FR2727404A1 - PROCESS FOR THE ALKYLATION OF C4-C5 ISOPARAFFIN WITH AT LEAST ONE C3-C6 OLEFIN IN A BIPHASIC MEDIUM - Google Patents

Abstract

The invention relates to the use in catalytic alkylation of at least one isoparaffin chosen from the group formed by isobutane and isopentane in the presence of at least one olefin comprising from 3 to 6 carbon atoms per molecule of a catalyst consisting essentially of sulfuric acid and the compound HB(HSO4)4, said catalyst comprising (by weight %) between 0.4% and 68.8% of the compound HB(HSO4)4 and between 31.2% and 99, 6% of the compound H2SO4, and said catalyst not containing sulfuric anhydride.

Description

The present invention relates to the use of a catalyst consisting

  essentially sulfuric acid and compound HB (HSO4) 4 in catalytic alkylation of paraffin (isobutane and / or isopentane) in the presence of at least one olefin comprising from 3 to

6 carbon atoms per molecule.

  To supply internal combustion and spark-ignition engines, and in particular engines with a high compression ratio, it is particularly advantageous to have fuels with high octane numbers, that is to say

  essentially consisting of highly branched paraffinic hydrocarbons.

  The alkylation of isoparaffin (isobutane and / or isopentane) with at least one olefin containing 3 to 6 carbon atoms per molecule makes it possible to obtain such products. This reaction requires the use of very acidic catalysts, in particular with the aim of reducing parasitic reactions such as the abstraction of olefin hydride and polymerization reactions which provide slightly branched hydrocarbons of low octane number. and unsaturated hydrocarbons,

  cracking reactions and dismrnutation reactions.

  Existing processes for the production of hydrocarbons by alkylation of isobutane by olefins generally use either sulfuric racide or hydrofluoric racide as catalyst. In these processes, where the reaction medium is two-phase, the acid catalyst constitutes a liquid phase which is brought into contact with the liquid isobutane-olefin (s) mixture to form an emulsion. For example, in the case of the use of sulfuric racide by Stratco technology (LF. Abright, Chem. Eng., August 15,1966, p. 143 and LF. Abright, Oi & Gas Journal, November 12, 1990 ), which is the most widespread, a emulsion is created, at one end of a horizontal reactor, by a turbine powered by the load and recycles crd'acide. In this case the continuous phase is the acid phase, because the volume ratio acid / hydrocarbons is greater than 1. The reaction takes place almost instantaneously at the level of the turbine. The olefins form crdakyle sulftes which then lead to the formation of ralkylate. The calories produced during the reaction are eliminated by a system of tubes inside the reactor in which circulates an alkylate-sobutane mixture cooled by expansion of part of the obutane at the outlet of the reactor. The separation of the two phases, acid and hydrocarbon, is carried out in a decanter located above the reactor. However, secondary oligomerization reactions followed by an oxidation reaction lead to the formation of "red oils which are, in fact, oligomers of high monocular weight and highly unsaturated. On the other hand, the oxidation of these products by racide sulfuric, leads to the formation of sulfur and SO 2 The red oils and water that are formed during these reactions are soluble in sulfuric racide and contribute to its dilution, thus the concentration of fresh racide entering the unit and which is close to 98-99% by weight, which gives a strong oxidizing power to racide, will decrease up to a titer of 92-90%. Below this value, racide must be extracted from the unit to regenerate. a continuous supply of fresh acid and a continuous extraction of spent acid are necessary to maintain a medium titer of racide around

  93-94% which ensures a good quality alkylate production.

  This continuous and significant consumption of sulfuric acid necessitates regeneration of the latter. The regeneration process consists in burning spent racide, recovering the S02 formed which is then oxidized to S03. Sulfuric anhydride (S03) brought into contact with the appropriate amount creau allows to obtain sulfuric racide having a titer of 98-99% by weight which will again be used to carry out the alkylation reaction. The cost of this regeneration step contributes about 30% of the operating cost of the alkylation process. Therefore, a catalytic formulation that would reduce acid consumption

  would increase the economic profitability of the alkylation units.

