CN1570029A

CN1570029A - Biological diesel fuel preparing method from natural grease

Info

Publication number: CN1570029A
Application number: CNA2004100148876A
Authority: CN
Inventors: 蒋剑春; 聂小安; 杨凯华; 夏建陵
Original assignee: Institute of Chemical Industry of Forest Products of CAF
Current assignee: Institute of Chemical Industry of Forest Products of CAF
Priority date: 2004-05-14
Filing date: 2004-05-14
Publication date: 2005-01-26
Anticipated expiration: 2024-05-14
Also published as: CN1257253C

Abstract

The invention provides a biological diesel fuel preparing method from natural grease by carrying out esterification reaction to natural grease and C1-C3 alcohols, at the presence of inorganic acid catalyst, elevating the temperature to 100-300 deg. C, blending for polymerization reaction 1-8 hours, lower the temperature to 100-240 deg. C, vacuum-pumping, proceeding vacuum distillation.

Description

Method for preparing biodiesel from natural oil

Technical Field

The invention relates to different preparation methods of biodiesel, in particular to a method for preparing biodiesel from natural oil.

Background

Since oils and fats contain fatty acids of various structures, ester products obtained by esterification or transesterification are widely used as industrial raw materials and medicines. The use of fatty acid methyl esters as biodiesel has been studied more, and in JP-A-7-197047 and JP-A-9235573, biodiesel is obtained by esterification using waste edible oils and methanol in the presence of sodium hydroxide. U.S. Pat. No. 4, 5713965 reports that the reaction of oil and methanol in hexane is carried out by using lipase as catalyst to obtain biodiesel. Chinese patent CN1247221A utilizes grease and alcohol to carry out ester exchange reaction under the condition of no catalyst and at least the grease and the alcohol are in a supercritical state, thus obtaining the biodiesel. From fatty acid ester participating in polymerization reaction in the prior art, methyl esterification products of any single grease such as rapeseed oil, cottonseed oil and soybean oil can be polymerized independently, but after dimerization reaction of the single grease, due to transition reaction of double bonds, fatty acid methyl ester as biodiesel contains too much saturated acid, has too high freezing point, is easy to solidify in winter, and is not beneficial to application of the biodiesel; in addition, the biodiesel prepared by the method has the defects of high glycerin content and iodine value, and the production cost of the methods is high.

Technical content

The invention provides a method for preparing biodiesel from natural oil, which can reduce the production cost and improve the quality of the obtained biodiesel.

The invention adopts the following technical scheme:

a method for preparing biodiesel from natural oil is to carry out esterification reaction on the natural oil and alcohol with molecular weight of 1-3 carbon atoms, and is characterized in that an esterification product, namely fatty acid methyl ester and fatty acid methyl ester containing two or more conjugated double bonds are heated to 100-300 ℃ under the action of an inorganic acid catalyst, and are subjected to blending polymerization reaction for 1-8 hours, then the temperature is reduced to 100-240 ℃, and the vacuum degree is maintained by vacuumizing to be more than 750mmHg, and the distillation product is the biodiesel.

Compared with the prior art, the invention has the following advantages:

the invention adopts the following route to prepare the biodiesel:

(1) methyl esterification reaction

(2) Dimerization reaction

Single or multiple double bond fatty ester + conjugated double bond fatty ester → fatty acid dimer + biodiesel

The invention preserves the advantages of the acid and alkali ester exchange process in the prior art, synthesizes fatty ester, adopts the blending polymerization technology to introduce a conjugated double bond system in order to overcome the defect that excessive saturated acid is caused by single fatty ester transition polymerization, such as: the fatty acid methyl ester containing two or more conjugated double bonds is introduced, the content ratio of saturated acid and unsaturated acid is freely adjusted, fatty acid ester with higher value is obtained through reaction and is separated to obtain the biodiesel, therefore, the fatty acid ester ofthe grease esterification product is not directly used as the biodiesel, but the characteristic of double bonds existing on the structure of the fatty acid ester is fully utilized, and the product with certain profit is firstly prepared, thereby reducing the production cost; the blending polymerization technology is adopted, the proportion of saturated acid and unsaturated acid ester is freely adjusted, and the defects that the saturated acid is too high and the biodiesel is easy to solidify in winter and cannot be used due to transitional polymerization are effectively avoided; in addition, the glycerin content of the biodiesel prepared by the invention is zero, the iodine value is 100, and the glycerin content and the iodine value are both lower than those of the prior art which are more than 0.5 percent. Therefore, the invention improves the quality of the prepared biodiesel.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

