Search

Sulfamic acid functionalized polyvinyl chloride catalysts (PVC-N-SO3H, N = EDA, DTA, TTA, TPA, PHA) were prepared as efficient heterogeneous solid acid catalysts via two-step treatment processes. The prepared catalysts were characterized by X-ray diffraction analysis (XRD), TG thermograms/derivative thermogravimetric (TG/DTG), transmission electron microscope (TEM), elemental mappings and energy-dispersive spectroscopy analyses (STEM-EDS), and FTIR measurements (FTIR) as well as acid–base back-titration. The acetalization of aldehydes (ketones) and alcohols to acetal (ketal) was selected to evaluate the acid catalytic performance of PVC-N-SO3H. The results showed that PVC-EDA-SO3H exhibit excellent activity and reusability due to its highly exposed sulfonic acid sites, high surface acid density (2.28 mmol g−1) for the conversion of aldehydes (ketones) to acetal (ketal). This new solid acid has obvious advantages in reusability and catalytic activity over traditional homogeneous concentrated sulfuric acid and heterogeneous sulfonated resin catalysts. Furthermore, PVC-EDA-SO3H exhibited an excellent catalytic performance in the synthesis of 12 acetals (ketals) as well as a good compatibility in the hydroxyalkylation of phenol with formaldehyde to bisphenol F (BPF) and the esterification reaction of oleic acid and methanol to biodiesel. More importantly, it could also be recovered easily and used repeatedly at least nine times without an obvious decrease in the activity. [ABSTRACT FROM AUTHOR]

BACKGROUND The synthesis of solid acid catalysts of recoverable and environmentally friendly nature has gained increasing attention in recent years. The distribution of Brønsted and Lewis acidic sites on the surface of sulfated metal oxides determines the catalytic performance, which is affected by many key factors, such as the concentration of sulfuric acid impregnated and the morphology of the metal oxides used. In this study, TiO2 nanosheets were successfully synthesized and used as carrier for the preparation of solid acid catalysts. RESULTS: The concentration of sulfuric acid for the impregnation resulted in various distributions of Brønsted and Lewis acidic sites on the surface of sulfated TiO2. With a medium concentration of sulfuric acid (1 mol L−1) for the impregnation, the highest ratio of Brønsted to Lewis acidic sites can be achieved, and the catalyst showed superior catalytic activity for the conversion of furfuryl alcohol (FA) to ethyl levulinate (EL) in ethanol and the conversion of fructose to 5‐hydroxymethylfurfural (HMF) in dimethyl sulfoxide (DMSO). CONCLUSION: The sulfation of TiO2 nanosheets induced the formation of both Brønsted and Lewis acidic sites. The Brønsted acidic sites were more effective for catalyzing the conversion of FA or fructose. The poor recyclability of the 1.0‐SO42−/TiO2 catalyst in the conversion of FA to EL in ethanol, a protic solvent, was due to the leaching of sulfur species. The deactivation of the catalyst in DMSO was due to coking, which could be resolved via calcination of the coke species in air. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Structural architecture and unique physical, chemical, thermal, and mechanical properties of ordered mesoporous silica materials can be tuned. High flexibility of silica materials can provide good support for different metal nanoparticles, metal oxides, and organic functional groups. The properties of silica materials can vary to a great extent by introducing the optimum amount of metal species co-doped, dispersed or composites with the silica mesostructure. The present study investigates the deposition of CeIII/IV/CeO2 on the silica surface by using different wet chemical engineering methods, illustrates the syntheses of those ceria-silica or metal doped ceria-silica nanomaterials and offers clear picture of the influence that incorporated ceria concentration has on the properties of the support material. Ceria-silica based ordered mesoporous materials can have numerous applications is also discussed in this article, emphasizing its use as a heterogeneous catalyst in particular. [ABSTRACT FROM AUTHOR]

The synthesis and catalytic activity of a new sulfonic acid-functionalized periodic mesoporous organosilica (PMO) obtained by an in situ oxidation process have been reported. This material was prepared by co-condensation of a homemade thiol-functionalized bis-silane precursor (EtO) 3 Si-R-Si(OEt) 3 (R = CH 2 CHSH) with 1,2-bis(triethoxysilyl)ethane (BTEE) in the presence of a nonionic triblock co-polymer. Thiol groups were oxidized either in situ during the formation of the mesostructure, or by a post-synthesis oxidation of the solid material. The in situ generated sulfonated PMO material had a well-ordered hexagonal mesoporous structure and a narrow pore size distribution. The sulfonic acid concentration of these materials was in the range of 0.85–1.48 mmol H + g −1 . The catalytic performance of these sulfonic acid-functionalized materials was evaluated and compared with the commercial resin Amberlyst-15 in the esterification of acetic acid with benzyl alcohol. The in situ sulfonated PMO has shown to be an efficient, robust, and recyclable catalyst in acid-catalyzed reactions throughout consecutive catalytic cycles. [ABSTRACT FROM AUTHOR]

A reaction network for acid-catalyzed hydrocarbon hydroprocessing in the C2 to C12 range has been generated, as part of a larger work to model a naphtha hydrocraking unit at the elementary step level. The structure of the feedstock molecules is stored as Boolean matrixes, facilitating their mathematical manipulation according to the rules of each elementary reaction step during the reaction network generation. Detailed algorithms and examples are shown for every elementary reaction step. Acyclic and cyclic species are considered, up to two fused aromatic, olefinic or naphthenic rings. Besides conventional elementary reactions, algorithms for aromatic isomerization (methyl and ethyl migration) and dealkylation were developed. It must be highlighted that the complexity of the reaction network should be weighed against the available chromatographic data resolution. Therefore, mathematical restrictions might be added to the generated structures, such as maximum number of ramifications or maximum molecule size within a group of isomers. A sensitivity analysis of these restrictions was carried out, to determine their impact on the dimension of the generated reaction network. [ABSTRACT FROM AUTHOR]