CN112225640A - Method for preparing enol by selective hydrogenation of alkynol - Google Patents
Method for preparing enol by selective hydrogenation of alkynol Download PDFInfo
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- CN112225640A CN112225640A CN202011211691.1A CN202011211691A CN112225640A CN 112225640 A CN112225640 A CN 112225640A CN 202011211691 A CN202011211691 A CN 202011211691A CN 112225640 A CN112225640 A CN 112225640A
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- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/17—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by hydrogenation of carbon-to-carbon double or triple bonds
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Abstract
The invention discloses a method for preparing enol by selective hydrogenation of alkynol, which achieves the aim of improving the selectivity and has pure product smell and mild reaction conditions by adding an acidic substance to adjust the pH value of a reaction system and adding crown ether to inhibit two main side reactions of terminal alkyne self-coupling and excessive hydrogenation.
Description
Technical Field
The invention relates to the field of selective catalytic hydrogenation, in particular to a method for preparing enol by selective hydrogenation of alkynol.
Background
The enol is an important fine chemical product, and can be used as a VE intermediate, a pyrethroid intermediate, a synthetic vitamin A, a vitamin K1, a carotenoid intermediate, a synthetic rubber monomer and a spice. The synthesis method generally comprises the steps of selectively hydrogenating alkynol to prepare corresponding enol, wherein the reaction general formula is as follows:
wherein R is1、R2Is hydrogen or a hydrocarbyl group.
In addition, it is found that the alkynol can also undergo terminal alkyne self-coupling reaction in the selective hydrogenation process, so that the selectivity is reduced, and the final yield is reduced. According to the document Organic Process Research & Development 2009,13, 991-998 it is reported that 2-methyl-3-buten-2-ol undergoes a corresponding terminal alkyne self-coupling reaction during the selective hydrogenation. The reaction path is as follows:
the terminal alkyne self-coupling reaction is also called Glaser reaction, and Glaser firstly uses CuCl as a catalyst and air as an oxidant to successfully convert phenylacetylene into corresponding conjugated diyne in ammonia water and ethanol. The conjugated diyne derivatives are also a very important substance and can be used as an organic synthesis intermediate, but the content of the conjugated diyne is lower than 3 percent in the process of preparing enol by selective hydrogenation of alkynol, and the purification is difficult, so that the terminal alkyne self-coupling reaction is one of main side reactions and needs to be inhibited.
Disclosure of Invention
The invention provides a method for preparing enol by selective hydrogenation of alkynol.
In order to solve the technical problems, the invention adopts the following technical scheme:
a process for preparing enol by selective hydrogenation of alkynol features that the alkynol is used as raw material and reacts under the action of selective hydrogenation catalyst and crown ether under acidic condition to obtain enol.
In the invention, the selective hydrogenation catalyst is a noble metal-loaded hydrogenation catalyst, the noble metal-loaded hydrogenation catalyst is preferably palladium, and the carrier is preferably calcium carbonate; the selective hydrogenation catalyst is preferably Lindlar catalyst.
Further preferably, the mass content of the supported palladium metal in the Lindlar catalyst is 0.5-50%, preferably 5-25%. Commercially available Lindlar catalysts are typically pre-poisoned with lead acetate, preferably with a lead content of less than 15 wt%, more preferably less than 5 wt%. The using amount of the catalyst for preparing the enol by the selective hydrogenation of the alkynol is 0.1-10 percent of the mass of the alkynol, and the optimal using amount is 0.5-2 percent.
In the invention, an acidic substance is added to maintain the acidic condition of the reaction, and the pH value of the reaction system is 4.0-6.0, preferably 4.5-5.5. The acidic substance can be inorganic acid or organic acid, such as sulfuric acid, nitric acid, acetic acid, benzenesulfonic acid, etc., preferably acetic acid.
According to the method, the pH value range is 4.0-6.0 after the acid substance is added for adjustment, the adjustment system is in an acid state, the occurrence probability of terminal alkyne self-coupling reaction can be reduced, and the generation of terminal alkyne self-coupling products is inhibited; secondly, calcium carbonate is used as a carrier of the alkynol selective hydrogenation catalyst, and the carrier is damaged by too low pH value, so that the pH value range is 4.0-6.0.
