CO气相合成草酸二乙酯催化剂性能评价

考察了Al2O3载体的类型和形状、活性组分Pd的负载量、活性组分Pd和助催化剂Fe之比对工业原料CO气相催化合成草酸二乙酯(DEO)反应的影响。结果表明,当Pd的负载量为1%～5%、Pd/Fe为0.2～2.0(mol比)、条状α-Al2O3为载体时,催化剂的性能优良,在此条件下,草酸二乙酯的最大收率可达60%, CO转化率可达63%,草酸二乙酯选择性可达98%。     

CO气相氧化偶联制草酸二乙酯催化剂研究

利用化学吸附仪、ＸＲＤ、ＸＰＳ、ＥＰＭＡ、ＳＥＭ等技术,对ＣＯ气相偶联制草酸二乙酸催化剂的比表面,孔分布,晶相,反应前后催化剂活性组分在表面和中心的价态对比及活性组分与助剂的分布进行了分析表征和反应机理探讨。研究表明小比表面大孔径的率剂反应效果好,在整个反应过程中催化剂活性组分Ｐｄ元素Ｐｄ＝Ｐｄ＾＋２,通过与亚硝酸乙酯及ＣＯ的反应来改变Ｐｄ的价态,反应过程中催化剂的成分变化和迁移与氧化还原“共催化     

钌(Ⅱ)-邻菲咯啉-有机酸-Ce(Ⅳ)偶合化学发光反应及其应用研究

本文以16种有机酸为研究对象, 系统地研究了钌(Ⅱ)-邻菲咯啉-有机酸-Ce(Ⅳ)偶合化学发光反应。结果表明, 化学发光强度与含有羰基或羟基的有机酸的浓度在一定浓度范围内具有良好的线性关系, 据此建立了羰基和羟基羧酸的化学发光分析法, 提出了偶合化学发光反应机理。方法用于草酸二乙酯和人体尿液中草酸的测定, 获得满意的结果。     

Precipitation of plutonium oxalate from homogeneous solutions

A method for the precipitation of plutonium(IV) oxalate from homogeneous solutions using diethyl oxalate is reported. The precipitate obtained is crystalline and easily filterable with yields in the range of 92–98% for precipitations involving a few mg to g quantities of plutonium. Decontamination factors for common impurities such as U(VI), Am(III) and Fe(III) were determined. TGA and chemical analysis of the compound indicate its composition as Pu(C₂O₄)₂·6H₂O. Data are obtained on the solubility of the oxalate in nitric acid and in mixtures of nitric acid and oxalic acid of varying concentrations. Green PuO₂ obtained by calcination of the oxalate has specifications within the recommended values for trace foreign substances such as chlorine, fluorine, carbon and nitrogen.     

Decomposition of oxalic acid with nitric acid

Oxalic acid or oxalate is widely used as a precipitant and a detergent in the field of nuclear energy. The present work aimed at developing a method of decomposing oxalic acid with HNO₃ in the presence of Mn²⁺ ion. The use of Mn²⁺ ion as low as 10^?3 mol/l facilitated the complete decomposition of oxalic acid, and the acidity of the resulting solution became as low as 0.1 eq/1 under the optimum conditions. The decomposition of oxalic acid is a first order reaction and proceeds at temperatures above 80°C; the activation energy of the reaction is 18.6 kcal/mol. This decomposition method is applicable to the dissolution of an oxalate precipitate.     

Old acid,new chemistry. Negative metal anions generated from alkali metal oxalates and others

A brief search in Sci Finder for oxalic acid and oxalates will reward the researcher with a staggering 129,280 hits. However, the generation of alkali metal and silver anions via collision-induced dissociation of the metal oxalate anion has not been previously been reported, though Tian and coworkers recently investigated the dissociation of lithium oxalate [18]. The exothermic decomposition of alkali metal oxalate anion to carbon dioxide in the collision cell of a triple quadrupole mass spectrometer leaves no place for the electron to reside, resulting in a double electron-transfer reaction to produce an alkali metal anion. This reaction is facilitated by the negative electron affinity of carbon dioxide and, as such, the authors believe that metal oxalates are potentially unique in this respect. The observed dissociation reactions for collision with argon gas (1.7−1.8 × 10⁻³ mbar) for oxalic acid and various alkali metal oxalates are discussed and summarized. Silver oxalate is also included to demonstrate the propensity of this system to generate transition-metal anions, as well.     

