MXPA00000707A - Hydrogenolysis of glycerol - Google Patents

Abstract

A process for the catalytic hydrogenolysis of glycerol in the presence of a homogeneous catalyst that is based on a platinum group metal or a compound of a platinum group metal, an anion source, and a metal-complexing compound of the formula Q1Q2MQ3 (I) or Q1Q2MQMQ3Q4 (II) wherein M represents phosphorus, arsenic or antimony, Q represents a group that is covalently bonded to both M's and having at least two atoms in the bridge and Q1 to Q4 are independently similar or dissimilar optionally substituted hydrocarbyl groups or Q1 and Q2 and/or Q3 and Q4 represent similar or dissimilar optionally substituted hydrocarbylene groups.

Description

HYDROGENOLISIS OF GLICEROL DESCRIPTION OF THE INVENTION The invention relates to a process for the catalytic hydrogenolysis of glycerol. In particular, the invention relates to the preparation of propylene glycols (1,2- and 1,3-propanediols) and / or acrolein by the hydrogenolysis of glycerol. Propylene glycols and acrolein are valuable chemicals. For example, 1,3-propanediol (PDO) is an attractive monomer in the preparation of polyesters and polyurethanes. It can also be used to prepare cyclic ethers that find use as solvents. Likewise, acrolein and its dimer provide a valuable starting point for the synthesis of chemicals used in textile finishing, paper treatment and the manufacture of rubber chemicals, pharmaceuticals, plasticizers and synthetic resins. Propylene glycols and acrolein can be prepared by a variety of processes. For example, the PDO can be prepared by the hydroformylation of ethylene oxide, or by the hydrogenation of 3-hydroxypropionaldehyde. However, each of these processes requires chemicals as a starting point that have to be prepared separately, often at considerable cost. In addition, the REF .: 32403 initial chemical products can find other more valuable uses. The chemical industries have realized that our petrochemical resources are not unlimited. Therefore, they focused and still focus on natural resources as a starting point for their processes. For example, U.S. Patent No. 4,642,394 describes the process for the conversion of glycerol to lower oxygenated hydrocarbons, such as 1, - and 1,3-propanediol, by reacting glycerol with carbon monoxide and hydrogen (in a reaction of hydrogenolysis ") in the presence of a homogeneous catalyst containing tungsten components and a group VIII metal. The examples of this patent document, however, reveal the need for elevated temperature and pressure conditions (200 ° C, 4600 psig (323.38 kgf / cm2)). Therefore the process is not as attractive as it could be. The technique also includes examples of hydrogenolysis processes using heterogeneous catalysts. For example, DE-A-4, 302, 464 describes the conversion of glycerol to 1,2-propandiol and other products (but not 1,3-propanediol) using copper and chromium tablets at various temperatures and high pressures. U.S. Patent No. 5,326,912 employs a catalyst containing ruthenium, palladium and copper. However, glycerol is produced instead of converting it. The inventors now provide a process for the conversion of glycerol to lower oxygenated hydrocarbons which avoids the need for such high temperature and pressure conditions. Accordingly the invention provides a process for the catalytic hydrogenolysis of glycerol in the presence of a homogeneous catalyst which is based on a metal of the platinum group or a metal compound of the platinum group, an anion, and a metal complexing compound of the formula QXQ2MQ3 (I) or Q1Q2MQMQ3Q4 (II) where it represents phosphorus, arsenic or antimony, Q represents a group that is covalently bound to both M and that has at least two atoms in the bridge and Q1 to Q4 are independently optionally substituted hydrocarbyl groups similar or different or Q1 and Q2 and / or Q3 and Q4 represent similar or different optionally substituted hydrocarbylene groups. Note that the standard textbook "Advanced Organic Chemistry" by Jerry March (3rd ed., Pages 392-393) regarding the hydrogenolysis of alcohols mentions that "the hydroxyl groups of most alcohols can be rarely cleaved" . Examples of those that undergo the reaction easily are alcohols of the benzyl type. In addition, 1,3-glycols are mentioned as being especially susceptible to hydrogenolysis, whereas tertiary alcohols can be reduced by catalytic hydrogenolysis when the catalyst is bis (triphenylphosphine) platinum dichloride. It is therefore surprising that glycerol, which is not an alcohol of the benzyl type, can be converted to propylene glycols and / or acrolein. Furthermore, it is surprising that the glycerol conversion can be controlled to stop at the stage where propylene glycol and / or acrolein are produced. In the present specification the metals of the platinum group are defined as the metals with the atomic numbers 28, 46 and 78, that is nickel, palladium and platinum. Of those, palladium and platinum are preferred. Examples of suitable metal sources are nitrates, sulfates, metal sulphonates, carboxylic acids of metal salts with up to 12 carbon atoms or inorganic metal complexes, for example with carbon monoxide or acetylacetonate. Palladium acetate (II) and platinum (II) acetylacetonate are examples of preferred metal sources. The anion on which the catalyst is based can be obtained from sources such as acids and salts. The anion can also originate from salts of metals of the platinum group, in which case both components of the catalyst are provided by the same source.

