利用手持技术探究催化剂对过氧化氢分解反应速率的影响

很多物质能催化过氧化氢分解反应，如酸、碱、过渡金属化合物、过氧化氢歧化酶等。但不同催化剂的催化效率不同。文中旨在通过手持技术探究二氧化锰、FeCl3溶液、CuS04溶液和CuCl2溶液对过氧化氢分解反应速率的影响，并比较它们的催化效率，同时探究了阳离子相同时，氯离子、硫酸根离子对过氧化氢分解反应的速率是否有影响。

过氧化氢催化分解反应装置的改进与实验内容的优化拓展

过氧化氢催化分解反应是经典的化学动力学实验,目前主要采用量气法测定过氧化氢分解反应的速率常数和半衰期。在分析总结现有实验装置不足的基础上,设计与改进了实验装置并应用于本校本科实验教学,改进装置获得国家实用专利授权。改进后,实验结果的准确性和重现性显著提高,重复操作与药品损失减少,实验成本降低,遵循绿色化学理念。同时,应用改进后的实验装置能够实现以初始速率法探究FeCl3催化过氧化氢分解反应的动力学特征,精确测定FeCl3催化过氧化氢分解反应级数、反应速率常数和活化能,拓展了过氧化氢催化分解反应的传统实验内容和实验方法,实现了对学生探究性思维和方法的高阶培养目标。

叔丁基过氧化物市场调研报告

概况 叔丁基过氧化物是有机过氧化物的一个重要分支,主要用作聚合反应的引发剂.叔丁基过氧化物包括叔丁基过氧化氢、二叔丁基过氧化氢、叔丁基过氧化苯甲酸酯、1,1-二叔丁基过氧基环己烷、1,1-二叔丁基过氧基-3,3,5-三甲基环乙烷和2,5-二甲基-2,5一二(叔丁基过氧基)己烷等.

一级反应数据非线性拟合的Excel方法

分析了通常处理一级反应实验数据的方法存在的缺陷,给出了使用Excel做非线性拟合的方法和实例.

单分子断键反应的理论研究

利用微扰理论和对称性规则 ,得到了单分子断键反应中反应物结构、过渡态和所断键之间的关系 .据此 ,对环丙基自由基及其正负离子的热开环反应和过氧化氢基态均裂反应作出预言 ,其中对环丙基自由基及其正负离子的热开环反应作出以下三方面的预言 :是否存在过渡态 ;产物的立体选择 ;反应的相对难易程度 .并分别使用UHF方法和CASSCF方法做势能面计算 。

Study on the Mechanisms for Baeyer-Villiger Oxidation of Cyclohexanone with Hydrogen Peroxide in Different Systems

The green and effective Baeyer-Villiger oxidation reaction of cyclohexanone for preparing e-caprolactone is of particular importance in the synthesis of new polymer materials. We have discussed here several mechanism types of Baeyer-Villiger oxidation of cyclohexanone with H2O2 in different reaction systems. Five main types have been addressed, i. e.： （1） the non-catalyzed reaction type, where the C=O of ketones is activated by H＋, which is electrolytically dissociated from H202 and H20, to improve the capability of C=O group for accepting the electron pairs; （2） the thermally activated radical reaction type, where the Criegee intermediate is produced via two steps of radical reaction with -OH attack, with much more hydroxyl radicals being excited in the presence of TS-1 zeolite; （3） the Bronsted acid catalysis reaction type, where both O-O moiety and C=O group could be activated by BriSnsted acid; （4） the solid Lewis acid catalyzed C=O of the substrate activation reaction type through enhancing the donor-acceptor interaction between the antibonding π＊c-o orbital of cyclohexanone and HOMO of Sn-containing zeolites; and （5） the solid Lewis acid catalyzed H202 to form Me-OOH oxidative species by converting the highest occupied molecular orbital （HOMO） of Ti-OOH into a singly occupied molecular orbital （SOMO）, making the O--O group highly electrophilic to attack the C--O of cyclohexanone during the Baeyer-Villiger oxidation process. In the end, we have also compared the different mechanisms and put forward our opinions on the development direction of catalytic materials aiming at eco-friendly Baeyer-Villiger oxidation of cyclohexanone in the years to come.

