Abstract
The utilization of fossil fuels has led to a gradual increase in greenhouse gas emissions, which have accelerated global climate change. Therefore, there is a growing interest in renewable energy sources and technologies. Biogas has gained considerable attention as an abundant renewable energy resource. Common biogases include anaerobic digestion gas and landfill gas, which can be used to synthesize high-value-added syngas through catalytic reforming. Because syngas (CO and H2) is synthesized at high reaction temperature, carbon is generated by the Boudouard reaction from CO and CH4 cracking; thus, C blocks the pores and surface of the catalyst, thereby causing catalyst deactivation. In this study, a simulation was performed to measure the CH4 and CO2 conversion rates and the syngas yield for different ratios of CO2/CH4 (0.5, 1, and 2). The simulation results showed that the optimum CO2/CH4 ratio is 0.5; therefore, biogas reforming over the 3 wt% Ni/Ce-MgO-ZrO2/Al2O3 catalyst was performed under these conditions. CH4 and CO2 conversion rates and the syngas yield were evaluated by varying the R values (R = (CO2 + O2)/CH4) on the effect of CO2 and O2 oxidants of CH4. In addition, steam was added during biogas reforming to elucidate the effect of steam addition on CO2 and CH4 conversion rates. The durability and activity of the catalyst after 200-h biogas reforming were evaluated under the optimal conditions of R = 0.7, 850 °C, and 1 atm.
Highlights
Owing to concern regarding the effects of climate change, many countries signed the “ParisAgreement” in 2015, agreeing to reduce greenhouse gas (GHG) emissions and limit the increase in global temperatures to below 1.5 ◦ C [1,2]
When the reverse water–gas shift (RWGS) reaction occurs during biogas reforming, the CO2 conversion rate tends to increase, and the carbon that is formed from the Boudouard and CH4 cracking reactions is deposited in the pores of the catalyst
This study achieves R values (0.6, 0.7, and 0.9; where R = ((O22 + CO22)/CH44)) for biogas reforming over the 3 wt% Ni/Ce-MgO-ZrO2 /Al2 O3 catalyst
Summary
Owing to concern regarding the effects of climate change, many countries signed the “Paris. MgO reportedly enhances the binding force in the presence of NiO, which improves the resistance of Ni-based catalysts to sintering and carbon formation and facilitates the highest catalytic performance [12]. Due to their redox properties and oxygen storage capacity, Ni-based catalysts supported on CeO2 or CeO2 -ZrO2 mixed oxides show promising performance, as well as low coke formation. Trutchetti et al [13] studied the kinetics of CH4 steam reforming over Ni-based catalysts and confirmed that the activation energy of the Pt-added catalyst was lower than that when the Pt-added Ni-based catalyst was supported on CeO2 and Ce-Zr-La. Sunarno et al [14] showed that the rate constants of the catalytic cracking of bio-oil increased with an increasing temperature.
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