Catalyst for alkylation of C.sub.4 -C.sub.5 isoparaffin by at least one C.sub.3 -C.sub.6 olefin

BACKGROUND OF THE INVENTION
The present invention relates to a catalyst of silica and an acid phase comprising sulphuric acid and the compound HB(HSO.sub.4).sub.4, the silica having been impregnated by said acid phase. The invention also relates to the preparation and use of said catalyst in catalytic alkylation of isoparaffin (isobutane and/or isopentane) in the presence of at least one olefin containing 3 to 6 carbon atoms per molecule.
In order to supply internal combustion engines with spark ignition, and particularly engines with a high compression ratio, it is particularly advantageous to have fuels with high octane ratings, that is to say consisting essentially of heavily branched paraffin hydrocarbons. The alkylation of isoparaffins (isobutane and/or isopentane) by at least one olefin containing 3 to 6 carbon atoms per molecule allows such products to be obtained. This reaction requires the use of very acidic catalysts, particularly for reducing parasitic reactions such as hydride abstraction from the olefin and of polymerization which provide slightly branched hydrocarbons with a low octane rating and unsaturated hydrocarbons, cracking reactions and dismutation reactions.
The existing processes for production of hydrocarbons by alkylation of isobutane by olefins generally use either sulphuric acid or hydrofluoric acid as the catalyst. In these processes the acid catalyst constitutes a liquid phase which is placed in contact with the liquid isobutane/olefin(s) mixture to form an emulsion. These processes are expensive and give rise to significant problems with regard to personal and environmental safety. In order to remedy these problems, different catalytic systems of sulphuric acid and hydrofluoric acid in liquid phase have been sought.
In order to catalyze the alkylation reactions of isoparaffins by olefins, it has already been proposed to develop acid catalysts from numerous acid solids of different types. Amongst the families of acid catalysts, molecular sieves, macroreticular resins, possibly associated with BF.sub.3, Lewis and/or Bronsted acids deposited on various inorganic supports, chlorous aluminium, graphites interpenetrated by Lewis and/or Bronsted acids and anions deposited on oxide supports such as ZrO.sub.2 /SO.sub.4 can be cited. These solids lead to the production of branched isoparaffins but suffer from several major faults, among which the use of often very high isobutane/olefin molar ratios to limit the magnitude of secondary reactions and the poor stability over time of the catalytic activity (inhibition of the catalyst by deposition of unsaturated oligomers) can be cited; these catalysts therefore have to be frequently regenerated. Moreover, the weak acidity of certain acid solids, such as molecular sieves, for example, necessitates the use of high reaction temperatures, which is prejudicial to obtaining hydrocarbons with a high octane rating.
European patent application EP-A-0539277 describes a catalyst containing silica and a solid acid phase consisting of sulphuric acid; the silica according to said patent application is such that its porous volume is between 0.005 and 1.5 cm.sup.3 per gram and its specific surface is between 0.01 and 1,500 m.sup.2 per gram. Said acid phase can if required contain an additive selected from the group formed by H.sub.3 PO.sub.4, B(OH).sub.3, BF.sub.4 H, FSO.sub.3 H, CF.sub.3 CO.sub.2 H, SbF.sub.5, CF.sub.3 SO.sub.3 H and SO.sub.3.
French patent application FR-A-2 687 935 describes a catalyst consisting of a silica with a specific surface of between 0.01 and 1,500 m.sup.2 per gram and a total porous volume of between 0.005 and 1.5 cm.sup.3 per gram and an acid phase in solid state containing at least sulphuric acid and sulphuric anhydride, the silica having been impregnated with said acid phase. Said acid phase may possibly contain boric acid B(OH).sub.3, the content by weight of boric acid being between 0.01% and 50%.
