Homogeneous catalysts usually show higher catalytic activities than heterogeneous catalysts because of their high dispersion of catalytically active sites. We demonstrate here that heterogeneous catalysts of ionic liquids functionalized on superhydrophobic mesoporous polymers exhibit much higher activities in transesterification to form biodiesel than homogeneous catalysts of the ionic liquids themselves. This phenomenon is strongly related to the unique features of high enrichment and good miscibility of the superhydrophobic mesoporous polymers for the reactants. These features should allow the design and development of a wide variety of catalysts for the conversion of organic compounds.
As important industrial materials, microporous zeolites are necessarily synthesized in the presence of solvents such as in hydrothermal, solvothermal, and ionothermal routes. We demonstrate here a simple and generalized solvent-free route for synthesizing various types of zeolites by mixing, grinding, and heating solid raw materials. Compared with conventional hydrothermal route, the avoidance of solvents in the synthesis not only significantly reduces the waste production, but also greatly increases the yield of zeolite products. In addition, the use of starting solid raw materials remarkably enhances the synthesis efficiency and reduces the use of raw materials, energy, and costs.
Low-cost copper-amine complex was rationally designed to be a novel template for one-pot synthesis of Cu-SSZ-13 zeolites. Proper confirmation and appropriate size make this complex fit well with CHA cages as an efficient template. The products exhibit superior catalytic performance on NH(3)-SCR reaction.
Mesoporous zeolites are useful solid catalysts for conversion of bulky molecules because they offer fast mass transfer along with size and shape selectivity. We report here the successful synthesis of mesoporous aluminosilicate zeolite Beta from a commercial cationic polymer that acts as a dual-function template to generate zeolitic micropores and mesopores simultaneously. This is the first demonstration of a single nonsurfactant polymer acting as such a template. Using high-resolution electron microscopy and tomography, we discovered that the resulting material (Beta-MS) has abundant and highly interconnected mesopores. More importantly, we demonstrated using a three-dimensional electron diffraction technique that each Beta-MS particle is a single crystal, whereas most previously reported mesoporous zeolites are comprised of nanosized zeolitic grains with random orientations. The use of nonsurfactant templates is essential to gaining single-crystalline mesoporous zeolites. The single-crystalline nature endows Beta-MS with better hydrothermal stability compared with surfactant-derived mesoporous zeolite Beta. Beta-MS also exhibited remarkably higher catalytic activity than did conventional zeolite Beta in acid-catalyzed reactions involving large molecules.
Graphene with its two-dimensional sheet of sp 2 -hybridized carbon is a hot topic in the fields of materials and chemistry due to its unique features. Herein, we demonstrate that sulfated graphene is an efficient solid catalyst for acid-catalyzed liquid reactions. The sulfated graphene was synthesized from a facile hydrothermal sulfonation of reduced graphene oxide with fuming sulfuric acid at 180 C. Combined characterizations of XRD, Raman, and AFM techniques show that G-SO 3 H has a sheet structure (1-4 layers). IR spectroscopy shows that G-SO 3 H has a S]O bond, and the XPS technique confirms the presence of an S element in G-SO 3 H. Acid-base titration indicates that the acidic concentration of sulfonic groups in the sulfated graphene is 1.2 mmol g À1 . TG curves shows that the decomposition temperature (268 C) of the sulfonic groups on the sulfated graphene is much higher than that of conventional SO 3 H-functionalized ordered mesoporous carbon (237 C). Catalytic tests of the esterification of acetic acid with cyclohexanol, the esterification of acetic acid with 1-butanol, the Peckmann reaction of resorcinol with ethyl acetoacetate, and the hydration of propylene oxide show that sulfated graphene is much more active than the conventional solid acid catalysts of Amberlyst 15, OMC-SO 3 H, SO 3 H-functionalized ordered mesoporous silica (SBA-15-SO 3 H), graphene oxide, and reduced graphene oxide, which is attributed to the fact that the sulfated graphene almost has no limitation of mass transfer due to its unique sheet structure. Very importantly, the sulfated graphene has extraordinary recyclability in these reactions, which is attributed to the stable sulfonic groups on the sulfated graphene. The advantages, including high activities and good recyclability as well as simple preparation, are potentially important for industrial applications of the sulfated graphene as an efficient heterogeneous solid acid catalyst in the future.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.