During the fellowship, work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far are as follows:
(i) Fabrication of zeolite membranes with controlled thickness
During the fellowship, SAPO-34 membranes supported on tubular porous alumina were developed and applied in the capture of CO2 from biogas, showing high CO2/CH4 selectivity of 160.
(ii) Synergistic effect of NTP enabled Ni- and Ru- based catalysts systems for CO2 mathanation
For the NTP catalysis, three robust catalysts were developed, including Ni supported on zeolite (i.e. Ni/NaBETA) or metal–organic frameworks (MOFs) catalysts (i.e. 15Ni/UiO-66), Ru supported on MgAl layered double hydroxide (i.e. Ru/MgAl). These catalysts were demonstrated to efficiently enable catalytic CO2 methanation activated by NTP at ambient conditions, showing significantly higher CO2 conversions (∼85 %) and CH4 yield (∼84 %) at relatively low temperatures compared with the conventional thermally activated catalysis. Additionally, the NTP activation was successfully applied to enable heterogeneous catalysis over MOFs-based catalysts for catalytic CO2 hydrogenation under mild conditions.
(iii) Catalytic CO2 methanation mechanisms under NTP activation
In situ diffuse reflectance infrared Fourier (DRIFTS) coupled with mass spectrometry (MS) characterization of the catalytic system confirmed the alternative reaction pathways enabled by NTP, enabling the fundamental understanding of the reaction mechanisms. In addition, kinetic studies of the catalytic CO2 methanation over the developed catalysts revealed that the NTP catalysis has a lower activation energy of ~21 kJ mol−1, being significantly lower than that of the thermal catalysis (~82 kJ mol−1).
(iv) process integration for improving process efficiency
Finally, the researcher carried out a proof-of-concept study of a novel integrated process, consisting of a MS followed by a NTPR in tandem, for potential application in the high-efficient capture and utilisation of CO2 towards biogas upgrading. The hybrid MS-NTPR system showed highest carbon capture efficiency (CCE) and carbon utilisation efficiency (CUE) of ca. 91.8% and 71.7%, respectively. In addition, the integrated process also exhibited excellent stability for CCU in the biogas upgrading, i.e. a stable performance over a 40 hr longevity test.
During the fellowship, the researcher has attended several conferences to disseminate the results of the project, including:
1. Chen, H.; Fan, X.; Hardacre, C. High-efficiency process for CO2 capture and utilization. Researcher Links Workshop on Sustainable Systems for CO2 Utilization in China and the UK, Beijing, China, July 2018.
2. Chen, H.; Fan, X.; Hardacre, C. Coupling of non-thermal plasma with BETA zeolite supported Ni catalysts for the methanation of carbon dioxide. UK Catalysis Conference, Loughborough, UK, January 2019.
3. Chen, H.; Fan, X.; Hardacre, C. Coupling of heterogeneous catalysts with non-thermal plasma for CO2 methanation: probing the reaction mechanisms using in-situ DRIFTS. ACS Spring 2019 National Meeting in Orlando, US, March 2019.