SUMMARY OF THE INVENTION
The present invention relates to a catalyst containing of silica and an acid phase comprising silica and an acid phase and the compound HB(HSO.sub.4).sub.4, the silica having been impregnated with said acid phase, said catalyst being such that it is composed substantially of particles with an average diameter of between 0.1 and 150 .mu.m (1 .mu.m=10.sup.-6 m) preferably between 5 and 110 .mu.m and even more preferably between 5 and 80 .mu.m, in that its content by weight of acid phase is greater than 40%, preferably greater than 70%, in that the silica, before its impregnation with said acid phase, has a total porous volume of between 0.5 and 6 cm.sup.3 per gram, preferably between 0.6 and 6 cm.sup.3 per gram, and even more preferably between 1.5 and 6 cm.sup.3 per gram, and in that said acid phase consists of (in % by weight) between 0.4 and 68.8%, preferably between 0.4 and 60% of the compound HB(HSO.sub.4).sub.4 and between 31.2 and 99.6%, preferably between 40 and 99.6% of the compound H.sub.2 SO.sub.4, said acid phase being characterised by the fact that it contains neither sulphuric anhydride (SO.sub.3) nor boric acid [B(OH).sub.3 ].
In particular, said acid phase does not contain non-associated sulphuric anhydride, that is to say not having reacted with the boric acid, nor non-associated boric acid, that is to say not having reacted with the sulphuric anhydride.
The invention also relates to the preparation and use of said catalyst in catalytic alkylation of at least one isoparaffin selected from the group formed by isobutane and isopentane (that is to say isobutane and/or isopentane: isobutane, or isopentane, or isobutane and isopentane) in the presence of at least one olefin with 3 to 6 atoms of carbon per molecule.
The catalyst according to the present invention leads, in a surprising manner, to improved catalytic performance with respect to those described in European patent application EP-A-0539277 and also with respect to those described in French patent application FR-A-2 687 935.
The compound HB(HSO.sub.4).sub.4 contained in the acid phase of the catalyst according to the invention can be obtained by all the methods known to the man skilled in the art. For example, and in a non-limiting manner, the preferred method according to the invention can be cited, which involves reacting 1 mol of boric acid B(OH).sub.3 with 3 mols of sulphuric anhydride SO.sub.3 and 1 mol of sulphuric acid H.sub.2 SO.sub.4 to obtain 1 mol of the compound HB(HSO.sub.4).sub.4.
The silica used as a support can contain impurities such as, for example, oxides, alkalines, alkaline-earths, aluminium compounds or any other impurities known to the man skilled in the art, the total quantity of the impurities generally not exceeding 2% by weight of the silica.
The silica is generally such that, before its impregnation with said acid phase, its specific surface is between 0.1 and 1,500 m.sup.2 per gram. Moreover, said silica is generally constituted substantially of particles with an average diameter of between 0.1 and 150 .mu.m, preferably between 5 and 110 .mu.m and even more preferably between 5 and 80 .mu.m.
The acid phase generally occupies between 80 and 100% of the total porous volume of the silica, preferably between 90 and 100% of said porous volume.
The process for preparation of the catalyst according to the invention generally comprises at least two stages. In a first stage the silica is calcined at a temperature greater than 50.degree. C., preferably greater than 80.degree. C. and even more preferably between 150.degree. and 600.degree. C., for example equal to approximately 500.degree. C. The duration of this calcination stage is normally between 10 minutes and 50 hours, preferably between 15 minutes and 25 hours. The calcination is generally carried out in the presence of dry air or a dry air/nitrogen mixture, at a rate of between 0.001 and 10 litres per hour per gram, preferably between 0.1 and 5 l/h/g. The second stage consists of impregnation of said calcined silica with said acid phase. Any of the techniques well known to the man skilled in the art can be used to carry out this stage. A stage of preparation of the acid phase, prior to the impregnation stage, can be added to this process of preparation.
The catalyst according to the invention thus prepared has not been subjected to any calcination subsequent to the impregnation stage. When it is used in the alkylation of isoparaffin(s) by at least one olefin, it is not subjected, prior to its use, to any calcination and thus between the impregnation stage and said use, it is not subjected to any calcination. The catalyst according to the invention thus prepared is therefore immediately ready for use.
The catalyst according to the present invention is used in a process which allows the alkylation reaction of isoparaffin by at least one olefin to be carried out in the best conditions. In particular said reaction being characterised by strong exothermic reaction (approximately 83.6 kJ per mol of transformed butene, if the olefin is butene and if the isoparaffin is isobutane), the use of the catalyst according to the present invention allows a good temperature homogeneity and concentration of reactants to be obtained.
In the process of alkylation of isoparaffin(s) using the catalyst according the present invention, the operating conditions, and more particularly the temperature and pressure, are generally selected in a manner such that the mixture constituted by the isoparaffin(s), the olefin(s) and the reaction products is liquid. Moreover, it is important that the catalyst is immersed in said liquid in order to ensure that there is a good liquid/solid contact.
