Studies On The Formation And Inhibition Of The Non-framework Ti Species In TS-1 During Hydrothermal Synthesis

Titanium silicalite (TS-1) was first synthesized in 1980's, which exhibited the unique catalytic performance in oxidation reaction involving H2O2 as the oxidant. These reactions are environmentally friendly that they have mild reaction conditions, high reaction selectivity, and the by-product is water. So, synthesis and industrial applications of TS-1 have become very important in past twenty years.Non-framework titanium species are the undesirable companions in the synthesis of TS-1 which used tetrapropylammonium bromide as cheap template. How to inhibit the formation of non-framework titanium species were investigated in the synthesis of TS-1, by using different silica sources(marked sol0,sol1,sol2 and sol3), solvents(IPA and acetylacetone) and additive ((NH4)2CO3). The UV-Vis,FT-IR result indicates that in synthesis of TS-1, all these, use silica source with low Na+and Al3+concentration (sol1), use acetylacetone as solvent and add appropriate amount (NH4)2CO3 or nitrogen protection during the synthesis can reduce the formation of non-framework titanium species and improve the catalyst performance in the liquid phase epoxidation of propylene:1. TS-1 used silica source with low Na+and Al3+concentration (sol1) have 63.7 conversion of H2O2 (XH202) while used silica source with high Na+and Al3+concentration (Sol3) is only 27.0.2. In the synthesis of TS-1, compared with isopropyl alcohol, use acetylacetone as solvent, the XH202 increase from 53.8 to 94.0, effective utilization of H2O2(UH2O2) increase from 55.1 to 94.6.3. Compared with non-additive, the best amount of additive in the synthesis of nano-TS-1 is (NH4)2CO3/Si=0.28(mol/mol) and the XH2O2 increase from 94.7 to 97.9, effective utilization of H2O2(UH2O2) increase from 49.6 to 97.7; the best amount of additive in the synthesis of micro-TS-1 is (NH4)2CO3/Si=1.0～1.2(mol/mol) and the XH202 increase from 53.8 to 64.8, effective utilization of H2O2(UH2O2) increase from 55.1 to 87.3.4. Nitrogen protection in the synthesis of TS-1, the XH202 of the product increase from 63.7 to 68.1, the UH2O2 of the product increase from 65.3 to 84.9.