FR2692814A1 - Alkylation catalyst for paraffin(s) - Google Patents

Abstract

A catalyst comprises a porous organic or mineral support, of surface area 0.01-150m2 per g and porous vol. 0.005-1.5cm3 per g, and at least one mixt. composed of an Al or B halide and an ammonium halide or amine halo-hydrate. The support is impregnated with this mixt. Also claimed, is the prepn. of the catalyst and use in catalytic alkylation processes.

Description

 The present invention relates to a catalyst comprising an organic or inorganic porous support and at least one mixture consisting of at least one aluminum halide and / or boron and at least one amine hydrohalide, and its use in catalytic alkylation. of isobutane and / or isopentane by means of at least one olefin comprising from 2 to 6 carbon atoms per molecule, that is to say a C2-C6 olefin, which makes it possible to obtain compounds paraffinic compounds with high degree of branching and high octane number.

 It is known that, for supplying internal combustion engines and spark ignition engines, and in particular engines with a high compression ratio, it is particularly advantageous to have fuels with a high octane number, that is to say constituted essentially by highly branched paraffinic hydrocarbons. The alkylation of isoparaffins (isobutane and / or isopentane) with olefins containing from 2 to 6 carbon atoms per molecule makes it possible to obtain such products. This reaction requires the use of highly acidic catalysts, in particular to reduce parasitic reactions such as olefin hydride abstraction and polymerization reactions, which provide poorly branched low-indexed hydrocarbons. octane and unsaturated hydrocarbons, cracking reactions and disproportionation reactions.

 Existing industrial processes for the production of hydrocarbons by the alkylation of isobutane and / or isopentane by C2-C6 olefins use either sulfuric acid or hydrofluoric acid as a catalyst. In these processes, the acid catalyst constitutes a liquid phase which is brought into contact with the isoparaffin liquid mixture (s) -olefin (s) to form an emulsion. These processes are expensive and pose significant problems with respect to the safety of people and the environment. In order to remedy these problems, different catalytic systems of sulfuric and hydrofluoric acid in the liquid phase have been sought.

To catalyze the isoparaffin alkylation reactions by olefins, it has been proposed to develop acid catalysts from many acidic solids of different natures. Among the families of acid catalysts include molecular sieves (see for example
US-A-3,236,762, US-A-3,251,902, US-A-3,644,565, US-A-4,377,721,
US-A-4,384,111 and US-A-4,300.01 5), macroreticular resins optionally combined with BF3 (see for example US-A-3 855 342,
US-A-3,855,343, US-A-3,862,258 and US-A-3,879,489), perfluorinated resins of NAFION type (see for example US-A-4,056,578 and US-A-4,038,213). ), Lewis and / or Bronsted acids deposited on various inorganic supports (see for example US-A-3,975,299, US-A-3,852,371 and US-A-3,979,476), chlorinated aluminas (see for example US-A-3,240,840, US-A-3,523,142,
US-A-3,607,859, US-A-3,523,141, US-A-4,066,716, US-A-4,083,800 and
US-A-4,066,716), graphites intercalated with Lewis acids and / or
Bronsted (see for example US-A-4.083.885, US-A-4.116.880,
US-A-4,128,596 and US-A-3,976,714) and anions deposited on oxide supports such as ZrO 2 / SO 4 (see for example J-01 288329, J-01 1245854-A,
J-01245953, J-61242641-A and J-61242641). These solids lead to the production of branched isoparaffins but suffer from several major defects, among which may be mentioned the use of a molar ratio isoparaffine (s) - olefin (s) often very high to limit the importance of side reactions and low stability over time of catalytic activity (catalyst inhibition by deposition of unsaturated oligomers); these catalysts must then be frequently regenerated. In addition, the low acidity of certain acidic solids, such as molecular sieves for example, requires the use of high reaction temperatures which is detrimental to obtaining hydrocarbons of high octane number.

On the other hand, the French patent application 92/00802 describes an alkylation catalyst comprising a porous organic or inorganic support and the mixture consisting of at least one aluminum halide and / or boron and at least one quaternary ammonium halide.

 The invention relates to a novel catalyst for obtaining high branching and high octane paraffinic compounds by alkylation of isobutane and / or isopentane, preferably isobutane, by means of at least one olefin comprising from 2 to 6 carbon atoms per molecule.

