 Thus, the process can be advantageously carried out in a single zone in the gas phase, as described above. It may comprise the following steps, preferably carried out continuously: (a) introducing the initial alkane (s), hydrogen, optionally the in situ hydrogen forming agent and optionally one or more inert gases in a single zone; a gaseous phase containing the catalyst, preferably in a solid form and capable of constituting in particular a particularly fluidized bed, so as to form a substantially gaseous stream passing through said zone, the stream preferably being recycled in said zone, (b) drawing off of

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 said zone a portion of the stream having passed through said zone and containing the alkanes produced, (c) partially or completely separating the alkanes produced from or unreacted initial alkanes, hydrogen, or optionally hydrogen, and optionally the inert gas (s), and (d) possibly return to said zone, thus separated from the alkanes produced and which are thus in particular brought into contact with the catalyst.

 FIG. 1 schematically represents a device making it possible to implement the process according to the invention in which the production of alkanes and the activation of the catalyst by hydrogen are carried out simultaneously and preferably continuously in a single zone (1) , in the liquid phase or preferably in the gas phase, containing the catalyst (2) in particular in a powder form or granules. The single zone (1) may comprise a reactor in the liquid phase, in particular a reactor for suspension in the liquid phase, as described above and equipped in particular with means for mechanical stirring and heat exchange. Preferably, the single zone (1) may comprise a gas phase reactor, in particular a fluidized bed reactor and / or mechanically stirred, or a fixed bed reactor or circulating bed, as described above, and provided in particular with means heat exchange and circulation and / or recycling products engaged and / or manufactured in the area (1). The device may comprise two feed lines (3) and (4) of the zone (1) respectively with initial (or initial) alkane (s) and with hydrogen (and optionally with in situ hydrogen forming agent). methane) which flow directly or indirectly into the zone (1), in particular via a recycling line (11). These feed lines preferably feed the zone (1) continuously. The device may optionally comprise a make-up line (5) made of fresh catalyst and a make-up line (6) of inert agent (s), which may be liquid or gaseous, in particular one or more inert gases such as than nitrogen, helium or argon. The two extra lines (5) and (6) can open into the zone (1) so as to supply, preferably continuously, this zone respectively with fresh catalyst and agent (s). The device can also comprise a line catalyst discharge (7) which exits the zone (1) so as to discharge, preferably continuously, out of the zone a portion of the catalyst,

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 especially in excess, or possibly worn or aged. A withdrawal line (8) can leave the zone (1) so as to withdraw, preferably, continuously from this zone a mixture containing at least a portion of the alkanes produced, hydrogen (and optionally in situ formation of hydrogen), or unreacted initial alkanes and optionally inert agents. The withdrawal line (8) can lead directly or indirectly into a separation zone (9) so as to partially or completely and preferably continuously remove at least one of the constituents of the mixture withdrawn, in particular the alkanes produced, in them. separating in particular hydrogen (and optionally hydrogen-forming agent), or initial alkanes and optionally inert agents. The alkanes produced and thus separated can be recovered, in particular continuously, outside the separation zone (9) by a recovery line (10) leaving this zone, while the other products separated in this zone, in particular hydrogen (and optionally the in situ forming agent for hydrogen), the initial alkane (s) and optionally the inert agent (s) may be advantageously returned at least in part and in particular continuously in zone (1) by a line of recycling (11). The separation zone (9) can comprise in particular one or more means of fractionation and / or condensation.

 FIG. 2 diagrammatically represents an improved device with respect to that illustrated in FIG. 1, making it possible to implement the method according to the invention, preferably carried out continuously and comprising in particular a single zone in the gas phase. The elements of the device according to Figure 2 which are identical to those of the device according to Figure 1, are taken with the same digital dens. The device has a single zone (1) in the gas phase which comprises a gas phase reactor (1 ') containing a bed (2') preferably fluidized and consisting essentially of the catalyst. The reactor (1 ') is provided in particular with a fluidization grid (12) and a recycle loop (13) of a substantially gaseous stream comprising the initial alkane (s), the alkanes produced, and optionally hydrogen. the in situ hydrogen forming agent, such as methane and optionally one or more inert gases such as nitrogen, helium or argon. The recycling loop (13)

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 can leave the top of the reactor (1 ') and return to the base of the latter. It may comprise a compressor (14) intended in particular to circulate, preferably continuously, the gaseous stream in the loop (13) and through the reactor (1 ') according to a particularly rising current, in order to maintain in particular the bed (2 ') in the fluidized state, and a heat exchanger (15) intended in particular for controlling and maintaining the temperature of the reactor (1'), in particular the temperature of the bed (2 '), to a predetermined value. The device may comprise two supply lines (3) and (4) of the reactor (1 ') respectively in alkane (s) (or initial) and in hydrogen and optionally in situ forming agent for hydrogen, and optionally a booster line (6) in one or more inert gases. These feed lines can lead into the recycle loop (13) of the reactor (1 ') and preferably feed the reactor (1') continuously. The reactor (1 ') can be provided with a fresh catalyst booster line (5) which can open into the reactor (1'), and a catalyst exhaust line (7), in particular in excess or possibly used or aged, which leaves the reactor (1 '). A withdrawal line (8) can leave the recycling loop (13) so as to withdraw, in particular continuously, out of the reactor (1 ') and the loop (13) a portion of the gas stream in the form of a mixture containing the product alkanes, hydrogen, the initial or unreacted alkanes, optionally the in situ hydrogen forming agent and optionally the inert gas (s). The withdrawal line (8) can lead directly or indirectly into a separation zone (9), as mentioned above, so as to partially or completely and preferably continuously remove at least one of the constituents of the mixture withdrawn, in particular the alkanes produced, in particular separating them from or from the initial alkanes, hydrogen, optionally the agent forming in situ hydrogen and optionally inert gas or gases. The alkanes produced and thus separated can be recovered, in particular continuously, out of the separation zone (9) by a recovery line (10) leaving this zone, while the other separated products can be returned at least in part and preferably continuously in the recycling loop (13) by a recycling line (11).

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 Figure 3 shows schematically a device for carrying out the method of the invention wherein the manufacture of alkanes and the activation of the catalyst with hydrogen take place simultaneously and preferably continuously in two distinct areas. The device comprises a reaction zone (1), in the liquid phase or preferably in the gas phase, containing in particular the catalyst (2), preferably in a powdered or granular form, and preferably operating continuously. The reaction zone (1) may comprise a liquid phase reactor or a gas phase reactor, as described above, and possibly equipped with means for heat exchange, agitation, circulation or recycling of the products engaged and / or manufactured in zone (1), such as those described above. The device may comprise a feed line (3) of the zone (1) of initial (or initial) alkane (s) and possibly a make-up line (6) of gaseous liquid agent (s), in particular inert gas (s), such as nitrogen, helium or argon.

The supply lines (3) and auxiliary lines (6) can lead directly or indirectly into the zone (1), for example via a recycling line (11), and can feed preferably continuously zone (1) or to make up this zone with these constituents. The device may further comprise a withdrawal line (8) which can leave the zone (1), so as to withdraw, in particular continuously, from the zone (1) a mixture containing a part of or alkanes produced, or unreacted initial alkanes and optionally inert agents. The withdrawal line (8) can lead directly or indirectly into a separation zone (9) including separation means such as those mentioned above. The separation zone (9) can operate in such a manner as to partially or completely and preferably continuously remove at least one of the constituents of the mixture withdrawn, in particular the alkanes produced, by separating them in particular from or from the initial alkanes and optionally from or inert agents. The alkanes produced and thus separated can be recovered, in particular continuously, outside the separation zone (9) by a recovery line (10) leaving this zone, while the other products separated in this zone, in particular the one or more initial alkanes which have not reacted and optionally the inert agent (s) may be returned at least

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 part and preferably continuously, directly or indirectly, in the area (1) by a recycling line (11).

 From the reaction zone (1) a discharge line (16) can be discharged from a mixture containing at least a part of the catalyst, preferably in a powder form or granules, with which part of the alkanes produced, from which initial unreacted alkanes and optionally inert agents. The evacuation line (16) may be a mechanical or pneumatic transport line, or in particular a mechanical or pneumatic lift. The pipe or the elevator are in particular intended to transport from one point to another the catalyst in the form of particles. The evacuation line (16) can preferably operate continuously and open into a separation zone (17) of the catalyst. The separation zone (17) can be in particular a phase separator, such as a solid / liquid, solid or liquid / solid / liquid / gas separator, a cyclone separator or a settling separator. The separation zone (17) can operate in such a way as to partially or totally and preferably continuously separate the catalyst from at least one of the constituents of the mixture discharged through the evacuation line (16), in particular the alkanes produced the initial alkane (s) unreacted and optionally the inert agent (s). From the separation zone (17) a transfer line (18) of the thus separated catalyst and a return line (19) of the other separated product (s) can be withdrawn. The return line (19) can preferably operate continuously and directly or indirectly lead into the reaction zone (1), in particular via the feed line (3). The transfer line (18) may be a mechanical, hydraulic or pneumatic transport line, or in particular a mechanical, hydraulic or pneumatic lift, and may preferably operate continuously.

