Wei Shen

A facile route to synthesize endurable mesopore containing ZSM-5 catalyst for methanol to propylene reaction

A novel route is proposed for the preparation of mesopore containing zeolite ZSM-5 via in situ hydrothermal treatment of a solution containing alkali-dissolved SBA-15 containing carbonized surfactant P123 in the mesopores; it exhibited prominent stability enhancement for methanol to propylene reaction.

Nafion-resin-modified mesocellular silica foam catalyst for 5-hydroxymethylfurfural production from D-fructose.

Catalytic dehydration of D-fructose to 5-hydroxymethylfurfural (HMF) was investigated over a series of Nafion-modified mesocellular silica foam (MCF) materials. By using an impregnation method, Nafion resin was highly dispersed in the ultra-large pores of the MCFs. Highly efficient and selective dehydration of D-fructose to HMF was achieved in dimethyl sulfoxide solvent; an 89.3% HMF yield with 95.0% selectivity was obtained in the presence of the Nafion(15)/MCF catalyst. The effects of reaction temperature, reaction time, and solvent on the dehydration of D-fructose were systematically investigated. The catalyst could be regenerated through an ion-exchange method and a high yield was retained after being used five times. As a heterogeneous catalytic process, a possible reaction mechanism for the dehydration of D-fructose over Nafion-modified MCF catalysts was proposed.

Hierarchically tetramodal-porous zeolite ZSM-5 monoliths with template-free-derived intracrystalline mesopores

In this work, we report a unique synthesis of hierarchical zeolite ZSM-5 monoliths using polyurethane foam (PUF) as a rigid scaffold through a simple steam-assisted crystallization (SAC) method. The resultant monolithic ZSM-5 with a well crystalline structure possesses unique tetra-modal porosity (macropore/macropore/mesopore/micropore). The first modes of macroporosity (pore size of ∼33 μm) is formed after the removal of the PUF scaffolds. The second set of macropores with a size of 0.2–1.7 μm originate from the aggregation of ZSM-5 nanocrystals (crystal size of ∼500 nm) inside the macropores of the PUF scaffolds. The third level of porosity stems from the intracrystalline mesopores (∼53 nm) in each ZSM-5 crystal, along with the fourth intrinsic microporosity of zeolites. The mesopores are derived from the voids formed in the initial dry precursors, which are transformed and preserved as intracrystalline mesopores in each zeolite crystal. This type of ZSM-5 monolith possesses a high macroporosity (75.2%) and mechanical stability (1.2 MPa). The total surface area of the monolithic ZSM-5 is ∼226 m2 g−1 and the total pore volume is ∼0.21 cm3 g−1. The ZSM-5 monolith as a structured catalyst for methanol to propylene (MTP) conversion shows excellent catalytic performance with high methanol conversion (above 95%) and propylene selectivity (above 40%) at a high weight hourly space velocity (WHSV, 3.6 h−1). Importantly, the diffusion efficiency of catalyst is remarkably improved. After reaction for 5 h, the selectivity of propylene reaches a steady state.

Highly stable boron-modified hierarchical nanocrystalline ZSM-5 zeolite for the methanol to propylene reaction

A highly stable MTP (methanol to propylene) catalyst, boron-modified hierarchical nanocrystalline ZSM-5 zeolite, has been constructed by a facile salt-aided seed-induced route. The cooperative effect of its hierarchical structure and modified acidity gives rise to a significantly stable activity (725 h) even at a high WHSV (weight hourly space velocity) of 4.0 h−1.

Ag microparticles embedded in Si nanowire arrays: a novel catalyst for gas-phase oxidation of high alcohol to aldehyde

A novel catalyst of silver microparticles embedded in a silicon nanowire array support (Ag@SiNW) was prepared by an in situ electroless metal deposition method; it exhibited high selectivity and stability for gas-phase oxidation of high alcohol to its corresponding aldehyde.

