Abstract
In this study, the application of a calcium-based bifunctional catalyst/sorbent is investigated in modified chemical looping steam methane reforming (CLSMR) process for in situ CO2 sorption and H2 production. The yttrium promoted Ca-Co samples were synthesized and applied as bifunctional catalysts/sorbent. The influence of reduction temperature (500–750 °C), Ca/Co and Ca/Y ratios (1.5–∞ and 3–18, respectively) and catalyst life time are determined in CLSMR process. The physicochemical transformation of fresh, used and regenerated samples after 16 redox cycles are determined using X-ray powder diffraction (XRD), N2 adsorption–desorption, field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM) techniques. The effect of yttrium promoter on the structure of catalyst and regeneration step on the reversibility of bifunctional catalyst/sorbent was two important factors. The characterization results revealed that the presence of yttrium in the structure of Ca-9Co sample could improve the morphology and textural properties of catalyst/sorbents. The suitable reversibility of bifunctional catalyst/sorbents during the repeated cycles is confirmed by characterization of calcined samples. The Ca-9Co-4.5Y as optimal catalyst illustrated superior performance and stability. It showed about 95.8% methane conversion and 82.9% hydrogen yield at 700 °C and stable activity during 16 redox cycles.
Highlights
IntroductionExcessive consumption of fossil fuels (natural gas, coal and oil) and emission of large amount of greenhouse gases such as CO2 have an uncontrollable impact on global warming
Excessive consumption of fossil fuels and emission of large amount of greenhouse gases such as CO2 have an uncontrollable impact on global warming
The freshly synthesized samples were characterized before activity tests, after reduction period and after calcination/oxidation section to investigate the structural changes of each catalyst/sorbent
Summary
Excessive consumption of fossil fuels (natural gas, coal and oil) and emission of large amount of greenhouse gases such as CO2 have an uncontrollable impact on global warming. This matter has increased worldwide environmental concern [1,2,3,4]. Hydrogen could be used as an important feedstock in different chemical and petrochemical processes such as methanol, ammonia and hydrochloric acid production It is a suitable fuel for fuel cells, turbines and internal combustion engines [7,11,12,13,14,15]. It has high hydrogen to carbon ratio and produces fewer
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