 The catalyst of the present invention contains an organic or inorganic porous support and at least one mixture consisting of at least one compound halide selected from the group consisting of boron and aluminum, that is to say from less an aluminum halide and / or boron, preferably an aluminum halide, and at least one amine hydrohalide, preferably an amine hydrochloride or hydrobromide, the support being impregnated with at least one mixture consisting of at least one aluminum halide and / or boron and at least one amine hydrohalide.

Said mixture is an ionic complex immiscible with the hydrocarbon phase commonly called "molten salt". It can be obtained liquid at ambient temperature, but also at a higher temperature, preferably below 1500C and even more preferably below 100 ° C. In all cases, it is liquid when it is impregnated on the support.

The support is chosen from porous organic or inorganic supports known to those skilled in the art. Among the organic supports that may be used include, but are not limited to, macroreticular resins, perfluorinated resins and charcoal. Among the mineral supports that can be used include oxides such as for example
SiO 2, ZrO 2, TiO 2, SnO 2, Al 2 O 3, Fe 2 O 3, HfO 2 and any combination of at least two of these compounds (ZrO 2 -TiO 2 for example). The preferred support is silica.

 The specific surface of the support that can be used must be between 0.01 and 1500 m 2 / g, preferably between 0.01 and 150 m 2 / g and even more preferably between 0.01 and 50 m 2 / g. . The total pore volume of the support should be between 0.005 and 1.5 cm3 / g, preferably between 0.005 and 1 cm3 / g and even more preferably between 0.005 and 0.8 cm3 / g. During the impregnation of said support with at least one mixture consisting of at least one aluminum halide and / or boron and at least one amine hydrohalide, said mixture (s) it is necessary to occupy a fraction of the total pore volume of the oxide support between 5 and 100%. The catalyst thus obtained is characterized by a specific surface area of between 0.01 and 500 m 2 / g, preferably between 0.01 and 150 m 2 / g and even more preferably between 0.01 and 40 m 2 / g.

 The aluminum and / or boron halides that can more particularly be used in the present invention are trifluorides, trichlorides and / or tribromides of aluminum and / or boron, such as Ait13, AlBr3, BC13 or BBr3, preferably trifluoride. , trichloride and / or aluminum trifluoride such as AIC13 and AlBr3. They can be used pure or in a mixture, for example, in variable proportions ranging from 99% of one of the halides to 99% of the other. It is thus possible to mix AIC13 with AlBr3, AIC13 with BC13 or AlBr3 with BBr3.

The amine halohydrates which are more particularly usable according to the invention comprise one mole of hydrohalic acid per mole of amine, but may also comprise at least two moles of hydrohalic acid per mole of amine, and preferably two moles of amine. hydrohalic acid per mole of amine.

 It is also possible to use mixtures of halohydrates with at least one mole of hydrohalic acid, for example mixtures of hydrohalides with one and two moles of hydrohalic acid.

dans lesquelles R1, R2, R3, R4 ou Rs identiques ou différents, représentent des restes hydrocarbyles, par exemple alkyl, cycloalkyl, aryl, aralkyl ou alkylaryl, ou bien encore représentent l'hydrogène, R5 pouvant être également un reste hydrocarbyle substitué comprenant par exemple au moins un atome différent de l'hydrogène et du carbone, comme l'azote.Pour obtenir un halohydrate d'amine, il est encore possible qu'un radical puisse unir deux molécules dont au moins l'une d'entre elles est telle que ci-dessus comme, par exemple, R1HN+=CR3-R6-CR3=N+ RIR2 (X-)2 o u R1 HN+=CR3-R6-CR3=N+R1 H (X-)2 ,R6 étant un radical et pouvant être un reste alkylène ou encore phénylène. Les cycles des formules (III) et (IV) sont constitués de 4 à 19 atomes, de préférence de 5 à 6 atomes, et peuvent comprendre, outre l'azote de l'amine, des atomes de carbone ou éventuellement d'autres atomes d'azote ces cycles pouvent être aromatiques ou non. Les cycles des formules (III) et (IV) peuvent être condensés avec d'autres cycles et porter des substituants hydrocarbonés tels que ceux définis pour Ri, des fonctions amines, des atomes de fluor, de chlore ou de brome.Said halo hydrates of amines are derived from cyclic amines or diamines or amines forming part of a ring which may comprise at least one nitrogen atom, and they correspond to the following general formulas:
R1R2R3NH + X- (I)

