SrTi_（1－x）Sn_xO_3的水热合成与结构研究

采用水热晶化法合成出ＳｒＴｉ_（１－ｘ）Ｓｎ_ｘＯ_３系列化合物，并对其结构进行了表征。结果表明，随着Ｓｎ含量的增加，产物的晶胞体积增大，红外吸收谱带发生劈裂，并向高波数方向移动；ＳｒＴｉ_（１－ｘ）Ｓｎ_ｘＯ_３化合物粒度较小，其中常含有少量有机物和吸附水，可以Ｔｉ（ＯＣ４Ｈ９）４为Ｔｉ源直接合成。     

CeO2对SrTiO3陶瓷电导性的影响

ＣｅＯ＿２改性的ＳｒＴｉＯ＿３陶瓷采用传统的陶瓷工艺制备。ＳｒＴｉＯ＿３基质与ＣｅＯ＿２按化学式ＳｒＴｉＯ＿３＋ｘ（ＣｅＯ＿２ｎＴｉＯ＿２）配比［ｘ（ｗｔ％）分别为２、５、１０、１５、２０、２５和３０］。样品在１４００℃下烧结１ｈ。Ｃｅ在ＳｒＴｉＯ＿３陶瓷中起施主杂质作用。扫描电镜形貌分析和Ｘ射线物相观察表明，在此种陶瓷中有Ｃｅ＿２Ｏ＿３第二相即玻璃相存在，并对毒害ＳｒＴｉＯ＿３陶瓷半导体化的杂质有固溶性质；同时，Ｃｅ＿２Ｏ＿３第二相还具有减薄晶粒表面氧化层的作用，从而增加了晶粒电导特性。在室温下，ＣｅＯ＿２改性的半导体ＳｒＴｉＯ＿３陶瓷具有畸变的立方结构。     

改性SrTiO3陶瓷电容器材料的化学制备及电性研究

本文采用（Ｃ４Ｈ９Ｏ）４Ｔｉ，Ｓｒ（ＮＯ３）２和Ｎｉ（ＮＯ３）３为原料制成柠檬酸多元配合物溶液，经过形成溶胶凝胶过程，在一定条件下进行热分解，获得组成为：０．９１ＳｒＴｉＯ３＋０．０９（Ｂｉ２Ｏ３．３ＴｉＯ２）的陶瓷粉料，上述粉料掺入３ｍｏｌ％ＰｂＯ，３Ｍｏｌ％Ｌｉ２Ｏ和０．４ｍｏｌ％Ｒｂ２Ｏ后经混全，压片、干燥和烧结等步骤制成改性ＳｒＴｉＯ３电容器材料，电性研究表明，用这种材料制成的电容器其介电     

钙钛矿型复合氧化物Ca_xSr_（1－x）TiO_3催化剂上的甲烷氧化偶联反应

在固定床反应器上，评价了不同温度下钙钛矿型复合氧化物ＳｒＴｉＯ３和ＣａＴｉＯ３的组成变化对甲烷氧化偶联反应的影响．同时，利用ＸＰＳ和ＣＯ２－ＴＰＤ对催化剂的结构及其氧物种的反应特性进行了表征．结果表明：ＳｒＴｉＯ３和少量Ｃａ掺杂的ＣａｘＳｒｌ－ｘＴｉＯ３有利于在较低温度（９２３Ｋ）下催化反应的活性和选择性，而ＣａＴｉＯ３体系则在高温（１０７３Ｋ）下表现出较好的活性和选择性．钙钛矿型复合氧化物ＳｒＴｉＯ３和ＣａＴｉＯ３组成变化对不同温度下反应活性的影响与ＣＯ２－ＴＰＤ的脱附谱图有很好的平行关系．     

钙钛矿型LaCoO3的光催化活性

对钙钛矿型ＡＢＯ３复合氧化物的物理化学性质已有许多研究,但对其光催化活性很少报道．我们曾报道ＳｒＴｉＯ３［１］、ＰｂＴｉＯ３［２］等的制备及其对水溶性染料的光催化降解．本文报道ＬａＣｏＯ３的制备及其光催化活性．ＬａＣｏＯ３用柠檬酸络合法制取,所用试剂...     

