CN1380141A - Homogeneous carbonylation reaction catalyst and its preparation and application - Google Patents

Abstract

The present invention discloses a hologeneous carbonylation reaction catalyst. Said catalyst is an chelating type cis-dicarbonyl rhodium coordination compound which uses organic metal lithium as ligand and is formed into square plane with rhodium carbonyl. Said invention also provides chemical structure formula of said coordination compound. Based on the synergistic effect of metal rhodium and metal lithium combined with carboxylic acid by means of ionic bond the terminal carbonyl group of metal rhodium is activated, and the activity of the catalyst also is raised, and its stability is high. Said invention also discloses its preparation method and its application for catalyzing carbonylation of methyl alcohol to prepare acetic acid and methyl acetate and catalyzing reaction of methyl acetate of prepare ethyl anhydride.

Description

A kind of homogeneous carbonylation reaction catalyst and its preparation method and application

The invention relates to a catalyst for homogeneous carbonylation reaction and a preparation method thereof, and also relates to its application in catalyzing the carbonylation of methanol into acetic acid and methyl acetate and in catalyzing the reaction of methyl acetate into acetic anhydride.

Under the action of a catalyst, the carbonylation of methanol to produce acetic acid is an important technical route in the acetic acid industry. In the homogeneous methanol carbonylation reaction catalyzed by soluble small molecule rhodium complexes, the active species is usually rhodium monodentate complexes, such as: [Brodrk.D.Ledere.C; Benise.B; Pannetier Gi bull.Soc Chim , Fr.1976.61], or diiodide rhodium dicarbonyl structural forms such as: the small molecule rhodium complex rhodium dicarbonyl diiodide rhodium [Rh(CO) ₂ I ₂ ] ^- N ⁺ _R4 [Roth, JF, et al. Chem technol 1971, 600]. Because the monodentate rhodium complex is unstable, when the reaction temperature exceeds 180 ° C, it begins to decompose and deactivate, and dicarbonyl diiodo rhodium (I) is easily converted into dicarbonyl tetraiodo rhodium (III) anion complex during the reaction , and lose catalytic activity, especially so under the high temperature that is conducive to reaction, therefore in production process, except keeping the partial pressure of carbon monoxide, also need to add excessive hydrogen iodide to keep catalyzer to exist with rhodium (I) state, like this It greatly increases the corrosion effect on production equipment.

To solve the above problems, the object of the present invention is to provide a homogeneous carbonylation catalyst with high catalytic activity and stability.

Another object of the present invention is to provide a method for preparing a homogeneous carbonylation catalyst.

The purpose of the present invention is also to provide a kind of homogeneous carbonylation reaction catalyst in catalyzing methanol carbonylation to be acetic acid and methyl acetate and in catalyzing methyl acetate to be the application in acetic anhydride reaction, reaction system need not add hydroiodic acid, can reduce Corrosive effect on production equipment.

A kind of homogeneous carbonylation reaction catalyst of the present invention, form the chelating type cis-dicarbonyl rhodium (I) complex of square plane with organometallic lithium as ligand and carbonyl rhodium (I), its structural formula is as follows:

In the formula, X ^- is BPh ₄ ^- , BF ₄ ^- , CH ₃ COO ^- or OH ^- ; n=0,1,2,3,4.

The organometallic lithium ligand refers to the lithium salt of a dicarboxylic acid containing two carboxyl groups, and its structural formula is as follows:

In the formula n=0 1,2,3,4. For example: lithium oxalate, lithium malonate, lithium succinate, lithium glutarate, etc.

Catalyst of the present invention has following characteristics:

1. Since the ligand contains two coordinating oxygen atoms, two coordinating bonds are formed with metal rhodium during the formation of the complex. These two coordinating oxygen atoms are connected with a certain flexible carbon chain to form a bidentate Coordinated chelating square planar bimetallic complexes.

2. The complex has relatively good stability and can be prepared without the protection of inert gas. Electron Spectroscopy (XPS) research shows that there are two O→Rh coordination bonds. Infrared spectroscopy shows that there is a characteristic absorption peak of the terminal carbonyl of the rhodium complex between 2000 and 2100 cm ^-1 , indicating that this type of complex contains cis - dicarbonyl structure.

3. Due to the chelating structure formed in the complex and the existence of two weaker O→Rh bonds, the catalyst system is beneficial to complete the addition of co-catalyst methyl iodide in the reaction.

