DEVELOPMENT OF CARBON-BASED CATALYST SYSTEM FOR CATALYTIC FAST PYROLYSIS OF LIGNOCELLULOSIC BIOMASS UNDER MICROWAVE ENERGY

The goal of the work is to provide a “green” and economical process of producing activated carbon from biomass with textural properties optimized for microwave-assisted catalytic fast pyrolysis and related applications. Douglas fir wood was successfully activated with phosphoric acid and carbonized via microwave heating. Although increasing phosphoric acid concentration during activation of biomass could result in high surface area, it was found that carbonization time was relatively compromised. Optimization that emphasizes economic consideration revealed that a 56.50 % wt. phosphoric acid concentration carbonized under 650 W microwave in around 30 minutes could give mostly mesoporous carbon with estimated surface are of 826.38 m2/g. Further, derived mesoporous activated carbon was effective susceptor and catalyst for in-situ microwave pyrolysis of softwood biomass. Average heating of biomass under microwave was improved significantly from 33 °C/min to 115 °C/min with increasing activated carbon fraction on feedstock mix. Notably, activated carbon favors highly furanic bio-oil product mainly comprising of furfural and methyl furfural from the biomass pyrolysis under microwave energy. Numerical optimization suggests that furfural selectivity could be as high as 70% of the total GC-MS peak area with corresponding concentration of 22.04 mg/mg of bio-oil can be obtained with activated carbon to biomass ratio of 2.5 and pyrolyzed at 650 W microwave energy. It was further noted that activated carbon tends to favor char formation from lignin-based pyrolytic products by promoting cross-linking and repolymerization during the liquid intermediate phase of the pyrolysis. This was further proved by activated carbon catalyzed ex-situ runs, which led high mono-phenolic bio-oil products. These phenolics are either from dehydration of guaiacols or re-arrangement from furanic intermediates which are upgraded in their gas phase. Kinetic studies on the thermal conversion of Douglas fir within the activated carbon bed show positive impacts of the activated carbon because the activation energy estimated by isoconversional method was lower when pyrolyzed with incorporation of AC than without it

Renewable High-Purity Mono-Phenol Production from Catalytic Microwave-Induced Pyrolysis of Cellulose over Biomass-Derived Activated Carbon Catalyst

The activated carbons (ACs) enriched in P-containing functional groups were obtained through one-pot microwave-induced pyrolysis from corn stover activated with phosphoric acid and were further tested as the catalyst for selective monophenol production from cellulose pyrolysis for the first time. Maximum AC yield (44.3 wt %) was obtained with an acid to biomass ratio of 0.85. Increasing phosphoric acid to corn stover ratios could enhance the porosity and peak intensities of P-containing functional groups in obtained ACs. Attained ACs had an excellent catalytic performance in phenol production with the highest selectivity of phenol (99.02 % based on peak area) in the obtained organic compounds at the catalytic temperature of 450 °C. The catalytic performance of ACs remained highly selective for phenol after using two times. The experimental results indicated that P-containing groups such as −O–P, OP, and −O–P–O– were the active reaction sites and more mespores promoted phenol production. The phenol can be generated from reforming of levoglucosenone and furfural over AC catalysts. The present work provides an efficient route to produce high selective monophenol from cellulose pyrolysis by using activated carbons as the catalyst, which further advanced the utilization of biomass to produce high-value chemicals