  The present invention relates to the use in alkylation of crisoparafine C4-C5 by at least one C3-C6 olefins of a catalyst consisting essentially of sulfuric acid (H2SO4) and of compound HB (HS04) 4. Said catalyst comprises (in% by weight) between 0.4 and 68.8%, preferably between 0.4 and 60%, of the compound HB (HSO4) 4 and between 31.2 and 99.6%, preferably between 40 and 99.6%, of the compound H2SO4. Said catalyst is such that it does not contain sulfuric anhydride (SO3)

not associated.

  Said catalyst is therefore an unsupported catalyst.

  Said catalyst used according to the invention has the advantage over sulfuric racide of title 98-99% by weight, currently used in cralkylation units, to have a greater or equal acidity while having a much more reliable oxidizing character. The use of said catalyst according to the invention therefore leads to a reduction in the consumption of catalyst and therefore to a reduction in the operating costs of the

alkylation units.

  In particular, said catalyst does not comprise non-associated sulfuric anhydride, that is to say which has not reacted with boric racide but may optionally contain excess, unassociated boric acid, ie ie not having reacted with

sulfuric anhydride.

  The invention thus relates to the use of said catalyst in catalytic alkylation at least one isoparaffin selected from the group formed by risobutane and risopentane (that is to say isobutane and / or isopentane: risobutane, or isopentane, or risobutane and risopentane) in the presence of at least one olefin comprising from 3 to 6

carbon atoms per molecule.

  Compound HB (HSO4) 4 included in said catalyst used according to the invention can be obtained by all the methods known to those skilled in the art. For example and without limitation, mention may be made of the preferred method according to the invention which consists in reacting 1 mole of boric acid B (OH) 3 with 3 moles of sulfuric anhydride SO 3

  and 1 mole cr of sulfuric acid H2SO4 to obtain 1 mole of compound HB (HSO4) 4.

  The process for preparing the catalyst used according to the invention generally comprises at least two steps. In a first step, a solution of the desired title of SO 3 in sulfuric racide is prepared. Then, in a second

  step the corresponding amount of boric acid, according to the reaction explained above

  above, is added so as to obtain a given solution of HB (HSO4) 4 in

H2S04.

  The catalyst used according to the present invention is used in a process which allows the dralkylation reaction of isoparaffin with at least one olefin to be carried out under the best conditions. In particular, said reaction being characterized by a high exothermicity (approximately 83.6 kJmol of butene transformed if the olefin is butene and if risoparaffin is isobutane), the use of the catalyst according to the present invention makes it possible to obtain good homogeneity of

  temperature and concentration of reagents.

  In particular, the catalyst according to the present invention is used by all the techniques known to those skilled in the art and which use a reactor and a

decanter.

  The isoparaffin (s) -olefin (s) mixture is generally introduced into the reaction zone at an hourly space speed, expressed in weight of olefin introduced per unit weight of catalyst and per hour (pph) of between 0.001 and 10 h- 1 and preferably between 0.002 and 2 h -1. Said mixing can also be carried out inside the reaction zone. In all cases the mixture thus formed is in the reaction zone under such pressure and temperature conditions

  that the hydrocarbon mixture remains liquid.

  The continuous phase is either the acid phase or the hydrocarbon phase and the medium

reaction is biphasic.

  The reaction temperature is generally below +20 C, preferably

  lower than +15 C and often more preferably between + 50C and -5C.

  The pressure in the reaction zone is sufficient to maintain the hydrocarbons

  1 5 with stiffness in said zone.

  In order to limit the side reactions, it is possible to use an excess of isoparaffin (s) relative to r '(the) olefin (s). By way of example, in the case of the alkylation of isobutane with a butene, isobutane can be introduced pure into the feed or in the form of a mixture of butanes containing for example at least 40% of isobutane. In addition, a pure butene or a mixture of isomeric butenes can be introduced. In all cases, the isobutaneibutne (s) molar ratio in the filler is generally between 1 and 100, preferably between 3 and 50 and

  often preferred between 5 and 15.