3-羟基-4-甲基-5-乙基-2(5H)-呋喃酮的合成

报道了以草酸二乙酯为原料,制备具有焦糖香味的香料化合物3-羟基-4-甲基-5-乙基-2(5H)-呋喃酮的方法:首先乙基溴化镁与草酸二乙酯通过格氏反应,以约50%产率生成2-氧代丁酸乙酯,然后其在碳酸钾的作用下发生缩合反应,以约94%产率得到3-羟基-4-甲基-5-乙基-5-乙氧羰基-2(5H)-呋喃酮,再通过水解、脱羧反应,得到3-羟基-4-甲基-5-乙基-2(5H)-呋喃酮.路线总收率约36%.     

Synthesis of oligoesters and polyesters from oxalic acid and ethylene glycol

High molecular weight poly(ethylene oxalate) with fiber-forming properties was obtained from oxalic acid and ethylene glycol. The process was carried out on two stages in the melt. A new method was used for aliphatic oligoester synthesis in the melt, because the decomposition of oxalic acid takes place in the presence of glycol. The process was carried out at low temperatures with azeotropic water removal. Investigations of the polycondensation of oxalic acid and ethylene glycol with a compound forming a heteroazeotrope with water showed that the process is subject to the general laws of the polycondensation in melt: it depends on the ratio of initial components, presence of accelerating compounds, etc. However, the reaction time of polycondensation was dependent on the stirring intensity. High molecular weight poly(ethylene oxalate) was obtained by oligomer polycondensation in the melt. Thorium carbonate and tin dichloride were used as catalysts.     

Volumetric estimation of potassium permanganate and potassium dichromate in mixtures with oxalic acid

1. A simple method has now been developed for the volumetric estimation of potassium permanganate and potassium dichromate in mixtures The method consists in taking an aliquot volume of the mixture in an Erlenmeyer flask, adding sufficient quantities of sulphuric acid and manganous sulphate (catalyst) and titrating with a standard solution of sodium oxalate or oxalic acid run in from the burette, until the colour changes from orange-red to yellow. The oxalic acid run ingives a measure of the permanganate present in the mixture Then the mixture in the flask is titrated with a standard solution of Mohr's salt using diphenylbenzidine as indicator. The volume of Fe⁺² solution run in the second stage gives a measure of the dichromate present in the original mixture. 2. The reverse titration does not give accurate results, because it is affected by the induced reaction between oxalic acid and dichromate which is induced by the reaction between oxalic acid and permanganate during the first stage of the reaction. This induced reaction has been studied in some detail.     

Quantitative Determination of Oxalic Acid Using Victoria Blue B Based on a Catalytic Kinetic Spectrophotometric Method

A sensitive catalytic method is developed for the spectrophotometric determination of oxalic acid. The procedure is based on the effect of oxalate on the oxidation of Victoria blue B by dichromate in dilute sulfuric acid medium. The reaction is quantitatively estimated by measuring the decrease in absorbance of Victoria blue B at the maximum wavelength of 610nm after quenching the reaction with tap water. The factors effecting the sensitivity and reproducibility of the reaction were studied. The method is not interfered with by foreign species generally associated with oxalate and oxalic acid. The described method is simple, specific, inexpensive and suitable for oxalic acid concentrations of between 0.06 and 9.0µgmL^–1. It was validated with satisfactory results by determining oxalic acid content in water extracts from plant materials such as spinach and Lathyrus sativus.     

Acyl Iodides in Organic Synthesis: V. Reactions with Carboxylic Acid Esters

Acyl iodides react with alkyl, alkenyl, and aralkyl esters derived from saturated, unsaturated, and aromatic mono- and dicarboxylic acids in the absence of a catalyst. The reaction involves cleavage of the OR bond and formation of organic iodide RI (including CH₂=CHI) and one or two symmetric carboxylic acid anhydrides. Phenyl acetate reacts with benzoyl iodide to give acetyl iodide and phenyl benzoate as a result of cleavage of the (O=)C–O bond. The reaction of diethyl fumarate with acetyl iodide is accompanied by cis– trans isomerization to afford maleic anhydride. In the reactions of acetyl iodide with diethyl oxalate and diethyl malonate, CO and CO₂ and CO₂ and polyketene are formed, respectively, in addition to ethyl iodide and acetic anhydride. Ethyl esters of strong organic acids, e.g., ethyl trihaloacetates, failed to react with acyl iodides under analogous conditions.     