in which R1, R2, R3, R4 or Rs, which are identical or different, represent hydrocarbyl residues, for example alkyl, cycloalkyl, aryl, aralkyl or alkylaryl residues, or else represent hydrogen, R5 may also be a substituted hydrocarbyl residue comprising, for example, at least one atom other than hydrogen and carbon, such as nitrogen.To obtain an amine hydrohalide, it is still possible for a radical to unite two molecules, at least one of which is as above such as, for example, R1HN + = CR3-R6-CR3 = N + RIR2 (X-) 2 or R1 HN + = CR3-R6-CR3 = N + R1 H (X-) 2, R6 being a radical and may be an alkylene or phenylene residue. The rings of the formulas (III) and (IV) are composed of 4 to 19 atoms, preferably of 5 to 6 atoms, and may comprise, in addition to the nitrogen of the amine, carbon atoms or possibly other atoms. nitrogen these cycles can be aromatic or not. The rings of formulas (III) and (IV) can be condensed with other rings and carry hydrocarbon substituents such as those defined for R 1, amine functions, fluorine, chlorine or bromine atoms.

 Among the groups R 1, R 2, R 3, R 4 and R 5 there may be mentioned the hydrogen atom, the radicals, methyl, ethyl, propyl, isopropyl, butyl, secondary butyl, tertiary butyl, amyl, methylene, ethylidene, phenyl or benzyl radicals. ; R6 may be a methylene, ethylene, propylene or phenylene group. The rings as described in formula (IV) are represented by the families of pyridines, imidazoles, triazines, pyrazoles, pyrimidines, triazoles.

 In these formulas X represents a halide ion, preferably the bromide ion or the chloride ion.

 As examples of hydrochlorides or hydrobromides of amines which can be used according to the invention, mention may be made more particularly of pyridinium salts such as pyridinium hydrochloride and hydrobromide, hydrochlorides and hydrobromides of 2-picolinium, 3-picolinium or 4-pyridinium. -picolinium, the hydrochlorides and hydrobromides of piperidinium, piperazinium, morpholinium, methyl-2 pyrazinium, and pyrrolidinium.

 For components of a certain nature, the relative proportions of aluminum halide (s) and / or boron and of amine hydrohalide (s) determine both the acidity (or basicity) of the medium and its point. of crystallization. When the mole fraction of aluminum and / or boron halide (s) is less than 0.5, the mixture is very slightly acidic or even basic. If it is greater than 0.5, the medium is all the more acidic as this molar fraction is large. There is therefore a very wide range of acidity that can be varied according to the reactivity of the olefin, which has the advantage of minimizing parasitic oligomerization reactions by maximizing the reaction rate.

 The process for preparing the catalyst according to the invention comprises two stages. In a first step the support is calcined at a temperature greater than 50 ° C, preferably greater than 80 ° C and even more preferably between 200 and 600 ° C, for example equal to about 500 ° C. The duration of this step The calcination may be carried out in the presence of air or an air / nitrogen mixture, the flow rate being between 0.001 and 10 I / h / g. impregnation of the calcined product with at least one mixture consisting of at least one aluminum halide and / or boron and at least one amine hydrohalide.The impregnation temperature is such that the said (s) ) mixture (s) is (are) liquid (s) during the impregnation of the support.To achieve this step can be used all the techniques well known to those skilled in the art.The solid thus obtained is then stored at the The catalyst of the present invention is protected from moisture. thus consists of a porous organic or inorganic support impregnated with at least one mixture consisting of at least one aluminum halide and / or boron and at least one amine hydrohalide.

 The catalyst according to the present invention can be used pure or diluted with various materials having little catalytic activity in the reaction considered, for example, silica, alumina, magnesia or various clays, such as, for example, bentonite or montmorillonite. or kaolin.

 Said catalyst is advantageously used in a process where the olefin and / or a mixture of olefins is introduced into the reactor in the liquid phase and in mixture with the isoparaffin and / or a mixture of isoparaffins. The catalyst may be used in fixed bed, moving bed or fluid bed, or in suspension in the liquid phase of the reagents subjected to efficient stirring.

 The isoparaffin (s) -olefin mixture (s) may be introduced into the reactor at a space velocity per hour, expressed by weight of olefin introduced per unit weight of the catalyst and per hour of between 0.001 and 10 h -1, and preferably between 0.002 and 2 h 1 Said mixture can also be carried out inside the reactor. In all cases, the mixture thus formed is in the reactor under conditions of pressure and temperature such that the hydrocarbon mixture remains liquid on the catalyst.

