Joan Wu

The effects of torrefaction on compositions of bio-oil and syngas from biomass pyrolysis by microwave heating.

Microwave pyrolysis of torrefied Douglas fir sawdust pellet was investigated to determine the effects of torrefaction on the biofuel production. Compared to the pyrolysis of raw biomass, the increased concentrations of phenols and sugars and reduced concentrations of guaiacols and furans were obtained from pyrolysis of torrefied biomass, indicating that torrefaction as a pretreatment favored the phenols and sugars production. Additionally, about 3.21-7.50 area% hydrocarbons and the reduced concentration of organic acids were obtained from pyrolysis of torrefied biomass. Torrefaction also altered the compositions of syngas by reducing CO2 and increasing H2 and CH4. The syngas was rich in H2, CH4, and CO implying that the syngas quality was significantly improved by torrefaction process.

Catalytic co-pyrolysis of lignocellulosic biomass with polymers: a critical review

The increasing demand for renewable chemicals and fuels requires the exploitation of alternative feedstock to replace petroleum-derived chemicals and fuels. Lignocellulosic biomass has been considered as the most promising feedstock for the production of sustainable biofuels. Catalytic fast pyrolysis (CFP) is more amenable to directly converting biomass into high quality biofuel. However, even in the presence of a highly efficient catalyst, the CFP of biomass can solely manufacture a low yield of aromatic hydrocarbon but a high formation of coke. The addition of a hydrogen-rich co-reactant (e.g. waste plastics) in CFP can significantly improve the yield of aromatics and lower the coke formation. Catalytic co-pyrolysis can also reduce the disposal of waste polymers (plastics and waste tires) in landfills, solve some environmental issues, and further increase energy security. In this regard, this article reviews the catalytic co-pyrolysis process from several points of view, starting from feedstock characteristics and availability, current understanding of the chemistry in non-catalytic co-pyrolysis, and focusing on the chemistry in the catalytic co-pyrolysis of biomass with various categories of polymers. Recent progress in the experimental studies on both the non-catalytic pyrolysis and catalytic co-pyrolysis of biomass with polymers is also summarized with the emphasis on the liquid yield and quality. In addition, reaction kinetics and several outlooks in the light of current studies are also presented in the review. Consequently, this review demonstrates both highlights of the remarkable achievement of catalytic co-pyrolysis and the milestones that are necessary to be garnered in the future.

Hydrocarbon and hydrogen-rich syngas production by biomass catalytic pyrolysis and bio-oil upgrading over biochar catalysts

The focus of this study is to investigate the influences of biochar as a catalyst in biomass pyrolysis and bio-oil upgrading. The biochar catalyst enhanced the syngas and improved the bio-oil quality in biomass pyrolysis. The high concentrations of phenols (46 area%) and hydrocarbons (16 area%) were obtained from torrefied biomass catalytic pyrolysis over biochar catalysts. High-quality syngas enriched in H2, CO, and CH4 was observed. The amounts of H2 and CO in syngas were up to 20.43 vol% and 43.03 vol% in raw biomass catalytic pyrolysis, and 27.02 vol% and 38.34 vol% in torrefied biomass catalytic pyrolysis. Thermal gravimetric (TG) analysis showed that the raw and recycled biochar catalysts had good thermal stability. Upgraded bio-oil was dominated by phenols (37.23 area%) and hydrocarbons (42.56 area%) at high biochar catalyst loadings. The biochar catalyst might be used as a cost-competitive catalyst in biomass conversion and bio-oil upgrading.

From lignocellulosic biomass to renewable cycloalkanes for jet fuels

A novel pathway was investigated to produce jet fuel range cycloalkanes from intact biomass. The consecutive processes for converting lignocellulosic biomass into jet fuel range cycloalkanes principally involved the use of the well-promoted ZSM-5 in the process of catalytic microwave-induced pyrolysis and RANEY® nickel catalysts in the hydrogen saving process. Up to 24.68% carbon yield of the desired C8–C16 aromatics was achieved by catalytic microwave pyrolysis at 500 °C. We observed that solvents could assist in the hydrogenation reaction of naphthalene; and the optimum result for maximizing the carbon selectivity (99.9%) of decalin was obtained from the reaction conducted in the n-heptane medium. The recovery of organics could reach ∼94 wt% after the extraction process. These aromatics in the n-heptane medium were eventually hydrogenated into jet fuel range cycloalkanes. Various factors were analyzed to determine the optimal result under mild conditions. An increased catalyst loading, reaction temperature, and prolonged time could enhance the hydrogenation reactions to improve the selectivity of jet fuel range cycloalkanes. Three types of hydrogenation catalysts (NP Ni, RANEY® Ni 4200, home-made RANEY® Ni) were chosen to evaluate the catalytic performance. The results indicated that the home-made RANEY® nickel is the optimal catalyst to obtain the highest selectivity (84.59%) towards jet fuel range cycloalkanes. These cycloalkanes obtained can be directly used as additives to synthesize the desired jet fuels by blending with other hydrocarbons. Hence integration of catalytic processes and conversion of lignocellulosic biomass paved a new avenue for the development of green bio-jet fuels over inexpensive catalysts under mild conditions.

