| As Being a new type of slight low poisonouspoison or non-toxic, environmentally friendly benign and high boiling point solvent, dihydric alcohol carboxylic acid ester is widely used in coating, medicine, tobacco, food, plastics and rubber industryies and so on. The optimization of producing process and developing a series of dihydric alcohol carboxylic acid esters for purpose of large-scale preparation and extending their applications will bring using production methods and enlarging its range of application to extend the industrial chain will bring great economic and social benefits.This thesis focused on the preparation of dihydric alcohol carboxylic acid esters from Direct esterification method is used to synthesize the series of dihydric alcohol carboxylic acid ester products with small molecule fatty acids of small molecule such as (acetic acid and, propionic acid and the ethylene glycol or/propylene glycol) and diol. And the producing process was optimized as well. The final products was determined as raw materials. The series of in this paper, we use Ethylene glycol or propylene glycol with small molecules of fatty acids such as acetic acid and propionic acid as raw materials to give series of dihydric alcohol carboxylic acid ester products by esterification directly. Pproducts consist of are ethylene glycol diacetate (EGDA), propylene glycol diacetate (PGDA) and ethylene glycol dipropionate (EGDP) respectively. We characterized the various series of products are characterized by gas chromatography, fourierfourier transform infrared and nuclear magnetic resonance respectively.Based on the chosenselection of Catalyst, azeotropic dehydration agent, and for purpose of an optimum reaction condition, orthogonal method was employed based on single-factor. The results indicated that the optimal reaction condition is:ratio of propionic acid to ethanediol,3.0:1, toluene,10%(V), zinc chloride,1.0%and reaction time,5.0h, yielding the corresponding product with up to94.2%yield, of which, the yield of diester is up to95.31%, and all esters were obtained in up to99.83%yield. we study the influence of n(acetic acid): n(propylene glycol) mole ratio, the dosage of toluene, the reaction time and catalyst dosage to synthesis of propylene glycol acetate(PGDA) production rate by single factor experiment and we get the optimal process parameters by orthogonal optimization: n(acetic acid):n(propylene glycol) =3.0:1, reaction time of5.0h, zinc chloride dosage of1.0%, toluene dosage of10%, PGDA yield of95.31.%, total ester content of99.83%, product yield of94.2%.The effect on the yield of ethylene glycol dipropionate was investigated by different ratios of the applied substrates. An optimum reaction condition was obtained with orthogonal method based on single-factor test. The results indicated that the optimal reaction condition is:ratio of propionic acid to ethanediol,2.5:1, p-toluene sulfonic acid and toluene,1.0%and10%of the total mass, respectively, reaction time,3.0h, yielding the corresponding product ethylene glycol dipropionate with yield of up to87.4%. Meanwhile, a further investigation for comparing the solubility with commonly applied orgainic solvents was also made, and EGDA, PGDA, EGDP proved to be with excellent capability for dissolving acrylic resin and epoxy resin, which is environmental friendly and safe to use. We study the influence of n (propionic acid): n(ethylene glycol), mole ratio, the dosage of p-toluene sulfonic acid, toluene dosage and reaction time and so on to ethylene glycol dipropionate (EGDP) esterification rate by single factor experiment, and on the basis of single factor, we get the better process parameters by orthogonal optimization:n (acrylic acid):n (ethylene glycol)=2.5:1, p-toluene sulfonic acid and toluene account for1.0%,10%of the total quality of materials respectively, reaction time of3.0h, EGDP yield of87.4%. We further study the solubility propertyb of EGDA, PGDA and EGDP series of dihydric alcohol carboxylic acid ester respectively. The results show that the three kinds of solvent’s solubility property have excellent solubility property for acrylic resin, epoxy resin and also environmental protection and safety relative.Based on the existing industrial production preparation process of ethylene acetate (EGDA), a further optimization was made. It was indicated that one fifth of the previous loading of catalyst could maintain full of its original efficiency in catalyzing by consequence addition in3times. Reation condition is:ratio of ethyl acid and ethandiol,2.2:1(mol), and through process optimization, it is concluded that the original p-toluene sulfonic acid catalyst will ensure its efficient catalytic ability based on a continuous three times adding relative to its usage of20%copper chloride; n(acetic acid):n(ethylene glycol)=2.2:l,reflux ratio of,2.0:1, and slag amount is reduced by30.5%by using the mass fraction of15%sodium carbonate solution alkaline cleaning production statistics in the refining process optimization.. Results indicated that:the waste was reduced by30.5%,, single reaction time for one cycle is shortened reduced by13.1%, and the final production producing cost is reduced up to by up to6.28%%. An obvious promotion in final yield and quality was found. Eventually, it brings us a considerable economic benefit. |
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