 The transfer line (18) can communicate with an activation zone (20) of the catalyst, in particular an activation zone in the liquid phase or preferably in the gas phase, preferably operating continuously. The activation zone (20) may comprise a reactor in the liquid phase or preferably in the gas phase, as described above, optionally provided with means for heat exchange, agitation, circulation or recycling of the products involved and / or made in

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 this area, such as the means mentioned above. A hydrogen feed line (4) (and optionally an in situ hydrogen forming agent, such as methane) may open into the activation zone (20) and preferably feed the zone (20) continuously. . A back-up line (6 ') of agent (s) can optionally lead directly or indirectly into the activation zone (20), for example via the feed line (4), and can operate in continued. The inert agent (s) supplying the activation zone (20) may be identical to or different from those introduced into the reaction zone (1).

 From the activation zone (20) may optionally exit a recovery line (21) of a mixture containing in particular at least one alkane, such as ethane and / or its higher homologues, resulting from the activation reaction of the catalyst by the optional agent forming in situ hydrogen, such as methane. The recovery line (21) may preferably operate continuously and open into a separation zone (22), in particular separation by fractionation, condensation or decantation. The separation zone (22) is operable to separate and recover, preferably continuously, the alkane (s) from the mixture, particularly ethane and / or its higher homologues, and to return it via a line (23) directly or indirectly and preferably continuously in the reaction zone (1), for example via the feed line (3). The other product or products separated in the separation zone (22), such as hydrogen and optionally the in situ forming agent of hydrogen, can be advantageously returned at least in part and preferably continuously, directly or indirectly. by a line (24) in the activation zone (20), for example via the feed line (4), the other part being discharged to the outside by a line (25). From the activation zone (20) may exit a withdrawal line (26) a mixture containing at least a portion of the activated catalyst, hydrogen, optionally the in situ hydrogen forming agent and optionally of or inert agents. The withdrawal line (26) may be a mechanical or pneumatic transport line, or in particular a mechanical or pneumatic lift, and may in particular operate continuously.

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 The withdrawal line (26) can open into a separation zone (27), which can be a phase separator, such as a solid / liquid, solid or liquid / solid / liquid / gas separator, in particular a separator. cyclone or separator by settling. The separation zone (27) can operate in such a manner as to partially or completely and preferably continuously separate the activated catalyst from the mixture withdrawn from the activation zone (20), and to return the activated catalyst in particular continuously and thus separated, in the reaction zone (1) through a recycling line (28) which can be a mechanical, hydraulic or pneumatic transport line, or in particular a mechanical, hydraulic or pneumatic lift. From the separation zone (27) there may be a return line (29) of the one or more separate products which can be returned directly or indirectly and preferably continuously in the activation zone (20), for example by the intermediate of the feed line (4). The reaction zone (1) can optionally be provided with a fresh catalyst booster line (5) which can flow directly or indirectly into the zone (1), in particular via the recycling line (28), and a catalyst evacuation line (7), in particular excess or possibly spent or aged, which can leave the reaction zone (1).

 A device as illustrated in FIG. 3 has the advantage of implementing an alkane production zone (1) and a catalyst activation zone (20) which can operate simultaneously with a high efficiency and independently of one another, in particular without the liquid or gaseous phase of one of the zones being disturbed or contaminated by that of the other.

 FIG. 4 diagrammatically represents an improved device compared to that illustrated in FIG. 3, making it possible to implement the method according to the invention, preferably carried out continuously and comprising in particular two distinct zones in the gas phase, intended for one to manufacture alkanes and the other to activate the catalyst, operating in particular independently of one another. The elements of the device according to Figure 4 which are identical to those of the device according to Figure 3, are taken with the same digital dens. The device has a gas phase reaction zone (1) which may comprise a reactor in phase

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 gaseous (1 ') preferably operating continuously and containing a bed preferably fluidized and consisting essentially of the catalyst (2). The reactor (1 ') is provided in particular with a fluidization grid (12) and a recycling loop (13) of a substantially gaseous stream comprising the initial alkane (s), the alkanes produced and optionally one or more gases. inerts, such as nitrogen, helium or argon. The recycling loop (13) can leave the top of the reactor (1 ') and return to the base of the latter. It may comprise a compressor (14) intended in particular to circulate, in particular continuously, the gaseous stream in the loop (13) and through the reactor (1 ') in a particularly upward flow in order to maintain in particular the bed to the fluidized state, and a heat exchanger (15) intended in particular for controlling and maintaining the temperature of the reactor, in particular the temperature of the bed, at a predetermined value. The device may comprise a feed line (3) of the reactor (1 ') alkane (s) (or initial) and optionally a feed line (6) of the reactor (1') in one or more inert gases. These supply lines can in particular operate continuously and lead into the recycling loop (13) of the reactor (1 '). The reactor (1 ') can be provided with a fresh catalyst booster line (5) which can lead directly or indirectly into the reactor (1'), and a metallic catalyst evacuation line (7). , in particular in excess or possibly used or aged, which can leave the reactor (1 '). A withdrawal line (8) can leave the recycling loop (13) so as to extract a portion of the gaseous stream in the form of a gas stream from the reactor (1 ') and the loop (13), in particular continuously. mixture containing the alkanes produced, the initial alkane (s) unreacted and optionally the inert gas (s). The withdrawal line (8) can lead directly or indirectly into a separation zone (9) as mentioned above, so as to partially or completely and preferably continuously remove at least one of the constituents of the mixture withdrawn, in particular the alkanes produced, separating them in particular from or from the initial alkanes and optionally from or inert gases. The alkanes produced and thus separated can be recovered outside the separation zone (9), in particular continuously, by a recovery line (10) leaving this zone, whereas the other separated products can be advantageously

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 returned at least in part and preferably continuously in the recycling loop (13) by a recycling line (11).

 From the reactor (1 ') can exit an evacuation line (16) of a substantially solid / gas mixture containing at least a part of the catalyst, especially in a powdered form or granules, taking with it a portion of the alkanes produced, or unreacted initial alkanes and optionally inert gas (s). The discharge line (16) may be a mechanical transport line or a mechanical lift, or preferably a pneumatic conveying line or a pneumatic lift, and may preferably operate continuously. It can lead into a separation zone (17) of the catalyst which can be a phase separator, such as a solid / gas, solid / liquid or solid / liquid / gas separator, a cyclone separator or a separator by decantation. The separation zone (17) can operate in such a way as to partially or completely and preferably continuously remove the catalyst from at least one of the constituents of the mixture discharged through the evacuation line (16), in particular gaseous constituents. or optionally liquids of this mixture, such as the alkanes produced, the initial alkane (s) unreacted and optionally the inert gas (s). From the separation zone (17), a transfer line (18) can exit from the catalyst thus separated and a return line (19) from the other product or products separated in this zone, in particular from a mixture comprising the alkanes produced, the or the initial alkanes which have not reacted and optionally the inert gas or gases. The return line (19) can preferably operate continuously and lead directly or indirectly into the reactor (1 '), in particular via the feed line (3) and / or the recycling loop (13). ). The transfer line (18) may be a mechanical transport line or a mechanical lift, or preferably a pneumatic conveying line or a pneumatic lift, and may preferably operate continuously.

 The transfer line (18) can communicate with an activation zone (20) of the catalyst, preferably an activation zone in the gas phase and operating particularly continuously. The activation zone (20) may comprise a gas phase reactor (20 ') containing a bed (30) preferably fluidized and consisting essentially of

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 the catalyst in a solid form. The gas phase reactor (20 ') may be provided in particular with a fluidization grid (31) and a recycle loop (32) of a gas stream essentially comprising hydrogen, optionally the in situ forming agent. hydrogen, such as methane, and optionally one or more inert gases, such as nitrogen, helium or argon. The recycling loop (32) can leave the top of the reactor (20 ') and return to the base of the latter. It may comprise a compressor (33) intended in particular to circulate, preferably continuously, the gaseous stream in the loop (32) and through the reactor (20 ') according to a particularly rising current, in order to maintain in particular the bed (30) in the fluidized state, and a heat exchanger (34) especially for controlling and maintaining the temperature of the reactor (20 '), in particular the temperature of the bed (30), to a predetermined value. A hydrogen feed line (4) (and optionally an in situ hydrogen forming agent, such as methane) can preferably operate continuously and directly or indirectly to the reactor (20 '), in particular via intermediate of the recycling loop (32). A feed line (6 ') made of inert gas (s) may optionally operate in particular continuously and lead directly or indirectly into the reactor (20'), in particular via the feed line (4) and / or the recycling loop (32). The inert gas (s) supplying the reactor (20 ') may be identical to or different from those introduced into the reactor (1').

 From the recycle loop (32) can advantageously exit a bypass line (35) of the gas stream flowing through the reactor (20 ') and the loop (32).

The bypass line (35) can preferably operate continuously and open into the transfer line (18), in particular to facilitate the transport of the catalyst withdrawn from the separation zone (17) and its introduction into the reactor (20 ' ). The advantage of such a method results in the use of a carrier gas in the transfer line (18) in the form of a gaseous stream which is identical to that flowing through the reactor (20 '). This improves the operation of the transfer line (18) and at the same time the operation of the reactor (20 ').

