Summary:In the present work, using the catalysts used in the long run activity tests, the deposits of the carbonaceous materials, vanadium and nickel on the catalyst beds or on the surface of the catalyst particles was investigated. From the experimental results, the following conclusions were obtained.(1) In the early stage of the formation of the deposits, the amount of deposits was dependent on the temperature distribution inside the reactor. However, with the progress of reaction time, the amount was apt to increase more in the lower part of the catalyst bed rather than in the upper part. The average amount of the deposited carbon became constant after 100 hours on stream and the increase afterward was not recognised. The average amount varied with the kinds of the catalysts and the amount of asphaltene contained in the feed oil.(2) Though varied with the catalyst, vanadium deposited more in the upper part of the catalyst bed and less in the lower part. The activation energy of the vanadium was about 10kcal/mol. (3) Through nickel is similar in behavior to vanadium which tends to deposit more in the upper part and less in the lower part, it spreads out more widely on the whole catalyst bed.(4) On the catalysts of smaller mean pore diameter, the vanadium deposited in little amount, thinly but densely on the surface. While, on the catalysts of larger mean pore diameter, it deposited in large amount, but sparsely on the surface, and deeply as far as the considerably inner part. Nickel, like vanadium, deposited in much amount and spread to as far as the considerably deep inner part of the catalyst particles. Carbon deposited inside of cracks or holes which had been supposedly produced during preparation of the catalyst.
Summary:The catalysts used for the long run activity tests of hydrodesulfurization reaction of the residual fuel were regenerated by burning with air. Physical properties and the desulfurization activity of the regenerated catalysts were studied. From the experimental results, the following conclusions were obtained. 1) The specific surface area of the catalysts used for the long run activity tests decreased to 40 % of the original value of the fresh catalysts. The specific surface area after regeneration recovered up to 50% in the upper part of the catalyst bed and about 70% in the lower part. The specific surface area of the catalysts after about 100 hours on stream was almost completely regenerated. The pore volume also varied in proportion to the degree of recovery of the specific surface area. The mean pore diameter became greater than that of the fresh catalyst by regeneration.2) The pore size distribution varied remarkably during the 100 hours on stream from the start, and after which it maintained almost the same distribution. Pores were plugged up by the deposited carbon and metals on the surface of the catalyst. Sites of the plugged up pores were considered to be different with different catalysts. The pore size distribution recovered more at the upper part of the catalyst bed than at the lower part after regeneration. 3) When the decrease in the catalyst activity was caused by the deposited carbon, the major part of the activity was recovered after regeneration. However, when the decrease in the activity was due to the deposited metals like vanadium etc., the activity was not recovered, since the metals could not be removed by regeneration.
Summary:Experiments were carried out on the reactions of four heptane isomers, four octane and 60kg/cm2 hydrogen pressure, in order to have a better understanding of the reactions. Reaction products were analyzed by means of a gas chromatographic unit. Reaction rate and selectivity were studied at low conversion levels with the following results:(1) Paraffinic hydrocarbons with higher number of branches were converted faster than did those with lower number of branches;(2) Isomerization reaction of a paraffin molecule to others with the same number of branches were very fast;(3) Hydrocracking reactions were very slow compared with isomerization reactions except for trimethylpentanes;(4) Decyclization reactions of methylcyclopentane and methylcyclohexane were very slow. Discussed were the reaction path and mechanism, and it was suggested that tertiary carbonium ions are more reactive than secondary ones and far more reactive than primary carbonium ions because of the higher rate of adsorption of olefins to form tertiary carbonium ions, the higher concentration of tertiary carbonium ions on acidic sites, and the higher rate of desorption of the tertiary carbonium ions.
Summary:The control methods of pore properties of catalyst supports and the manufacturing methods of their desirable pore size distribution for hydrodesulfurization catalyst of residual and calcination condition of alumina hydrates, especially boehmite gel, were investigated. From the experimental results, the following were obtained. 1) With higher hydrolysis temperature, the crystallites became larger, the spec fic surface area period of boehmite gel was prolonged, the degree of crystallinil), advanced along with the crystal growth of bayerite and consequently, the specific surface area and the pore volume decreased. 2) When the alumina hydrates were washed in water, the pore volume and the specific surface area decreased. When they were washed in alcohol, the pore volume and the specific surface area increased on the contrary. 3) As the calcination temperature was raised higher, the specific surface area decreased and, in reverse, the pore volume increased. 4) The most important effect on the pore structure of the alumina as catalyst support was the permeation of alcohols into the interstice of crystallites of alumina. Also, selecting the preparation conditions of alumina hydrates adequately, the diameter of crystallites could be changed markedly and, consequently, the pore structure could be controlled. 5) When the suitable kind of acid was added to alumina hydrates and they were calcined to make alumina supports, the specific surface area was constant independent of the acid concentration, while the pore volume and the mean pore diameter decreased according to increase of the acid cotcentration.
Summary:In connection with hydrodesulfurization catalysts for residual fuel, correlations between physical properties and desulfurization activity of the catalysts, were studied. From the experimental results, the following conclusions were obtained.less crystallity showed high desulfurization activity.(2) Independent of the manufacturing methods of catalysts, the removal of vanadium and nickel was almost proportional to sulfur removal.(3) The desulfurization activity of catalysts in their early reaction stage was high in proportion to their acidity.(4) Correlations between desulfurization activity and such physical properties as specific surface area, pore volume, apparent bulk density, mean pore diameter and pore size distribution, etc., were investigated by regression analysis. In consequence, it was found that the catalysts which had a large pore volume, low apparent bulk density, large mean pore diameter and pore size distribution, which was abundant in the pore dia-1 Introduction
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