AlPO4-5 is the most extensively studied material in exploring the crystallization mechanism of aluminophosphate molecular sieves, and it can be synthesized using 4-dimethylaminopyridine (DMAP) as an organic structure-directing agent (OSDA). Achieving the AlPO4-5 intermediate in the crystalline form would be of great importance and significance for this purpose. In this study, we proposed a concept that by carefully regulating the synthesis conditions, crystalline alumimophosphate intermediates could be rationally prepared. A crystalline AlPO4-5 intermediate, (C7H11N2)2(H3O)(Al3P4O16)·(H2O)2.5 (1), was, therefore, synthesized by significantly increasing the amounts of orthophosphoric acid and DMAP. The intermediate 1 consists of alternating organic DMAP and inorganic [Al3P4O16]3− layers with abundant hydrogen bonds and can transform to the AlPO4-5 framework upon heating in air or through a steam-assisted conversion (SAC) method. To unravel the role of DMAP in the transformation, pure AlPO4-5 (2) was also synthesized by altering the synthesis conditions. The supramolecular assembly templating (SAT) effects of DMAP in 1 and 2 were verified via fluorescence spectra. Thus, the π–π stacking interactions between the DMAP molecules and the abundant hydrogen bonds between the adjacent layers are considered to be important for the phase transformation of 1. This crystalline intermediate would promote the understanding of the crystallization mechanism in the system of aluminophosphate molecular sieves.
Yanyan Xu,Lu Tianliang,Bu Ningning,Luo Qianqian,Qing Yashi,Lin Li
Abstract Catalytic conversion of biomass based platform chemicals to value added chemicals has attracted much attention recently. In this work, Ni-based catalysts were developed for the conversion of levulinic acid to γ-valerolactone. By investigation of reduction behavior of NiO, it was found that a relatively low reduction temperature (300°C) can provide the reduction of NiO to Ni 0 . The high reduction temperature (500°C) generally applied in literature is not necessary. The effect of supports was also studied, and hierarchical AlPO 4 -5 (AlPO 4 -5-meso) supported Ni showed the best catalytic performance due to the proper pore size of AlPO 4 -5-meso, which contains both micropores and mesopores. The effect of Ni loading was also investigated, 10 wt % of Ni is enough for this reaction, which is lower than the reported amount of Ni loading. By using Ni/AlPO 4 -5-meso with 10 wt % Ni as catalyst, 84% γ-valerolactone yield and 100% levulinic acid conversion can be obtained after reaction for 10 h at 180°C.
SAPO-34 catalysts with high selectivity for light olefins were first synthesized via the introduction of phosphomolybdic acid (HPMo) and AlPO 4 -5 zeolite into the initial gel. The physical and chemical characteristics of the synthesized catalysts were determined by a series of techniques and the catalytic performance of the modified composite zeolites for the methanol-to-olefin (MTO) reaction was investigated. The results indicated that HPMo-modified SAPO-34 was featured with more Brønsted acid sites, more mesopores, and a smaller crystal size, thereby demonstrating superior catalytic performance. The further combination with AlPO 4 -5 (16.7 wt%) prolonged the lifetime of the HPMo-modified SAPO-34, which is thought in this paper related to its 12-ring straight channel (0.7–0.8 nm) and the absence of any Brønsted acid sites. The MTO tests showed that the light olefins selectivity for the modified composite zeolites reached 95.1 %, while the catalyst lifetime remained at 445 min
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