Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G65/00—Treatment of hydrocarbon oils by two or more hydrotreatment processes only
  • C10G65/02—Treatment of hydrocarbon oils by two or more hydrotreatment processes only plural serial stages only
  • C10G65/04—Treatment of hydrocarbon oils by two or more hydrotreatment processes only plural serial stages only including only refining steps

Definitions

• the present invention relates to a process for the production of hydrocarbons with low sulfur content.
• This fraction of hydrocarbons contains a fraction of olefins generally greater than 5% by weight and most often greater than 10% by weight.
• the process allows in particular to recover the entire petrol cut containing sulfur by reducing the sulfur and mercaptan contents of said gasoline cut to very low levels, without reducing the fuel yield, and minimizing the decrease in octane number during said process.
• the invention finds particularly its application when the essence to be treated is an essence of catalytic cracking containing a sulfur content greater than 500 ppm by weight or even greater than 1000 ppm by weight or even 2000 ppm by weight, and when the content of sulfur sought in desulphurized petrol is less than 50 ppm by weight, or even 20 ppm weight or even 10 ppm weight.
• the main sources of sulfur in gasoline bases are gasolines said to be cracked, and mainly, the fraction of gasoline resulting from a catalytic cracking of a residue from atmospheric or vacuum distillation of a crude oil.
• the gasoline fraction from catalytic cracking which represents average 40% of petrol bases, in fact contributes more than 90% to the contribution of sulfur in the essences. Consequently, the production of low sulfur species requires a step of desulfurization of catalytic cracked gasolines. This desulfurization is conventionally carried out by one or more stages of contact of the sulfur compounds contained in said gasolines with a gas rich in hydrogen in a process known as hydrodesulfurization.
• octane number of such gasolines is very strongly linked to their content of olefins. Preserving the octane number of these species therefore requires limiting reactions for the transformation of olefins into paraffins which are inherent in hydrodesulfurization processes.
• the essences have corrosive properties due to the presence of mercaptans.
• the mercaptans measured in desulfurized gasolines are so-called recombination mercaptans, that is to say derived from the addition reaction of hydrogen sulfide (H 2 S) produced during the desulfurization step and the olefins present in l petrol.
• the solution usually used to eliminate these mercaptans consists in hydrogenating the olefins present in gasoline. However, for the reasons already described, this hydrogenation causes a loss of unacceptable octane on the catalytic cracking gasolines.
• the treatment of gasoline rich in sulfur in order to finally reach sulfur contents lower than 50 ppm, even 20 ppm or even 10 ppm, can optionally and preferably requiring the implementation of a process comprising hydrodesulfurization in at least two hydrodesulfurization reactors in series, and an intermediate elimination of the H 2 S formed during the first hydrodesulfurization step.
• This type of scheme is preferably intended to achieve high rates of desulphurization, for example rates of 99% to bring a gasoline having sulfur concentrations of the order of 2000 ppm to sulfur concentrations of the order of 10 ppm.
• patent EP 0755995 proposes a scheme consisting of at least two hydrodesulfurization steps and a step of removing H 2 S between two hydrodesulfurization reactors.
• the hydrodesulfurization rate must be between 60% and 90% at each stage.
• such a process does not make it possible to envisage reaching desulfurization rates greater than 99% on an industrial scale.
• US patent 6,231,753 proposes the treatment of highly sulfuric gasolines by a scheme also comprising 2 hydrodesulfurization steps and an intermediate elimination of the H 2 S formed.
• the operating conditions are such that the desulfurization rate and temperature of the essences of the second hydrodesulfurization step are higher than those of the first step.
• the present desulfurization process offers a solution to achieve high desulfurization rate, typically greater than 95% and more specifically greater 99%, while limiting the loss of octane by hydrogenation of olefins, as well as the formation of recombinant mercaptans. This results in the production of a gasoline low in sulfur and mercaptans and with a high octane number.
• At least one of the catalysts hydrodesulfurization includes at least one element from group VIII of the classification periodically and more preferably at least one of the catalysts comprises in in addition to at least one element of group VIB of the periodic table.
• said hydrodesulfurization catalysts comprise at least minus one element from group VIII of the classification chosen from the group consisting of nickel and cobalt and at least one element from group VIB of the classification chosen from the group consisting of molybdenum and tungsten.
• the first desulfurization of the process according to the invention is carried out at a temperature between 250 ° C and 350 ° C, under a pressure between 1 and 3MPa, at a liquid hourly space velocity between 1h -1 and 10h - 1 and with an H 2 / HC ratio of between 50 l / l and 500 l / l and preferably the second desulfurization is carried out at a temperature between 200 ° C and 300 ° C, under a pressure between 1 and 3 MPa, at a liquid hourly space velocity between 1h -1 and 10h -1 and with an H 2 / HC ratio between 50 l / l and 500 l / l.
