CN108863785A - A kind of low pour point pentaerythritol oleate mixed ester and its synthetic method - Google Patents

Abstract

The invention discloses a low pour point pentaerythritol oleate mixed ester, the main component of which is a pentaerythritol trioleate maleic acid monoester mixed ester, which maintains three long carbon chain oleic acid groups in the structure, and simultaneously introduces a maleic acid group The cis double bond structure or double bond structure plus branched chain structure of the acid increases the number of double bonds per unit mass or increases the branched chain structure, thereby reducing the pour point. The synthesis method comprises the following steps: first adding oleic acid and pentaerythritol to react according to the molar ratio of oleic acid to pentaerythritol of 3; then adding maleic acid monoester to completely block unreacted hydroxyl groups; Remove water agent to obtain light yellow oily transparent liquid pentaerythritol trioleate maleic acid monoester mixed ester. The present invention synthesizes pentaerythritol oleate mixed ester through two-step esterification reaction, the main component is pentaerythritol oleate maleic acid monoester mixed ester, the product viscosity is lower than pentaerythritol tetraoleate, and the pour point is lower than pentaerythritol oleate ; Simultaneously in the present invention, the raw material is cheap and easy to get, the performance is stable, the operation is simple, and it is easy to realize industrially.

Description

A kind of pentaerythritol oleate mixed ester with low pour point and its synthetic method

technical field

The invention relates to the field of fine organic chemical industry, in particular to a low pour point pentaerythritol oleate mixed ester and a synthesis method thereof.

Background technique

Pentaerythritol tetraoleate has excellent lubricating properties, good flame resistance, low volatility, biodegradation rate greater than 90%, pour point -32°C. The high-quality base oil can be used as the base oil of synthetic ester type fire-resistant hydraulic oil and the base oil of aviation engine lubricating oil.

Low temperature fluidity is an important property of lubricating oil, expressed by pour point. The pour point refers to the lowest temperature at which the cooled sample of the oil can flow under the specified test conditions. Oils with a high pour point are not suitable for application in cold regions. The low-temperature fluidity of ester oil is related to the structure. The literature "Contemporary Chemical Industry" Volume 44, No. 7 P1570-1572 "Study on the Effect of Structure of Ester Lubricating Oil on Performance" shows that for diester compounds, the branched carbon chain at both ends Chemicalization can improve the low-temperature fluidity of the oil, and the existence of double bonds can improve the low-temperature fluidity of the oil to a certain extent. In the Chinese invention patent application CN 107735484A, trimethylolpropane ester of C9 or C10 monocarboxylic acid was synthesized, wherein C9 or C10 monocarboxylic acid contained 5-15mol% branched chain acid and 85-95mol% straight chain acid (relative to in total moles of monocarboxylic acid). For example, when the molar ratio of nonanoic acid to 3,5,5-trimethylhexanoic acid is 9:1, the pour point of trimethylolpropane mixed ester is lower than -54°C. In Chinese patent CN102203225B, branched 2-propylheptanoic acid is directly esterified with pentaerythritol and trimethylolpropane to obtain tetra-2-propylheptanoate of pentaerythritol (tetraester content 97~98%), three Tri-2-propylheptanoate of hydroxymethylpropane (triester content 97%), both have very low pour points, -56°C and -52°C respectively, but both have relatively small viscosity indexes, the former 110, the latter 89, the biodegradation rate has not been reported, and it belongs to the ester oil of low quality. In the document "Lubrication and Sealing", Volume 36, No. 2 P1-3 "Synthesis and Properties of Pentaerythritol Oleic Acrylic Acid Mixed Ester", a pentaerythritol oleic acid mixed ester polymer was synthesized by a two-step method. The first step: one-pot reaction of pentaerythritol, oleic acid and acrylic acid to obtain the mixed ester; the second step: in the presence of the initiator azoisobutyronitrile, the double bond of acrylic acid is polymerized. In the first step, it is deacidified by washing with saturated sodium bicarbonate solution and washing with distilled water. However, the acrylic acid introduced in this document has an unstable structure, which is equivalent to a terminal olefin, and the terminal olefin is easy to polymerize, resulting in a gradual increase in the viscosity of the oil during use, and eventually even polymer precipitation.

The prior art shows that pentaerythritol tetraoleate is a base oil with good performance, and its synthesis method has been reported in literature. There is no literature report on the work of modifying the structure of pentaerythritol tetraoleate, introducing the structure of maleic acid monoester, and obtaining the mixed pentaerythritol oleic acid monoester maleate with low pour point.

Contents of the invention

The object of the present invention is to provide a pentaerythritol oleate mixed ester with high biodegradation rate, high viscosity, low volatilization, high flash point, high viscosity index and very low pour point and a synthesis method thereof.

