WO2020258413A1 - Application of gold-based catalyst to catalyzing oxidation of aldehyde to generate ester - Google Patents

Abstract

An application of a gold-based catalyst to catalyzing oxidation of an aldehydes to generate an ester. The gold-based catalyst comprises an active center and a carrier. The active center comprises gold and a rare earth metal, the loading of the gold being 0.02-2 wt%, the loading of the rare earth metal being 0.1-3 wt%. The carrier is one of Al ₂O ₃, TiO ₂, SiO ₂, Fe ₃O ₄, ZrO ₂, SiO ₂-Al ₂O ₃, CaCO ₃, a carbon material, and a molecular sieve material. The reaction of the application is: using a C1-C2 small molecular alcohol and an unsaturated aromatic aldehyde or furan aldehyde as raw materials, and introducing molecular oxygen to generate an ester under the action of the gold-based catalyst. No alkali, bromine, or sulfuric acid is present in the reaction system, and the high activity of the gold-based catalyst greatly reduces the alcohol-to-aldehyde ratio, and the process features conversion rate and selectivity improvement and cost reduction.

Description

Application of a gold-based catalyst to catalyze the oxidation of aldehydes to esters Technical field

The invention relates to the technical field of catalytic oxidation, in particular to a method for oxidative esterification of aldehydes.

Background technique

Esters are an important chemical and organic synthesis intermediate. The traditional synthesis method is to first oxidize aldehydes or alcohols to prepare acids or acid derivatives, and then esterify them with alcohols. The benzoic acid esters in aromatic esters and their salts with acids have strong antitrypsin activity, strong antithrombin activity and strong anticoagulant activity. At the same time, they have low toxicity and can be used to treat pancreas and disseminated intravascular Blood coagulation (DIC) agent; can also be used as a plasticizer. In furan aldehyde, 5-hydroxymethyl furfural (5-HMF) is an important chemical raw material. As a furan structure compound, 5-hydroxymethyl furfural can be hydrogenated, esterified, halogenated, polymerized, redox, etc. The reaction is transformed into many high value-added products such as fuels, polymer materials, medicines, and pesticides. Its catalytic oxidation product, dimethyl furan-2,5-dicarboxylate, can be used to prepare bio-based polyesters, which are compatible with ethylene terephthalate, butylene terephthalate and polyterephthalate. Polyester materials such as propylene glycol esters also have excellent properties and have the characteristics of renewable resources and degradability. They can be used as raw materials for the production of degradable plastics. They have a wide range of industrial applications and huge market potential.

The industrial production of benzoic acid ester is made by esterification reaction of benzoic acid with alcohol in the presence of sulfuric acid. It is prepared by mixing benzoic acid with alcohol, adding concentrated sulfuric acid, heating and refluxing. During the reaction process, there are problems such as acid liquid, harsh requirements for reaction equipment and subsequent distillation equipment, and unfriendly environment.

5-HMF is composed of a furan ring, an aldehyde group and a hydroxyl group. The oxidation process of 5-HMF is a process of co-oxidation of aldehyde group and hydroxyl group. Therefore, besides (FDMC), there are many by-products, including 5 -Methyl hydroxymethylfuroate (HMMF), 2,5-furandiformaldehyde (DFF), 5-aldehyde methyl furoate (FFMC), etc. Existing studies have shown that the existing 5-HMF oxidative esterification technical system requires the addition of alkali or bromine as an initiator due to the low activity of the catalyst, and a higher reaction pressure and reaction temperature are required to achieve efficient conversion of aldehydes. This inevitably brings about product separation and equipment corrosion problems, and the harsh reaction conditions, low yield and other shortcomings, greatly restrict the application of dimethyl furan-2,5-dicarboxylate in the direction of biodegradable materials.

Summary of the invention

In view of the defects in the prior art, the present invention provides a gold-based supported catalyst. In the preparation of aromatic esters and furan esters, it can ensure the selectivity of aromatic esters and furan esters while greatly improving the conversion of aromatic aldehydes and furan aldehydes. rate.

The present invention is realized through the following technical solutions:

The invention provides an application of a gold-based catalyst in the oxidation of aldehydes to esters. The gold-based catalyst includes an active center and a carrier; the active center includes gold and rare earth metals.

Based on the above technical solution, preferably, the gold-based catalyst is made by a gold sol solid support method, the catalyst includes an active center and a carrier; the active center includes gold and rare earth metals.

As a preferred solution, the catalyst active center includes gold and a rare earth metal; the loading amount of gold in the catalyst is 0.02-2 wt%, and the loading amount of rare earth metal is 0.1-3 wt%.