Prospect of vapor phase catalytic H2O2 production by oxidation of water

Vapor phase catalytic hydrogen peroxide production by oxidation of water is possible by coupling the reaction with oxidation of an organic sacrificial reductant. It is potentially a safer process than direct synthesis from H2 and O2. Based on mechanistic information available mostly for liquid phase catalytic processes, feasible reaction mechanisms for such coupled reactions are proposed based on which desirable catalyst properties are identified. It is found that the surface-adsorbed oxygen bond is an important parameter for identifying desirable catalysts. Thermodynamics can be used to identify the types of organic oxidation reactions that can couple with water oxidation such that H2O2 formation becomes thermodynamically favorable. Reactions such as epoxidation of alkenes and selective oxidation of alkanes to alcohols cannot provide sufficient thermodynamic driving force, whereas oxidation of alcohols to aldehydes and to acids can. Finally, further research is suggested to identify catalytic properties important for H2O2 decomposition and for coupling selective oxidation of organic compounds to oxidation of H2O in order to facilitate development of H2O2 production coupled with selective organic oxidation.

Enhanced electrocatalytic activity for H_2O_2 production by the oxygen reduction reaction: Rational control of the structure and composition of multi-walled carbon nanotubes

Hydrogen peroxide(H2O2)is a very useful chemical reagent,but the current industrial methods for its production suffer from serious energy consumption problems.Using high-activity and high-selectivity catalysts to electrocatalyze the oxygen reduction reaction(ORR)through a two-electron(2e^-)pathway is a very promising route to produce H2O2.In this work,we obtained partially oxidized multi-walled carbon nanotubes(MWCNTs)with controlled structure and composition by oxidation with concentrated sulfate and potassium permanganate at 40℃ for 1 h(O-CNTs-40-1).The outer layers of O-CNTs-40-1 are damaged with defects and oxygen-containing functional groups,while the inner layers are maintained intact.The optimized structure and composition of the partially oxidized MWCNTs ensure that O-CNTs-40-1 possesses both a sufficient number of catalytic sites and good conductivity.The results of rotating ring disk electrode measurements reveal that,among all oxidized MWCNTs,O-CNTs-40-1 shows the greatest improvement in hydrogen peroxide selectivity(from ~ 30% to ~ 50%)and electron transfer number(from ~ 3.4 to ~ 3.0)compared to those of the raw MWCNTs.The results of electrochemical impedance spectroscopy measurements indicate that both the charge-transfer and intrinsic resistances of O-CNTs-40-1 are lower than those of the raw MWCNTs and of the other oxidized MWCNTs.Finally,direct tests of the H2O2 production confirm the greatly improved catalytic activity of O-CNTs-40-1 relative to that of the raw MWCNTs.

Effect of calcination temperatures on photocatalytic H_(2)O_(2)-production activity of ZnO nanorods

Photocatalytic hydrogen peroxide(H_(2)O_(2))production from O_(2) and H2O is an ideal process for solar‐to‐chemical energy conversion.Herein,ZnO nanorods are prepared via a simple hydrothermal method for photocatalytic H_(2)O_(2) production.The ZnO nanorods exhibit varied performance with different calcination temperatures.Benefiting from calcination,the separation efficiency of photo‐induced carriers is significantly improved,leading to the superior photocatalytic activity for H_(2)O_(2) production.The H_(2)O_(2) produced by ZnO calcined at 300℃ is 285μmol L^(−1),which is over 5 times larger than that produced by untreated ZnO.This work provides an insight into photocatalytic H2O2 production mechanism by ZnO nanorods,and presents a promising strategy to H2O2 production.

Layered transition-metal hydroxides for alkaline hydrogen evolution reaction

Hydrogen is a promising sustainable energy to replace fossil fuels owning to its high specific energy and environmental friendliness.Alkaline water electrolysis has been considered as one of the most prospective technologies for large scale hydrogen production.To boost the sluggish kinetics of hydrogen evolution reaction(HER)in alkaline media,abundant materials have been designed and fabricated.Herein,we summarize the key achievements in the development of layered transition-metal hydroxides[TM(OH)x]for efficient alkaline HER.Based on the structure of TM(OH)x,the mechanism of synergistic effect between TM(OH)x and HER active materials is illuminated firstly.Then,recent progress of TM(OH)x-based HER catalysts to optimize the synergistic effect are categorized as TM(OH)x and active materials,including species,structure,morphology and interaction relationship.Furthermore,TM(OH)x-based overall water splitting electrocatalysts and electrodes are summarized in the design principles for high activity and stability.Finally,some of key challenges for further developments and applications of hydrogen production are proposed.

