Effect of composition and calcination temperature on the activity of steam reforming catalyst

Abstract

The present study deals with the properties of nickel catalysts used for the reaction between steam and hydrocarbon (methane) into mixtures of hydrogen, carbon monoxide and carbon dioxide. Such type of reaction is normally called steam reforming or catalytic steam reforming. In our country steam reforming of methane is very important particularly in fertilizer industries as it is one of the reactions that are involved in ammonia synthesis. The purpose of this paper is to study the physical and chemical properties of reforming catalyst in order to interpret the activity and selectivity of a particular catalyst. In this research work three series of catalysts were prepared using co-precipitation technique and were systematically investigated. The active component of the catalyst was nickel supported by alumina and promoted by chromium/manganese. The samples of the third series were consisted of only nickel and aluminum oxides. The structural orientation of Ni-Cr-AI and Ni-Nn-AI catalytic systems prepared by using different precipitants (KOH/Urea) was assessed on the basis of activity testing data, XRD patterns, TPR results and chemisorption data. The first seriesof samples were used for this study. The second series of samples were prepared to study the effect of composition on the activity of the catalysts by increasing the space velocity of reacting gas since the activity of the samples was as high as 22% per g of catalyst at low space velocity regardless of composition. The calcination temperature of the samples of third series was varied to study the influence of calcination temperature on the activity and XRD pattern. The activity testing gives arbitrary results. Therefore, conversion of the reactants can not be correlated to the active metal loading of the catalysts. The position and intensity variation of the XRD patterns show that the structure and iii crystallinity of each sample varies considerably from the other. The TPR data and chemisorption results show different reduction temperatures and different hydrogen uptakes for different prepared samples. Thus the results of this investigation are in agreement in one point, that is, each sample is unique from structural point of view. Furthermore, the prepared catalyst samples are observed to be consisted of various combination of free NiO, y A1ZO], MnO or chromium oxide of variable valency and a variety of multimetallic compounds. As the calcination temperature increases, the samples become more crystalline and activity as well as stability of the samples increase.