A kind of production method of biofuelTechnical field
The present invention relates to a kind of production method of biofuel, relate in particular to a kind of production method of low acid number biofuel.
Background technology
Fatty acid triglyceride, particularly animal and plant fat and oil, carries out with lower molecular weight monohydroxy-alcohol the formicester that transesterification reaction obtains, has similar character to the diesel oil obtained from petroleum fractions, can use as fuel, generally the fuel obtained in this way is called biofuel.
The biofuel of being produced by the transesterification reaction of grease is had the following advantages: 1) have excellent environmental protection characteristic.Biofuel sulphur content is low, also not containing the aromatic hydrocarbon to environment.2) have good engine cold-starting performance, time additive-free, condensation point reaches-20 DEG C.3) there is good lubricity, the wear rate of oil injection pump, engine cylinder-body and connecting rod can be reduced, extend its work-ing life.4) have good safety performance, its flash-point is high, does not belong to hazardous substance.5) have good fuel performance, its cetane value is high, and combustionproperty is better than ordinary diesel oil.6) there is recyclability.Biofuel is as a kind of renewable energy source, and its resource can not be exhausted.
CN1408701A discloses a kind of method and apparatus preparing fatty acid ester.Under supercritical state and catalyzer existent condition, use the reactor of this invention, prepare fatty acid ester.Wherein reactor is returned in the reaction mixture recirculation containing unreacted reactant and/or intermediate product.The preferred temperature of the method 240 DEG C ~ 400 DEG C, preferred temperature is 245 DEG C ~ 350 DEG C, and preferred reaction pressure is 0.5MPa ~ 25MPa, and preferred reaction pressure is 2MPa ~ 22MPa, particularly preferably 8MPa ~ 20MPa.
CN1408701A also discloses and a kind ofly prepares the method for fatty acid ester and the fuel of fatty acid esters.This fatty acid ester is in the absence of catalyst, and one of grease and alcohol are under the condition of supercritical state, prepared by grease and alcohol reaction.The method preferable reaction temperature is no more than 400 DEG C, and preferred reaction pressure is 0.4MPa ~ 25.0MPa.
CN1230945A discloses a kind of from fatty acid triglyceride, especially animal or plant fat and oil, with the method for a kind of lower molecular weight monohydroxy-alcohol by transesterification production fatty acid ester under homogeneous phase or different-phase catalyst exist.The fatty acid ester generated according to the method is extracted from reaction mixture by a kind of extraction agent, and the fatty acid ester purity obtained like this is higher.There is reduced temperature about 0.7 as the most handy one of extraction agent 20 DEG C time, be preferably equal to or greater than the low-pressure gas of 0.7.Preferred extraction agent is carbonic acid gas, propane, butane, dme, ethyl acetate or their mixture.
Due to alcohol and animal and plant grease mutual solubility poor, reaction system is two-phase, and transesterification reaction is only carried out at interface, and speed of reaction is low, and in order to improve transformation efficiency, CN1496398A discloses a kind of method being obtained fatty acid ester by alcoholysis from triacylglycerol ester.In order to accelerate ester-exchange reaction, a certain amount of at least one alkanol fatty acid ester is added in initial reaction phase, especially unitary chain triacontanol ester, preferred methyl esters, ethyl ester and/or ethyl ester, to in the fat having pending transesterify and/or oil, so that the reaction mixture generated thus is made up of single-phase.Thus make this process from just keep high reaction rate.
Japanese Patent (JP 2002-167356) also discloses a kind of preparation method of fatty acid ester, the method adopts a kind of volatile organic amine as catalyzer, fatty acid ester is prepared under the condition comparing mitigation, from technological angle, do not need separating catalyst, simply can refine out fatty acid ester, and avoid in traditional method also exist be separated glycerine mutually in the problem of catalyst residue.The optimum reaction condition of the method is, temperature of reaction 60 ~ 150 DEG C, and reaction pressure is 0.2 ~ 0.9MPa.