The catalyst according to the invention is advantageously used in the reaction zone of alkylation of isobutane and/or isopentane with at least one olefin containing 3 to 6 carbon atoms per molecule, in a liquid phase and in a mixture together with isoparaffin or a mixture of isoparaffins. The catalyst according to the invention can be used in an expanded bed, in an almost perfectly agitated reaction zone, or circulating bed, and is preferably used in a process which uses a continuous liquid phase, the catalyst being used in the form of a suspension, for example, according to the two implementations described hereinafter.
In the case where the catalyst is used in the form of a suspension, in a first implementation a reaction zone with an almost perfect mix can be used, that is to say with a perfect mix or near-perfect (agitated or Grignard vessel), using at least one agitation means, for example by means of a helix, in order to obtain sufficient agitation of the catalyst in suspension in the hydrocarbonated liquid phase, which consists generally of isoparaffin (isobutane and/or isopentane), at least one olefin, possibly at least one inert dilutant (for example, propane and normal butane) and the products of the alkylation reaction. The charge to be converted, composed of isobutane and/or isopentane and at least one olefin can be, for example, introduced in a liquid form at at least one point within the hydrocarbonated liquid phase present in the reaction zone.
A second implementation of the catalyst according to the present invention in suspension in a hydrocarbonated phase is the cocurrent flow fluidized bed or circulating bed. In this implementation the catalyst in suspension in the hydrocarbonated liquid phase, generally consisting of isobutane and/or isopentane, at least one olefin, possibly at least one inert dilutant (for example propane or normal butane) and the products of the alkylation reaction, circulate from bottom to top in the reaction zone. The group constituted by the suspension of catalyst in the hydrocarbonated phase then circulates through at least one heat exchanger and at least one pump, before being introduced again at the entrance to the reaction zone. The charge to be converted, constituted by isobutane and/or isopentane and at least one olefin is introduced either in liquid form or in gaseous form at at least one point in the reaction zone.
In the two types of implementation previously described, isoparaffin (isobutane and/or isopentane) not having been converted, or having been introduced in excess with respect to the stoichiometry of the reaction, is generally recycled after separation of the alkylate, either by direct introduction into the reaction zone or by mixing with the charge to be converted.
The isoparaffin(s)/olefin(s) mixture is generally introduced into the reaction zone at a spatial speed per hour, expressed in weight of olefin introduced per unit of catalyst and per hour (w.p.h.) of between 0.001 and 10 h.sup.-1, and preferably between 0.002 and 2.sup.h-1. Said mixture can also be carried out in the interior of the reaction zone. In all cases, the mixture constituted in this manner is in the reaction zone under conditions of pressure and temperature such that the mixture of hydrocarbons remains fluid on the catalyst.
The reaction temperature is generally lower than +10.degree. C., preferably lower than 0.degree. C. and in manner often more preferable, lower than -3.degree. C. The pressure of the reaction zone is sufficient to maintain the hydrocarbons in a liquid state in said zone.
In order to limit secondary reactions, an excess of isoparaffin(s) with respect to the olefin(s) can be used. By way of example, in the case of alkylation of isobutane by a butene, the isobutane can be introduced pure in the charge or in the form of a mixture of butanes containing, for example, at least 40% isobutane. Moreover, a pure butane or else a mixture of isomeric butanes can be introduced. In any case, the isobutane/butene(s) molar ratio in the charge is generally between 1 and 100, preferably between 3 and 50 and in a manner often preferred, between 5 and 15.
When the nature of the catalyst and the reaction conditions and chosen judiciously (in particular the temperature), the catalyst according to the invention allows the production of alkylation products of at least one isoparaffin by at least one olefin which are valuable as fuels for engines and constituents for petrol, and which consist of, for example, at least 60% mols of paraffin having 8 atoms of carbon per molecule and less than 1% mols of non-saturated compounds, the paraffins consisting of 8 atoms of carbon per molecule composed of 70 to 98% in mols of trimethylpentanes.
Another advantage of the catalyst according to the present invention is the possibility of alkylizing isobutane with mixtures of olefins with 3 to 6 carbon atoms per molecule at low temperatures, where the proportion of olefins with 4 atoms of carbon per molecule is very significant.
