CN1349855A

CN1349855A - Bimetallic catalyst for homogeneous methanol carbonylation and its prepn

Info

Publication number: CN1349855A
Application number: CN 00130033
Authority: CN
Inventors: 袁国卿; 潘平来; 邹瑾
Original assignee: Institute of Chemistry CAS
Current assignee: Institute of Chemistry CAS
Priority date: 2000-10-24
Filing date: 2000-10-24
Publication date: 2002-05-22
Anticipated expiration: 2020-10-24
Also published as: CN1117628C

Abstract

The invention relates to a homogeneous carboxylation reaction bimetal catalyst. It is a cis-dicarbonyl lawrencium and lithium dimetal compound. In said catalyst the cocatalyst assistant and polar solvent can be added to form a catalytic system, under the condition of moderate reaction said catalytic system can quickly catalyze methyl alcohol to implement carboxylation to obtain acetic acid and methyl acetate or catalyze methyl acetate to obtain acetic anhydride. Said catalyst possesses good activity and stability.

Description

Bimetallic catalyst for homogeneous methanol carbonylation and method for making thereof

The present invention relates to a kind of equal bimetallic catalysts that is used for methanol carbonylation and preparation method thereof.This catalyzer has very high catalytic activity and selectivity to methanol carbonylation.

At the beginning of 1970's, U.S. Monsanto Company has developed low-pressure process methyl alcohol carbonylation system acetic acid technology, and has successfully realized industrialization, is the important technology route of present acetic acid industry.Its reaction process is the effect that methyl alcohol passes through rhodium catalyst, prepares acetate with reaction of carbon monoxide, and catalyzer adopts anionic small molecules rhodium complex as [Rh (CO) ₂I ₂] ^-NR ₄ ⁺,

[Roth，J.F.et?al.Chem.Technol，1971，600]。Because this class rhodium active specy is unstable in reaction, is easy to be converted in reaction process dicarbapentaborane tetraiodo rhodium (III) [Rh (CO) ₂I ₄] ^-Anionic complex, and lose catalytic activity, helping reacting all the more so under the high temperature that carries out.Therefore in actual production, general employing keeps the dividing potential drop of carbon monoxide and adds excessive hydrogen iodide existing with protection rhodium (I) state, but this has greatly increased the corrodibility of reaction medium to equipment again.

At existing catalyzer these deficiencies in reaction process, people wish to find a kind of catalyzer of more excellent performance, and promptly catalyzer has the highly active while, has better stability.The catalyzer that Britain BP company uses in recent years becomes iridium catalyst systems [EP849249,19 Dec 1996] by original rhodium catalytic system, has obtained certain effect, makes catalyst performance that great improvement arranged.

Institute of Chemistry, Academia Sinica, once having proposed a kind of organometallics that contains nitrogen, oxygen is part, forms the chelating type of new square plane along the dicarbapentaborane bimetal complexes with rhodium carbonyl.[Chinese patent 1105603A] this system can be used for the catalysis methanol carbonyl and turns to acetate and methyl acetate, also can be used for the catalysis methyl acetate and obtains diacetyl oxide.

The purpose of this invention is to provide a kind of bimetallic catalyst for homogeneous methanol carbonylation, the chelating type that it is characterized in that having N and O atom metal lithium organic ligand along dicarbapentaborane rhodium cationic structural catalyzer or with N be the monodentate coordination of ligating atom along dicarbapentaborane rhodium structure catalyst, its structure is as follows:

R is H in the formula, carboxylic hydrocarbon derivative; (X ^-) be BPh ₄ ^-, BF ₄ ^-Or CH ₃COO ^-X is I, Cl or Br; N=0,1 or 2.

In the bimetallic catalyst of the invention described above, described N of having and O atom metal lithium organic ligand are meant the lithium salts of the pyridine derivate that contains carboxyl, and its ligand structure is as follows:

R is H or carboxylic hydrocarbon derivative in the formula, and n is 0,1 or 2.Wherein, preferably R is H, for example, and pyridine-2-lithium formate, Nicotinicum Acidum lithium, pyridine-4-lithium formate, pyridine-2-lithium acetate, pyridine-3-lithium acetate, pyridine-4-lithium acetate or than pyridine-3-propionic acid lithium etc.

