Production of inherently separated syngas streams via chemical looping methane cracking

Abstract

‘Chemical Looping Combustion’ (CLC) is an emerging clean combustion technology which offers an efficient route for fossil fuel combustion with inherent CO2 capture. Beyond combustion, chemical looping is also applicable to selective oxidation of fuels to synthesis gas or olefins. In all these applications, the main advantage of chemical looping lies in the inherent air separation, which allows conversion of the fuel without nitrogen dilution. In the present work, we extend this inherent separation principle to separation of the product stream by demonstrating the formation of fully separated syngas streams from methane, i.e. the production of separate, high-purity CO and H2 streams via (non-oxidative) methane cracking. CH4 is first cracked catalytically over Ni, producing gaseous H2 and solid carbon. The carrier is then periodically regenerated by burning off the carbon using CO2 as oxidant, thus enabling the reduction of CO2 to CO. Importantly, the Ni carrier is never oxidized during this cycle and hence acts as a “carbon carrier” rather than as an oxygen carrier as typical in chemical looping processes to-date. Autothermal process configurations are discussed, which allow reconciling the use of abundant natural gas reserves with the demand for clean, carbon-free energy production.