Thermodynamics of hydrogen production by the steam reforming of butanol: Analysis of inorganic gases and light hydrocarbons

The thermodynamics of butanol steam reformation for the production of hydrogen were simulated using a Gibbs free-energy-minimisation method with water–butanol molar feed ratios (WBFR) between 1 and 18, a pressure range of 1–50 bar and reaction temperatures from 300 to 900 °C. The differences in H2 and CO production were calculated as functions of WBFR and temperature at 1 bar. On the basis of the equilibrium calculations with higher-hydrocarbon compounds excluded, the optimal operating conditions obtained were 600–800 °C, 1 bar and WBFR = 9–12. At these conditions, the yield of hydrogen and carbon monoxide was maximised and methane selectivity minimised. The yield of hydrogen was in the range of 75.13–81.27% (wet basis) with selectivities of 46.20–54.96%. This was achieved at a temperature of 800 °C and WBFR from 9 to 12. Carbon monoxide yield ranged between 65.48 and 55.57% (wet basis), with selectivities ranging from 14.56 to 10.66%. The formation of coke was completely inhibited at these operating conditions. In order to evaluate the effect of methane on coke formation at lower temperatures, simulations were performed in two sets, i.e., primary products (H2, CO, CO2 and C) including or excluding methane. The results indicate that some coke can be hydrogenated to methane at 300 °C and WBFR = 3, and that higher pressure favours hydrogenation reactions. Higher pressure had a negative effect on hydrogen and carbon monoxide yields.