Combined Hydrogen and Oxygen transport membranes in the activation of Methane

Abstract

Dense ceramic membranes have been extensively studied for gas separation and as reaction supports for significant environmental processes. In the work presented in this thesis, yttrium/zirconia doped barium cerate (BaCe0.8Y0.2O3-δ- BCY20 and BaCe0.6Zr0.2Y0.2O3-δ- BCZY) powders were synthesised using the sol-gel method and were calcinated to remove impurities (e.g. carbonates) in both conventional and microwave sintering furnaces at 900-1250OC, to understand the process and attempt to reduce the calcination temperature. Results from the calcination tests proved that the use of a microwave furnace can reduce the calcination time and temperature for BCY20, from 1200OC for 12h in a conventional furnace, to 1000OC for 1h, thereby saving time and energy. For BCZY, the using a microwave furnace does not make a difference to the calcination temperature, the addition of the high melting point ZrO2 could not be removed at temperatures below 1250OC. BCZY20 and BaCe0.6Zr0.2Y0.2O3-δ-Ce0.8Gd0.2O3-δ dense membranes, were produced in the laboratory at low temperatures (1150OC), with the addition of 1-2% ZnO sintering aid and microwave furnace, alongside the samples containing 2% ZnO displaying a 92% relative density when sintered at 1150OC for 6h. The success of producing a dense membrane in the laboratory meant catalytic tests could be completed. BaCe0.6Zr0.2Y0.2O3-δ was selected as the membrane support for wireless Electrochemical Promotion for CO oxidation on Pt. In a dual-chamber reactor, the use of H2/H2O flow in the sweep side, induced promoting species supply, to the catalyst in the reaction side of the reactor. Moderate promotion of the catalytic rate up to 10%, was observed for temperatures up to 650OC, while this promotional effect was reversible and repeatable. The encouraging preliminary catalytic experiments together with the membrane’s stability under the applied conditions reinforce the candidacy of BCZY membranes for intermediate-temperature applications in catalytic membrane reactors. Continuing with the success of the wireless EPOC of CO oxidation on Pt using BCZY support, BCZY:CGO hollow fibre hybrid membrane was applied to the dehydrogenative conversion of methane with in-situ continuous removal of hydrogen in a hollow fibre catalytic membrane reactor (HFCMR).

This proved successful at 775OC, in a counter current setup, the use of a membrane showed 50% increase of reaction rate compared to a regular packed bed reactor, injecting air into the sweep side of the system, to permeate into the reactor side and burn the poisoning carbonous product off to increase the reactions lifetime, albeit with a slight decrease in rate due to the production of CO and CO2.

Date of Award	Jul 2021
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	Department of Higher and Further Education, Training and Employment
Supervisor	Danai Poulidi (Supervisor) & Lorenzo Stella (Supervisor)