The following examples illustrate the invention without thereby limiting the scope thereof.

EXAMPLE
Example 1
Preparation of catalyst 1 according to the invention
14 g of macroporous silica with a specific surface equal to 27 m.sub.2 per gram, with a total porous volume equal to 1 cm.sup.3 per gram, with particles of an average diameter equal to 110 .mu.m is activated by calcination in air for 4 hours at 500.degree. C. The solid thus activated is preserved in argon. Then 100m.sup.3 of a mixture composed of 80% by weight of sulphuric acid (99.99%) and 20% by weight of sulphuric anhydride is prepared. After this 0.993 g of boric acid is added to the 10 .cent.m.sup.3 of mixture prepared above to obtain 20.28 g of acid phase. After the reaction of the sulphuric anhydride and the boric acid in the presence of sulphuric acid, and respectively in molar ratios 3/1/1 (that is to say 1 mol of boric acid with 3 mols of sulphuric anhydride and 1 mol of sulphuric acid) an acid phase is obtained which contains the compound HB(HSO.sub.4).sub.4 in solution in H.sub.2 SO.sub.4 and containing 31.69% by weight of HB(HSO.sub.4).sub.4 and 68.31% by weight of H.sub.2 SO.sub.4.
After this dry impregnation of 11 g of the calcined solid with 14.31 g of the mixture described above is carried out. The catalyst 1 thus obtained contains 14.31 g of acid phase and 11 g of silica, that is a content by weight of acid phase of 56.5%; it is preserved in an argon atmosphere at -18.degree. C.
Alkylation of isobutane by butene-1 with catalyst 1
20 g of catalyst 1 prepared according to the method described in example 1 is introduced into a glass reactor of the Fischer & Porter type with a volume of 360 ml, previously purged by argon discharge. The reactor containing the catalyst is then closed, then placed under low vacuum, then cooled to the temperature of -20.degree. C.
72 cm.sup.3 of isobutane is then added to the reactor containing the catalyst while agitating, said reactor being immersed in a cold bath at -20.degree. C. The catalyst +isobutane system is kept agitated for 30 minutes in order to homogenize the temperature.
100 cm.sup.3 of a mixture composed of 24% by volume of butene-1 and 76% by volume of isobutane is added regularly for a total of 10 hours, the temperature of the reactor being maintained at -15.degree. C. for the whole duration of the injection.
After reaction, the hydrocarbon phase is drawn off from the reactor, and the isobutane is slowly evaporated. The alkylate is collected and analyzed by chromatography in the vapour phase; its composition by weight is given in table 1.
Example 2
Preparation of catalyst. 2 (according to French patent application FR-A-2 687 935)
To prepare catalyst 2, 11 g of the same macroporous silica as used for the preparation of catalyst 1 is used, the calcination conditions being identical. The solid thus activated is preserved in argon. Then 7 cm.sup.3 of a mixture composed of 80% by weight of sulphuric acid (99.99%) and 20% by weight of sulphuric anhydride is prepared. After this 0.81 g of boric acid is added to the 7 cm.sup.3 of mixture prepared above to obtain 14.31 g of acid phase. After the reaction of the sulphuric anhydride and the boric acid in the presence of sulphuric acid, and respectively in molar ratios 3/1/1, an acid phase is obtained which contains the compound HB(HSO.sub.4).sub.4 in solution in H.sub.2 SO.sub.4 and containing 31.42% by weight of HB(HSO.sub.4).sub.4, 67.76% by weight of H.sub.2 SO.sub.4 and 0.82% by weight of B(OH).sub.3.
After this dry impregnation of 11 g of the calcined solid with the whole of the mixture described above is carried out. The catalyst 2 thus obtained contains 14.31 g of acid phase and 11 g of silica, that is a content by weight of acid phase of 56.5%; it is preserved in an argon atmosphere at -18.degree. C.
Alkylation of isobutane by butene-1 with catalyst 2
The test of catalytic alkylation of isobutane by butene-1 is repeated under the same experimental conditions as those described in example 1, but instead of regularly adding 100 cm.sup.3 of a mixture composed of 24% by volume of butene-1 and 76% by volume of isobutane for a total duration of 10 hours, 50 cm.sup.3 of the same mixture is added in 10 hours, that is a supply of reactants and thus of butene-1, twice as weak as in example 1, with the catalyst 1. The results are described in table 1.
