Ethane Steam Reforming over a Platinum/Alumina Catalyst: Effect of Sulfur Poisoning

Claire Gillan,Sam French,S David Jackson,Martin Fowles

doi:10.1021/ie401999t

Abstract

In this study we have examined the adsorption of hydrogen sulfide and methanethiol over platinum catalysts and examined the effect of these poisons on the steam reforming of ethane. Adsorption of hydrogen sulfide was measured at 293 and 873 K. At 873 K the adsorbed state of hydrogen sulfide in the presence of hydrogen was SH rather than S, even though the Pt:S ratio was unity. The effect of 11.2 ppm hydrogen sulfide or methanethiol on the steam reforming of ethane was studied at 873 K and 20 barg. Both poisons deactivated the catalyst over a number of hours, but methanethiol was found to be more deleterious, reducing the conversion by almost an order of magnitude, possibly due to the co-deposition of sulfur and carbon. Changes in the selectivity revealed that the effect of sulfur was not uniform on the reactions occurring, with the production of methane reduced proportionally more than the other products, due to the surface sensitivity of the hydrogenolysis and methanation reactions. The water-gas shift reaction was affected to a lesser extent. No regeneration was observed when hydrogen sulfide was removed from the feedstream in agreement with adsorption studies. A slight regeneration was observed when methanethiol was removed from the feed, but this was believed to be due to the removal of carbon rather than sulfur. The overall effect of sulfur poisoning was to reduce activity and enhance hydrogen selectivity.

Highlights

Steam reforming is the most widely practiced process for the production of hydrogen, accounting for the production of 96% of on-purpose hydrogen
Hydrogen sulfide did not adsorb on the silica support but did adsorb on the alumina; the adsorption data for the Pt/alumina catalyst had the support contribution subtracted from the total adsorption
In this study we have examined the adsorption of hydrogen sulfide and methanethiol over platinum catalysts and examined the effect of these poisons on the steam reforming of ethane

Summary

Introduction

Steam reforming is the most widely practiced process for the production of hydrogen, accounting for the production of 96% of on-purpose hydrogen. Adsorbed sulfur will poison the site on which it is adsorbed, and it may poison a larger number of sites by removing a geometrical degree of freedom from the surface.[1,2] In addition the formation of a bond between a metal atom in an array and a sulfur atom may affect the ability of neighboring metal atoms to form bonds of the correct strength to allow a catalytic reaction to occur This type of behavior has been well-understood for many years, at least empirically, and has been used to good effect in the reforming industry.[3]

Results

Discussion

Conclusion