CN101249432A - A kind of solid base catalyst and its application in preparing biodiesel - Google Patents

Abstract

The invention discloses a solid base catalyst and its application in the preparation of biodiesel. The catalyst is obtained by performing a solid phase reaction between metal nitrate and alkali or alkali metal carbonate, and roasting at high temperature; the biodiesel is obtained by transesterification Preparation method, adding grease, low-carbon alcohol, and solid alkali catalyst into a three-neck container, heating and reflux stirring, filtering the material, filtering out the catalyst, separating the filtrate, separating the lower layer of glycerin, adding NaHCO ₃ solution to the upper layer mixture, and washing To neutrality, dry with anhydrous MgSO ₄ , and distill under reduced pressure to obtain biodiesel. The catalyst of the invention has the advantages of high yield, low catalyst cost and small catalyst consumption, mild reaction conditions and short reaction time, reusable catalyst, no environmental pollution and low requirements on raw materials.

Description

A kind of solid base catalyst and its application in preparing biodiesel

technical field

The invention relates to the technical field of organic chemical synthesis, in particular to a solid base catalyst and its application in preparing biodiesel.

Background technique

With the decreasing mineral resources such as petroleum and their impact on the earth's environment, the development of new green and renewable fuel resources has become an issue of widespread concern. Biodiesel is a mono-alkyl ester of long-chain fatty acid, free of sulfur and aromatics, high cetane number, and good lubricating performance, it is a high-quality clean fuel. At the same time, biodiesel has incomparable advantages over traditional fossil fuels. The raw material is renewable biomass oil. The product itself is environmentally friendly, biodegradable, high flash point, non-toxic, low in volatile organic compounds (VOC), and has a high calorific value. High, complete combustion, no need to replace and clean the engine frequently, and it is also a raw material for the manufacture of biodegradable fine chemical products with high added value. The most important environmental effect of biodiesel is in an indirect way, through the re-conversion of CO ₂ to hydrocarbons, so that the net CO ₂ emissions are greatly reduced. Scientists believe that the use of biomass raw material energy is a more effective and effective strategy than increasing forest resources (as CO2 absorption). The production method of biodiesel is mainly prepared by the transesterification reaction of vegetable oil or animal fat and low carbon alcohol. Commonly used catalysts mainly include acid catalysis, base catalysis, enzyme catalysis and supercritical method. Acid-catalyzed method [Ono, YJCatal, 2003, 216 (1-2): 406] often adopts sulfuric acid and the like, and there is a large amount of alcohol, which leads to difficulties in product stratification, high reaction temperature, and poor catalytic efficiency. Alkali catalysis [Sheng Mei et al., Journal of Chemical Engineering of Colleges and Universities, 2004, 18 (2): 231-236] mostly adopts homogeneous catalysts such as NaOH, KOH, sodium methylate, etc., which have strict requirements on raw materials and require anhydrous and acid-free catalysts. Harsh conditions, saponification phenomenon, product post-processing and other disadvantages. Enzyme catalysis [Nie Kaili et al., Bioprocessing, 2005, 3(1): 58-62] has disadvantages such as expensive catalyst, easy deactivation, and long reaction time. In the supercritical non-catalytic method, the reaction temperature and pressure exceed the critical temperature and critical pressure of methanol, and the production process requires high equipment. Generally, the synthesis of supported solid bases involves dissolving the active components in water first, then impregnating them, and then filtering or evaporating the water under reduced pressure, which is a cumbersome process, which is time-consuming, energy-consuming, and wastes a lot of raw materials.

Contents of the invention

The purpose of the present invention is to provide a kind of solid base catalyst for the deficiencies in the prior art, and at the same time the catalyst is used for the preparation of biodiesel, the preparation of the catalyst is simple and easy, the preparation of biodiesel yield is high, the catalyst consumption is small and can be reuse.

The concrete technical scheme that realizes the object of the invention is:

A solid base catalyst, which is obtained by grinding metal nitrate and alkali or alkali metal carbonate at room temperature for solid-state reaction, and then roasting at high temperature; the specific method is: mix metal nitrate and alkali or alkali metal carbonate Put it in a mortar, the mass ratio of metal nitrate to alkali or alkali metal carbonate is 1-12:10, grind at room temperature for 1-2 hours, and then roast in a muffle furnace at 300-1000°C for 5-10 hours , That is, the metal nitrate is magnesium nitrate, aluminum nitrate, zinc nitrate, calcium nitrate or strontium nitrate; the alkali or alkali metal carbonate is sodium hydroxide, potassium hydroxide, sodium carbonate or potassium carbonate.

The application of the above-mentioned solid base catalyst in the preparation of biodiesel. The biodiesel is prepared by transesterification. The specific steps are: add grease, low-carbon alcohol, and solid base to a three-neck container equipped with electromagnetic stirring, a thermometer, and a reflux condenser. The catalyst is heated and refluxed and stirred for 1-3 hours; the heating temperature is controlled at 50-110°C; the reacted material is filtered, the catalyst and the filtrate are filtered out, the filtrate is separated, and the lower layer of glycerin is separated, and the mass fraction of the upper layer is added to the mixture. 10% NaHCO ₃ solution, the amount of which is added is 2 to 6 times the mass of the upper layer mixture, washed to neutrality, and unreacted free fatty acids are removed, then the upper organic phase is separated with a separatory funnel, and the organic phase is washed with anhydrous MgSO ₄ drying, filtering to remove the desiccant, and distillation under reduced pressure to obtain a nearly light yellow transparent product which is biodiesel.