In the invention, the crown ether can be 12-crown-4, 15-crown-5, 18-crown-6, 24-crown-8, benzo 12-crown-4, dibenzo 18-crown-6, etc., preferably 15-crown-5 and 18-crown-6. The amount of crown ether added in the method for preparing the enol by the selective hydrogenation of the alkynol is 1-10 percent, preferably 2-5 percent of the mass of the alkynol.
The main functions of the crown ether added in the invention are as follows: crown ethers have special complexation ability for metal cations, variations in the number of atoms and the size of macrocyclic holes, and have significant selectivity for different metal ions. The preparation process of the alkynol selective hydrogenation catalyst is to deposit noble metal on a carrier, and then to reduce and fixedly carry the noble metal on the carrier. A small amount of unreduced metal ions exist in the preparation process, and the raw materials and the solvent used in the reaction can introduce a trace amount of metal ions. The metal ions, especially free copper or palladium ions, can catalyze the terminal alkyne self-coupling side reaction, so that the interference of the free metal ions on the selective hydrogenation of main reaction alkynol needs to be reduced. The crown ether is added into the system to inhibit the generation of a terminal alkyne self-coupling product, and the addition of the crown ether is unexpectedly found to not reduce the selectivity of selective hydrogenation of alkynol, but slightly improve the selectivity.
In some preferred embodiments of the present invention, the preparation method of the present invention comprises the steps of: firstly, mixing crown ether and a catalyst in an inert gas atmosphere, secondly, adding an acidic substance into the system to adjust the pH value to a target value, heating the system, introducing hydrogen to replace the system and reaching a set pressure. And thirdly, adding a reaction substrate alkynol into the reaction system, preserving the temperature, cooling after the reaction is finished, and separating the catalyst from the reaction solution.
Specifically, first, the mixing apparatus is turned on and the crown ether is mixed in the form of a solution or a pure substance with the selective hydrogenation catalyst or a mixture of the selective hydrogenation catalyst and the solvent under an inert gas atmosphere. Secondly, adding an acidic substance into the system to adjust the pH value to a target value, heating the system, introducing hydrogen into the system for replacing the system and reaching a set pressure. Thirdly, adding reaction substrate alkynol into the reaction system at a uniform rate, preserving the temperature and observing the change condition of the gas flow. And finally, cooling after the reaction is finished, and separating the catalyst from the reaction solution by using a filtering, filter pressing or suction filtration mode and the like.
The invention provides a method for preparing enol by selective hydrogenation of alkynol, which takes the alkynol with a structural general formula I as a substrate, and forms the enol with a structural general formula II after selective hydrogenation reaction under the action of a catalyst system for preparing the enol by selective hydrogenation of the alkynol:
wherein R is1、R2Is hydrogen or a hydrocarbyl group, preferably hydrogen or a branched or straight chain C6-C20 alkyl or alkenyl group, R1、R2Same or different, more preferably, R1Or R2One of which is hydrogen and the other is a branched or straight chain C6-C20 alkyl or alkenyl group.
In the method of the present invention, the alkynol is preferably selected from 2-methyl-3-butyn-2-ol, dehydrolinalool, dihydrodehydrolinalool, dehydronerolidol, dihydrodehydronerolidol, tetrahydrodehydronerolidol or dehydroisophytol, etc., and the corresponding molecular structure is as follows:
the structure of the corresponding obtained selective hydrogenation enol product is as follows:
in the method, the selective hydrogenation reaction is carried out at the reaction temperature of 0-90 ℃, preferably 40-70 ℃ and the reaction time of 0.1-24 h, preferably 2-6 h.
In the method of the present invention, in the selective hydrogenation reaction process, the introduction amount of hydrogen is kept at a pressure of 0.05 to 3MPa (gauge pressure), preferably 0.1 to 2.0MPa (gauge pressure) in the system.