The preferred anion sources in the catalyst systems of the present invention are strong acids, ie, acids having a pKa value of less than 3, preferably less than 2, measured in aqueous solution at 18 = C. the anions derived of these acids are not coordinated or coordinate weakly with the metals of the platinum group. Typical examples of suitable anions are phosphoric acid anions, sulfuric acids, hydrogen anions, sulfonic acids and halogenated carboxylic acids such as trifluoroacetic acid. Sulfonic acids are particularly preferred, for example methanesulfonic acid, trifluoromethanesulfonic acid, tert-butanesulfonic acid, p-toluenesulfonic acid and 2,4,6-trimethylbenzenesulfonic acid. Halide anions have been found particularly useful (in combination with other anions) when water is applied as the reaction solvent. Also, complex anions are suitable, such as the anions generated by a combination of a Lewis acid such as BF3, A1C13, SnF2, Sn (CF3S03) 2, SnCl2 or GeCl2, with a protic acid, such as a sulfonic acid , for example CF3SO3H or CH3SO3H or a hydrogen halide such as HF or HCl, or a combination of a Lewis acid with an alcohol. Examples of such complex anions are BF ~, SnCl3 ~, [SnCl2.CF3S03r and PF6".

Finally, mixtures of anions can also be used; in particular the mixture of halide anions in combination with another source of anion mentioned above. In the compounds that comprise metal of the formula (I) or (II), (each) M is a phosphorus atom, in which case the compounds are monophosphines or bisphosphines. Preferably, a compound that complexes metal of the general formula (II) is used. The group that forms the bridge in such a compound, represented by Q, is typically composed of carbon atoms. Preferably, the group forming the bridge contains from 2 to 3 carbon atoms in the bridge. The hydrocarbyl groups Q1 to Q4 can independently represent several non-cyclic or cyclic groups of up to 20 carbon atoms, preferably up to 15 carbon atoms, more preferably up to 10 carbon atoms, optionally substituted with substituents such as alkoxy groups with 1 to 4 carbon atoms, halogen atoms or groups (C to C alkyl) amino. Examples are alkyl groups such as the ethyl, isopropyl, sec-butyl and tert-butyl groups, cycloalkyl groups such as the cyclopentyl and cyclohexyl groups, and aryl groups such as the phenyl, tolyl and naphthyl groups.