In the production method of above biofuel, owing to there being water to exist in reaction process, methyl esters can be hydrolyzed generation organic acid in presence of water, the acid number of biodiesel oil product is increased, can not meet the requirement of standard.At present, in production of biodiesel process, removing organic acid method has, 1) adopt alkaline aqueous solution, the organic acid in neutralized product, makes it generate good fortune thing, then carries out being separated, washes, drying obtains standard compliant biodiesel oil product.This method, product yield is low, is formed a large amount of saponified, needs recycling, produces a large amount of contaminated wastewater environment in production process simultaneously.2) adopt the method for hydrogenation, make organic acid become alcohol, to reduce the acid number of product, meet the requirement of standard.This method, energy consumption is large.Owing to needing hydrogen in production process, this method is made to have certain limitation.
In use, the acid number of biofuel is very large on engine working conditions impact for biofuel, and the biofuel that acid number is large can make carbon distribution in engine increase, and causes piston wear, makes nozzle coking, affect atomization and combustionproperty; The excessive emulsion that also can cause biofuel of acid number.Organic acid content in acid number large explanation product is high, and these organic acids in presence of water, will corroding metal.And organic acid relative molecular weight is less, it is acid larger, and corrosive power is also stronger.When there being water to exist, even the low molecular organic acids of trace, also can with metal function, generate be dissolved in the ferrous naphthenate of oils and carboxylic acid ferrous etc., make equipment corrosion; Generate metal soap, cause lubricating oil to accelerate rotten; Soap class is gathered in oil and forms settling simultaneously, destroys machine and normally runs.
Biofuel use in process, the acid number of biofuel is very large on engine working conditions impact, and the biofuel that acid number is large can make carbon distribution in engine increase, and causes piston wear, makes nozzle coking, affect atomization and combustionproperty; The excessive emulsion that also can cause biofuel of acid number.Organic acid content in acid number large explanation product is high, and these organic acids in presence of water, will corroding metal.And organic acid relative molecular weight is less, it is acid larger, and corrosive power is also stronger.When there being water to exist, even the low molecular organic acids of trace, also can with metal function, generate be dissolved in the ferrous naphthenate of oils and carboxylic acid ferrous etc., make equipment corrosion; Generate metal soap, cause lubricating oil to accelerate rotten; Soap class is gathered in oil and forms settling simultaneously, destroys machine and normally runs.
CN200810012202.2 discloses organic acid removal methods in a kind of biofuel, under anionite-exchange resin exists, 50 ~ 100 DEG C, under the condition of normal pressure, effectively remove organic acid in biofuel, obtain standard compliant biodiesel oil product.CN101993776 adopts the method production biofuel adding de-acidying agent.Aforesaid method all needs to add extra material, and cost is high, troublesome poeration.
Summary of the invention
For the deficiencies in the prior art, the invention provides a kind of preparation method of biofuel.The method can produce the biofuel of low acid number, has simple to operate, low cost and other advantages.
A preparation method for biofuel, comprises the steps:
(1) animal and vegetable oil containing fatty acid triglycercide or fat and the monohydroxy-alcohol with 1 ~ 4 carbon atom carry out esterification under the effect of organic alkali catalyst;
(2) esterification products of separating step (1), obtains having the monohydroxy-alcohol of 1 ~ 4 carbon atom, raw glycerine and the lipid acid monoester containing organic alkali catalyst;
(3) to step (2) be separated obtain add water containing in the lipid acid monoester of organic alkali catalyst and be uniformly mixed, add that the water yield is the lipid acid monoester quality containing organic alkali catalyst 1% ~ 20%, preferably 1% ~ 10%, most preferably 1% ~ 5%, mixing temperature is 25 DEG C ~ 100 DEG C, preferably 30 DEG C ~ 80 DEG C, most preferably 50 DEG C ~ 80 DEG C;
(4) in the material of step (3), step (2) isolated raw glycerine stratification after being uniformly mixed is added, obtain ester phase and glycerine phase, namely ester obtains the qualified biodiesel oil product of acid number through underpressure distillation, can obtain lipid acid and glycerine after glycerine processes mutually.
