CN1786117A

CN1786117A - Method of preparing biological diesel oil by methanol critical low alkali process

Info

Publication number: CN1786117A
Application number: CNA2005100412676A
Authority: CN
Inventors: 邬国英; 林西平; 李为民; 周永生
Original assignee: Jiangsu Polytechnic University
Current assignee: Jiangsu Polytechnic University
Priority date: 2005-08-01
Filing date: 2005-08-01
Publication date: 2006-06-14
Anticipated expiration: 2025-08-01
Also published as: CN100365100C

Abstract

The present invention belongs to a new process for preparing biological energy. It is characterized by that said invention adopts vegetable oil and critical methyl alcohol, under the catalysis of minute quantity of alkali whose added quantity is 0.05%-0.1% makes the vegetable oil and critical methyl alcohol implement ester exchange reaction so as to obtain neutral crude product biological diesel oil and by-product glycerin.

Description

The method of preparing biological diesel oil by methanol critical low alkali process

Technical field

The invention belongs to the bioenergy new preparation process, refer in particular to a kind of method of preparing biological diesel oil by methanol critical low alkali process.

Background technology

Biofuel is a kind of alternative petrifaction diesel, reproducible clean fuel.Available vegetable and animals oils, waste edible oil etc. carry out transesterification reaction for alcohol such as raw material and methyl alcohol, ethanol, and product is fatty acid methyl ester (back abbreviation methyl esters), and byproduct is a glycerine.Traditional transesterification reaction adopts homogeneous catalyst, as NaOH, KOH, sodium methylate etc., is about 1% in the vegetables oil consumption, temperature of reaction generally is the boiling point of methyl alcohol, in 1 hour reaction times, the transformation efficiency height reaches more than 95%, but also exist significant disadvantages simultaneously, though the base catalysis method reacts easy usually, in order to remove alkaline catalysts, the aftertreatment of reaction solution is very cumbersome, product need neutralize washing and bring a large amount of trade effluents, causes environmental pollution.Yuichiro W. is at " Yuichiro Warabi, DadanKusdiana, Shiro Saka, Bioresource Technology 91 (2004) 283-287 " lipid acid and the reaction of triglyceride level in supercritical alcohols in the research rape seed oil in the article, propose to carry out transesterification reaction with overcritical on-catalytic method, reaction times is short, transformation efficiency can reach more than 95%, and product does not need washing, and aftertreatment is simple, but molar ratio of methanol to oil reaches 42/1, temperature of reaction is 350 ℃, and pressure is 20MPa.Surpass the critical temperature and the emergent pressure of methyl alcohol, production technique is to the equipment requirements height.Transesterification reaction prepares the biodiesel processes report under the another kind of catalyst-free, M.Diasakou etc. are at (M.Diasakou, A.Louloudi, N.Papayannakos, Fuel 1998 vol.77.No.12 pp.1297-1302) point out during the kinetics of research soya-bean oil transesterification reaction under catalyst-free in the article: when methyl alcohol and soya-bean oil mol ratio are 27/1, in 10 hours reaction times, the content of methyl esters reaches 65% during 220 ℃ of temperature of reaction; When methyl alcohol and soya-bean oil mol ratio are 27/1, in 10 hours reaction times, the content of methyl esters reaches 85% during 235 ℃ of temperature of reaction.This work also has supercritical methanol technology aftertreatment characteristic of simple, and molar ratio of methanol to oil and temperature of reaction and pressure ratio supercritical methanol technology are low, but the reaction times is longer, and the content of methyl esters is lower.

Summary of the invention

The purpose of this invention is to provide a kind of critical little base catalysis legal system of on base catalysis method and supercritical methanol technology basis, developing and be equipped with biofuel, this method is because there is micro-base catalysis, both had overcritical aftertreatment characteristic of simple, the product aftertreatment of reaction back need not neutralization washing, environmentally safe, low because of temperature of reaction and pressure ratio supercritical methanol technology again, heat-up time is shorter, and the content of methyl esters is higher, and energy consumption is low, the technology that operation is simple, cost is low is easier to the advantage of industrialization.

