Zhiguo Zhu

One-pot synthesis of 5-hydroxymethylfurfural from glucose using bifunctional [Sn,Al]-Beta catalysts

Abstract The one-pot synthesis of 5-hydroxymethylfurfural (5-HMF) from glucose was investigated, using [Sn,Al]-Beta catalysts prepared by a combination of partial dealumination and isomorphous substitution of Sn into the zeolite framework. The amount of Al in [Sn,Al]-Beta was adjusted by changing the concentration and acid treatment time, and the Sn content was varied by changing the SnCl4 vapor treatment time. [Sn,Al]-Beta contains framework Al-related Bronsted acid sites and tetrahedral Sn-related Lewis acid sites, and is therefore a bifunctional solid acid catalyst. The reaction parameters for the [Sn,Al]-Beta-catalyzed one-pot conversion of glucose to 5-HMF were optimized. [Sn,Al]-Beta with a suitable Sn/Al molar ratio gave a glucose conversion of 60.0% and 5-HMF selectivity of 62.1%.

Hydrophobic Nanosized All-Silica Beta Zeolite: Efficient Synthesis and Adsorption Application

All-silica beta zeolite, synthesized by conventional hydroxide route, usually possesses small crystal size of a few hundred nanometers but poor hydrophobicity, whereas the fluoride-mediated one exhibits to be highly hydrophobic but microsized. To obtain nanosized all-silica beta zeolite with excellent hydrophobicity, an innovative and efficient hydrothermal route via interzeolite transformation for synthesizing all-silica beta zeolite is proposed in present study. With the assistance of beta seeds and tetraethylammonium hydroxide as the structure-directing agent, siliceous beta zeolite is well-crystallized at a high solid yield via dissolution-recrystallization of all-silica ITQ-1 crystals at an extremely low water content (H2O/SiO2 molar ratio of 1). The obtained all-silica beta crystals are composed of 30-70 nm nanoparticles and highly hydrophobic just next to siliceous beta-F zeolite synthesized by environmentally unfriendly fluoride route, which is derived from relatively small amounts of internal defect sites. Thus, this beta zeolite is superior to other pure silica beta zeolites in the adsorption of large-sized volatile organic compounds (VOCs), which is mainly attributed to its high total pore volume and specific surface area as well as excellent hydrophobicity.

Controllably confined ZnO on USY zeolites (USY@ZnO/Al2O3) as efficient Lewis acid catalysts for Baeyer‐Villiger oxidation

A ZnAl-LDHs (layered double hydroxides) phase was readily formed on the surface of a USY zeolite through a distinctive in situ growth method that benefitted from the interaction of the added Zn source and aluminum species extracted from the Al-rich USY zeolite crystals. The migration of aluminum and simultaneous interaction with the external Zn source took place in one pot to form a ZnAl-LDHs phase coated on the surface of the USY crystals. Upon calcination, the ZnAl-LDHs phase was transformed into a ZnO/Al2 O3 composite that was still firmly anchored on the USY zeolite, without sacrificing the core-shell structure. The resultant USY@ZnO/Al2 O3 materials gave rise to unique Lewis acidity and hierarchical porosity, which endowed the catalyst with promising performance in the Baeyer-Villiger oxidation of ketones with H2 O2 or bulky tert-butyl hydroxide as an oxidant.

Stabilizing Low‐Silica Zeolites through Aluminum Sulfate Assisted Cannibalistic Dealumination

A versatile dealumination strategy was proposed to stabilize low‐silica zeolites through cannibalistic interaction between the host framework Al (FAL) and the guest aluminum salt. It is possible to capture selectively the FAL and Na ions in NaY zeolite by employing a special external Al source such as aluminum sulfate as the dealuminating agent. This unique postmodification reduces the FAL amount efficiently and converts the chemically reacted Al species into a γ‐alumina support for the catalytically active component of zeolite, which avoids wasting Al sources. Possessing greatly enhanced hydrothermal stability, newly generated intracrystal mesopores, as well as an optimized distribution of FAL, the resultant dealuminated Y zeolite catalysts can be used practically in heavy oil cracking.