4. Since the catalyst contains two metals, i.e. rhodium metal and lithium metal ionically bonded to carboxylic acid, the synergistic effect between the two metals activates the terminal carbonyl group of rhodium metal, thereby improving the catalytic activity. active.

5. Due to the high catalytic activity and stability of the catalyst, the reaction conditions of methanol carbonylation reaction are extremely mild. The reaction system does not need to add polar solvents such as hydroiodic acid, only methyl acetate, acetic acid, acetic anhydride, water, etc. as a solvent.

The preparation method of a kind of homogeneous carbonylation reaction catalyst of the present invention, carries out according to the following steps successively:

a. Preparation of organometallic lithium ligand 1 molar part of malonic acid and 1 to 10 molar parts of lithium hydroxide monohydrate are dissolved in 10 to 100 molar parts of methanol or aqueous solution, and reacted for 10 to 60 minutes under stirring, Precipitate with excess ether, filter, wash and dry; the molar ratio of malonic acid and lithium hydroxide monohydrate is preferably 1:2.

b. Preparation of monodentate catalysts

① 1 mole part of the ligand is dissolved in 10-100 mole parts of methanol,

②Add dropwise methanol solution containing 0.01~1 mole parts rhodium carbonyl while stirring at 0~50°C. The molar ratio of methanol to rhodium carbonyl is 50~100:1. A single-dentate catalyst is obtained; the rhodium carbonyl is Rh ₂ (CO) ₄ Cl ₂ , Rh ₂ (CO) ₄ Br ₂ or Rh ₂ (CO) ₄ I ₂ .

c. the preparation of cis dicarbonyl rhodium complex catalyst is then added dropwise to the methanol solution containing 1 to 10 mole parts of precipitant, the molar ratio of methanol to precipitant is 5 to 50: 1, the rhodium complex is precipitated and separated out completely, suction filtered, The obtained solid is repeatedly washed with methanol or ether equal to or lower than 0°C, and then dried under reduced pressure at 0-50°C to constant weight to obtain a maximum of 100% cis-dicarbonyl double metal complex. The precipitating agent is anion alkali metal sodium or potassium salt or alkali metal hydroxide with BPh ₄ ^- , BF ₄ ^- , CH ₃ COO ^- . The share ratios in steps a and b above are not comparable, and the share ratios in steps b and c are comparable.

Taking the lithium malonate ligand as an example, the formation process of the cis-dicarbonyl double metal complex chelate structure catalyst is as follows:

The application of the homogeneous carbonylation reaction catalyst of the invention in the reaction of catalyzing the carbonylation of methanol into acetic acid and methyl acetate. Add methanol, methyl iodide and the catalyst of the present invention respectively in the reaction device, their molar ratio is 1: 0.1～0.5: 0.001～0.0001, fully mix and charge carbon monoxide, the reaction temperature is 150～200 ℃, and the reaction pressure is 20～40kg /cm ² , and the reaction time is 1 to 5 hours. Before charging carbon monoxide, acetic acid, acetic anhydride, water, methyl acetate, etc. can also be added in a molar ratio of 0.2 to 1:1 with methanol. The reaction conditions are relatively mild, and only methyl iodide is used as a cocatalyst without adding hydroiodic acid.

The application of a homogeneous carbonylation reaction catalyst of the present invention in catalyzing the reaction of methyl acetate into acetic anhydride. Add methyl acetate, methyl iodide and the catalyst of the present invention into the reactor, their molar ratio is 1:0.1～0.5:0.001～0.0001, mix well and charge carbon monoxide, the reaction temperature is 170～200°C, and the reaction pressure is 20～ 40kg/cm ² , the reaction time is 1-5 hours. Before charging carbon monoxide, acetic acid, acetic anhydride, methyl acetate, etc. may be added in a molar ratio of 0.2 to 1:1 to methyl acetate. A large number of experimental data show that the catalyst has high catalytic activity for the formation of acetic anhydride.

This type of catalyst catalyzes the carbonylation reaction of methanol or methyl acetate to prepare acetic acid and acetic anhydride. The reaction mechanism is as follows:

(1)

(2)

(3)

(4)

(5)

(6)

The present invention will be further described below in conjunction with embodiment.

