Abstract:
Nickel catalysts find widespread industrial application in hydrogenation,
hydrotreating, and steam reforming reactions. Recently considerable interest
has developed in the application of nickel catalysts for methanation of coal
synthesis gas. Before starting experimental work, extensive literature studies
were carried out on this topic and it was found that despite this widespread
use very little work had been done on the co-precipitated nickel catalyst. The
scope of the work under this project was to study the effect of composition
and calcination temperature on the structure and activity of methanation
catalyst. Nickel catalyst supported by alumina and promoted by chromium
prepared by co-precipitation method was used for this purpose. The whole
work was divided into three groups. These are :
(1) To study the effect of composition on the structure of the catalyst, .
(2) To investigate the effect of composition on the activity of the catalysts, .
and
(3) To assess the effect of calcination temperature on the structure and
activity of the catalysts.
A set of four catalysts of different composition was prepared to study the
effect of composition on structure. Temperature Programmed Reduction
(TPR), Hydrogen Chemisorption and X-ray Diffraction (XRD) methods
were used to study the structure of the catalysts. Methanation reaction was
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carried out on these catalysts to established their suitability for this reaction.
Free NiO, CrZ03 and fixed compounds were found to be present in most of
the catalysts. From XRD patterns it is evident that the position and intensity
of the peaks varied due to different structural orientation.
In the second section of this work, the space velocity of the feed was
increased to assess the effect of composition on the performance of the
prepared catalysts. XRD patterns were used to find out the relationship
between structure and activity. Conversions of carbon oxides varied
inversely with the space velocity. Conversion and selectivity of methanation
reaction did not show any trend with weight loading.
In the third section of this work, one catalyst without promoter was calcined
at different temperatures. The impact of calcination temperature on the
activity and structure was studied. For the same catalyst calcined at different
temperatures, highest conversion (21.87%/gm cat.) was found for the lowest
calcination temperature. The conversion decreased markedly with increasing
temperature. Most of the catalysts showed very good performance in respect
of activity. It has been found that the catalyst preparation variables have.
significant influence on the structure and activity ofthe catalysts.
