Catalytic pyrolysis of three different agricultural and forestry wastes (pinewood, peanut shell, rice straw) was performed in a fixed-bed reactor heated slowly under a stream of purging argon in the temperature range from 300 °C to 700 °C using K2CO3 as the catalyst. The aim of this study is to investigate the gaseous, liquid, and solid products derived from three different biomasses, and to ascertain the effects of K2CO3 on the pyrolysis behaviours. The products' yields correlated with the composition of the biomasses and the addition of catalyst in the biomasses. The addition of K2CO3 described a strong catalysis in all three phases of the products: The liquid yield decreased obviously in contrast to the increase in gas yield. The liquid yields of pinewood and peanut shell demonstrated a remarkable decrease, while that of rice straw demonstrated the least decrease owing to a significant difference between the fibre composition of rice straw and those of the other two biomasses. This catalytic pyrolysis procedure was observed to produce low yields of liquid that contained high proportions of ketones and phenols, with minor acids, aldehydes, and furans. Among the three, the phenols of rice straw indicated the most obvious increase, while guaiacols decreased significantly, indicating that K2CO3 facilitated the secondary decomposition of guaiacols. Generally, for K2CO3 catalyst, the order of catalytic effect was pinewood > peanut shell > rice straw.
Keywords: Biomass; agricultural wastes; catalytic pyrolysis; fixed-bed reactor; potassium carbonate; thermogravimetry.