Example 1:

Weigh 0.005 mol of oxalic acid and 0.01 mol of lithium hydroxide monohydrate and dissolve in 0.3 mol of methanol, react for 20 minutes under stirring, precipitate with excess ether, filter, wash, and dry to obtain the ligand. Dissolve 0.005 mole of ligand in 0.2 mole of methanol, add dropwise a solution of 0.0025 mole of tetracarbonyl dirhodium dichloride in methanol (0.25 mole of methanol) at 25°C, and continue stirring for 20 minutes to dissolve 0.005 mole of tetraphenyl Boron sodium methanol solution was added (0.1 mole of methanol), and after 10 minutes of reaction, the rhodium complex precipitated completely and was suction filtered. The obtained solid was washed twice with methanol at 0°C, and dried under reduced pressure at room temperature to constant weight to obtain the bidentate complex. finished catalyst.

Example 2:

Weigh 0.01 mol of malonic acid and 0.02 mol of lithium hydroxide and dissolve in 0.8 mol of water, react for 15 minutes under stirring, precipitate with excess ether, filter, wash, and dry to obtain the ligand. Dissolve 0.01 mole of ligand in 0.5 mole of methanol, stir and dropwise add 0.005 mole of tetracarbonyl dirhodium dichloride in methanol (0.25 mole of methanol) at 20°C, continue stirring for 20 minutes, and dissolve 0.01 mole of fluoroboric acid Add methanol solution of sodium (methanol is 0.2 mol), react for 10 minutes, the rhodium complex precipitates out completely, filter with suction, wash the solid obtained twice with methanol at 0°C, dry under reduced pressure at room temperature to constant weight, and obtain the bidentate complex finished catalyst.

Example 3:

Weigh 0.005 mol of succinic acid and 0.01 mol of lithium hydroxide monohydrate and dissolve in 0.5 mol of methanol, react under stirring for 20 minutes, precipitate with excess ether, filter, wash, and dry to obtain the ligand. Dissolve 0.005 mole of ligand in 0.1 mole of methanol, stir and dropwise add 0.0025 mole of tetracarbonyl dirhodium dichloride in methanol solution (0.2 mole of methanol) at 25 ° C, continue stirring for 20 minutes, and dissolve 0.005 mole of fluoroboric acid Add sodium methanol solution (methanol is 0.1 mol), react for ten minutes, the rhodium complex precipitates out completely, filter with suction, the obtained solid is washed twice with 0 ℃ methanol, and dried under reduced pressure at room temperature to constant weight to obtain bidentate coordination Finished catalyst.

Example 4:

Weigh 0.005 mol of glutaric acid and 0.01 mol of lithium hydroxide monohydrate and dissolve in 0.5 mol of methanol, react under stirring for 20 minutes, precipitate with excess ether, filter, wash, and dry to obtain the ligand. Dissolve 0.005 mole of ligand in 0.2 mole of methanol, stir and dropwise add 0.0025 mole of tetracarbonyl dirhodium dichloride in methanol (0.15 mole of methanol) at 20°C, continue stirring for 20 minutes, and dissolve 0.005 mole of fluoroboric acid Add sodium methanol solution (methanol is 0.05 mol), react for ten minutes, the rhodium complex precipitates out completely, filter with suction, the obtained solid is washed twice with 0 ℃ methanol, and dried under reduced pressure at room temperature to constant weight to obtain bidentate coordination Finished catalyst. Example 5:

Weigh 0.01 mol of adipic acid and 0.02 mol of lithium hydroxide monohydrate and dissolve in 0.5 mol of methanol, react for 20 minutes under stirring, precipitate with excess ether, filter, wash, and dry to obtain the ligand. Dissolve 0.01 mole of ligand in 0.2 mole of methanol, stir and dropwise add 0.005 mole of tetracarbonyl dirhodium dichloride in methanol solution (0.3 mole of methanol) at 20°C, continue stirring for 20 minutes, add 0.01 mole of potassium acetate Add methanol solution (methanol is 0.1 mol), react for 10 minutes, the rhodium complex precipitates out completely, filter with suction, wash the obtained solid twice with methanol at 0°C, dry under reduced pressure at room temperature to constant weight, and obtain a bidentate coordination catalyst finished product.

Embodiment 6:

In a 250ml reactor, add 4× ^10-4 moles of the catalyst in Example 1, 2 moles of methanol, and 0.4 moles of methyl iodide, and rinse the reactor with carbon monoxide for 3 times, keeping the reaction temperature at 170°C and the constant pressure of CO at 3.0MPa , the stirring speed was 450 rev/min, and the reaction was carried out for 1 hour, the conversion rate of methanol was 91%, the yield of methyl acetate was 15.2%, and the yield of acetic acid was 62.1%.