Silica-immobilized Aquivion PFSA superacid: application to heterogeneous direct etherification of glycerol with n-butanol

We report the effective heterogenization of polymeric perfluorosulfonic acid (PFSA) Aquivion® resin in a silica network for the direct etherification of glycerol with aliphatic n-butanol. The Aquivion-silica composites, prepared by a template-free sol–gel method, presented a large specific surface area, affording highly accessible acid sulfonic groups. The textural and bulk/surface properties of the hybrid composites were characterized in-depth using TGA, acid–base titration, N2 adsorption–desorption, XRD, TEM, FTIR, Raman, CP-MAS NMR and XPS. The Aquivion-silica composites exhibited a high catalytic activity (91% n-butanol conversion) and selectivity (45% butyl glyceryl monoether yield) while they lowered the formation of by-product (6% dibutyl ether yield) as compared to benchmark homogeneous and heterogeneous acid catalysts. The catalyst was reusable and maintained a stable performance after six consecutive cycles.

Support effect in hydrogenation of methyl benzoate over supported manganese oxide catalysts

Abstract Manganese oxide supported on MgO, γ-Al 2 O 3 , SiO 2 , ZrO 2 , TiO 2 and SiO 2 -Al 2 O 3 catalysts were prepared. The effect of support on their catalytic behavior for hydrogenation of methyl benzoate to benzaldehyde was studied. The formation of toluene is suppressed on the supported catalysts due to the dilution of oxygen vacancies on the catalyst surface. The benzaldehyde yield of the supported catalysts follows the trend Mn/γ-Al 2 O 3 >Mn/TiO 2 >Mn/ZrO 2 >Mn/SiO 2 -Al 2 O 3 >Mn/SiO 2 >Mn/MgO. XRD measurements show that the Mn nitrate precursor is essentially transformed to highly dispersed MnO 2 on the supports at calcination and subsequently to MnO under reaction conditions with an exception of Mn/MgO. TPR and XPS analyses suggest that a strong interaction between manganese oxide and the γ-Al 2 O 3 support plays a positive role in the hydrogenation reaction.

A novel catalyst with high activity for polyhydric alcohol oxidation: nanosilver/zeolite film

A novel catalyst of silver nanoparticles over a zeolite film-coated copper grid (SZFC) has been fabricated via an in situ electrolytic method; it exhibited high catalytic activity and selectivity at a relatively low temperature for the partial oxidation of 1,2-propylene glycol to methyl glyoxal.

Aquivion®–carbon composites via hydrothermal carbonization: amphiphilic catalysts for solvent-free biphasic acetalization

One-pot hydrothermal carbonization of polysaccharides (i.e. guar gum or cellulose) with Aquivion® perfluorosulfonic superacid at 180 °C produced new amphiphilic Aquivion®–carbon composites. The materials stabilized dodecyl aldehyde/ethyleneglycol Pickering emulsions, and thus efficiently catalyzed the solvent-free biphasic acetalization reaction under moderate conditions with excellent reusability.

Simultaneous Ni Doping at Atom Scale in Ceria and Assembling into Well-Defined Lotuslike Structure for Enhanced Catalytic Performance

Oxide materials with redox capability have attracted worldwide attentions in many applications. Introducing defects into crystal lattice is an effective method to modify and optimize redox capability of oxides as well as their catalytic performance. However, the relationship between intrinsic characteristics of defects and properties of oxides has been rarely reported. Herein, we report a facile strategy to introduce defects by doping a small amount of Ni atoms (∼1.8 at. %) into ceria lattice at atomic level through the effect of microstructure of crystal on the redox property of ceria. Amazingly, a small amount of single Ni atom-doped ceria has formed a homogeneous solid solution with uniform lotuslike morphology. It performs an outstanding catalytic performance of a reduced T50 of CO oxidation at 230 °C, which is 135 °C lower than that of pure CeO2 (365 °C). This is largely attributed to defects such as lattice distortion, crystal defects and elastic strain induced by Ni dopants. The DFT calculation has revealed that the electron density distribution of oxygen ions near Ni dopant, the reduced formation energy of oxygen vacancy originated from local chemical effect caused by local distortion after Ni doping. These differences have a great effect on increasing the concentration of oxygen vacancies and enhancing the migration of lattice oxygen from bulk to a surface which is closely related to optimized redox properties. As a result, oxygen storage capacity and the associated catalytic reactivity has been largely increased. We have clearly demonstrated the change of crystal lattice and the charge distribution effectively modify its chemical and physical properties at the atomic scale.