In the process of the present invention, the alkynol may be diluted with a solvent selected from one or more of pure water, inert aliphatic alkanes which do not react with the starting material, aromatic hydrocarbons, ethers, alcohols, such as one or more of pure water, n-heptane, toluene, ethanol; preferably, the amount of the diluting solvent is 0 to 3 times, preferably 0.5 to 2.0 times of the mass of the alkynol.
The invention has the positive effects that: the pH value of a reaction system is adjusted by adding an acidic substance, and a crown ether substance is added, so that the effects of inhibiting two main side reactions of terminal alkyne self-coupling and excessive hydrogenation are achieved, and the conversion rate of alkynol and the selectivity of a product enol are improved. The purposes that the conversion rate of alkynol is more than or equal to 98.0 percent and the selectivity of enol is more than or equal to 98.0 percent are achieved.
In the prior art, the Lindlar catalyst can be used only by being modified by adding other poisoning agents such as quinoline, and the excellent catalytic effect can be achieved by adding crown ether and adjusting the pH without adopting the poisoning agents such as quinoline. The product has pure smell and mild reaction conditions, and is suitable for industrial production.
Detailed Description
The process of the present invention will be further illustrated by the following examples, but the present invention is not limited to the examples listed, but also includes any other known variations within the scope of the claims of the present invention.
The analysis method comprises the following steps:
gas chromatograph: agilent7820A, column HP-5(30 m.times.320. mu.m.times.0.25 μm), injection port temperature: 150 ℃; the split ratio is 50: 1; carrier gas flow: 1.5 ml/min; temperature rising procedure: keeping at 40 deg.C for 1min, heating to 90 deg.C at 10 deg.C/min for 0min, heating to 160 deg.C at 5 deg.C/min for 0min, heating to 280 deg.C at 30 deg.C/min for 6 min. Detector temperature: 280 ℃.
Second, the source of the main raw materials
Lindlar catalyst, 5% Pd-5% Pb palladium-calcium carbonate catalyst, Xinnaoko technologies, Inc.;
15-crown-5, 98 wt%, welibart technologies ltd;
18-crown-6, 99 wt.%, Prodwellin technologies, Inc.
Example 1
100.0g of ethanol, 1.0g of 15-crown-5 and 1.0g of 5% Pd-5% Pb palladium calcium carbonate catalyst were charged into an autoclave under an inert gas atmosphere. The stirring was turned on and the pH was adjusted to 5.2 using acetic acid. The autoclave was sealed, and replaced with hydrogen 6 times, and finally the hydrogen pressure was maintained at 2.0MPa (gauge pressure).
And starting heating until the temperature in the kettle is 60 ℃, adding 100.0g of dehydrolinalool into the autoclave by using an advection pump, controlling the adding time of the dehydrolinalool to be about 0.5h, and keeping the temperature in the reaction kettle at 60 ℃ after the addition of the dehydrolinalool is finished to continue the reaction. After the reaction is continued for 3.5h, the flow of the reaction kettle with a hydrogen flow meter is reduced to be below 0.5mL/min, the stirring is stopped, and the hydrogen is discharged. The reaction solution was analyzed by GC and had the following composition: 98.666% of linalool, 0.313% of dihydrolinalool, 0.977% of 15-crown-5, 0.015% of terminal alkyne self-coupling and 0.029% of other components. The conversion rate of alkynol is more than 99.99 percent, and the selectivity of enol is 99.64 percent.
Example 2
100.0g of toluene, 2.0g of 18-crown-6 and 1.0g of 5% Pd-5% Pb palladium-calcium carbonate catalyst were charged into an autoclave under an inert gas atmosphere. The stirring was started and the pH was adjusted to 5.5 using acetic acid. The autoclave was sealed, and replaced with hydrogen 6 times, and finally the hydrogen pressure was maintained at 2.0MPa (gauge pressure).
