甲醇气相氧化羰基化合成碳酸二甲酯的研究Ⅲ. 催化剂的失活再生

碳酸二甲酯 (ＤＭＣ)是一种对环境友好的绿色化学品 ,其洁净合成工艺的开发 ,已引起国内外研究者的广泛重视。真田等人[1 ] 对ＰｄＣｌ2 存在下ＣＯ和亚硝酸甲酯反应合成ＤＭＣ过程所用催化剂的失活原因和再生方法进行了研究 ,认为ＰｄＣｌ2 中的Ｃｌ被还原消除生成氯甲酸甲酯导致催化剂失活 ,并发现氯甲酸甲酯在ＤＭＣ合成中可使Ｐｄ催化剂再生和提高寿命。ＤＯＷ公司[2 ] 开发的气相氧化羰基化法催化剂ＣｕＣｌ2-ＫＣｌ ＡＣ易失活 ,该催化剂运行 50～ 1 0 0ｈ后需进行再生。再生时 ,于 1 2 0℃条件下通入 1 0 %ＨＣｌ Ｎ2 混合物 ,再生后…     

SnO2的制备及催化臭氧氧化活性

采用沉淀法制备了SnO2催化剂,以SnO2催化臭氧氧化降解糖蜜酒精废水脱色为探针反应,对催化剂的活性进行了评价.采用X射线衍射、红外光谱及热分析(TG-DSC)等技术对催化剂进行表征,研究了沉淀剂及焙烧温度等制备参数对SnO2催化臭氧氧化活性的影响.结果表明,SnO2催化剂对臭氧氧化降解糖蜜酒精废水脱色具有较高的催化活性,反应60 min后,糖蜜酒精废水的脱色率从单独臭氧氧化的43.04%提高到60.24%.沉淀剂对SnO2催化剂的活性影响很大,其中以氨水为沉淀剂制备的SnO2催化剂去羟基化反应程度高,所制得的催化剂活性最大.催化剂适宜的焙烧温度为723 K.SnO2吸附吡啶的红外光谱表明,催化剂表面存在L酸中心.臭氧在SnO2表面吸附的红外光谱表明,通过臭氧的末端氧原子与表面羟基及L酸中心成键,生成的活性氧可氧化降解糖蜜酒精废水.     

Preparation of Al2O3-supported nano-Cu2O catalysts for the oxidative treatment of industrial wastewater

Cuprous oxide (Cu₂O) nanoparticles supported on Al₂O₃ prepared using two different methods (hereafter referred to as catalyst I and II, respectively) were characterized by XRD and TEM. The catalytic activities of catalyst I and II during the treatment of industrial wastewater were then investigated. Specifically, the progress of the catalytic oxidation of industrial wastewater was observed by monitoring the time-dependent change in the chemical oxygen demand (COD) of industrial wastewater when the catalysts were applied. The results indicated that the catalytic activity of catalyst II was greater than that of catalyst I. Furthermore, under optimal conditions the COD removal efficiency was 94.59%. Finally, the mechanism by which the oxidative degradation of the industrial wastewater occurred could be explained based on a hydroxyl radical mechanism.     

Pozzolanic properties of a residual FCC catalyst during the early stages of cement hydration

The catalyst used in fluidized catalytic cracking (FCC) units of refineries after several recovery cycles in regeneration units, reduces its activity and it is partially substituted by new catalyst in the process. As it has a high silicon and aluminum oxides content, the pozzolanic properties of a Brazilian FCC spent residual catalyst, used in different substitution degrees to cement, were evaluated by three thermal analysis techniques during the early stages of hydration of a type II Portland cement. NCDTA curves show in real time that the residual catalyst, accelerates the stages of cement hydration. TG and DSC curves of respective pastes after 24 h of hydration evidence the pozzolanic activity of the waste, respectively, by the lower water mass loss during the dehydroxylation of the residual calcium hydroxide and by the lower dehydroxylation endothermal effect. Within the analyzed period, the higher is the cement substitution degree, the higher is the pozzolanic activity of the residual catalyst.     

Effect of electrode size on catalytic activity

In the field of catalyst research, synthesis innovations have allowed for the production of nanoparticle catalysts less than 2 nm in size. With this decrease in catalyst size, new questions have arisen with respect to the overall effect of size on catalytic activity. It is generally accepted that as catalyst particles decrease in size, the surface area to volume ratio of the catalyst is increased, resulting in higher catalytic performance. This paper introduces a novel technique for producing electrode structures with specific catalyst sizes. Through the use of electrochemical impedance spectroscopy and chronoamperometry, these different electrode sizes are compared with respect to the hydrogen evolution reaction. From this work, it is shown that for the given reaction, there exists a critical size at which catalytic activity begins to increase. A proposed explanation for the observed change in catalytic performance is introduced.     