Example 3
Preparation of catalyst 3, not according to the invention
To prepare catalyst 3, 1 1 g of the same macroporous silica as used for the preparation of catalysts 1 and 2 is used, the calcination conditions being identical. The solid thus activated is preserved in argon. Then 30 g of a mixture composed of 80% by weight of sulphuric acid (100%) and 20% by weight of sulphuric anhydride is prepared.
After this 1.42 g of boric acid is added to the 30 g of mixture prepared above to obtain 31.42 g of acid phase. After the reaction of the sulphuric anhydride and the boric acid in the presence of sulphuric acid, and respectively in molar ratios 3/1/1 (that is to say 1 mol of boric acid with 3 mols of sulphuric anhydride and 1 mol of sulphuric acid), an acid phase is obtained which contains 29.3% by weight of HB(HSO.sub.4).sub.4, 69.2% by weight of sulphuric acid and 1.52% by weight of sulphuric anhydride.
After this dry impregnation of 11 g of the calcined solid with 14.31 g of the mixture described above is carried out. The catalyst 3 thus obtained contains 14.31 g of acid phase and 11 g of silica, that is a content by weight of acid phase of 56.5%; it is preserved in an argon atmosphere at -18.degree. C.
Alkylation of isobutane by butene-1 with catalyst 3
The test of catalytic alkylation of isobutane by butene-1 is repeated under the same experimental conditions as those described in example 2. The results are described in table 1.
TABLE 1______________________________________Comparison of catalysts 1, 2 and 3Alkylate Catalyst 1 Catalyst 2 Catalyst 3composition (according (not according to (not according to(% by to the the invention; the invention;weight) invention) free B(OH).sub.3) free SO.sub.3______________________________________C.sub.5 -C.sub.7 % 2.0 2.4 6.2C.sub.8 % 95.2 94.6 85.5C.sub.9 .sup.+ % 2.8 3 8.3______________________________________
This table shows the advantage of working with the catalyst according to the invention, containing an acid phase comprising sulphuric acid and the compound HB(HSO.sub.4).sub.4 and without boric acid or sulphuric anhydride. Indeed, the presence of the compound HB(HSO.sub.4), in the acid phase in the absence of SO.sub.3 and B(OH)3 allows a catalyst 1 according to the invention to be obtained which is more active as it is working with a supply of reactants (butene-1 and isobutane) that is with a supply of butene-1 twice as large as that used in the case of catalysts 2 and 3 which respectively contain boric acid B(OH).sub.3 and sulphuric anhydride SO.sub.3. The catalyst 1 according to the invention, under stricter test conditions (butene-1 supply twice as large) is also more selective as shown in table 1.
Example 4
Preparation of catalyst 4 according to the invention
15 g of silica with a total porous volume equal to 2.6 .cent.m.sup.3 per gram, with a specific surface equal to 420 m.sup.2 per gram and an average particle diameter equal to 75 .mu.m is activated by heating with a supply of dry N.sub.2 at 500.degree. C. for 12 hours. The silica thus activated is preserved in dry nitrogen. Then 2.97 g of boric acid is added to 100 g of a solution of sulphuric anhydride in sulphuric acid, containing 11.5% by weight of sulphuric anhydride and 88.5% by weight of sulphuric acid to obtain 102.97 g of acid phase. After the reaction of the sulphuric anhydride and the boric acid in the presence of sulphuric acid, and respectively in molar ratios 3/1/1 an acid phase is obtained which contains the compound HB(HSO.sub.4).sub.4 in solution in H.sub.2 SO.sub.4 and containing 18.6% of HB(HSO.sub.4).sub.4 and 81.4% by weight of H.sub.2 SO.sub. 4.
After this dry impregnation of 10 g of the above activated silica is carried out with 47.5 g of the phase described previously. The solid thus obtained, designated catalyst 4, has a content by weight of acid phase equal to 82.6% by weight It is kept protected from humidity in argon at -18.degree. C.
Alkylation of isobutane by butene-1 with catalyst 4
20 g of catalyst 4 prepared according to the method described above is introduced into a glass reactor of the Fischer & Porter type with a volume of 360 ml, previously purged by argon discharge. The reactor containing the catalyst is then closed, placed under low vacuum, then cooled to the temperature of -20.degree. C.