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 From the recycle loop (32) may optionally exit a recovery line (21) of a substantially gaseous mixture containing at least one alkane, such as ethane and / or its higher homologues, resulting from the activation reaction of the catalyst by the optional agent forming in situ hydrogen, such as methane. The recovery line (21) can preferably operate continuously and open into a separation zone (22), in particular separation by fractionation, condensation or decantation. The separation zone (22) can be operated so as to separate and recover, preferably continuously, the alkane (s) from the mixture, in particular ethane and / or its higher homologues, and to return it, preferably to continuous, by a return line (23) directly or indirectly in the reactor (1 '), in particular via the feed line (3) and / or the recycling loop (13). The other product or products separated in the separation zone (22), such as hydrogen and optionally the in situ forming agent of hydrogen, can be advantageously returned at least partly, directly or indirectly, and preferably continuously. by a line (24) in the reactor (20 '), in particular via the recycling loop (32), another part being able to be evacuated to the outside via a line (25). Such a method makes it possible to improve the efficiency of the process.

 From the reactor (20 ') a withdrawal line (26) can be discharged from a substantially solid / gas mixture containing a part of the activated catalyst, carrying with it hydrogen, optionally the in situ hydrogen forming agent and optionally the inert gas or gases. The withdrawal line can be a mechanical transport line or a mechanical lift, or preferably a pneumatic conveying line or a pneumatic lift, and can operate in particular continuously.

 The withdrawal line (26) may open into a separation zone (27) which may be a phase separator, such as a solid / gas separator, a cyclone separator or a settling separator. The separation zone (27) can operate in such a way as to partially or completely and preferably continuously separate the activated catalyst from the mixture withdrawn from the reactor (20 '), and to turn over the catalyst thus activated and

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 separated, preferably continuously, in the reactor (1 ') through a recycling line (28). The line (28) may be a mechanical transport line or a mechanical lift, or preferably a pneumatic conveying line or a pneumatic lifting line. Thus, the hydrogen-activated catalyst in the reactor (20 ') can be continuously transported and recycled to the reactor (1') where the alkanes are made. In order to facilitate the transport of the activated catalyst to the reactor (1 ') and improve the operation of this reactor, a bypass line (36) of the gas stream flowing through the reactor (1') can leave the recycling loop (13). ), exit into the recycling line (28), and preferably operate continuously. This method advantageously makes it possible to use a carrier gas in the recycle line (28) in the form of a gaseous flow identical to that circulating in the reactor (1 '), and thus to be able to manufacture the alkanes and to activate the catalyst. a completely independent way. Moreover, the fresh catalyst booster line (5) can lead indirectly into the reactor (1 ') via the recycling line (28), especially when the branch line (36) opens into the line (28).

 From the separation zone (27) can exit a return line (29) of the other products or products separated in this zone, in particular hydrogen, optionally hydrogen-forming agent in situ and optionally inert gases, which can be returned directly or indirectly and preferably continuously in the reactor (20 '), in particular via the recycling loop (32). Such a method makes it possible to improve the efficiency of the activation of the catalyst.

 The catalyst used according to the present invention contains at least one metal, Me, bonded to at least one hydrogen atom and / or at least one hydrocarbon radical. It is preferably chosen from supported metal catalysts and in particular grafted onto a solid support.

 The supported metal catalyst and grafted on a solid support generally means a catalyst or metal compound comprising a solid support and at least one metal, Me, which is (chemically) fixed to the support, in particular by at least one single or multiple bond, and in particular that is directly related to at least one of the essential elements (or constituents) of the solid support.

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 The metal Me, present in the catalyst may be at least one metal chosen from lanthanides, actinides and metals of groups 2 to 12, preferably groups 3 to 12, especially from the transition metals of Groups 3 to 11 , especially Groups 3 to 10 of the Periodic Table of Elements.

The metal, Me, can be in particular at least one metal selected from scandium, yttrium, lanthanum, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, rhenium, iron, ruthenium, cobalt, rhodium, iridium, nickel, palladium, platinum, cerium and neodymium. Preferably, it may be chosen from among yttrium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, ruthenium, rhodium and platinum, and more particularly among yttrium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, ruthenium, rhodium and platinum.

 The catalyst may be chosen from catalysts or metal compounds supported and grafted onto a solid support, comprising a solid support and one or more metals, Me, which are identical or different, and in particular (chemically) fixed to the support, in particular by single or multiple bonds. . In the case where the metal, Me, grafted onto a support is bonded to at least one hydrogen atom, the catalyst may be chosen from supported and grafted metal catalysts or compounds comprising a solid support on which is grafted at least one hydride metal, especially a metal hydride Me.

 In the case where the metal, Me, grafted onto a support is bonded to at least one hydrocarbon radical, the catalyst may be chosen from supported and grafted metal catalysts or compounds comprising a solid support on which is grafted at least one organometallic compound, in particular an organometallic compound of the metal Me.

 The catalyst may advantageously be chosen from metal hydrides and organometallic compounds of metal Me, preferably supported and grafted onto a solid support.

 The catalyst may also be advantageously chosen from supported and grafted metal catalysts or compounds comprising a solid support on which

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 are grafted at least two types of metal Me, one in a form (A) of a metal compound where the metal, Me, is bonded to at least one hydrogen atom and / or at least one hydrocarbon radical, and the other in a form (B) of a metal compound where the metal, Me, is only bonded to the support and optionally to at least one other element which is neither a hydrogen atom nor a hydrocarbon radical. In each of the (A) and (B) forms, the catalyst may comprise one or more different metals, Me.

The metal Me present in the form (A) may be identical or different from that present in the form (B). When forms (A) and (B) coexist in the catalyst, the degree of oxidation of the metals Me present in the form (A) may be identical or different from that of the metals Me present in the form (B).

 The solid support may be any solid support, in particular essentially comprising M and X atoms, which are different from one another and generally bonded to each other by single or multiple bonds, so as to form in particular the molecular structure of the solid support. By support essentially comprising M and X atoms, is generally meant a support which comprises as major constituents the M and X atoms and which may comprise, in addition, one or more other atoms capable of modifying the structure of the support.

 The atom M of the support can be at least one of the elements chosen from lanthanides, actinides and elements of Groups 2 to 15 of the Table of the Periodic Table of Elements. The atom M of the support may be identical to or different from the metal, Me. The atom M may be at least one of the elements chosen in particular from magnesium, titanium, zirconium, cerium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, boron, aluminum, gallium, silicon, germanium, phosphorus and bismuth. The atom M of the support is preferably at least one of the elements chosen from lanthanides, actinides and elements of Groups 2 to 6 and Groups 13 to 15 of the Periodic Table of Elements, in particular from silicon, aluminum and phosphorus.

 The atom X of the support, which is different from the atom M, can be chosen from at least one of the elements of Groups 15 and 16 of the Periodic Table of Elements, the element possibly being alone or possibly itself linked to another

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 atom or a group of atoms. In the case where the X atom of the support is chosen in particular from at least one of Group 15 elements, it may optionally be bonded to another atom or to a group of atoms chosen, for example, from a hydrogen atom a halogen atom, in particular a fluorine, chlorine or bromine atom, a hydrocarbon radical, saturated or unsaturated, a hydroxyl group of formula (OH-), a hydrogenosulphide group of formula (SH-), alcoholate groups; thiolate groups, silyl (or silane) or organosilyl (or organosilane) groups. Preferably, the X atom of the support is at least one of the elements selected from oxygen, sulfur and nitrogen, and more particularly from oxygen and sulfur.

 The M and X atoms, which generally represent the essential elements of the solid support, may in particular be linked together by single or double bonds. In a preferred variant, the solid support may be chosen from oxides, sulphides and azides, in particular M, and mixtures of two or three of the oxides, sulphides and / or azides. More particularly, the support may be an oxide, in particular M, and may be chosen from simple or mixed oxides, in particular M, or mixtures of oxides, in particular M.sub.2. The support may be, for example, chosen from metal oxides, refractory oxides and molecular sieves, in particular from silica, alumina, silicon aluminates, aluminum silicates which are simple or modified with other metals, zeolites, clays, titanium oxide, cerium oxide, magnesium oxide, niobium oxide, tantalum oxide and zirconium oxide. The support may also be a metal oxide or refractory, optionally modified with an acid, and may optionally comprise in particular an atom M bonded to at least two atoms X different from each other, for example the oxygen atom and the sulfur atom . Thus, the solid support can be chosen from sulphated metal or refractory oxides, for example a sulphated alumina or a sulphated zirconia. The support may also be chosen from sulphides and metal or refractory oxides, sulphides, for example a molybdenum sulphide, a tungsten sulphide or a sulphurated alumina. The support may also be chosen from azides, in particular boron.

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 The essential constituents of the solid support are preferably the M and X atoms described above. In addition, the solid support has the advantage generally of having on the surface X atoms likely to be part of the coordination sphere of the metal, Me, of the catalyst, especially when the catalyst is chosen from the metal compounds supported and grafted on a solid support. Thus, at the surface of the support, the atom X which is bonded to at least one metal atom, Me, may advantageously also be bonded to at least one M. The bonds between X and M and those between X and Me can be single or double bonds.

