Shuai Yan,Xin Pu,Zhiyong Qi,Xiaoran Zhang,Xiaoyu Zhou,Xin Han,Lei Ye,Xinglong Qin,Jichang Liu
m -Cresol and p -cresol cannot be effectively separated using conventional distillation because of their proximate boiling temperatures. This study investigated the adsorption separation of cresol using the short b -axis ZSM-5 synthesized via a urea-assisted method. In contrast to the ellipsoidal HZSM-5, which was approximately 1 μm in length, the thickness of the sheet-like HZSM-5 decreased to 36 nm, resulting in an increase in total cresol adsorption capacity from 76 to 122 mg/g. Applying the CLD method, an increase in the TEOS:HZSM-5 ratio from 0 to 0.83 resulted in the increase in p -cresol adsorption capacity from 69 to 106 mg/g, while m -cresol adsorption capacity dropped from 53 to 12 mg/g. The adsorption selectivity significantly rose from 1.3 to 9.7. The adsorption kinetics and isotherms demonstrated that the process was exothermic for p -cresol and endothermic for m -cresol.
Graphical Sheet-like zeolite TS-1 was synthesized under hydrothermal conditions by adding seed and urea. Liquid seed and pre-crystallization could adjust thickness of sheet-like sample in b-axis direction. Epoxidation of 1-hexene with H 2 O 2 catalyzed by sheet-like TS-1 gave high selectivity of 1,2-epoxyhexane. In zeolite TS-1, the straight channel parallelled to the b-axis direction has larger pore size and thus is main diffusion channel for molecules. Shorter b-axis brings about shorter diffusion channel, which can leads to higher adsorption and diffusion rate. Therefore, with regard to the morphology modification of MFI zeolites, many studies touch on short b-axis zeolites have been reported. Unfortunately, most of the preparation processes require harsh synthesis conditions and complex organic templates, and they are not conducive to large-scale applications. In this work, cheap organic additive urea and seed crystals were added to synthesize sheet-like TS-1, which boasts short b-axis. At the same time a pre-crystallization was performed at the aging solution stage. In the b-axis direction, the zeolite TS-1 prepared in this way had a minimum thickness of about 50 nm. This is because urea can inhibit the growth of crystals in the b-axis direction, and the guiding effect of the seed liquid also plays the function of adjusting the b-axis thickness. In the epoxidation of 1-hexene with H 2 O 2 when catalyzed by sheet-like TS-1, the selectivity of the target product 1,2-epoxyhexane was significantly improved.
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