• the desulfurization rate of the second desulfurization is strictly more than 80% and more preferably, the difference between the desulphurization of the first and second desulphurization is at least one for hundred in absolute value.
• a difference can be obtained in particular thanks to a difference in temperature and / or hourly space velocity between the first and the second desulfurization, and / or via a catalytic activity different from the catalysts used in the first and second hydrodesulfurization stage, for example in because of a difference in the composition or preparation of these catalysts.
• the method according to the invention is preferably applied to fillers such as gasoline cuts from catalytic cracking or coking of a charge heavy hydrocarbon or steam cracking.
• the charge to be desulfurized is optionally treated beforehand in a sequence of reactors for the selective hydrogenation of diolefins (step a) and weighing down the light sulfur compounds (step b).
• the charge thus pretreated is then distilled and fractionated into at least two cuts (step c): a light essence low in sulfur and rich in olefins and a heavy gasoline rich in sulfur and depleted in olefins.
• the light fraction from the previous three steps contains generally less than 50 ppm of sulfur, preferably less than 20 ppm of sulfur, and very preferably, less than 10 ppm of sulfur, and does not require generally no further treatment before its incorporation as a petrol base.
• This optional step of pretreatment of the gasoline to be desulfurized is intended for at least partially eliminate the diolefins present in the gasoline.
• the hydrogenation of dienes is an optional but advantageous step, which allows to eliminate practically all of the dienes present in the cut to be treated before hydrotreating.
• Diolefins are precursors of gums which polymerize in hydrotreatment reactors and limit their lifespan.
• This step generally takes place in the presence of a catalyst comprising at least one metal from group VIII, preferably chosen from the group formed by platinum, palladium and nickel, and a support.
• a catalyst comprising at least one metal from group VIII, preferably chosen from the group formed by platinum, palladium and nickel, and a support.
• a catalyst containing 1 to 20% by weight of nickel deposited on an inert support such as, for example, alumina, silica, silica-alumina, a nickel aluminate or a support containing at least 50% alumina.
• This catalyst generally operates under a pressure of 0.4 to 5 MPa, at a temperature of 50 to 250 ° C, with an hourly space velocity of the liquid from 1 h -1 to 10 h -1 .
• Another metal of group Vlb can be combined to form a bimetallic catalyst, such as for example molybdenum or tungsten.
• This group Vlb metal if it is associated with the group VIII metal, will be deposited at a level of 1% by weight to 20% by weight on the support.
• the choice of operating conditions is particularly important. We will operate the most generally under pressure in the presence of a small amount of hydrogen compared to the stoichiometric value necessary to hydrogenate the diolefins.
• the hydrogen and the charge to be treated are injected in ascending or descending currents in a reactor preferably with a fixed bed of catalyst.
• the temperature is included on more generally between 50 and 300 ° C, and preferably between 80 and 250 ° C, so more preferred between 120 and 210 ° C.
• the pressure is chosen as sufficient to maintain more than 80%, and preferably more than 95%, by weight of the gasoline to be treated in the liquid phase in the reactor; it is most generally from 0.4 to 5 MPa and preferably greater than 1 MPa.
• Advantageous pressure is between 1 to 4 MPa, limits included.
• the space speed is, in these conditions of the order of 1 to 12 h -1 , preferably of the order of 4 to 10 h -1 .
• the light fraction of the gasoline catalytic cracking cut can contain up to a few% by weight of diolefins.
• the content of diolefins is reduced to less than 3000 ppm or even less than 2500 ppm and better still to less than 1500 ppm. In some cases, a dien content of less than 500 ppm can be obtained.
• the content of dienes after selective hydrogenation can even be reduced in some cases below 250 ppm.
• the hydrogenation step of the dienes is takes place in a catalytic hydrogenation reactor which comprises at least one zone catalytic reaction generally traversed by the entire charge and by the quantity of hydrogen necessary to carry out the desired reactions.
• This optional step consists in transforming the light saturated sulfur compounds, that is to say the compounds whose boiling point is lower than that of thiophene, into saturated sulfur compounds whose boiling point is above this thiophene.
• These light sulfur compounds are typically mercaptans of 1 to 5 carbon atoms, CS 2 and sulfides comprising of 2 to 4 carbon atoms.
• This transformation is preferably carried out on a catalyst comprising at least one element from group VIII (groups 8, 9 and 10 of the new periodic classification) on a support of alumina, silica or silica alumina or nickel aluminate type.