Effects of binder, coking and regeneration on acid properties of H-mordenite during TDP reaction

The effects of binder, coking and regeneration on the acid properties of H-mordenite zeolite during toluene disproportionation reaction (TDP) have been investigated by solid-state ³¹P-MAS-NMR of various adsorbed phosphorous probe molecules in conjunction with elemental analysis by ICP-MS technique. A series of fresh, spent and regenerated mordenite-based commercial catalysts were examined and the results were also compared with binder-free H-mordenite zeolite and unformulated γ-alumina binder. It is found that parent H-mordenite zeolite possessed only Brønsted acidity, which is responsible for the observed catalytic activity. In contrast, the γ-Al₂O₃ binder exhibited only Lewis acidity and plays a minor role during the catalytic reaction. While the amount of strong Brønsted acid sites decreased rapidly during initial coking, it reached a plateau at a total coke content of ca. 7 wt%, corresponding to ca. 80% decrease in total acidity. That the catalyst remained active even under deep coke deposition (>7 wt%) condition indicated catalytic activity may be invoked by subsequent coking taking place on the external surface rather than intracrystalline channels of the zeolite catalyst. Furthermore, upon catalyst regeneration treatment, ca. 75% of the total acidity could be effectively recovered.     

Microparticle HZSM-5 zeolite as highly active catalyst for the hydration of cyclohexene to cyclohexanol

Microparticle HZSM-5 zeolite (MPZ) has been prepared without employing any organic templates, and used as a catalyst for the hydration of cyclohexene to synthesize cyclohexanol. MPZ exhibits better catalytic performance and superior settlement separation property than those of commercial HZSM-5 prepared by the traditional method using an organic template. The stability of MPZ has been investigated for a 1200-h test, and the regenerated performance of MPZ has also been investigated. The results show that although MPZ was reused for five recycles, the high cyclohexene conversion of 9.6 % and the high cyclohexanol selectivity of 96.8 % are still attained after the fifth regeneration. FT-IR, XRD and N₂ adsorption–desorption characterizations show that coke deposit on the surface and in the channels of MPZ is the main reason for the deactivation. ICP-AES, SEM–EDS and NH₃-TPD characterizations indicate that hydrothermal dealumination reduces the strong acidity and accelerates the catalyst deactivation. The spent catalyst by regeneration with H₂O₂ could be recovered to its initial high catalytic activity, due to the restored appropriate channels and exposed active sites.

     

Ionic Liquids as Performance Additives for Electroenzymatic Syntheses

Electroenzymatic syntheses combine oxidoreductase‐catalysed reactions with electrochemical reactant supply. The use of ionic liquids as performance additives can contribute to overcoming existing limitations of these syntheses. Here, we report on the influence of different water‐miscible ionic liquids on critical parameters such as conductivity, biocatalyst activity and stability or substrate solubility for three typical electroenzymatic syntheses. In these investigations promising ionic liquids were identified and have been used as additives for batch electrolyses on preparative scale for the three electroenzymatic systems. It was possible to improve the space‐time‐yield for the electrochemical regeneration of NADPH by a factor of three. For an amino acid oxidase catalysed resolution of a methionine racemate with ferrocene‐mediated electrochemical regeneration of the enzyme‐bound cofactor FAD a 50 % increase in space time yield and 140 % increase in catalyst utilisation (TTN) were achieved. Furthermore, for the chloroperoxidase‐catalysed synthesis of (R)‐phenylmethylsulfoxide with electrochemical generation of the required cosubstrate H₂O₂ the space time yield and the catalyst utilisation were improved by a factor of up to 4.2 depending on the ionic liquids used.     

Influence of Regeneration Conditions on the Activity of the Catalyst for Oxidative Chlorination of Ethylene

The possibility of thermochemical regeneration of an industrial batch of a spent and partially deactivated catalyst to improve its activity and selectivity in oxidative chlorination of ethylene to give 1,2-dichloroethane was studied.     

微乳液法制备的PtSn/C催化剂对乙醇的电催化氧化性能

以甲酸钠为还原剂,在水/triton X-100/乙二醇/环己烷的W/O型微乳液中制备PtSn/C催化剂.采用X射线衍射（XRD）分析催化剂的结构,循环伏安法和电化学阻抗谱法测试催化剂对乙醇的催化氧化性能.结果表明,微乳法制备的PtSn/C催化剂部分合金化,与Pt/C相比,PtSn/C对乙醇的电催化氧化活性有明显提高,具有更高的抗CO中毒能力.     

