[CCoE Notice] Cullen College Dissertation Announcement: Jonathan Ratcliff-ChBE

[Hutchinson, Inez A]

[Dissertation Defense Announcement at the Cullen College of Engineering]

Methane Oxidation and Tri-Reforming in Catalytic Monoliths:

Reactor Performance Features, Spatial Gradients, and Multiplicity



Jonathan Ratcliff

July 24, 2024; 10:00 AM - 12:00 PM

Location: Chemical Engineering Conference Room (S234)

Teams Link: https://urldefense.com/v3/__https://teams.microsoft.com/l/meetup-join/19*3ameeting_MTgyOTE3MmItZWM4ZS00OTZhLWIwYjQtODUwMmI1YTYyNTYy*40thread.v2/0?context=*7b*22Tid*22*3a*22170bbabd-a2f0-4c90-ad4b-0e8f0f0c4259*22*2c*22Oid*22*3a*22d12a08c9-8396-4e41-9a01-dbb685cb3f58*22*7d__;JSUlJSUlJSUlJSUlJSUl!!LkSTlj0I!G6dwmfths_4b1dpmHgM-Y3MTAWLZDLcZ4e62GHKs-9yvT36wmYQEwfXWfBnS66F2aQtG89wqoXF0AUVbaxvOoNAfGQg$ 

Committee Chairs:
Michael P. Harold, PhD

Committee Members:
Praveen Bollini, Ph.D. | Lars Grabow, Ph.D. | Stanko Brankovic, Ph.D |

Ram Ratnakar, Ph.D

Abstract

       This work investigates Pt/Pd/Al2O3 monoliths for mitigating greenhouse gas (Methane, CO2) emissions through two approaches: rich methane oxidation for natural gas vehicles and methane tri-reforming for syngas production from power plant flue gas. Rich methane oxidation on these catalysts reveals isothermal steady state multiplicity in the form of a clockwise hysteresis loop of methane conversion versus oxygen concentration. There are three distinct steady state branches with respect to feed oxygen concentration; these include a high activity, positive dependence on oxygen, a branch of negative dependence on oxygen and reducing activity, and a fully inhibited branch. Spatially-resolved mass spectrometry measurements map out the species concentration profiles. In the negative dependence region spatial measurements identified co-existing active and inhibited states in independent monolith channels. To explain this finding a microkinetic model was developed. The model demonstrated that the multiplicity arose from the competitive adsorption between oxygen and methane. Separate modeling of lean methane oxidation catalysts was performed to aid in the design/operation of novel catalysts.

      Methane tri-reforming experiments reveal a distinct spatial pattern with oxidation preceding downstream reforming reactions. Temperature profiles obtained via optical frequency domain reflectometry confirmed this trend. Operational parameters were varied, with there being a positive impact on conversion with increasing temperature, higher oxygen concentrations promoting CH4 but not CO2 conversion, and water having an inverse impact on CO2 conversions. Modeling was also carried out to determine the impact that thermal exchange reactor design would have on greenhouse gas conversion. It reveals that there is a potential to increase the greenhouse gas conversion by allowing for thermal exchange within the reactor.

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