Further, the rare earth metal is one of scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), and neodymium (Nd).

Further, the carrier is one of Al ₂ O ₃ , TiO ₂ , SiO ₂ , Fe ₃ O ₄ , ZrO ₂ , SiO ₂ -Al ₂ O ₃ , CaCO ₃ , carbon material, and molecular sieve material.

Further, the gold-based catalyst is made by the following method:

Under stirring conditions, fully mix the gold precursor with the reducing agent and deionized water to obtain a stable, uniform and single gold sol with a relatively high dispersion state, then add the polymer protective agent and the carrier, and continue to stir for 1-24 hours. Slowly raise the temperature to 50-80℃, after the stirring, reduce to room temperature, stand still and filter, wash with deionized water until no chlorine ions can be detected, after drying, calcinate in the air at 500-700℃ for 5-20h to obtain gold base catalyst. Further, after the gold sol is obtained, the rare earth metal precursor is added in the presence of the polymer protective agent, and then the carrier is added to continue to prepare the gold and rare earth metal-supported gold-based catalyst.

Based on the above technical solutions, preferably, the precursor of Au is gold cyanide (Au(CN) ₃ ), potassium aurous cyanide, gold chloride (AuCl), gold chloride (AuCl ₃ ), gold chloride One or two or more of acid, chloroauric acid, sodium gold sulfite or Lei Jin; the precursor of the rare earth metal is the nitrate of the rare earth metal.

Based on the above technical solutions, preferably, the polymer protective agent is polyvinyl alcohol, polyvinylpyrrolidone, tetramethylolphosphorus chloride, polydimethyldipropylene ammonium chloride, sodium citrate, and mercaptans.

Based on the above technical solution, preferably, the reducing agent is sodium citrate, tetrahydroxymethyl phosphorous chloride, oxalic acid and sodium borohydride.

Based on the above technical solution, preferably, in the method, the amount of gold precursor, reducing agent, polymer protective agent and carrier added is: the mass ratio of gold element: reducing agent: polymer protective agent: carrier: water is 1 : (0.1-25): (0.1-25): (25-1000): (100-2000).

The application of the gold-based catalyst of the present invention in the oxidative esterification of aldehydes to prepare esters does not limit the reaction system. Preferably, air and/or oxygen are used as oxidants to react with methanol or ethanol.

Based on the above technical solution, preferably, the reaction is carried out without adding alkali, bromine or sulfuric acid.

The present invention is a method for preparing esters by oxidizing aldehydes, including the following steps: fully mixing raw aldehydes and alcohols in a reactor, adding gold-based catalysts to the reaction mixture; sealing the reactor, turning on the stirring, and passing pure Oxygen or oxygen with a concentration of (15%-60%) whose supplementary gas is nitrogen inert gas, react for 2h; the reaction temperature is controlled at 100～130℃, the reaction pressure is controlled at 2.5～5MPa; the reaction temperature is preferably 110℃; the reaction pressure is preferably 3MPa.

As a preferred solution, in the method for oxidizing aldehydes to synthesize esters of the present invention, in the reaction system, when the raw material aldehyde is aromatic aldehyde, the molar ratio of alcohol to aromatic aldehyde is 1; when the raw material aldehyde is furan aldehyde, The molar ratio of alcohol to furan aldehyde is 5-60:1.

As a preferred solution, in the method for oxidizing aldehyde to synthesize ester of the present invention, the reaction pressure is 2.5-4 MPa.

As a preferred solution, in the method for oxidizing aldehydes to synthesize esters of the present invention, the reaction temperature is 100-130°C, and the reaction time is 1-3h.

In the method for oxidizing aldehydes to synthesize esters of the present invention, the molar ratio of alcohol to aromatic aldehyde in the reaction system is 1:1, and the molar ratio of alcohol to furan aldehyde is more preferably 5-15:1.

The products in the reaction system are analyzed by gas chromatography, and the conversion rate of aldehyde and the selectivity of the target product ester are calculated. The obtained reaction indicators are: the conversion rate of aldehyde>95%, and the selectivity of ester>99%.

Beneficial effect

(1) Under the action of the gold-based catalyst, the present invention can rapidly oxidize and esterify aromatic aldehydes and furfural without adding any initiator;

(2) The present invention has mild reaction conditions, short reaction time and simple reaction route;

(3) In the synthesis method of the present invention, the highly active Au-based catalyst realizes the process conditions of low aldol ratio, greatly reduces the energy consumption of the subsequent product separation process, and greatly improves the economics of the process. Moreover, the molar ratio of alcohol to aromatic aldehyde is 1, and the molar ratio of alcohol to furan aldehyde is 5-60:1, more preferably 5-15:1, which reduces the aldol ratio while avoiding the need to increase conversion in the existing process. Initiators such as bromine, alkali or sulfuric acid are added based on the efficiency and selectivity.