Optimizing carbon efficiency of jet fuel range alkanes from cellulose co-fed with polyethylene via catalytically combined processes

Enhanced carbon yields of renewable alkanes for jet fuels were obtained through the catalytic microwave-induced co-pyrolysis and hydrogenation process. The well-promoted ZSM-5 catalyst had high selectivity toward C8-C16 aromatic hydrocarbons. The raw organics with improved carbon yield (∼44%) were more principally lumped in the jet fuel range at the catalytic temperature of 375°C with the LDPE to cellulose (representing waste plastics to lignocellulose) mass ratio of 0.75. It was also observed that the four species of raw organics from the catalytic microwave co-pyrolysis were almost completely converted into saturated hydrocarbons; the hydrogenation process was conducted in the n-heptane medium by using home-made Raney Ni catalyst under a low-severity condition. The overall carbon yield (with regards to co-reactants of cellulose and LDPE) of hydrogenated organics that mostly match jet fuels was sustainably enhanced to above 39%. Meanwhile, ∼90% selectivity toward jet fuel range alkanes was attained.

Development of a catalytically green route from diverse lignocellulosic biomasses to high-density cycloalkanes for jet fuels

This study reports a novel route to manufacture high-density cycloalkanes for jet fuels from diverse lignocellulosic biomasses. The consecutive processes for manufacturing high-density cycloalkanes primarily included the catalytic microwave-induced pyrolysis of diverse lignocellulosic biomasses (hybrid poplar, loblolly pine and Douglas fir) over a well-promoted ZSM-5 and a hydrogenation process in the presence of a RANEY® nickel catalyst. Two variables (catalytic temperature and catalyst-to-biomass ratio) were employed to determine the optimal conditions for the production of C8–C16 aromatics in the catalytic microwave-induced pyrolysis. The maximum carbon yield of the desired aromatics was 24.76%, which was achieved from the catalytic microwave-induced pyrolysis of hybrid poplar at 500 °C with the catalyst-to-biomass ratio of 0.25. We observed that the aromatics derived from catalytic microwave-induced pyrolysis in the n-heptane medium were completely hydrogenated into renewable high-density cycloalkanes for jet fuels. In the hydrogenation process, increasing the catalyst loading and reaction temperature could promote the selectivity to high-density cycloalkanes. The results indicated that hybrid poplar was the optimal feedstock for obtaining the highest selectivity (95.20%) towards high-density cycloalkanes. The maximum carbon yield of cycloalkane-enriched hyrogenated organics based on hybrid poplar was 22.11%. These high-density cycloalkanes with high selectivity can be directly used as additives in jet fuels, such as JP-5, JP-10 and RJ-5.

Microwave pyrolysis of Douglas fir sawdust pellet

Microwave pyrolysis of Douglas fir sawdust pellet was investigated to determine the effects of reaction temperature and time on the yields of bio-oil, biogas, and biochar using a central composition design (CCD) and response surface analysis. The research results indicated that thermochemical conversion reactions can take place rapidly in large-sized biomass pellet by using microwave pyrolysis. The yields of bio-oil and biogas were increased with the reaction temperature and time. The highest yield of bio-oil was 53.9% (wet biomass basis) obtained at 470.7°C and 15min. GC/MS analysis indicated that the bio-oils were mainly composed of phenols, guaiacols, furans, ketones/aldehydes, and organic acids. The phenols and guaiacols accounted for the largest amount of chemicals in the bio-oil, which represented 59.7–78.6% under different conditions. The biogases contained high value chemicals, such as carbon monoxide, methane, and short chain hydrocarbons. A third-order reaction mechanism fits well the microwave pyrolysis of Douglas fir pellet with activation energy of 33.5 kJ/mol and a frequency factor of 3.03 s–1.