Method for preparing neopentyl polyol higher fatty acid ester by two-step method

Abstract

The invention discloses a method for preparing neopentyl polyol higher fatty acid ester by a two-step method, which comprises the following steps: under the action of a palladium-based catalyst, performing alkoxycarbonylation reaction on alpha-olefin and carbon monoxide in low-carbon alcohol to generate fatty acid ester; and carrying out transesterification on the generated fatty acid ester and neopentyl polyol under the action of an acid catalyst to generate the corresponding neopentyl polyol fatty acid ester. The method disclosed by the invention has the advantages of high atom economy, high product yield, convenience in catalyst separation, easiness in product purification, green and environment-friendly technological process and the like.

Description

Technical Field

[0001] The present invention belongs to the field of fine chemical preparation, and particularly relates to a method for preparing neopentyl polyol higher fatty acid esters through two-step reactions, that is, first obtaining higher fatty acid esters through the alkoxycarbonylation reaction of α-olefins, and then obtaining neopentyl polyol higher fatty acid esters through the transesterification reaction of the obtained higher fatty acid esters with neopentyl polyol. Background Art

[0002] Neopentyl polyol higher fatty acid esters have excellent high and low temperature properties, viscosity-temperature properties, antioxidant properties, low volatility and good lubricating properties due to their unique molecular structures, and have the biodegradability, low toxicity and raw material renewability of ester oils, meeting the current requirements for new lubricating materials and becoming the best choice for high-end synthetic ester lubricants.

[0003] Currently, the reported preparation methods of neopentyl polyol higher fatty acid esters usually use the corresponding fatty acids and pentyl polyols as raw materials and acids or bases as catalysts to synthesize through esterification reactions. For example, Patent CN 111410734A reports that hydroxy acids and fatty acids first generate oligomers through esterification reactions and then react with dibasic acids to generate polyester, and this polyester can be used as an environmentally friendly high-viscosity lubricating oil. Patent CN 112552977A reports that using monocarboxylic acids and polyols as raw materials, by adding a large excess of polyols in two steps, the monocarboxylic acids are completely esterified, and the synthesized esters can be used as lubricating oil base stocks. Patent CN 113088363A reports that neopentyl polyol first reacts with dibasic fatty acids under the action of solid acids through esterification reactions to obtain oligomers, and then reacts with coconut oil fatty acids under the action of silica gel-supported catalysts to obtain composite esters, and these composite esters have the characteristics of very low solubility in lower fatty alcohols and a wide viscosity range. Patent CN 109053441A reports that oleic acid, pentaerythritol, and succinic acid monoester are prepared into pentaerythritol mixed esters through two-step esterification in a molar ratio of 3:1:1.1 - 1.2, and the succinic acid monoester still needs to be in excess. It can be seen that when synthesizing polyol fatty acid esters by the esterification reaction of polyols and fatty acids, due to the chemical equilibrium existing in the esterification reaction, generally one of the raw materials needs to be in excess, or the product water needs to be removed from the reaction system to make the esterification reaction close to complete. However, both the raw material polyols and fatty acids have relatively high boiling points and are difficult to completely remove from the product by vacuum distillation, which will lead to a decrease in product purity or a relatively high acidity value. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing neopentyl polyol higher fatty acid esters. This method has the advantages of high atom economy, high product yield, convenient separation and recovery of catalysts, easy purification of products, and a green and environmentally friendly process.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A method for preparing neopentyl polyol higher fatty acid ester, which first obtains a higher fatty acid ester through the alkoxycarbonylation reaction of an α-olefin, and then obtains the neopentyl polyol higher fatty acid ester by transesterification with neopentyl polyol. The steps are as follows: (1) In a palladium-based catalytic system, dissolve the olefin in a lower alcohol and introduce carbon monoxide for alkoxycarbonylation reaction to generate a fatty acid ester; (2) In the presence of an acid catalyst, carry out a transesterification reaction between the fatty acid ester generated in step (1) and neopentyl polyol to generate the required neopentyl polyol fatty acid ester.

[0006] Further, the palladium-based catalytic system in step (1) is composed of a palladium-based catalyst, a phosphine ligand, and an acid promoter in a molar ratio of 1:(10 - 60):(10 - 60).

[0007] Furthermore, the content of Pd in the palladium-based catalyst is 5 wt%.

[0008] Furthermore, the palladium-based catalyst can be either a homogeneous catalyst, such as palladium acetate, palladium chloride, etc.; or a supported catalyst, such as Pd / C, Pd / γ-Al2O3, etc. Preferably, it is a supported catalyst, which is more convenient for separation and recovery from the product.