(4) The method of the present invention has high selectivity to esters, and the use of gold-based rare earth metal supported catalysts can ensure that the conversion rate of aldehydes is greater than 95%, and the selectivity of esters is greater than 99%.

Detailed ways

The embodiments of the technical solution of the present invention will be described in detail below. The following embodiments are only used to illustrate the technical solutions of the present invention more clearly, and therefore are only used as examples, and cannot be used to limit the protection scope of the present invention.

It should be noted that, unless otherwise specified, the technical or scientific terms used in this application shall have the usual meaning understood by those skilled in the art to which the present invention belongs.

Example 1

Under room temperature conditions, during the stirring process, dissolve 1.3g of chloroauric acid and 1g of sodium citrate in 600mL of deionized water. After fully dissolving, add 1g of polyvinylpyrrolidone (PVP, molecular weight 8000-10000) and 9.4g of lanthanum nitrate to dissolve completely Then add 0.3kg of TiO ₂ powder, continue to stir and slowly raise the temperature to 75°C, continue stirring at this temperature for 14 hours and then drop to room temperature, after standing still, pour out the upper layer of liquid, and wash the lower layer of sediment with deionized water until no chlorine is detected Ions, dried at 100°C for 24 hours and then calcined in air at 300°C for 24 hours to obtain the catalyst La-Au/TiO ₂ . Among them, the mass percentages of La and Au in the catalyst are 1% and 0.1% respectively.

Example 2

The catalyst preparation conditions were the same as in Example 1. The lanthanum nitrate was replaced with cerium nitrate to obtain the catalyst Ce-Au/TiO ₂ , in which the mass percentages of Ce and Au in the catalyst were 1% and 0.1% respectively.

Example 3

The catalyst preparation conditions were the same as in Example 1. The lanthanum nitrate was replaced with cerium nitrate to obtain the catalyst Sc-Au/TiO ₂ , wherein the mass percentages of Sc and Au in the catalyst were 1% and 0.1%, respectively.

Example 4

The catalyst preparation conditions were the same as in Example 1. The lanthanum nitrate was replaced with yttrium nitrate to obtain the catalyst Y-Au/TiO ₂ , wherein the mass percentages of Y and Au in the catalyst were 1% and 0.1% respectively.

Example 5

The catalyst preparation conditions were the same as in Example 1. The lanthanum nitrate was replaced with praseodymium nitrate to obtain the catalyst Pr-Au/TiO ₂ , wherein the mass percentages of Pr and Au in the catalyst were 1% and 0.1%, respectively.

Example 6

The catalyst preparation conditions were the same as in Example 1. The lanthanum nitrate was replaced with neodymium nitrate to obtain the catalyst Nd-Au/TiO ₂ , wherein the mass percentages of Nd and Au in the catalyst were 1% and 0.1% respectively.

Example 7

The catalyst preparation conditions were the same as in Example 1. The TiO ₂ was replaced with SiO _{2 to} obtain the catalyst La-Au/SiO ₂ , in which the mass percentages of Ce and Au in the catalyst were 1% and 0.1% respectively.

Example 8

The catalyst preparation conditions were the same as in Example 1. The TiO _{2 was} replaced with Fe ₃ O _{4 to} obtain the catalyst La-Au/Fe ₃ O ₄ , in which the mass percentages of Ce and Au in the catalyst were 1% and 0.1%, respectively.

Example 9

The catalyst preparation conditions were the same as in Example 1. The catalyst La-Au/ZrO ₂ was obtained by replacing TiO ₂ with ZrO ₂ , in which the mass percentages of Ce and Au in the catalyst were 1% and 0.1% respectively.

Example 10

The catalyst preparation conditions were the same as in Example 1. The catalyst La-Au/CaCO ₃ was obtained by replacing TiO ₂ with CaCO ₃ , in which the mass percentages of Ce and Au in the catalyst were 1% and 0.1%, respectively.

Example 11

Weigh 500g silica sol (30wt%), add 90g aluminum nitrate during the stirring process, add 2.5ml concentrated nitric acid to adjust the PH value, continue stirring at 50℃ for 24h, and spray drying after cooling to room temperature. The spray condition is: 10ml/min Material quantity, inlet temperature 200-220℃, outlet temperature 80-100℃, to obtain carrier SiO ₂ -Al ₂ O ₃ powder with a particle size of about 70 μm, and then calcinate the powder at 700℃ in an air atmosphere for 6 hours, and then cool to room temperature To spare.