 In the case of a supported and grafted metal catalyst on a support, the metal, Me, present in particular in the form (A), can be bonded on the one hand to the support, in particular to at least one atom constituting the support, preferably the X atom of the support as described above, in particular by a single or double bond, and on the other hand to at least one hydrogen atom and / or at least one hydrocarbon radical, in particular via a carbon bond -Metal single, double or triple.

 The catalyst, for example in the form (A) described above, may contain at least one metal, Me, bonded to at least one hydrocarbon radical, R, which may be saturated or unsaturated, have from 1 to 20, preferably from 1 at 10 carbon atoms, and be chosen from alkyl, alkylidene or alkylidyne radicals, especially from C 1 to C 10, aryl radicals, especially C 6 to C 10 radicals, and aralkyl, aralkylidene or aralkylidyne radicals, especially C 7 to C 14 radicals. The metal, Me, can be bonded to the hydrocarbon radical, R, by one or more single, double or triple carbon-metal bonds. It can be a simple carbon-metal bond, in particular of the type #: in this case, the hydrocarbon radical, R, can be an alkyl radical, in particular a linear or branched radical, for example from C 1 to C 10, preferably Ci, or an aryl radical, for example the phenyl radical, or an aralkyl radical, for example the benzyl radical. Alkyl radical generally means a monovalent aliphatic radical originating from the removal of a hydrogen atom in the molecule of an alkane, or an alkene, or an alkyne, for example the methyl or ethyl radical. , propyl, neopentyl, allyl or ethinyl. The methyl radical is preferred.

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 It may also be a carbon-metal double bond, in particular of # type: in this case, the hydrocarbon radical, R, may be an alkylidene radical, in particular linear or branched, for example from C 1 to C 10, preferably Ci, or an aralkylidene radical, for example C7 to C14. By alkylidene radical is generally meant a divalent aliphatic radical derived from the removal of two hydrogen atoms on the same carbon of the molecule of an alkane, or an alkene, or an alkyne, for example the radical methylidene, ethylidene, propylidene, neopentylidene or allylidene.

The methylidene radical is preferred. By aralkylidene radical is generally meant a divalent aliphatic radical derived from the removal of two hydrogen atoms on the same carbon of an alkyl, alkenyl or alkynyl branch of an aromatic hydrocarbon.

 It may also be a carbon-metal triple bond: in this case, the hydrocarbon radical, R, may be an alkylidyne radical, in particular linear or branched, for example from C 1 to C 10, preferably C 1, or aralkylidyne radical, for example from C7 to C14. By alkylidyne radical is generally meant a trivalent aliphatic radical originating from the removal of three hydrogen atoms on the same carbon of the molecule of an alkane, or an alkene, or an alkyne, for example the radical methylidyne, ethylidyne, propylidyne, neopentylidyne or allylidyne. The methylidyne radical is preferred. By aralkylidyne radical is generally meant a trivalent aliphatic radical derived from the removal of three hydrogen atoms on the same carbon of an alkyl, alkenyl or alkynyl branch of an aromatic hydrocarbon.

 The catalyst may advantageously be selected from supported or grafted metal catalysts or compounds on a solid support, comprising the metal, Me, present in both forms (A) and (B). Such a catalyst has the advantage of having a very high catalytic activity in the manufacture of alkanes. The form (A) of the catalyst is that described above. In the form (B), the metal, Me, is preferably bonded only to the support, in particular to one or more atoms constituting the essential elements of the support, in particular to one or more X atoms of the support as described above, for example by single or double bonds.

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 In the form (B), the metal, Me, may optionally be bonded, in addition to the support, to at least one other element which is neither a hydrogen atom nor a hydrocarbon radical. The other element linked to the metal Me may be, for example, at least one of the elements of Groups 15 to 17 of the Periodic Table of Elements, which element may be alone or itself linked to at least one atom of hydrogen and / or at least one hydrocarbon radical and / or at least one silylated (or silane) or organosilyl (or organosilane) group. In particular, the metal, Me, present in the form (B) may optionally be bonded, in addition to the support, to at least one atom of the elements chosen from oxygen, sulfur, nitrogen and halogens, especially the fluorine, chlorine or bromine. Thus, for example, the metal, Me, may be linked, by a single bond, to one or more halogen atoms, especially fluorine, chlorine or bromine. It can also be linked, by a double bond, to one or more oxygen or sulfur atoms, especially in the form of an oxide or a metal sulphide. It may also be linked, by a single bond, to at least one oxygen or sulfur atom, itself linked to a hydrogen atom or to a saturated or unsaturated hydrocarbon radical, in particular from C 1 to C 20, preferably from C 1 to C 10, for example in the form of a hydroxide, a hydrogen sulfide, an alcoholate or a thiolate. It can be further bound, by a single bond, to a silyl or organosilyl group. It can also be linked, by a single bond, to an amido (or amide) group, for example of formulas (NH 2 -), (NHR -) or (NRR '-) in which R and R' being identical or different represent saturated or unsaturated hydrocarbon radicals, especially of C 1 to C 20, preferably of C 1 to C 10, or silyl or organosilyl groups, or be bonded, by a double bond, to an imido (or imide) group, for example of the formula (NH =) or, by a triple bond, to a nitrido (or azide) group, for example of formula (N =).

 It is preferred to use the supported and grafted metal catalysts on a solid support, in which the metal, Me, grafted onto the support is present in both forms (A) and (B), since these catalysts advantageously have a catalytic activity. very high in the manufacture of alkanes. This is particularly the case when, for 100 moles of metal Me grafted onto the support, the catalyst comprises:

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 (a) from 5 to 95 moles, preferably from 10 to 90 moles, especially from 20 to 90 moles, in particular from 25 to 90 moles, or more particularly from 30 to 90 moles of the metal Me in the form (A), and (b) from 95 to 5 moles, preferably from 90 to 10 moles, especially from 80 to 10 moles, in particular from 75 to 10 moles, or more preferably from 70 to 10 moles of the Me metal in the form (B). .

 The catalysts described above can be prepared in various ways. A first method for preparing a supported and grafted metal catalyst on a solid support can comprise the following steps: (a) grafting an organometallic precursor (P) comprising the metal Me bonded to at least one hydrocarbon ligand on the solid support, and (b) treating the solid product resulting from step (a) with hydrogen or a reducing agent capable of forming a Me-hydrogen metal bond, preferably by hydrogenolysis of the hydrocarbon ligands, at a temperature in particular at most equal to the temperature T1 at which the catalyst is formed only in the form (A) as defined above.

 The temperature of step (b) is chosen in particular so that it is at most equal to the temperature Tl where only the form (A) of the catalyst is formed, that is to say where only the metal hydride is formed. The temperature of stage (b) may in particular be chosen in a range from 50 to 160.degree. C., preferably from 100 to 150.degree. C. Stage (b) may take place under an absolute pressure of 10-3 at 10 MPa and for a duration ranging from 1 to 24 hours, preferably from 5 to 20 hours.

 A second method of preparing a catalyst may comprise the following steps:

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 (a) grafting an organometallic precursor (P) comprising the metal Me bonded to at least one hydrocarbon ligand on the solid support, and (b) treating the solid product resulting from step (a) with hydrogen or an agent reducing agent capable of forming a Me-hydrogen metal bond, preferably by hydrogenolysis of the hydrocarbon ligands, at a temperature above the temperature Tl at which the catalyst is formed only in the form (A), and below the temperature T2 at which the catalyst is formed only in the form (B), the forms (A) and (B) being those described above.

 The temperature of step (b) is chosen in particular so that it is greater than the temperature T1 where only the shape (A) is formed. It may in particular be at least 10 C, preferably at least 20 C, in particular at least 30 C or even at least 50 C higher than the temperature T1. it is lower than the temperature T2 where only the form (B) is formed. It may in particular be at least 10 C, preferably at least 20 C, especially at least 30 C or even at least 50 C below the temperature T2. The temperature of step (b) may, for example, be chosen in a range from 165 ° C. to 450 ° C., preferably from 170 ° to 430 ° C., in particular from 180 ° to 390 ° C., in particular from 190 ° to 350 ° C. or 200 ° C. at 320 ° C. Step (b) can be carried out under an absolute pressure of 10-3 to 10 MPa, and for a duration ranging from 1 to 24 hours, preferably from 5 to 20 hours.

 A third method for preparing a catalyst may comprise the following steps: (a) grafting an organometallic precursor (P) comprising the metal Me bonded to at least one hydrocarbon ligand on the solid support, and then

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 (b) treating the solid product resulting from step (a) with hydrogen or a reducing agent capable of forming a Me-hydrogen metal bond, preferably by complete hydrogenolysis of the hydrocarbon ligands, at a temperature at most equal to at the temperature Tl at which the catalyst is formed only in the form (A) as defined above, so as to form a metal hydride in the form (A), and (c) heat-treating the solid product resulting from the step (b), preferably in the presence of hydrogen or a reducing agent, at a temperature above the temperature of step (b) and below the temperature T2 at which the catalyst is formed only in the form (B) ) as defined above.

 Step (b) of the process can be carried out under the same conditions, in particular temperature, as those of step (b) of the first preparation process.

Step (c) can be carried out at a temperature, under a pressure and for a duration equivalent to those described in step (b) of the second preparation process.