In view of the higher activity of the resulting catalyst system, Q1 together with Q2, and in the case of a compound of general formula (II) Q3 together with Q4, preferably represent an optionally substituted hydrocarbylene group. The general hydrocarbylene group comprises at least 5 atoms in the ring and preferably contains from 6 to 9 atoms in the ring. More preferably, the cyclic group contains 8 ring atoms. The substituents, if any, are alkyl groups having 1 to 4 carbon atoms. As a rule, all ring atoms are carbon atoms, although divalent cyclic groups containing one or two heteroatoms in the ring, such as oxygen or nitrogen atoms, are not excluded. Examples of suitable divalent cyclic groups are 1,4-cyclohexylene, 1,4-cycloheptylene, 1,3-cycloheptylene, 1,2-cyclooctylene, 1,3-cyclooctylene, 1,4-cyclooctylene, 1,5-cyclooctylene. , 2-methyl-1, 5-cyclooctylene, 2,6-dimethyl-1,4-cyclooctylene and 2,6-dimethyl-1,5-cyclooctylene. The preferred metal complexing compounds of formula (II) are 1,2-bis (1, -cyclooctylenphosphine) -ethane, 1,2-bis (1,5-cyclooctylenphosphine) ethane and mixtures thereof. For the preparation of these compounds, reference is made to known techniques, for example the method described in GB-A-1,127,965.

The amount in which the catalyst system is used, not critical may vary within wide limits. The usual amounts range from 10 ~ 8 to 10"1, preferably from 10" 7 to 10"2 mol metal atom of the platinum group per mole of ethylenically unsaturated compound The amounts of the participants in the catalyst system are selected conveniently, so that per mol metal atom of the platinum group are used from 0.5 to 10, preferably from 1 to 6 moles of compound ligand that complexes metal, and from 0.5 to 15, preferably from 1 to 8 moles of anion source as a complex anion source Typically, the hydrogenolysis process is carried out under an atmosphere that comprises or is composed of hydrogen gas, for example, an atmosphere of carbon monoxide and hydrogen is very suitable These gases can be present in equimolar or non-equimolar ratios, for example in a ratio within the range of 5: 1 or 1: 5. Hydrogenolysis can be carried out at moderate reaction conditions. and they recommend temperatures in the range of 50 to 250 ° C, with temperatures in the range of 70 to 200 ° C being preferred. Reaction pressures in the range of 5 to 100 bar are preferred. Lower or higher pressures may be selected, but are not considered particularly advantageous. In addition, higher pressures require the provision of special equipment. In the process of the invention, the initial material and the formed product can act as a reaction diluent. Consequently, the use of a separate solvent is not necessary. However, the hydrogenolysis reaction is conveniently carried out in the additional presence of a solvent. As such, saturated hydrocarbons are recommended, for example paraffins and isoalkanes and further alcohols, preferably having from 3 to 10 carbon atoms per molecule, such as propanol, butanol, ethylenehexanol-1, nonanol-1, or general terms alcohols formed as products of hydrogenolysis, ethers such as 2, 5, 8-trioxanonane (diglyme), diethyl ether and anisole, and ketones, such as methylbutyl ketone. A particularly suitable solvent or cosolvent is water. Solvents that comprise or consist substantially of sulfones are also very suitable. Particularly preferred sulfones are, for example, dialkylsulfones such as dimethylsulfone and diethylsulfone and cyclic sulfones, such as sulfolane (tetrahydro-thiophene-2, 2-dioxide), sulfolene, 2-methylsulfolane and 2-methyl-4-ethylsulfolane. Mixtures of solvents, for example a mixture of a sulfone with a protic solvent, such as an alcohol or water, can also be used.

The amount of solvent to be used in the process of the invention can vary considerably. The experimental results provided hereinafter are indicative of the amount of solvent to be preferably used. The invention will now be illustrated by the non-limiting examples, as described hereinafter. The abbreviations used in the tables have the following meanings: BCPE = 1, 2-bis (1, 5-cyclooctylenphosphino) ethane BBPE = 1, 2-bis (sec-butylphosphino) ethane MSA = methanesulfonic acid TSFA = trifluoromethanesulfonic acid Examples 1 to 5 The experiments were carried out in a magnetic stirring autoclave of 250 ml. The autoclave was charged with 30 ml of glycerol, sulfolane and water in the amounts described in the Table, 0.25 mmol of palladium (II) acetate, 0.6 mmol of complexing compound and anions again in the amounts described in the table. After being thoroughly washed, the autoclave was pressurized. Subsequently, the reactor was sealed and the content was heated to the pre-established temperature and maintained at that temperature for 10 hours. After cooling, a sample of the reactor contents was taken and analyzed by gas and liquid chromatography. Additional details and the results of the analysis can be found in the Table. The calculated conversion rate was expressed as moles of product per mol metal atom of the platinum group and per hour, (mol / mol.h).

