Enhanced Stability of Dimethyl Ether Carbonylation through Pyrazole Tartrate on Tartaric Acid-Complexed Cobalt-Iron-Modified Hydrogen-Type Mordenite.

In this study, pyrazole tartrate (Pya·DL) and tartaric acid (DL) complexed with cobalt-iron bimetallic modified hydrogen-type mordenite (HMOR) were prepared using the ion exchange method. The results demonstrate that the stability of the dimethyl ether (DME) carbonylation reaction to methyl acetate (MA) was significantly improved after the introduction of Pya·DL to HMOR. The Co∙Fe∙DL-Pya·DL-HMOR (0.8) sample exhibited sustainable stability within 400 h DME carbonylation, exhibiting a DME conversion rate of about 70% and MA selectivity of above 99%. Through modification with the DL-complexed cobalt-iron bimetal, the dispersion of cobalt-iron was greatly enhanced, leading to the formation of new metal Lewis acidic sites (LAS) and thus a significant improvement in catalysis activity. Pya·DL effectively eliminated non-framework aluminum in HMOR, enlarged its pore size, and created channels for carbon deposition diffusion, thereby preventing carbon accumulation and pore blockage. Additionally, Pya·DL shielded the Bronsted acid sites (BAS) in the 12 MR channel, effectively suppressing the side reactions of carbon deposition and reducing the formation of hard carbon deposits. These improvements collectively contribute to the enhanced stability of the DME carbonylation reaction.

Enhancing the dimethyl ether carbonylation performance over hydrogen-type mordenites modified by pyrazole hydrochloride.

Hydrogen-type mordenite (HMOR) modified with pyrazole hydrochloride (Pya·HCl) was prepared by the ion exchange method. The results showed that Pya·HCl introduction significantly improved the activity and stability of HMOR in the carbonylation reaction of dimethyl ether (DME) to methyl acetate (MA). Small pyrazole ions (HPya+) entered into the twelve-membered ring (12-MR) pores of HMOR and selectively replaced part of the Brønsted acid (BAS), thus suppressing the formation of carbon deposits. The modified HMOR presented a larger specific surface area and pore volume, which provided larger channels for molecular diffusion. Additionally, non-framework aluminum was removed by the acidic Pya·HCl solution, resulting in the formation of mesopores, which facilitated the migration of carbon-deposited species from the inside of the zeolite to the outside.

Fabrication of layered Fe2P-Cd0.5Zn0.5S nanoparticles with a reverse heterojunction for enhanced photocatalytic hydrogen evolution.

In this work, a novel two-dimensional (2D) layered Fe2P modified Cd0.5Zn0.5S (CZS) nanoparticles composites were successfully developed by an environmentally friendly solvothermal method. The Fe2P-CZS photocatalysts were used for noble-metal-free photocatalytic H2 generation under visible light. The rate of H2 evolution of 13 wt% Fe2P-CZS was 24.84 mmol·g-1·h-1, which was 37.6 times that of CZS (0.66 mmol·g-1·h-1). The formation of the 2D-0D reverse heterojunction in the Fe2P-CZS composite photocatalyst improved the transport and separation of photogenerated electron-hole pairs and optimized the kinetics of hydrogen evolution. Compared with Fe2P particles, the layered Fe2P cocatalysts had higher conductivity and lower hydrogen evolution overpotential.

Recent Developments of Graphene Oxide-Based Membranes: A Review.

Membrane-based separation technology has attracted great interest in many separation fields due to its advantages of easy-operation, energy-efficiency, easy scale-up, and environmental friendliness. The development of novel membrane materials and membrane structures is an urgent demand to promote membrane-based separation technology. Graphene oxide (GO), as an emerging star nano-building material, has showed great potential in the membrane-based separation field. In this review paper, the latest research progress in GO-based membranes focused on adjusting membrane structure and enhancing their mechanical strength as well as structural stability in aqueous environment is highlighted and discussed in detail. First, we briefly reviewed the preparation and characterization of GO. Then, the preparation method, characterization, and type of GO-based membrane are summarized. Finally, the advancements of GO-based membrane in adjusting membrane structure and enhancing their mechanical strength, as well as structural stability in aqueous environment, are particularly discussed. This review hopefully provides a new avenue for the innovative developments of GO-based membrane in various membrane applications.

Fabrication and Water Treatment Application of Carbon Nanotubes (CNTs)-Based Composite Membranes: A Review.