The technical scheme that realizes above-mentioned purpose is:

Little or low alkaline catalysts is an alkali metal hydroxide, as: NaOH, KOH, sodium methylate etc. are dissolved in the little alkaline solution of preparation in 2～3ml methyl alcohol, add-on 0.1～0.05% (weight with vegetables oil is standard metering).At 240 ± 5 ℃ of temperature of reaction, pressure is 6.9～7.0Mpa, methyl alcohol: the vegetables oil mol ratio is under 42～21: 1 the condition, to add alkaline solution in a subtle way, in the autoclave pressure that band stirs, carry out transesterification reaction after 100～120 minutes, steam unreacted methanol, quiescent settling divides two-layer up and down then.Lower floor is a coarse biodiesel, sampling analysis methyl esters content; The upper strata is a raw glycerine, and sampling analysis glycerol content, the transformation efficiency of transesterification reaction are 99～97%.The biofuel product that makes meets 0# diesel oil main performance index.

The invention has the beneficial effects as follows:

(1) low alkaline catalysts adds, and reaction product two layers of solution up and down is that thick product biofuel and byproduct glycerine pH 6～7 are neutral, thus need not the neutralization washing, without sewage discharge, subsequent disposal is simplified greatly, and is the same with supercritical methanol technology;

(2) temperature of reaction is 240 ± 5 ℃, and pressure is 6.9～7.0Mpa, at the methanol critical state, molar ratio of methanol to oil is reduced to 42～21: 1, and all low than supercritical methanol technology, energy consumption reduces simultaneously, the withstand voltage heatproof of conversion unit is required to reduce, and yield 99～97% easier industrialization of methyl esters.

(3) glycerol content of upper strata raw glycerine is than base catalysis method and supercritical methanol technology height, and the content of glycerine makes separating and the simplification greatly of purifying of methyl esters and glycerine up to more than 91%.

Description of drawings

Fig. 1 is the process flow diagram of the low alkaline process of critical methanol

Embodiment

Embodiment 1

In 1L band magnetic agitation autoclave pressure, add thick rapeseed oil 100.0 grams, industrial grade benzenemethanol 146.7 grams respectively, molar ratio of methanol to oil is 42: 1, (in rapeseed oil) alkaline catalysts 0.05%, be that 0.05gKOH is dissolved in 3ml methyl alcohol, stirring heating reaches 240 ± 5 ℃, after pressure was 6.9MPa, 120 minutes afterreactions of clock reaction finished, and distill out unnecessary methyl alcohol, reacting liquor while hot is poured standing demix in the separating funnel into, lower floor is a coarse biodiesel, and the upper strata is the byproduct raw glycerine, and the pH value of levels is 6～7, and sampling respectively, analytical results is listed in the following table.

Levels reacting coarse product pH value is 6～7, so need not aftertreatment, has avoided common base catalysis method need add processes such as acid neutralization, washing, has prevented the generation of industrial sewage effectively.It is 96.3% that chromatogram detects methyl esters content, and bio-diesel yield reaches 99.7%; Glycerol content is 91.0%, and yield is up to 96.5%.

Embodiment 2

Change alkaline catalysts add-on in the foregoing description 1 into 0.1%, other condition is identical, and test-results is listed in the table.Upper strata byproduct of reaction raw glycerine pH value is 7～8, and following reaction product layer coarse biodiesel pH value is 6～7, need not aftertreatment.It is 99.1% that chromatogram detects methyl esters content, and bio-diesel yield is up to 99.7%.

Embodiment 3

The molar ratio of methanol to oil of the foregoing description 1 is reduced to 21: 1, and other condition is identical, and test-results is listed in the table.Levels reacting coarse product pH value is 6～7, still need not aftertreatment.It is 95.1% that chromatogram detects methyl esters content, and bio-diesel yield is up to 97.3%.