Highly active Pd-Fe/α-Al_2O_3 catalyst with the bayberry tannin as chelating promoter for CO oxidative coupling to diethyl oxalate

A novel Pd-Fe/α-Al_2O_3 catalyst was synthesized by incipient-wetness impregnation method with bayberry tannin as chelating promoter and commercial hollow column Raschig ring a-Al_2O_3 as support for the synthesis of diethyl oxalate from CO and ethyl nitrite.A variety of characterization techniques including N_2 physical adsorption,optical microscopy,scanning electron microscopy and energy dispersive system(SEM-EDS),inductively coupled plasma optical emission spectroscopy(ICP-OES),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),transmission electron microscopy(TEM),were employed to explore the relationship between the physicochemical properties and activity of catalysts.It indicated that a large number of phenolic hydroxyl groups in bayberry tannin can efficiently anchor the active component Pd,reduce the particle size and make the active Pd as a multi-ring distribution on the commercial a-Al_2O_3 suppo rt,which we re beneficial to improve the catalytic activity for the production of diethyl oxalate from CO and ethyl nitrite.0.3 wts Pd-Fe/α-Al_2O_3 showed excelle nt catalytic activity and selectivity in a continuous flow,fixed-bed reactor with the loading amount of 10 mL catalysts,Under the mild reaction conditions,the space-time yield of diethyl oxalate was 978 g L ~1 h ~1 and CO conversion was 44% with the selectivity to diethyl oxalate of 95.5%.     

Cluster phase chemistry: collisions of vibrationally excited cationic dicarboxylic acid clusters with water molecules initiate dissociation of cluster components

A homologous series of cationic gas-phase clusters of dicarboxylic acids (oxalic acid, malonic acid, succinic acid, glutaric acid, and adipic acid) generated via electrospray ionization (ESI) are investigated using collision-induced dissociation (CID). Singly charged cationic clusters with the composition (Na(+))(2n+1)(dicarboxylate(2-))(n), where n = 1-5, are observed as major gas-phase species. Significant abundances of singly charged sodiated hydrogen dicarboxylate clusters with the composition (Na(+))(2n)(dicarboxylate(2-))(n)(H+), where n = 1-6, are observed with oxalic acid, malonic acid, and succinic acid. Isolation of the clusters followed by CID results mainly in sequential loss of disodium dicarboxylate moieties for the clusters of succinic acid, glutaric acid, and adipic acid. However, the dimer of sodiated hydrogen succinate, all malonate clusters, and all oxalate clusters, with the exception of the dimer, exhibit complex chemical reactions initiated by the collision of vibrationally excited clusters with water molecules. Generally, water molecules serve as proton donors for reacting dicarboxylate anions in the cluster, initiating dissociation pathways such as the decomposition of the malonate ion to yield an acetate ion and CO(2). The reactivity of several mixed dicarboxylate clusters is also reported. For example, malonate anion is shown to be more reactive than oxalate anion for decarboxylation when both are present in a cluster. The energetics of several representative cluster phase reactions are evaluated using computational modeling. The present results for cationic clusters are compared and contrasted to earlier studies of anionic sodiated dicarboxylic acid clusters.     

Determination of oxalate in black liquor by headspace gas chromatography

This study demonstrated a headspace gas chromatographic method (HS-GC) for the determination of oxalate content in black liquor (alkaline aqueous solution of inorganic chemicals and dissolved wood species from the alkaline pulping of wood). The method described in this paper is based on the reaction between oxalic and manganese dioxide in an acidic medium, in which oxalic acid is converted to carbon dioxide that is measured with a GC using a thermal conductivity detector. The challenge in developing this method was ensuring complete conversion of oxalic acid while minimizing the contribution of side reactions between carbohydrates, lignin and manganese dioxide to the carbon dioxide measured. It was found that a complete conversion of oxalate to carbon dioxide can be achieved within 3 min at a temperature of 70 degrees C; a MnO(2):C(oxalate) (concentration of H(2)C(2)O(4)+HC(2)O(4)(-)+C(2)O(4)(2-)) mole ratio of 60 and H(2)SO(4) concentration of 0.005-0.01 mol/L in the headspace vial. The method can detect concentrations as low as 0.39 microg of oxalate. The standard deviation was found to be 7% while recovery experiments with black liquor showed recoveries of 93-108% which were deemed acceptable for analysis of oxalate in an industrial sample such as black liquor.     