Membrane separation technology is widely explored for various applications, such as water desalination and wastewater treatment, which can alleviate the global issue of fresh water scarcity. Specifically, carbon nanotubes (CNTs)-based composite membranes are increasingly of interest due to the combined merits of CNTs and membrane separation, offering enhanced membrane properties. This article first briefly discusses fabrication and growth mechanisms, characterization and functionalization techniques of CNTs, and then reviews the fabrication methods for CNTs-based composite membranes in detail. The applications of CNTs-based composite membranes in water treatment are comprehensively reviewed, including seawater or brine desalination, oil-water separation, removal of heavy metal ions and emerging pollutants as well as membrane separation coupled with assistant techniques. Furthermore, the future direction and perspective for CNTs-based composite membranes are also briefly outlined.

Incorporation of zinc for fabrication of low-cost spinel-based composite ceramic membrane support to achieve its stabilization.

In order to reduce environment risk of zinc, a spinel-based porous membrane support was prepared by the high-temperature reaction of zinc and bauxite mineral. The phase evolution process, shrinkage, porosity, mechanical property, pore size distribution, gas permeation flux and microstructure were systematically studied. The XRD results, based on a Zn/Al stoichiometric composition of 1/2, show a formation of ZnAl2O4 structure starting from 1000°C and then accomplished at 1300°C. For spinel-based composite membrane, shrinkage and porosity are mainly influenced by a combination of an expansion induced by ZnAl2O4 formation and a general densification due to amorphous liquid SiO2. The highest porosity, as high as 44%, is observed in ZnAl4 membrane support among all the investigated compositions. Compared with pure bauxite (Al), ZnAl4 composite membrane support is reinforced by ZnAl2O4 phase and inter-locked mullite crystals, which is proved by the empirical strength-porosity relationships. Also, an increase in average pore diameter and gas flux can be observed in ZnAl4. A prolonged leaching experiment reveals the zinc can be successfully incorporated into ceramic membrane support via formation of ZnAl2O4, which has substantially better resistance toward acidic attack.

Environment-oriented low-cost porous mullite ceramic membrane supports fabricated from coal gangue and bauxite.

Porous mullite ceramic supports for filtration membrane were successfully fabricated via recycling of coal gangue and bauxite at sintering temperatures from 1100 to 1500°C with corn starch as pore-forming agent. The dynamic sintering behaviors, phase evolution, shrinkage, porosity and pore size, gas permeation flux, microstructure and mechanical property were systematically studied. A unique volume-expansion stage was observed at increased temperatures from 1276 to 1481°C caused by a mullitization-crystal-growth process. During this stage, open porosity increases and pore size distributions broaden, which result in a maximum of nitrogen gas flux at 1400°C. The X-ray diffraction results reveal that secondary mullitization took place from 1100°C and the major phase is mullite with a content of ∼84.7wt.% at 1400°C. SEM images show that the as-fabricated mullite supports have a porous microstructure composed of sintered glassy particles embedded with inter-locked mullite crystals, which grew gradually with increasing temperature from rod-like into blocky-like morphologies. To obtain mullite membrane supports with sufficient porosity and acceptable mechanical strength, the relationship between porosity and mechanical strength was investigated, which was fitted using a parabolic equation.

[Determination of molybdenum in supported catalysts by ICP-AES].

The supported Mo catalysts were pretreated using hydrofluoric acid. Then Mo was determined by inductively coupled plasma atomic emission spectrometry(ICP-AES). In the present method, the detection limit of Mo was 8.220 ng x mL(-1), the recovery of standard addition was 102.6%-104.3%, the relative standard deviation (n = 11) was less than 0.860%. The method is efficient, accurate, and easy to operate. Molybdenum in supported catalysts, which were prepared under different conditions, was determined by this method. The results showed that the content of Mo in supported catalysts decreased after preparation. The decreases in the content of Mo were different when the active component concentrations in impregnation solution, and the calcination temperature, changed.

[Pretreatment of supported Wacker catalysts and the determination of palladium and copper].

The supported Wacker catalysts were pretreated with two different methods. Then copper and palladium were determined by inductively coupled plasma atomic emission spectrometry(ICP-AES). The results showed that the best pretreatment method is burning-acid dissolving. With this method, the detection limits of Pd and Cu were 3.127 and 2.548 ng x mL(-1), the recoveries of standard addition of Pd and Cu were 96.26% and 94.82%, and the relative standard deviations (n=11) of Pd and Cu were less than 1.237% and 1.354%, respectively. The method is efficient, accurate, and easy to operate. Pd and Cu in supported Wacker catalysts, which were sampled before calcination, after calcination and after reaction, were determined by this method, and the contents were compared with calculated values. The percentages were larger than 96.4% and 96.6% respectively. It is considered that the active components did not decrease in preparation and reaction.