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Heterogeneous solid base catalysis is valuable and promising in chemical industry, however it is insufficiently developed compared to solid acid catalysis due to the lack of satisfied solid base ca...

An octahedron-based gallium borate (Ga-PKU-1) with an open framework was prepared by the boric acid flux method and studied by XRD, SEM, FT-IR, TGA-DSC, BET and NH3-TPD. The borate hydroxyl groups in the 18-ring membered channels functioned as Bronsted acid centers and were proved to play an important role in the dehydration of isopropanol to propylene with high selectivity. However, the other two gallium borates, Ga4B2O9 and GaBO3, with similar elemental compositions showed completely different acidities and catalytic performance for isopropanol decomposition. Our results indicated that such a great difference in selectivity most probably originated from the changes in the coordination microenvironment from GaO6 to GaO5. The relationship between the structure and activity was discussed in detail, and an intrinsic mechanism for the selectivity preference was proposed according to the obtained results.

PKU-5 (Al 4 B 6 O 15 ) is potentially a solid acid catalyst, and it possesses an interesting open-framework composed of [AlO 6 ] and [B 2 O 5 ] groups. PKU-5 shows a high thermal stability, while no physical and chemical properties were investigated thus far, because of the difficulty in its synthesis. Cr-stabilized PKU-5 with the formula (Al 1− x Cr x ) 4 B 6 O 15 (0.08 ≤ x ≤ 0.14) can be easily prepared by annealing Cr-doped PKU-1 precursors. XRD and TEM experiments demonstrate Cr 3+ has been successively incorporated into the framework of PKU-5. NH 3 -TPD measurements indicate that the partial substitution of Al 3+ by Cr 3+ leads to a small change of acid sites in total amounts and distributions. Cr-PKU-5 shows a good catalytic activity for methanol dehydration from 300 to 450 °C. Other operation conditions, such as the Cr 3+ content, space velocity of methanol were also discussed in detail to evaluate its catalytic performance.