Volume 197, 2017

The effect of sodium species on methanol synthesis and water–gas shift Cu/ZnO catalysts: utilising high purity zincian georgeite

Abstract

The effect of sodium species on the physical and catalytic properties of Cu/ZnO catalysts derived from zincian georgeite has been investigated. Catalysts prepared with <100 ppm to 2.1 wt% Na+, using a supercritical CO2 antisolvent technique, were characterised and tested for the low temperature water–gas shift reaction and also CO2 hydrogenation to methanol. It was found that zincian georgeite catalyst precursor stability was dependent on the Na+ concentration, with the 2.1 wt% Na+-containing sample uncontrollably ageing to malachite and sodium zinc carbonate. Samples with lower Na+ contents (<100–2500 ppm) remained as the amorphous zincian georgeite phase, which on calcination and reduction resulted in similar CuO/Cu particle sizes and Cu surface areas. The aged 2.1 wt% Na+ containing sample, after calcination and reduction, was found to comprise of larger CuO crystallites and a lower Cu surface area. However, calcination of the high Na+ sample immediately after precipitation (before ageing) resulted in a comparable CuO/Cu particle size to the lower (<100–2500 ppm) Na+ containing samples, but with a lower Cu surface area, which indicates that Na+ species block Cu sites. Activity of the catalysts for the water–gas shift reaction and methanol yields in the methanol synthesis reaction correlated with Na+ content, suggesting that Na+ directly poisons the catalyst. In situ XRD analysis showed that the ZnO crystallite size and consequently Cu crystallite size increased dramatically in the presence of water in a syn-gas reaction mixture, showing that stabilisation of nanocrystalline ZnO is required. Sodium species have a moderate effect on ZnO and Cu crystallite growth rate, with lower Na+ content resulting in slightly reduced rates of growth under reaction conditions.

Associated articles

Article information

Article type
Paper
Submitted
03 Oct 2016
Accepted
24 Oct 2016
First published
24 Oct 2016
This article is Open Access
Creative Commons BY license

Faraday Discuss., 2017,197, 287-307

The effect of sodium species on methanol synthesis and water–gas shift Cu/ZnO catalysts: utilising high purity zincian georgeite

S. A. Kondrat, P. J. Smith, J. H. Carter, J. S. Hayward, G. J. Pudge, G. Shaw, M. S. Spencer, J. K. Bartley, S. H. Taylor and G. J. Hutchings, Faraday Discuss., 2017, 197, 287 DOI: 10.1039/C6FD00202A

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements