TPA+-Mediated Conversion of Silicon Wafer into Preferentially-Oriented MFI Zeolite Film under Steaming

TPA^+-mediated conversion of silicon wafers into preferentially oriented siliceous MFI zeolite films is achieved by steam-assisted crystallization. Indeed, silicon wafers as the substrate are oxidized by TPAOH(aq) and therefore supplied as Si source for simultaneous crystallization of zeolite film

TPA+-Mediated Conversion of Silicon Wafer into Preferentially-Oriented MFI Zeolite Film under Steaming

TPA^+-mediated conversion of silicon wafers into preferentially oriented siliceous MFI zeolite films is achieved by steam-assisted crystallization. Indeed, silicon wafers as the substrate are oxidized by TPAOH(aq) and therefore supplied as Si source for simultaneous crystallization of zeolite film

Hierarchically Porous ZSM-5 Synthesized by Nonionic- and Cationic-Templating Routes and Their Catalytic Activity in Liquid-Phase Esterification

Hierarchically porous MFI zeolites (ZSM-5) have been synthesized by hydrothermal treatment in the presence of trialkoxysilylated-derivatives of nonionic poly(oxyethylene) alkyl ether or alkyl quaternary ammonium cation as mesopore-generating agent, along with tetrapropylammonium cation as zeolite structure-directing agent. Powder X-ray diffraction revealed that zeolites have been crystallized, and scanning electron microscopy showed rugged surface morphology that was quite different from conventional ZSM-5. The mesoporosity was confirmed by nitrogen adsorption-desorption measurement showing type IV isotherms with narrow distribution of mesopore diameters. The catalytic activity of these mesoporous ZSM-5 was tested in liquid-phase esterification of benzyl alcohol with hexanoic acid. The conversion of benzyl alcohol on mesoporous ZSM-5 prepared via cationic-templating route was almost 100%, being much higher than on mesoporous ZSM-5 prepared with silylated nonionic surfactant as well as on conventional ZSM-5 with no mesopores. The presence of Brønsted acid sites, together with the mesopores, was responsible for this catalytic conversion, as confirmed by pyridine adsorption monitored by in situ infrared and 27Al magic angle spinning nuclear magnetic resonance spectroscopy

The effect of lean methods and tools on the environmental performance of manufacturing organisations

Evidence suggests that lean methods and tools have helped manufacturing organisations to achieve operational excellence, and in this way meet both traditional and contemporary organisational objectives such as profitability, efficiency, responsiveness, quality, and customer satisfaction. However, the effect of these methods and tools on environmental performance is still unclear, as limited empirical research has been conducted in this field. This paper therefore investigates the impact of five essential lean methods, i.e. JIT, autonomation, kaizen/continuous improvement, total productive maintenance (TPM) and value stream mapping (VSM), on four commonly utilised measures for the compliance of environmental performance, i.e. material use, energy consumption, non-product output, and pollutant releases. A correlation analysis modelled the relationship and effect of these lean methods on the environmental performance of 250 manufacturing organisations around the world. Structural equation modelling (SEM) was used as a second pronged verification approach to ensure the validity of the results. The results indicate that TMP and JIT have the strongest significance on environmental performance, whereas kaizen/continuous improvement only showed an effect on the use of materials and release of pollutants. Autonomation and VSM did not show any impact on environmental performance. The research holds important implications for industrialists, who can develop a richer knowledge on the relationship between lean and green. This will help them formulate more effective strategies for their simultaneous or sequential implementation. The paper extends our knowledge in the lean and green field by helping us to establish and explain the given relationships between five of the most important and commonly used lean methods and the environmental performance of manufacturing organisations. No previous research had considered the studied lean methods and environmental measures of performance

Direct visualisation of carbon dioxide adsorption in gate-opening zeolitic imidazolate framework ZIF-7

The crystal structures of zeolitic imidazolate framework 7 (ZIF-7) under various CO2 pressures were studied by high-resolution neutron powder diffraction. CO2 adsorption in ZIF-7 is visualised and demonstrated to be primarily controlled by the benzimidazolate ligands via a gate-opening mechanism. Our results highlight the importance of pressure on the CO2 adsorption and the related structural framework responses in ZIF-7

Fabrication of hierarchical Lewis acid Sn-BEA with tunable hydrophobicity for cellulosic sugar isomerization

Lewis acid Sn-BEA catalysts with tunable morphology and hydrophobicity were successfully synthesized by the recrystallization of post-synthetic Sn-BEA in the presence of ammonium fluoride (NH4F) and tetraethylammonium bromide (TEABr). Three-dimensionally ordered mesoporous imprinted (3DOm-i) and nanocrystalline Sn-BEA catalysts with hydrophobic surface were synthesized for the first time by the method. This recrystallization method includes the dissolution of crystalline zeolite BEA by fluoride ions and the rearrangement of different types of silanol defects in the presence of TEABr. The method allows the final products to simultaneously inherit the morphology of their parent Al-BEA zeolites, and significantly reduce silanol defects within the catalysts. The Sn-BEA catalysts synthesized from the recrystallization method show largely enhanced catalytic performance for both glucose isomerization and bulky lactose isomerization in different solvents, which is presumably due to the hydrophobic surface and improved molecular transport property in the hierarchical zeolites. The recrystallization approach is a facile and reliable strategy to improve the hydrophobicity of zeolite catalysts with tunable morphologies ranging from nanocrystals to hierarchical structures.Chemical Engineerin

Crystal-Size Effects on Carbon Dioxide Capture of a Covalently Alkylamine-Tethered Metal-Organic Framework Constructed by a One-Step Self-Assembly

To enhance the carbon dioxide (CO2) uptake of metal-organic frameworks (MOFs), amine functionalization of their pore surfaces has been studied extensively. In general, amine-functionalized MOFs have been synthesized via post-synthetic modifications. Herein, we introduce a one-step construction of a MOF ([(NiLethylamine)(BPDC)]=MOFNH2; [NiLethylamine]2+=[Ni(C12H32N8)]2+; BPDC2-=4,4???-biphenyldicarboxylate) possessing covalently tethered alkylamine groups without post-synthetic modification. Two-amine groups per metal centre were introduced by this method. MOFNH2 showed enhanced CO2 uptake at elevated temperatures, attributed to active chemical interactions between the amine groups and the CO2 molecules. Due to the narrow channels of MOFNH2, the accessibility to the channel of CO2 is the limiting factor in its sorption behaviour. In this context, only crystal size reduction of MOFNH2 led to much faster and greater CO2 uptake at low pressures.open

Synthesis and applications of MOF - derived porous nanostructures

Metal organic frameworks (MOFs) represent a class of porous material which is formed by strong bonds between metal ions and organic linkers. By careful selection of constituents, MOFs can exhibit very high surface area, large pore volume, and excellent chemical stability. Research on synthesis, structures and properties of various MOFs has shown that they are promising materials for many applications, such as energy storage, gas storage, heterogeneous catalysis and sensing. Apart from direct use, MOFs have also been used as support substrates for nanomaterials or as sacrificial templates/precursors for preparation of various functional nanostructures. In this review, we aim to present the most recent development of MOFs as precursors for the preparation of various nanostructures and their potential applications in energy-related devices and processes. Specifically, this present survey intends to push the boundaries and covers the literatures from the year 2013 to early 2017, on supercapacitors, lithium-ion batteries, electrocatalysts, photocatalyst, gas sensing, water treatment, solar cells, and carbon dioxide capture. Finally, an outlook in terms of future challenges and potential prospects towards industrial applications are also discussed