MXPA96002553A - Alifatic alkaly procedure in reverse emulsion with premix catalyst-olef - Google Patents

Abstract

The invention relates to an alkylation process of at least one isoparaffin selected from the group consisting of isobutane and isopentane by at least one olefin comprising from 2 to 6 carbon atoms per molecule in the presence of a liquid acid catalyst, said process comprises mixing in a mixed first zone of the charge comprising the olefin to be converted and of an effluent comprising mostly isoparaffin, as well as the formation in an emulsion zone of an emulsion of said catalyst in a hydrocarbon effluent which It comprises for the most part isoparaffin, said effluent constitutes the continuous phase of the emulsion so formed, then the mixing or mixing in a second mixed zone of most of the emulsion of the acid in the hydrocarbon effluent and most of the the dilute charge comprising the olefin, followed by the implementation of most of the reaction in a reaction zone which is fed in most of said mixture or mixture

Description

- ALIFATIC ALKALY PROCEDURE IN REVERSE EMULSION WITH PREMIX CATALYST-OLEFIN FIELD OF THE INVENTION The present invention relates to a process for the catalytic alkylation of at least one isoparaffin selected from the group consisting of iso-1-butane and isopentane by at least one olefin comprising from 2 to 6, preferably from 3 to 6 carbon atoms per molecule, in the presence of at least one liquid acid catalyst.

