Catalytic Pyrolysis of Lignocellulosic Biomass: The Influence of the Catalyst Regeneration Sequence on the Composition of Upgraded Pyrolysis Oils over a H-ZSM-5/Al-MCM-41 Catalyst Mixture

Abstract

Catalyst regeneration is economically attractive, and it saves resources. Thus, it is important to determine the influence of catalyst regeneration on the chemical composition of upgraded oil. The catalyst was regenerated several times, and the regenerated catalyst was reloaded in the reactor to proceed with the next run. The composition of the derived upgraded pyrolysis oils in relation to catalyst regeneration was determined. The results revealed that the catalyst cracking abilities decreased with an increased number of reaction cycles. The opposite trends of the organic fraction and water yields indicated that the deoxygenation process occurred via H2O production. A decrease in the CO and CO2 yields revealed that the deoxygenation in catalytic pyrolysis with a catalyst mixture occurred via decarbonylation, decarboxylation, and dehydration mechanisms. The chemical formula of bio-oil changed from CH0.17O0.91 for a noncatalytic experiment to CH0.14O0.66 for a catalytic pyrolysis experiment after five reaction cycles, which indicated that the oxygen in the bio-oil decreased at the expense of hydrogen. The high heating value (HHV) of bio-oils decreased as the number of reaction cycles increased, albeit the minimum value of 22.41 wt % in the 6th reaction cycle was still higher than the value for the noncatalytic experiment. Compared to the HHVs of diesel fuel and gasoline petrol, the values of the produced bio-oil with catalyst mixtures were still low. The catalyst regained 94% of the surface area for the fresh catalyst, which indicated that the regeneration procedure was effective.