CN112916049B - Oxygen-containing multidentate ligand-modified copper-based catalyst for acetylene hydrochlorination and its preparation method and application - Google Patents

Abstract

The invention relates to an oxygen-containing polydentate ligand modified copper-based catalyst for acetylene hydrochlorination and a preparation method and application thereof. The catalyst takes activated carbon as a carrier and copper salt as a main active component, and the catalytic activity and stability of the catalyst are improved by adding oxygen-containing polydentate ligands. The oxygen-containing polydentate ligand does not contain other heteroatoms except oxygen and can form a stable complex with copper; the copper salt is selected from one or more of copper chloride, copper bromide, copper nitrate and copper sulfate; the mass ratio of the copper element in the catalyst is 2.5-16%. Copper ions can be firmly combined with oxygen-containing polydentate ligands to prevent reduction to inactive zero-valent copper during the catalytic process. In addition, if the two are coordinated to form a five-membered cyclic complex, the electrons of the copper ions can be regulated and controlled, and the space distribution of the copper ions is more favorable for catalysis.

Description

Oxygen-containing multidentate ligand-modified copper-based catalyst for acetylene hydrochlorination and its preparation method and application

technical field

The invention belongs to the field of chemical catalysis, in particular to an oxygen-containing multidentate ligand-modified copper-based catalyst for acetylene hydrochlorination reaction, and a preparation method and application thereof.

Background technique

Polyvinyl chloride (PVC) is one of the top five general-purpose resins in the world and is widely used in many industries such as chemical industry, building materials, agriculture and medical equipment. In 2018, China's total PVC production capacity exceeded 24 million tons, accounting for more than 40% of the global PVC production capacity. It is estimated that by 2026, the total global PVC demand is expected to reach 56.2 million tons. The production of polyvinyl chloride (PVC) requires vinyl chloride monomer (VCM). In view of my country's special energy structure of "rich coal, lean oil, and less gas", our country chooses mature technology, low water consumption and low production cost. The basic acetylene production route, but the core link of this production route relies on mercury-containing catalysts. Polyvinyl chloride (PVC) production has become the industry with the largest mercury consumption in my country, accounting for more than 60% of the total mercury consumption in China.

The main active component of mercury-containing catalysts used in acetylene hydrochlorination in industry is HgCl ₂ , which is easily sublimated and lost at high temperatures, causing serious environmental pollution and serious harm to human health. With the official entry into force of the "Minamata Convention on Mercury" in China and other parties in 2017, the use of mercury-containing products will be strictly restricted. Since the 1970s, relevant researchers at home and abroad have started the research on mercury-free catalysts for acetylene hydrochloride. A large number of research results show that the mercury-free catalysts with industrial application conditions at this stage are mainly catalysts with noble metals (such as Au, Pt, Ru) as active components and non-precious metals (such as Cu, Sn, Bi) as active components. catalyst. Based on economy, non-precious metal mercury-free catalysts have ushered in a research upsurge in recent years, especially Cu-based catalysts, and a large number of literature and patent reports have appeared.

The invention patent with the publication number CN107008465B discloses a copper-based catalyst for acetylene hydrochlorination. The catalyst uses copper salt as an active component, and adds a stabilizer to improve the stability of the catalyst. The copper salt is selected from one or more of copper chloride, copper nitrate, copper sulfate and copper phosphate, and the stabilizer is selected from guanidine hydrochloride, tetramethylethylenediamine hydrochloride, tetramethylammonium chloride, tetraethylammonium chloride ammonium chloride, trimethylbenzylammonium chloride, triethylbenzylammonium chloride, tetramethylphosphonium chloride, tetrabutylphosphonium chloride, methyltriphenylphosphonium chloride, 1-butyl One or several kinds of triphenylphosphonium chloride, although the invention effectively improves the stability of the copper-based catalyst, the reaction activity is not improved, and the highest initial reaction activity is only 74%.

Application 201910933364.8 proposes a preparation method of a trivalent copper catalyst and its application in acetylene hydrochlorination. The catalyst preparation method comprises the following steps: adding nitrogen-containing heterocyclic compounds and copper salts into a chloroform solution and mixing to obtain a mixed solution containing divalent copper compounds; adding ionic liquid to the obtained mixed solution, under the action of an oxidant, to obtain a mixed solution containing a divalent copper compound; The mixed solution of trivalent copper compound; the porous solid carrier is immersed in the obtained mixed solution containing the trivalent copper compound for 0.5 to 5 hours, and then the treated solid is taken out and heated and dried under the condition of blue light irradiation, that is, the trivalent copper is obtained. catalyst. Although the catalyst has certain activity and stability in the reaction, the preparation process is cumbersome and difficult to industrialize production.