Example 1

A method for preparing biodiesel from natural oil comprises performing methyl esterification reaction on natural oil and 1-3 carbon molecular weight to obtain methyl ester of fatty acid and methyl ester of fatty acid containing two or more conjugated double bonds, heating to 100-300 ℃ under the action of an inorganic acid catalyst, carrying out blending polymerization reaction for 1-8 hours, after the reaction is finished, cooling to 100-240 ℃, vacuumizing to keep the vacuum degree above 750mmHg, carrying out reduced pressure distillation to obtain a distillate, namely the biodiesel, the inorganic acid catalyst comprises bisulfate and various types of activated clay, preferably activated clay with the pH value of 3-5, the addition amount of the fatty acid methyl ester is 0-5% of the weight percentage of the natural oil, the fatty acid methyl ester containing two or more conjugated double bonds participating in the blending polymerization reaction can be the methyl esterification products of conjugated linseed oil, Chinese tallow seed oil and tung oil, and the methyl esterification product of the tung oil is preferably methyl eleostearate; methyl esterification of natural oil can be realized by adopting the prior art, the embodiment is that the oil is heated to 80-130 ℃, preferably 70-80 ℃, vacuumized to ensure that the vacuum degree is above 750mm mercury column for decompression dehydration for 1-8 hours, preferably 4 hours, cooled to 0-50 ℃, added with 1-3 carbon molecular weight alcohol and 0.1-5% of inorganic catalyst relative to the weight percentage of the oil ester according to the oil/alcohol molar ratio of 1: 3-1: 10, heated to 50-100 ℃, subjected to reflux reaction for 1-8 hours, after the reaction is finished, unreacted alcohol is evaporated, a product is cooled to 0-50 ℃, and kept stand until the reaction liquid is layered, and the lower layer of glycerin is separated out to obtain fatty acid ester; the inorganic catalyst can be strong acid or strong base, and the strong acid comprises: 98% concentrated sulfuric acid, anhydrous phosphoric acid, solid super acid and the like, preferably solid super acid; the strong base is as follows: potassium hydroxide, sodium hydroxide, calcium hydroxide, preferably potassium hydroxide; the 1-3 carbon molecular weight alcohol can be methanol, ethanol, isopropanol, etc., preferably methanol; the molar ratio of oil to alcohol is preferably 1: 6, and the natural oil comprises oleum Rapae, oleum gossypii semen, Chinese tallow tree seed oil and waste oil, preferably oleum Rapae; different grease is subjected to ester exchange, and different catalysts can be adopted to promote the smooth reaction; for example, potassium hydroxide is used for rapeseed oil, solid super acid is used for cottonseed oil, and 98% concentrated sulfuric acid is used for waste grease; their methyl esterification products can also be polymerized using different catalysts, such as methyl rapeseed oil with waste oil activated clay, cotton seed oil with sodium bisulfite.

Example 2

Adding 300 g of rapeseed oil into a three-necked flask with a vacuum dehydration device, a thermometer and a reflux condenser, heating to a preferred temperature of 120 ℃, carrying out reduced pressure dehydration for 1-2 hours, cooling to 50 ℃, adding 100 g of methanol and 2.4 g of potassium hydroxide, carrying out reflux reaction for 4 hours, recovering excessive methanol, cooling to 50 ℃, standing for 1-2 hours, and separating out lower-layer glycerol to obtain 290 g of fatty acid methyl ester.

290 g of fatty acid methyl ester and 145 g of eleostearic acid methyl ester are added into a three-necked flask with a thermometer and a stirrer, a small amount of activated clay and distilled water are added, the temperature is preferably 240 ℃, the reaction is preferably 8 hours, and the reduced pressure distillation is carried out, so as to obtain 270 g of dimer acid methyl ester and 165 g of light yellow biodiesel.

270 g of dimer acid methyl ester and 405 g of Mannich modified amine are added into a three-neck flask with a thermometer and a stirrer, heated to 180 ℃, and reacted for about 6 hours until no methanol flows out, thus obtaining 640 g of brown yellow viscous liquid, namely the epoxy resin flexible curing agent polyamide.

Example 3

Adding 298 g of cottonseed oil into a three-necked flask with a vacuum dehydration device, a thermometer and a reflux condenser, heating to 120 ℃, dehydrating under reduced pressure for 1-2 hours, cooling to 50 ℃, adding 100 g of methanol and 2.4 g of solid superacid, carrying out reflux reaction for 4 hours, recovering excessive methanol, cooling to 50 ℃, standing for 1-2 hours, and separating out lower-layer glycerol to obtain 285 g of fatty acidmethyl ester.