The technical scheme that the present invention adopts is: a kind of low pour point pentaerythritol oleic acid ester mixed ester, it is characterized in that: its main component is pentaerythritol trioleate maleic acid monoester mixed ester, keeps three long carbon chains in the structure The oleic acid group is introduced into the cis double bond structure or double bond structure and branched chain structure of maleic acid at the same time, so that the number of double bonds per unit mass or the branched chain structure increases, thereby reducing the pour point.

The synthesis method of pentaerythritol oleate mixed ester with low pour point of the present invention comprises the following steps: in the first step, oleic acid and pentaerythritol are added according to the molar ratio of oleic acid and pentaerythritol being 3, and the reaction is carried out under the conditions of adding a catalyst and a water-carrying agent; In the second step, add maleic acid monoester to block all the unreacted hydroxyl groups. The molar ratio of oleic acid: pentaerythritol: maleic acid monoester is 3:1:1.1~1.2; the third step is complete and then cooled Return to room temperature, wash with water, remove the water-carrying agent from the organic layer in vacuum, and obtain a light yellow oily transparent liquid pentaerythritol trioleate maleic acid monoester mixed ester.

Maleic acid monoester in the present invention refers to maleic acid monoester refers to monomethyl maleate, monoethyl maleate, methyl monomethyl maleate, methyl monoethyl maleate A mixture of one or more of esters, 2,3-dimethylmaleic acid monomethyl ester, 2,3-dimethylmaleic acid monoethyl ester.

The catalyst of the present invention is p-toluenesulfonic acid, and the dosage is 5‰ of the mass fraction of oleic acid; the water-carrying agent is petroleum ether.

The heating temperature of the first step of the present invention is 110-140°C, preferably 130-135°C, and the reaction time is 2.0-6.0 hours, preferably 3.0h; the reaction temperature of the second step is 110-140°C, preferably 130-135 °C, the reaction time is 1.0-3.0 hours, preferably 2.0 hours.

The invention adopts two-step esterification reaction to synthesize pentaerythritol trioleate maleate monoester mixed ester. details as follows:

The first step: According to the material ratio of oleic acid and pentaerythritol molar ratio is 3, add oleic acid and pentaerythritol, mainly generate pentaerythritol trioleate, containing a small amount of pentaerythritol tetraoleate and pentaerythritol dioleate:

The second step: add maleic acid monoester again, and seal the hydroxyl group remaining in the pentaerythritol trioleate molecule to generate pentaerythritol trioleate maleic acid monoester mixed ester:

.

The introduction of branched chain structure or double bond (especially cis double bond) in the present invention destroys the symmetry of molecular arrangement, lowers the crystallization temperature and lowers the pour point. The molecular weight of maleic acid is smaller than that of oleic acid, and it has a cis double bond structure. In addition to the cis double bond, there are branches in the structure of 2,3-dimethylmaleic acid. Pentaerythritol tetraoleate has a molecular weight of 1194, four oleic acid double bonds, and one double bond in the average mass of 298.5. One of the products of the present invention, pentaerythritol trioleate monomethyl maleate mixed ester molecular weight 1040, also has 4 double bonds, and there is a double bond in the average mass of 260, and the double bond increases in the visible unit mass, so the present invention obtains Pentaerythritol trioleate maleate mixed ester has a lower pour point. Maleic acid is chemically stable, the double bond is not easy to oxidize, and it is not easy to polymerize.

The innovation of the present invention is that the pentaerythritol trioleate maleic acid monoester mixed ester maintains three long carbon chain oleic acid groups in the structure to ensure high viscosity, high viscosity index and high biodegradation rate, while introducing The cis double bond structure or double bond structure plus branched chain structure of maleic acid, due to the relatively small molecular weight of maleic acid, increases the number of double bonds per unit mass or increases the branched chain structure, thereby reducing the pour point.

The product obtained by this method has unique high quality: high biodegradation rate, high viscosity, low volatility, high flash point, high viscosity index and low pour point. Its main component is pentaerythritol trioleate maleate monoester mixed ester, and it also contains a small amount of pentaerythritol tetraoleate and pentaerythritol dioleate dimaleate monoester mixed ester, and the mixture does not need to be separated. At the same time, the raw materials in the present invention are cheap and easy to obtain, stable in performance, simple in operation and easy to realize industrially.

Detailed ways

The present invention will be further described according to specific embodiments below:

Example 1:

Add 136.2g of pentaerythritol and 847.3g of oleic acid successively into the reactor, add catalyst and water agent, control the heating temperature of the oil bath at 130-135°C, under the protection of nitrogen, stir and reflux, divide the water for 3.0-4.0 hours, cool slightly, Add 143.1 g of monomethyl maleate, raise the temperature to 130-135° C., and stir to separate water for 2 hours. After the reaction is complete, cool to room temperature, wash with water, remove the water-carrying agent from the organic layer in vacuum, and obtain a light yellow oily transparent liquid with a biodegradation rate of more than 90%, a pour point of less than -40°C, and a yield of 99%.