At present, the main difficulties of acetylene copper hydrochloride-based catalysts are that they have poor activity, poor stability or the preparation method is not easy for industrial production. Based on this background, the present application discloses a mercury-free catalyst for acetylene hydrochloride, which uses activated carbon as a carrier, copper salt as an active component, and uses oxygen-containing multidentate ligands to improve activity and stability. Green environmental protection, high industrial feasibility.

SUMMARY OF THE INVENTION

Aiming at the defects of the above-mentioned technologies and the deficiencies in industrial application, the present invention provides an oxygen-containing multidentate ligand-modified copper-based catalyst for acetylene hydrochlorination, and a preparation method and application thereof.

In view of the common problems of low activity and poor stability of current copper-based catalysts, we have found through a large number of experiments and studies that oxygen-containing multidentate ligands can make high-valent copper active species more stable and reduce the zero valence of reduction products in the catalytic process. formation of copper. According to the theory of soft and hard acid-base, the electron donors of carboxyl and hydroxyl groups are oxygen atoms, which are difficult to polarize and belong to hard bases. Copper ions are hard acids and can form stable complexes with hard bases. The oxygen atom of the electron donor can stably coordinate with the copper ion as the junction acid, so the copper ion can be firmly combined with the oxygen-containing multidentate ligand, preventing it from being reduced to inactive zero-valent copper during the catalytic process, thereby improving Activity and stability of copper-based catalysts. In addition, if the two are coordinated to form a five-membered cyclic complex, the electrons of copper ions can be regulated to tend to a more favorable spatial distribution for catalysis.

Oxygen-containing multidentate ligands refer to ligands containing two or more oxygens as coordination atoms in one ligand. There are 6 electrons around oxygen. After two of them form covalent bonds with carbon, there are also two lone pairs of electrons that can coordinate with transition metals. The oxygen atom in the furan ring, the carbonyl oxygen and the hydroxyl oxygen in the carboxyl group are all sp2 hybridized, and the oxygen of the alcoholic hydroxyl group is sp3 hybridized, but they can be used as coordination atoms. The oxygen-containing multidentate ligands involved in this patent do not contain heteroatoms other than oxygen.

The present invention is realized by the following method:

An oxygen-containing multidentate ligand-modified copper-based catalyst for acetylene hydrochlorination, the catalyst is composed of a copper salt, an oxygen-containing multidentate ligand and a carrier. The copper salt and one or more oxygen-containing ligands are loaded on the surface of the carbon support, wherein the copper salt cation is mainly Cu ²⁺ ; the coordinating oxygen atom of the oxygen-containing ligand comes from furan ring, ester group , one or more of carboxyl group and hydroxyl group.

A preparation method of an oxygen-containing multidentate ligand-modified copper-based catalyst for acetylene hydrochlorination is as follows:

1) Dissolve the copper salt and the oxygen-containing multidentate ligand in a specific solvent at a certain temperature in a certain proportion to obtain a mixed solution, at which the ligand can be completely dissolved and a uniform and stable mixed solution can be obtained;

2) Under the same temperature, the active components in the mixed solution are evenly loaded on the activated carbon carrier by methods such as dipping, spraying, precipitation, ion exchange, spray evaporation and drying;

3) The catalyst is obtained by drying for a certain period of time under a certain temperature and pressure environment.

Preferably, in step 1), one or more of the following features are also included:

1) the copper salt is selected from one or more of copper chloride, copper bromide, copper nitrate, copper sulfate; more preferably, the copper salt is copper chloride;

2) The ligands are selected from structures with furan rings (such as 2-acetyl furan, furfuryl alcohol, furfural, hydroxymethyl furfural), ester groups (cycloethyl carbonate, 1,4-butyrolactone, methyl pyruvate); ester, dimethyl maleate, diethyl oxalate, 4-hydroxycoumarin), carboxyl (mandelic acid, 1-hydroxycyclohexylcarboxylic acid, trimethylpyruvic acid, lactic acid, malonic acid, 2-tetrahydrofurancarboxylic acid) ) one or more of the oxygen-containing organics; wherein 2-acetyl furan, furfuryl alcohol, furfural, hydroxymethyl furfural, methyl pyruvate, diethyl oxalate, mandelic acid, 1-hydroxycyclohexylcarboxylic acid, Methyl pyruvic acid, lactic acid, 2-tetrahydrofuran carboxylic acid, etc. can form complex structures with five-membered rings with copper.

