Silica supported transition metal phosphides- Alternative materials for the water-gas shift reaction

QD Chemistry

Hughes, Matt ; Hargreaves, J.S.J.

University:University of Glasgow

Department:School of Chemistry

关键词: Materials,Surfaces science, Catalysis, Inorganic chemistry, Water-gas shift reaction, Nickel phosphide;   

Others  :  http://theses.gla.ac.uk/5548/1/2014HughesPhD.pdf

来源: University of Glasgow

【 摘 要 】

Transition metal phosphides remain relatively unexplored as water-gas shift catalysts; however the little that has been done has produced promising results in terms of performance due to the presence of oxygen rich phases. They can be produced through a number of approaches, the most common being reduction of the phosphate precursor using hydrogen. Bimetallic phosphides have also generated interest recently, e.g. with the addition of cerium there are improvements to the phosphides' activity and with the addition of palladium a decrease in reduction temperature is evident in the precursor material. Nickel phosphide and a range of bimetallic derivatives on a silica support were investigated for their activity in both high and low temperature water-gas shift reactions. All of the catalysts were tested using a continuous flow, fixed bed reactor. Characterization of the catalysts was carried out using XRD, EXAFS, XPS, FTIR, SEM and TEM. The comparison of supported nickel phosphide and an iron based industrial catalyst shows supported nickel phosphide to have good mass normalized activity in comparison to the industrial counterpart under high temperature water-gas shift conditions. The results complement previous studies with regards to potential of nickel phosphide as a water-gas shift catalyst. In view of the results obtained so far for other transition metal phosphides, Ni2P appears to be superior for the water-gas shift reaction. One of the most promising aspects of using nickel phosphide in the water-gas shift reaction is its potential resistance to sulfur. Catalyst poisoning caused by impurities such as sulfur are known to deactivate current commercial catalysts for both high and low temperature shift conditions, therefore a catalyst which is resistant to sulfur is an attractive prospect. The sulfur resistant properties of the nickel phosphide catalysts were highlighted by testing them under high temperature water-gas shift conditions in the presence of sulfur. Whilst the catalysts deactivated under the conditions, they showed some residual catalytic activity still remained after sulfur was removed from the feed. Compared with the industrial catalyst, nickel phosphide displayed greater resistance to deactivation.