纳米晶La_（1－_x）Sr_xFeO_3的合成及气敏特性的研究

用柠檬酸盐法合成出Ｌａ_（１－_ｘ）Ｓｒ_ｘＦｅＯ_３（ｘ＝０．１，０．２，０．３，０．４）原粉，再经固相反应得到纳米晶粉末，用ＴＧ、ＤＴＡ、ＸＲＤ、ＩＲ进行了表征，确证复合氧化物Ｌａ_（１－_ｘ）Ｓｒ_ｘＦｅＯ_３为钙钛矿型结构，粒径在１０～２５ｎｍ之间。实验结果表明，随着固相反应条件不同，产物粒径呈规律性变化．气敏特性研究表明，该纳米晶材料对乙醇有较高的选择性和灵敏度，其选择性顺序为Ｌａ_（０．９）Ｓｒ_（０．１）ＦｅＯ_３＞ＬａＦｅＯ_３＞ＬａＦｅＯ_３（大晶粒）。     

负载型贵金属催化剂的制备化学－载体等电点对Pd／A1_2O_3催化剂结构与催化性能的影响

本文通过化学修饰的方法改变了γ－Ａｌ_２Ｏ_３载体等电点（ＩＥＰＳ），并用具有不同等电点的Ａｌ_２Ｏ_３作载体，以（ＮＨ_４）_２ＰｄＣｌ４为活性组分前身制备了一系列Ｐｄ／Ａｌ_２Ｏ_３催化剂，在固定床微反色谱装置上考察了其对ＣＯ氧化的催化活性，用Ｈｉ—Ｏ_２滴定、紫外漫反射光谱（ＤＲＳ）、透射电子显微镜（ＴＥＭ）中的能量色散谱（ＥＤＸＳ）等方法对上述催化剂进行了表征，结果表明：Ａｌ_２Ｏ_３的等电点（ＩＥＰＳ）对所得催化剂中金属分散度和浓度分布都有明显影响，ＩＥＰＳ越高。活性组分越靠近外表面，在相同担载量下，其分散度也越高。这主要是由于载体ＩＥＰＳ的改变，导致了（ＮＨ_４）_２ＰｄＣｌ_４在γ－Ａｌ_２Ｏ_３上吸附机理的变化，并使所得催化剂对ＣＯ氧化的催化活性发生了规律性的变化。     

SrCeO3的微波合成及离子导电性质研究

ＳｒＣｅＯ_３的微波合成及离子导电性质研究徐秀廷，崔得良，冯守华，徐如人（吉林大学无机水热合成开放研究实验室，长春，１３００２３）关键词ＳｒＣｅＯ_３，微波合成，离子电导在复合氧化物中，ＳｒＣｅＯ３由于具有电子和离子混合导电性质而成为潜在的电极材料。另...     

含固氮酶钼微环境结构单元O_3MoS_3的Mo－S，Mo－Fe－S化合物的研究

研究了含固氮酶钼微环境Ｏ_３ＭｏＳ_３结构单元四个系列化合物［Ｍｏ（Ｓ，Ｏ－Ｃ_６Ｈ_４－１，２］~－（Ｍ）［Ｍｏ_２（ＣＯ）_３（Ｓ，Ｏ－Ｃ_６Ｈ_４－１，２）_３］~（２－）（Ｄ），［Ｍｏ_３（ＣＯ）_７（Ｓ，Ｏ－Ｃ_６Ｈ_４－１，２）_３］~（２－）（Ｔ），和［Ｍｏ_２Ｆｅ（ＣＯ）_４（Ｓ，Ｏ－Ｃ_６Ｈ_４－１，２）_３Ｃｌ_２］~（２－）（Ｔ_ｆ）的合成化学与结构化学，并通过Ｘ－射线光电子能谱，红外光谱和电化学环伏安研究，深入探讨了它们的混合价，电子迁移和电化学行为，也讨论了有趣的Ｏ_３ＭｏＳ_３结构单元。     

不同添加物和制备方式对Al2O3热稳定性的影响

通过水溶液成胶和丙三醇络事助成胶制备了不同的结构的γ－Ａｌ２Ｏ３,研究了Ｌａ,Ｓｉ,Ｂａ以及Ｌａ,Ｓｉ和Ｌａ,Ｂａ双组分改性对它们结构热稳定的作用,讨论了改性元素的引入方式及硅铝比的影响。结果表明,丙三醇络合助成胶能明显提高Ａｌ２Ｏ３的比表面积和孔径,并能显著改善Ａｌ２Ｏ３的热稳定性。     

Characterization of Catalysts for Glycerol Ester Production with Various Acetylating Agents

The use of raw materials from renewable sources by industries is essential to the sustainable development of modern society. The biodiesel produced by the transesterification of vegetable oils is a less polluting diesel fuel, but large amounts of glycerol (10% of total weight of product) are generated during the production process. The scientific community and industries of the sector know that, in the future, the amount of glycerol generated can cause a serious ecologic problem. Thus, it is essential to find alternatives for the consumption of this co-product, in its crude form and/or as high value-added derivatives. This work studied obtaining triacetate from the glycerol esterification reaction that was determined by electrospray ionization–mass spectrometry and gas chromatography–mass spectrometry. The reactions were carried out with sulfuric acid, phosphotungstic acid and in the absence of catalyst, using different acetylating agents (acetic acid and acetic anhydride). The phosphotungstic acid showed satisfactory performance in the catalytic esterification of glycerol when acetic acid and acid anhydride were used. The use of acetic anhydride as the acetylating agent favors the esterification reaction, decreasing the reaction time required for obtaining glycerol triacetate.     

