Preparation method of alkali metal ion modified titanium silicalite zeolite for gas phase epoxidation of propylene and hydrogen peroxide

A preparation method of an alkali metal ion modified titanium silicalite zeolite for the gas phase epoxidation of propylene and hydrogen peroxide, wherein in the alkali metal ion modified titanium silicalite zeolite, alkali metal ions are reserved on the silicon hydroxyl of the modified TS-1 zeolite;

• an infrared characteristic absorption band of framework titanium active site modified by the alkali metal ions is in a range above 960 cm−1 and below 980 cm−1;
• TS-1 zeolite matrix of the alkali metal ion modified titanium silicalite zeolite meets the following requirements:
• a crystal size is ≥0.3 micron;
• a silicon-titanium molar ratio is ≤200;
• an index value of the framework titanium content is ≥0.40;
• and relative crystallinity is ≥85%;
• wherein specific steps of conducting a degree controlled hydrothermal treatment on the TS-1 zeolite matrix by using an alkali metal hydroxide modification solution in the preparation method are as follows:
• at first step:
• preparing an alkali metal hydroxide modification solution;
• the concentration of the alkali metal hydroxide modification solution is 0.05-0.2 mol/L;
• at second step:
• conducting the degree controlled hydrothermal treatment on the TS-1 zeolite matrix with the alkali metal hydroxide modification solution to obtain a hydrothermally modified TS-1 zeolite;
• the ratio of volume of the alkali metal hydroxide modification solution to weight of the TS-1 zeolite matrix is in the range of 5-15 ml/g;
• hydrothermal treatment temperature is 100° C.-200° C.;
• hydrothermal treatment time is 10-20 hours;
• at third step:
• conducting post-treatment on the hydrothermally modified TS-1 zeolite;
• the post-treatment comprises solid-liquid separation, washing, drying and calcining;
• in the washing process, a modified TS-1 zeolite wet material obtained by solid-liquid separation is washed with a low concentration alkali metal hydroxide solution, and the degree of washing is satisfactory when no precipitate appears after the washing solution is neutralized with acid;
• a concentration of the alkali metal hydroxide solution for washing is 0.001-0.05 mol/L.