TS-1 catalyst is an excellent candidate for hydrogen peroxide oxidation (HPO) of linear, branched and cyclic alkanes.ts-1 catalyst It is a highly effective catalyst for epoxidation reactions, with high selectivity towards propylene (PO) and good tolerance against side reactions. However, its poor shape-selectivity for the oxidation of larger hydrocarbons limits its application in industrial processes.
To improve the catalytic properties of TS-1, it is important to increase its surface area and mesopore volume.ts-1 catalyst The present work demonstrates the feasibility of achieving these effects by post-treatment of TS-1 with a mixed basic solution containing ammonia and TPABr. The etching effect of ammonia provides the required basic environment, while the co-existence with TPABr allows the guided growth of Ti atoms to create secondary porosity through a dissolution-recrystallization process. The resulting post-modified TS-1 zeolite has much improved mass transfer ability, significantly improving its epoxidation performance.
A green preparation method for TS-1 is also proposed in the present study, utilizing inexpensive inorganic titanium silicalite and low-concentration ammonia water as raw materials and alkali sources.ts-1 catalyst Seed crystals are added to reduce the energy barrier for the hydrothermal synthesis, thereby shortening the preparation time and allowing for the repetition of experiments under the same conditions. The resulting TS-1 catalysts have been shown to perform exceptionally well in the chloropropene epoxidation reaction, with excellent conversion of H2O2 and selectivity of epichlorohydrin even after being reused twice.
The FTIR spectra of the sample TS-1-A, TS-1-B and TS-1-S show strong absorption in the region of hydroxyl vibrations, which is consistent with the presence of abundant internal and external silanol sites on the crystalline structures.ts-1 catalyst The sample TS-1-B, which has a higher content of framework Ti and a large surface area, exhibits the best catalytic activity in the epoxidation of propylene.
In addition, the textural properties of TS-1-A, TS-1-B, and TS-1-S are similar to one another, as demonstrated by the type-I N2 adsorption isotherms (see Supplementary Table S3).ts-1 catalyst The pore size distribution diagrams further confirm that the samples are hierarchical, with a small microporous zone at the apex of the macropores and a large mesopore zone around the pore axis.
In order to investigate the influence of the amount of added TBOT on the properties of the TS-1 zeolite, different amounts of Ti were added to the precursor sol, with the molar ratio of Si/Ti being varied accordingly. The samples with different amounts of added TBOT were subjected to a series of characterization tests, including the N2 adsorption isotherms, XRD and SEM. The results show that the apex of the mesopore zone is closer to the apex of the macropore, and the pore axis is tilted in the direction of the c-axis in all three cases. Moreover, the sample with the highest amount of Ti, TS-1-B, has a smaller crystal size and a lower RC, but a larger pore volume, indicating that a large number of mesopores exist in the TS-1-B sample. The enhanced catalytic performance of the TS-1-B sample may be attributed to its larger micropore and mesopore volume, allowing for greater mass transfer of reactant molecules into and out of the mesopores.
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