  When the nature of the catalyst and the reaction conditions are judiciously chosen (in particular the temperature), the catalyst according to the invention allows the production of alkylation products of at least one isoparaffin with at least one olefin which are advantageous as fuels for the petrol engines and components and which comprise, for example, at least 60 mol% of paralins having 8 carbon atoms per molecule and less than 1 mol% of unsaturated compounds, the paraffins comprising 8 carbon atoms per molecule

  comprising 70 to 98 mol% of trimethylpentanes.

  The following examples illustrate the invention without, however, limiting its scope.

Example 1

  Preparation of catalyst 1 according to the invention 100 g crd of a mixture consisting of 80% by weight of sulfuric acid (99.99%) and 20% by weight of sulfuric anhydride are prepared. Then add 5 g of boric acid to 100 g of the mixture prepared above to obtain 105 g of acid phase. Following the reaction of sulfuric anhydride and boric acid in the presence of sulfuric acid and respectively in the molar ratios 311/1 (i.e. 1 mole of boric acid with 3 moles of sulfuric anhydride and 1 mol of sulfuric acid), an acid phase is obtained which contains the compound HB (HSO4) 4 in solution in

  H2SO4 and comprising 31.69% by weight of HB (HSO4) 4 and 68.31% by weight of H2SO4.

  Alkylation of isobutane or butene-1 with catalyst I in the continuous xhydrocarbon phase 40 g of catalyst 1 prepared according to the method described in example 1 are introduced into a 500 ml crude steel reactor previously purged under flow of argon . The reactor containing the catalyst is then closed then i is

cooled to a temperature of 5 C.

  mi of isobutane are then added to the reactor containing the catalyst with stirring, speed of rotation 2000 revolutions per minute, said reactor being cooled to C by circulation of a cold liquid (0 C) in the double jacket with which i is equipped. Stirring (propeller) is maintained for a period of 30 minutes in order to

to homogenize the temperature.

  200 g of a mixture consisting of 10% by weight of butne-I1 and 90% by weight of isobutane is regularly added over a total period of 5 hours, the

  reactor temperature being maintained at 5 ° C. for the entire rinse time.

  After reaction and decantation, the hydrocarbon phase is withdrawn from the reactor, isolated, then neutralized and then analyzed by vapor phase chromatography, its weight composition is given in Table 1. The catalyst is then washed several times with rsobutane, then the carbon content present in the phase

acid is determined.

Example

  Preparation of catalyst 2 not in accordance with the invention 100 g of a mixture consisting of 80% by weight of sulfuric acid are prepared

  (100%) and 20% by weight of sulfuric anhydride.

  Then 4.73 g of boric acid are added to 100 g of the mixture prepared above in order to obtain 104.73 g of acid phase. Following the reaction of sulfuric anhydride and boric racide in the presence of sulfuric acid and respectively in the molar ratios 3/1/1 (that is to say 1 mole of boric acid with 3 moles of sulfuric anhydride and 1 mole sulfuric cracide), an acid phase is obtained which comprising 29.3% by weight of compound HB (HSO4) 4, 692% by weight of sulfuric acid

  and 1.5% by weight of sulfuric hydride.

  Alkylation of isobutane by butene-1 with catalyst 2 in the continuous hydrocarbon phase The catalytic test of alkylation of isobutane by butene-1 is repeated under the same experimental conditions as those described in Example 1 and the

  same analyzes are carried out. The results are collated in Table 1.

  Table I: ComRaralson of catalysts 1 and 2 Example 1, Example 2, Alkylate catalyst composition 1 catalyst 2 X not consistent (% by weight) not in accordance with the invention rinvention S03 Ie

C5-C7 2.3 6.2

C8 93.8 85.5

  Cg9 + 3.9 8.3 Carbon content in 1.8 4.7 the acid phase This table highlights the importance of working with the catalyst according to the invention comprising an acid phase comprising sulfuric racide and the compound HB (HSO4) 4, and without sulfuric anhydride. Indeed, the presence of compound HB (HSO4) 4 in the acid phase, in the absence of SO3, makes it possible to obtain a catalyst 1 according to the invention which is more selective as indicated in Table 1 and which has, after the 5 hours of testing, a content lower carbon which is indicative of a lower consumption of acid phase per gram of alkylate

  product. These results are obtained in the continuous hydrocarbon phase.