150 cm.sup.3 of isobutane is then added to the reactor containing the catalyst while agitating (helix), said reactor being immersed in a cold bath at -5.degree. C. The catalyst+isobutane system is kept agitated for 30 minutes in order to homogenize the temperature.
5 g of butene-1 per hour is added regularly for a total of 6 hours, the temperature of the reactor being maintained at -5.degree. C. for the whole duration of the injection.
After reaction, the hydrocarbon phase is drawn off from the reactor, then analysed by chromatography in the vapor phase. Its composition by weight is given in table 2. The olefin conversion is 100%.
Example 5
Preparation of catalyst 5 not according to the invention
To prepare catalyst 5, 10 g of the same silica as used for the preparation of catalyst 4 is used, the calcination conditions being identical. The solid thus activated is preserved in argon. Then dry impregnation of 10 g of said activated silica is carried out with 47.5% of a solution of sulphuric acid of 99.9% by weight. The solid thus obtained, designated catalyst 5, has a content by weight of acid phase equal to 82.6% by weight. It is kept protected from humidity in argon at -18.degree. .
Alkylation of isobutane by butene-1 with catalyst 5
The test of catalytic alkylation of isobutane by butene-1 is repeated under the same experimental conditions as those described in example 4. The results are described in table 2.
TABLE 2______________________________________Comparison of catalysts 4 and 5Alkylate Catalyst 4 Catalyst 5composition (according to the (not according to(% by weight) invention) the invention)______________________________________C.sub.5 -C.sub.7 % 5.3 9.1C.sub.8 % 91.6 82.9C.sub.9 .sup.+ % 3.1 8.0______________________________________
This table shows the advantage of working with a catalyst containing an acid phase composed of sulphuric acid and the compound HB(HSO.sub.4).sub.4. Indeed, the presence of the compound HB(HSO.sub.4).sub.4 allows a catalyst 4 according to the invention to be obtained which is more selective as shown in table 2.
Example 6
Preparation of catalyst 6 according to the invention
15 g of silica with a total porous volume equal to 1.85 cm.sup.3 per gram, with a specific surface equal to 186 m.sup.2 per gram and an average particle diameter equal to 35 .mu.m is activated by heating with a supply of dry nitrogen at 500.degree. C. for 12 hours. The silica thus activated is preserved in dry nitrogen. Then 6.715 g of boric acid is added to 100 g of a solution of sulphuric anhydride in sulphuric acid, containing 25.9% by weight of sulphuric anhydride and 74.1% by weight of sulphuric acid to obtain 106.715 g of acid phase. After the reaction of the sulphuric anhydride and the boric acid in the presence of sulphuric acid, and respectively in molar ratios 3/1/1 an acid phase is obtained which contains the compound HB(HSO.sub.4).sub.4 in solution in H.sub.2 SO.sub.4 and containing 40.5% of HB(HSO.sub.4).sub.4 and 59.5% by weight of H.sub.2 SO.sub.4.
After this dry impregnation of 10g of the above activated silica is carried out with 34 g of the phase described previously. The solid thus obtained, designated catalyst 6, has a content by weight of acid phase equal to 77.3% by weight. It is kept protected from humidity in argon at -18.degree. C.
Alkylation of isobutane by butene-1 with catalyst 6
Alkylation test 6A
20 g of catalyst 6 prepared according to the method described above is introduced into a glass reactor of the Fischer & Porter type with a volume of 360 ml, previously purged by argon discharge. The reactor containing the catalyst is then closed, placed under low vacuum, then cooled to the temperature of -20.degree. C.
150 cm.sup.3 of isobutane is then added to the reactor containing the catalyst while agitating (helix), said reactor being immersed in a cold bath at -5.degree. C. The catalyst+isobutane system is kept agitated for 30 minutes in order to homogenise the temperature.
4 g per hour of butene-1 is regularly added for a total of 24 hours, the temperature of the reactor being maintained at -5.degree. C. throughout the whole injection time.
After reaction, the hydrocarbon phase is drawn off from the reactor, then analyzed by chromatography in the vapor phase. Its composition by weight is given in table 3. The olefin conversion is 100%.
Alkylation test 6B
20 g of catalyst 6 prepared according to the method described above is introduced into a glass reactor of the Fischer & Porter type with a volume of 360 ml, previously purged by argon discharge. The reactor containing the catalyst is then closed, placed under low vacuum, then cooled to the temperature of -20.degree. C.
