| The importance of catalyst used for sulfuric acid under low temperature and the necessity to prepare catalyst with high activity under low temperature has been discussed.The promotional effects of carbonized mother liquor containing alkali-metal elements (that is K,Na,Cs,Rb,Li) on vanadium catalysts under low temperature have been investigated. The result showed that when the quantity of the carbonized mother liquor had been added according to nK/nv=3.0, the conversion of 862 on catalyst prepared directly with carbonized mother liquor could reach to 24.8% at 410 ℃. If the ratio of nNalnv was adjusted to 1.5, the conversion of SO2 could increased to 35.6%at the same temperature. The effects of Cs, Rb and Li on catalytic activity have been investigated. The results showed that Cesium was the best promoter and the suitablenC5|nv was 0.3-0.6. When nC5|ny=0.6, the conversion ofSOa increased to 42.5% under 410℃. Because the effect of Rubidium on activity of sulfuric acid catalyst under low temperature was neglectable, Rubidium should be separated from carbonized mother liquor so as to make full use of valuable elements. Lithium had a good effect on activity of catalyst, its optimum nL1/nv was 0.4 andthen the conversion of SO2 was 46% under 410℃. Furthermore, if the content of active components was excessive, the activity of catalyst under low temperature would reduce on the contrary and the suitable nM /ny was 4.5.So carbonized mother liquor was refined. Based on the refined liquid B, catalyst Ls was prepared. Its activity under 410℃ was as high as 37.1%. The differential thermal analyses of catalyst indicated that both endothermic apices and exothermic apices of catalyst shifted forward obviously and it indicated that the catalyst possessed high activity at low temperature.Based on catalyst Ls, the effect of ultrasonic cavitation on the low-temperature activity of catalysts has been investigated. In the SB2200- type ultrasonic cleaner, it took 20 minutes to produce obvious ultrasonic cavitation. When it was treated in SB3200-type ultrasonic cleaner, only 10 minutes would be needed. The higher the temperature of wet material, the less time was needed to produce ultrasonic cavitation and the optimal temperature was 60℃.The content of water in wet material mainly affected the quantity of ultrasonic cavitation. With the use of ultrasound, the catalyst Ls-8 was prepared. Its activity reached to 52.5% at 410℃and 4.2% at 350℃.Plasma technology was used to prepare catalyst Ls-9. The results showed that with the use of plasma, the activation time was shorten sharply and the activity of catalyst was improved to some extent.Differential thermal analysis had been used to investigate the reason why the activity of catalyst was so high. It was found that there existed obvious endothermic peak at 283 ,which proved that active components began to melt. The axial intensity of catalyst Ls-9 was 49.8N and radial intensity was 50.3N.The measure of surface fractal dimension of catalyst indicated that with the use of ultrasound and plasma, the surface fractal dimension could be increased.A three-step reaction mechanism for S2 oxidation on Ls-9 catalyst was proposed and a intrinsic kinetic equation was derived as follow:The intrinsic kinetic data was measured with a non-gradient reactor and the parameters of model equations were calculated in the range of 380~520C by Powell-62073 -2384 -18949non-linear regression method:,=0.152 KT ,A:2=8.18e Kr , K3=0.22le " .The method to calculate the availabity of inner surface of column-type catalyst Ls-9 was given. Combined with three-step reaction mechanism intrinsic kinetic equation, the macroscopic kinetic equation was deduced:,b, 0~) ^ so,,s eff, With outer-heated fixed-bed integral reactor and under the condition of temperature 350~410, space velocity I800'-'500h"1, SO2 inlet concentration 7 12%, the macroscopic kinetic data were determined. Finally, the equation was obtained as follow:...
|
PDF Full Text Request