• the choice of catalyst is made in particular so as to promote the reaction between light mercaptans and olefins, which leads to mercaptans or sulphides with boiling temperatures higher than thiophene.
• This optional step can possibly be carried out at the same time as the step a), on the same catalyst.
• it can be particularly advantageous to operate, during the hydrogenation of the diolefins, under conditions such that at least part of the compounds in the form of mercaptans are transformed.
• the temperatures are generally between 100 and 300 ° C and preferably between 150 and 250 ° C.
• the H 2 / charge ratio is adjusted between 1 and 20 liters per liter, preferably between 3 and 15 liters per liter.
• the space velocity is generally between 1 and 10 h -1, preferably between 2 and 6 h -1 and the pressure between 0.5 and 5 MPa, preferably between 1 and 3 MPa.
• This separation is preferably carried out by means of a distillation column classic.
• This fractionation column must make it possible to separate a fraction light petrol containing a small fraction of sulfur and a heavy fraction preferably containing most of the sulfur initially present in the original essence.
• Light petrol obtained after separation generally contains at least the set of olefins with five carbon atoms, preferably the compounds with five carbon atoms and at least 20% of olefins with six carbon atoms.
• this light fraction obtained after steps a) and b) has a low sulfur, i.e. it is not generally necessary to treat the light cut before using as fuel.
• the gasoline treated by means of the variant of the process according to the invention which is described below is a cracking gasoline obtained directly from the cracking unit or pretreated according to at least one of steps a), b) or c) described above.
• the process according to the invention comprises two stages d) and f) of desulfurization carried out in two distinct reaction zones, as well as a step e) of separation of H 2 S between the two hydrodesulfurization zones.
• the first hydrodesulfurization step (step d) consists in passing the gasoline to be treated in the presence of hydrogen, over a hydrodesulfurization catalyst, at a temperature between 250 ° C and 350 ° C, preferably between 270 ° C and 320 ° C and at a pressure between 1 and 3 MPa, preferably between 1.5 and 2.5 MPa.
• the liquid space velocity is generally between 1 h -1 and 10 h -1 , preferably between 2 h -1 and 5 h -1
• the H 2 / HC ratio is between 50 liters / liter (l / l) and 500 l / l, preferably between 100 l / l and 400 l / l, and more preferably between 150 l / l and 300 l / l.
• the H 2 / HC ratio is the ratio between the flow of hydrogen under 1 atmosphere and 0 ° C. and the flow of hydrocarbon. Under these conditions, the reaction takes place in the gas phase.
• the desulfurization rate reached during this stage is strictly greater than 90%, that is to say for example, that a gasoline initially containing 2000 ppm of sulfur will be transformed into a gasoline containing less than 200 ppm of sulfur.
• the operating conditions during this step are therefore adjusted as a function of the characteristics of the feed to be treated in order to reach a desulfurization rate strictly greater than 90%, preferably greater than 92% and very preferably greater than 94%.
• the effluents from this first hydrodesulfurization step are partially desulfurized gasoline, residual hydrogen and H 2 S produced by decomposition of sulfur compounds.
• step e This step is followed by a separation step (step e) of most of the H 2 S from the other effluents.
• This step is intended to remove at least 80% and preferably at least 90% of the H 2 S produced during step d).
• the elimination of H 2 S can be carried out in various ways, for the most part known to those skilled in the art. Mention may be made, for example, of the absorption of H 2 S by a mass of metal oxide, preferably chosen from the group consisting of zinc oxide, copper oxide or molybdenum oxide.
• This absorbent mass is preferably regenerable and can be regenerated continuously or discontinuously by means, for example of a heat treatment under an oxidizing or reducing atmosphere.
• the adsorbent mass can be used in a fixed bed or a moving bed.
• Another more conventional method consists in cooling the effluent from step d) to produce a liquid and a gas rich in H 2 and H 2 S.
• H 2 S can be separated from H 2 by means of an amine washing unit whose operation is well known to those skilled in the art.
• a second desulfurization step f) is intended to carry out a deep desulfurization of the gasoline resulting from step e) up to the desired sulfur content.
• This step consists in passing over a hydrodesulfurization catalyst, the gasoline resulting from step e) in mixture with hydrogen at a temperature between 200 ° C and 300 ° C, preferably between 240 ° C and 290 ° C, at a pressure between 1 and 3 MPa, preferably between 1.5 and 2.5 MPa.