[0009] Furthermore, the phosphine ligand can be selected from any one of triphenylphosphine, 1,2-bis(di-tert-butylphosphinomethyl)benzene, 4,5-bis(diphenylphosphino)-9,9-dimethyloxanthrene, diphenyl-2-pyridylphosphine, etc. Preferably, it is triphenylphosphine, which has good activity and economy.

[0010] Furthermore, the acid promoter can be selected from benzenesulfonic acid, p-toluenesulfonic acid, etc. Preferably, it is p-toluenesulfonic acid.

[0011] Further, the olefin in step (1) is a long-chain α-olefin of C5-C 18 ...

[0012] Further, the lower alcohol in step (1) is an alcohol of C1-C3, which can be methanol, ethanol, n-propanol, etc. Preferably, it is methanol. In this reaction, the lower alcohol is both a reactant and a solvent, and its addition amount is usually in excess.

[0013] Further, the dosage of the palladium-based catalytic system in step (1) is calculated according to the molar ratio of palladium contained therein to the olefin of 1:(100~2000).

[0014] Further, the temperature of the alkoxycarbonylation reaction in step (1) is 60-120 °C, the pressure > 1.0 MPa, and the time is 2-10 hours. Preferably, the reaction temperature is 100 °C and the pressure is 2.0-5.0 Mpa.

[0015] Further, the acid catalyst in step (2) can be a liquid acid catalyst such as concentrated sulfuric acid, p-toluenesulfonic acid, etc., or a solid acid catalyst such as cation exchange resin, solid superacid, inorganic oxide, etc. Preferably, it is a solid acid catalyst, which is convenient for separating from the product and does not corrode the equipment. More preferably, it is a strongly acidic ion exchange resin.

[0016] Further, the neopentyl polyol in step (2) is one or more of neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol, etc. Preferably, it is neopentyl glycol.

[0017] Further, the dosage of the neopentyl polyol in step (2) is converted according to the molar ratio of the fatty acid ester used to the hydroxyl group in the neopentyl polyol being (1.1-1.2):1. The fatty acid ester is in excess during the reaction so that the neopentyl polyol can react almost completely.

[0018] Further, the dosage of the acid catalyst in step (2) is 4-12% of the total mass of the fatty acid ester and the neopentyl polyol.

[0019] Further, the temperature of the transesterification reaction in step (2) is 80-160 °C and the time is 12-24 °C.

[0020] The principle and advantages of the present invention are as follows: The present invention synthesizes neopentyl polyol higher fatty acid esters through olefin alkoxycarbonylation reaction and transesterification reaction. Among them, the first-step alkoxycarbonylation reaction of α-olefin has high atom economy, high conversion rate and selectivity, and the yield of higher fatty acid can reach more than 90% (calculated based on the raw material olefin). At the same time, by using a supported Pd catalyst, the problem that the catalyst is difficult to recover in the homogeneous reaction system can be effectively solved, greatly reducing the catalyst cost. The second-step transesterification reaction has mild conditions, high product yield, and it is easier to remove the excess reaction raw materials, facilitating the purification of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 13C-NMR of the neopentyl glycol dinonanoate prepared in the example 13 13C-NMR.

[0022] Figure 2 1H-NMR of the neopentyl glycol dinonanoate prepared in the example 1 1H-NMR. DETAILED DESCRIPTION OF THE INVENTION

[0023] A method for preparing neopentyl polyol higher fatty acid esters, the specific steps are as follows: (1) Dissolve the olefin in a lower alcohol, add a palladium-based catalyst, a phosphine ligand and an acid assistant, then introduce carbon monoxide until the gas pressure > 1 MPa, and then react at 60 - 120 °C for 2 - 10 hours to produce a fatty acid ester; (2) Mix the fatty acid ester and the hydroxyl groups in neopentyl polyol in a molar ratio of (1.1 - 1.2):1, add an acid catalyst accounting for 4 - 12% of their total mass, and react at 80 - 160 °C for 12 - 24 °C to produce the required neopentyl polyol fatty acid ester.

[0024] Among them, the olefin described in step (1) is a long-chain α-olefin with C5 - C 18 The lower alcohol can be methanol, ethanol, n-propanol, etc. The molar ratio of palladium to olefin in the palladium-based catalyst is 1:(100 - 2000). The molar ratio of the used palladium-based catalyst, phosphine ligand and acid assistant is 1:(10 - 60):(10 - 60). The content of Pd in the palladium-based catalyst is 5 wt%. The phosphine ligand can be selected from any one of triphenylphosphine, 1,2-bis(di-tert-butylphosphinomethyl)benzene, 4,5-bis(diphenylphosphino)-9,9-dimethyloxanthene, diphenyl-2-pyridylphosphine, etc. The acid assistant can be selected from benzenesulfonic acid, p-toluenesulfonic acid, etc.