Heating to 70 deg.C, adding 100.0g of dehydrogenated isophytol into the autoclave by use of advection pump, controlling the adding time of dehydrogenated isophytol at about 0.5h, and maintaining the temperature in the autoclave at 70 deg.C for continuous reaction after adding dehydrogenated isophytol. After the reaction is continued for 2.5h, the flow of the reaction kettle with a hydrogen flow meter is reduced to be below 0.5mL/min, the stirring is stopped, and the hydrogen is discharged. The reaction solution was analyzed by GC and had the following composition: 0.015 percent of dehydroisophytol, 97.730 percent of isophytol, 0.273 percent of dihydroisophytol, 1.948 percent of 18-crown-6, 0.009 percent of terminal alkyne self-coupling and 0.025 percent of other components. The conversion rate of alkynol is 99.985 percent, and the selectivity of enol is 99.69 percent.
Example 3
100.0g of toluene, 5.0g of 18-crown-6 and 10.0g of 5% Pd-5% Pb palladium-calcium carbonate catalyst were charged into an autoclave under an inert gas atmosphere. The stirring was turned on and the pH was adjusted to 4.1 using acetic acid. The autoclave was sealed, and replaced with hydrogen 6 times, and finally the hydrogen pressure was maintained at 0.5MPa (gauge pressure).
Heating to 40 deg.C, adding 100.0g of dehydrogenated isophytol into the autoclave by use of advection pump, controlling the adding time of dehydrogenated isophytol at about 0.5h, and maintaining the temperature in the autoclave at 40 deg.C for continuous reaction after adding dehydrogenated isophytol. After the reaction is continued for 2.0h, the flow of the reaction kettle with a hydrogen flow meter is reduced to be below 0.5mL/min, the stirring is stopped, and the hydrogen is discharged. The reaction solution was analyzed by GC and had the following composition: 0.031% of dehydroisophytol, 95.015% of isophytol, 0.199% of dihydroisophytol, 4.731% of 18-crown-6, 0.003% of terminal alkyne self-coupling and 0.021% of other components. The conversion rate of alkynol is 99.97%, and the selectivity of enol is 99.77%.
Example 4
100.0g of toluene, 9.0g of 18-crown-6 and 5% Pd-5% Pb palladium-calcium carbonate catalyst, 5.0g, were charged into an autoclave under an inert gas atmosphere. The stirring was turned on and the pH was adjusted to 4.5 using acetic acid. The autoclave was sealed, and replaced with hydrogen gas 6 times, to finally maintain a hydrogen pressure of 1.0MPa (gauge pressure).
And starting to heat the kettle until the temperature in the kettle is 50 ℃, adding 100.0g of dehydronerolidol into the autoclave by using an advection pump, controlling the adding time of the dehydronerolidol to be about 0.5h, and keeping the temperature in the reaction kettle at 50 ℃ after the addition of the dehydronerolidol is finished to continue the reaction. After the reaction is continued for 4.0h, the flow of the reaction kettle with a hydrogen flow meter is reduced to be below 0.5mL/min, the stirring is stopped, and the hydrogen is discharged. The reaction solution was analyzed by GC and had the following composition: the content of nerolidol is 91.434 percent, the content of dihydronerolidol is 0.355 percent, the content of 18-crown ether-6 is 8.189 percent, the content of terminal alkyne self-coupling is 0.002 percent, and the content of other components is 0.020 percent. The conversion rate of alkynol is more than 99.99 percent, and the selectivity of enol is 99.59 percent.
Comparative example 1
100.0g of ethanol, 5% Pd-5% Pb palladium-calcium carbonate catalyst, 1.0g, were charged to the autoclave under an inert gas atmosphere. The autoclave was sealed by opening the stirring, and replaced with hydrogen 6 times, and finally the hydrogen pressure was maintained at 2.0MPa (gauge pressure).
And starting heating until the temperature in the kettle is 60 ℃, adding 100.0g of dehydrolinalool into the autoclave by using an advection pump, controlling the adding time of the dehydrolinalool to be about 0.5h, and keeping the temperature in the reaction kettle at 60 ℃ after the addition of the dehydrolinalool is finished to continue the reaction. After the reaction is continued for 3.5h, the flow of the reaction kettle with a hydrogen flow meter is reduced to be below 0.5mL/min, the stirring is stopped, and the hydrogen is discharged. The reaction solution was analyzed by GC and had the following composition: 95.788% of linalool, 2.527% of dihydrolinalool, 0.986% of 18-crown-6, 0.284% of terminal alkyne self-coupling and 0.415% of other components. The conversion rate of alkynol is more than 99.9 percent, and the selectivity of enol is 96.74 percent.