BACKGROUND OF THE INVENTION The alkylation of isoparaffin (isobutane and / or isopentane) by at least one olefin containing from 2 to 6, preferably from 3 to 6 carbon atoms per molecule, makes it possible to obtain paraffinic hydrocarbons strongly branched (for example belonging to the groups consisting of dimethylbutanes, trimethylpentanes, trimethylhexanes and trimethyl-heptanes), essential constituents of high octane fuel. This reaction of alqui¬ called aliphatic, needs the use of REF: 22667 • highly acidic catalysts, mainly to reduce parasitic reactions such as olefin hydride and polymerization abstraction reactions that provide low branched hydrocarbons with low octane number and unsaturated hydrocarbons, catalytic thermofraction reactions and dismutation reactions. A large number of acidic catalysts, liquid or solid, are known to make the alki¬ aliphatic portion of isoparaffin (s) such as isobutane or isopentane, by at least one olefin such as propylene, 1- and 2-butenes, isobutene. The catalysts most commonly used in industrial practice are liquid catalysts which are the concentrated sulfuric acid and the hydrofluoric acid alone or in mixture with the Lewis acids such as boron trifluoride. ^ Ét Most of the conventional procedures are, in particular, characterized because the phase Acid constitutes the continuous phase of the acid-hydrocarbon emulsion formed within the reactor. The ratio or proportion of the volumes of acid and hydrocarbons (mixture of isoparaffins and olefins) is thus greater than 1. In addition, the emulsion is made generally within the same alkylation reactor, ie in the presence of the charge to be converted which contains the olefin (see for example in the case of the implementation of Stratco technology employing liquid sulfuric acid: LF Albright, Chem Eng., August 15, 1966, p.143 and LF Albright, Oil &Gas Journal, November 12, 1990). In the case where the sulfuric acid is the catalyst, the conventional process of alkylation of isoparaffins with sulfuric acid as catalyst has numerous drawbacks, among which the following can be mentioned: the impossibility of reaching temperatures below 0 ° C in the reactor in the presence of of sulfuric acid of title or quality greater than 97% by weight. In fact, the viscosity of sulfuric acid becomes higher at such temperatures and, the acid is the continuous phase, the medium becomes inactive. - • The olefin in the charge and the recirculated acid in the decanter are injected directly into the reactor in the immediate vicinity of the stirring device. The latter must then perform two operations: create the acid-hydrocarbon emulsion and assure the dilution of the olefin in the hydrocarbon phase in such a way as to limit the local overconcentrations in said olefin, which is not carried out sufficiently efficiently. the residence time of the hydrocarbon phase in the decanter is important, most of the time close to 1 hour. The temperature in said decanter is most often greater than about 15 ° C, then degradation reactions of isoparaffins having more than 5 carbon atoms per molecule occur. Between these degradation reactions, the oxidation reactions of the paraffins can be cited by sulfuric acid, which produce water and SO_. These reactions contribute to the deactivation of the catalyst. The uncontrolled decomposition reactions of the alkyl sulphates and in particular of the butyl sulphates can also be mentioned. These decomposition reactions are the origin of the formation of unsaturated oligomers that deactivate the catalyst. PCT patent application WO 95/04199 discloses a process for the alkylation of an olefin by an isoparaffin in the presence of liquid sulfuric acid, the process comprising a zone for preparing an emulsion of the acid in the isoparaffin followed by a reaction zone fed to the isoparaffin. by said emulsion in which the olefin is injected, the volumic or volume ratio sulfuric acid: hydrocarbons present in the reaction zone, is comprised between 0.3: 1 and 0.5 and 1. Thus the continuous phase of the emulsion prepared in said process is the hydrocarbon phase. Said patent application also describes the means of realization of the emulsion and the supply of olefin in the reaction zone as well as the equipment for the implementation of the process. In the PCT patent application WO 95/04199, the olefin is injected directly into the reaction zone. This area must thus ensure the dilution of the olefin in the hydrocarbon phase in such a way that limi¬ local overconcentrations in said olefin. Now, the alkylation reaction of iso- ^ Ofc. butane and / or isopentane comprises a very rapid first stage of adoption or approval of the olefin in the ca¬ Acidicizer, which allows the formation of an acid-olefin "complex" exit, followed by a reaction step of said "complex" with isobutane and / or isopentane. And said first stage, if it is conducted under the