Cracking Of Volatile Products From Pyrolysis Of Fir Sawdust Using Metals/char As Catalysts

The paper investigated the catalytic cracking of biomass pyrolysis vapors using fir sawdustas raw materials. A pyrolysis reactor was used, which consisted of two vertical fixed beds, thebottom one for biomas pyrolysis and the up one for catalytic cracking. In the cracking process,metals/char catalysts, such as Ni,Fe,K,Ca,Mg, were used in the pyrolysis and crackingprocess. In the process of pyrolysis and cracking, the gaseous products were real time detectedby gas chromatography, the liquid collected after cooling were analyzed by GC-MS, and thestructure of metal-based carbon were characterized by XRD.The results show that pyrolysis of fir wood produced a large amount of oxygenatedcompounds such as alcohol, aldehydes, ketones, acid and phenols. They could be catalyticallycracked into the hydrogen-rich gases. Especially, the Ni based char catalyst exhibited the bestperformance to catalytically convert tar into hydrogen,with the much less content of CO₂, COand CH₄. The pyrolysis and cracking of biomass in the presence of the Fe, K and Ca based charcatalyst also obtained the gas steam with the higher content of H₂, but produced the much morecontent of CO₂, CO and CH₄than that in the case of Ni based char catalyst. The Mg based charresulted in the very low content of H₂, CO and CH₄.The metal/char catalysts have a significant effect on the compound distribution in liquidpyrolytic products. Ni/char catalyst exihibited the excellent performace in catalysizing thecracking of light tar and heavy tar, leading the the marked decrease in CH₄content. K-carbonand Ca-carbon catalyst preferred to catalyze the cracking of heavy tar, producing more a cokeand water. Fe-carbon catalyst predominantly catalyzed the cracking of light tar. However,Mg/char catalyst has no significant catalysis in the tar cracking.In addition, the Ni metal was loaded at800°C charring of charcoal, which in the catalyticpyrolysis temperature of800oC have the best catalytic effect and the tar have largely crackedinto gas composition, but Ni/carbon have the short use life. By Ni and Fe preparation ofcomposite metal/carbon catalyst, research have shown that the catalytic effect has not beensignificantly improved; when Ni metal was loaded in the coconut shell activated carbon, and weresearch the catalytic pyrolysis temperature of800oC, the results show that it not only havevery good catalytic effect, but also has the long use life and the tar largely cracked into gascomposition.