Claims (10)
1. A method for preparing enol by selective hydrogenation of alkynol is characterized in that the alkynol is used as a reaction raw material, and the enol is prepared by reaction under the combined action of a selective hydrogenation catalyst and crown ether under an acidic condition.
2. The process according to claim 1, wherein the selective hydrogenation catalyst is a supported noble metal hydrogenation catalyst, the supported noble metal is preferably palladium, and the carrier is preferably calcium carbonate; the selective hydrogenation catalyst is preferably a Lindlar catalyst;
more preferably, the mass content of the supported palladium metal in the Lindlar catalyst is 0.5-50%, preferably 5-25%, and the use amount of the catalyst for preparing the enol by the selective hydrogenation of the alkynol is 0.1-10%, preferably 0.5-2% of the mass of the alkynol.
3. The method according to claim 1 or 2, characterized in that the acidic condition of the reaction is maintained by adding an acidic substance, and the pH value of the reaction system is in the range of 4.0 to 6.0, preferably 4.5 to 5.5;
preferably, the acidic substance is an inorganic acid or an organic acid, preferably sulfuric acid, nitric acid, acetic acid, benzenesulfonic acid, and more preferably acetic acid.
4. The method according to claim 1 or 2, wherein the crown ether comprises one or more of 12-crown-4, 15-crown-5, 18-crown-6, 24-crown-8, benzo 12-crown-4, dibenzo 18-crown-6, preferably 15-crown-5, 18-crown-6;
the addition amount of the crown ether is 1 to 10 percent of the mass of the alkynol, and preferably 2 to 5 percent.
5. The method according to any one of claims 1 to 4, comprising: firstly, mixing crown ether and a catalyst in an inert gas atmosphere, secondly, adding an acidic substance into the system to adjust the pH value to a target value, heating the system, introducing a hydrogen replacement system to set pressure, adding a reaction substrate alkynol into the reaction system, preserving heat, cooling after the reaction is finished, and separating the catalyst from a reaction solution.
6. A process according to any one of claims 1 to 5, characterized in that the alkynol has the general structural formula I,
the structural formula of the enol is as follows:
wherein R is1、R2Is hydrogen or a hydrocarbyl group, preferably hydrogen or a branched or straight chain C6-C20 alkyl or alkenyl group, R1、R2Same or different, more preferably, R1Or R2One of which is hydrogen and the other is a branched or straight chain C6-C20 alkyl or alkenyl group.
7. The method according to claims 1 to 6, wherein the alkynol is selected from 2-methyl-3-butyn-2-ol, dehydrolinalool, dihydrodehydrolinalool, dehydronerolidol, dihydrodehydronerolidol, tetrahydrodehydronerolidol or dehydroisophytol.
8. The method according to claims 1 to 7, wherein the selective hydrogenation reaction is carried out at a temperature of 0 to 90 ℃, preferably 40 to 70 ℃, for a time of 0.1 to 24 hours, preferably 2 to 6 hours.
9. The method according to claims 1 to 8, wherein the introduction amount of hydrogen in the selective hydrogenation reaction is kept at a pressure of 0.05 to 3MPa, preferably 0.1 to 2.0MPa, in the system.
10. The method according to any one of claims 1 to 9, wherein in the reaction, the alkynol is diluted by a solvent, and the solvent is selected from one or more of pure water, inert aliphatic alkane which does not react with the raw material, aromatic hydrocarbon, ether and alcohol, preferably one or more of pure water, n-heptane, toluene and ethanol;
preferably, the amount of the diluting solvent is 0 to 3 times, preferably 0.5 to 2.0 times of the mass of the alkynol.
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| CN113788737A (en) * | 2021-08-25 | 2021-12-14 | 万华化学集团股份有限公司 | Triple bond partial hydrogenation method and catalyst thereof |
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| CN113788737A (en) * | 2021-08-25 | 2021-12-14 | 万华化学集团股份有限公司 | Triple bond partial hydrogenation method and catalyst thereof |
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