reaction conditions of Pressure and temperature may favor the formation II of polymers, unwanted by-products, to the detriment of the formation of said "complex". This is very penalized in terms of the performance of the procedure. It is thus interesting to proceed with a mixture of the olefin and the catalyst in an area that precedes the reaction zone, under the conditions of temperature and pressure that favor mainly the formation of the "complex". t? DESCRIPTION OF THE INVENTION The process according to the invention is therefore an alkylation process of at least one isoparaffin selected from the group formed by isobutane and isopentane, preferably isobutane, by at least one olefin comprising from 2 to 6, preferably from 3 to 6 carbon atoms per molecule, in the presence of an acidic, liquid catalyst, said process comprises mix in a first mixed zone of the cargo they buy from the olefin to be converted and an effluent comprising mostly of the isoparaffin, which allows the obtaining of a diluted load comprising the olefin, as well as the formation in an area of emulsion of an emulsion of said catalyst in a hydrocarbon effluent comprising mostly isoparaffin, said effluent constitutes the continuous phase of the emulsion thus formed, then the mixing in a mixed second zone of most of the emulsion of the acid in the hydrocarbon effluent and most of the diluted charge comprising the olefin, followed by the implementation of most of the reaction in a reaction zone that is fed into most of said mixture. * The operations of the first mixing and of emulsion formation, can take place simultaneously or not, the order of said operations matters little when they are carried out successively. According to a preferred embodiment according to the invention, the method according to the invention also comprises the step of # most of the effluent from the reaction zone in a settling area, which allows obtaining of an effluent comprising mostly liquid acid and a hydrocarbon phase comprising mainly isoparaffin and alkylate. In such a case, according to a first option, said method is preferably such as the catalyst which feeds the emulsion zone, comprises the greater part of the effluent which comprises, for the most part, the liquid acid leaving said decantation zone. According to a second option, independent or not of the preceding one, the effluent, which mostly comprises the isoparaffin entering the first mixed zone, comprises for the most part part of said hydrocarbon phase. According to the preferred embodiment described above, and independently or not of IO each of the options described above, said process can, preferably, also comprise a separation zone that allows obtaining a hydrocarbon effluent containing mostly isoparaffin and obtaining a alkylate, product of the reaction, said reaction zone is fed by a part of the hydrocarbon phase obtained at the exit from the de¬ # singing It is then possible for the method according to the invention to be such that the other Part of said hydrocarbon phase obtained at the outlet of the decantation zone is comprised in the effluent which comprises, for the most part, the isoparaffin which enters the zone of the first mixture or of the first mixture. Another possibility, independent or not of The foregoing possibility is that the process according to the invention, such as the hydrocarbon effluent which comprises for the most part the isoparaffin which feeds the emulsion zone, comprises for the most part of the hydrocarbon effluent it contains in its most of the isoparaffin that leaves the separation zone. In addition, the process according to the invention comprises a contribution of isoparaffin. This contribution of isoparaffin constitutes the food The procedure of the invention according to the invention with isoparaffin, which is made with stoichiometry of the alkylation reaction in relation to the olefin. Preferably, the method according to the invention is such that the contribution of Isoparaffin is made by mixing or mixing the iso-paraffin that is provided in the charge comprising the olefin to be converted before the entrance of said load HE in area of the first mix. Thus, more preferably, the load that enters the area of the first The mixture comprises mainly the feeding of the process with olefin (s) and with isoparaffin (s). The process according to the invention generally comprises a fresh or fresh catalyst feed, ie catalyst that has not yet undergone any chemical reaction that is either catalyst that has undergone any chemical reaction and has been regenerated in a regeneration zone in order to restore its initial catalytic properties, and a used catalyst transfer . Preferably, the fresh catalyst input comprises for the most part of the catalyst leaving a regeneration zone. The process according to the invention is such that the acidic, liquid catalyst is generally chosen