Example 3

  Preparation of catalyst 3 in accordance with the invention 100 g of a sulfuric anhydride solution in sulfuric racide, 1 5 containing 11.5% by weight of sulfuric anhydride and 88.5% by weight of sulfuric acid, are prepared. To this solution are added 2.97 g of boric acid in order to obtain 102.97 g of acid phase. Following the reaction of sulfuric anhydride and boric racide in the presence of sulfuric dracid and respectively in the molar ratios 3/1/1, an acid phase is obtained which contains the compound HB (HSO4) 4 in solution in H2SO4 and comprising 18.6 % by weight of HB (HSO4) 4 and 81.4% by weight of H2SO4 Alkvlation of isobutane with butene-1 with catalyst 3 in continuous ohase of hydrocarbon 30g of catalyst 1 is prepared prepared according to the method described in Example 1 in a 500 ml crun steel reactor previously purged under an argon flow. The reactor containing the catalyst is then closed then I is

cooled to the temperature of 50C.

  100 ml of isobutane are then added to the reactor containing the catalyst with stirring, speed of rotation 2000 revolutions per minute, said reactor being cooled to C by circulation of a cold liquid (00 C) in the double jacket with which E is equipped. . The acid phase + isobutane catalytic system is left stirring

  (propeller) for a period of 30 minutes in order to homogenize the temperature.

  200 g cr of a mixture consisting of 10% by weight of butene-1 and 90% by weight of isobutane are regularly added, over a total period of 5 hours, the

  temperature of the reactor being maintained at 5 ° C. for the entire duration of rmjeclion.

  After reaction and decantation, the hydrocarbon phase is withdrawn from the reactor, isolated, then neutralized and then analyzed by vapor phase chromatography, its weight composition is given in Table 1. The catalyst is then washed several times with risobutane, then the carbon content present in the phase

acid is determined.

Example 4

  Preparation of catalyst 4 not in accordance with the invention

  1 5 The catalyst 4 consists of 100 g of a 99% by weight sulfuric acid solution.

  Alkylation of risobutane or butene-1 with catalyst 4 The catalytic test of alkylation of risobutane with butene-1 is repeated under the same experimental conditions as those described in Example 3. The results are collated in Table 2; they are obtained in phase

continuous hydrocarbon.

  Table 2: Comoaralson of catalysts 3 and 4 Alkylate composition Example 3, catalyst 3 Example 4, catalyst 4 (% by weight) in accordance with the invention not in accordance with ivenon

C5-C7 5.4 9.1

C8 91.2 82.9

C9 + 3.4 8.0

  Carbon content in 1.9 4.0 the acid phase _ This table highlights the importance of working with a catalyst comprising an acid phase comprising sulfuric racide and the compound HB (HSO4) 4. Indeed, the presence of the compound HB (HSO4) 4 makes it possible to obtain a catalyst 4 according to the invention which is more selective as shown in Table 2 and which exhibits, after the 5 hours of testing, a lower carbon content which is indicative lower acid phase consumption per gram of alkylate produced.

Example 5

  Preparation of the catalyst 5 according to the invention This is the same catalyst, according to the invention, as that described in the example

I of the present invention.

  Alkylation of risobutane or butene-1 with catalyst 5 in the continuous phase add2 100 g of catalyst 5, prepared according to the same method as that described in example 1, are introduced into a steel reactor with a volume of 250 ml previously purged under argon flow. The reactor containing the catalyst is then closed then it

  is cooled to a temperature of 5 C.

  ml of isobutane are then added to the reactor containing the catalyst with stirring, speed of rotation 2000 revolutions per minute, said reactor being cooled to C by circulation of a cold liquid (0 C) in the double jacket with which i is equipped. Stirring (propeller) is maintained for a period of 30 minutes in order to

  2 5 to homogenize the temperature.

