Design considerations for vapor phase heterogeneous reaction processes in methanol steam reformers

Abstract

There are significant problems with current methanol steam reformer approaches as applied to vapor phase heterogeneous catalysis. There remains a need for further development in methanol steam reformer processes and systems. The present study aims to provide an improved reactor system and process for the carrying out of vapor phase heterogeneous reactions. The effect of temperature on the methanol mole fraction and effective factor is investigated for a microchannel methanol steam reformer with different shapes of the cross section of the process microchannel. Particular emphasis is placed upon the heat and mass characteristics involved in vapor phase heterogeneous reaction processes in methanol steam reformers. The results indicate that the steam reforming catalyst is adapted to produce a reformate stream from the feed stream, which is delivered to the reforming region at an elevated temperature and pressure. The fuel stream tends to vary in composition and type depending upon the mechanisms used to produce heat. Methanol is a particularly well-suited carbon-containing feedstock for steam reforming reactions. Methanol steam reforming typically takes place at a lower temperature than when other carbon-containing feedstocks are reformed. A methanol steam reforming catalyst is additionally or alternatively not pyrophoric. A benefit of a low temperature shift catalyst is that the reforming catalyst beds do not need to be shielded or otherwise isolated from contact with air to prevent spontaneous oxidation of the catalyst. Improving heat flux from tubular reactor outer environment to inner environment is a critical step to increase reactor efficiency. Smaller diameter catalytic reactors can offer several advantages of improving heat transfer from external heat source to reaction mixture in the tube, enhancing tube life-time by reducing thermal gradients, reducing metal material use, and being applicable for compact steam reformer systems. Keywords: Heterogeneous catalysis; Vapor phases; Reaction processes; Diffusion coefficients; Heat fluxes; Support structures