Synthesis of monometallic macrostructured catalysts for bromate reduction in a continuous catalytic system

ABSTRACT

The last few years have seen great leaps in the use of mechano-chemically modified carbon nanotubes in catalysis. While high improvements in catalytic performance have been achieved, the nature of the technique is not compatible with typical strategies for CNT coating of macro-structured catalysts by chemical vapour deposition. Developing macro-structured catalysts is a key step towards the sustainability of multi-phase catalysis and requires a methodology for coating with mechano-chemical modified CNT metallic catalysts. Preparing water-based slurries is not straightforward due to the CNT’s hydrophobicity, and the use of organic solvents is unsustainable. A novel methodology for the washcoating of macro-structures with pre-modified monometallic CNT catalysts was assessed. A compromise between surfactant use, post-coating treatment, and the catalyst activity/integrity, was achieved by solubilization of the surfactant in a isopropanol:acetone mixture. The activity of the prepared catalysts was affected by the metallic dispersion, surfactant coverage, and distribution of the palladium throughout the catalytic layer. Palladium centres in the bottommost layers were found to be unavailable for liquid phase reaction. The activity of the catalysts prepared with pre-formed carbon monometallic powders was improved by adopting a coating strategy to maximize the availability of the metallic particles near the surface of the catalytic layer.

GRAPHICAL ABSTRACT

KEYWORDS:

• Bromate conversion
• catalytic reduction
• structured catalysts
• washcoating
• Metal distribution

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data that support the findings of this study are available from the corresponding author, [OSGPS], upon request.

Additional information

Funding

This research was financially supported by InTreat-PTDC/EAM-AMB/31337/2017 – POCI-01-0145-FEDER-031337-funded by FEDER funds through COMPETE2020-Programa Operacional Competitividade e Internacionalização (POCI) and by national funds (PIDDAC) through FCT/MCTES and by NanoCatRed (NORTE-01-0247-FEDER-045925) co-financed by the ERDF – European Regional Development Fund through the Operation Program for Competitiveness and Internationalisation – COMPETE 2020, the North Portugal Regional Operational Program – NORTE 2020 and by the Portuguese Foundation for Science and Technology – FCT under UT Austin Portugal; LA/P/0045/2020 (ALiCE), UIDB/50020/2020 and UIDP/50020/2020 (LSRE-LCM), funded by national funds through FCT/MCTES (PIDDAC). C.A.O. acknowledges FCT funding under DL57/2016 Transitory Norm Programme. O.S.G.P.S. acknowledges FCT funding under the Scientific Employment Stimulus – Institutional Call CEECINST/00049/2018. A.S.G.G.S acknowledges FCT funding under reference UI/BD/151093/2021.