Exploring on-board reforming technologies, particularly diesel steam reforming, is a contemporary research in the modern hydrogen production technology. One of the main problems in reforming logistics fuels is the presence of sulfur (ranging from few ppm to over thousand ppm). Diesel steam reforming is generally carried out using n-hexadecane as a surrogate fuel to mimic diesel. Reforming such long chain hydrocarbons typically involve deactivation of catalyst over short time on streams (partly due to sulfur). In order to improve the sulfur resistance of metal supported catalysts, we must know how sulfur chemisorbs on the metal sites. Understanding the mechanism of sulfur interaction would help us get insights into deactivation and thereby help in designing a better catalyst for improved performance. In the present work, we looked at the effect of sulfur on different Rh-Ni catalyst supported on alumina.

The effect of sulfur was studied at 800 deg C, 1 atm and S/C ratio of 3 with different Rh-Ni catalysts. Thiophene was used as the source of sulfur at 1000 wppm. In general, the presence of sulfur increased the coking rate on the support but had negligible effect on the metal. Presence of Rh in small quantities tends to increase sulfur resistance but when present in higher amounts gives lesser hydrogen yields. Various factors such as coking,nickel particle sintering, phase transformation, degree of reduction and support acidity were discussed to explain this effect. Techniques such as X-ray diffraction, X-ray photoelectron spectroscopy, Transmission electron microscopy, Temperature programmed oxidation, reduction and ammonia desorption were employed in the present study.