3) the molar ratio of copper salt to ligand in the mixed solution is 0.25-2; more preferably, the molar ratio of copper salt to ligand in the mixed solution is 0.5-1;

4) The mixed solution solvent is a common polar solvent; more preferably, the solvent is selected from deionized water, absolute ethanol, acetone, dichloromethane, acetonitrile, chloroform, N,N-dimethylformamide. one or more;

5) The mass fraction of Cu element in the mixed solution accounts for 2.5-16% of the catalyst product mass, such as 2.5-5wt%, 5-8.5wt%, 12-15wt%;

6) The stirring and dissolving temperature of the mixed solution is 15 to 80°C, such as 15°C to 30°C, 40°C to 65°C, and 65°C to 80°C.

Preferably, the following one or more features should be included in step 2):

1) The activated carbon carrier is one or more of coconut shell activated carbon, coal-based activated carbon, wood activated carbon, and pitch-based activated carbon;

2) The water capacity of the activated carbon is 60-130%, and the bulk density is 0.3-0.8 g/mL;

3) The loading temperature is the same as the stirring and dissolving temperature, which is 15-80°C.

Preferably, the following one or more features should be included in step 3):

1) The drying process of the catalyst is as follows: drying for 6-20 hours at 5-20°C higher than the boiling point of the solvent and 0.1MPa.

More preferably, in step 3), drying is performed at 15° C. higher than the boiling point of the solvent for 20 h.

The prepared oxygen-containing multidentate ligand-modified copper-based catalyst is used in acetylene hydrochlorination.

Preferably, the reaction conditions are as follows: the temperature is 90-250° C., the volume space velocity of acetylene is 5-200 h ⁻¹ , and the pressure is 0.01-0.2 Mpa.

The product consisted of gas chromatographic analysis and the reactivity was represented by the acetylene conversion.

Compared with the prior art, the beneficial effects of the present invention are:

1) The catalyst of the present invention adds neutral oxygen-containing multidentate ligands to copper salts to form stable complexes with copper, and forms complexes with copper by introducing oxygen-containing multidentate ligands to stabilize high-valent copper active species;

2) The stability of copper ions can reduce the generation of inactive zero-valent copper in the catalytic process, thereby improving the activity of copper-based catalysts;

3) Oxygen-containing ligands such as 2-tetrahydrofurancarboxylic acid and furfuryl alcohol form a five-membered ring complex after coordination with copper ions, and the electrons of copper ions are adjusted to tend to be more favorable for catalysis. The spatial distribution makes the catalytic activity better. The structure of the five-membered cyclic complex is shown below:

4) The oxygen-containing multidentate ligand-modified copper-based catalyst prepared by the preparation method has high catalytic activity and good stability. When the reaction conditions are 130° C., the space velocity of acetylene is 40h ^-1 , and the volume ratio of hydrogen chloride to acetylene is 1.2:1, The acetylene conversion rate is above 80%, the stability is good, and it has good industrial application potential.

Detailed ways

The technical solutions of the present invention are described below through specific specific examples. The following examples are intended for those skilled in the art to understand the present invention in more detail and are not intended to limit the protection scope of the present invention. The scope of protection of the present invention is set forth in the attached claims.

Example 1

(1) at 50 ° C, 1.7 g of anhydrous copper chloride and 0.61 g of methyl pyruvate were stirred and dissolved in 5.5 g of absolute ethanol to obtain an immersion solution containing copper ions and ligands;

(2) Immerse the immersion liquid on 10g of activated carbon by the equal volume immersion method, and seal and stand at 50°C for 1 hour;

(3) The activated carbon was dried at 95° C. for 20 hours to obtain catalyst A1.

When the reaction conditions of A1 are 130℃, the acetylene space velocity is 40h ^-1 and the volume ratio of hydrogen chloride to acetylene is 1.2:1, the acetylene conversion rate is 84.5%.

