| Energy is the base for the progress of human society. With the depletion of fossil resources such as petroleum, coal and natural gas, it is very urgent to seek alternative sources worldwide. The second generation of bio-fuels prepared from the catalytic deoxygenation of oil mainly contained alkanes ranging from octane to dococane. It has low oxygen content and high heating value, which can be mixed with vehicle fuels at any ratio and used as aviation fuels, making it a hotspot in the biomass research field. Currently, the main approach to produce the second generation of biofuels from oil is hydrodeoxygenation of vegetable oil, which has the disadvantages of high feedstock price and hydrogen cost. Therefore, more attention has been attracted to decarboxylation of oil, which is a promising technology to treat low-grade oil with less consumed hydrogen and less cost.This thesis employed fatty acids and fatty acid esters as the model compounds. The catalytic decarboxylation of these model compounds to alkane without hydrogen was studied, including metal catalyst preparation, catalyst activity evaluation, reaction kinetics, conditions optimization, etc. This thesis aimed at preparing efficient, inexpensive and reliable catalyst for the decarboxylation, revealing the regularity of reaction, demonstrating the mechanism of catalytic decarboxylation, and establishing a new approach for the preparation of long chain alkane, that will facilitate the industrialization process of efficient and low-cost preparation of the second generation biofuels.Firstly, five different Pt/C catalysts were prepared. The catalytic activities of catalysts for stearic acid decarboxylation were evaluated in high temperature water (HTW). The effects of reaction time and catalyst loading on the decarboxylation of stearic acid over two catalysts with high activity (Pt/C-H2O2-EG-24h and Pt/C-H2O2-HCHO-2h) were investigated. The results show that the carbon carrier after H2O2oxidation has larger specific surface area and mesopore volume than that after HNO3oxidation. Compared to HCHO, the reductant-glycol favors the dispersion of Pt particles on activation carbon. Reduction time has certain influence on the catalytic activity of catalyst.Secondly, the catalytic decarboxylation of fatty acid esters over commercial Pt/C was studied. The catalytic activity of commercial Pt/C on stearate decarboxylation under phenylacetonitrile, dodecane, cyclohexane, water, methanol and solvent-free were evaluated. The hydrothermal decarboxylation behaviors of different fatty acid esters over Pt/C were investigated. Then, Pt/C was used for the hydrothermal decarboxylation of micro-algae oil. The results show that Pt/C had synergistic catalysis effect with HTW. In hydrothermal condition, ester is firstly hydrolyzed to fatty acid, and then decarboxylated to alkane. Pt/C has a good effect on the hydrothermal deoxygenation of microalgae oil.Thirdly, Pt supported on carbon nanotubes (Pt/MWCNTs) was prepared. The kinetics of catalytic decarboxylation of stearic acid in HTW were studied. The structure information of catalyst was obtained by a series of characterizations of fresh and used catalyst. The effects of carbon number on the decarboxylation of saturated fatty acids were investigated. The results show that decarboxylation of stearic acid over Pt/MWCNTs shows high selectivity of97%. The decarboxylation is a pseudo-first-order reaction and the apparent activation energy is114kJ·mol-1. Corresponding alkane is produced by the decarboxylation of C12-22fatty acid over Pt/MWCNTs, and the selectivity varied with the length of carbon chain.Lastly, stearic acid was selected as model compound. The catalytic performances of Ni, Cu, Mg catalysts on stearic acid decarboxylation without solvent were evaluated. The effects of different supports, metal types, metal valences, solvents and metal loadings on the catalyst activity were initially investigated. The results show that Ni has higher catalytic activity on decarboxylation than Cu, Mg. Compared to the hydrothermal condition, Ni/C exhibits higher catalytic activity under solvent-free condition. |
PDF Full Text Request