On validating the hypothetical activity of hexameric copper

On validating the hypothetical activity of hexameric copper nanocluster catalysts in a CO conversion reaction (CO oxidation) Luqmanulhakim Baharudina (luqmanulhakim. baharudin@pg. canterbury. ac. nz), A. C. K. Yipa, V. B. Golovkob & a M. J. Watson a. Department of Chemical and Process Engineering (CAPE), University of Canterbury, Christchurch, New Zealand b. School of Physical and Chemical Sciences, University of Canterbury, Christchurch, New Zealand BACKGROUND Research gap: Studies on interaction of CO molecules with transitional metal clusters (size range of 3 to beyond 20 atoms) in quantum chemistry did not take into account the behaviour of the interaction in the system where clusters are deposited on support materials [1]. Synthesized materials: Novel materials made of hexameric copper clusters (Cu 6) (Fig. 1 (L)), supported on pristine and carboxyl-functionalized multi-walled carbon nanotubes (MWCNTraw and MWCNTCOOH) (Fig. 1 (R)). RESULTS & DISCUSSION Fig. 1: Left: Cu 6 cluster determined by single-crystal XRD; Right: Carboxyl-functionalized MWCNT Objective: To study CO interaction with the active site on supported Cu 6 nanocluster catalysts by CO temperature-programmed desorption (CO-TPD) and interpret the active site characterization by experimental validation in CO oxidation reaction. Active site characterization: BELCAT II Catalyst Analyzer (Microtac. BEL) (Fig. 2) located at CAPE lab was used to study the interaction of CO with the supported Cu 6 using CO-TPD technique [2]. Fig. 2: BELCAT analyzer for CO-TPD Experimental validation: CO interaction with the active site determined by CO-TPD was validated in actual activity tests in a differential reactor (Fig. 3) on the synthesized materials in CO oxidation reaction. Fig. 3: Experimental rig for CO oxidation CONCLUSIONS CO-TPD technique by BELCAT analyzer complements the experimental analysis of supported Cu 6 nanocluster catalytic behaviours, aiding in understanding the elementary steps involved in CO oxidation mechanism. Fig. 4: Activity behaviour of support materials in CO oxidation Fig. 5: Activity behaviour of supported Cu 6 catalysts in CO oxidation Langmuir-Hinshelwood Mechanism Dissociative adsorption of O 2 (g) from feed gas: O 2 (g) + 2* 2 O* Adsorption of CO (g) from feed gas: CO (g) + * CO* Surface reaction between adsorbed CO* and adsorbed dissociated oxygen O*: CO* + O* CO 2* + * Desorption of CO 2* from vacant site into CO 2 (g) product gas: CO 2* CO 2 (g) + * Fig. 6: Non-dissociated oxygen adsorbed on active site blocks CO molecules, limiting the CO conversion to progress REFERENCES [1] Fielicke et al. (2009). The adsorption of CO on transition metal clusters, : A case study of cluster surface chemistry, Surface Science (603), 1427 -1433. [2] Baharudin et al. (2018). CO-TPD of a Cu 6 nanocluster catalyst supported on MWCNTs for active site characterization in a LTWGS reaction, Chem. Eng. J. , aip.