Basic Research, Based On Ultrasonic Cavitation And Low-temperature Vanadium Catalyst Preparation

The importance of catalyst under low temperature used in sulphuric acid manufacture and the necessity to develop vanadium catalysts with high activity under low temperature has been discussed. Based on the composition of SI07 and SI08 catalysts, orthometric experiments were made with three factors w(V2O5), n(K)/n(V) and n(Na)/n(V).With w(V2O5)=6.3%, n(K)/n(V)=2.7 and n(Na)/n(V)=2.2, the so-called vanadium catalyst TT, presented an optimal activity. Its activity reached to 44.8% at 410℃ and exceeded the ministry standard of vanadium catalysts by 9.8%,Based on catalyst TS, the effect of ultrasonic cavitation on the low-temperature activity of vanadium catalysts was investigated under ultrasonic cleaner. It was found that the effect related to the power of ultrasonic generator, the treating time of ultrasound, the temperature of wet material and the content of water in material. In the SB2200- type ultrasonic cleaner, it took 20 minutes to produce obvious ultrasonic cavitation in wet material. When the same wet material was treated in SB3200-type ultrasonic cleaner with higher power, the time needed to produce ultrasonic cavitation reduced from 20 minutes to 10 minutes. 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. It was also observed that, with the existence of ultrasonic cavitation, the mechanical, thermodynamic and chemical function of ultrasound also had promoting effect on catalytic activity at the same time. It was observed that ultrasonic cavitation enhanced the catalytic activity under low temperature, then the catalyst presented a certain activity at 350℃ .With the use of ultrasound, the catalyst MB was prepared. Its activity reached to 4.2% at 350℃ and 52.5% at410℃.The progress in deactivation that the activity of vanadium catalysts decreased suddenly below 410℃ ~440℃ was summarized, which resulted from low-value vanadium compound separating out from vanadium catalysts. The method to calculate the availabity of inner surface of column-type vanadium catalysts was given. Combined with EopecKOB microcosmic kinetic equation, the macroscopic kinetic equation of column-type vanadium catalysts under low temperature was deduced. With outer-heated fixed-bed integral reactor andunder the condition of temperature 350℃ ~410℃, space velocity 1800 h-1 -5000 h-1,SO2 inlet concentration 7% - 12%, the macroscopic data of the reaction of SO2 oxidation on MI vanadium catalyst were determined. Then the parameters of model equation were estimated. The equation was finally obtained as follows:The intensity and the differential thermal analysis of catalyst MI was determined. It was showed that its axial intensity was 39. 6N and radial intensity was 38. IN. Its differential thermal analysis curve showed that there existed obvious endothermic peak at 348. 86℃, which proved that active components began to melt.