(232d) Ethylene Production from Shale and Coal Derived Flue Gases

As an inexpensive and abundant source of energy, coal, provides ~41%¹ of the world’s electricity needs. Yet, coal based power plants are under serious scrutiny due to their damaging impact on the environment. In 2015, although coal contributed to 33%² of the total electricity production in the U.S., it was responsible for 71%³ of the total CO₂ emission from the U.S. electric power sector for the same year. One of the most attractive approaches to combat high GHG emission from coal-fired plants is CO₂ capture and conversion to higher value products.

Contemporaneously, thanks to the shale gas growth in the U.S., an excess supply for pure (extracted) ethane and other light hydrocarbons is available currently at low cost. As a result, an increasing number of steam cracker plants are using ethane as raw material to produce ethylene, the highest volume petrochemical intermediate produced in the world with a current global production capacity of 334 billion lb/year. Ethylene production from steam cracking is also an energy intensive process. A typical ethylene steam cracker plant consumes ~17-21 GJ/ton ethylene energy and emits ~1.0-1.2 ton CO₂/ton of ethylene⁴.

Southern Research (SR), in partnership with DOE/NETL is developing a low temperature ethylene production process using CO₂, notably from coal-fired flue gas streams, and readily available low cost ethane as raw materials. The proposed process proceeds through a less energy intensive oxidative dehydrogenation pathway by using SR’s recently developed low-cost mixed metal oxide catalyst which balances the functionalities between ethane activation and ethylene selectivity with a goal to ensure yields (>60%) higher than reported in literature. The process is also anticipated to benefit from the presence of several components of the flue gas from coal-fired plants and ensure lower downstream separation costs. IT is anticipated that this new process would (i) reduce the reaction temperature for ethylene production by at least 200°C from the conventional steam cracking and (ii) reduce overall GHG emission by ~35% for the combined coal-fired power plant and ethylene production process. With an existing SR catalyst formulation, high selectivity (99%) and high turn-over rates have already been achieved. This paper will discuss the catalyst screening and key performance results for further optimizing catalysts. The studied parameters include reaction temperature, ratio of ethane to oxidant and oxidizing agents (CO₂/O₂), catalyst deactivation, and impact on separations as a result of product selectivity and yield. References

[1] http://data.worldbank.org/indicator/EG.ELC.COAL.ZS, [2] Electric power monthly, Jan 2017, U.S. Energy Information Administration, [3] Monthly energy review. August 2016. U.S. Energy Information Administration. www.eia.gov/mer. [4] Ren, Tao, Martin Patel, and Kornelis Blok. Energy 31.4 (2006): 425-451.