Production of olefins by thermal cracking of natural gas condensates or light naphtha is an energy intensive process (20-40 GJth/tonne ethylene), leading to significant formation of coke and NOx along with 1.8-2 kg of CO2 per kg ethylene. The energy and carbon intensity of this process, combined with the high availability of ethane from shale gas has shifted North American ethylene production towards ethane cracking. However, ethane cracking does not produce the same amounts of C3+ olefins and di-olefins as naphtha cracking. We propose an alternative two-step redox (or chemical looping) oxy-cracking (CL-OxyC) scheme where hydrogen, produced from the cracking of light liquid paraffins, is selectively oxidized by lattice oxygen from a redox catalyst, in the first step. Regeneration of the lattice oxygen in a subsequent step heats the redox catalyst, providing the thermal energy needed for the cracking reaction. This process leads to minimal parasitic energy loss and significantly reduced CO2/NOx emissions, while promoting olefin formation through the removal of hydrogen. In the current study a promising Mn-based oxygen carrier is demonstrated and the CL-OxyC process is simulated with ASPEN Plus® using the demonstration data. CL-OxyC is compared with traditional naphtha-cracking for olefin production. Results indicate that the CL-OxyC process can reduce the overall energy demand and CO2 emissions by half. The upstream section consumes less energy while producing twice the amount of valuable heavy products per kg of feed hexane.

Olefin production from natural gas condensates using a cyclic redox scheme

255th National Meeting (2018)

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