In the inventive method step (1), the described animal and vegetable oil containing fatty acid triglycercide comprises Oleum Gossypii semen, plam oil, rapeseed oil, soybean oil, peanut oil, tung oil, preferred Oleum Gossypii semen and plam oil.The described monohydroxy-alcohol with 1 ~ 4 carbon atom comprises methyl alcohol, ethanol, propyl alcohol, butanols, particular methanol, ethanol, more preferably methyl alcohol.Described organic alkali catalyst is the organic amine containing 1 ~ 10 carbon atom.Comprise methylamine, dimethylamine, Trimethylamine 99, allylamine, diallylamine, triallylamine, Isopropylamine, Diisopropylamine, ethamine, diethylamine, triethylamine, 2 ethyl hexylamine, propylamine, n-Butyl Amine 99, t-butylamine, sec-butylamine or monoethanolamine, preferred diethylamine.
In the inventive method step (2), the monohydroxy-alcohol with 1 ~ 4 carbon atom is obtained by the evaporation mode of routine, isolate the material after monohydroxy-alcohol and obtain raw glycerine and the lipid acid monoester containing organic alkali catalyst through stratification, described is 0.1 ~ 10% containing organic bases mass content in the lipid acid monoester of organic alkali catalyst, preferably 0.1 ~ 5%, most preferably 0.1 ~ 3%.
In the inventive method step (4), the amounts of glycerol added is 1% ~ 100% of step (2) isolated raw glycerine, preferably 5% ~ 100%, most preferably 10% ~ 100%, and being uniformly mixed temperature is 25 DEG C ~ 100 DEG C, preferably 30 DEG C ~ 80 DEG C, most preferably 50 DEG C ~ 80 DEG C.
The inventive method adds appropriate water in the esterification products isolating monohydroxy-alcohol, raw glycerine, be conducive to organic acid in esterification products and organic bases reacts, then raw glycerine is being added, the system of raw glycerine and water composition fully can extract the resultant of organic acid and organic bases, and then obtains the biofuel of low acid number.The preparation of biofuel combines with esterification products refinement treatment by the inventive method, only need add appropriate water, have cost low, advantage simple to operate.
Embodiment
further illustrate process of the present invention and effect below in conjunction with embodiment, but following examples do not form the restriction to the inventive method.
Embodiment 1
Oleum Gossypii semen 300g is added, methyl alcohol 130g, triethylamine 23g in autoclave, temperature of reaction 140 DEG C, take out after reaction 5h, steam remaining methyl alcohol, remaining product separation goes out raw glycerine 27g, ester phase acid number is 3.73mgKOH/g, ester mutually in add 4g water, add 10g raw glycerine after vibration, vibration shakes up, stratification, getting upper strata ester through underpressure distillation post analysis acid number is 0.21mgKOH/g.
Embodiment 2
Plam oil 300g is added, methyl alcohol 110g, triethylamine 36g in autoclave, temperature of reaction 100 DEG C, take out after reaction 5h, steam remaining methyl alcohol, remaining product separation goes out raw glycerine 29g, ester phase acid number is 1.09mgKOH/g, ester mutually in add 6g water, add 15g raw glycerine after vibration, vibration shakes up, stratification, getting upper strata ester through underpressure distillation post analysis acid number is 0.25mgKOH/g.
Embodiment 3
Plam oil 500g is added, methyl alcohol 133g, triethylamine 51g in autoclave, temperature of reaction 130 DEG C, take out after reaction 3h, steam remaining methyl alcohol, remaining product separation goes out raw glycerine 22.4g, ester phase acid number is 3.27mgKOH/g, ester mutually in add 5g water, add 20g raw glycerine after vibration, vibration shakes up, stratification, getting upper strata ester through underpressure distillation post analysis acid number is 0.34mgKOH/g.
Comparative example 1
Step 2 only isolates methyl alcohol, and all the other are with embodiment 1, and getting upper strata ester through underpressure distillation post analysis acid number is 0.72mgKOH/g.