c) Although the precise mechanism of thiophene HDS reaction is still under debate. Borgna et al, 2003 used a simplified reaction network consisting of elementary steps, in which thiophene (TH) exclusively adsorbs on sulfur vacancies and H2 adsorbs dissociatively on different sites to form butadiene ( B) and H2S. Assuming that the surface reaction between adsorbed thiophene and H2 is the rate limiting step (irreversible). Determine the Langmuir-Hinshelwood rate expression. Overall equation: TH+H2B+H2S i) Postulate a series of elementary steps and derive the rate expression. [11] ii) Discuss the effects of an increase in partial pressure of butane on reaction with time. [4]