Embodiment 7:

In a 250ml reactor, add 4.5× ^10-4 moles of the catalyst in Example 2, 2 moles of methanol, 0.4 moles of methyl iodide, and 0.3 moles of acetic acid, and rinse the reactor 3 times with carbon monoxide to keep the reaction temperature at 180°C. Constant pressure 3.0MPa, stirring speed 550 rev/min, reaction for 1 hour, the conversion rate of methanol was 94.6%, the yield of methyl acetate was 10.4%, and the yield of acetic acid was 68.3%.

Embodiment 8:

In a 250ml reactor, add 5× ^10-4 moles of the catalyst in Example 1, 1 mole of methyl acetate, 0.3 moles of methyl iodide, and 0.6 moles of acetic acid, purging the reactor 3 times with carbon monoxide, and keeping the reaction temperature at 180°C , CO constant pressure 3.0MPa, H ₂ constant pressure 0.5MPa, stirring speed 500 rpm, reaction for 1 hour, the conversion rate of methyl acetate was 60.4%, the yield of acetic acid was 12.3%, and the yield of acetic anhydride was 48.1%.

Embodiment 9:

In a 250ml reactor, add 6× ^10-4 moles of the catalyst in Example 2, 1 mole of methyl acetate, 0.3 moles of methyl iodide, and 0.6 moles of acetic acid, purging the reactor 3 times with carbon monoxide, and keeping the reaction temperature at 170°C , CO constant pressure 3.0MPa, H ₂ constant pressure 0.5MPa, stirring speed 600 rev/min, reaction for 1 hour, the conversion rate of methyl acetate was 62.4%, the yield of acetic acid was 14.5%, and the yield of acetic anhydride was 43.6%. Example 10:

In a 250ml reactor, add 7× ^10-4 moles of the catalyst in Example 3, 1 mole of methyl acetate, 0.3 moles of methyl iodide, and 0.7 moles of acetic acid, purging the reactor 3 times with carbon monoxide, and keeping the reaction temperature at 185°C , CO constant pressure 3.0MPa, H ₂ constant pressure 0.5MPa, stirring speed 600 rpm, reaction for 1 hour, the conversion rate of methyl acetate was 71.5%, the yield of acetic acid was 8.6%, and the yield of acetic anhydride was 50.7%.

Claims (5)

1. a kind of homogeneous carbonylation reaction catalyzer, is that ligand and carbonyl rhodium form the chelating type cis dicarbonyl rhodium (I) complex of square plane with organometallic lithium, and its structural formula is as follows:

In the formula, X ^- is BPh ₄ ^- , BF ₄ ^- , CH ₃ COO ^- or OH ^- ; n=0,1,2,3,4. 2. A homogeneous carbonylation catalyst according to claim 1, characterized in that said organometallic lithium is lithium oxalate, lithium malonate, lithium succinate, lithium glutarate, lithium adipate. 3. A method for preparing a homogeneous carbonylation catalyst, which is carried out in the following steps: a. Preparation of organometallic lithium ligand 1 molar part of malonic acid and 1 to 10 molar parts of lithium hydroxide monohydrate are dissolved in 10 to 100 molar parts of methanol or aqueous solution, and reacted for 10 to 60 minutes under stirring, Precipitate with excess ether, filter, wash, and dry; b. Preparation of monodentate catalysts ① 1 molar part of the ligand is dissolved in 10-100 molar parts of methanol; ②Add dropwise methanol solution containing 0.01~1 mole parts rhodium carbonyl while stirring at 0~50°C. The molar ratio of methanol to rhodium carbonyl is 50~100:1. A monodentate structure catalyst is obtained; the rhodium carbonyl is Rh ₂ (CO) ₄ Cl ₂ , Rh ₂ (CO) ₄ Br ₂ or Rh ₂ (CO) ₄ I ₂ ; c. the preparation of cis dicarbonyl rhodium complex catalyst is then added dropwise to the methanol solution containing 1 to 10 mole parts of precipitant, the molar ratio of methanol to precipitant is 5 to 50: 1, the rhodium complex is precipitated and separated out completely, suction filtered, The obtained solid is repeatedly washed with methanol or ether equal to or lower than 0°C, and then dried under reduced pressure at 0-50°C to constant weight; the precipitant is an anion base with BPh ₄ ^- , BF ₄ ^- , CH ₃ COO ^- Sodium or potassium metal salts or alkali metal hydroxides. 4. The application of a homogeneous carbonylation catalyst in catalyzing the carbonylation of methanol into acetic acid and methyl acetate. 5. The application of a homogeneous carbonylation catalyst in catalyzing the reaction of methyl acetate into acetic anhydride.