Investigation Of New Catalyst For Biomass Tar Catalytic Reforming

As an environment-friendly and renewable resource, biomass is only one of the promising substitutions of fossil fuels at present. The gasification is one of the effective technologies for its conversion. However, the gasification process is inevitably accompanied by the formation of tar. The condensable compounds that present in tar not only cause conglomeration and sediment in the gasification equipment and gas transporting line, but also threat the environment and health of man. Therefore, the tar affects the extensive utilization of the technology of the biomass gasification.A review of current researches and development of biomass tar destruction is given in this thesis, from which the conclusion can be drew that the catalytic steam reforming of tar is the most effective method to suppress the problem. The choice of catalysts is the important factor of the catalytic reforming of biomass tar, and the reaction activity and life span are the chief performance factors of catalyst. From economical and technical considerations, nickel-containing catalyst appears to be the most appropriate choice.In the aim of the choice for the new catalysts possessing higher reaction activity and better function to prevent coking, a series of experiments were carried out, from which the useful and systematical data were studied. At first, the performance of two series of synthesized nickel-containing olivine catalysts was investigated using toluene and benzene as model biomass tar. The effects of the content of Nickel and Cerium impregnated olivine and the reaction condition on toluene catalytic reforming were investigated. The results showed: for 1 % Ce-3 % Ni/Olivine catalyst, the conversion efficiency of toluene is 88.2% at the temperature of 800℃and the steam to carbon (s/c) of 5. And then on the basis, the effects of the addition of the basic promoter Mg and the different impregnating order of promoter were examined. The results showed that the catalysts of adding the basic promoter possessed better function to prevent coking. Impregnating order of promoter affected the reaction activity seriously. The catalyst of sequentially impregnating Mg, Ce, Ni exhibited higher catalytic activity under the same condition. For 1%Mg-1%Ce-3%Ni/Olivine catalyst, the conversion efficiencies of toluene and benzene were 93.8% and 76.9% respectively at the temperature of 800°C and the steam to carbon (s/c) of 3.5.In order to eliminate the formation of the tar derived from the gasification of biomass, a set of apparatus that used for the gasification of biomass and the corresponding catalytic reforming of tar was set up. The further tests for synthesized catalysts were conducted in this apparatus. The effects of the reaction condition on the composition of gas and the content of biomass tar were determined. At the same time, the performance of synthesized 1%Ce-3%Ni/Olivine catalyst was researched using the producer gas derived from biomass gasification, and changes in gas composition and the tar content by the addition of catalyst and the steam were also analyzed in this study. The catalyst proved effective and the conversion efficiency of heavy tars was 90% in the presence of steam and at the temperature of 750℃, and hydrogen yield also increased 6～7%...