A New Structured Vanadium Catalyst And Its Design, Manufacture And Tests

Structured vanadium catalysts (SVC) is a novel catalysts designed for solving the problems including high pressure drop and high energy consuming in sulfuric acid production. Its inner regular cross channels endow SVC with attractive properties such as low friction resistance and high mass and heat transfers. SVC was prepared with diatomite as a carrier. Channels were obtained by using plastic shape template. The final product of SVC was manufactured to be a cubic appearance with reticular channels inside.A moulding compressing method was used to manufacture SVC, which is different from the shaping method for commercial random catalysts. The quality of SVC greatly depends on the properties of moulding slurry. The influence of slurry dosage and processing conditions on the flow behavior of the casting catalyst slurry was investigated. The relationship between the flow behavior of slurry and the mechanic strength was discussed in detail. The results show that the fluidity of catalyst slurry can be improved by acid processing, lowering pH value, kneading, adding lubricant additives, etc. The slurry processing makes it possible to use low water content in the shaping process of catalyst. The SVC prepared has less cracks and shows a high mechanic strength.The manufacture process of SVC includes three steps, stuffing, compressing and demoulding. Plastic templates obviously influence the shaping process. Bymeasuring the influence of different methods on these steps, the variation tendency of compactness and density were determined and the catalytic body's density model is established. The results show that kneading and aging can efficiently decrease the viscosity of vanadium catalyst's slurry. The feasible way to compress SVC is multiple stuffing and pressing. Plastic shape templates decreased single stuffing height and body's compactness of SVC seriously.Polypropylene was chosen to be the material of plastic shape templates. Thermal treatment program was completely different because of the exist of the plastic inside SVC. By measuring the thermal properties, such as heated expansion rate, TG and DTA, the co-pyrogenation effect caused by plastic on vanadium catalyst is observed and researched. The results show that the drying time should be no less than 10 hours according to drying profile. The heating rate in calcining should be limited under 15℃/h in 300-400℃ to avoid the sharp expansion of plastic destroys the subtle inner structure of catalysts. The introduction of plastic did not affect the catalysts' chemical properties, especially catalysis activity.Mechanic strength is the most important property of SVC. Vanadium catalysts is fragile material and easy to block the bed after being crushed. By screening commercial catalyst recipes, the recipe of commercial S105 vanadium catalyst for SO2 conversion, which showed the highest mechanical strength, was selected to be a basic recipe. Manufacture parameters, such as shaping pressure, moisture, pH value, kneading condition, age time, etc., were tested. Graphite, glass fiber and high temperature binder were also employed as additives to improve the mechanical strength of the catalyst material. Under an optimal manufacture condition, the mechanical strength of the material prepared is 4-5 times higher than that of the commercial S105 catalyst. Mechanic strength reliability increased satisfied.Inner structures of SVC may decrease its mechanic strength. The inner channel to whole strength was simulated by an analogy calculating by using finite element method. Results show that inner structure of SVC causes the strength reducing to 20% of vanadium catalyst materials, which agrees with experimental data. A strain-stress equation of SVC is established. Based on this equation, the mechanicfailure press is about 1.33 MPa, hydraulic failure pressure is 1.19MPa.Activity, pressure drop and external mass transfer of SVC were measured respectively. Results show that the structure of SVC can increase the effectiveness of vanadium catalysts. The pressure drop of a SVC bed is only 1/2-1...