A fourth process for preparing a catalyst may comprise the following steps: (a) grafting an organometallic precursor (P) comprising the metal Me bonded to at least one hydrocarbon ligand to the solid support comprising functional groups capable of grafting the precursor ( P), by contacting the precursor (P) with the solid support so as to graft the precursor (P) onto the support by reaction of (P) with a part of the functional groups of the support, preferably of
5 to 95% of the functional groups of the support, then (b) heat-treating the solid product resulting from step (a), preferably in the presence of hydrogen or an agent

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 reducing agent, at a temperature equal to or greater than the temperature T2 at which the catalyst is formed only in the form (B) as defined above, and then (c) grafting on the solid product resulting from step (b) an organometallic precursor (P '), identical or different from (P), comprising the metal Me bonded to at least one hydrocarbon ligand, the metal Me and the ligand being identical or different from those of (P), by contacting the precursor (P) ') with the solid product resulting from step (b) so as to graft the precursor (P') onto the support by reacting (P ') with the functional groups remaining in the support, and optionally (d) treating the solid product resulting from step (c) with hydrogen or a reducing agent capable of forming Me-hydrogen metal bonds, preferably by complete hydrogenolysis of the hydrocarbon ligands of the grafted precursor (P '), at a temperature in particular at more equal the temperature T at which the catalyst is formed solely in the form (A) as defined above.

 Step (b) of the process may be carried out at a temperature such that most, preferably all, of the precursor (P) grafted onto the support is converted into a metal compound in the form (B). The temperature during step (b) may be chosen in a range from 460 C, preferably 480 C, especially 500 C to a temperature below the sintering temperature of the support. Step (d) is optional and can be performed at a temperature equivalent to that of step (b) of the first preparation process.

 A fifth method of preparing a catalyst may comprise the following steps:

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 (a) grafting an organometallic precursor onto the solid support under the same conditions as in step (a) of the preceding preparation method, then (b) treating the solid product resulting from step (a) under the same conditions than in step (b) of the preceding preparation process, and then (c) bringing the solid product resulting from step (b) into contact with at least one compound Y that is capable of reacting with the metal Me of the form ( A) and / or (B) prepared above, the contacting being preferably followed by a removal of the unreacted compound Y and / or a heat treatment at a temperature below the sintering temperature of the support and then (d) grafting onto the solid product resulting from step (c) an organometallic precursor (P '), identical to or different from (P), comprising the metal Me bonded to at least one hydrocarbon ligand, the metal Me and the ligand being identical or different from those of (P), by setting into con tact of the precursor (P ') with the product resulting from step (c) so as to graft the precursor (P') on the support by reaction of (P ') with the functional groups remaining in the support, and optionally ( e) treating the solid product resulting from step (d) with hydrogen or a reducing agent capable of forming Me-hydrogen metal bonds, preferably by complete hydrogenolysis of the hydrocarbon ligands of the grafted precursor (P '), a temperature in particular at most equal to the temperature Tl at which the catalyst is formed only in the form (A) as defined above.

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 Step (b) of the process may be carried out at a temperature equivalent to that of step (b) of the fourth preparation process. In step (c), the compound Y may be chosen from molecular oxygen, water, hydrogen sulphide, ammonia, an alcohol, especially of C 1 to C 20, preferably of C 1 to C 10, thiol, especially of C 1 to C 20, preferably of C 1 to C 10, a primary or secondary amine of C 1 to C 20, preferably of C 1 to C 10, a molecular halogen, in particular fluorine, chlorine or molecular bromine, and a halide of hydrogen, for example of formula HF, HC1 or HBr. The heat treatment possibly performed at the end of step (c) can be carried out at a temperature ranging from 25 to 500 C. Step (e) is optional and can be carried out at a temperature equivalent to that of step (b) the first preparation process.

In the processes for preparing a supported and grafted metal catalyst as described above, the grafting operation on a solid support uses at least one organometallic precursor (P) or (P ') comprising the metal Me bonded to at least one hydrocarbon ligand. The precursor can answer the general formula:
Me R'a (4) in which Me has the same definition as above, R 'represents one or more hydrocarbon ligands, identical or different, saturated or non saturated, in particular aliphatic or alicyclic, in particular of Ci to C20, preferably of Ci to CI (), having for example the same definition as that given above for the hydrocarbon radical, R, of the metal catalyst, and a is an integer, equal to the degree of oxidation of the metal Me.

The radical R 'can be chosen from alkyl, alkylidene, alkylidyne, aryl, aralkyl, aralkylidene and aralkylidyne radicals. The metal Me may be bonded to one or more carbons of the hydrocarbon ligands, R ', in particular by single, double or triple carbon-metal bonds, such as those connecting the metal Me to the hydrocarbon radical, R, in the catalyst.

 In the processes for preparing a supported and grafted metal catalyst as described above, the solid support is preferably previously subjected to a heat treatment of dehydration and / or dehydroxylation,

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 in particular at a temperature below the sintering temperature of the support, preferably at a temperature ranging from 200 to 1000 ° C., preferably from 300 ° to 800 ° C., for a period which can range from 1 to 48 hours, preferably from 5 to 24 hours. The temperature and the duration can be chosen so as to create and / or leave in the support and at predetermined concentrations, functional groups capable of grafting by reaction the precursor (P) or (P '). Among the known functional groups for the supports, there may be mentioned groups of formulas XH in which H represents a hydrogen atom and X corresponds to the same definition as given previously for the support, and in particular may represent an atom chosen from oxygen, sulfur and nitrogen. The most well-known functional group is the hydroxyl group.

 The grafting operation in general may be carried out by sublimation or by contacting the precursor in a liquid medium or in solution. In the case of sublimation, the precursor used in the solid state can be heated under vacuum and under conditions of temperature and pressure ensuring its sublimation and its migration in the vapor state on the support. Sublimation can be carried out at a temperature ranging from 20 to 300 ° C., in particular from 50 to 150 ° C., under vacuum.

 It is also possible to carry out grafting by contacting it in a liquid medium or in solution. In this case, the precursor can be dissolved in an organic solvent such as pentane or ethyl ether, so as to form a homogeneous solution, and the support can then be suspended in the solution containing the precursor or by any other method ensuring contact between the support and the precursor. The contacting can be carried out at room temperature (20 ° C.), or more generally at a temperature ranging from -80 ° C. to 150 ° C. under an inert atmosphere, such as nitrogen. If only a portion of the precursor is attached to the support, the excess can be removed by washing or reverse sublimation.

 The following examples illustrate the present invention.

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 to be reused in the following metathesis reaction of propane. In each propane metathesis reaction, the instantaneous propane reaction rate, expressed as the number of moles of propane reacted per mole of tantalum per hour, in particular the initial velocity (at time t = 0 minutes), is measured. ) and the final speed after a reaction time of 8000 minutes. In particular, the initial rate of the metathesis reaction can be compared after each catalyst activation operation at the final rate of the preceding metathesis reaction, and thus show that the catalyst has been effectively reactivated after each catalyst activation operation.

The metathesis reaction of propane can be written essentially according to the following equation:
2 C3H8 # C2H6 + C4H10 (8)
Each metathesis reaction of propane is carried out under the following conditions. One reactor contains 0.52 g of tantalum catalyst (containing 5.33% by weight of tantalum) under an argon atmosphere and at room temperature (25 ° C). The reactor is filled with propane at atmospheric pressure and is then heated to 150 ° C under a continuous stream of propane at a constant rate of 1 ml / min (measured under normal conditions) at atmospheric pressure. This direct current is maintained under these conditions, at 150 ° C. and under atmospheric pressure, for a period of 8000 minutes.

 Each activation operation of the catalyst is carried out under the following conditions. The tantalum catalyst is recovered in the reactor at the end of a previous metathesis reaction, after cooling the reactor to room temperature and then filling the reactor with hydrogen at atmospheric pressure. The reactor thus containing the catalyst is traversed by a continuous stream of hydrogen at a constant flow rate of 1 ml / min (measured under normal conditions), at atmospheric pressure. Meanwhile, the temperature of the reactor is regularly raised from 25.degree. C. to 150.degree. C. at a constant speed of 40.degree. C./h, and is then kept constant at 150.degree. C. for 15 hours. At the end of this period, the reactor is cooled to room temperature, then evacuated and filled with argon, so that the catalyst thus activated is ready for a new metathesis reaction.

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 It is observed that the metathesis reaction of the propane thus produced produces in each case essentially ethane and butane, and small amounts of methane and C5 homologues. At each metathesis reaction, the initial and final reaction rates of the propane are measured. These measurements are made during a first metathesis reaction, then a second metathesis reaction preceded by a first activation, and a third metathesis reaction, itself preceded by a second activation. The results of these measurements are summarized in Table 1.

