Processing of Lignocellulosic Waste Biomass via Fine Cr2O3-Catalyzed Pyrolysis in a Sealed Pressure Reactor

The aim of the work is to present a technologically feasible method for processing waste biomass into synthesis gas for further use, namely for the synthesis of bio-methanol, which is considered an important renewable fuel. Walnut shells were tested as lignocellulosic waste. Samples with an operating particle size (0.5–3 mm) were pyrolyzed under well-defined conditions in a sealed pressure reactor, using chromium (III) oxide particles and fine particles as a catalyst. The effect of particle size on the yield and composition of resulting synthesis gas and biochar was tested. It was found that slow, catalyzed pressure pyrolysis at a final temperature of 400 °C provides synthesis gas with a H2/CO ratio of up to 0.9 or up to 1.8 and biochar (35–39 wt.%) useful as biofuel. These products were analyzed and their use described. The residual product was greywater (25–35 wt.%). Overall, under energy-saving conditions (slow pyrolysis, final temperature of 400 °C), pressure and catalyzed pyrolysis of biomass provide usable products and acceptable residuum.