Production of low carbon number olefins from natural gas: Methane-involved catalytic non-oxidative propane dehydrogenation

Abstract

Low carbon number olefins such as ethylene and propylene are important chemical products with large production and extensive usage. Natural gas is a clean and abundant natural resource, which mainly contains methane as the major component and co-existing other light alkanes. It is highly efficient and profitable if natural gas can be directly converted to low carbon number olefins in a one-step process. In this work, non-oxidative dehydrogenation is practiced under mild reaction conditions using a simulated natural gas consisting of methane and propane with their natural abundance. It is found that similar amounts of methane and propane are converted simultaneously over a Pt-based catalyst with an interesting product distribution where low carbon number olefins are dominant. Control experiments demonstrate a synergistic effect between methane and propane, which is responsible for the distinctive reaction behaviors that enable effective natural gas conversion towards desired products. The catalyst optimization is also performed and PtRu/mesoTiO2 is selected as the candidate with both high activity and preferred product selectivity. Completely different product compositions are obtained when thermodynamic equilibrium calculations are compared with experimental results, indicating the reaction process is heavily kinetically controlled. After excluding the possibility of mass transfer limitations, a simplified kinetic model is established and tested to be capable of describing the experimental observations, which also better explains the uniqueness of the process with co-fed methane and propane. The study concerning methane-involved catalytic propane dehydrogenation could help to develop an innovative process for better utilization of natural gas resources.