Comparative Example 1

(1) at 50 ° C, 1.7 g of anhydrous copper chloride was stirred and dissolved in 5.5 g of absolute ethanol to obtain an immersion solution containing only copper ions;

(2) Immerse the immersion liquid on 10g of activated carbon by the equal volume immersion method, and seal and stand at 50°C for 1 hour;

(3) The activated carbon was dried at 95° C. for 20 hours to obtain catalyst A2.

When the reaction conditions of A2 are 130℃, the acetylene space velocity is 40h ^-1 and the volume ratio of hydrogen chloride to acetylene is 1.2:1, the acetylene conversion rate is 80.6%. However, under the same conditions, only using copper ions as the active component has poor overall performance such as stability and lifespan, which is far from satisfying industrial applications.

Example 2

(1) At 50°C, 1.7g of anhydrous copper chloride and 0.54g of lactic acid were stirred and dissolved in 5.5g of N,N-dimethylformamide to obtain an immersion solution containing copper ions and ligands;

(2) Immerse the immersion liquid on 10g of activated carbon by the equal volume immersion method, and seal and stand at 50°C for 1 hour;

(3) The activated carbon was dried at 170° C. for 20 hours to obtain catalyst A3.

When the reaction conditions of A3 are 130℃, the acetylene space velocity is 40h ^-1 and the volume ratio of hydrogen chloride to acetylene is 1.2:1, the acetylene conversion rate is 87.1%.

Example 3

(1) At 50°C, 1.7g of anhydrous copper chloride and 0.61g of methyl pyruvate were stirred and dissolved in 5.5g of N,N-dimethylformamide to obtain an immersion solution containing copper ions and ligands;

(2) Immerse the immersion liquid on 10g of activated carbon by the equal volume immersion method, and seal and stand at 50°C for 1 hour;

(3) The activated carbon was dried at 170° C. for 20 hours to obtain catalyst A4.

When the reaction conditions of A4 are 130℃, the acetylene space velocity is 40h ^-1 and the volume ratio of hydrogen chloride to acetylene is 1.2:1, the acetylene conversion rate is 86.9%.

Example 4

(1) at 50°C, 1.7g of anhydrous copper chloride and 0.66g of 2-acetylfuran were stirred and dissolved in 5.5g of N,N-dimethylformamide to obtain an immersion solution containing copper ions and ligands;

(2) Immerse the immersion liquid on 10g of activated carbon by the equal volume immersion method, and seal and stand at 50°C for 1 hour;

(3) The activated carbon was dried at 170° C. for 20 hours to obtain catalyst A5.

When the reaction conditions of A5 are 130℃, the acetylene space velocity is 40h ^-1 and the volume ratio of hydrogen chloride to acetylene is 1.2:1, the acetylene conversion rate is 87.3%.

Example 5

(1) at 50°C, 1.7g of anhydrous copper chloride and 0.59g of furfuryl alcohol were stirred and dissolved in 5.5g of N,N-dimethylformamide to obtain an immersion solution containing copper ions and ligands;

(2) Immerse the immersion liquid on 10g of activated carbon by the equal volume immersion method, and seal and stand at 50°C for 1 hour;

(3) The activated carbon was dried at 170° C. for 20 hours to obtain catalyst A6.

When the reaction conditions of A6 are 130℃, the acetylene space velocity is 40h ^-1 and the volume ratio of hydrogen chloride to acetylene is 1.2:1, the acetylene conversion rate is 87.7%.

Example 6

(1) at 50° C., 1.7g of anhydrous copper chloride and 0.70g of 2-tetrahydrofuran formic acid were stirred and dissolved in 5.5g of N,N-dimethylformamide to obtain an impregnation solution containing copper ions and ligands;

(2) Immerse the immersion liquid on 10g of activated carbon by the equal volume immersion method, and seal and stand at 50°C for 1 hour;

(3) The activated carbon was dried at 170° C. for 20 hours to obtain catalyst A7.

When the reaction conditions of A7 are 130℃, the acetylene space velocity is 40h ^-1 and the volume ratio of hydrogen chloride to acetylene is 1.2:1, the acetylene conversion rate is 88.8%.

Example 7

(1) At 50°C, 1.7g of anhydrous copper chloride and 0.53g of cycloethyl carbonate were stirred and dissolved in 5.5g of N,N-dimethylformamide to obtain an immersion solution containing copper ions and ligands;

(2) Immerse the immersion liquid on 10g of activated carbon by the equal volume immersion method, and seal and stand at 50°C for 1 hour;

(3) The activated carbon was dried at 170° C. for 20 hours to obtain catalyst A8.