from the group consisting of sulfuric acid and hydrofluoric acid, and preferably said acid, liquid catalyst is sulfuric acid, which preferred way is of quality or title greater than 96% by weight. The liquid sulfuric acid used according to the invention in the reaction zone at a temperature generally lower than 0 ° C, has the advantage over sulfuric acid of title or quality of 96 to 99% by weight, currently used in the units of alkylation (in the conventional processes and operating in the reaction zone at a temperature generally higher than 0 ° C), of having an acidity higher or equal having a much lower oxidant character, and thus obtaining an alkylate of which the octane number is superior to what is commonly obtained with said conventional processes. The use of said catalyst according to the invention thus leads to a reduction in the consumption of the catalyst and then to a reduction in costs of the alkylation units. But the process of the present invention is applied to any liquid acid catalyst, such as for example a catalyst comprising at least one acid selected from the group consisting of sulfuric acid and hydrofluoric acid, to which at least one additive such as for example the compound HB (HS0.) .. For example, the catalyst used according to the process of the present invention, comprises (in% by weight) between 0.4 and 68.8%, preferably between 0.4 and 60% , of the compound HB (HS04). and between 31.2 and 99.6%, preferably between 40 and 99.6%, of the compound H_S0., said catalyst is such that it does not contain sulfuric anhydride (SO-,) not associated, that is, it does not react with boric acid but can eventually contain boric acid, in excess, not associated, that is to say, it does not react with sulfuric anhydride. The process according to the present invention, more particularly in its preferred embodiment, which comprises the passage of most of the effluent from the reaction zone in a decantation zone, presents numerous advantages in relation to the processes of alkylation known in the prior art, among which we can mention: the use of a low reaction temperature, in particular lower than 0 ° C, the obtaining of decanting speeds much greater than those obtained when the acid phase is the continuous phase of the emulsion, the use of a mixing or mixing temperature of the olefin and the acid catalyst, liquid, very low, and mainly lower than the temperature of the reaction zone, in particular lower than 0 ° C, carrying out the operation of Decanting at a low temperature favors the addition of a short residence time in said decantation zone, which considerably limits the importance of secondary reactions that are manifested in the decanters of conventional processes. Thus, a preferred embodiment according to the invention relates to an alkylation process in which a charge is treated comprising, on the one hand, at least one isoparaffin selected from the group consisting of isobutane and isopentane, Preferably the isobutane and on the other hand at least one olefin containing from 2 to 6, preferably from 3 to 6 carbon atoms per molecule, in the presence of an acid, liquid catalyst, said process is such that it itself comprises the following steps: (1) the realization in an area (E) of the emulsion of most of the liquid acid coming from a settling zone (D) described in step (5) and most of the hydrocarbon effluent which comprises for the most part of the isoparaffin coming from the isoparaffin-alkylate (S) separation zone described in step (6), said greater part of such effluent constitutes the continuous phase of said emulsion. The effluent from zone (E) is an acid emulsion in a hydrocarbon liquid effluent comprising mostly isoparaffin. This emulsion is constituted by fine droplets of acid despersas in a continuous hydrocarbon phase. (2) mixing or mixing in a mixed first zone (M1) of the charge and a part of the hydrocarbon phase comprising mainly the isoparaffin and the alkylate leaving the decantation zone (D) described in step (5), which allows obtaining a diluted load. The steps (1) and (2) are performed at least in part simultaneously or successively, in which case the order of carrying out said steps intervenes little. (3) mixing or mixing in a mixed second zone (M2) of said diluted filler described in step (2) and said emulsion described in step (1), which allows obtaining a mixture of acid in a hydrocarbon liquid effluent which is the continuous phase of the emulsion. (4) the realization in a zone (R) of most . of the alkylation reaction, the zone (R) is fed by most of the mixing leaving the zone (M2) described in step (3), preferably introduced at least at the entrance of the zone (R). The efficiency of the effluent entering the reaction zone (R) is chosen in such a way that the emulsion present in said zone is constituted by the dispersed acid droplets in a continuous hydrocarbon phase.

