CATALYTIC COMPOSITION IN THE FORM OF A PICKERING EMULSION

Abstract

The present invention relates to a catalytic composition in the form of what is known as a Pickering emulsion, said composition comprising a first non-aqueous liquid phase L1 comprising hydrocarbon compounds, within which droplets of a second liquid phase L2 are stabilized by solid particles, said second liquid phase L2 comprising at least one ionic liquid of formula Q.sup.+A.sup., Q.sup.+ being an organic cation and A.sup. being an anion, and in which a Brnsted acid HB is dissolved.

Claims

1. A catalytic composition in the form of what is known as a Pickering emulsion, said composition comprising a first non-aqueous liquid phase L1 comprising hydrocarbon compounds, within which droplets of a second liquid phase L2 are stabilized by solid particles, said second liquid phase L2 comprising at least one ionic liquid of formula Q.sup.+A.sup., Q.sup.+ being an organic cation and A being an anion, and in which a Brnsted acid HB is dissolved.

2. The catalytic composition as claimed in claim 1, characterized in that the organic cation Q.sup.+ is a quaternary ammonium and/or a quaternary phosphonium and/or a trialkylsulfonium, and in that the anion A.sup. is an anion that forms with the cation Q.sup.+ a salt which is liquid below 150 C.

3. The catalytic composition as claimed in claim 1, characterized in that the anion A.sup. is chosen from the anions tetrafluoroborate, tetraalkylborate, hexafluorophosphate, hexafluoroantimonate, alkylsulfonate, in particular methylsulfonate, perfluoroalkylsulfonate, in particular trifluoromethylsulfonate, fluorosulfonate, sulfate, phosphate, perfluoroacetate, in particular trifluoroacetate, perfluorosulfonamide, in particular bis-trifluoromethanesulfonyl amide (CF.sub.3SO.sub.2).sub.2N, fluorosulfonamide, perfluorosulfomethide, in particular tris-trifluoromethanesulfonyl methide (CF.sub.3SO.sub.2).sub.3C.sup. and carboranes.

4. The catalytic composition as claimed in claim 1, characterized in that the cation Q.sup.+ is chosen from the following compounds ##STR00002## for which R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are identical or different, bonded together or not, and represent hydrogen or hydrocarbyl groups having from 1 to 12 carbon atoms, in particular saturated or unsaturated alkyl groups, or cycloalkyl groups or aromatic, aryl or aralkyl, groups, comprising from 1 to 12 carbon atoms.

5. The catalytic composition as claimed in claim 1, characterized in that the Brnsted acid HB comprises an anion B chosen from the anions tetrafluoroborate, tetraalkylborates, hexafluorophosphate, hexafluoroantimonate, alkylsulfonates, in particular methylsulfonate, perfluorosulfonate, in particular trifluoromethylsulfonate, fluorosulfonate, sulfate, phosphate, perfluoroacetate, in particular trifluoroacetate, perfluorosulfonamide, in particular bis-trifluoromethanesulfonyl amide (CF.sub.3SO.sub.2).sub.2N, fluorosulfonamide, perfluorosulfomethide, in particular tris-trifluoromethanesulfonyl methide (CF.sub.3SO.sub.2).sub.3C.sup. and carborane.

6. The catalytic composition as claimed in claim 1, characterized in that the Brnsted acid HB has the formula Q.sub.2.sup.+A.sub.2.sup., in which Q.sub.2.sup.+ represents an organic cation comprising at least one sulfonic acid or carboxylic acid function, and A.sub.2.sup. represents an anion, in particular the same anion as the anion A.sup. of the ionic liquid.

7. The catalytic composition as claimed in claim 1, characterized in that the first liquid phase L1 comprises one or more saturated hydrocarbons, in particular of linear or cyclic alkane type, and/or one or more unsaturated hydrocarbons, in particular of olefin or aromatic compound type, said hydrocarbon or hydrocarbons preferably having between 3 and 20 carbon atoms.

8. The catalytic composition as claimed in claim 1, characterized in that the solid particles are chosen from: silica particles, preferably functionalized with hydrophobic hydrocarbon groups, clay particles, preferably modified with organic or amphiphilic molecules, magnetic nanoparticles, in particular of Fe.sub.3O.sub.4, carbon nanotubes, particles of graphene oxides, particles of synthetic polymers, particles of a material of natural origin preferably chosen from hydroxyapatite, chitosan, cyclodextrin, dextran, particles in the form of cellulose nanocrystals or nanofibers, particles of biological material, in particular of food grade, preferably chosen from starch, zein, soy proteins, bacteria and yeasts, with the optional addition to the particles of at least one surfactant.

