Nisapo-101 And Fesapo-101 Zeolite Synthesis And Characterization

As a third generation of new molecular sieves, MeSAPO with good thermal stability and hydrothermal stability can be used as catalysts or catalyst carriers, particularly in the development of methanol to olefins (MTO) process, are playing an important role. The present works were applied to synthesize a novel class of silicoaluminophsphate molecular sieves by hydrothermal crystallization employing diethylene-triamine (DETA) as template, phosphoric acid, nano-aluminum hydroxide, ethyl orthosilicate, nickel sulfate and ammonium ferrous sulfate were used in the syntheses as raw materials.The main research contents and conclusions are as follows:Firstly, by adjusting the crystallization time, crystallization temperature, pH value and the raw material ratio, high crystalline MeSAPO-101(Me= Ni or Fe) molecular sieve have been synthesized under the traditional hydrothermal condition, with diethylene-triamine (DETA) as the template, orthophosphoric acid, tetraethyl orthosilicate, nickel sulfate, ammonium ferrous sulfate and namo-aluminum hydroxide as raw materials. The optimum molar ratios of raw materials are n(P): n(Si): n(H2O):n(Ni):n(Al): n(DETA)= 1:0.11:82:0.38:0.49:82:0.89 and n(P): n(Si): n(H2O): n(Fe): n(A1):n(DETA)= 1:0.67:82:0.13:0.21:82:0.78, respectively. NiSAPO-101 molecular sieve have been synthesized with crystallization temperature at 210℃, pH value at 6.8 and crystallization time for 24 h; FeSAPO-101 molecular sieve have been synthesized with crystallization temperature at 190℃, pH value at 8.0 and crystallization time for 24 h.Secondly, elemental analysis indicates that the percentage composition (wt%) of N, C, H, P, Si, Al, and Ni are 7.64%,8.65%,2.72%,13.69%,3.57%,3.57%and 16.57%, the percentage content(wt%) of N, C, H, P, Si, Al, and Fe are N 7.87 wt%, C 8.99 wt%, H 2.81 wt%, P 13.78 wt%, Si 3.29 wt%, Al 10.10 wt%, Fe 15.69 wt%, respectively.Thirdly, the results of SEM and XRD analyses indicated that the synthetic products have high purity, crystallinity and large crystal size. Meanwhile, according to the literatures, the synthetic molecular sieves belong to rhombohedral system, space group R-3.Fourthly, the analysis of DTA-TG showed that the compounds have good thermal stability. The surface acidity of molecular sieves were studied by temperature programmed desorption, the results indicateded that these two kinds of metallic molecular sieves have weak surface acidity.Fifthly, using the synthetic molecular sieve as catalyst in MTO process, the methanol conversion rate exceeds 90 wt%, the product distribution is much concentrated in light olefins, under the optimum conditions, the selectivity of ethylene and propylene are about 70 wt% and 15-30 wt%, respectively, the sum is about 91 wt%. All these explain that the synthetic molecular sieves are potential catalyst for MTO process.