[0025] The neopentyl polyol described in step (2) is one or several of neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol, etc.

[0026] To make the content of the present invention easier to understand, the technical solutions of the present invention are further described below in conjunction with specific embodiments, but the present invention is not limited thereto. Examples

[0027] Taking the preparation of neopentyl glycol dinonanoate as an example, the main process route is to generate methyl nonanoate through the alkoxycarbonylation reaction of 1-octene and methanol, and then generate neopentyl glycol dinonanoate through the transesterification reaction of methyl nonanoate and neopentyl glycol.

[0028] 1) The alkoxycarbonylation reaction formula of 1-octene is as follows: ; The specific steps are as follows: 1.12 g (0.01 mol) of 1-octene and 10 mL of methanol were placed in a high-pressure reactor, and 5% Pd / γ-Al2O3, triphenylphosphine, and p-toluenesulfonic acid were added to the high-pressure reactor according to a molar ratio of palladium-based catalyst, phosphine ligand, and acid promoter of 1:60:60 (the molar ratio of 1-octene to palladium in the catalyst was 1000:1). Then, 4.0 MPa of carbon monoxide was introduced, and the reaction was carried out at 100 °C for 5 hours to obtain methyl nonanoate.

[0029] The conversion rate of 1-octene in this reaction process reached 99.83%, and the yield of methyl nonanoate reached 94.07%. The obtained methyl nonanoate was specifically a mixture of n-methyl nonanoate and isomethyl nonanoate (both can be used as raw materials for transesterification reactions), and the n / i ratio was 4:1.

[0030] 2) The reaction equation for the transesterification of methyl nonanoate and neopentyl glycol is as follows: ; The specific steps are as follows: 20.64 g (0.12 mol) of methyl nonanoate obtained from the previous step and 5.20 g (0.05 mol) of neopentyl glycol were added together to a three-necked flask equipped with a water separator (to remove the generated methanol), and then 2.07 g of strong acid ion exchange resin Amberlyst-15 was added. The reaction was carried out at 110 °C for 24 hours to obtain neopentyl glycol dinonanoate.

[0031] The conversion rate of neopentyl glycol in this process reached 99.89%, and the yield of neopentyl glycol dinonanoate was 91.29%.

[0032] It can be seen that after two steps of reaction, the total yield of neopentyl glycol dinonanoate was 85.88% (calculated based on 1-octene).

[0033] The above are only the preferred embodiments of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope covered by the present invention.

Claims

1. A method for preparing neopentyl polyol higher fatty acid ester by a two-step process, characterized in that: It includes the following two steps: (1) Generating the corresponding fatty acid ester through the alkoxycarbonylation reaction of an olefin; (2) Performing a transesterification reaction between the generated fatty acid ester and neopentyl polyol to generate the desired neopentyl polyol fatty acid ester.

2. The method according to claim 1, wherein: The alkoxycarbonylation reaction described in step (1) is specifically carried out in a palladium-based catalytic system. The olefin is dissolved in a lower alcohol, and carbon monoxide is introduced. The reaction is carried out at 60 - 120 °C and a pressure > 1.0 MPa for 2 - 10 hours to generate the fatty acid ester.

3. The method according to claim 2, wherein: The palladium-based catalytic system is composed of a palladium-based catalyst, a phosphine ligand, and an acid promoter in a molar ratio of 1:(10 - 60):(10 - 60).

4. The method according to claim 3, wherein: The content of Pd in the palladium-based catalyst is 5 wt%; The phosphine ligand is selected from any one of triphenylphosphine, 1,2-bis(di-tert-butylphosphinomethyl)benzene, 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene, and diphenyl-2-pyridylphosphine; The acid promoter is benzenesulfonic acid or p-toluenesulfonic acid.

5. The method according to claim 2, wherein: The dosage of the palladium-based catalytic system is calculated according to the molar ratio of palladium contained therein to the olefin of 1:(100 - 2000).

6. The method according to claim 2, characterized in that: The olefin is a long-chain α-olefin having 5 to C 18 .

7. The method according to claim 1, characterized in that: The neopentyl polyol described in step (2) is one or several of neopentyl glycol, trimethylolpropane, pentaerythritol, and dipentaerythritol.

8. The method according to claim 1, characterized in that: The dosage of the neopentyl polyol is calculated according to the molar ratio of the fatty acid ester to the hydroxyl group in the neopentyl polyol of (1.1 - 1.2):

1.

9. The method according to claim 1, wherein: The temperature of the transesterification reaction described in step (2) is 80 - 160 °C, and the time is 12 - 24 h.

10. The method according to claim 1, wherein: An acid also needs to be added as a catalyst in step (2); its dosage is 4 - 12% of the total mass of the fatty acid ester and the neopentyl polyol.

Images