Embodiment 4

Change alkaline catalysts in the foregoing description 1 into NaOH, other condition is identical with embodiment 1, and test-results is listed in the table.Levels reacting coarse product pH value is 6～7, still need not aftertreatment.It is 98.1% that chromatogram detects methyl esters content, and bio-diesel yield is up to 98.3%.

Embodiment 5 is a comparative experimental example 1

Do not add base catalysis in the foregoing description 1, other condition is identical with embodiment 1, and test-results is listed in the table.The yield of chromatogram detection of biological diesel oil is 46.1%, and the yield of glycerine is 16.5%.Obviously do not have little base catalysis, just prepare biofuel under the methanol critical condition, the yield of methyl esters is very low.

Embodiment 6 is a comparative experimental example 2

Under condition of normal pressure, temperature of reaction is 60 ℃, and other condition is identical with embodiment 2, and test-results is listed in the table.The yield of chromatogram detection of biological diesel oil is 0%.Obviously in the little base catalysis of normal pressure, not to prepare biofuel under the methanol critical condition, transesterification reaction takes place hardly.

Embodiment 7 is a comparative experimental example 3

Conventional base catalysis legal system is equipped with biofuel, and test-results is listed in the table.

Watch test condition and result

Instance number	Temperature of reaction ℃	Reaction pressure MPa	The alcohol oil rate mole	Alkali add-on %	Bio-diesel yield %	Glycerine yield %	Reacting liquid pH value
Instance number	Temperature of reaction ℃	Reaction pressure MPa	The alcohol oil rate mole	Alkali add-on %	Bio-diesel yield %	Glycerine yield %	Reacting liquid pH value	One	245	6.9	42∶1	0.05	99.7	96.5	6～7
Two	245	6.9	42∶1	0.1	99.7	Do not survey	7～8	One	245	6.9	42∶1	0.05	99.7	96.5	6～7
Two	245	6.9	42∶1	0.1	99.7	Do not survey	7～8	Three	245	6.1	21∶1	0.05	97.3	Do not survey	6～7
Four	245	6.9	42∶1	0.05	98.3	Do not survey	6～7	Three	245	6.1	21∶1	0.05	97.3	Do not survey	6～7
Four	245	6.9	42∶1	0.05	98.3	Do not survey	6～7	Five	245	6.9	42∶1	0	46.1	16.5	6
Six	60	Normal pressure	42∶1	0.1	0	Do not survey	7～8	Five	245	6.9	42∶1	0	46.1	16.5	6
Six	60	Normal pressure	42∶1	0.1	0	Do not survey	7～8	Seven	60	Normal pressure	42∶1	1	91.2	Do not survey	9～10

Claims

1. the method for preparing biological diesel oil by methanol critical low alkali process, it is characterized in that taking little or low amount alkaline catalysts is that alkali metal hydroxide is dissolved in 2～3ml methyl alcohol, add-on 0.1～0.05%, 240 ± 5 ℃ of temperature of reaction, pressure are 6.9～7.0Mpa, then at methyl alcohol: the vegetables oil mol ratio is under 42～21: 1 the condition, the little alkaline solution that adds above-mentioned preparation, transesterification reaction in the autoclave pressure that band stirs, steam unreacted methanol, quiescent settling then, two-layer about dividing, promptly lower floor is a coarse biodiesel, and the upper strata is a raw glycerine.

2, the method for preparing biological diesel oil by methanol critical low alkali process according to claim 1 is characterized in that described alkali metal hydroxide is NaOH, KOH, sodium methylate.

3, the method for preparing biological diesel oil by methanol critical low alkali process according to claim 1 is characterized in that the described transesterification reaction time is: when reacting liquid temperature arrives 240 ± 5 ℃, pick up counting, reacted 100～120 minutes.