Aqueous Extraction Of Yellow Horn(Xanthoceras Sorbifolia Bunge.) Seed Oil And Methyl Esterification Process By Using Silica Supported Heteropolyacids

This research has studied on the extraction process for seed oil from yellow horn, the fatty acid composition and the main physical and chemical properties has been determined. Phosphotungstic acid immobilized on silica gel was prepared by impregnation as a new catalyst. The methyl esterification process has been established and optimized, the specific contents are as follows:1. The optimization of extraction for seed oil from yellow hornAcidic pH based microwave-assisted aqueous extraction for yellow horn seed oil was established. The mechanism of the acidic pH in the extraction process had been illustrated. The effects of the parameters, such as extraction temperature, liquid to solid ratio, extraction time, on the extraction yield were analyzed by central composite design and response surface methodology. The selected operating parameters were:pH5, extraction time52min, liquid solid ratio5.2:1, extraction temperature70℃, microwave power500W and stirring rate300rpm, and the oil extraction yield reached48.3%under this condition.2. The determination of the oil chemical composition and physicochemical propertiesThe physicochemical properties of yellow horn seed oil were determined as follows:acid value0.47mg KOH/g, iodine value117.79g/100g, peroxide value0.79mmol/kg. The oil chemical composition was analyzed by GC-MS, included palmitic acid, stearic acid, oleic acid and linoleic acid, which accounted for96.8%of the total weight.3. Preparation of a heterogeneous acidic solid catalystPhosphotungstic acid immobilized on silica gel was prepared by impregnation as a new catalyst. Its chemical structure was analyzed by FT-IR, which indicated the acidity was not affected by immobilized. The stability and properties of catalyst were investigated by recycling and reuse experiments. As a result, the using frequency of the catalyst was more than5times, which still remained a good catalytic activity.4. The optimization of methyl esterification processThe biodiesel preparation from yellow horn seed oil catalyzed by phosphotungstic acid immobilized on silica gel was established successfully. The effects of different parameters on conversion yield were investigated by single factor experiments. The optimal reaction conditions were:phosphotungstic acid loading amount30wt.%, catalyst dosage5wt.%, methanol to oil molar ratio9:1, reaction temperature60℃, reaction time60min, stirring rate300rpm, and the maximum conversion yield obtained was96.0%. The physical and chemical indicators of crude methyl ester product from yellow horn seed oil was analyzed as follows: flash point165℃, kinematic viscosity at40℃4.4mm2/s, cetane number56.1, sulfate ash content0.002%, acid value0.06mg KOH/g, and carbon residue0.03%. These are up to ASTM D6751and EN14214biodiesel standards.