Comparative Example 1 The experiment was carried out substantially according to the procedure described above, using, however, 1.0 g of a heterogeneous catalyst of Pd on carbon (10% Pd on C, ex Janssen Chimica), 40 ml of glycerol and one pure hydrogen gas atmosphere (which should give a better performance). The results are also shown in the Table.

Comparative Example 2 The experiment was carried out substantially according to the procedure described above, using, however, 1.0 g of a heterogeneous Ru-carbon catalyst (5% of Ru on C, ex Janssen Chimica), 40 ml of glycerol and an atmosphere of pure hydrogen gas. The results are also shown in the Table.

Comparative Examples 3 and 4 The experiment was carried out substantially according to the procedure described in Example 1 of US Pat. No. 4,662,394 to the conditions mentioned above. The autoclave was charged with 50 ml of l-methyl-2-pyrrolidinone, 20 ml of glycerol, 0.58 mmol of Rh (CO) 2 acetylacetonate, and 4 mmol of H2W04. The reaction was heated to about 150 ° C and maintained at 60 bar of 1: 2 synthesis gas (C0: H2). Only traces of acrolein could be detected 15 hours later. When the metal of Group 10 was replaced by acetylacetonate by Pd (CO) 2, no products could be detected at all.

Conclusions Although not optimized, the examples according to the invention work as comparative examples. Other observations can be made related to the compound that complexes metal. Thus, the preferred BCPE gives a catalytic system with a higher speed than the one based on BBPE. The acidity of the anion source affects the speed and selectivity of acrolein. The speed is also improved by the presence of halide anions. While the amount of water that allows some control with respect to selectivity. < -p l-1 O cp O Cp Table I) A = acrolein; B = 1-propanol; C = 1,2-propanediol; D = 1, 3- propanediol It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (10)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. A process for the catalytic hydrogenolysis of glycerol, characterized in that it is carried out in the presence of a homogeneous catalyst which is based on a metal of the platinum group or a compound of a metal of the platinum group, a source of anions, and a metal-forming compound. pnetal complex of the formula Q1Q2MQ3 (I) or Q1Q2MQMQ3Q4 (II) characterized M represents phosphorus, arsenic or antimony, Q where a group that is covalently bound to both M and that has at least two atoms in the bridge and Q1 to Q4 are independently similar or different optionally substituted hydrocarbyl groups or Q1 and Q2 and / or Q3 and Q4 represent similar or different optionally substituted hydrocarbylene groups.

2. The process according to claim 1, characterized in that the metal of the platinum group is platinum or palladium.

3. The process according to claim 1 or 2, characterized in that acids having a pKa value of less than 3, measured in aqueous solution at 18 ° C, are used as the source of anions.

4. The process according to any of claims 1 to 3, characterized in that it is carried out in the presence of a catalyst system comprising halide anions as a source of anions.

5. The process according to any of claims 1 to 4, characterized in that (each) M in the phosphorus metal complex forming group.

6. The process according to any of claims 1 to 5, characterized in that a compound that forms a metal complex of formula (II) is used. The process according to any of claims 1 to 6, characterized in that Q1 together with Q2, and in the case of a compound of general formula (II) Q3 together with Q4, represent an optionally substituted hydrocarbylene group. 8. The process according to any of claims 1 to 7, characterized in that it is carried out at a temperature in the range of 50 to 250 ° C. 9. The process according to any of claims 1 to 8, characterized in that it is carried out at a pressure in the range of 5 to 100 bar. The process according to any of claims 1 to 9, characterized in that it is carried out in the presence of sulfolane, water, or a mixture thereof.