Preparation and characterization of transition metal-modified lacunary Keggin 11-tungstophosphates supported on carbon

Transition metal-modified lacunary Keggin heteropolycompounds [PW₁₁O₃₉M]⁵⁻, with M = Ni²⁺, Co²⁺, Cu²⁺, or Zn²⁺, were synthesized and characterized. These heteropolycompounds were used to prepare the carbon-supported catalysts. Both the heteropolycompounds and the carbon-supported catalysts showed FT-IR spectra with the characteristic bands of these compounds and provided an indirect measure of the interaction strength between M and the oxygen of the central tetrahedron group of the Keggin structure. The anion decomposition of the modified compounds takes place at equal or lower temperature than that of the bulk and supported parent lacunary [PW₁₁O₃₉]⁷⁻ anion. The species present on the support surface may be highly dispersed as a non-crystalline form, as a result of the interaction with the support surface groups. The activity of the synthesized catalysts in isopropanol dehydration, reflecting their acidity, increases as the reduction temperature of the decomposition products of the heteropolycompounds decreases. It may be assumed that the generation of acid sites is a result of the interaction of hydrogen, donated by isopropanol during its decomposition, with the M cation, leading to M reduction and protons.     

Photocatalytic Oxidation of Isopropanol in Aqueous Solution Using Perovskite‐Structured La2Ti2O7

This study is focused on the application of a highly‐doped layered perovskite, La₂Ti₂O₇, as the photocatalyst for the photocatalytic decomposition of isopropanol (IPA). The La₂Ti₂O₇ powder prepared by solid state reaction was characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), UV‐Vis diffuse reflectance spectrophotometry (UV‐DRS), X‐ray photoelectron spectroscopy (XPS), and zeta potential. The temporal behavior of the photocatalytic decomposition of IPA in aqueous solution by the UV/La₂Ti₂O₇, with a photoreactor operated in a recirculation mode, was studied under various conditions including solution pH, light intensity, and La₂Ti₂O₇ loading. The decomposition of IPA in aqueous solution by La₂Ti₂O₇ photocatalytic processes was found to be technically feasible. A kinetic equation was developed for modeling the photocatalytic decomposition of IPA by the UV/La₂Ti₂O₇ photocatalytic processes.     

UDCaT-4: a novel mesoporous superacid catalyst in the selective synthesis of 4,4′-diisopropylbiphenyl by the isopropylation of biphenyl

A novel superacidic mesoporous catalyst UDCaT-4 was developed in this laboratory, which has been used in the alkylation of biphenyl with isopropanol. UDCaT-4 is a synergistic combination of persulfated alumina and zirconia with hexagonal mesoporous silica. 4,4′-Diisopropylbiphenyl (DIPB) has been increasingly used as an intermediate for manufacturing polymers and films possessing high heat resistance and strength. A variety of solid acid catalysts, especially zeolites, are reported for the alkylation of biphenyl to make DIPB but all of them e.g. mordenites, ZSM-5, H-β etc. suffer from coke formation and require regeneration within a few hours of time-on-stream. We report the efficacy of UDCaT-4, which exhibits tremendous stability, activity and selectivity in the vapor phase isopropylation of biphenyl with isopropanol to DIPB. A systematic investigation of the effects of various operating parameters is done. Furthermore, a mathematical model is developed to describe the reaction kinetics which is validated with experimental results.     

Achieving high electrocatalytic performance towards isopropanol electrooxidation based on a novel N-doping carbon anchored Pd3Fe alloy

Isopropanol is regarded as one of the most promising anodic electrooxidation candidates for direct alcohol fuel cells. However, developing the efficacious electrocatalysts remains the critical issue in the propelling of isopropanol electrooxidation. In this study, a good electrocatalyst combined with the benefits of a novel N-doping carbon support (CN support) and Pd-based alloy nanoparticles (Pd₃Fe anchoring on CN support, Pd₃Fe/CN), was successfully prepared and estimated. Electrochemical results indicate that the as-obtained Pd₃Fe/CN electrocatalyst possesses larger electrochemical active surface area, higher activity, better anti-CO poisoning and superior stability compared to Pd/C towards isopropanol electrooxidation. This work would propose a good electrocatalyst for the development of isopropanol electrooxidation.     

The development of high performance P84 co-polyimide hollow fibers for pervaporation dehydration of isopropanol

Probably because of material and fabrication limitations, most previously developed hollow fibers were lack of high performance for pervaporation dehydration applications. In this paper, we have successfully developed integrally skinned BTDA-TDI/MDI (P84) co-polyimide hollow fibers for pervaporation dehydration of isopropanol (IPA), which have impressive flux and selectivity towards water. The effects of spinning conditions such as air gap distance, coagulation temperature, and dope/bore fluid flow rates on membrane formation, morphology and pervaporation performance have been determined. Even though spinning conditions affect membrane separation performance, it is found that silicone rubber coating and heat treatment play much more important roles on performance enhancement. Not only can the silicone rubber coating effectively seal the membrane defects, but also triple the selectivity because of its nature of high water permeability while its hydrophobic property does not dominate. A tremendous increase in separation factor/selectivity (20-100 times) is observed after a heat treatment at . The newly developed P84 hollow fibers after heat treatment have a flux of and a separation factor of 10 585 for dehydration of 85/15 (w/w) IPA/water mixture at .     

