Research Article Cite This: ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX pubs.acs.org/journal/ascecg Hydrogen-Rich Syngas Production through Synergistic Methane- Activated Catalytic Biomass Gasification † † † ‡ † Amoolya Lalsare, Yuxin Wang, Qingyuan Li, Ali Sivri, Roman J. Vukmanovich, ‡ † Cosmin E. Dumitrescu, and Jianli Hu*, † ‡ Department of Chemical and Biomedical Engineering and Department of Mechanical and Aerospace Engineering, West Virginia University, 395 Evansdale Drive, Morgantown, West Virginia 26505, United States *S Supporting Information ABSTRACT: The abundance of natural gas and biomass in the U.S. was the motivation to investigate the effect of adding methane to catalytic nonoxidative high-temperature biomass gasification. The catalyst used in this study was Fe− Mo/ZSM-5. Methane concentration was varied from 5 to 15 vol %, and the reaction was performed at 850 and 950 °C. While biomass gasification without methane on the same catalysts produced ∼60 mol % methane in the total gas yield, methane addition had a strong effect on the biomass gasification, with more than 80 mol % hydrogen in the product gas. This indicates that the reverse steam methane reformation (SMR) reaction is favored in the absence of additional methane in the gas feed as the formation of H2 and CO shifts the equilibrium to the left. Results showed that 5 mol % additional methane in the feed gas allowed for SMR due to formation of steam adsorbates from oxygen in the functional groups of aromatic lignin being liberated on the oxophilic transition metals like Mo and Fe. This oxygen was then available for the SMR reaction with methane to form H2, CO, and CO2. This study was not a detailed catalytic activity evaluation, but it was exploratory research to ascertain the synergy presented in the co-gasification of biomass and natural gas. KEYWORDS: Biomass gasification, Co-gasification of biomass and methane, FeMo/ZSM-5 catalyst ■ INTRODUCTION the world energy needs and the shift to renewable energy Per capita energy demand increased sharply over the last sources is not an easy task, owing to the high costs and unreliability of energy sources like solar and wind. Biomass, century, which caused irreversible changes in the weather − patterns across the globe.1 Climate change, which has long which accounts for 10 14% of the global energy supply, can been perceived as a futuristic phenomenon, is already replace fossil fuels as a reliable, sustainable, and green source of producing adverse climatic changes around the globe. The energy, contingent on the development of technologies that can harness its energy in clean, efficient, and economical (i.e., Downloaded via WEST VIRGINIA UNIV on September 18, 2019 at 20:33:19 (UTC). average annual temperature of the planet has already risen by ff 6 1.5 °C, and the current efforts in reducing emissions are cost-e ective) means. Even today, biomass accounts for most focused on curbing this temperature rise to 2 °C.2,3 At the of the energy utilized in the remotest, underdeveloped, and See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles. ff current rate of emissions, the planet may see a record developing regions globally. Biomass is available in di erent temperatureriseof2°C by 2050. According to the forms such as agricultural and forestry waste, animal waste, Intergovernmental Panel on Climate Change (IPCC), the biological materials byproducts, wood, and municipal waste. ’ These sources of biomass have vastly different moisture carbon dioxide (CO2) concentration in Earth s atmosphere has ffi crossed the unprecedented mark of 400 ppm.4 The world content and elemental compositions, thus making it di cult to develop a cost-effective technology which utilizes most types of community is diligently working toward moving to cleaner, 7,8 fi green, and sustainable energy sources like solar, wind, and biomass. Although woody biomass such as dry rewood is used in combustion for heating and power generation,9 the biomass to meet energy needs especially in the power and ffi transportation sectors.5 Biomass has been a major source of energy e ciency is low, and air emission control becomes an energy for humankind since the discovery of fire in the issue. In contrast, both heat and power generation require- ments using gasification can be met in an efficient, effective, prehistoric era and was the predominant source of fuel for 10 heating and cooking applications until fossil fuels like and clean way. Energy utilization by converting solid petroleum, coal, and natural gas were successfully harnessed feedstock to high-heating-value syngas is one of the cleanest in the 19th century. Fossil-fuel-based technologies enabled the human population to increase sharply from less than 1 billion Received: May 17, 2019 before the 18th century to more than 7 billion by 2020, a span Revised: August 22, 2019 of just three centuries. Fossil fuels account for nearly 80% of Published: September 4, 2019 © XXXX American Chemical Society A DOI: 10.1021/acssuschemeng.9b02663 