Study on the Hydrodesulfurization Catalyst of Residual Fuel (Part 4): Improvement of Catalyst Support

The control methods of pore properties of catalyst supports and the manufacturing methods of their desirable pore size distribution for hydrodesulfurization catalyst of residual fuel were studied. Namely, the correlations between pore properties of γ-alunzina and preparation 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 specific surface area decreased and the pore volume of the pore having diameter less than 600Å increased. When aging period of boehmite gel was prolonged, the degree of crystallinity 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.