Synthesis,characterization and application of PVA/ionic liquid mixed matrix membranes for pervaporation dehydration of isopropanol

In this study,polyvinyl alcohol (PVA)-ionic liquid (IL) membranes were prepared for the separation of isopropylalcohol (IPA)-water azeotropic mixtures by pervaporation.PVA-IL composite membranes were prepared by simple solvent evaporation method using four ILs,viz.,1-n-butyl-3-methylimidazolium chloride (BMIMCl),1-hexyl-3-methylimidazolium chloride (HMIMCl),1-hexyl-3-methylimidazolium tetrafluoroborate (HMIMBF4)and 1-octyl-3-methylimidazolium chloride (OMIMCl).Three ILs were used to study the effect of alkyl chain on the pervaporation performance.The study had focused on the effect feed water concentration from 10％-40％and effect of feed temperature from 50-80 ℃.Physiochemical properties of all the membranes were studied using Fourier transform infrared spectroscopy (FTIR),scanning electron microscopy (SEM) and contact angle measurement.The Arrhenius activation energies for permeation were estimated to be in the range 4-12 kJ.mol-1 from the temperature dependent permeation values.     

Deactivation mechanism of beta-zeolite catalyst for synthesis of cumene by benzene alkylation with isopropanol

The alkylation of benzene with isopropanol over beta-zeolite is a more cost-effective solution to cumene production.During the benzene alkylation cycles,the cumene selectivity slowly increased,while the benzene conversion presented the sharp decrease due to catalyst deactivation.The deactivation mechanism of beta-zeolite catalyst was investigated by characterizing the fresh and used catalysts.The XRD,SEM and TEM results show that the crystalline and particle size of the beta-zeolite catalyst almost remained stable during the alkylation cycles.The drop in catalytic activity and benzene conversion could be explained by the TG,BET,NH3-TPD and GC-MS results.The organic matters mainly consisted of ethylbenzene,p-xylene and 1-ethyl-3-(1-methyl) benzene produced in the benzene alkylation deposited in the catalyst,which strongly reduced the specific surface area of beta-zeolite catalyst.Moreover,during the reaction cycles,the amount of acidity also significantly decreased.As a result,the catalyst deactivation occurred.To maintain the catalytic performance,the catalyst regeneration was carried out by using ethanol rinse and calcination.The deactivated catalyst could be effectively regenerated by the calcination method and the good catalytic performance was obtained.     

Improvement of separation process of synthesizing MIBK by the isopropanol one-step method

The separation process of synthesizing MIBK (methyl isobutyl ketone) by an isopropanol one-step method, in which the multi-component mixture contains AC (acetone), IPA (isopropanol), water, MIBK, MIBC (methyl isobutyl carbinol), DIBK (di-isobutyl ketone), etc., was studied. As a high-purity of MIBK over 99.5 wt% is required in industry, the development of an effective separation method is urgent. In this work, first, by means of VLE (vapor-liquid equilibrium) experiments and PROII simulation, the possible azeotropes formed in the investigated system were tested. Then, the separation process was simulated with the result that the calculated and designed values were in good agreement, which indicated that the calculated results were reliable. On this basis, the original separation process was improved. In the original separation process, the yield of MIBK for a concentration of MIBK over 99.5 wt% was small, only 32.5%. In the improved separation process (step two), two columns (one extractive distillation column and the other solvent recovery column) were added and some simplification was made so as to recycle MIBK. In this case the yield of MIBK was 91.7%. Moreover, about 27.6% water stream per kilogram MIBK product is saved.     

Dehydration of isopropanol by PVA-APTEOS/TEOS nanocomposite membranes

In the present work, dehydration of isopropanol was investigated by novel organic-inorganic nanocomposite membranes which were prepared through sol-gel reaction of polyvinyl alcohol (PVA) with γ-aminopropyl-triethoxysilane (APTEOS) and tetraethoxysilane (TEOS). The PVA chains were crosslinked by mixing silane coupling agents. This reaction between polymer chains and silanols agents could control degree of swelling of the nanocomposite membranes in aqueous isopropanol (IPA) solutions. The membranes were characterized by SEM and ATIR. Effects of APTEOS content in the membranes, feed concentration and temperature on pervaporation (PV) performance were investigated. It was found out that separation factor and permeation flux increase with increasing APTEOS content in the membranes. Arrhenius-type relationship was used for describing the temperature dependence of permeation flux. It was also found out that separation factor decreases with increasing temperature.     

异丙醇在硅碱性腐蚀液中的作用

在硅单晶的碱性腐蚀过程中,往往由于碱性腐蚀液对单晶硅的腐蚀速率过快,从而增大了硅单晶片表面的粗糙度。异丙醇有着减缓腐蚀速率的功效因而降低了硅单晶片表面的粗糙度。主要讨论了异丙醇在碱性腐蚀液中的作用原理并对腐蚀实验结果做了分析。