The catalyst system that is used for methanol carbonylation of the present invention is made up of above-mentioned bimetallic catalyst, promotor and polar solvent three parts.

So-called promotor is meant methyl iodide and hydroiodic acid HI.

And employed polar solvent is meant acetate, acetic anhydride, water, methyl acetate etc. in reaction system.

Catalyzer of the present invention has following technical characterictic:

1. owing to contain the different coordination electron donor of two kinds of powers of N, O in the part, in this catalyst system, form two kinds of different coordinate bonds of power with metal, the donor atom of strong coordination ability links to each other by certain flexible carbochain with the donor atom of weak coordination ability, has formed the bimetal complexes of the square plane of the chelating type that has strong and weak metal-complexing key simultaneously.

Since in the title complex chelating type unsymmetric structure that forms and strong N → Rh join the existence that key, weak O → Rh are joined key, make catalyst system have good thermostability.

3. in reaction medium, be easy to disassociation because weak O → Rh joins key, make the center rhodium atom of active specy be in the coordination undersaturated condition, be convenient to CH ₃I oxidation addition, weak ligating atom still are in the coordination scope of rhodium after its coordination disassociation owing to the existence of chelating chain, after treating that the oxidation addition process finishes, form O → Rh again and join key, finish a catalytic cycle, show good catalytic activity and stability.

4. owing to contain two kinds of metals in this catalyst system, promptly metal rhodium and with carboxylic acid with ionic linkage bonded metallic lithium, the synergistic effect between two kinds of metals makes the terminal carbonyl of metal rhodium obtain activation, thereby has improved activity of such catalysts and stability.

The preparation of bimetallic catalyst of the present invention is by following step:

1. make the reaction of above-mentioned pyridine derivate part and rhodium carbonyl compound, wherein the ratio of rhodium carbonyl and part is 1: 1-5, and be reflected at 0-50 ℃ and carry out, can obtain the monodentate coordination along dicarbapentaborane rhodium structure catalyst;

2. after above-mentioned steps 1, add precipitation agent, wherein the precipitation agent consumption be rhodium carbonyl 1.5-10 doubly, can obtain the coordination of bidentate chelating along dicarbapentaborane rhodium structure catalyst synthermal the reaction down.

The concrete method for making of catalyzer of the present invention is as follows: 0.01 mole part is dissolved in 10～100 moles the methyl alcohol or other solvents, 0～50 ℃ while stirring Dropwise 5～30ml be dissolved with the methanol solution of 0.005 mole of rhodium carbonyl (methyl alcohol: the rhodium carbonyl mol ratio be 50～100: 1), after dropwising, isothermal reaction 5～120 minutes can get the monodentate structure catalyst.As being added dropwise to 5～50% methanol solutions (or aqueous solution) that contain 0.02 mole of precipitation agent again, make the rhodium complex precipitation separate out complete, suction filtration, the gained solid is with 0 ℃ of methyl alcohol (or water) repetitive scrubbing, at room temperature drying under reduced pressure can obtain 100% suitable dicarbapentaborane bimetal complexes at most to constant weight then.With pyridine-2-lithium formate part is example, as follows along the forming process of dicarbapentaborane bimetal complexes chelate structure catalyzer and monodentate structure catalyst:

In above-mentioned preparation method, the rhodium compound that uses is Rh (CO) ₄Cl ₂, Rh ₂(CO) ₄Br ₂Or Rh ₂(CO) ₄I ₂

In addition, in above-mentioned preparation method, selected precipitation agent is to have BPh ₄ ^-, BF ₄ ^-, CH ₂COO ^-The negative ion alkali metallic sodium or the salt of potassium make precipitation agent.

Adopt this catalyst carbonylation of methanol can obtain acetate and methyl acetate.1) and this catalyzer (their mol ratio is 5～8:, charge into carbon monoxide behind the thorough mixing, temperature of reaction is 150～200 ℃, reaction pressure 20～40kg/cm to add methyl alcohol, methyl iodide in reaction unit respectively ²Reaction conditions is gentle relatively, only uses the promotor methyl iodide and need not to add hydroiodic acid HI.