• the liquid space velocity is generally between 1 h -1 and 10 h -1 , preferably between 2 h -1 and 8 h -1
• the H 2 / HC ratio is between 50 liters / liter (l / l) and 500 l / l, preferably between 100 l / l and 400 l / l, and more preferably between 150 l / l and 300 l / l.
• the reaction takes place in the gas phase.
• the mixture of gasoline and hydrogen treated during this stage contains less than 100 ppm of H 2 S and preferably less than 50 ppm of H 2 S.
• the operating conditions of this stage are such that the rate of desulfurization achieves the required sulfur content, while maintaining a desulfurization rate lower than that of the first step.
• the charge to be treated during this stage is much less sulfurous than the initial charge, and the desired desulfurization rates are lower. Consequently, the volumes of catalyst required as well as the operating temperatures are also lower.
• the VVH (hourly volume speed) of desulfurization step f) can be 1.5 times greater than the VVH of step d), and / or the temperature of desulfurization step f) can for example be at least 10 ° C lower and advantageously at least 20 ° C than that of step d).
• the desulfurization rate of step f) is then mainly adjusted by the temperature.
• said difference can be adjusted, without departing from the scope of the invention, by means of any parameter known to act on the desulfurization rate of each step d) or f), for example by using to carry out the step f), a less active catalyst than that of step d).
• the difference in activity between the catalysts of steps d) and f) can for example be obtained by using, for step f), a catalyst containing a smaller quantity of metals or a support with a lower specific surface area compared to the catalyst. from step d).
• Another solution may consist in using a catalyst partially deactivated in step f).
• step f) The operating conditions during step f) are therefore adjusted according to the characteristics of the feed to be treated in order to achieve the most desulfurization rate often strictly greater than 80%, preferably greater than 85% and so very preferred greater than 92%, or even greater than 95%.
• the difference between first and second stage desulphurization rates hydrodesulfurization is generally greater than 1 percent, preferably greater than 2 percent, and most preferably, greater than 3 percent in absolute value.
• the catalysts used during stages d) and f) comprise at least one element of group VIII and / or at least one element of group VIB on an appropriate support.
• the group VIII metal content expressed as oxide is generally between 0.5 and 15% by weight, preferably between 1 and 10% by weight.
• the metal content of group VIB is generally between 1.5 and 60% by weight, preferably between 3 and 50% by weight.
• the element of group VIII, when it is present, is preferably cobalt, and the element of group VIB, when it is present, is generally molybdenum or tungsten.
• the catalyst support is usually a porous solid, such as for example an alumina, a silica-alumina or other porous solids, such as for example magnesia, silica or titanium oxide, alone or in combination. mixture with alumina or silica-alumina.
• the catalyst according to the invention preferably has a specific surface of less than 190 m 2 / g, more preferably less than 180 m 2 / g, and very preferably less than 150 m 2 / g.
• the catalyst After introduction of the element (s) and possibly shaping of the catalyst (when this step is carried out on a mixture already containing the basic elements), the catalyst is in a first activated stage.
• This activation can correspond either to an oxidation and then to a reduction, either to a direct reduction, or to a calcination only.
• the calcination step is generally carried out at temperatures ranging from approximately 100 to approximately 600 ° C. and preferably between 200 and 450 ° C, under an air flow.
• the catalyst is preferably used at least in part in its sulfurized form.
• the introduction of sulfur can occur before or after any activation step, that is to say calcination or reduction.
• no oxidation step of the catalyst is carried out when the sulfur or a sulfur-containing compound has been introduced onto the catalyst.
• the sulfur or a sulfur-containing compound can be introduced ex situ, that is to say outside the reactor where the process according to the invention is carried out, or in situ, that is to say in the reactor used for the process according to the invention.
• the catalyst is preferably reduced under the conditions described above, then sulphurized by passing a charge containing at least one sulfur compound, which once decomposed leads to the fixing of sulfur on the catalyst.
• This charge can be gaseous or liquid, for example hydrogen containing H 2 S, or a liquid containing at least one sulfur-containing compound.
• Example 1 relates to a desulfurization process without intermediate elimination of H 2 S and with a hydrodesulfurization step.
• a hydrodesulfurization catalyst A is obtained by impregnation “without excess of solution ”of a transition alumina in the form of surface beads specific of 130 m2 / g and pore volume 0.9 ml / g, with an aqueous solution containing molybdenum and cobalt in the form of ammonium heptamolybdate and cobalt nitrate.
• the catalyst is then dried and calcined in air at 500 ° C. Content in cobalt and molybdenum from this sample is 3% CoO and 10% MoO3.
• catalyst A 100 ml of catalyst A are placed in a tubular hydrodesulfurization bed reactor fixed.