150 cm.sup.3 of isobutane is then added to the reactor containing the catalyst while agitating (helix), said reactor being immersed in a cold bath at -5.degree. C. The catalyst+isobutane system is kept agitated for 30 minutes in order to homogenize the temperature.
20 g per hour of butene-I is added regularly for a total of 6 hours, the temperature of the reactor being maintained at -5.degree. C. for the whole duration of the injection.
Alkylation test 6B thus differs from alkylation test 6B in that the supply of butene-1 is 5 times greater in alkylation test 6B.
After reaction, the hydrocarbon phase is drawn off from the reactor, then analyzed by chromatography in the vapor phase. Its composition by weight is given in table 3. The olefin conversion is 100%.
Example 7
Preparation of catalyst 7 not according to the invention
To prepare catalyst 7, 10 g of the same silica as used for the preparation of catalyst 6 is used, the calcination conditions being identical. The solid thus activated is preserved in argon. Then dry impregnation of 10 g of the above activated silica is carried out with 34 g of a solution of sulphuric acid (H.sub.2 SO.sub.4) at 99.9% by weight. The solid thus obtained, designated catalyst 7, has a content by weight of acid phase equal to 77.3% by weight. It is kept protected from humidity in argon at -18.degree. .
Alkylation of isobutane by butene-1 with catalyst 7
Alkylation test 7A
20 g of catalyst 7 prepared according to the method described above is introduced into a glass reactor of the Fischer & Porter type with a volume of 360 ml, previously purged by argon discharge. The reactor containing the catalyst is then closed, placed under low vacuum, then cooled to the temperature of -20.degree. C.
150 cm.sup.3 of isobutane is then added to the reactor containing the catalyst while agitating (spring), said reactor being immersed in a cold bath at -5.degree. C. The catalyst+isobutane system is kept agitated for 30 minutes in order to homogenize the temperature.
4 g per hour of butene-1 is added regularly for a total of 24 hours, the temperature of the reactor being maintained at -5.degree. C. for the whole duration of the injection. The same operating conditions are used as for alkylation test 6A.
After reaction, the hydrocarbon phase is drawn off from the reactor, then analyzed by chromatography in the vapor phase. Its composition by weight is given in table 3. The olefin conversion is 100%.
Alkylation test 7B
The test of alkylation of isobutane by butene-1 with catalyst 7 is repeated under the same experimental conditions as those described in example 6 for alkylation test 6B. The results are described in table 3.
TABLE 3______________________________________Comparison of catalysts 6 and 7 Catalyst 6 Catalyst 7 Catalyst 6 Catalyst 7Alkykate (according (not accord- (according (not accord-compos- to the ing to the to the ing to theition invention) invention) invention) invention)(% by Alkylation Alkylation Alkylation Alkylationweight) test 6A test 7A test 6B test 7B______________________________________C.sub.5 -C.sub.7 % 4 8.4 8.7 --C.sub.8 % 92.9 84.7 81.6 --C.sub.9 .sup.+ % 3.1 6.9 9.7 C.sub.9 .sup.+ >80______________________________________
This table shows the advantage of working with a catalyst according to the invention, containing an acid phase composed of sulphuric acid and the compound HB(HSO.sub.4).sub.4. Indeed, the presence of the compound HB(HSO.sub.4).sub.4 allows a catalyst 6 according to the invention to be obtained which is more selective as shown in table 3 by the alkylation test 6A with respect to the alkylation test 7A carried out with catalyst 7, not according to the invention, under the same operating conditions.
Furthermore, the comparison of alkylation tests 6B and 7B, carried out under the same experimental conditions, shows that catalyst 6 according to the invention is more active and selective than catalyst 7, not according to the invention, which leads to a major degree to the formation of heavy C.sub.9.sup.+ compounds.

Number	Date	Country	Kind
93 10896	Sep 1993	FRX
93 14994	Dec 1993	FRX

Number	Date	Country
2081271	Apr 1993	CAX
67467	May 1982	EPX
325811	Dec 1988	EPX
539277	Oct 1992	EPX

Catalyst for alkylation of C.sub.4 -C.sub.5 isoparaffin by at least one C.sub.3 -C.sub.6 olefin

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