Use this catalyzer to obtain diacetyl oxide by the catalysis methyl acetate.Methyl acetate, methyl iodide (in molar ratio) and this catalyzer join in the reactor, charge into carbon monoxide after mixing, and temperature of reaction is 170～200 ℃, reaction pressure 20～40kg/cm ²A large amount of experimental datas show that this catalyzer has advantages of high catalytic activity to the generation of diacetyl oxide.

Give further detailed explanation below by embodiment to technology of the present invention.

Embodiment 1

Taking by weighing equimolar pyridine-2-formic acid and lithium hydroxide is dissolved in the methyl alcohol, under agitation back flow reaction is 1 hour, be cooled to room temperature, add four carbonyl dichloros, two rhodiums that are equivalent to pyridine-2-formic acid  mole, continue to stir 20 minutes, with being same as the sodium tetraphenylborate methanol solution adding of mole numbers such as four carbonyl dichloros, two rhodiums, react after ten minutes, get lemon yellow throw out 0C with excessive ether sedimentation ⁰Methanol wash twice, reduced pressure at room temperature obtain the catalyzer finished product of double coordination to constant weight.

Embodiment 2

Take by weighing equimolar Nicotinicum Acidum and lithium hydroxide, be dissolved in the methyl alcohol, under agitation back flow reaction is 1 hour, be cooled to room temperature, add four carbonyl dichloros, two rhodiums that are equivalent to Nicotinicum Acidum  mole, continue to stir 20 minutes, will be same as the sodium acetate methanol solution adding of mole numbers such as four carbonyl dichloros, two rhodiums, react after ten minutes, with excessive ether sedimentation filter throw out 0C ⁰Methanol wash twice, reduced pressure at room temperature obtain the catalyzer finished product of double coordination to constant weight.

Embodiment 3

Take by weighing equimolar pyridine-4-formic acid and lithium hydroxide and be dissolved in the methyl alcohol, under agitation back flow reaction is 1 hour, is cooled to room temperature, add four carbonyl dichloros, two rhodiums that are equivalent to pyridine-4-formic acid  mole, continue to stir 20 minutes, use excessive ether sedimentation, throw out is used 0C after filtering ⁰Methanol wash twice, reduced pressure at room temperature obtain monodentate coordinate catalyzer finished product to constant weight.

Embodiment 4

In the 250ml reactor, add the catalyzer 0.5g among the embodiment 1, methyl alcohol 100ml, methyl iodide 25ml, with air in the CO displacement still, keeping temperature of reaction is 180 ℃, CO constant voltage 3.0MPa, 450 rev/mins of stirring velocitys, reacted 1.5 hours, methanol conversion 96.1%, methyl acetate yield 20.9%, acetic acid yield 60.2%.

Embodiment 5

In the 250ml reactor, add the catalyzer 0.5g among the embodiment 2, methyl alcohol 100ml, acetate 20ml, methyl iodide 25ml is with air in the CO displacement still, keeping temperature of reaction is 175 ℃, CO constant voltage 3.0MPa, 500 rev/mins of stirring velocitys are reacted after 1.5 hours, methanol conversion 92.5%, methyl acetate yield 17.0%, acetic acid yield 55.2%, the acetate increment is 40.3%.

Embodiment 6

In the 250ml reactor, add the catalyzer 0.55g of embodiment 3, methyl acetate 80ml, acetate 40ml, methyl iodide 20ml, with air in the CO displacement still, keeping temperature of reaction is 180 ℃, CO constant voltage 3.0MPa, 500 rev/mins of stirring velocitys were reacted after 1.5 hours, and the methyl acetate transformation efficiency is 72.3%, acetic acid yield 10.03%, acetic anhydride yield 62.27%.