The mass ratio of the added oil, low-carbon alcohol and solid base catalyst is 1:0.1-0.5:0.04-0.1.

The oil is vegetable oil, animal fat or waste oil and waste oil in the production process.

The low-carbon alcohol is methanol, ethanol, propanol or butanol.

After the reaction of the present invention is finished, the filtered catalyst can be reused, the activity remains basically unchanged, and the reaction yield can still reach more than 90%.

The synthetic reaction formula of biodiesel of the present invention is as follows:

Compared with the background technology, the advantages of the present invention are: the catalyst has uniform distribution of active components, high utilization rate of raw materials, and simple synthesis method; the advantages of the catalyst for biodiesel synthesis are: (1) high yield; (2) catalyst Cheap, small amount of catalyst, about 0.5-3% of the total weight of the reaction raw materials; (3) mild reaction conditions, short reaction time; (4) catalyst can be reused; (5) no environmental pollution; (6) requirements for raw materials Low.

Detailed ways

The present invention will be further elaborated below by specific embodiment:

Example 1

Preparation of the 1st step solid base catalyst

Put 6g of magnesium nitrate and 10g of potassium hydroxide in a mortar, grind it at room temperature for about 1 hour, and then roast it in a muffle furnace at 800°C for 5 hours to obtain it.

Step 2 transesterification reaction

Add 5g of rapeseed oil, 1.5g of methanol, and 0.1g of the above-mentioned solid base catalyst into a 100mL three-necked flask equipped with electromagnetic stirring, a thermometer, and a reflux condenser, heat under reflux and stir for 2 hours, and heat to 90°C.

Step 3 Separation of catalyst and purification of product

The material in the three-necked bottle is filtered, and the catalyst filtered out can be directly used in the next reaction. The filtrate is separated to separate the lower layer of glycerol, and the upper layer mixture is added with a mass fraction of 6% NaHCO ₃ solution 70ml is washed to neutrality to remove The unreacted free fatty acid is separated from the upper organic phase with a separatory funnel, dried with anhydrous MgSO ₄ , filtered to remove the desiccant, and distilled under reduced pressure to obtain a nearly light yellow transparent product, which is biodiesel. The yield was 98.3%.

Example 2-6

Except following difference, all the other are identical with embodiment 1, in the process of preparing catalyst, magnesium nitrate is by the consumption of table 1.

Table 1

Examples 7-11

Except for the following differences, all the other are the same as in Example 1, using the nitrates shown in Table 2 respectively.

Table 2

Examples 12-15

Except for the following differences, all the other are the same as in Example 1, using the alkali or carbonate shown in Table 3 respectively.

table 3

Example 16-20

Except for the following differences, the rest are the same as in Example 1, using the bio-grease shown in Table 4 respectively.

Table 4

Examples 21-25

Except following difference, all the other are identical with embodiment 1, adopt respectively the low carbon alcohol shown in table 5.

table 5

Examples 26-30

Except for the following differences, the rest are the same as in Example 1, and the results of the impact of the repeated use of the catalyst on the reaction are shown in Table 6.

Table 6

Claims (2)

1, a kind of solid base catalyst is characterized in that: after metal nitrate and alkali or alkali carbonate are at room temperature ground solid phase reaction, and high-temperature roasting and getting; The concrete practice is: metal nitrate and alkali or alkali carbonate are placed mortar, metal nitrate is 1～12: 10 with the ratio of the quality of alkali or alkali carbonate, under room temperature, grind 1～2h, 300～1000 ℃ of following roasting 5～10h in the Muffle furnace then, promptly; Described metal nitrate is magnesium nitrate, aluminum nitrate, zinc nitrate, calcium nitrate or strontium nitrate; Described alkali or alkali carbonate are NaOH, potassium hydroxide, sodium carbonate or potash.

2, the application of the described solid base catalyst of a kind of claim 1 in the preparation biodiesel, it is characterized in that biodiesel adopts the ester-interchange method preparation, concrete steps are: add grease, low-carbon alcohols, solid base catalyst and add hot reflux and stir 1～3h in the three neck containers that have electromagnetic agitation, thermometer, reflux condensing tube; Heating and temperature control is at 50～110 ℃; With reacted material filtering, leach catalyst and filtrate, filtrate is carried out separatory, tells lower floor's glycerine, and the adding mass fraction is 5～10% NaHCO in the mixture of upper strata ₃Solution, its addition are 2～6 times of upper strata mixture quality, and washing is removed unreacted free fatty to neutral, tells upper organic phase with separatory funnel again, with organic facies with anhydrous MgSO ₄Drying removes by filter drier, and decompression distillation obtains nearly light yellow opaque products and is biodiesel; The mass ratio of described adding grease, low-carbon alcohols, solid base catalyst is 1: 0.1～0.5: 0.04～0.1; Described grease is waste oil, the waste oil in vegetable fat, animal tallow or the production process; Described low-carbon alcohols is methyl alcohol, ethanol, propyl alcohol or butanols.