| Since the implementation of the plastic restriction policy in the world,many kinds of non-toxic and environment-friendly plasticizers which mainly derived from plant oils and fats(biomass resources)came into being.Epoxidized soybean oil(ESBO),as plasticizer and stabilizer of PVC material,was economical and environmental friendly,and effectively reduced humans' concern about the problems of resource and environment.In addition,in China,as a representative of high unsaturation oil,soybean oil has a large production,low cost and wide source,which provides a rich material base for the development of ESBO industrialization.However,due to the serious corrosion of the equipment,the difficulty of the treatment of "three wastes" and the low catalytic efficiency of the traditional catalyst,it is very urgent to develop a clean and efficient catalyst to improve the utilization of the epoxide-tion of soybean oil.In this paper,the one-pot epoxidation of refined soybean purchased from the market has conducted when deep eutectic solvents(DESs)were used as a catalyst.1H NMR spectrum method was used to quantitatively analyze the conversion rate of double bonds and the yield of epoxidation,effectively replacing the tedious,complicated gas chromatography-mass spectrometry(GC-MS)and the national standard titration method according to the change of characteristic functional groups and finally the excellent results have been obtained.Three kinds of DESs as catalysts were prepared with different hydrogen bond donor(HBD),including oxalic acid dihydrate(OA),malonic acid(MA),citric acid monohydrate(CA),and choline chloride(Ch Cl)in molar ratio of 1:1.In the fixed proportion of raw oil,formic acid(88wt %)and hydrogen peroxide(30wt %),the epoxidation reaction occurred.The structure and composition of the raw soybean oil and obtained products were analyzed and compared by nuclear magnetic hydrogen spectrum.The results showed that the reaction in choline chloride-oxalic acid dihydrate(Ch Cl-OA)system was carried out at 50 ? for 8 h,possessing the conversion rate 88.80% of double bond,the selectivity of 93.86%,which exceeded that of Ch Cl-MA(90.87%,10 h)and Ch Cl-CA(83.52%,8 h).Compared with other various catalysts under the same conditions,Ch Cl-OA has better catalytic performance.The results of characterization illustrated that characteristic groups from product were consistent with the target product with the higher conversion rate of the unsaturated double bond and the lower chance of the side reaction.The mechanism of the catalytic epoxidation further was accomplished.It was found that hydroxyl groups in the carboxylic acid and the anion in quaternary ammonium salts were combined by the hydrogen bonding,forming a double functional epoxidation catalyst,DES,to promote the process of epoxidation.Through the analysis of the structure and properties of different quaternary ammonium salt(hydrogen bond receptor,HBD)-oxalic acid dihydrate,a single factor experiment was carried out to optimize the exploration process by using DES synthesized by benzyl three ethyl ammonium chloride(TEBA),three butyl methylation ammonium chloride(MTBAC),four ethyl ammonium chloride(TEAC),choline chloride(Ch Cl)and oxalic acid dihydrate.The main influence factors concluded the type of HBD,reaction temperature,reaction time,the amount of hydrogen peroxide,formic acid and catalyst.Under the optimum conditions,the epoxy value of the product was 6.85%,the acid value was 0.45 mg/g(KOH),the iodine value was 4.33 g I2/100 g,the water content is 0.1%,and the standard of the national epoxy soybean oil plasticizer has been reached.The epoxidized soybean oil(ESBO)has slight color and high quality which was mixed with the traditional dioctyl phthalate(DOP)in a certain proportion as a plasticizer,then they were added to the polyvinyl chloride(PVC)resin.The standard test strips were obtained by mixing and injection molding after the proper amount of stabilizer was added into.The testing methods of physical(surface hardness,extraction),mechanical(tensile test),thermal analysis(thermal aging,DSC)were used to comfirm the plasticity of different samples.The addition of epoxy soybean oil decreased the glass transition temperature of the material,prolonged the aging time and improved the corresponding thermal stability in comparison with the samples under the addition of DOP alone.In addition,the test results of hardness and tensile strength showed that the toughness of PVC samples enhanced obviously,and the mixing use also reduced the loss of volatilization in liquid. |
PDF Full Text Request