(70a) Economic and Environmental Assessment of Methane to Ethylene Via Oxidative Coupling

Approximately 400 million barrels of ethylene were produced in U.S. gas plants in 2015, making it one of the world's largest volume commodity chemicals. Ethylene is valuable as a precursor to a variety of products; mostly low and high density polyethylene but also vinyl chloride monomer (VCM), ethylene glycol, and styrene. Because of its high volume, finding cheaper feedstocks is one of the few ways to have an impact on the ethylene production market. Oxidative Coupling of Methane (OCM) has long been studiedas a way to use low-value methane to make ethylene by reacting it catalytically with oxygen; unfortunately, methane conversions and selectivities in OCM reactors with ordinary catalysts have historically been too low to make the process viable.

Recently, Siluria Technologies has patented a novel inorganic polycrystalline nanowire OCM catalyst with commercially viable selectivities and conversions. They report methane conversions of 20-30% with a 60-70% selectivity to two-carbon products(ethane, ethylene, and acetylene) on a long-lived catalyst material. With this improved catalyst performance, full scale OCM reactors may start to be economically viable as competitors with traditional hydrocarbon cracking.

This work proposes one possible process design for the production of ethylene (and byproducts) from methane and air or oxygen. We assume a claimed reactor performance and design a separation system to make 99.95% pure ethylene for polymerization. We are interested in producing both economic (via detailed costing of an optimized design) and environmental (via LCA) performance targets on this OCM process to possibly show its potential to produce valuable products from methane in a low-cost and low-impact way.

We will discuss the possible process choices, a simulation of our proposed separation system, a pinch analysis/heat integration of that system, a full cost analysis, and a cradle-to-gate LCA of the energy and carbon impact of OCM versus conventionally produced ethylene.