When the reaction conditions of A8 are 130℃, the acetylene space velocity is 40h ^-1 and the volume ratio of hydrogen chloride to acetylene is 1.2:1, the acetylene conversion rate is 88.1%.

The exhaust gas composition was analyzed using gas chromatography, with samples taken every 0.5 hours. The representative data was sampled at the point of reaction for 4 hours, and the acetylene conversion and vinyl chloride selectivity of copper-based catalysts introduced with different oxygen-containing multidentate ligands were compared. The results are shown in the table:

The better activity of cycloethyl carbonate may be due to the special electronic effect of this structure. The oxygen on the two ɑ positions reduces the electron cloud density on the carbonyl carbon and enhances the nucleophilicity of the carbonyl oxygen. The coordination with copper is more common. The carbonyl group is more stable.

The oxygen-containing ligands in Examples 1-6 can form a five-membered cyclic complex after being coordinated with copper ions. Under the same conditions, the acetylene conversion rate is significantly improved compared to the copper catalyst without oxygen-containing ligands, and copper The strong binding of ions to oxygen-containing multidentate ligands also significantly improves the stability and life of the catalyst, indicating that the addition of oxygen-containing ligands has a significant gain effect.

What is not described in the present invention applies to the prior art.

Claims (10)

1. An oxygen-containing polydentate ligand-modified copper-based catalyst for use in hydrochlorination of acetylene, characterized in that the catalyst comprises a copper salt, an oxygen-containing polydentate ligand and a carrier; the preparation process is that;

(1) dissolving copper salt and oxygen-containing polydentate ligand in a solvent according to a certain proportion to obtain a mixed solution;

(2) uniformly loading the active components in the mixed solution onto an active carbon carrier by adopting a dipping method, a spraying method, a precipitation method, an ion exchange method or a spray evaporation method at the same temperature as the dissolving temperature of the mixed solution obtained in the step (1);

(3) drying at the temperature of 5-20 ℃ higher than the boiling point of the solvent to obtain the catalyst;

the oxygen-containing polydentate ligand is one or more of 2-acetylfuran, furfuryl alcohol, furfural, hydroxymethyl furfural, cyclic ethyl carbonate, 1, 4-butyrolactone, methyl pyruvate, dimethyl maleate, diethyl oxalate, 4-hydroxycoumarin, mandelic acid, 1-hydroxycyclohexyl formic acid, trimethylpyruvic acid, lactic acid, malonic acid and 2-tetrahydrofuran formic acid.

2. The catalyst of claim 1, wherein the copper salt is selected from one or more of copper chloride, copper bromide, copper nitrate, copper sulfate; the mass ratio of the copper element in the catalyst is 2.5-16%.

3. The catalyst of claim 1, wherein copper coordinates to oxygen in the oxygen-containing polydentate ligand to form a five-membered ring complex.

4. The catalyst of claim 1, wherein the support is one or more of coconut shell activated carbon, coal-based activated carbon, wood-based activated carbon, and pitch-based activated carbon.

5. The catalyst of claim 1, wherein the activated carbon has a water capacity of 60 to 130% and a bulk density of 0.3 to 0.8 g/mL.

6. The catalyst according to claim 1, wherein the molar ratio of the copper salt to the ligand in the mixed solution is 0.25 to 2.

7. The catalyst according to claim 1, wherein in step (1), the molar ratio of the copper salt to the ligand is 0.25 to 2; in the step (1), the solvent is a polar solvent.

8. The catalyst of claim 7, wherein the solvent is selected from one or more of deionized water, absolute ethanol, acetone, dichloromethane, acetonitrile, chloroform, N-dimethylformamide; the dissolving temperature of the mixed solution is 15-80 ℃.

9. The catalyst according to claim 1, wherein the drying treatment in the step (3) is performed by: drying for 6-20 h under the condition that the temperature is 5-20 ℃ higher than the boiling point of the solvent and the pressure is 0.1 MPa.

10. The application of the catalyst of claim 1, which is characterized in that the catalyst is used for hydrochlorination of acetylene, the reaction temperature is 90-250 ℃, and the volume space velocity of acetylene is 5-200 h^-1The reaction pressure is 0.01-0.2 MPa.