The catalyst preparation conditions were the same as in Example 1. The TiO _{2 was} replaced with the carrier SiO ₂ -Al ₂ O ₃ prepared above to obtain the catalyst La-Au/SiO ₂ -Al ₂ O ₃ , in which the mass percentages of La and Au in the catalyst The content is 1% and 0.1% respectively.

Example 12

The preparation conditions of the catalyst were the same as in Example 11, where lanthanum nitrate was not added to obtain a catalyst Au/SiO ₂ -Al ₂ O ₃ , wherein the mass percentage of Au in the catalyst was 0.1% respectively.

Example 13

The catalysts described in Examples 1-12 were respectively applied to the reaction of oxidative esterification of 5-hydroxymethylfurfural to prepare dimethyl furan-2,5-dicarboxylate, and the reaction conditions were:

Mix 5ml 5-hydroxymethyl furfural and methanol in the reactor thoroughly, add 2g of gold-based catalyst to the reaction mixture; seal the reactor, turn on the stirring, and pass pure oxygen and inert gas at the bottom of the reactor for 2h reaction; The molar ratio of methanol to 5-hydroxymethylfurfural in the mixture is 15:1, the reaction temperature is controlled at 110℃, and the reaction pressure is controlled at 3MPa. The products in the reaction system are analyzed by gas chromatography to calculate the conversion of 5-hydroxymethylfurfural Rate C (HMF) and dimethyl furan-2,5-dicarboxylate selectivity S (FDMC), the results are as follows: It can be seen that the addition of lanthanide metals improves the conversion rate of HMF and the selectivity of FDMC.

Example 14

The reaction process was the same as in Example 13. The methanol was replaced with the same mole number of ethanol, and the aldol ratio was maintained at 15:1 to obtain diethyl furan-2,5-dicarboxylate (FDEC). The results are as follows. It can be seen that the prepared gold catalyst can also catalyze the esterification reaction between HMF and ethanol, and has excellent activity.

Example 15

The reaction process was the same as in Example 13. The 5-hydroxymethyl furfural was replaced with 15 times the number of moles of benzaldehyde, and the aldol ratio was maintained at 1:1. The resulting product was methyl benzoate. The highest conversion rate of benzaldehyde after the reaction The highest selectivity of methyl benzoate is 100%.

Example 16

The reaction process was the same as that in Example 15. The methanol was changed to ethanol, and the aldol ratio was maintained at 1:1. After the reaction, the highest conversion rate of benzaldehyde was 100%, and the highest selectivity of ethyl benzoate was 100%.

Example 17

The reaction process was the same as that in Example 13. The 5-hydroxymethyl furfural was replaced with 15 times the moles of phenylacetaldehyde and the aldol ratio was kept at 1:1. After the reaction, the highest conversion rate of phenylacetaldehyde was 100%. The highest ester selectivity is 100%.

Example 18

The reaction process was the same as that in Example 17. The methanol was changed to ethanol, and the aldol ratio was maintained at 1:1. After the reaction, the highest conversion rate of phenylacetaldehyde was 100%, and the highest selectivity of phenylacetaldehyde was 100%.

Example 18

The reaction process was the same as in Example 13. The 5-hydroxymethylfurfural was replaced with 15 times the mole number of phenylpropanal, and the aldol ratio was maintained at 1:1. After the reaction, the highest conversion rate of phenylpropanal was 100%, and phenylpropionic acid The highest selectivity of methyl ester is 100%.

Example 19

The reaction process was the same as in Example 18. The methanol was replaced with ethanol, and the aldol ratio was maintained at 1:1. After the reaction, the highest conversion rate of phenylpropionaldehyde was 100%, and the highest selectivity of methyl phenylpropionate was 100%.

Example 20

The reaction process is the same as in Example 13, replacing 5-hydroxymethyl furfural with 3 times the number of moles of furfural, keeping the aldol ratio at 5:1. The highest conversion rate of furfural after the reaction is 99%, and the highest selectivity of methyl furoate Is 99%.

Example 21

The reaction process is the same as in Example 20, changing methanol to ethanol, keeping the aldol ratio at 5:1. After the reaction, the maximum conversion rate of furfural is 100%, and the maximum selectivity of ethyl furoate is 99%.

