The pure silicon MWW were synthesized for the first time by means of a dry-gel conversion method utilizing N, N, N-trimethyl-1-adamantyl ammonium hydroxide and hexamethyleneimine as the structural directing agents. A vapor transport assisted crystallization method for obtaining complete crystallinity was developed to replace the traditional dry-gel conversion methods. TiCl 4 acid solution treatment was cleverly used for the implantation of titanium in MWW. Compared with Ti-ERB-1, the Ti content of boron- free Ti-MWW is only 20% of the former, the conversion rate of 1-hexene epoxidation is 2.3 times of the former and nearly 100% of H 2 O 2 efficiency.
Zijian Wang,Shuting Li,Jiashuo Zheng,Jiahan Li,Yanbing Tong,Ming Ke,Zhaozheng Song
MCM-22 zeolite synthesized by utilizing the hexamethyleneimine as the organic structure directing agent has a wide range of applications. For the growth mechanism of the typical sample, on the macro level, XRD, FT-IR, and SEM are used to confirm the epitaxial growth of the intercalation structure. On the micro level, eight different T sites of the zeolite are completely distinguished as well as the guidence of hexamethyleneimine on T 1 , T 2 , T 3 and T 5 sites has been demonstrated through DFT calculation and solid-state nuclear magnetic resonance. A series of MCM-22 zeolites display the good catalytic stability and dimerization selectivity. The synergy of hexamethyleneimine and amphiphilic organosilane optimizates the mesopore and acidity of the sample effectively, which makes the selectivity and yield of dimerization product exceed 94.8 % and 85.0 % after 12 hours respectively. At the same time, the carbon deposition decreases from 3.38 % to 3.13 %. This work provides a theoretical basis for the growth mechanism and application in olefin oligomerization of MCM-22 zeolite.
Hao Runming,Du An,Zhu Qingling,Wu Xue,Liu Sijia,Wang Ke,Wang Yang
5-Hydroxymethylfurfural (HMF) is a high value-added platform compound, converted into bio-based polyesters and biofuels etc. In this paper, we used two commercially available hexamethylenimine and cetyltrimethylammonium bromide (CTAB) as the structure-directing agents to synthesize HMWW zeolite nanosheets via one step. A series of HMWW zeolite nanosheets with different disorder index ( DI ) were controllably prepared by adjusting the amount of CTAB, operating also as an in situ exfoliating agent, converting fructose into HMF in the tetrahydrofuran/NaCl-H 2 O biphasic solvent with low boiling point. Successful construction of disordered HMWW zeolite nanosheets was verified by PXRD. Further characterizations by BET, SEM and TEM etc. show that HMWW 4.0 with the optimum DI of 0.67 has a disordered network-like arrangement of layers with the external surface area of 224 m 2 /g and the mesoporous size of 3.5 nm. Catalytic evaluations showed that HMF selectivity was closely related to DI of the catalysts. Under the optimized DI , fructose molecules are readily accessible to acidic sites on the external surface while larger external surface area is exposed. The HMWW 4.0 zeolite catalyzed fructose dehydration in the biphasic solvent, producing 90% HMF selectivity with 93% fructose conversion at 140 °C for 6 h. In the reuses of the HMWW 4.0 catalyst, HMF selectivity was around 90% with fructose conversion decreasing by ca. 10% after six runs, indicating that it possesses the promising stability. Graphical Abstract
危险品化学品经营许可证（带存储）