288 g of fatty acid methyl ester and 144 g of eleostearic acid methyl ester are added into a three-neck flask with a thermometer and a stirrer, and a small amount of NaHSO is added₃Heating to 240 deg.c, reaction for 8 hr, and vacuum distillation to obtain methyl dimer acid 265 g and yellowish biodiesel 160 g.

265 g of dimer acid methyl ester and 400 g of Mannich modified amine are added into a three-neck flask with a thermometer and a stirrer, heated to 180 ℃, and reacted for about 6 hours until no methanol flows out, thus obtaining 630 g of brown yellow viscous liquid, namely the epoxy resin flexible curing agent polyamide.

Example 4

Adding 296 g of waste oil into a three-necked flask with a vacuum dehydration device, a thermometer and a reflux condenser, heating to 120 ℃, carrying out reduced pressure dehydration for 1-2 hours, cooling to 50 ℃, adding 100 g of methanol and 2.4 g of 98% concentrated sulfuric acid, carrying out reflux reaction for 4 hours, recovering excessive methanol, cooling to 50 ℃, standing for 1-2 hours, and separating out lower-layer glycerol to obtain 288 g of fatty acid methyl ester.

285 g of fatty acid methyl ester and 140 g of eleostearic acid methyl ester are added into a three-necked flask with a thermometer and a stirrer, a small amount of activated clay and distilled water are added, the temperature is increased to 240 ℃, the reaction lasts for 8 hours, and reduced pressure distillation is carried out, thus obtaining 272 g of dimer acid methyl ester and 163 g of light yellow biodiesel.

272 g of dimer acid methyl ester and 406 g of Mannich modified amine are added into a three-neck flask with a thermometer and a stirrer, heated to 180 ℃, and reacted for about 6 hours until no methanol flows out, thus obtaining 642 g of brown yellow viscous liquid, namely the epoxy resin flexible curing agent polyamide.

The epoxy resin curing agent polyamide prepared by the invention is widely applied to the industries of adhesives, anticorrosive coatings, electronic encapsulation and the like. Because the domestic cheap raw material amine is used for replacing imported triethylene tetramine and diethylene triamine, the price is more competitive.

Claims

1. A method for preparing biodiesel from natural oil is to carry out esterification reaction on the natural oil and alcohol with molecular weight of 1-3 carbon atoms, and is characterized in that an esterification product, namely fatty acid methyl ester and fatty acid methyl ester containing two or more conjugated double bonds are heated to 100-300 ℃ under the action of an inorganic acid catalyst, and are subjected to blending polymerization reaction for 1-8 hours, then the temperature is reduced to 100-240 ℃, and the vacuum degree is maintained by vacuumizing to be more than 750mmHg, and the distillation product is the biodiesel.

2. The method for preparing biodiesel from natural oil according to claim 1, wherein the methyl esterification reaction of natural oil is carried out as follows:

heating the grease to 80-130 ℃, vacuumizing to enable the vacuum degree to be more than 750mm mercury columns, carrying out reduced pressure dehydration for 1-8 hours, cooling the grease to 0-50 ℃ after dehydration is finished, adding 1-3 carbon molecular weight alcohol and 0.1-5% of inorganic catalyst relative to the weight percentage of the grease according to the oil/alcohol molar ratio of 1: 3-1: 10, heating to 50-100 ℃, carrying out reflux reaction for 1-10 hours, evaporating unreacted low molecular weight alcoholafter the reaction is finished, cooling the product to 0-50 ℃, standing until the reaction liquid is layered, and separating out lower-layer glycerol to obtain the fatty acid ester.

3. The method for preparing biodiesel from natural oil according to claim 2, wherein the inorganic catalyst used for the transesterification reaction is a strong acid.

4. The method for preparing biodiesel from natural oil according to claim 2, wherein the inorganic catalyst for transesterification reaction is strong base.

5. The method of claim 1, wherein the fatty acid methyl ester containing two or more conjugated double bonds involved in the blending polymerization is methyl eleostearate, which is a methyl esterification product of tung oil.

6. The process according to claim 1, wherein the inorganic acidic catalyst used in the co-polymerization is activated clay having a pH of 3 to 5.

7. The method according to claim 1, wherein said natural oil is rapeseed oil.