Highly active n-butene skeletal isomerization catalyst and preparation method thereof

The present invention belongs to the technical field of catalysts, and specifically relates to a high-activity catalyst for the skeletal isomerization of n-butene and a preparation method thereof. The catalyst for the skeletal isomerization of n-butene of the present invention is a nano-micron composite crystal obtained by mixing and molding FER zeolite micron crystals with an amorphous silica-alumina sol binder and then transforming the binder into FER zeolite nanocrystals through a hydrothermal reaction; the FER zeolite micron mother crystal has a flaky grain size of 0.5 micron to 2 micron, a silicon-aluminum molar ratio of 15-60, and a flaky nanocrystal size generated by hydrothermal transformation of the flaky nanocrystals of 20-100 nanometers. The composite crystal FER zeolite catalyst exhibits the characteristics of high activity, high selectivity, high stability, high strength and wear resistance in the n-butene isomerization reaction.

1. A high-activity n-butene skeletal isomerization catalyst, characterized in that it is obtained by using FER zeolite micron crystals as mother crystals, mixing and molding with an amorphous silica-alumina sol binder, and then transforming the binder into FER zeolite nanocrystals through a hydrothermal reaction; the FER zeolite micron sheet crystal size is 0.5 micron to 2 micron, the silicon-aluminum molar ratio is 15-60, and the size of the sheet nanocrystals generated by hydrothermal transformation is 20-100 nanometers.
2. The catalyst according to claim 1, characterized in that the FER zeolite is ferrierite, ferrierite, ZSM-35, FU-9, NU-23, ISI-6 with the same skeleton topology.
3. The catalyst according to claim 1, characterized in that the weight ratio of the FER micron zeolite crystals in the catalyst is 50-95%, and the weight ratio of the FER zeolite nanocrystals generated by the amorphous silica-alumina sol binder in the catalyst is 5-50%.
4. The catalyst according to claim 1, characterized in that the FER micron zeolite crystal is a commercial product or laboratory product of hydrogen type, sodium type, sodium potassium type.
5. The catalyst according to claim 1, characterized in that the composition of the amorphous silica-alumina sol binder is calculated by molar number: OH/SiO₂=0.05-0.5, H₂O/SiO₂≥2, Si0₂/Al₂O₃=15-80.
6. A method for preparing a high-activity catalyst for the skeletal isomerization of n-butene as claimed in any one of claims 1 to 5, characterized in that the specific steps are as follows:
   (1) Mixing amorphous silica-alumina sol binder, FER zeolite micron crystal powder and water in a certain proportion, and forming them into granules by an extruder;
   (2) Drying the formed granules, and then placing them in a vapor-solid phase reactor, and hydrothermally reacting them in a water vapor atmosphere containing or not containing an organic directing agent, the reaction temperature is 100-200°C, and the reaction time is 5-80 hours; wherein, if the content of FER zeolite micron crystals is less than 85%, an organic directing agent is added to the water vapor atmosphere during the hydrothermal reaction;
   (3) After the hydrothermal reaction is completed, the catalyst particles are subjected to ammonium salt or acid exchange to remove sodium ions, and then dried and calcined, the calcination temperature is 400-800°C, and the calcination time is 2-20 hours, to obtain the catalyst of the present invention. 7. The preparation method according to claim 6, characterized in that the organic directing agent is one or a mixture of two of ethylenediamine, pyrrolidine, tetrahydrofuran, trimethylamine, and pyridine.
7. The preparation method according to claim 6, characterized in that during the molding process in step (1), sesbania powder is added as needed, and the amount of sesbania powder is not more than 4%.
8. The preparation method according to claim 6, characterized in that the amorphous silica-alumina sol binder, wherein the silicon source used is silica sol, white carbon black, silica gel or water glass, the aluminum source is aluminum hydroxide, aluminum sulfate, aluminum nitrate or sodium aluminate, and the alkali source is one or both of sodium hydroxide and potassium hydroxide.