Yu-Ting Cheng

Production of green aromatics and olefins by catalytic fast pyrolysis of wood sawdust

Catalytic fast pyrolysis of pine wood sawdust and furan (a model biomass compound) with ZSM-5 based catalysts was studied with three different reactors: a bench scale bubbling fluidized bed reactor, a fixed bed reactor and a semi-batch pyroprobe reactor. The highest aromatic yield from sawdust of 14% carbon in the fluidized bed reactor was obtained at low biomass weight hourly space velocities (less than 0.5 h−1) and high temperature (600 °C). Olefins (primarily ethylene and propylene) were also produced with a carbon yield of 5.4% carbon. The biomass weight hourly space velocity and the reactor temperature can be used to control both aromatic yield and selectivity. At low biomass WHSV the more valuable monocyclic aromatics are produced and the formation of less valuable polycyclic aromatics is inhibited. Lowering the reaction temperature also results in more valuable monocyclic aromatics. The olefins produced during the reaction can be recycled to the reactor to produce additional aromatics. Propylene is more reactive than ethylene. Co-feeding propylene to the reactor results in a higher aromatic yield in both continuous reactors and higher conversion of the intermediate furan in the fixed bed reactor. When olefins are recycled aromatic yields from wood of 20% carbon can be obtained. After ten reaction–regeneration cycles there were metal impurities deposited on the catalyst, however, the acid sites on the zeolite are not affected. Of the three reactors tested the batch pyroprobe reactor yielded the most aromatics, however, the aromatic product is largely naphthalene. The continuous reactors produce less naphthalene and the sum of aromatics plus olefin products is higher than the pyroprobe reactor.

Catalytic conversion of biomass-derived feedstocks into olefins and aromatics with ZSM-5: the hydrogen to carbon effective ratio

Catalytic conversion of ten biomass-derived feedstocks, i.e.glucose, sorbitol, glycerol, tetrahydrofuran, methanol and different hydrogenated bio-oil fractions, with different hydrogen to carbon effective (H/Ceff) ratios was conducted in a gas-phase flow fixed-bed reactor with a ZSM-5 catalyst. The aromatic + olefin yield increases and the coke yield decreases with increasing H/Ceff ratio of the feed. There is an inflection point at a H/Ceff ratio = 1.2, where the aromatic + olefin yield does not increase as rapidly as it does prior to this point. The ratio of olefins to aromatics also increases with increasing H/Ceff ratio. CO and CO2 yields go through a maximum with increasing H/Ceff ratio. The deactivation rate of the catalyst decreases significantly with increasing H/Ceff ratio. Coke was formed from both homogeneous and heterogeneous reactions. Thermogravimetric analysis (TGA) for the ten feedstocks showed that the formation of coke from homogeneous reactions decreases with increasing H/Ceff ratio. Feedstocks with a H/Ceff ratio less than 0.15 produce large amounts of undesired coke (more than 12 wt%) from homogeneous decomposition reactions. This paper shows that the conversion of biomass-derived feedstocks into aromatics and olefins using zeolite catalysts can be explained by the H/Ceff ratio of the feed.

Production of p‐Xylene from Biomass by Catalytic Fast Pyrolysis Using ZSM‐5 Catalysts with Reduced Pore Openings

Pores for thought: Chemical liquid deposition of silica onto ZSM-5 catalysts led to smaller pore openings that resulted in >90% selectivity for p-xylene over the other xylenes in the catalytic fast pyrolysis of furan and 2-methylfuran (see scheme). The p-xylene selectivity increased from 51% with gallium spray-dried ZSM-5 to 72% with a pore-mouth-modified catalyst in the pyrolysis of pine wood.

Production of targeted aromatics by using Diels–Alder classes of reactions with furans and olefins over ZSM-5

In this paper we study the co-feeding of olefins (ethylene and propylene) with a series of furanic compounds (furan, 2-methylfuran, furfural, and furfuryl alcohol) over ZSM-5 catalyst in a continuous flow fixed-bed reactor at a temperature range of 450–600 °C. We show the importance of Diels–Alder cycloaddition reactions when olefins are co-fed with furanics over ZSM-5. Co-feeding propylene with furan (C4 diene) increased the toluene aromatic selectivity from 22% to 59%. Similarly, co-feeding propylene with 2-methylfuran (C5 diene) increased the xylenes aromatic selectivity from 9% to 27%. Co-feeding of ethylene with furans did not change the aromatics selectivity. The increase of toluene selectivity was also observed in the co-feeding of propylene with furfural and fufuryl alcohol. Furfural and furfuryl alcohol both underwent decarbonylation reactions to produce CO and furan. The reaction conditions that maximize Diels–Alder products were a propylene to 2MF molar ratio of 1 at 450 °C. Increasing the temperature to 600 °C increased the selectivity of benzene, toluene and CO. Decreasing the temperature to 300 °C increased the coke yield and decreased the xylene yield. The xylene selectivity went through a maximum at a propylene to 2-methylfuran molar ratio of 1 : 1.