Multistage Extractive Reaction for Hydrogen Peroxide Production by Anthraquinone Process

The extractive reaction process of oxygen-working solution-water three-phase system for the production of hydrogen peroxide by the anthraquinone method was investigated in a sieve plate column of 50 mm in internal diameter. The oxidation reaction of anthrahydroquinone in the working solution with oxygen and the extraction of hydrogen peroxide from the working solution into aqueous phase occurred simultaneously in the countercurrent mode. The agitating effect caused by gaseous phase made the droplets of the dispersed phase become smaller, thus, increasing the liquid-liquid interfacial contact areas and resulting in the improvement of the mass transfer velocity. Results showed that the gas-agitation had a beneficial effect on the extraction of hydrogen peroxide from the working solution into the aqueous phase; the concentration of hydrogen peroxide in the raffinate decreased with the increase of the gaseous superficial velocities; and the concentration of H2O2 in the raffinate increased with the increase of the dispersed phase superficial velocity at the same superficial velocity of the gaseous phase. In the G-L-L extractive reaction process, with the increase of the gaseous superficial velocities, both the conversion of the anthrahydroquinone oxidation and the extraction efficiency of hydrogen peroxide first increased significantly, then increased gradually.

Synthesis of TS-1 Films on Porous Supports for Epoxidation ofAllyl Chloride by Hydrogen Peroxide

Titanium silicalite-1(TS-1)films were synthesized on stainless steel plate,glass slide and monolith supports via an in-situ hydrothermal method.Characterization data showed that the formation of TS-1 films was easier on the porous flat support with rough surface such as monolith than on the smooth non-porous supports like glass slide and stainless steel plate.The film on the monolith had the highest uniformity and smallest size of crystals.The catalytic property of monolithsupported film was tested for epoxidation of allyl chloride(ACH)by H2O2in a fixed bed reactor.Under the condition of a methanol(solvent)/ACH(90% )/H2O2(30% )ratio of 12:1:1,a LHSV of 1.35 h-1and a temperature of 318 K,the conversion of allyl chloride and the selectivity to epichlorohydrin reached 79% and 51% ,respectively.

Understanding surface charge effects in electrocatalysis.Part 2:Hydrogen peroxide reactions at platinum

Electrocatalytic activity is influenced by the surface charge on the solid catalyst.Conventionally,our attention has been focused on how the surface charge shapes the electric potential and concentration of ionic reactant(s)in the local reaction zone.Taking H_(2)O_(2)redox reactions at Pt(111)as a model system,we reveal a peculiar surface charge effect using ab initio molecular dynamics simulations of electrified Pt(111)-water interfaces.In this scenario,the negative surface charge on Pt(111)repels the O-O bond of the reactant(H_(2)O_(2))farther away from the electrode surface.This leads to a higher activation barrier for breaking the O-O bond.Incorporating this microscopic mechanism into a microkinetic-double-layer model,we are able to semi-quantitatively interpret the pH-dependent activity of H_(2)O_(2)redox reactions at Pt(111),especially the anomalously suppressed activity of H_(2)O_(2)reduction with decreasing electrode potential.The relevance of the present surface charge effect is also examined in wider scenarios with different electrolyte cations,solution pHs,crystal facets of the catalyst,and model parameters.In contrast with previous mechanisms focusing on how surface charge influences the local reaction condition at a fixed reaction plane,the present work gives an example in which the location of the reaction plane is adjusted by the surface charge.

Continuous Flow Reactor for Hydroxylation of Benzene to Phenol by Hydrogen Peroxide

The direct hydroxylation of benzene to phenol catalyzed by activated carbon-supported Fe （Fe/AC） in acetonitrile using H2O2 as the oxidant was studied in a continuous flow reactor. Results showed that the continuous operation could obtain high phenol yield of 28.1%, coupled with the turnover frequency of 3 h^-1, and high selectivity of 98% under mild condition. The catalyst was characterized by N2 adsorption/desorption, Boehm titration, X-ray photoelectron spectra, and Fourier transform infrared spectroscopy. It was observed that iron may interact with the carboxyl group forming iron-carboxylate like species, which act as the active phase. The apparent activation energy obtained by fitting an Arrhenius model to the experimental data was 13.4 kJ/mol. The reaction order was calculated to be about i, 0.2 for benzene and 0.7 for H202.