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX ACS Sustainable Chemistry & Engineering Research Article ways to harness renewable energy source from woody biomass. abundant source like natural gas has a very high H/Ceff ratio of Biomass fast pyrolysis and gasification holds good potential for 4.39 In recent years, there have been efforts to utilize methane the production of hydrocarbon fuels and value-added and biomass in a single reactor, but mainly for the purpose of chemicals.11,12 Pyrolysis has been extensively researched and fast pyrolysis. In one of the recent studies, pine saw dust applied for producing biofuels for direct use in transportation biomass was impregnated with Ni and gasified with steam at 13−21 ° and related applications. However, the decomposition of 600 C to produce H2-rich syngas with maximum H2 yield of the highly aromatic lignin structure in lignocellulosic biomass 60% in the outlet gas. Steam was replaced by methane to leads to formation of bio-oil at temperatures below 700 perform catalytic methane decomposition (CMD) for 10 h at ° 22−24 ° C. Bio-oil is high in oxygen content and has limited 850 C on Ni/carbon catalyst to further increase H2. About direct application as fuel owing to high acidity, poor resistance 90% methane conversion was reported with the process.35 The to extreme weather conditions, and instability.11,25 These present study focuses on nonoxidative catalytic gasification in a limitations are the result of the highly oxygenated aromatic single stage using co-feeding of methane (5−15 mol %) with structure of biomass. The thermochemical conversion of biomass. Although renewable energy sources have started biomass to energy and fuels have been extensively studied contributing significantly to power generation in the US, for the past few decades.26,27 Biomass decomposes rapidly sources like solar and wind face severe limitations to be between 400 and 600 °C giving devolatilization components considered as mainstream source for power generation. Thus, like carbon monoxide (CO), carbon dioxide (CO2), methane natural gas biomass synergy is of key importance given the 9,11,12,22 (CH4), bio-oil, aerosols, and biochar. power and energy requirements of the US in coming decades. There have been numerous efforts to upgrade the yields With the abundance of natural gas in the US and especially the from biomass to value-added chemicals such as benzene, Appalachian region, efficient and cost-effective utilization of toluene, ethylbenzene, and xylene (BTEX), and produce natural gas for fuels and conversion to valuable chemicals along hydrogen-rich syngas.28,29 In situ tar cracking, hydrodeoxyge- with biomass offers great potential for meeting US energy nation (HDO), and rearrangement to form ketonic inter- needs in the near future. Methane is a major constituent in mediates leading to alkanes are typical reaction steps necessary natural gas (>80 mol %), which makes it an inexpensive source for conversion of biomass to valuable chemicals.28,30,31 of hydrogen for tar reforming in the biomass pyrolysis and Transition metals on catalytic surfaces like zeolite (HZSM- gasification process. Methane can be activated with the use of γ 33,40 5), SiO2, and -Al2O3 have been studied to initiate biomass- synthetic transition metal catalysts like Ni, Fe, Co. upgrading reactions like dehydration, rearrangement, decar- This study chose Fe−Mo/ZSM-5 for the co-gasification of boxylation, decarbonylation, and hydrodeoxygenation.7,28,32 methane and biomass at 750−950 °Cinafixed-bed reactor However, the complexity of reaction chemistry, the require- system. In general, zeolites such as ZSM-5 with acidic function ment of high-pressure hydrogen, and the rapid catalyst can be utilized to crack large molecules such as biomass. deactivation due to coke deposition and poisoning increases Adding metals to zeolite creates bifunctional properties − the cost of the process, rendering it economically nonviable. facilitating dehydrogenation and hydrogen transfer.41 43 Fe Methane-promoted catalytic biomass gasification can achieve on ZSM-5 was shown to assist methane decomposition with in situ tar reformation and cracking, thus producing high less energy intensive cleavage of the C−H bond.39,40,44 Fe- syngas yields with an enhanced H2/CO ratio, suitable for impregnated ZSM-5 catalyst has been subjected to high- chemical synthesis via a conventional Fischer−Tropsch (FT) temperature methane decomposition to produce hydrogen and synthesis process. Air−steam catalytic and noncatalytic gas- carbon nanotubes (CNTs). Fe−Mo/ZSM-5 catalyst has also fi i cation were reported on Ni/CeO2/Al2O3 with catalyst been utilized for methane and ethane dehydroaromatization loadings of 20−40% in a fluidized bed reactor at 725, 825, studies. Iron active sites supported on ZSM-5 have been shown and 900 °C.33 Nishikawa et al. reported that at 900 °C high to cause 3D coke deposition on the catalyst in the form of catalyst-to-biomass loading of 40% was effective in tar cracking CNTs.