Sorption enhanced steam reforming of ethanol for hydrogen production

R. AVENDAÑO; M. L. DIEUZEIDE; ROBERTO TEJEDA; NORMA AMADEO

Conferencia; HYPOTHESIS XVI; 2021

Recently, it has been proposed H2 as a power vector, to replace fossil fuels such as oil, coke, and natural gas, due to their high environmental impact. One way to use H2 as a power source is in fuel cells, which requires high purity H2 to be effective [1]. Among main industrial processes for H2 synthesis the steam reforming of alcohols obtained from biomass is a sustainable alternative. Nevertheless, the H2 produced using this process contains significant amounts of CO, which poisons the anode at the PEM fuel cell and therefore it is necessary to be removed. To remove CO in gaseous product containing CH4, CO, CO2 and H2, successive operational units are used to decrease CO mainly. These units are based in chemical reactions as Water Gas Shift Reaction (WGSR) and Preferential Oxidation of CO (COPROX). Lately, several research [2] have studied sorbent materials that, working in the same reforming unit, eliminate the most amount of CO produced in ethanol reforming reaction through selective capture of CO2 (SESRE), by shifting equilibrium of CO-CO2 reaction (WGSR). In last years, SESRE has become an interesting approach for industry, because it offers high H2 purity with a simpler and smaller system. To improve feasibility on this process, it must be operated in multicyclic sorption-regeneration scheme, so it becomes important the use of materials that work under suitable conditions. For instance, there are several CO2 sorbents which require high regeneration temperatures, and as the number of sorption-regeneration cycles increases, the activity of the solid decreases due to sintering of its particles. Between different options, Hydrotalcite (HT), a layered double hydroxide material, has shown selective CO2 capture capacity and stability in multicyclic operation under mild temperatures [3]. Even when it is known that HT sorbent has low activity, this material seems to be a promising feedstock to develop solids with improved CO2 sorption capacity by means of increasing basicity of HT structure adding alkaline metals such as Na, K, Cs [4]. In this study it is proposed to synthesize sorbents based in HT impregnated with different loads of potassium (K), with the aim of evaluate in first instance, the effects of K on HT activity in CO2 capture, and then their performance in the SESRE process with a Ni-based catalyst, to produce high H2 purity under mild temperatures of each cycle of reaction and regeneration.