(582an) Assembly of Kaolin and SAPO-34 Catalyst Using Silica Sol As Binder By Spray Drying for Conversion of Methanol to Light Olefins in Fluidized Bed Reactor: Effect of Ion Exchange Method

Light olefins are of most important intermediates in organic chemical process and are essential feedstocks in petrochemical industry, which are generally produced through thermal and catalytic cracking. High reaction temperature, low yield and dependency to oil sources are of drawbacks of those methods. Catalytic methanol-to-olefins (MTO) can be an alternative. The availability of huge quantities of natural gas and other non-oil sources for methanol production such as coal, biomass and industrial waste has led to an increased interest in the MTO process. SAPO-34 as a novel molecular sieve with CHA structure has the best catalytic performance in methanol-to-olefin (MTO) reaction due to the contribution of small pore, medium acidity, shape selectivity, high surface area and good thermal/hydrothermal stability. However, rapid deactivation and short lifetime are challenges for SAPO-34 catalysts. To overcome these drawbacks, fluidized bed reactor was suggested by consideration of reactor design principles. It provides the possibility of catalyst regeneration. In this study, the successful synthesis of kaolin-bound SAPO-34 catalyst by using silica sol was achieved. The used silica sol during the slurry preparation was derived from sodium silicate. The Na⁺ ion in the binder lead to the formation of catalyst with almost no activity in MTO reaction. Thus, ion exchange stage should be considered when sodium silicate is the desired Si sol precursor due to its low price. Slurries with constant ratios of SAPO-34 catalysts, kaolin (as matrix) and silica sol (as binder) were subjected to the spray dryer at constant operational conditions. Two different methods of ion exchange, using ammonium nitrate and resin, were applied after spray dring for Na⁺ ions exchange with H⁺. Different physiochemical characterization methods including XRD, FESEM, BET, NH₃-TPD and FTIR techniques were applied. At first, the catalysts activities were examined in a fixed bed reactor and then the catalyst with the best performance in MTO reaction was used in fluidized bed reactor. Using acid cation exchanger caused the successful removal of Na⁺ ions. The result of XRD analysis demonstrates appearing of corresponding peaks of SAPO-34 with the most intensity for the sample in which ion exchange resin was applied. Using ammonium nitrate to exchange Na⁺ ions could not completely lead to H⁺ ions substitution. Catalyst life times increased when sprayed spherical particles were subjected to ion exchange resin bed.