A review on catalytic role of heterogeneous acidic catalysts during glycerol acetylation to yield acetins

Glycerol is a colorless, odorless, and non-toxic compound and has application in food, paint, and pharmaceutical industries. At an industrial scale, glycerol (GL) commonly forms as a by-product of soap and biodiesel producing industries. To utilize the excess GL of biodiesel industry, former has been employed as a building block to manufacture value added products such as acetins by fine chemical manufacturers. Acetins, including monoacertin (MA), diacetin (DA) and triacetin (TA), has diverse application such as in cosmetics, fuel additives, pharmaceuticals, leather, and food processing. Specifically, TA is employed as an additive to improve the anti-knocking property of gasoline and viscosity and cold flow properties of biofuel. The acetins are frequently produced at an industrial scale via a homogeneous Brønsted acid catalysed process employing acetic acid or acetic anhydride as an acetylating agent. Homogeneous acid catalysts are corrosive, non-reusable, difficult to separate from the reaction mixture, and sensitive to water, which is formed as a by-product during the glycerol acetylation. To address the issues, Brønsted or Lewis acidic group have been immobilized over various matrices (e.g., mixed metal oxides, mesoporous silica, ion exchange resins, carbon, zeolites, and magnetic nanoparticles) to prepare the heterogeneous acidic catalysts for the glycerol acetylation. Both the sites assisted the carbocation mediated esterification of glycerol with acetic acid or acetic anhydride. The ease of catalyst separation from the reaction mixture and reusability are the major advantages of their usage. However, lower conversion levels with low product selectivity, catalysts deactivation, and partial dissolution in the reaction mixture are the concerns related to the catalysts. To address these issues, novel catalyst preparation techniques to incorporate the variety of active sites over the matrix surface have been employed in the literature, which will be highlighted in detail in the present review article.     

Role of Epoxides in the Oxidation of Allyl Alcohol,Allyl Formate,and Allyl Acetate in Acetic Acid

The formation of epoxy derivatives as intermediate products in the oxidation of allyl alcohol, allylformate, allyl acetate in acetic acid was proved. Intermediate epoxy compounds undergo further trans-formations: They react with acetic acid to give glycerol esters or are converted into polyethers of glyceroland its esters. The rate constants for transformations of 2,3-epoxypropanol, 2,3-epoxypropyl formate, and 2,3-epoxypropyl acetate along these pathways were measured. Higher selectivity of glycerol ester formation from allyl formate was substantiated.     

Glycerol acetylation considering competing dimerization

Glycerol acetylation is a very interesting reaction for studies of consecutive kinetics. In this short communication, we present a pseudo-homogeneous model for the synthesis of triacetyl glycerol from the reaction of glycerol and acetic acid over strongly acidic Amberlyst-15 and Amberlyst-70 catalysts, considering a dimerization of diacetyl glycerol (DAG) into diglycerol tetraacetate as a parallel reaction and compare the results with a model without side reactions. The best fits were obtained for apparent zeroth-order dimerization and first-order consecutive reactions in the presence of acetic acid in excess and with removal of water. An adaptation was made for DAG. The proposed model shows that the formation of DAG is faster than the consumption of glycerol, which could be an explanation for the occurrence of DAG dimerization instead of other parallel reactions in acetylation.     

Examples of the application of titration techniques in the process industry

Different titration techniques are used for analyses of the nitrating acids in three different industrial processes, namely in the production of glycerol trinitrate (nitrate ester,  C-ONO₂), trinitrotoluene (nitro group,  C-NO₂) and trimethylene trinitramine (nitramine, N-NO₂). The determination of the composition of the process acids, which consist mainly of water, nitric acid, sulphuric acid, acetic acid and hexamethylenetetramine with minor amounts of nitrous acid and ammonium nitrate, are complicated by the ability of the process acids to dissolve the product to various extents. Acid-base titrations as well as oxidation-reduction titrations and voltammetry are used to provide a rapid system for analysing the process acids.     