Example 2:

Add 136.2g of pentaerythritol and 847.3g of oleic acid successively into the reactor, add catalyst and water agent, control the heating temperature of the oil bath at 130-135°C, under the protection of nitrogen, stir and reflux, divide the water for 3.0-4.0 hours, cool slightly, Add 158.5 g of monoethyl maleate, raise the temperature to 130-135° C., and stir to separate water for 2 hours. After the reaction is complete, cool to room temperature, wash with water, remove the water-carrying agent from the organic layer in vacuum, and obtain a light yellow oily transparent liquid with a biodegradation rate of more than 90%, a pour point of less than -40°C, and a yield of 99%.

Example 3:

Add 136.2g of pentaerythritol and 847.3g of oleic acid successively into the reactor, add catalyst and water agent, control the heating temperature of the oil bath at 130-135°C, under the protection of nitrogen, stir and reflux, divide the water for 3.0-4.0 hours, cool slightly, Add 173.9 g of 2,3-dimethylmaleic acid monomethyl ester, raise the temperature to 130-135° C., stir for 2 hours to separate water. After the reaction is complete, cool to room temperature, wash with water, remove the water-carrying agent from the organic layer in vacuum, and obtain a light yellow oily transparent liquid with a biodegradation rate of more than 90%, a pour point of less than -40°C, and a yield of 99%.

Example 4:

Add 136.2g of pentaerythritol and 847.3g of oleic acid successively into the reactor, add catalyst and water agent, control the heating temperature of the oil bath at 130-135°C, under the protection of nitrogen, stir and reflux, divide the water for 3.0-4.0 hours, cool slightly, Add 71.6g of monomethyl maleate and 87.0g of 2,3-dimethyl monomethyl maleate, raise the temperature to 130-135°C, and stir to separate water for 2 hours. After the reaction is complete, cool to room temperature, wash with water, remove the water-carrying agent from the organic layer in vacuum, and obtain a light yellow oily transparent liquid with a biodegradation rate of more than 90%, a pour point of less than -40°C, and a yield of 99%.

The embodiments described in the present invention are not only a description of the preferred implementation of the present invention, but are not intended to limit the concept and scope of the present invention. Various modifications and improvements made in the scheme should fall within the protection scope of the present invention, and the technical content claimed in the present invention has been fully recorded in the claims.

Claims (6)

1. a kind of low pour point pentaerythritol oleate mixed ester, it is characterised in that：Its main component is three oleic acid horse of pentaerythrite Carry out acid monoester mixed ester, keep the oleic acid moieties of three Long carbon chains in the structure, while introducing the cis-double bonds structure of maleic acid Or double bond structure adds branched structure, so that double bond quantity increases in unit mass or branched structure increases, to reduce pour point.

2. the synthetic method of low pour point pentaerythritol oleate mixed ester as described in claim 1, it is characterised in that including as follows Step：The first step is 3 oleic acid and pentaerythrite to be added by oleic acid and pentaerythrite molar ratio, and catalyst, water entrainer is being added Under the conditions of reacted；Second step adds maleic acid monoester, the complete hydroxyl of unreacted is all closed, wherein oleic acid：Season Penta tetrol：The molar ratio of maleic acid monoester is 3：1：1.1~1.2；It is cooled to room temperature, washes, organic layer after third step fully reacting Vacuum sloughs water entrainer, obtains three oleic acid maleic acid monoester mixed ester of pale yellowish oil transparency liquid pentaerythrite.

3. synthetic method according to claim 2, it is characterised in that：The maleic acid monoester refers to maleic acid list first Ester, ethyl maleate, citraconic acid mono-methyl, citraconic acid mono ethyl ester, 2,3- dimethyl maleic acid mono-methyl, 2,3- One of dimethyl maleic acid mono ethyl ester or a variety of mixtures.

4. synthetic method according to claim 2, it is characterised in that：The catalyst is p-methyl benzenesulfonic acid, and dosage is oil The 5 ‰ of acid mass fraction；The water entrainer is petroleum ether.

5. synthetic method according to claim 2, it is characterised in that：The heating temperature of the first step is 110-140 DEG C, reaction Time is 2.0-6.0 hours；Second step reaction temperature is 110-140 DEG C, and the reaction time is 1.0-3.0 hours.

6. synthetic method according to claim 5, it is characterised in that：First step heating temperature is 130-135 DEG C, when reaction Between be 3.0h；Second step reaction temperature is 130-135 DEG C, reaction time 2.0h.