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The fabrication of low-cost, recyclable, reusable, and heterogeneous catalysts is of considerable significance for green chemistry. In this study, a nanocomposite catalyst, MCM-41-supported Zn–Co double metal cyanide (MCM-41@DMC), was prepared using the synchronous dropping method. Thereafter, the composition, crystal structure, complexing state, morphology, and thermal stability of the catalyst were characterised using scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller analysis, and thermogravimetry. The effects of different organic ligands on the catalytic activity of samples were evaluated, and the results showed that ethyl acetoacetate exhibited the best catalytic activity owing to its ketone coordination. The use of the MCM-41 support was beneficial for improving the catalytic activity because it reduced the crystallinity and substantially increased the external specific surface area of the catalyst. The experimental results pertaining to the use of the MCM-41@DMC catalyst in the fabrication of polypropylene glycol showed that the conversion of propylene oxide and molecular weight reached 90.6% and 2900, respectively. This study provides a new strategy for the green synthesis of poly(propylene glycol) products. [ABSTRACT FROM AUTHOR]

Layered double hydroxide (LDH) has been recognized as one type of the most promising shell material. In this contribution, SiO2@Mg-Al-LDH core-shell nanocomposites with different shell morphologies were prepared and characterized via XRD, SEM, TEM, FT-IR, TG-DTA, and BET in detail. The as-prepared SiO2@LDHs exhibit different base catalysis for the synthesis of propylene glycol monomethyl ether (PGME). The results indicate that LDH shell oriented vertically on the core could be generated by the sol-gel method (SG-SiO2@LDH) and displays the highest catalytic activity and stability among three materials. The horizontally oriented shell morphology tends to be formed by the self-assembly method (SA-SiO2@LDH), which maintains the original LDH structure but unstable. The formation of a third morphology called mixed platelet is contributed to the coexistence of horizontally and vertically platelets. It has been seen in the case of co-precipitation (CP-SiO2@LDH). Integrating the experimental result analysis, synthesis methods can significantly influence the nucleation rate, which would fabricate different shell morphologies. Furthermore, core-shell nanomaterials with special morphology may have certain application prospects in solid catalysis. [ABSTRACT FROM AUTHOR]

Hierarchical HBEA catalysts were fabricated through alkaline treatment and evaluated in a fixed-bed reactor. The relative crystallinity, pore property, Si/Al molar ratio, coke formation and structure of catalysts were investigated by the methods including X-ray diffraction, N2 physisorption, X-ray fluorescence, thermogravimetric analysis and transmission electron microscope, respectively. The acidity of catalysts was studied by Fourier transform infrared spectrometry using pyridine as the probe molecule. These results demonstrated that pure NaOH treatment improved the mesoporosity of catalyst, while decreased the β-methylnaphthalene selectivity and catalyst stability due to the partially destroyed framework and an increase in the concentration of Lewis acid sites. The Lewis acid sites are responsible for the hydride transfer and subsequent reaction that form coke. In contrast, the presence of tetra-propyl-ammonium hydroxide in the mixed-alkali treatment resulted in regular mesopores development, preserved intrinsic zeolite properties and Lewis sites proportion, leading to the maintained β-MN selectivity and coke deposition rate. The increased mesoporosity and strong Brönsted acid sites amount per number of coke were responsible for the improved coke tolerance of mixed-alkali treated HBEA, and thus its deactivation rate was 41.7% lower than that of HBEA catalyst. [ABSTRACT FROM AUTHOR]

Selective isomerization of 1-methylnaphthalene was carried out in a fixed-bed reactor over HBEA catalysts modified by acid and tetraethoxysilane treatments, respectively. Catalysts were characterized by X-ray diffraction, NH temperature-programmed desorption, N physisorption, inductively coupled plasma analysis, thermogravimetric analysis and Fourier transform infrared spectrometry after adsorption of pyridine. The results demonstrated that tetraethoxysilane treatment successfully passivated external active sites of the zeolite, but had little effect on the selectivity of isomerization reaction and catalytic stability. Dealumination of HBEA zeolite by treatment with oxalic and hydrochloric acids can lead to higher surface area and pore volume. Sufficiently strong Brönsted acidic sites were found to be responsible for the isomerization activity. Furthermore, a decrease in the number of Lewis acidic sites in acid-modified zeolites were advantageous to suppress the hydride transfer and subsequent side reactions that form coke, leading to higher 2-methylnaphthalene selectivity and longer catalytic life. [ABSTRACT FROM AUTHOR]

p-Aminophenol was synthesized by catalytic hydrogenation of p-nitrophenol on Ni nanoparticles prepared by a chemical reduction method using polyamidoamine (PAMAM) dendrimers as templates. The as-prepared Ni nanoparticles were characterized by XRD, LRS, EDS, FTIR, FESEM, HRTEM and N sorption analysis. Smaller-sized, better-dispersed and more active Ni nanoparticles can be successfully achieved using PAMAM dendrimers as templates. Analysis results show the as-prepared Ni nanoparticles are pure f.c.c. nickel. In hydrogenation reactions of p-nitrophenol, Ni nanoparticles show higher catalytic activity than that of Ni nanoparticles prepared in the absence of PAMAM dendrimers. The weight ratio of PAMAM/Ni is proved to be an important parameter on the catalytic activity of Ni nanoparticles and the optimal ratio is 15%. The reason proposed for higher catalytic activity of Ni nanoparticles is a combination effect of smaller particle size, better dispersion and more active Ni nanoparticles. [ABSTRACT FROM AUTHOR]