E ~ (5) the separation in a settling zone (D) of most of the effluent leaving the reaction zone (R) described in step (4). Said effluent is constituted by an emulsion of acid in a continuous hydrocarbon phase. In the decantation zone (D) the separation of the two acid and hydrocarbon phases takes place. The settling zone (D) generally comprises at least one decanter. The type of decanter used is chosen in such a way that the time necessary to carry out the decanting operation is as small as possible, and that the temperature of the acid phase in said decanter is lower than 0 ° C. The settling zone (D) allows the obtaining of an effluent comprising mostly of the liquid acid, most of said effluent is recirculated to the emulsion zone (E) described in step (1), and obtaining of a hydrocarbon phase comprising mainly isoparaffin and alkylate, of which a part is recirculated into the zone of the first mixed or first mixture (M1) described in step (2). (6) the isoparaffin-alkylate separation in a zone (S) of the other part of the hydrocarbon liquid phase comprising mainly the iso-paraffin and the alkylate leaving the decantation zone (D) described in step (5), with the object of obtaining a hydrocarbon effluent comprising for the most part isoparaffin and from which most of it is recirculated in the zone (E) described in step (1), optionally and preferably a hydrocarbon effluent comprising most of it for normal fine, obtained as a purge, and a hydrocarbon effluent comprising mostly alkylate, as a product. In the process of alkylating isoparaffin (s) by at least one olefin according to the present invention, the operating conditions, and more particularly temperature and pressure, are chosen in such a way that the reaction mixture is liquid. . In carrying out the process according to the invention, the realization of mixtures or mixtures in the zone (M1) and in the zone (M2) can be done according to various techniques known to the person skilled in the art. For example, it is possible to use at least one static mixer in line (containing Sulzer fittings or accessories for example). In all the cases of the figure, it is particularly advantageous to use static mixers above the reaction zone (R) so as to ensure the greatest possible contact between the different effluents before their introduction into the reaction zone (R). The efficiency of the effluent entering the reaction zone (R) is chosen in such a way that the emulsion present in the entire reaction zone (R) is constituted by droplets of acid dispersed in a continuous hydrocarbon phase. One or several reactors can be used for the implementation of the method according to the invention. In a preferred embodiment in accordance with the invention, the effluent, which comprises mostly of the catalyst below the decantation zone (D), is continuously or discontinuously introduced and is introduced continuously or discontinuously from the catalyst. fresh or recent catalyst, at the entrance of the emulsion zone (E) to maintain at a constant level the quality of the alkylate produced. The temperature in the emulsion zone (E) is generally between -20 and + 10 ° C, preferably between -10 and + 10 ° C, and the pressure is such that any hydrocarbon present in said zone is liquid. ^ l. The temperature in the zone of the second mixed or second mixture (M2) is generally between -20 and +10 ° C, preferably between -15 and 0 ° C, still more preferably between -10 and -3 ° C, and the pressure is such that all hydrocarbons present in said zone are liquid. The temperature in the alkylation zone or reaction zone (R) is generally between -20 and + 10 ° C, preferably between -10 and + 5 ° C, and Even more preferred way comprised between -10 and 0 ° C, and the pressure is such that any hydrocarbon present in said zone is liquid. The temperature in the decantation zone (D) is generally between -20 t + 10 ° C, preferably is between -10 and + 5 ° C, and still more preferably between -10 and 0 ° C, and the pressure is such that any hydrocarbon present in said zone is liquid. The residence time of the compounds in The zone of the second mixture or mixture (M2) is very short, generally between 1 second and 2 minutes, preferably between 1 second and 1 minute, in such a way that the alkylation reaction can not be produced in a very important way in the zone (M2). However, 5 it is considered that only most of the reaction ^ fl ?. occurs in the area (R). The residence time of the effluent from the reaction zone (R) in the decantation zone (D) is very short, shorter than for conventional alkylation processes for which the continuous phase of the isoparaffin-acid emulsion is the acid. It is generally comprised between 1 minute and 1 hour, preferably between 1 minute and 30 minutes, and in a frequently preferred manner between 1 and 5 minutes. The residence time of the catalyst in the emulsion zone (E) is generally between 1 second and 20 minutes, preferably between 1 according to day and 10 minutes. The residence time of the compounds, and more particularly of the catalyst, in the reaction zone (R) is generally between 1 minute # to and 1 hour, preferably between 1 minute and 30 minutes. The ratio of the volumetric effluents of the effluent, which mostly comprises the acid coming from the lower part of the decantation zone (D) and the hydrocarbon effluent, which comprises, for the most part, the isoparaffin which comes from the head or upper part of the separation zone (S), at the entrance of the emulsion zone (E), is chosen in such a way that the volume or volume ratio of acid in said emulsion zone is between 5 and 49 %, preferably between 10 and 45% and more preferably between 30 and 45%. The volumetric proportion of acid within the reaction zone (R) is between 20 and 49%, preferably between 30 and 45%. Preferably, the filler is dried on a molecular sieve t10 and selectively hydrogenated prior to its introduction into the zone of the first mixture (M1), so as to eliminate very strongly unsaturated compounds capable of inhibiting the catalytic phase. 15 In general, the space velocity per hour, expressed in volumes of olefin (s) introduced per volume unit of the pre¬ catalyst »In the zone (R) and per hour, it is comprised between 0.1 and 5 h -1, preferably between 0.2 and 2 h-1 To limit the secondary degradation reactions of the C8-C isoparaffins present in the liquid effluent passing through the reaction zone (R), the separation operation (zone (S)) of said so that the ratio of the mass or mass yields of the hydrocarbon effluent, which mostly comprises isoparaffin (for example isobutane) leaving the head or upper part of the separation zone (S) and the hydrocarbon effluent, which comprises mostly part of the alkylate leaving the bottom of the zone (S), is between 5: 1 and 100: 1, and preferably between 10: 1 and 30: 1. The appended figure illustrates the invention, and more precisely one of the preferred implementations of the method according to the invention, without limiting the scope of the same. The charge to be converted constituted by the liquid phase mixture of line (1), which comprises at least one isoparaffin and at least one olefin containing from 2 to 6 carbon atoms per molecule, is mixed with the effluent of the line ( 2), isoparaffin and alkylate mixture that comes from a part of the effluent (9) that comes out of the decanter (D) which is not sent to the separation zone (S). The lines (1) and (2) mixed thus form the line (3) that feeds the static mixer (M1). The effluent leaving (M1) is injected, then mixed with the effluent from the line (5) in a second static mixer (M2). The effluent from line (5) consists of an emulsion of acid in the isoparaffin, isoparaffin that comes from the head or upper part of the separation zone (S) through line (12) and the acid that comes from it. from the bottom of the decantation zone (D) along the line (11). The effluent leaving the mixer (M2), consisting of an emulsion in continuous hydrocarbon phase, is introduced by the line (7) in the reaction zone (R). The effluent leaving the reaction zone (R), that is to say the emulsion of acid in a hydrocarbon-based phase, consisting mainly of isoparaffin and alkylate, is introduced into a settling zone (D). The lower part of the zone (D) is crossed, by the line (11), the acid, which after mixing with the effluent (isoparaffin) of the line (12), is introduced at the entrance of a zone (E). ). From the upper part of the decantation zone (D) a hydrocarbon phase containing the excess isoparaffin and the alkylate is transferred through line (9). A part of this effluent is recirculated by the line (2) at the entrance of the first static mixer (M1) and the other part is introduced in a separation zone (S) isoparaffin-paraffin Ñor-mal-alkylate. The alkylate separated in the zone (S) is extracted from the unit as a product by line (13). Normal paraffin is extracted <; S laterally from the area (S) by the line (15) as purging or purging. The liquid fraction rich in isoparaffin extracted in the head or upper part of the zone (S) is recirculated towards the entrance of the emulsion zone (E) by line (12).

