| Fat is an important renewable resource and important raw material of preparing biodiesel by transesterification. However, there are many defects in the production costs and properties, and the methyl ester of fatsty acid bio-diesel encountered some difficulties in application. Therefore, this study prepared renewable liquid fuel which with high heat value and better fluidity at a low temperature by catalytic cracking of fats. Process of catalytic cracking and the acid control mechanism were studied, as well as the preparation of highly efficient heterogeneous solid acid catalyst. The main contents and results of this research are summarized as follows:1. Catalytic cracking mechanism, process and properties of products had been studied. We used TG-calorimetry method to study the mechanism of catalytic cracking process and proposed a new process of basic catalyst cracking. With three catalytic cracking reactor, including batch reactor, the rotating cone reactor and catalytic distillation reactor, we studied the catalytic cracking process and determined the catalytic distillation reaction was the suitable method of preparing liquid fuels. Best conditions were distillation column temperature of 320 350℃, cracking temperature of 450 500℃, the feed rate of 35 g / h, using Na2CO3 as the catalyst. Fuel properties of the product as follows: density of 825 kg/m3, viscosity of 4.0 mm2 / s, heat value of 42 MJ / kg, freezing point of -9℃and the cold filter plugging point of -4℃. Comparing to biodiesel, both the low temperature fluidity and heat value of product improved significantly. Then catalytic cracking of palm oil, Curcas oil, S.wilsoniana Sojak oil, tung oil was studied in last process conditions. The results showed that the catalyst method has good adaptability of raw materials. GC-MS confirmed compositions of products were main alkanes and alkenes with the carbon chain of less than C24, and a small amount of aldehyde, carboxylic acid compounds.2. Catalytic cracking solid acid and its structure had been studied. The results showed that the solid acid with mesoporous ZrO2 carrier (M-ZrO2) prepared by hydrothermal synthesis and S2O82- acidic groups had better catalytic activity. Better preparation conditions of preparing catalyst S2O82-/M-ZrO2 are as followed: S2O82- salt solution concentration of 2.5 an be 51.4%. mol/L, with calcination temperature of 550℃and calcination time of 3 h. The structure and composition of mesoporous ZrO2 and S2O82-/M-ZrO2 were studied by XRD, TG-DSC analysis, N2 adsorption and desorption, SEM analysis. The results were the mesoporous ZrO2 had the surface area of 398.0 m2/g and average pore diameter of 5.67 nm, showing in small amorphous grains. The S2O82-/M-ZrO2 had smaller surface area and pore volume than mesoporous ZrO2, which with tetragonal phase, surface irregularities and had loose hole of honeycomb structure. Acetic acid and ethanol esterification reaction as a model reaction, catalyzed by S2O82-/M-ZrO2, esterification rate of which c3. Using S2O82-/M-ZrO2 solid acid catalysts with good esterification effect studied the acid value of cracking products control methods. Optimal conditions were using 4 % S2O82-/M-ZrO2 solid acid catalyst and m (methanol): m (pyrolysis oil) = 0.3, under which the acid value dropped to 6 mgKOH/g, esterification rate reached 94.4 %, and esterification rate reduced to 84.8 % when repeat using the catalyst for three times. FT-IR and GC-MS analysis showed that the carboxylic acids have been methylated and been converted into the corresponding fatsty acid methyl ester. The fuel properties of esterification product were as followed: calorific value increased to 42 kJ/g, acid value from the 59 mgKOH/g decreased to 6mgKOH/g, viscosity was within the criteria of 0# diesel, and condensation point and cold filter plugging point are -10℃and -8℃, which were better than biodiesel and better low temperature fluidity. By alkaline treatment, the acid value of esterification product can be further decreased to 0.4 mgKOH/g.
|
PDF Full Text Request