Table 1

<Tb>
<tb> Tests <SEP> Speed <SEP> initial <SEP> (*) <SEP> (at <SEP> Speed <SEP> final <SEP> (*) <SEP> (at
<tb> the instant <SEP> t <SEP> = <SEP> 0 <SEP> min) <SEP> the instant <SEP> t <SEP> = <SEP> 8000 <SEP> min)
<tb> First <SEP> reaction <SEP> of
<tb> metathesis <SEP> 1.46 <SEP> 0.18
<tb> Second <SEP> reaction <SEP> of
<tb> metathesis <SEP> (after <SEP> one <SEP> 0.95 <SEP> 0.11
<tb> first <SEP> activation)
<tb> Third <SEP> reaction <SEP> of
<tb> metathesis <SEP> (after <SEP> one <SEP> 0.76 <SEP> 0.07
<tb> second <SEP> activation)
<Tb>
(*) expressed as the number of moles of propane reacted per mole of tantalum catalyst and per hour.

 Table 1 shows that the tantalum catalyst is reactivated (or regenerated) in the metathesis reaction of propane after each catalyst activation operation with hydrogen.

 Example 3: metathesis reaction of propane in the presence of a tantalum catalyst and separate activation of the catalyst with hydrogen.

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 The same successive metathesis reactions of propane and the same catalyst activation operations with hydrogen as in Example 2 are carried out, except that in each catalyst activation operation, instead of maintaining for 15 hours the temperature of the reactor at 150 C, it is maintained for 36 hours at 150 C.

 Under these conditions, it is found that the initial speed of the second metathesis reaction of propane (after the first activation) is not only higher than the final speed of the first metathesis reaction, but close to or almost equivalent to the initial speed of the metathesis. first metathesis reaction. The same is true for the third metathesis reaction of propane (after the second activation): the initial speed of the third metathesis reaction is close to or almost equivalent to the initial speed of the second metathesis reaction, so that the it can be said that, thanks to the operation of activating the catalyst with hydrogen, the catalytic activity is almost completely restored at the moment of the metathesis reaction following the activation operation.

 Example 4 Preparation of a Tungsten Catalyst

A supported and grafted tungsten catalyst on silica is prepared exactly as in Example 1, except that in the first step, instead of using a solution of tantalum tris (neopentyl) neopentylidene in n- pentane, a solution of tris (neopentyl) neopentylidyne of tungsten in n-pentane, corresponding to the general formula:
W [- CH 2 -C (CH 3) 3] 3 [# C-C (CH 3) 3] (9) and that in the second step, instead of carrying out hydrogenolysis at 250 ° C., it is carried out at 150 ° C. This gives a tungsten catalyst supported on silica, essentially in the form (A) of a tungsten hydride.

 Example 5 Propane metathesis reaction in the presence of a tungsten catalyst and separate activation of the catalyst with hydrogen.

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 The same successive reactions of metathesis of propane and the same operations of activation of the catalyst by hydrogen as in Example 2, except that instead of using the tantalum catalyst, the catalyst is used. tungsten prepared in Example 4.

 Under these conditions, it is observed that the tungsten catalyst is reactivated in the metathesis reaction of propane after each activation operation of the catalyst with hydrogen.

 Example 6: metathesis reaction of propane in the presence of a tantalum catalyst with simultaneous activation of the catalyst with hydrogen.

 The metathesis reaction of propane is carried out under the following conditions. In a reactor, 0.52 g of the tantalum catalyst prepared in Example 1 (containing 5.33% by weight of tantalum) is introduced at ambient temperature (25 ° C.) under an argon atmosphere. The reactor is filled with a mixture of propane and hydrogen in a molar ratio between propane and hydrogen equal to 9/1, at atmospheric pressure. The reactor is then heated to 150 ° C. under a continuous stream of the mixture of propane and hydrogen at a constant flow rate of 1 ml / min (measured under normal conditions) at atmospheric pressure. This direct current is maintained under these conditions, at 150 ° C. under atmospheric pressure, for 8000 minutes.

 It is observed that under these conditions, the metathesis reaction of propane producing in particular ethane and butane proceeds simultaneously with an activation reaction of the tantalum catalyst whose activity in the metathesis reaction is particularly sustained during the course of the reaction. time.

 Example 7 Propane metathesis reaction in the presence of a tantalum catalyst with simultaneous activation of the catalyst with hydrogen.

<Desc / Clms Page number 53>

 A metathesis reaction of propane is carried out exactly as in Example 6, except that instead of filling the reactor with the mixture of propane and hydrogen, it is filled with a mixture of propane, argon and of hydrogen in a molar ratio between propane, argon and hydrogen equal to 90/10/1 respectively. This mixture is then used under the same conditions as that of Example 6.

 It is observed that under these conditions, the metathesis reaction of propane producing essentially ethane and butane proceeds simultaneously with an activation reaction of the tantalum catalyst whose activity in the metathesis reaction is particularly sustained during the course of the reaction. time.

 Example 8: methane-propane reaction of propane in the presence of a tantalum catalyst with simultaneous activation of the catalyst with hydrogen.

 A tantalum supported and grafted catalyst is prepared exactly as in Example 1, except that in the second step, instead of carrying out the hydrogenolysis at 150 ° C., it is carried out at 250 ° C. A catalyst is thus obtained. tantalum supported on silica, of which 72% of tantalum is in the form of a tantalum hydride corresponding to the general formula (7) as mentioned above.

 Through a reactor heated to 250 ° C. and containing 0.3 g of the tantalum catalyst thus prepared, a mixture of methane is passed continuously at a constant flow rate of 1.5 ml / min (measured under normal conditions). propane and hydrogen in a molar ratio of methane, propane and hydrogen respectively equal to 106 / 7x102 / 1.5x102 at a methane partial pressure of 5 MPa.

 It is observed that under these conditions, the methane-olysis reaction of propane producing essentially ethane proceeds simultaneously with an activation reaction of the tantalum catalyst whose activity in the methaneolysis reaction is particularly sustained over time. .

<Desc / Clms Page number 54>

 Example 9: methane-propane reaction of propane in the presence of a tantalum catalyst and separate activation of the catalyst with hydrogen.

 Several successive reactions of propane methane-olysis are carried out under the same conditions and in the presence of the tantalum catalyst prepared in Example 8, except that at the end of each methane-olysis reaction, the catalyst is recovered. and is each time subjected to an activation operation using hydrogen carried out exactly as in Example 2, before being reused in the following methane-propane propane reaction. In each propane methane-olysis reaction, the initial velocity (at time t = 0 minutes) and the final velocity (at time t = 8000 minutes) of the propane reaction are measured so as to be able to compare the initial rate of the methane-olysis reaction after each catalyst activation operation at the final rate of the previous methane-olysis reaction.

 Each propane methane-olysis reaction is carried out under the following conditions. A reactor contains 0.52 g of the tantalum catalyst prepared in Example 8 under an argon atmosphere and at room temperature (25 ° C). The reactor is filled with a mixture of methane and propane in a molar ratio between methane and propane equal to 106 / 7x102, under a methane partial pressure of 5 MPa, and then is heated to 250 C under a direct current of this mixture at a constant flow rate of 1.5 ml / min (measured under normal conditions) under a methane partial pressure of 5 MPa for a period of 8000 minutes.

 Each catalyst activation operation is carried out as in Example 2 except that instead of recovering the catalyst at the end of each propane metathesis reaction, it is recovered at the end of each methane reaction. propane olysis as described in this Example.

 It is observed that under these conditions, the tantalum catalyst is reactivated (or regenerated) in the propane methane-olysis reaction after each activation operation of the catalyst with hydrogen.

Claims (4)