Example 22

The reaction process was the same as that in Example 13. The 5-hydroxymethylfurfural was replaced with 3-fold moles of 5-methylfurfural, and the aldol ratio was maintained at 5:1. After the reaction, the highest conversion rate of 5-methylfurfural was 98%. The highest selectivity for methyl 5-methylfuroate is 99%.

Example 23

The reaction process was the same as that in Example 22. The methanol was changed to ethanol and the aldol ratio was maintained at 5:1. After the reaction, the highest conversion rate of 5-methylfurfural was 100%, and the highest selectivity of 5-methylfurfural ethyl ester was 99%.

Example 24

The reaction process was the same as in Example 13. The 5-hydroxymethylfurfural was replaced by 3-fold moles of 5-ethyl-2-furaldehyde, and the aldol ratio was maintained at 5:1. After the reaction, the amount of 5-ethyl-2-furaldehyde The highest conversion rate is 95%, and the highest selectivity of 5-ethyl-2-furoate is 99%.

Example 25

The reaction process was the same as that in Example 24. The methanol was changed to ethanol and the aldol ratio was maintained at 5:1. After the reaction, the highest conversion rate of 5-ethyl-2-furaldehyde was 96%. The highest ester selectivity is 99%.

Claims (15)

1. An application of a gold-based catalyst to catalyze the oxidation of aldehydes to form esters, characterized in that the gold-based catalyst includes an active center and a carrier; the active center includes gold; the loading amount of gold is 0.02-2wt%; the reaction of the application It is: taking aldehydes and C1-C2 small molecular alcohols as raw materials, and under the action of the gold-based catalyst, molecular oxygen is introduced to generate esters.
2. The application according to claim 1, wherein the active center further comprises rare earth metals; the loading amount of rare earth metals is 0.1-3wt%.
3. The application according to claim 1, wherein the C1-C2 small molecule alcohols are methanol or ethanol.
4. The application according to claim 1, wherein the aldehyde is R-CHO, wherein R is phenyl or furyl.
5. The application according to claim 1, wherein the gold-based catalyst is prepared by a gold sol solid support method.
6. The application according to claim 1, characterized in that: the carrier is Al ₂ O ₃ , TiO ₂ , SiO ₂ , Fe ₃ O ₄ , ZrO ₂ , SiO ₂ -Al ₂ O ₃ , CaCO ₃ , carbon material, One of the molecular sieve materials.
7. The application according to claim 1, characterized in that the reaction pressure of the reaction is 2.5-4MPa, the reaction temperature is 100-130°C, and the reaction time is 1-3h.
8. The application according to claim 4, wherein when the reacted aldehyde is an aromatic aldehyde, the molar ratio of aldol is 1:1; when the aldehyde is furan aldehyde, the molar ratio of aldol is 5-15:1 .
9. The application according to claim 2, wherein the rare earth metal is one of scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), and neodymium (Nd) Kind.
10. The application according to claim 5, wherein the preparation method of the gold-based catalyst comprises the following steps:

    The gold precursor, reducing agent and deionized water are fully mixed and stirred to obtain a gold sol, then the polymer protective agent and carrier are added, the temperature is raised to 50-80°C, stirred for 1-24h, then the temperature is lowered, filtered and washed to No chlorine ions can be detected, and the gold-based catalyst is obtained by roasting in the air after drying.
11. The application according to claim 10, wherein the preparation method of the gold-based catalyst further comprises the following steps:

    After the gold sol is obtained, the rare earth metal precursor is added in the presence of the polymer protective agent, and then the carrier is added to continue preparing the gold-based catalyst.
12. The application according to claim 10 or 11, characterized in that: the gold precursor is gold cyanide (Au(CN) ₃ ), potassium aurous cyanide, gold chloride (AuCl), gold chloride (AuCl ₃ ), one or more of chloroauric acid, chloroauric acid, sodium gold sulfite, or Lei Jin; the rare earth metal precursor is the nitrate of the rare earth metal.
13. The application according to claim 10, wherein the reducing agent is sodium citrate, tetrakis(hydroxymethyl)phosphorus chloride, oxalic acid and sodium borohydride.
14. The application according to claim 10, wherein the polymer protective agent is polyvinyl alcohol, polyvinylpyrrolidone, tetramethylolphosphorus chloride, polydimethyldipropylene ammonium chloride, sodium citrate, Mercaptans.
15. The application according to claim 10, characterized in that: in the method, the amount of gold precursor, reducing agent, polymer protective agent and carrier added is: gold element: reducing agent: polymer protective agent: carrier: water The mass ratio is 1:0.1～25:0.1～25:25～1000:100～2000.