Embodiment 7

In the 250ml reactor, add the catalyzer 0.55g of embodiment 1, methyl acetate 80ml, acetate 40ml, methyl iodide 20ml, behind air in the CO displacement still, keeping temperature of reaction is 185 ℃, CO constant voltage 3.0MPa, 500 rev/mins of stirring velocitys were reacted after 1.5 hours, and the methyl acetate transformation efficiency is 72.78%, acetic acid yield 10.32%, acetic anhydride yield 62.46%.

Claims

1. A bimetallic catalyst for homogeneous methanol carbonylation, characterized in that there is a chelating type cis-dicarbonyl rhodium cationic structure catalyst with N and O atom metal lithium organic ligands or the monodentate coordination with N as a coordination atom Cis dicarbonyl rhodium structure catalyst, its structure is as follows:

In the formula, R is H, a carboxyl-containing hydrocarbon derivative; (X ^- ) is BPh ₄ ^- , BF ₄ ^- or CH ₃ COO ^- ; X is I, Cl or Br; n=0, 1 or 2.

2. homogeneous methanol carbonylation bimetallic catalyst as claimed in claim 1, it is characterized in that described have N and O atom metal lithium organic ligand and refer to the lithium salt of the pyridine derivative containing carboxyl, its ligand structure as follows:

In the formula, R is H or a carboxyl-containing hydrocarbon derivative, and n is 0, 1 or 2.

3. The homogeneous methanol carbonylation bimetallic catalyst as claimed in claim 2, characterized in that the ligand is: lithium pyridine-2-formate, lithium pyridine-3-formate, lithium pyridine-4-formate, pyridine - lithium 2-acetate, lithium pyridine-3-acetate, lithium pyridine-4-acetate or lithium pyridine-3-propionate.

4. A method for preparing a homogeneous carbonylation bimetallic catalyst, characterized in that rhodium carbonyl: ligand: the ratio of precipitant is 1: 2: 2 (molar ratio), and 1 mole of ligand is dissolved in 10 to 100 moles of In acetone and methanol, add dropwise a methanol solution in which rhodium carbonyl is dissolved while stirring at 0-40°C. Methanol:rhodium carbonyl is 50-100:1 (molar ratio). Add 2-10% precipitant in methanol solution, and after the product precipitates, filter it with suction, wash it repeatedly with methanol and ether at 0°C, and dry it under reduced pressure at room temperature to constant weight.

5. homogeneous carbonylation bimetallic catalyst preparation method as claimed in claim 4, it is characterized in that described ligand has N and O atom metal lithium organic ligand and refers to the lithium salt of the pyridine derivative containing carboxyl, its The ligand structure is as follows:

6. The method for preparing a homogeneous carbonylation bimetallic catalyst as claimed in claim 5, wherein said ligand is: lithium pyridine-2-formate, lithium pyridine-3-formate, lithium pyridine-4-formate, pyridine - Lithium 2-acetate, lithium pyridine-3-acetate, lithium pyridine-4-acetate, lithium pyridine-3-propionate, and the like.

7. The method for preparing a homogeneous carbonylation bimetallic catalyst as claimed in claim 4, characterized in that the precipitating agent is a sodium or potassium salt with negative ions of BPh ₄ ^- , BF ₄ ^- or CH ₃ COO ^- .

8. The use of the homogeneous carbonylation bimetallic catalyst as claimed in claim 1, characterized in that it can catalyze the carbonylation of methanol into acetic acid and methyl acetate. After methanol and methyl iodide are mixed in a ratio of 5 to 8: 1 (molar ratio), add the double metal complex catalyst as claimed in claim 1, charge carbon monoxide, and the reaction temperature is 150 to 200 ° C, and the carbon monoxide partial pressure during the reaction 20 to 40 kg/cm ² .

9. The use of the homogeneous carbonylation bimetallic catalyst as claimed in claim 1, characterized in that methyl acetate can be catalyzed to be acetic anhydride. After methyl acetate and methyl iodide are mixed in a ratio of 5 to 8: 1 (molar ratio), add the double metal complex catalyst as claimed in claim 1, charge into carbon monoxide, and the reaction temperature is 150 to 200° C. During the reaction, carbon monoxide The partial pressure is 20-40kg/cm ² .