Selective esterification of glycerol with acetic acid to diacetin using antimony pentoxide as reusable catalyst

Glycerol can be obtained as a by-product during biodiesel manufacture. It is important to convert glycerol to value-added products. Glycerol esterification with acetic acid is one of the most promising approaches for glycerol utilization. It is usually difficult to obtain diacetin with good activity and selectivity. In this work, glycerol esterification with acetic acid over different metal oxides, such as Bi2O3, Sb2O3, Sn O2, Ti O2, Nb2O5 and Sb2O5, was investigated. It was found that in the six investigated metal oxides, only Sb2O5 resulted in good activity and selectivity to diacetin. Under the optimized conditions, the glycerol conversion reached 96.8%,and the selectivity to diacetin reached 54.2%, while the selectivity to monoacetin and triacetin was 33.2% and12.6%, respectively. The catalysts were characterized with FT-IR spectra of adsorbed pyridine, which indicated that in the six investigated metal oxides, only Sb2O5 possessed Br?nsted acid sites strong enough to protonate adsorbed pyridine. The good catalytic activity and selectivity to diacetin might be mainly attributable to the Br?nsted acid sites of Sb2O5. Reusability tests showed that with Sb2O5 as catalyst, after six reaction cycles, no significant change in the glycerol conversion and the selectivity to diacetin was observed.     

Determination of dihydroxyacetone and glycerol in fermentation process by GC after n-methylimidazole catalyzed acetylation

A gas chromatographic method that accurately measures glycerol and dihydroxyacetone from a fermentation broth is described in this paper. The method incorporates a sample derivatization reaction using n-methylimidazole as catalyst in the presence of acetic anhydride. Resulting derivatives are separated on a DB-5 capillary column and flame ionization detector. Results show that 10 μL n-methylimidazole and 75 μL acetic anhydride are sufficient to complete the acetylation for glycerol and dihydroxyacetone at room temperature for 5 min. The present method exhibits good linearity at a concentration range of 1-100 g/L with excellent regression (R(2) > 0.9997). The limits of detection are 0.025 and 0.013 g/L for dihydroxyacetone and glycerol, respectively. The method has been successfully applied to the monitoring and control of the fermentation process, and recoveries are in the range of 95.5-98.8% with relative standard deviations below 1%.     

The combined effects of acetic acid, formic acid, and hydroquinone on Debaryomyces hansenii physiology

The combined effects of inhibitors present in lignocellulosic hydrolysates was studied using a multivariate statistical approach. Acetic acid (0–6 g/L), formic acid (0–4.6 g/L) and hydroquinone (0–3 g/L) were tested as model inhibitors in synthetic media containing a mixture of glucose, xylose, and arabinose simulating concentrated hemicellulosic hydrolysates. Inhibitors were consumed sequentially (acetic acid, formic acid, and hydroquinone), alongside to the monosaccharides (glucose, xylose, and arabinose). Xylitol was always the main metabolic product. Additionally, glycerol, ethanol, and arabitol were also obtained. The inhibitory action of acetic acid on growth, on glucose consumption and on all product formation rates was found to be significant (p≤0.05), as well as formic acid inhibition on xylose consumption and biomass production. Hydroquinone negatively affected biomass productivity and yield, but it significantly increased xylose consumption and xylitol productivity. Hydroquinone interactions, either with acetic or formic acid or with both, are also statistically signficant. Hydroquinone seems to partially lessen the acetic acid and amplify formic acid effects. The results clearly indicate that the interaction effects play an important role on the xylitol bioprocess.     

Biotechnological Utilization of Biodiesel-Derived Glycerol for the Production of Ribonucleotides and Microbial Biomass

Ten yeast strains were evaluated concerning their capabilities to assimilate biodiesel-derived glycerol in batch cultivation. The influence of glycerol concentration, temperature, pH and yeast extract concentration on biomass production was studied for the yeast selected. Further, the effect of agitation on glycerol utilization by the yeast Hansenula anomala was also studied. The yeast H. anomala CCT 2648 showed the highest biomass yield (0.30?g?g^?1) and productivity (0.19?g?L^?1?h^?1). Citric acid, succinic acid, acetic acid and ethanol were found as the main metabolites produced. The increase of yeast extract concentration from 1 to 3?g?L^?1 resulted in high biomass production. The highest biomass concentration (21?g?L^?1), yield (0.45?g?g^?1) and productivity (0.31?g?L^?1?h^?1), as well as ribonucleotide production (13.13?mg?g^?1), were observed at 700?rpm and 0.5?vvm. These results demonstrated that glycerol from biodiesel production process showed to be a feasible substrate for producing biomass and ribonucleotides by yeast species.     

Polymerization of acrylonitrile initiated by a manganese(III) acetate glycerol redox system

The kinetics of polymerization of acrylonitrile(AN) initiated by manganese(III) acetate in the presence of glycerol was investigated in the temperature range of 30–40°C. The effect of varying the concentrations of glycerol, sulfuric acid, acetic acid, metal ion, and monomer on the rate was studied. A suitable reaction scheme and rate expression have been proposed. Termination was mutual and was caused by the combination of two growing polymer radicals.