  Then, 17 g of a mixture consisting of 30% by weight of butene-1 and 70% by weight crisobutane are regularly added, for a total duration of 1 hour, the temperature of the reactor being maintained at 5 ° C. for the entire duration.

injection.

  After reaction and decantation, the hydrocarbon phase is withdrawn from the reactor, isolated, then neutralized then analyzed by vapor phase chromatography, its weight composition is given in table 3. The catalyst is then washed several times with risobutane, then the carbon content present in the phase

acid is determined.

  Preparation of catalyst 6 not in accordance with the invention Catalyst 6 consists of 100 g of a 99.5% by weight sulfuric acid solution. Alkylation of isobutane by butene-1 with catalyst 6 in the continuous phase Acde 100 g of catalyst 6 are introduced into a steel reactor with a volume of 250 ml previously purged under a flow of argon. The reactor containing the catalyst is

  then closed then it is cooled to the temperature of 5 C.

  ml of isobutane are then added to the reactor containing the catalyst with stirring, speed of rotation 2000 revolutions per minute, said reactor being cooled to 1 5 5 C by circulation of a cold liquid (0 C) in the double jacket of which is equipped. Stirring (propeller) is maintained for a period of 30 minutes in order to

to homogenize the temperature.

  Then, 17 g of a mixture consisting of 30% by weight of butene-1 and 70% by weight of isobutane are regularly added, for a total duration of 1 hour, the temperature of the reactor being maintained at 5 ° C. for the entire duration

injection.

  After reaction and decantation, the hydrocarbon phase is withdrawn from the reactor, isolated, then neutralized and then analyzed by vapor phase chromatography, its weight composition is given in Table 3. The catalyst is then washed several times with rsobutane, then the carbon content present in the phase

acid is determined.

  Table 3: Comparison of catalysts 5 and 6 Alkylate composition Example 5, catalyst 5 Example 6, catalyst 6 (% by weight) according to the invention not according to the invention

C5-C7 2.6 6.9

C8 94.3 85.8

C9 + 3.2 7.3

  Carbon content in 1.7 3.5 the acid phase This table shows that in the continuous acid phase it is also interesting to work with a catalyst comprising an acid phase comprising sulfuric racide and the compound HB (HSO4) 4. Indeed, the presence of the HB compound (HSO4) 4 makes it possible to obtain a catalyst 4 according to the invention which is more selective as indicated in Table 3 and which after 1 hour of testing has a lower carbon content which is indicative of lower acid phase consumption per gram of alkylate produced

Claims (4)

  1 - Use in catalytic aikylation crau minus one isoparaffin chosen from the group formed by risobutane and r'isopentane in the presence crd'at at least one olefin having 3 to 6 carbon atoms per molecule of a catalyst consisting essentially of sulfuric acid and of compound HB (HSO4) 4, said catalyst comprising (in% by weight) between 0.4% and 68.8% of compound HB (HSO4) 4 and between 31.2% and 99.6% of compound H2SO4, and said catalyst not containing of sulfuric anhydride.   2 - Use according to claim 1 wherein the reaction temperature is below +20 C and the pressure of the reaction zone is sufficient to   maintain the liquid-retaining hydrocarbons in said zone.   1 5 3 - Use according to any of claims 1 or 2 in which the temperature of   reaction is below +15 C and the pressure in the reaction zone is sufficient   to maintain the liquid-retaining hydrocarbons in said zone.   4 - Use according to one of claims 1 to 3 wherein the phase continues is the hydrocarbon phase.   - Use according to one of claims 1 to 3 in which the phase continues is the acid phase.   6 - Use according to one of claims I to 5 in which the compound   HB (HSO4) 4 is obtained by reacting 1 mole of boric acid with 3 moles   sulfuric anhydride and 1 mole sulfuric cracide.