1. A process for producing alkanes comprising contacting at least one initial alkane with a metal catalyst containing at least one metal, Me, bonded to at least one hydrogen atom and / or at least one radical hydrocarbon, characterized in that during the manufacture of alkanes, the catalyst is contacted with hydrogen. 2. A method of activating a metal catalyst for producing alkanes and containing at least one metal, Me, bonded to at least one hydrogen atom and / or at least one hydrocarbon radical, characterized in that during the manufacture of alkanes made by contacting the catalyst with at least one initial alkane, the catalyst is contacted with hydrogen. 3. Method according to claim 1 or 2, characterized in that the hydrogen is used together with an in situ hydrogen forming agent. Periodic Classification of Elements, in particular among the transition metals of Groups 3 to 11, in particular Groups 3 to 10 of the said Table. 4. Method according to any one of claims 1 to 3, characterized in that the metal Me is at least one metal selected from lanthanides, actinides and metals of Groups 2 to 12, preferably Groups 3 to 12 of Table of the 5. Process according to claim 4, characterized in that the metal Me is at least one metal chosen from scandium, yttrium, lanthanum, titanium and zirconium. <Desc / Clms Page number 56>  hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, rhenium, iron, ruthenium, cobalt, rhodium, iridium, nickel, palladium, platinum, cerium and neodymium. 6. Method according to claim 4, characterized in that the metal Me is at least one metal selected from yttrium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum. , tungsten, ruthenium, rhodium and platinum. 7. Method according to any one of claims 1 to 6, characterized in that the catalyst is selected from supported metal catalysts and in particular grafted onto a solid support. C80, especially C4 to C12? or C18 to Cg8, and cycloalkanes substituted with at least one linear or branched alkane chain, preferably C4 to Cg8, in particular C4 to C17 or C18 to C80. 8. Process according to any one of Claims 1 to 7, characterized in that the initial alkane or alkanes are chosen from linear alkanes, preferably from C2 to C80, in particular from C2 to C17 or from C18 to C80, alkanes. branched, preferably from C4 to 9. Process according to any one of claims 1 to 7, characterized in that the initial alkane or alkanes are selected from methane and mixtures of methane with one or more other initial alkanes selected from linear alkanes, branched alkanes and cycoalkanes substituted by at least one linear or branched alkane chain. 3-pentane, dimethyl-2,3-butane, n-heptane, isoheptane, n-octane and 10. Process according to any one of claims 1 to 7, characterized in that the initial alkane (s) are chosen from ethane, propane, n-butane, isobutane, n-pentane and isopentane. , n-hexane, isohexane, methyl-2-pentane, methyl- <Desc / Clms Page number 57>  isooctane, and among methane and mixtures of methane with at least one of the initial alkanes mentioned above. 11. Process according to any one of claims 1 to 7, characterized in that the initial alkane or alkanes are chosen from liquefied petroleum gases, natural gas, wet gas or moist natural gas, natural gas liquids. and synthetic crude. 12. Process according to any one of claims 1 to 11, characterized in that the production of alkanes is carried out by subjecting, as main step, the initial alkane (s) to a metathesis reaction of carbon-carbon bonds. in the presence of the catalyst and optionally at least one other initial alkane. 13. Process according to any one of claims 1 to 11, characterized in that the production of alkanes is carried out by subjecting, as a main step, the initial alkane (s) to a cross-metathesis reaction comprising the implementation of contact of the initial alkane (s) with the catalyst containing at least one metal, Me, linked to at least one hydrocarbon radical. 14. Process according to any one of Claims 1 to 11, characterized in that the production of alkanes results, as a main step, in bringing methane and one or more other initial alkanes into contact with each other. the catalyst. 15. Method according to any one of claims 1 to 11, characterized in that the manufacture of alkanes results, as a main step, of bringing the methane into contact with the catalyst. 16. Process according to any one of Claims 1 to 15, characterized in that the production of alkanes is carried out in the presence of one or more inert agents, in particular liquid or gaseous agents, in particular of one or more inert gases. <Desc / Clms Page number 58>  17. Process according to any one of claims 1 to 16, characterized in that the production of alkanes is carried out batchwise or, preferably, continuously. 18. Process according to any one of claims 1 to 17, characterized in that the catalyst is brought into contact with the hydrogen by adding hydrogen to the catalyst. 19. A method according to any one of claims 1 to 18, characterized in that the contacting of the catalyst with hydrogen is carried out by adding hydrogen to the catalyst and by in situ formation of hydrogen in the presence of the catalyst. 20. Process according to claim 19, characterized in that the in situ formation of hydrogen is carried out using an in situ hydrogen forming agent, preferably chosen from agents capable of releasing hydrogen. in particular by a physical action, and among agents capable of forming hydrogen by chemical reaction, especially in the presence of the catalyst. Periodic Classification of Elements. 21. Process according to claim 20, characterized in that the agent capable of releasing hydrogen is chosen from metals and alloys of metals capable of reversibly accumulating hydrogen, and preferably from metal hydrides and hydrides of metal alloys, in particular metals chosen from lanthanides, actinides and metals of Groups 2 to 12 and more particularly the transition metals of Groups 3 to 11 of the Table of 22. The method of claim 20, characterized in that the agent capable of forming hydrogen by chemical reaction is methane, used in particular in the presence of the catalyst. <Desc / Clms Page number 59> 23. Method according to any one of claims 19 to 22, characterized in that the contacting of the catalyst with hydrogen is carried out by adding hydrogen and a hydrogen-forming agent to the catalyst. . 24. A method according to any one of claims 1 to 23, characterized in that the amount of hydrogen and optionally an in situ forming agent of hydrogen, engaged in contacting with the catalyst is chosen such so that it is sufficient to activate the catalyst, or in particular to reduce or slow down the loss of catalyst activity over time in the manufacture of alkanes, or more particularly to maintain the activity of the catalyst in the manufacture of alkanes at a higher level than expected in the absence of any catalyst treatment. 20 to 400 C. 25. Process according to any one of Claims 1 to 24, characterized in that the catalyst is brought into contact with hydrogen at a temperature ranging from -30 ° C to + 800 ° C, preferably from 0 ° C to 600 ° C. , in particular from 20 to 500 C or from 26. Process according to any one of claims 1 to 25, characterized in that the duration of contacting the catalyst with hydrogen is at least 1 minute and at most 72 hours. 27. Method according to any one of claims 1 to 26, characterized in that the contacting of the catalyst with hydrogen is carried out in the presence of one or more inert agents, in particular liquid or gaseous, in particular a or several inert gases. 28. Process according to any one of Claims 1 to 27, characterized in that the catalyst is brought into contact with the hydrogen in batch form or, preferably, continuously. <Desc / Clms Page number 60> 29. A method according to any one of claims 1 to 28, characterized in that the catalyst contacting with hydrogen and optionally an in situ forming agent of hydrogen is carried out in the presence of or initial alkanes. 30. Process according to any one of claims 1 to 29, characterized in that it comprises the additions of or initial alkanes, hydrogen and optionally an in situ forming agent for hydrogen to the catalyst, these addition being preferably carried out simultaneously and / or continuously. 31. A method according to any one of claims 1 to 27, characterized in that in a discontinuous production of alkanes, the contacting of the catalyst with hydrogen and optionally an in situ forming agent of hydrogen is carried out. discontinuously, in the presence of or initial alkanes. 32. A method according to any one of claims 1 to 27, characterized in that in a continuous production of alkanes, the contacting of the catalyst with hydrogen and optionally an in situ hydrogen forming agent is carried out. continuously, in the presence of or initial alkanes. 33. The method of claim 32, characterized in that it carries out continuous and simultaneous additions of or initial alkanes, hydrogen and optionally the in situ forming agent of hydrogen to the catalyst. 34. Process according to any one of claims 1 to 27, characterized in that in a continuous production of alkanes, the contacting of the catalyst with hydrogen and optionally an in situ hydrogen forming agent is carried out discontinuously, in the presence of or initial alkanes, while simultaneously the initial alkane (s) are added to said catalyst. <Desc / Clms Page number 61> 35. Process according to claim 34, characterized in that discontinuous or sequential additions of hydrogen and optionally of the in situ hydrogen forming agent are carried out on the catalyst. 36. Process according to claim 35, characterized in that the discontinuous or sequential additions are carried out regularly over time, or in such a way that the activity of the catalyst during the continuous manufacture of alkanes is maintained at a predetermined level. and in particular greater than that expected in the absence of any treatment of the catalyst. 37. A method according to any one of claims 1 to 27, characterized in that the contacting of the catalyst with hydrogen and optionally an in situ forming agent of hydrogen is carried out in the absence of or initial alkanes . 38. Process according to claim 37, characterized in that the catalyst contacted with the initial alkane (s) in the production of alkanes is separated from the alkanes, in particular from the initial alkanes or the unreacted alkanes and the alkanes produced. before it is brought into contact with hydrogen and optionally the in situ forming agent for hydrogen. 39. A method according to claim 37 or 38, characterized in that in a discontinuous production of alkanes, the contacting of the catalyst with hydrogen and optionally the in situ forming agent of hydrogen is carried out discontinuously, in the absence of or initial alkanes. 40. Process according to claim 39, characterized in that it comprises the following successive steps, carried out in particular in a repetitive manner: (a) recovering the catalyst put in contact with the initial alkane (s) at the end of manufacture batch of alkanes, (b) separating the catalyst thus recovered, alkanes and in particular the initial or unreacted alkanes and alkanes produced, (c) <Desc / Clms Page number 62>  contacting or activating discontinuously the catalyst thus separated with hydrogen and optionally the in situ forming agent for hydrogen, (d) optionally separating the catalyst thus activated from this or these latter, at the end of the contact or discontinuous activation, and (e) bringing the catalyst back into contact with the initial alkane (s) in another discontinuous production of alkanes. 41. A method according to claim 37 or 38, characterized in that in a discontinuous production of alkanes, contacting the catalyst with hydrogen and optionally the in situ forming agent of hydrogen is carried out continuously, in the absence of or initial alkanes. 