Study On The Preparation And Denitration Properties Of Honeycomb SCR Catalyst

Nitrogen oxides is one of the most serious atmosphere pollutants, it is not only the key cause of acid rain, but the fundamental components of the photochemical smog, which heavily destroy our living environment, and which is the current domestic and international extremely attention and urgent hot issue. According to its treating methods, SCR (Selective Catalytic Reduction) technology is considered the most effective one, and Catalyst is the core of the SCR system, which is accounting for 20 to 30 percent of the cost. At present, SCR catalyst production technology mainly mastered by some developed countries, and SCR catalyst technologies have modification and improvement in many areas, so the study with independent intellectual property rights, high efficient, low cost of SCR denitration catalyst has very important practical significance.In this article, we use nano TiO₂ as the carrier, V₂O₅ and WO₃ as the active components, supplemented by adhesive, extruding-aid additive, pore-enlarging additive and reinforcing agent and other substances, by extrusion technology, the honeycomb SCR DeNOx catalysts were prepared. Using SEM, EDS, XRD, BET, TG-DSC and Strength Tester and other methods, the catalyst surface morphology, elemental composition, crystal structure, surface area, weight loss and compressive strength properties were characterized; finally, the catalyst's denitration efficiency was measured in the self-built test equipment.In the molding process of honeycomb SCR catalyst, powder ratio, the addition and type of adhesive, textruding-aid additive and reinforcing agent have a great influence on molding properties of the catalysts. When the water content is 18²7%, the amount of a3 is 1²%, b and c is 0.003ml/g, d is 2⁶%, e is 1²%, the best performance plastic molding paste was prepared.The drying process directly affects the yield of the catalyst, if drying is too fast, the water evaporation rate inside will be different from surface of the catalyst, which will lead to cracking of the catalyst surface; if too slow, resulted in excessive energy consumption, so stop the catalyst surface from excessive water evaporating that can reduce the probability of surface cracking. Using 10mm thick sponge wrapped the catalyst, wrapped it again with cardboard, and then dried for 12 hours in the oven at 60℃after dried for 24 hours in room temperature , the catalyst prepared has a good performance.Calcination is another very important process which is mainly controlled by the heating rate, cooling rate, the furnace pressure and maximum temperature and other factors. Here, the DSC-TG was used to study the roasting process of the catalyst. The optimal method was that roasted the honeycomb catalyst in the muffle furnace at 450℃for 1 hour, 550℃for 2, and then at 600℃for 1. Through studies on influence of reaction temperature, space velocity (SV), NO concentration, O₂ concentration, ammonia ratio (NH₃/NO) and calcination temperature on the denitrification performance of the catalyst, we concluded that reaction temperature, SV, NH₃/NO, calcination temperature have a greater impact on the denitration efficiency of the catalyst, while the concentration of O₂, NO concentration have less impact on the efficiency. In the range of 200³20℃, with temperature increasing, the denitrification rate increased rapidly, rising to about 350℃reaches the maximum, and when it gets to 360℃, the denitrification rate declined as the temperature increases; Under the same temperature, the denitrification rate decreases as the SV increases; NO removal rate increases with the NH₃/NO ratio increasing, when it is less than 1, the effect is more obvious than when it is more than 1, NO conversion rate is almost unchanged; O₂ concentration and NO concentration both have little impact on the denitrification efficiency of the catalyst; but the calcination temperature has a greater influence on the denitration efficiency. when it is higher than 600℃, the denitrification efficiency will be significantly decreased.When SV=3500h-1, t=350℃, n(NH₃/NO)=1, n(NO)=1000ppm, the oxygen concentration is 5%, the denitration efficiency of honeycomb SCR catalyst could reach 95% and the mechanical strength is over 1.1MPa,which reached industrial use requirement.