Hybrid non-thermal plasma (NTP) catalysis-separation system for upgrading biogas

Abstract

In recent years, anaerobic digestion of biomass and food wastes/residues to produce biogas has become one of the most attractive routes for producing renewable energy. Biogas mainly consists of methane (CH4, 40-75 vol.%) and carbon dioxide (CO2, ca. 25-60 vol.%). To enable the maximum utilisation of biogas, CO2 removal is necessary. Therefore, this project developed a novel integrated membrane-catalytic process for biogas upgrading, which consists of a membrane separation technology (to capture the CO2 from biogas) coupled with non-thermal plasma (NTP) activated catalysis (to convert the captured CO2 into CH4), enabling methane enrichment. The development of the individual processes was undertaken first. Specifically, a new method was developed to modify SAPO-34 zeolite membrane (using nanoporous organosilica) to heal of the membrane defects, and the developed membrane unit showed an improved CO2/CH4 selectivity (from ca. 60 to 160) without compromising the CO2 permeance. Then, the development of highly efficient catalysts (based on zeolites and MOFs) for the NTP-catalysis system was performed for CO2 hydrogenation. For example, under NTP at 6 kV, the Ni (15 wt.%) supported on UiO-66 MOF catalyst showed a good CO2 conversion (ca. 80%) and CH4 selectivity (ca. 99%). In addition, in situ techniques, such as diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) characterisation, and kinetic studies were carried out to investigate the mechanism of the NTP-catalysis based on the CO2 hydrogenation reaction. At the laboratory scale, the integration of membrane separation with NTP-catalysis was successfully achieved to realise the CH4 enrichment of synthetic biogas. The integrated system showed satisfactory carbon capture efficiency (CCE) and carbon utilisation efficiency (CUE) of ca. 91.8% and 71.7%, respectively, as well as the good stability (40 h).

Date of Award	31 Dec 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Xiaolei Fan (Supervisor) & Chris Hardacre (Supervisor)