Computer Data Processing of the Hydrogen Peroxide Decomposition Reaction

Two methods of computer data processing, linear fitting and nonlinear fitting, are applied to compute the rate constant for hydrogen peroxide decomposition reaction. The results indicate that not only the new methods work with no necessity to measure the final oxygen volume, but also the fitting errors decrease evidently.

Hydroxylation of phenol with hydrogen peroxide catalyzed by Fe- and AIFe-Bentonite

The paper described pillarisations of natural bentonite from Pacitan East Java of Indonesia by using AI and Fe. Intercalation process by using surfactant molecule has also been carried out. Natural bentonite was intercalated with HDTMA-Br （hexadecyltrimethylammonium-bromide） 1, 5% solution before pillared with AI and Fe metal to give HDTMA-bentonite forms. The ratio of bentonite and intercalating agent or pillaring agent was 1 gr/50 mL. The mixture was agitated, and then the solid phase was washed with distilled water. Then it was dried and calcined at 450℃ for 4 hours. Their catalytic activity and selectivity were studied for phenol hydroxylation using tlzOz （30%）. The reaction condition of this reaction was as follows： ratio of phenol/ H202 = 1：1 （molar ratio）, concentration of phenol = 1 M, reaction temperature was 60℃, and ratio of catalyst/phenol was 1：10. The products were hydroquinone and cathecol.

Preliminary Study of Oxidative Stress in Human Hepatocellular Carcinoma and Adjacent Normal Liver Tissues

OBJECTIVE The antioxidative system in human hepatocellular carcinoma was investigated. METHODS The activities of cytosolic catalase (CAT), superoxide dismu-tase, glutathione peroxidase (GSH-Px), glutathione S-tranferase and levels of reduced glutathione, total protein thiols and malondialdehyde were assayed in 10 cases of hepatocellular carcinoma and adjacent normal liver. RESULTS Hepatoma tissues showed higher activities of CAT, GSH -Px and lower content of total antioxidative capacity compared to adjacent normal liver tissue (P<0.05). CONCLUSION These findings suggest that the antioxidative defense-related enzymes and antioxidants are largely regulated in hepatoma cells. However, the mechanism which is not clear requires further investigation.

Kinetics of 2-Methylbutene-2 Epoxidation with 2-Methylbutane Hydroperoxide

The kinetics of epoxidation of methylbutene with structurally identical methylbutane hydroperoxide was studied in the presence of a molybdenum catalyst. The analysis of the rate curves suggested the most probable scheme of the process. The revealed features of the process and its mathematical description make it possible to more competently design a reactor unit for the commercial production of isoprene according to the developed scheme. The main kinetic constants were calculated.

针式搜索在自催化反应解析中的应用(英文)

自催化反应一般比较复杂,其动力学模型往往未知。在其反应过程中获得的动力学-光谱数据矩阵可用迭代目标转换因子分析法(ITTFA)来解析。针式搜索被用来确定数据矩阵的化学秩及反应过程中所产生的中间体达到最大浓度的时间,并进一步构造ITTFA 中的初始迭代矢量。应用此方法,一组含有两个中间体的自催化反应的模拟数据得到了成功的解析。硫酸介质中高锰酸钾氧化过氧化氢的反应属于自催化反应,在线测得的该反应的动力学-光谱数据用针式搜索-ITTFA方法进行了解析,确定反应过程中存在2个中间体,获得了反应体系中各组分的动力学谱。

Oxidative desulfurization performance optimization of tert- amyl hydroperoxide

The desulphurization experiment of oil-soluble oxidant tert-amyl hydroperoxide with dibenzothiophene dissolved in decalin as model-oil was researched. Characterisation on oxidation product was made, and dibenzothiophene removal rate was computed. The influence factors of the oxidative reaction regent amount and the condtions of reaction temperature and reaction time were optimized and compared. The best reaction condition was reaction temperature 90℃, reaction time 3 h, ratio of oxygen to sulfur 4：1, catalyst amount 0.12 g. Dibenzothiophene removal rate reached 97% in this reaction condition.