 The reaction temperature is between -50 and 150 ° C., but the catalytic performances are improved when the reaction temperature is less than 5 ° C., preferably less than 0 ° C. and even more preferably less than -5 ° C. The reactor pressure must be sufficient to maintain the hydrocarbons in the liquid state in the reactor whatever the temperature.

 In order to limit the side reactions, an excess of isoparaffin (s) with respect to the olefin (s) is generally used. By way of example, in the case of the alkylation of isobutane with a butene, isobutane is introduced pure into the feedstock or in the form of a mixture of butanes containing, for example, at least 40% of isobutane. . In addition, pure butene or a mixture of isomeric butenes can be introduced. In all cases, the molar ratio of isobutane / butene (s) in the feed is between 1 and 100, preferably between 3 and 50 and often preferably between 5 and 10.

The products of the reaction can be checked regularly by measuring the bromine index, for example according to the draft French Standard
Pr. M. 07.071 of March 1969.

 When the nature of the catalyst and the working conditions of the catalyst are judiciously chosen (and in particular the temperature), the catalyst according to the invention allows the production of paraffin alkylation products with at least one olefin which are of interest. as fuels for engines and gasoline constituents and which comprise for example at least 60% (in moles) of paraffins having 8 carbon atoms per molecule and less than 1% (in moles) of unsaturated compounds, paraffins having 8 carbon atoms per molecule being composed of 70 to 98% (in moles) of trimethylpentanes.

 Another advantage of the catalyst according to the present invention is the possibility of alkylating, at low temperature, isobutane with mixtures of olefins having from 2 to 6 carbon atoms per molecule, wherein the proportion of olefins having at least 5 atoms carbon per molecule is very important (at least 10% by weight, preferably at least 40% by weight).

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

Example 1
Catalyst preparation
An ionic complex of normality 0.67 N is prepared in the following manner to a suspension of 24.8 g of freshly sublimed AIC13, in heptane 11.5 g of pyridinium hydrochloride are slowly added, with stirring at room temperature. using a magnetic bar. This gives a mixture, liquid at room temperature, very slightly colored. This mixture is stored under argon in the absence of moisture.

 13 g of macroporous silica with a specific surface area of 27 m 2 / g are activated by calcination in air for 4 hours at 500 ° C. The solid thus activated is kept under argon, followed by dry impregnation with 13 g of solid calcined with 8.8 g of mixture prepared as indicated above The catalyst thus obtained contains 8.8 g of mixture and 13 g of silica and is stored under argon at -18 ° C.

Alkylation of isobutane by butene-2
The catalyst prepared according to the method described above is introduced into a Fischer & Porter type glass reactor with a volume of 360 ml previously purged under an argon flow. The reactor containing the catalyst is then closed and placed under primary vacuum, and then cooled to -15 ° C.

 80.6 g of isobutane are then added to the reactor containing the catalyst with stirring, said reactor being immersed in a cold bath at -15 ° C. The catalyst + isobutane system is left stirring for a period of 30 minutes in order to homogenize the temperature.

 16.5 g of butene-2 are added regularly for a total duration of 3 hours, the temperature of the reactor being maintained at -15 ° C. throughout the duration of the injection.

 After reaction, the hydrocarbon phase is withdrawn from the reactor, the isobutane is evaporated slowly. The alkylate is collected and analyzed by vapor phase chromatography; its weight composition is given below. The conversion of the olefin is 100%. The composition of the alkylate, in% by weight, is reported in Table 1 below.

Table 1

<tb> iCg <SEP> I <SEP> 0.9
<tb><SEP> C6 <SEP> 1.1
<tb> This / <SEP> 1,3 <SEP>
<tb><SEP> C8 <SEP> 93.3 <SEP>
<tb><SEP> Cg <SEP> 1,2 <SEP>
<tb> C9 + <SEP> 2.2 <SEP>
<Tb>
The fraction Cg contains 93.2% by weight of trimethylpentanes, the calculated research octane number is 98.6.

Example 2
The isobutane alkylation catalytic test is repeated with butene-2 with the same catalyst as in Example 1, and a series of tests are carried out at different temperatures. The results are collated in Table 2 below.