Titanium nitride catalyst cathode in a Li-air fuel cell with an acidic aqueous solution

TiN was used as an oxygen reduction reaction (ORR) catalyst in a Li-air fuel cell with a non-aqueous/acidic aqueous hybrid electrolyte. The electrochemical properties of the TiN based catalyst and the single cell were extensively investigated. It is suggested that TiN has considerable electrochemical catalytic activity for Li-air fuel cells in a weak acidic solution.     

Fe-Mn-Cu-Ce/Al2O3 as an efficient catalyst for catalytic ozonation of bio-treated coking wastewater: Characteristics,efficiency, and mechanism

It is important to develop a catalyst that has high catalytic activity and can improve the degradation efficiency of refractory organic pollutants in the catalytic ozonation process. In this study, Fe-Mn-Cu-Ce/Al₂O₃ was synthesised via impregnation calcination for catalytic ozonation of bio-treated coking wastewater. The physical and chemical characteristics of the catalysts were analysed using X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller nitrogen adsorption–desorption methods. The effects of catalyst dosage, pH, and reflux ratio on the degradation efficiency of wastewater were examined in laboratory-scale experiments. The chemical oxygen demand (COD) removal rate of bio-treated coking wastewater was estimated to be 52.76 % under optimal conditions. The experiments on the catalytic mechanism demonstrated that the surface hydroxyl formed by the Lewis acid sites on the surface of the catalyst can react with ozone as the active site forming the active oxygen (·OH, ·O₂^–, and ¹O₂), thereby efficiently degrading the organic pollutants in coking wastewater. Furthermore, a pilot-scale experiment on the catalytic ozonation of bio-treated coking wastewater was carried out using an Fe-Mn-Cu-Ce/Al₂O₃ catalyst, while the effects of the initial pollutant concentration, ozone concentration, and gas flow on the COD removal rate were studied on a pilot scale. It was found that the COD removal rate of the wastewater was ～ 60 % under optimal parameters. After the treatment, the wastewater steadily reached the coking wastewater discharge standard (COD < 80 mg/L), while the operating cost of catalytic ozonation reached ～ 0.032$/m³, thereby paving the way toward economic engineering applications. The COD degradation kinetics in the bio-treated coking wastewater followed pseudo-second-order kinetics. Three-dimensional fluorescence and gas chromatography–mass spectrometry revealed that macromolecular organic pollutants in the bio-treated coking wastewater were greatly degraded. In summary, Fe-Mn-Cu-Ce/Al₂O₃ exhibited good reusability, high catalytic activity, and low cost and has a wide application prospect in the treatment of coking wastewater.     

PtTe/C催化剂的制备及其对乙醇的电催化氧化性能

采用无机溶胶法制备了用于乙醇燃料电池的PtTe/C催化剂;利用X射线衍射仪分析了催化剂的结构,采用循环伏安法和电化学阻抗法测试了PtTe/C催化剂对乙醇的电催化氧化性能.结果表明,与商业Pt/C催化剂相比,PtTe/C催化剂对乙醇的催化氧化效率明显较高,可使乙醇氧化峰电流密度提高27%,且具有更高的抗CO中毒能力.     

载银纳米TiO2光催化降解水中的有机污物

载银纳米TiO2光催化降解水中的有机污物     

Reactivation of CoMo/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> hydrotreating catalysts with chelating agents

Effect of various chelating components, multibasic carboxylic acids and glycols, used to prepare hydrotreating catalysts on the activity regeneration of calcined hydrotreating catalysts was studied. Reactivated catalyst samples were tested in a model reaction of hydrodesulfurization of dibenzothiophene. It was shown that the treatment of calcined catalysts with the chelating components leads to an increase in the catalytic activity. The best catalytic characteristics are observed for the catalyst reactivated with a solution containing citric acid and triethylene glycol.     

A promising amendment for water splitters: Boosted oxygen evolution at a platinum,titanium oxide and manganese oxide hybrid catalyst

A hybrid catalyst composed of a platinum thin layer and modified with manganese oxide (MnOx) is recommended for the oxygen evolution reaction (OER). The Pt layer of the catalyst was physically sputtered onto a TiOx-coated Si substrate (this TiOx layer was sputtered inbetween the Si substrate and Pt layer to improve their adhesion and prevent their mutual diffusion). On top of the Pt layer, another thin TiOx layer (∼60 nm) was spun before the electrochemical deposition of MnOx. The investigation focused primarily to evaluate the impact of the catalyst’s annealing in oxygen atmosphere on its catalytic activity toward OER. Interestingly, before the modification with MnOx, a large catalytic enhancement both in activity (∼228 mV negative shift at 20 mA cm⁻² if compared to conventional bare Pt catalysts) and stability was achieved at the catalyst annealed at 600 °C toward OER in 0.5 M KOH. Surprisingly, the addition of MnOx to the catalyst synergized a boosted activity amplifying the negative shift to 470 mV at the same current density. Bunch of materials and electrochemical techniques were combined to reveal important remarks about the catalyst’s morphology, structure, composition and intrinsic activity which was attributed to electronic rather than geometric factors.     

