Zirconia based supports for rhodium for automotive-catalytic reaction

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Burton, I., 2001. Zirconia based supports for rhodium for automotive-catalytic reaction. PhD, Nottingham Trent University.

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Abstract

Of the many factors investigated, the temperature of calcination and the ratio of ceria : zirconia in the bulk are the main variables that influence the character of the ceria / zirconia mixed oxide, when prepared by the coprecipitation route. The Plackett- Burman statistical approach used allows for a number of conclusions to be drawn. These include that mixed oxides calcined at 500°C have a surface area 85 m2g-1 greater than those calcined at 900°C and reduce at a temperature 50°C lower. The use of the approach in preparing an 'optimised' catalyst has limited success.

Ternary additives, praseodymia, neodymia, lanthana and yttria, significantly influence the character ceria / zirconia mixed oxide. Ternaries at levels of 10 mol%, rather than at 3 mol%, offer greater stabilisation of surface area, the enhancement of which is greatest with lanthana and worst with yttria and this can be related to ionic radius.

As a support for rhodium, high temperature calcined supports significantly aid the catalyst in performing the CO-NO reaction. A ceria rich surface, high surface area and the addition of a ternary rare earth oxide into the support are also beneficial to the activity and selectivity of the catalyst. For N2O decomposition, the surface area of the support, and hence the manner in which rhodium is supported on it, is directly related to catalytic activity.

The presence of rhodium species stabilises the surface area of tetragonal zirconia, when prepared as a lwt% Rh / ZrO2 mixed oxide by coprecipitation, and decreases the extent of the tetragonal to monoclinic phase transformation. Surface enrichment of rhodium under high temperature treatment improves the catalytic activity for N2O decomposition.

The AlPO-5 structure is much less effective a vehicle for copper for the SCR of NO by propene than ZSM-5. The activity of each copper unit is much greater in the case of Cu-ZSM-5. The nature of the copper within the AlPO structure is shown to be different due to the mode of preparation and this is important to the catalytic nature of the material. A lwt% Rh / ZrO2 catalyst, when prepared by coprecipitation, is superior to Cu-AlPO in performing the SCR reaction.

Item Type:

Thesis

Creators:

Burton, I.

Date:

2001

ISBN:

9781369316780

Identifiers: