Dehydrogenation of Lower Alkanes Using H2S

Abstract

Propylene is an important building block for the production of polypropylene, propylene oxide, and acrylonitrile. The main processes for propylene production are steam cracking (SC) of naphtha and fluid catalytic cracking (FCC). The processes of SC and FCC produce ethylene and gasoline as the main products, respectively, and propylene as a by-product1),2). Although the global demand for propylene increases by approximately 4-5 % per year, there is a risk of shortage of propylene supply3). Therefore, to fulfill the global demand for propylene, the operations of the SC and FCC processes are optimized for lesser production of ethylene and gasoline, respectively, and greater production of propylene4)~6). Recently, the dehydrogenation reaction of propane (C3H8 → C3H6+H2) has received significant attention because dehydrogenation can convert the economic feedstock of propane to valuable propylene7). Because the reaction is reversible, prone to volume expansion, and highly endothermic, higher temperatures and lower pressures are preferred for this reaction. The most important aspect of propane dehydrogenation is the energy required for the endothermic reaction8). However, heat input to the reactor is a major technical challenge. A high reaction temperature used for the replenishment of the heat absorbed during the endothermic reaction results in the occurrence of side reactions and formation of coke, and deactivates the catalyst9),10). Current state-of-the-art research focuses on investigating the synergistic effects of gas-phase oxidants and alkanes to overcome the obstacles to industrial dehydrogenation reactions11). It has been established that catalytic oxidative dehydrogenation (ODH) reactions are sensitive to certain oxidizing agents. A number of oxidants such as oxygen, nitrous oxide, and carbon dioxide have been investigated for the propane dehydrogenation reaction12)~16). ODH can proceed at low temperatures because of the exothermic nature of the reaction without thermodynamic constraints. A vanadium-based material was found to be a selective catalyst for ODH with oxygen, because of its favorable redox properties. Carrero et al. reported that (VOx)n (TiOx)m-supported on SBA-15 catalyst showed a propane conversion of 10 % with a 60 % selectivity for the production of propylene; these values are superior to those of all other V-based catalysts reported to date17). High VOx dispersion is required to achieve high propylene selectivity, and the formation of a linked VTi oxide monolayer is crucial to obtain high reaction rates with relatively high propylene selectivity. Boron nitride (BN) was also reported to display high activity and selectivity; the resultant conversion was 14 % with a 79 % selectivity for the propylene18),19). Lots of studies are focused on enhancing propylene selectivity, however it [Review Paper]