How Do Claus Catalysts Really Work?

摘要

This paper highlights some of the salient and practically important issues of catalyticconversion of H2S and SO S SO2 in the catalytic converter train of a Claus plant. In particular, theissue of sulfate formation on alumina is investigated as it relates to CS2 conversion, testing ofcatalysts for CS2 conversion activity, influence of HS/SO2 ratio on CS2 conversion andcatalyst fouling by BTX. The use of titania for CS2 conversion is also examined.Overall, it has been shown that the formation of sulfate on alumina is directly related to theoxidizing properties of alumina or titania and the chemistry of H2S/2 conversion overthese materials. Although sulfate is formed by O2 ingress into a converter, it will also bepresent on any Claus catalyst as a result of the Anatural@ chemistry of H2S/SO2 conversion.Hence, the presence of sulfate on a catalyst is not reason enough to decide on changing out acatalyst.An understanding of the occurrence of natural sulfate has enabled development of a robustcatalyst testing procedure which allows steady-state CS2 conversion to be evaluated quicklyand reliably. Also, it has been shown that the HS/SO2 ratio is an important parameteraffecting the catalyst sulfate levels and degree of CS2 conversion attainable in the plant.Importantly, high HS/SO2 ratios give greater CS2 conversion. These factors have importantramifications with respect to evaluation of plant performance data.BTX fouling has been shown to be a general consequence of catalyst sulfate leading to thepractical step that BTX would be dealt with most successfully upstream of the convertertrain.As is well known, titania is a superior material for CS2 conversion. Sulfate is also formed ontitania but it appears to have no influence on CS2 conversion at temperatures >320 320oC.Appreciable CS2 conversion can also be attained on titania at second converter conditions.The oxidizing properties of alumina and a chemical analysis of the initial steps of H2Soxidation by O2 has allowed us to develop a new process for the catalytic conversion of H2Sto hydrogen and sulfur. This type of process has the potential to radically alter the paradigmfor sulfur recovery from H2S.