HZSM-5在线提质生物油及催化剂失活机理分析

对不同使用时间的HZSM-5分子筛在线催化提质制取的生物油进行理化特性和成分分析,从生物油品质角度对HZSM-5的催化性能进行评价;并采用TG、BET、XRD、SEM和TEM等方法对失活的HZSM-5催化剂进行表征分析,探讨了HZSM-5催化提质生物油的失活机理,并进行再生研究。研究表明,HZSM-5分子筛可转化生物油中的酸类、醛类和酮类等"非期望"有机物,生成较多"期望"有机物,如酚类和芳烃类物质,降低生物油的氧含量及酸性,提高生物油的热值;HZSM-5使用80 min后,生物油品质明显变差,催化剂活性明显降低;失活催化剂上沉积的焦炭主要呈纤维状,同时,还存在少量石墨状焦炭,焦炭总量达14.12%,且使用过程中催化剂的比表面积和孔容均下降,晶粒的团聚现象加剧,结晶度下降;在催化提质过程中,在孔道内生成的石墨状焦炭及在表面形成的纤维状焦炭大量覆盖活性位点,使得催化剂失活。经550℃再生后,催化剂可恢复催化性能。     

Characterization of the Isochromen-4-yl-gold(I) Intermediate in the Gold(I)-Catalyzed Glycosidation of Glycosyl ortho-Alkynylbenzoates and Enhancement of the Catalytic Efficiency Thereof

Gold standard: The title gold complex was characterized unambiguously as an important intermediate in the title reaction. Protonolysis of this vinyl gold(I) complex was critical for regeneration of the active gold(I) species for the catalytic cycle, and use of a protic acid co-catalyst significantly lowered the required catalyst loading to 0.5?mol?%.     

Well‐Dispersed Pt Cubes on Porous Cu Foam: High‐Performance Catalysts for the Electrochemical Oxidation of Glucose in Neutral Media

The investigation of highly efficient catalysts for the electrochemical oxidation of glucose is the most critical challenge to commercialize nonenzymatic glucose sensors, which display a few attractive superiorities including the sufficient stability of their properties and the desired reproducibility of results over enzyme electrodes. Herein we propose a new and very promising catalyst: Pt cubes well‐dispersed on the porous Cu foam, for the the electrochemical oxidation reaction of glucose in neutral media. The catalyst is fabricated in situ on a homemade screen‐printed carbon electrode (SPCE) substrate through initially synthesizing the three‐dimensional (3D) porous Cu foam using a hydrogen evolution assisted electrodeposition strategy, followed by electrochemically reducing the platinic precursor simply and conveniently. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) proofs demonstrate that Pt cubes, with an average size (the distance of opposite faces) of 185.1 nm, highly dispersed on the macro/nanopore integrated Cu foam support can be reproducibly obtained. The results of electrochemical tests indicate that the cubic Pt‐based catalyst exhibits significant enhancement on the catalytic activity towards the electrooxidation of glucose in the presence of chloride ions, providing a specific activity 6.7 times and a mass activity 5.3 times those of commercial Pt/C catalysts at ?0.4 V (vs. Ag/AgCl). In addition, the proposed catalyst shows excellent stability of performance, with only a 2.8 % loss of electrocatalytic activity after 100 repetitive measurements.     

Electrocatalytic properties of multiwalled carbon nanotubes-based nanocomposites for oxygen electrodes

Metals (platinum, nickel, and lead) and oxides (manganese dioxide and molybdenum, chromium, cobalt, and niobium oxides) were deposited onto multiwalled carbon nanotubes by chemical and electrochemical methods. The resulting nanocomposites were tested as oxygen electrode materials for electrochemical power sources with alkaline electrolytes. A correlation was revealed between the catalytic activity of oxygen electrodes manufactured from composites based on carbon nanotubes with catalyst deposited, on the one hand, and the coefficient a in the Tafel equation for the oxygen evolution reaction on this catalyst, on the other. A possibility of predicting and evaluating the catalytic properties of oxygen electrode materials for power sources was suggested.