9. The catalytic composition as claimed in claim 1, characterized in that the largest dimension of the droplets is between 1 m and 1000 m, preferably between 2 m and 100 m, in particular between 10 m and 50 m.

10. The catalytic composition as claimed in claim 1, characterized in that the content of solid particles relative to the second liquid phase L2 is from 0.1% to 10% by weight, in particular from 0.5% to 5% by weight, preferably from 1% to 3% by weight.

11. The catalytic composition as claimed in claim 1, characterized in that the ratio by volume between the second liquid phase L2 and the first liquid phase L1 is between 2:1 and 1:10, preferably between 1:1 and 1:5.

12. The catalytic composition as claimed in claim 1, characterized in that the concentration of Brnsted acid HB within the second liquid phase L2 is between 0.05% and 40.0% by weight, preferably between 0.1% and 5% by weight.

13. A process for preparing the catalytic composition as claimed in claim 1, characterized in that it comprises the following steps: dispersing solid particles in the first liquid phase L1, with stirring, in particular with magnetic or mechanical stirring, preparing the second liquid phase L2 by adding Brnsted acid to the ionic liquid comprising at least one organic cation Q.sup.+ and one anion A.sup., adding the second liquid phase L2 to the first liquid phase L1 with the supply of dispersive energy, in particular by mechanical stirring means, a colloid mill, a membrane system, an ultrasonic stirring means, a microfluidic system.

14. An acid catalysis process, characterized in that a catalytic composition in the form of what is known as a Pickering emulsion is used, said composition comprising a first non-aqueous liquid phase L1 comprising hydrocarbon compounds, within which droplets of a second liquid phase L2 are stabilized by solid particles, said second liquid phase L2 comprising at least one ionic liquid of formula Q.sup.+A.sup., Q.sup.+ being an organic cation and A.sup. being an anion, and in which a Brnsted acid HB is dissolved.

15. The process as claimed in claim 14, characterized in that it is a process of alkylation of aromatic hydrocarbons, of oligomerization of olefins, of dimerization of isobutene, of isomerization of n-olefins to isoolefins, of isomerization of n-paraffins to isoparaffins, and of alkylation of isobutane by olefins.

Description

DESCRIPTION OF THE EMBODIMENTS

[0064] The coalescence stability of the catalytic composition emulsion is evaluated by an optical method based on multiple light scattering. The analysis of the light transmission and backscattering signals (wavelength 880 nm) is carried out using a Turbiscan apparatus sold by the company Formulaction. The technique makes it possible to reveal possible sedimentation, creaming and coalescence phenomena. The apparatus is used to verify that there is no coalescence of the dispersed phase of the emulsion and to confirm the stability of the emulsion to coalescence.

[0065] Within the meaning of the present invention, the different embodiments presented can be used alone or in combination with one another, without any limit to the combinations.

[0066] For the purposes of the present invention, the various ranges of parameters for a given step, such as the pressure ranges and the temperature ranges, can be used alone or in combination. For example, for the purposes of the present invention, a preferred range of pressure values can be combined with a range of more preferred temperature values.

[0067] In the text hereinbelow, the expressions of between . . . and . . . and between . . . and . . . are equivalent and mean that the limiting values of the interval are included in the described range of values. Should such not be the case and should the limiting values not be included in the range described, such a clarification will be provided by the present invention.

[0068] The invention will be described in greater detail with the aid of the non-limiting examples below.

EXAMPLES

Example 1 (Comparative): Dimerization of Isobutene in a Two-Phase System

[0069] A Fisher-Porter tube with a volume of 50 ml, equipped with a magnetic bar and dried beforehand in an oven and evacuated under vacuum, is charged, under an argon atmosphere, with 5.6 g of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([BMI][NTf.sub.2]) and 0.014 g of HNTf.sub.2 acid. The mixture is stirred for a few minutes and a clear solution containing 0.3% by weight of HNTf.sub.2 acid is obtained. 1.25 g of tetradecane (deaerated beforehand, with a water content of less than 10 ppm) are then added, this serving as internal standard. (As a reminder, the role of the internal standard is as follows: The internal standard is a compound inert with respect to the chemical reaction carried out, which is introduced in a known amount into the reaction medium. It makes it possible to measure the amount of products formed after reaction, by gas chromatography, as follows (schematically): the chromatographic area of the internal standard peak, which corresponds to the mass which was initially introduced, is measured, then the area of the products is measured, and by rule of three the mass of these products is deduced therefrom). 44 g of a liquid feedstock containing 12% by weight of isobutene and 88% by weight of n-heptane, i.e. 5.28 g of isobutene, are then introduced at ambient temperature. Stirring is then started (time zero of the reaction). After reacting for 10 minutes at 25 C., the stirring is stopped. The pressure is evacuated and the Fisher-Porter tube is opened in order to remove a few milliliters of the supernatant organic phase. The latter is analyzed by gas chromatography (PONA column) after treatment with sodium hydroxide (0.1 M) in order to eliminate possible traces of acid followed by drying over MgSO.sub.4.

