Hualong Xu

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.

Controllable fabrication of uniform core–shell structured zeolite@SBA-15 composites

Mesoporous core–shell composites with large-pore silica shells are highly desired for a broad spectrum of applications. We report an ultra-dilute liquid-phase coating strategy in an acidic medium for controllable synthesis of uniform micro/mesoporous core–shell composites zeolite@SBA-15 comprising zeolite cores and mesoporous silica SBA-15 shells using triblock compolymer Plunoric P123 as a template. Structural characterizations show that the core–shell composites possess tunable specific surface areas (115–228 m2 g−1), large pores (∼7.0 nm in diameter) with plenty of mesotunnels (∼3.0 nm) from silica shells, original crystalline zeolite frameworks, and opened junctions between micropores and mesopores. The silica shells have ordered 2-D hexagonal mesopore channels, most of which are annularly parallel (fingerprint-like arrangement) to the anisotropic zeolite faces. The shell-thickness is crystal face-dependent, which could be facilely tuned in the range of 30–45 and 40–120 nm on a pinacoids/dome faces and b pinacoids of a zeolite single-crystal, respectively. Moreover, the synthesis parameters such as MgSO4 additive, stirring rate, acidity, temperature and reaction time show great influences on the formation of uniform core–shell composites. Post-hydrothermal treatment at 100 °C has been for the first time adopted to improve mesostructural regularity of the core–shell composites. A scheme regarding surface-induced micellization and hydrothermal rearrangement of mesostructured silica shells in the coating process is proposed to illustrate the formation of core–shell composites. The core–shell composite HZSM-5@SBA-15 (HZ@S15) was employed as a catalyst for methanol to propylene (MTP) conversion, and shows excellent catalytic performance with high methanol conversion (∼98%) and propylene to ethylene (P/E) ratio (∼10.7) as well as propylene selectivity (∼39%).

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.

Formation and photocatalytic properties of nanocomposite films containing both tetracobalt Dawson-derived sandwich polyanions and tetracationic porphyrins.

Films based on electrostatic interactions between tetracationic zinc porphyrins, ZnOEP(py)(4)(4+) or ZnTMePyP(4+), and the tetracobalt Dawson-derived sandwich polyanion αββα-[Co(4)(H(2)O)(2)(P(2)W(15)O(56))(2)](16-) are formed by the so-called layer-by-layer method. These films have been characterized by UV-visible absorption spectroscopy, atomic force microscopy and electrochemistry. The composition of the film was measured by X-ray photoelectron spectrum (XPS). The XPS data confirm the presence of the expected elements. The photocatalytic properties of these films have been also studied for the reduction of silver and gold ions. Indeed, in these systems, porphyrins can be excited by visible light and then play the role of photosensitizers able to give electrons to POM known to be good catalysts. Silver nanowires and gold nanosheets have been obtained.

A facile route to cage-like mesoporous silica coated ZSM-5 combined with Pt immobilization

Uniform core–shell composites with cage-like mesoporous silica (CmesoSiO2) shells and zeolite HZSM-5 cores have been synthesized by a facile acid-catalyzed sol–gel coating process. The mesoporous silica shells are uniform and coated on the anisotropic HZSM-5 crystal faces, and the shell-thicknesses can be tuned from 25 to 70 nm. The core–shell composites possess a high surface area (∼862 m2 g−1) and pore volume (∼0.66 cm3 g−1), large pore sizes (3.2–8.2 nm) and unchanged zeolite micropore properties. The silica shells are composed of cage-like mesopores and entrances (ranging from 3.2 to 8.2 nm) as well as a plenty of micropores. Pt nanocatalysts with an average particle size of ∼3.2 nm have been successfully encapsulated into the micropores and partial mesopores of the cage-like silica shells. The catalytic oxidation of toluene shows that the Pt/HZ@CmesoSiO2 composite presents an equivalent activity for toluene combustion at the light-off temperature of ∼195 °C (T50%) relative to the mixture catalyst (198 °C of T50%), but more excellent catalytic durability without activity loss (193 °C of T50%) after a 100 h test.

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.