• the catalyst is first sulfurized by treatment for 4 hours under a pressure of 3.4 MPa at 350 ° C, in contact with a load consisting of 2% sulfur as dimethyldisulfide in n-heptane.
• the charge treated is a catalytic cracking gasoline whose initial point boiling point is 50 ° C and the end point is 225 ° C. Its sulfur content is 2000 ppm weight and its bromine index (IBr) is 69 g / 100 g, which corresponds, approximately 36% by weight of olefins.
• This charge is treated on catalyst A, under a pressure of 2 MPa bar, an H 2 / HC ratio of 300 l / l and a VVH of 2 h -1 .
• Table 1 shows the influence of temperature on the desulfurization and saturation rates of olefins. Temperature (° C) Sulfur content of desulphurized petrol (ppm) Mercaptans content (ppm) Desulfurization rate (%) IBr of desulphurized petrol Olefin saturation rate (HDO) 310 41 32 97.9 20.3 70.6 320 23 20 98.8 14.7 78.7 330 12 11 99.4 10 85.5
• the operating conditions required to reach 10 ppm of sulfur with this type of very sulfur gasoline are a high temperature (> 310 ° C) and a low VVH (2 h -1 ). Under these conditions, it is possible to achieve desulfurization rates greater than 99%, but the saturation rate of the olefins then becomes very high (greater than 85%), which is harmful for the octane number.
• Example 2 relates to a desulfurization process with two hydrodesulfurization steps and the intermediate elimination of the H 2 S formed, in accordance with the prior art.
• Catalyst A is used under milder conditions than those of Example 1. According to the prior art, the desulfurization rate of the second hydrodesulfurization stage is greater than that of the first stage.
• the load processed is the same as the load of Example 1.
• the charge is sent to the reactor of Example 1 on the catalyst A mixed with hydrogen.
• the operating temperature is 285 ° C.
• the other operating conditions are specified in Table 2.
• the effluents leaving the reactor contain 239 ppm of sulfur. They are cooled and stripped in order to separate the hydrogen and H 2 S from the hydrocarbon phase.
• the stripped effluents are then reinjected into the reactor loaded with catalyst A as a mixture with fresh hydrogen, according to the operating conditions of said second step indicated in table 2.
• the feed rate was multiplied by 1.5 with respect to the flow of the first stage.
• the experimental device used includes an online sulfur analyzer which makes it possible to continuously measure the sulfur content in the effluents.
• the temperature of the reactor during the second stage was adjusted in order to produce a gasoline containing 10 ppm of sulfur.
• Example 2 shows that the process comprising two hydrodesulfurization steps with intermediate elimination of H 2 S is much more selective than the one-step process implemented in Example 1.
• the gasoline produced in the Example 2 has the same sulfur content as the gasoline of Example 1, but the saturation rate of olefins (HDO) is here 46.7% against 85.5% for Example 1.
• the process used Work according to Example 2 therefore makes it possible to minimize the processes leading to the saturation of the olefins during hydrodesulfurization.
• the desulfurization rate of the first step is, on the contrary, Example 2 superior to that of the second step.
• the charge treated is the same as that of Examples 1 and 2.
• the charge is sent to the reactor described above on the catalyst A mixed with hydrogen.
• the operating temperature is 300 ° C.
• the other operating conditions are specified in Table 3.
• the effluents leaving the reactor respectively contain 117 ppm of sulfur.
• the procedure is the same as for Example 2: the effluents are cooled and stripped in order to separate the hydrogen and the H 2 S from the hydrocarbon phase which is reinjected into the reactor loaded with catalyst A, in mixture with fresh hydrogen, according to the operating conditions indicated in Table 3.
• the feed rate was multiplied by 1.5 with respect to the rate of the first desulfurization step.
• the temperature was adjusted so as to finally recover at the outlet of the reactor a gasoline containing 10 ppm of sulfur.
• the process according to the invention that is to say the use of a desulfurization rate of the first stage higher than that of the second stage achieves the same sulfur content in desulfurized gasoline, as well as the same rate of saturation of olefins as the prior art, illustrated by Example 2.
• the effluent produced by the process according to the invention contains 30% less mercaptans than the gasoline from Example 2.
• the implementation of the method according to this invention therefore not only greatly limits the saturation of olefins, but in addition, to greatly decrease the mercaptan content and therefore the corrosivity of the gasoline produced.

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• 2002
  • 2002-03-29 FR FR0204108A patent/FR2837831B1/fr not_active Expired - Lifetime
• 2003
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  • 2003-03-28 JP JP2003090289A patent/JP2003327970A/ja active Pending
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