[0070] The isobutene conversion becomes established at 36%. The selectivity for dimerization products (trimethyl-2,4,4-pentenes) and trimerization products (C12) is 60% and 40%, respectively.

Example 2 (Comparative): Dimerization of Isobutene in a Two-Phase System

[0071] The catalytic test is carried out in the same way as in example 1, except that the reaction time is increased to 60 min. The isobutene conversion becomes established at 88%. The selectivity for dimerization products (trimethyl-2,4,4-pentenes) and trimerization products (C12) is 51% and 49%, respectively.

Example 3 (According to the Invention): Preparation of the Pickering Emulsion [BMI][NTf.SUB.2.]/HNTF.SUB.2./SiO.SUB.2./Heptane

[0072] 5.13 g of n-heptane, constituting the first liquid phase L1, were introduced into a beaker under an inert atmosphere.

[0073] Then 0.145 g of solid silica particles, which in this case are silica fume particles with the commercial reference Aerosil R972, sold by Evonik.

[0074] These particles, which are functionalized with dimethyldichlorosilane groups, are dispersed in n-heptane with magnetic stirring.

[0075] In a burette, the second liquid phase L2 is prepared: a mixture consisting of 5.6 g of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([BMI][NTf2]) and 0.014 g of HNTf2 acid. This mixture (second liquid phase L2) is poured dropwise into the beaker containing the n-heptane (first liquid phase L1) and the silica particles, with continuous application of dispersion energy provided by a rotor-stator system (UltraTurrax device, sold by the company IKA, 000 rpm).

[0076] The Pickering emulsion thus obtained contains 2.5% by mass of silica particles relative to the dispersed ionic liquid phase (L2). The emulsion thus produced has a number-average droplet size of 20 m, with a minimum diameter of 9 m and a maximum diameter of 54 m. No coalescence was detected by the Turbiscan apparatus according to the method described above.

Example 4 (According to the Invention): Dimerization of Isobutene Using the Pickering Emulsion System Described in Example 3

[0077] A Fisher-Porter tube with a volume of 50 ml, equipped with a magnetic bar and dried beforehand in an oven and evacuated under vacuum, is charged, under an argon atmosphere, with all of the Pickering emulsion prepared according to example 3, and also 1.18 g of tetradecane (deaerated beforehand, with a water content of less than 10 ppm), which serves as internal standard. 42.2 g of a liquid feedstock containing 12% of isobutene and 88% of n-heptane, i.e. 5.06 g of isobutene, are then introduced at ambient temperature. Stirring is then started (time zero of the reaction). The reaction starts.

[0078] After reacting for 10 minutes at 25 C., the stirring is stopped. The pressure is evacuated and the Fisher-Porter tube is opened in order to remove a few milliliters of the supernatant organic phase that appears above the emulsion. To do this, the emulsion is allowed to settle at the bottom of the Fischer-Porter tube, and the upper phase containing the products is taken for analysis.

[0079] In order to measure the conversion and the selectivity, it is specifically merely necessary to take a sample that is representative of the continuous phase. (To recover all the products obtained, the entirety can be centrifuged.)

[0080] This sample is analyzed by gas chromatography (PONA column) after treatment with sodium hydroxide (0.1 M) in order to eliminate possible traces of acid and drying over MgSO.sub.4.

[0081] The isobutene conversion becomes established at 35%. The selectivity for dimerization products (trimethyl-2,4,4-pentenes) and trimerization products (C12) is 91% and 9%, respectively.

Example 5 (According to the Invention): Dimerization of Isobutene Using the Pickering Emulsion System Described in Example 3

[0082] The catalytic test is carried out in the same way as in example 4, except that the reaction time is increased to 60 min. The isobutene conversion becomes established at 88%. The selectivity for dimerization products (trimethyl-2,4,4-pentenes) and trimerization products (C12) is 74% and 26%, respectively.

