Sulfated zirconia, as a promising catalyst in various acid-catalytic reactions, still suffer from unsatisfactory catalytic stability and regeneration performance due to severe leaching of sulfur species, while aluminum modification can effectively overcome these drawbacks. Unfortunately, the limited acceptability of aluminum content by co-precipitation and milling methods remains a critical issue. Herein, an effective strategy of coating sulfated zirconia on the surface of γ-Al 2 O 3 was developed to synthesize the novel Al 2 O 3 @SO 4 2- /ZrO 2 catalyst with high aluminum content. The synthesis variables were investigated and systematically optimized. The structural and acidic properties of Al 2 O 3 @SO 4 2- /ZrO 2 were determined by XRD, HR-TEM equipped with EDX, N 2 adsorption-desorption isotherms, EA, FT-IR, NH 3 -TPD and Py-FTIR. Results indicated that the unique structure constructed by sulfated zirconia coated on γ-Al 2 O 3 not only realized the stabilization of favorable tetragonal zirconia phase even at exceedingly high aluminum content but also promoted Brønsted acid sites. Accordingly, the optimal Al 2 O 3 @SO 4 2- /ZrO 2 - 50% performed outstanding catalytic activity and stability, given the olefins conversion of 98%-75% during the continuous reaction experiment. Owing to the alleviation of sulfur loss by Al-promoting effects, excellent regeneration performance, with olefins conversion only slightly declining after 4 consecutive reaction-regeneration cycles, was also obtained. The mechanistic pathway for the alkylation of olefins with aromatics over Al 2 O 3 @SO 4 2- /ZrO 2 was also investigated and proposed by GC–MS analysis.
Su Yang,Xiaoxuan Guo,Xiaomei Pan,Liuyu Gu,Xueping Liu,Lijing Gao,Guomin Xiao
Concentrated sulfuric acid is generally used as a catalyst for producing brominated alkanes in traditional methods, but is highly corrosive and difficult to separate. This work reports the preparation of bromopropane from n-propanol based on a reactive distillation strategy combined with alumina-modified sulfated zirconia (Al2O3/SO42−/ZrO2) as a heterogenous catalyst. As expected, under the optimum reaction conditions (110 °C), the yield of bromopropane was 96.18% without side reactions due to the reactive distillation strategy. Meanwhile, the microscopic morphology and performance of Al2O3/SO42−/ZrO2were evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Brunner–Emmet–Teller (BET), Fourier transform infrared spectroscopy (FT–IR), and other characterization methods. The results confirmed that the morphology of zirconia sulfate is effectively regulated by the modification method of alumina, and more edges and angles provide more catalytic acid sites for the reaction. Furthermore, Al2O3/SO42−/ZrO2exhibited high stability and remarkable reusability due to the strong chemical bond Zr–Al–Zr. This work provides a practical method for the preparation of bromopropane and can be further extended to the preparation of other bromoalkanes.Keywords:sulfated zirconia;modification of alumina;bromopropane;catalytic distillation
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