Table 2

<tb> T <SEP> 0G <SEP> C5-C7 <SEP><SEP> C8 <SEP><SEP> C9 + <SEP> RON <SEP>
<tb><SEP> -20 <SEP> | <SEP> 2.1 <SEP> 0 <SEP> 95.2 <SEP> 2.7 <SEP> | <SEP> 99.5
<tb><SEP> -10 <SEP> 4.0 <SEP> 89.9 <SEP> 4.9 <SEP> 97.3
<tb><SEP> 0 <SEP> 5.9 <SEP> 87.8 <SEP> 7.3 <SEP> 96.1
<Tb>
This table highlights the interest of working at low temperatures.

Example 3
Catalyst preparation
An ionic complex of normality 0.67 N is prepared as follows at 28.8 g of freshly sublimed AIC13, in heptane 12.9 g of 4-picolinium hydrochloride are slowly added, with stirring with the aid of a magnetic bar. This gives a mixture, liquid at room temperature, very slightly colored. This mixture is stored under argon in the absence of moisture.

 13 g of macroporous silica with a specific surface area of 27 m 2 / g are activated by calcination in air for 4 hours at 500 ° C. The solid thus activated is kept under argon, followed by dry impregnation with 13 g of solid calcined with 8.5 g of mixture prepared as indicated above The catalyst thus obtained contains 8.5 g of mixture and 13 g of silica and is stored under argon at -18 ° C.

Alkylation of isobutane by butene-2
The catalyst prepared according to the method described above is introduced into a Fischer & Porter type glass reactor with a volume of 360 ml previously purged under an argon flow. The reactor containing the catalyst is then closed and then placed under primary vacuum, and then it is cooled to -15 C. The same catalytic test, alkylation of isobutane with butene 2, that carried out in Example I at -15tC is then repeated. The results are summarized in Table 3 below.

Table 3

<tb> iC5 <SEP> 1,1
<tb><SEP> C6 <SEP> 0.8
<tb> C7 <SEP> 1,4
<tb> C8 <SEP> 93.6
<tb> C9 <SEP> 1.0 <SEP>
<tb> Cg + <SEP> 2.1 <SEP>
<Tb>
The C8 fraction contains 94.0% by weight of trimethylpentanes, the calculated research octane number is 98.9.

Claims (8)

A catalyst comprising a porous organic or inorganic support with a specific surface area of between 0.01 and 1500 m 2 / g and a total pore volume of between 0.005 and 1.5 cm 3 / g and at least one mixture consisting of at least one halide of compound selected from the group consisting of aluminum and boron and at least one amine hydrohalide, the support having been impregnated with said mixture. 2. Catalyst according to claim 1 such that said mixture is an ionic complex, immiscible with the hydrocarbon phase, liquid during its impregnation on the support. 3. Catalyst according to one of claims 1 or 2 such that the compound halide selected from the group consisting of aluminum and boron is selected from the group consisting of AlCl3, AlBr3, BC13 and BBr3. 4. Catalyst according to one of claims 1 to 3 such that the general formula of the amine hydrohalide is one of the following formulas  R1R2R3RNH + X- (I)

 in which R1, R2, R3, R4 or Rg, identical or different, represent hydrocarbyl residues or hydrogen, and X- represents a halide ion. 5. Catalyst according to one of claims 1 to 4, such that the amine hydrohalide is chosen from the group formed by pyridinium salts such as pyridinium hydrochlorides and hydrobromides, 2-picolinium hydrochlorides and hydrobromides, and 3picolinium hydrochlorides and hydrobromides, 4-picolinium hydrochlorides and hydrobromides, piperidinium hydrochlorides and hydrobromides, piperazinium hydrochlorides and hydrobromides, morpholinium hydrochlorides and hydrobromides, 2-methyl-pyrazinium hydrochlorides and hydrobromides and hydrochlorides and hydrobromides pyrrolidinium. 6. Process for preparing a catalyst according to one of claims 1 to 5 such that the support is calcined and then impregnated with said mixture. 7. Use of the catalyst according to one of claims 1 to 5 or prepared according to claim 6, in a catalytic alkylation process of at least one element selected from the group consisting of isobutane and isopentane by at least an element selected from the group consisting of olefins comprising from 2 to 6 carbon atoms per molecule. The use of claim 7 wherein the temperature of the reaction is less than 5 ° C.