[0083] Table 1 below shows all the results obtained on the basis of examples 1 to 5. It reveals the very significant impact of the invention on the control of the selectivity for dimerization product: specifically, the comparative examples have a dimer selectivity/trimer selectivity ratio of at most 1.50 (example 1), while the examples according to the invention have a ratio of at least 2.84 (example 5) up to 10 (example 4), and therefore a selectivity that is at least virtually doubled.

TABLE-US-00001 TABLE 1 Time Conversion Dimer sel. Trimer sel. Feedstock (min) (% by wt.) (% by weight) (% by weight) Example 1 isobutene 10 36 60 40 (comparative) Example 2 isobutene 60 88 51 49 (comparative) Example 4 Isobutene 10 35 91 9 (according to the invention) Example 5 Isobutene 60 88 74 26 (According to the invention)

Example 6 (Comparative): Dimerization of an Isobutene/1-Butene Mixture in a Two-Phase System

[0084] A Fisher-Porter tube with a volume of 50 ml, equipped with a magnetic bar and dried beforehand in an oven and evacuated under vacuum, is charged, under an argon atmosphere, with 5.6 g of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([BMI][NTf.sub.2]) and 0.014 g of HNTf.sub.2 acid. The mixture is stirred for a few minutes and a clear solution containing 0.3% by weight of HNTf.sub.2 acid is obtained. 1.57 g of tetradecane (deaerated beforehand, water content less than 10 ppm) are then added, this serving as internal standard. 37.7 g of a liquid feedstock containing 9.7% by weight of isobutene, 10% by weight of 1-butene, 5% by weight of n-butane (internal standard) and 75% by weight of n-heptane, i.e. 3.66 g of isobutene and 3.77 g of 1-butene, are then introduced at ambient temperature. Stirring is then started (time zero of the reaction). After reacting for 10 minutes at 25 C., the stirring is stopped. The pressure is evacuated, the gaseous phase is recovered in a balloon and analyzed by gas chromatography on an Alumina Plot column.

[0085] The Fisher-Porter tube is opened in order to remove a few ml of the supernatant organic phase. The latter is analyzed by gas chromatography (PONA column) after treatment with sodium hydroxide (0.1 M) in order to eliminate possible traces of acid and drying over MgSO.sub.4.

[0086] The isobutene conversion becomes established at 32%, while the 1-butene conversion is only 5.4%. The selectivity for dimerization products (trimethyl-2,4,4-pentenes) and trimerization products (C12) is 67% and 33%, respectively.

Example 7 (According to the Invention): Dimerization of an Isobutene/1-Butene Mixture in a Pickering Emulsion

[0087] A Fisher-Porter tube with a volume of 50 ml, equipped with a magnetic bar and dried beforehand in an oven and evacuated under vacuum, is charged, under an argon atmosphere, with all of the Pickering emulsion prepared according to example 3, and also 1.51 g of tetradecane (deaerated beforehand, with a water content of less than 10 ppm), which serves as internal standard. 36.2 g of a liquid feedstock containing 9.7% by weight of isobutene, 10% by weight of 1-butene, 5% by weight of n-butane (internal standard) and 75% by weight of n-heptane, i.e. 3.51 g of isobutene and 3.62 g of 1-butene, are then introduced at ambient temperature. Stirring is then started (time zero of the reaction). After reacting for 10 minutes at 25 C., the stirring is stopped. The pressure is evacuated, the gaseous phase is recovered in a balloon and analyzed by gas chromatography on an Alumina Plot column. The Fisher-Porter tube is opened in order to remove a few ml of the supernatant organic phase. The latter is analyzed by gas chromatography (PONA column) after treatment with sodium hydroxide (0.1 M) in order to eliminate possible traces of acid and drying over MgSO.sub.4.

[0088] The isobutene conversion becomes established at 34%, while the 1-butene conversion is only 5.1%. The selectivity for dimerization products (trimethyl-2,4,4-pentenes) and trimerization products (C12) is 93% and 7%, respectively.

[0089] Table 2 below shows all the results obtained on the basis of examples 6 to 7.

TABLE-US-00002 TABLE 2 Conversion Dimer sel. Trimer sel. Time iC4.sup.=/C4.sup.=1 (% by (% by Feedstock (min) (% by wt.) weight) weight) Example 6 Isobutene/1-butene 10 32/5.4 67 33 (comparative) Example 7 Isobutene/1-butene 10 34/5.1 93 7 (according to the invention)

[0090] It reveals the very significant impact of the invention on the control of the selectivity: specifically, comparative example 6 exhibits a dimer selectivity/trimer selectivity ratio of 2.03, while example 7 according to the invention exhibits a ratio of 13.29, and therefore a selectivity that is multiplied by a factor of 6.5.