Modifications in the Thermicity of the Pyrolysis Reactions of ZnCl2-Loaded Wood

The influence of the loaded zinc chloride content (0-11 wt %, dry sample basis) on the pyrolysis of beechwood particles packed in a bench-scale bed was studied. Given an external heating temperature of 655 K, the temporal profiles of the thermal field showed maximum values progressively increasing from 683 to 790 K as the catalyst content was increased from 0 to about 5 wt %. Based on cumulative char and water yields increasing from about 51 to 70 wt % and yields of condensable organics decreasing from about 35 to 15 wt %, the enhancement in the global exothermicity of the conversion process can be attributed to the successive predominance of dehydration with cross-linking reactions over depolymerization reactions. The exothermic effects were found to be qualitatively similar to but quantitatively lower than those associated with a sulfuric acid treatment. For higher acid contents and both additives, the noncatalytic effects associated with their loading were also found to contribute significantly to the characteristics of the thermal field. Specifically, for zinc chloride, the successively higher effective thermal conductivities of the bed caused a progressive reduction in the spatial gradients and maximum temperatures.