| At present,environmental problems have become increasingly prominent,and environmental protection has been highly valued by the state.Sulfur compounds in the air mainly come from automobile combustion of diesel oil.98% of exhaust gases such as gasoline and diesel are mainly in the form of sulfur dioxide.These sulfur compounds emitted into the air can cause acid rain,endanger human health,acidify the soil and endanger crops.The sulfur compounds in gasoline and diesel are mainly benzothiophene,dibenzothiophene and some sulfur-containing ether alcohols.Thiophene compounds account for 85% of the total sulfur content in diesel oil.Traditional desulfurization technology is difficult to meet the international standards,so it is necessary to adopt new methods to reduce the sulfur content.In this paper,multi-porous molecular sieves were prepared,and dibenzothiophene was used as a simulated sulfide.Different multi-porous molecular sieves were prepared to remove sulfides.This paper studies the following aspects in detail:(1)Four kinds of multi-stage porous titanium-silicon molecular sieves with different two-dimensional lamellar titanium were prepared by one-step hydrothermal synthesis method,and their properties were studied by loading different titanium content molecular sieves.XRD characterization shows that the prepared zeolite belongs to ZSM-5 zeolite.SEM shows that its surface is spherical.TEM shows that the prepared zeolite belongs to two-dimensional lamellar structure.BET test shows that the prepared zeolite has a large specific surface area.Using dibenzothiophene as raw material,acetonitrile as solvent,1,3-diisopropylbenzene as internal standard and hydrogen peroxide as oxidant,the catalytic performance of the zeolite with 40 Si/Ti ratio was tested by gas chromatography.The catalytic performance of the zeolite was the best,and the conversion of Dibenzothiophene was the highest.After 10 hours,the conversion of Dibenzothiophene could reach 55%.The selectivity is the best and the utilization rate of hydrogen peroxide is the highest.The kinetics of hydrogen peroxide is simulated and the results show that the kinetic reaction belongs to the first order reaction.(2)A TS-1 zeolite was synthesized by one-step hydrothermal synthesis,and then multiporous TS-1 zeolite(HTS-1)was prepared by dissolving silicon with sodium hydroxide and aspartic acid as protective agent.The structure of TS-1 zeolite with different Si/Ti ratios was characterized by XRD,SEM and nitrogen adsorption-desorption isotherms.When sodium hydroxide treatment time was 30 min,sodium hydroxide concentration was 1 mol/L,molecular sieve mass was 0.15 g and aspartic acid mass was 0.5g,the oxidative desulfurization performance of TS-1 zeolite with Si/Ti 20 was the best,and dibenzothiophenoxy was the best.The conversion rate and selectivity of conversion to dibenzothiophene sulfone can reach 45% and 98%.The kinetic reaction is first order.(3)In order to study the effect of different concentration of sodium hydroxide on silica dissolution in molecular sieves,four different concentrations of sodium hydroxide solutions were prepared,namely 0.5mol/L? 1.0 mol/L? 1.5 mol/L and 2 mol/L.The results showed that when 1.5mol/L sodium hydroxide,1 g aspartic acid and 0.3 g ZSM-5 zeolite were stirred at room temperature for 30 minutes,the oxidative desulfurization effect of the prepared zeolite was the best.After 4 hours,the conversion and selectivity of Dibenzothiophene reached 56 % and 99 %,which indicated that the reaction was a first-order kinetic reaction,and all of the dibenzothiophene was converted to dibenzothiophene sulfone. |
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