42. Process according to claim 41, characterized in that it comprises the following successive stages, carried out in particular in a repetitive manner: (a) recovering the catalyst put in contact with the initial alkane (s) at the end of manufacture batch of alkanes, (b) separating the catalyst thus recovered, alkanes and in particular the initial or unreacted alkanes and alkanes produced, (c) adding and mixing the thus separated catalyst to a part of the catalyst in contact or continuously activated with hydrogen and optionally the in situ hydrogen forming agent, (d) withdrawing and recovering a portion of the catalyst thus contacted or activated continuously, (e) optionally separating the portion of the catalyst as well as recovered and recovered, hydrogen and optionally the in situ hydrogen forming agent, and (f) contacting the catalyst portion with the initial alkane (s) in another manufacturer. discontinuous cation of alkanes. 43. A method according to claim 37 or 38, characterized in that in a continuous production of alkanes, the contacting of the catalyst with hydrogen and optionally the in situ forming agent of hydrogen is carried out discontinuously, in the absence of or initial alkanes. <Desc / Clms Page number 63> 44. Process according to claim 43, characterized in that it comprises the following successive stages, carried out in particular in a repetitive manner: (a) taking and recovering a portion of the catalyst put in contact with the initial alkane (s) in a production alkanes, (b) separating the portion of the catalyst thus collected and recovered, the alkanes and in particular the initial or unreacted alkanes and the alkanes produced, (c) contacting or activating the portion of the catalyst thus separated with hydrogen and optionally the in situ forming agent of hydrogen, (d) optionally separating from this or these the portion of the catalyst thus brought into contact or activated, at the end of the contacting or discontinuous activation, and (e) bringing the catalyst portion back into contact with the initial alkane (s) in the continuous manufacture of alkanes. 45. Process according to claim 37 or 38, characterized in that in a continuous production of alkanes, the catalyst is brought into contact with the hydrogen and optionally the in situ forming agent of hydrogen in a continuous manner. in the absence of or initial alkanes. 46. The method of claim 45, characterized in that it comprises the following successive steps, carried out in particular in a repetitive manner: (a) take and recover a portion of the catalyst contacted with the initial alkane (s) in a production alkanes, (b) separating the portion of the catalyst thus withdrawn and recovered, the alkanes and in particular the initial or unreacted alkanes and the alkanes produced, (c) adding and mixing the portion of the catalyst thus separated to a part of the catalyst in contact or continuously activated with hydrogen and optionally the in situ forming agent of hydrogen, (d) withdrawing and recovering a portion of the catalyst thus brought into contact or activated continuously, (e) separating optionally the portion of the catalyst thus collected and recovered, hydrogen and optionally the in situ hydrogen forming agent, and (f) contacting the portion of the catalyst with the initial alkane (s) in the continuous manufacture of alkanes. <Desc / Clms Page number 64> 47. Process according to any one of claims 1 to 36, characterized in that the contacting of the catalyst with hydrogen and optionally an in situ hydrogen forming agent is carried out in the presence of or initial alkanes, in a single zone. 48. The method of claim 47, characterized in that the single zone is a gas phase zone. 49. A method according to claim 48, characterized in that the single zone in the gas phase comprises a gaseous phase consisting essentially of the initial alkane (s), hydrogen, and optionally the in situ hydrogen forming agent, and optionally by one or more inert gases. 50. Process according to Claim 48 or 49, characterized in that the single zone in the gas phase comprises a reactor or a gas-phase loop, preferably chosen from the fluidized-bed and / or mechanically stirred reactors, the fixed-bed reactors. and circulating bed reactors, the bed consisting in particular essentially of the catalyst in a solid form. 51. Process according to any one of claims 48 to 50, characterized in that it comprises the following steps, preferably carried out continuously: (a) introducing the initial alkane or alkanes, hydrogen, optionally the agent forming in situ hydrogen and optionally one or more inert gases in the single zone in the gas phase containing the catalyst, so as to form a substantially gaseous stream passing through said zone, the stream preferably being recycled in said zone, (b) withdrawing out of said zone a portion of the stream having passed through said zone and containing the alkanes produced, (c) partially or completely separating the alkanes produced from or unreacted initial alkanes, hydrogen, or optionally forming in situ hydrogen, and optionally inert gas (s), <Desc / Clms Page number 65>  and (d) possibly returning to said zone and thus separated from the alkanes produced and which are thus in particular brought into contact with the catalyst. 52. Process according to claim 47, characterized in that the single zone is a zone in the liquid phase. 53. Process according to claim 52, characterized in that the single zone in the liquid phase comprises a liquid phase consisting essentially of the initial alkane (s) and optionally by one or more liquid inert agents, the liquid phase preferably being a suspension containing solid particles, in particular consisting essentially of the catalyst in a solid form. 54. Process according to claim 52 or 53, characterized in that the single zone in the liquid phase comprises a reactor or a loop in the liquid phase, preferably a reactor or a loop for suspension in the liquid phase. 55. Process according to any one of Claims 1 to 28 and 37 to 46, characterized in that the contacting of the catalyst with hydrogen and optionally an in situ forming agent of the catalyst is carried out separately. hydrogen and on the other hand with the initial alkane (s) in two distinct zones. 56. Process according to claim 55, characterized in that the two distinct zones are interconnected by a first catalyst transfer zone connecting the zone of contacting or activation of the catalyst with hydrogen to the reaction zone of the catalyst. production of alkanes, and a second catalyst transfer zone connecting the reaction zone for the production of alkanes to the zone of contacting or activation of the catalyst with hydrogen. <Desc / Clms Page number 66> 57. A method according to claim 56, characterized in that one of the two transfer zones or preferably the two transfer zones are implemented in discontinuous or, preferably, continuously. 58. The method of claim 56 or 57, characterized in that at least one of the two transfer zones comprises a pipe or elevator selected from the pipes and mechanical, hydraulic or pneumatic lifts. 59. The method of claim 58, characterized in that the transfer of the catalyst in a pipe or elevator, hydraulic or pneumatic, is achieved by a carrier fluid, especially a carrier liquid or a carrier gas, preferably selected from at least one of the liquid or gaseous components present in the zone where the transfer is directed. 60. Process according to any one of claims 56 to 59, characterized in that at least one of the two transfer zones is preceded by a zone separating partially or totally the catalyst from the other liquid or gaseous constituents, entrained with the catalyst out of the zone from which the catalyst originates, the other component (s) thus entrained and separated are preferably returned to the zone from which the catalyst originates. 61. Process according to any one of claims 55 to 60, characterized in that the production of alkanes is carried out in a reaction zone in the liquid phase. 62. Process according to claim 61, characterized in that the liquid phase reaction zone comprises a liquid phase consisting essentially of the initial alkane (s) and / or one or more liquid inert agents, the liquid phase preferably being a suspension containing solid particles, in particular essentially consisting of the catalyst in solid form. <Desc / Clms Page number 67>  63. Process according to claim 61 or 62, characterized in that the liquid phase reaction zone comprises a reactor or a loop in the liquid phase, or preferably a reactor or a loop for suspension in the liquid phase. 64. Process according to any one of claims 55 to 60, characterized in that the production of alkanes is carried out in a reaction zone in the gas phase. 65. The method of claim 64, characterized in that the gas phase reaction zone comprises a gaseous phase consisting essentially of the initial alkane (s) and optionally by one or more inert gases. 66. Process according to claim 64 or 65, characterized in that the gas phase reaction zone comprises a reactor or a gas-phase loop, preferably chosen from fluidized-bed and / or mechanically stirred reactors, fixed-bed reactors. and circulating bed reactors, the bed consisting in particular essentially of the catalyst in a solid form. 67. Process according to any one of claims 61 to 66, characterized in that the production of alkanes comprises the following steps, preferably carried out continuously: (a) introducing the initial alkane (s) into the reaction zone, (b) ) contacting the initial alkane (s) with the catalyst present or introduced in said zone, (c) withdrawing from said zone a portion of the alkanes produced, which with them leads to a portion of initial or unreacted alkanes, (d) partially or completely separating the portion of alkanes produced from the portion of initial or unreacted alkanes, and (e) returning preferably to said zone the portion thus separated from or from the initial alkanes not having reacted, which part is thus in particular brought into contact with the catalyst. 68. Process according to any one of Claims 55 to 67, characterized in that the activation of the catalyst carried out by placing the latter in contact with hydrogen <Desc / Clms Page number 68>  and optionally the in situ hydrogen forming agent is performed in a liquid phase activation zone. 69. Process according to claim 68, characterized in that the activation zone in the liquid phase comprises a liquid phase consisting essentially of at least one liquid inert agent, the liquid phase preferably being a suspension containing solid particles, in particular essentially consisting of by the catalyst in a solid form. 70. The method of claim 68 or 69, characterized in that the activation zone in the liquid phase comprises a reactor or a loop in the liquid phase, or preferably a reactor or a loop for suspension in the liquid phase. 71. Process according to any one of claims 55 to 67, characterized in that the activation of the catalyst carried out by placing the latter in contact with the hydrogen and optionally the in situ forming agent of hydrogen is carried out in an activation zone in the gas phase. 72. Process according to claim 71, characterized in that the gas phase activation zone comprises a gaseous phase consisting essentially of hydrogen, optionally by the in situ hydrogen forming agent and optionally by one or more inert gases. 73. Process according to claim 71 or 72, characterized in that the gas phase activation zone comprises a reactor or a gas phase loop, chosen in particular from fluidized-bed and / or mechanically stirred reactors, bed-type reactors. fixed and circulating bed reactors, the bed consisting in particular essentially of the catalyst in a solid form. <Desc / Clms Page number 69> 4. Method according to any one of claims 71 to 73, characterized in that it comprises the following steps, preferably carried out continuously: (a) introducing the catalyst into a gas phase activation zone traversed by a current hydrogen, and optionally hydrogen-forming agent, the stream being preferably recycled to said zone; (b) withdrawing and recovering from said zone a portion of the catalyst thus activated, carrying with it a portion of hydrogen and optionally the agent, (c) optionally partially or completely separate the portion thus withdrawn and recovered from the catalyst, the part of the hydrogen and optionally the agent thus entrained, withdrawn and recovered, and (d) ) return preferably in said zone the part of the hydrogen and optionally of the thus separated agent, which part is thus in particular brought into contact with the catalyst.