Desulfurization Of Gasoline By Al-MCM-41 Mesoporous Molecular Sieve

With the increasingly stringent environmental regulations worldwide, low-sulfur gasoline production has become highly concerned issue in the refinery industry. Among various methods of non-hydrodesulfurization, the adsorption desulfurization is the most promising technology.This article presents the hydrothermal synthesis of Al-MCM-41 molecular sieve with different Si-Al ratio, and the characterization by XRD, N2 adsorption isotherms. Additionally, the effect of the crystallization time, the method and temperature of calcination on the preparation of molecular sieve was investigated. After the static adsorption experiments, the molecular sieves with outstanding results were modified with metal cations. The investigation of adsorption effects on the desulfurization were focused on Ni, Zn modified molecular sieves, their best preparation conditions and the impacts of aromatics in gasoline were studied. Finally, preliminary study was carried out on bimetal molecular sieve adsorption desulfurization.The results showed that the optimum conditions for preparation of molecular sieves were: sources of aluminum: sodium aluminate,crystallization time: 72h, temperature increasing rate: 2℃/min. From the XRD and N2 adsorption-desorption curves, A1-MCM-41(80) had excellent crystallization, uniform pore distribution, large surface area and narrow pore size distribution. Al-MCM-41(80) molecular sieve had the best adsorption desulfurization capacity. The optimum operating conditions were: adsorption temperature: 80℃, oil-adsorbent ratio: 60:1, adsorption time: 5h, under this condition, the adsorption of sulfur content was 12.3056mgS/g adsorbent.Comparing different metal cations modified Al-MCM-41 (80) molecular sieves and their effects on simulated gasoline desulfurization, the order of the desulfurization capacity of Fe, Ni, Zn, Cu, Co, Ce was: Ni-Al-MCM-41(80)>Co-Al-MCM-41(80)>Zn-Al-MCM-41(80)> Fe-Al-MCM-41(80)>Ce-Al-MCM-41(80)>Cu-Al-MCM-41(80); aromatics reduced the selectivity of thiophene of the molecular sieve, the nickel and zinc loaded Al-MCM-41(80) molecular sieve had the better selectivity.Further study on nickel, zinc loaded molecular sieve showed the best preparation condition for Ni-Al-MCM-41(80) molecular sieve was: nickel nitrate 0.3mol/L, dipping time 24h, calcination temperature of 450℃, reduction temperature of 550℃. The best adsorption of sulfur content was 18.6854mgS/g adsorbent. When the toluene content was 5wt%, the adsorption of sulfur content decreased by 37.64%; after increasing to 10wt%, the adsorption dropped by 48.12%. Regeneration of nitrogen calcination had the best adsorption desulfurization performance. The best preparation condition for Zn-Al-MCM-41 (80) molecular sieve was: zinc nitrate 0.1mol/L, dipping time 24h, calcination temperature of 450℃, then the best adsorption of sulfur content was 15.7958mgS/g adsorbent. When the toluene content was 5wt%, the adsorption of sulfur content decreased by 28.12%; after increasing to 10wt%, the adsorption decreased by 44.51%.Finally for the bimetal molecular sieve Zn-Ni-Al-MCM-41(80), the optimum preparation conditions were: both nickel nitrate, zinc nitrate are 0.1mol/L, dipping time 12h, calcination temperature 450℃, then the adsorption was 17.8958mgS/g adsorbent; when the quantity of toluene was 5wt%, the adsorption of sulfur content decreased by 42.13%; increasing 10wt%, the adsorption decreased by 44.87%.