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention is that which is clear from the present description of the invention. Having described the invention as above, the content of the following is claimed as property fifteen fr twenty

Claims (10)

1. An alkylation process of at least one isoparaffin selected from the group consisting of isobutane and isopentane by at least one olefin comprising from 2 to 6 carbon atoms per molecule in the presence of an acidic, liquid catalyst, such a process is characterized in that it comprises the mixing or mixing in a first mixing zone of the load comprising the olefin to be converted and an effluent comprising mostly isoparaffin, which allows obtaining a diluted load comprising the olefin, as well as as the formation in an emulsion zone of an emulsion of said catalyst in a hydrocarbon effluent comprising mostly isoparaffin, said effluent constitutes the continuous phase of the emulsion thus formed, then mixing in a mixed second zone or second mixture of most of the acid emulsion in the hydrocarbon effluent and most of the diluted cargo comprising the olefin a, followed by the implementation of most of the reaction in a reaction zone that is fed in most of such mixing or mixing.

2. The process according to claim 1, characterized in that it also comprises the passage of most of the effluent from the reaction zone in a decantation zone, which allows the obtaining of an effluent comprising in its most of the liquid acid and a hydrocarbon phase comprising mainly isoparaffin and alkylate.

3. The method according to claim 2, characterized in that the catalyst that feeds the emulsion zone comprises the greater part of the effluent, which comprises, for the most part, the liquid acid leaving said zone of de¬ 15 singing

4. The process according to one of claims 2 to 3, characterized in that the effluent comprising mostly of the isoparaffin 20 na that enters the first mixed zone, comprises for the most part a part of said hydrocarbon phase.

5. The process according to one of claims 2 to 4, characterized in that it also comprises a separation zone which allows ^ | f to obtain a hydrocarbon effluent containing mostly isoparaffin and obtaining an alkylate, product of the reaction, said separation zone is fed by a portion of the hydrocarbon phase obtained at the outlet of the decantation zone.

6. The procedure in accordance with the. claim 5, characterized in that the hydrocarbon-based effluent, which comprises for the most part the isoparaffin which feeds the emulsion zone, comprises for the most part the hydrocarbon effluent which contains for the most part the isoparaffin leaving the separation zone.

7. The process according to claims 1 to 6, characterized in that it comprises a contribution of isoparaffin.

8. The process according to claim 1, characterized in that it comprises a fresh or fresh catalyst feed and a used catalyst transfer. 5 JP

9. The process according to one of claims 1 to 8, characterized in that said liquid acid catalyst is chosen from the group consisting of sulfuric acid and hydrofluoric acid.

10. The process according to one of claims 1 to 9, characterized in that said liquid acid catalyst is sulfuric acid. 5 0 5