The Porosoff group focuses on developing new catalysts for upgrading C1 and C2 resources for efficient energy storage and low-cost production of plastics, chemicals and fuels. Understanding the relationships between chemical reactivity and catalyst electronic/structure properties are extremely important for developing catalysts that exploit particular reaction pathways. This approach requires controlled synthesis of catalysts combined with in situ techniques and theoretical calculations. In particular, target areas of research are three types of catalytic reactions for improved shale gas utilization and lowering CO2 emissions: (I) Catalyst development for CO2 hydrogenation, (II) Selective synthesis of light olefins from CO and H2 and (III) Developing a new class of catalysts for oxidative coupling of methane. Experimental work combines an mix of catalyst synthesis and characterization, reactor studies and in situ spectroscopy.
Dual-functional catalysts for CO2 conversion to plastics, chemicals and fuels
Through a variety of catalytic reactions, waste CO2 can be converted to valuable oxygenates, specialty chemicals and hydrocarbons for synthetic fuel. There are many examples in literature of conversion of CO2 into CO, methane (CH4) and methanol; however, research of direct CO2 hydrogenation to light olefins (C2-C4 unsaturated hydrocarbons ie. ethylene and propylene) is limited. Converting CO2 to light olefins offers a means to store energy and convert waste CO2 into plastics, chemicals and fuels; however, the pathway is challenging because of the thermodynamic and kinetic limitations of activating the highly stable CO2 molecule.
The current approach for CO2 hydrogenation to hydrocarbons uses two reactors in series with high temperature reverse water-gas shift (RWGS, CO2 + H2 ↔ CO + H2O), followed by CO hydrogenation via Fischer-Tropsch (FT, nCO + 2nH2 → CnH2n + nH2O) synthesis. While there are groups investigating CO2 hydrogenation through direct Fischer-Tropsch (CO2-FT) over a single catalyst, the scientific challenges of precisely controlling selectivity to the desired products remain. The Porosoff group is investigating novel, dual-functional catalysts to selectively produce a tight distribution of hydrocarbons from CO2.
Selective Synthesis of Light Olefins from CO and H2
Light olefins (C2-C4) are important raw materials for manufacturing plastics, chemicals and synthetic fuels. Olefin synthesis mainly proceeds through steam cracking of naphtha, ethane and propane. Another route is coal gasification with O2 and H2O to make synthesis gas (CO + H2), which is converted to methanol over Cu/ZnO/Al2O3 catalysts. Methanol is then reacted over zeolites to synthesize olefins. Recent research efforts focus on direct conversion of synthesis gas to olefins through Fischer-Tropsch (FTO), bypassing the methanol intermediate. However, achieving high selectivity towards light olefins is difficult, because the products generally follow the Anderson-Schulz-Flory (ASF) distribution:
Future directions for designing selective catalysts will explore a combination of techniques to synthesize high surface area, mesoporous supports with effective promoters to control the size distribution of olefins. Experiments use a combination of in situ X-ray absorption fine structure (XAFS) and Fourier transform infrared (FTIR) spectroscopy to understand the effect of promoters on catalyst structure and electronic properties.
Developing a new class of catalysts for oxidative coupling of methane
The recent exploitation of natural gas reserves has increased the importance of developing novel routes for transforming light alkanes to value-added products. Oxidative coupling of methane (OCM, 2CH4 + O2 → C2H4 + 2H2O) is a highly desirable pathway to produce ethylene, thereby increasing the demand and value of methane feedstocks.
There has been extensive research into catalysts for OCM, but they still fall well short of the single-pass 90% C2 selectivity and 30% C2 yield required for commercialization. To improve upon OCM performance and achieve ethylene yield targets, a new class of catalysts must be developed with clear structure-property trends to better understand the fundamental design principles. The Porosoff group is developing catalysts to correlate oxygen binding energy (OBE), CO binding energy, and d-band center with activity and selectivity, as previously demonstrated for hydrogenation and deoxygenation reactions. The Porosoff group is using a novel synthesis approach to develop a class of low-cost, nano-catalysts, with easily tunable electronic properties.