Experimental and computational study of glycerol reforming over wall-coated microchannels

Abstract

This study aimed to investigate intensified glycerol reforming both experimentally and computationally. In the experimental part, gas phase oxidative steam reforming (OSR) of glycerol is carried out in an in-house designed microchannel reactor whose inner wall is coated with Rh/Al2O3 catalyst. The effects of operating parameters such as reaction temperature, molar inlet carbon-to-oxygen (C/O) and steam-to-carbon (S/C) ratios on glycerol conversion and product distribution are studied. Product analysis is carried out by two online gas chromatographs. The results show that glycerol conversion is enhanced by temperature as the glycerol decomposition is endothermic. Complete glycerol conversion is achieved over the temperature range of 600-700 °C at C/O of 1.125. S/C effect on OSR of glycerol is found to be much less significant as compared to C/O and temperature effects. Conversion and H2 yield slightly improved with steam content of the feed via WGS and possible coke gasification. It is observed that obtaining a desirable H2/CO ratio in the product stream, which is found to be in the range of 0.5-1.8, is feasible through changing C/O, S/C and temperature. In the computational part of the work, glycerol steam reforming (SR) is investigated in a heat exchange integrated microchannel reactor by means of mathematical modeling techniques. Heat needed for endothermic glycerol SR taking place in Co-Ni/Al2O3 coated channels is supplied by steam flowing in the adjacent channels separated by solid walls. The effects of operational parameters, namely S/C and temperature of the reactive mixture, inlet temperature and velocity of steam, flow configurations of the reactive mixture and steam, and of structural parameters, i.e. reactor wall material and thickness of the wall between the channels on temperature distribution and on glycerol conversion are studied. Product distribution is found to be in alignment with those of experimental studies reported in the literature. The simulation suggests that selectivity towards H2 is positively correlated with the degree of uniformity of reaction channel temperature, which is also found to dampen undesired CH4 selectivity.