Fluidized reaction method for synthesizing propylene oxide by gas phase epoxidation of propylene and hydrogen peroxide

A fluidized reaction method for synthesizing propylene oxide by gas phase epoxidation of propylene and hydrogen peroxide, wherein a fluidized epoxidation reaction is conducted at normal pressure and temperature above 100° C.;

• the raw materials of propylene and hydrogen peroxide are directly mixed in gas phase;
• feed gas enables catalyst to be fluidized in an epoxidation reactor;
• the catalyst is a microspherical catalyst formed with a kind of alkali metal ion modified titanium silicalite zeolite TS-1;
• the alkali metal ion modified titanium silicalite zeolite TS-1 has the characteristic that alkali metal ions are reserved on the silicon hydroxyl of a modified TS-1 zeolite to modify the local environment of the framework titanium;
• therefore, an infrared characteristic absorption band of framework titanium active site of the alkali metal ion modified titanium silicalite zeolite TS-1 appears in a range above 960 cm−1 and below 980 cm−1;
• the preparation steps of the catalyst are as follows:
• at first step:
• selecting a TS-1 zeolite matrix;
• the TS-1 zeolite matrix shall meet the following requirements:
• the crystal size is ≥0.3 micron;
• the silicon-titanium molar ratio is ≤200;
• the index value of the framework titanium content is ≥0.4;
• and relative crystallinity is ≥85%;
• at second 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 third step:
• conducting a degree controlled hydrothermal treatment on the TS-1 zeolite matrix by using the alkali metal hydroxide modification solution;
• 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 modification temperature is 100° C.-200° C.;
• hydrothermal modification time is 10-20 hours;
• at fourth step:
• conducting post-treatment on the hydrothermally modified TS-1 zeolite;
• the post-treatment comprises solid-liquid separation, washing, drying and calcining;
• in a washing process, modified TS-1 zeolite wet material obtained by solid-liquid separation is washed by using 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;
• the concentration of the alkali metal hydroxide solution for washing is 0.001-0.05 mol/L;
• at fifth step:
• molding the alkali metal ion modified titanium silicalite zeolite TS-1 as microspherical catalyst by a spray forming method, wherein the spray forming method is as follows:
• (1) the suspension of the modified TS-1 zeolite is prepared with the acid-catalyzed hydrolysis solution of tetraethyl orthosilicate:
• tetraethyl orthosilicate is added to deionized water under stirring;
• then, concentrated nitric acid is added dropwise to the solution to hydrolyze the tetraethyl orthosilicate at room temperature under acidic conditions and distill the alcohol to obtain a binder glue solution;
• then, an alkali metal ion modified TS-1 zeolite is dispersed in the binder glue solution, and the dispersion liquid is treated with a colloid mill to make the D90 size value of the particles in the zeolite suspension less than or equal to 8 microns, thereby obtaining a zeolite suspension for spray forming, wherein the pH of the tetraethyl orthosilicate hydrolyzed at room temperature under the acidic conditions is 3.0-4.0;
• alcohol distilling conditions are:
• temperature is 55-60° C.;
• the total solid content in the zeolite suspension is 20-35 wt %;
• the percentage of the alkali metal ion modified TS-1 zeolite in all of the solid matters in the zeolite suspension is 40-80 wt %;
• (2) a spray drying tower is used for spray forming of the suspension:
• the temperature of hot air entering the tower is 350° C., and the temperature of exhaust air exiting the tower is not less than 100° C.;
• (3) the spray forming product collected from the spray drying tower are dried and calcined to obtain a microspherical catalyst, wherein drying is conducted at 110° C. until the dry basis content is not less than 90 wt %;
• calcining temperature is 540-600° C., and calcining time is 1-10 hours.