三草酸合铁(Ⅲ)酸钾合成方法的改进

三草酸合铁(III)酸钾具有工业生产价值,其合成作为化学专业本科生的经典实验项目,按教材实验的效果却不尽人意。本文在严谨的化学平衡理论分析基础上,首次提出提高合成产率的关键是严格控制草酸和草酸钾的用量,改进后的合成条件为：氧化步骤H2O2的浓度为6%,水浴温度为40°C;充分氧化后,微沸2分钟;酸溶步骤中草酸稍微过量,草酸钾过量10%;结晶时做到充分冷却。经此改进,可简化操作,节约原料,实验室平均产率达87%,教学中学生实验平均产率超过70%。     

Evaluation of Oxalate Decarboxylase and Oxalate Oxidase for Industrial Applications

Increased recirculation of process water has given rise to problems with formation of calcium oxalate incrusts (scaling) in the pulp and paper industry and in forest biorefineries. The potential in using oxalate decarboxylase from Aspergillus niger for oxalic acid removal in industrial bleaching plant filtrates containing oxalic acid was examined and compared with barley oxalate oxidase. Ten different filtrates from chemical pulping were selected for the evaluation. Oxalate decarboxylase degraded oxalic acid faster than oxalate oxidase in eight of the filtrates, while oxalate oxidase performed better in one filtrate. One of the filtrates inhibited both enzymes. The potential inhibitory effect of selected compounds on the enzymatic activity was tested. Oxalate decarboxylase was more sensitive than oxalate oxidase to hydrogen peroxide. Oxalate decarboxylase was not as sensitive to chlorate and chlorite as oxalate oxidase. Up to 4 mM chlorate ions, the highest concentration tested, had no inhibitory effect on oxalate decarboxylase. Analysis of the filtrates suggests that high concentrations of chlorate present in some of the filtrates were responsible for the higher sensitivity of oxalate oxidase in these filtrates. Oxalate decarboxylase was thus a better choice than oxalate oxidase for treatment of filtrates from chlorine dioxide bleaching.     

一氧化碳气相催化偶联合成草酸二乙酯的研究

在固定床反应器中对一氧化碳气相催化偶联合成草酸二乙酯的双金属钯系催化剂进行了活性评价。研究结果表明，所研制的催化剂具有较高的活性、选择性和稳定性，具有工业开发价值；在较高的反应温度和浓度下，亚硝酸乙酯易分解而使一氧化碳转化率和草酸二乙酯空时收率下降；在原料气中加入适量的乙醇有助于提高草酸二乙酯的空时收率。提出了一氧化碳气相催化偶联合成草酸二乙酯的适宜的工艺条件。     

草酸镁空心纳米结构的一步低热固相化学合成(英)

Nanostructuredmaterialsareafocusedresearchfieldduetotheirunusualpropertiesandpotentialap-plicationsrangingfrommesoscopicresearchtothede-velopmentofnanodevices[1,2].Especially,allsortsofnanoscalematerialswithspecificstructureorinter-estingmorphologyhavepro…     

Computational study on the kinetics and mechanisms for the unimolecular decomposition of formic and oxalic acids

The kinetics and mechanisms for the unimolecular decomposition reactions of formic acid and oxalic acid have been studied computationally by the high-level G2M(CC1) method and microcanonical RRKM theory. There are two reaction pathways in the decomposition of formic acid: The dehydration process starting from the Z conformer is found to be the dominant, whereas the decarboxylation reaction starting from the E conformer is less competitive. The predicted rate constants for the dehydration and decarboxylation reactions are in good agreement with the experimental data. The calculated CO/CO2 ratio, 13.6-13.9 between 1300 and 2000 K, is in close agreement with the ratio of 10 measured experimentally by Hsu et al. (In The 19th International Symposium on Combustion; The Combustion Institute: Pittsburgh, PA, 1983; p 89). For oxalic acid, its isomer with two intramolecular hydrogen bonds is the most stable structure, similar to earlier reports. Two primary decomposition channels of oxalic acid producing CO2+HOCOH with barriers of 33-36 kcal/mol and CO2+CO+H2O with a barrier of 39 kcal/mol were found. At high temperatures, the latter process becomes more competitive. The rate constant predicted for the formation of CO2 and HOCOH (the precursor of HCOOH) agrees well with available experimental data. The mechanism for the isomerization of HOCOH to HCOOH is also discussed.     

Catalytic kinetic spectrophotometry for the determination of trace amount of oxalic acid in biological samples with oxalic acid-rhodamine B-potassium dichromate system

A new catalytic kinetic spectrophotometric method was proposed for determining trace oxalic acid based on the catalytic effect of oxalate on the oxidation of potassium dichromate with rhodamin B in 0.10 M of sulfuric acid. Good linearity is obtained over the concentration range 0.40-6.0 microg/mL of oxalic acid. After the reactions of the catalytic and non-catalytic systems were terminated by using 2.00 mL of 4 M sodium hydroxide solution, they can be stable for 3 h at room temperature. The apparent activation energy of the catalytic reaction is 12.44 kJ/mol. The effect of 50 coexisting substances was observed. The method was used to determine trace oxalic acid in tea, spinach and urine samples with satisfactory results.