Ti2(OMe)4/SiO2催化剂的制备及其合成碳酸二甲酯的反应性能

采用表面改性和离子交换法制备了SiO2负载的Ti2(OMe)4双核桥联配合物催化剂，用IR、TPD和微反技术考察了催化剂的表面构造及CO2和CH3OH在催化剂表面上的化学吸附和反应性能。结果表明：双核桥联配合物Ti2(OMe)4以Ti-O-Si键锚定在SiO2表面上；CO2在催化剂表面存在桥式和甲氧碳酸酯基两种吸附态，其中甲氧碳酸酯基吸附态是生成DMC的关键物种；CH3OH在催化剂上只有一种分子吸附态。在150℃以下，CO2和CH3OH在Ti2(OMe)4/SiO2催化剂表面上高选择地生成碳酸二甲酯。     

Small angle neutron scattering studies on nonaqueous dispersions of calcium carbonate Part 2. Determination of the form factor for concentric spheres

Colloidal dispersions of calcium carbonate, stabilised primarily by a surface active agent, in both toluene and dodecane have been examined by small angle neutron scattering. A model has been developed to simulate the scattering behaviour of the particles and is based on the idea of a concentric sphere with a homogeneous layer of adsorbed material surrounding a core particle. Computations based on the model show a wide variation of scattering behaviour with variation of the coherent scattering length of the dispersion medium. These predictions were confirmed by experiment. A method is described for analysis of the experimental data which leads to a determination of the thickness of the adsorbed layer, the radius of the core particle and the standard deviation of core particle radius.     

Kinetic and computational studies on aminolysis of bicyclic carbonates bearing alicyclic structure giving alicyclic hydroxyurethanes

Aminolysis of bicyclic carbonates, which consist of five-membered cyclic carbonate and five- or six-membered alicyclic groups, was examined. Kinetic studies revealed that the aminolysis of the bicyclic carbonate with cyclohexane ring proceeded more smoothly than that of the bicyclic carbonate with cyclopentane ring. Computational calculation suggested that the different reaction rates originate from the distinct ring-strain of the cyclic carbonate groups affected by the conformation of the alicyclic groups.     

非均相羰基氧化合成碳酸二苯酯反应液组分的分析

通过色质联用仪对非均相催化一步合成碳酸二苯酯(DPC)过程中的反应液的主要产物及副产物进行了定性分析，其结果发现该反应的主要副产物为苯氧基丙酸和4-苯氧基苯酚以及四丁基铵盐；用气相色谱外标法对反应液中的DPC进行了定量分析，并通过回归法得到了定量分析：DPC的计算方程式，实验证明该方程在DPC的浓度小于10％范围内比较可靠。     

常压气相氧化羰基化合成碳酸二乙酯

碳酸二乙酯是一种重要的有机化工原料,可广泛用于合成农药如脱叶灵,医药如喹啉酮衍生物,中间体3-氧硫代羧酸酯,还可用于电子管阴极的镀层[1-3]。生产碳酸二乙酯的传统方法为:无水乙醇与光气反应生成氯甲酸乙酯,氯甲酸乙酯继续与乙醇反应生成碳酸二乙酯后经水洗蒸馏制成。使用光气为原料对设备的要求较高。我们在常压下气相羰基化合成碳酸二乙酯[4]:2ＮＯ+Ｃ2Ｈ5ＯＨ+0.5Ｏ2→2Ｃ2Ｈ5ＯＮＯ+Ｈ2Ｏ(1)ＣＯ+2Ｃ2Ｈ5ＯＮＯ→(Ｃ2Ｈ5Ｏ)2ＣＯ+2ＮＯ(2)产生的一氧化氮可与氧气和乙醇进行反应再生为亚硝酸乙酯,符合原子经济反应且几乎不放出对…     

Influence of molecular characteristics on overall isothermal melt-crystallization behavior and equilibrium melting temperature of syndiotactic polypropylene

Overall isothermal melt-crystallization and subsequent melting behavior of metallocene-catalyzed syndiotactic polypropylene resins of various molecular weights were investigated using differential scanning calorimetry (DSC) technique. Two sets of molecular weight range were synthesized with two different metallocene catalyst systems. The kinetics of the overall isothermal melt-crystallization process was analyzed based on various macrokinetic models, i.e. the Avrami, Malkin and Urbanovici-Segal models. The effective activation energy describing the overall isothermal crystallization process over the crystallization temperature range studied was estimated based on an Arrhenius approximation of the obtained Avrami crystallization rate constants. The equilibrium melting temperature for each of these resins was estimated based on the linear and non-linear Hoffman-Weeks extrapolative methods.     

Photodegradation of polypropylene thermal bonded non-woven fabric

Samples of thermal bonded polypropylene non-woven fabrics were exposed to light from two TUV 30W G30T8 Philips lamps (λ = 253.7 nm) in a covered open-air chamber at room temperature (25 °C and 55% relative humidity) for different periods of time. In order to determine the state of degradation, the samples were examined by optical microscopy, scanning electron microscopy, staining with an isopropanol solution of methylene blue and Sudan III, colourimetry, Fourier transform infrared (FTIR) spectroscopy and density measurements. Although the bonded areas formed under complex thermal and mechanical deformations during the fabric production, no localized staining was observed. The colour of the irradiated and stained fabrics changed uniformly due to the even production of polar groups in the process of irradiation. It was found that the change of redness and blueness of degraded and stained samples can be correlated linearly with the evolution of POOH groups as determined by FTIR spectroscopy. Products containing carbonyl (CO), hydroxyl and/or hydroperoxide (POOH) groups increase with time of degradation with a non-linear relation. It was also observed that the density and 997 cm⁻¹/972 cm⁻¹ FTIR absorbance ratio increases with degradation time. Density fluctuation and the build up of degradation products caused fibre cracks and embrittlement.     

不同碳酸铵试剂对共沉淀法制备的GDC粉性状的影响

近年来工作温度在500￣700℃的中温固体氧化物燃料电池(IT-SOFC)受到广泛关注。稀土掺杂氧化铈尤其是钐、钆掺杂氧化铈在中温下的离子电导率远高于钇掺杂氧化锆(YSZ),是较为理想的IT-SOFC电解质材料。由于掺杂氧化铈难于烧结,不便于制备致密的电解质膜,通过提高掺杂氧化铈粉体细度来降低其烧结温度,是近年来该材料应用领域的一个研究热点。已有各种合成掺杂氧化铈纳米粉的报道,如采用共沉淀法、固态反应法、水热处理法、燃烧法、溶胶-凝胶法等等。其中碳酸盐共沉淀法由于具有成本低、设备简单以及合成粉体细度高等优点而倍受青睐。通…     

高稳定性CaO-ZrO2固体碱催化剂的表征和催化性能

用共沉淀法经高温焙烧制备了CaO摩尔分数从10%至50%的CaO-ZrO₂系列催化剂, 将其应用于碳酸丙烯酯和甲醇酯交换合成碳酸二甲酯过程, 并通过XRD, FT-IR, BET, ICP, CO₂-TPD, XPS等表征手段研究了催化剂的物性及其催化性能随组成变化的的规律. 结果表明, 当CaO摩尔分数高于30%时, 表面出现游离的CaO, 虽然具有强碱性和高活性, 但是稳定性差; 而当CaO摩尔分数低于30%时, Ca^2＋进入ZrO₂晶格, CaO与ZrO₂形成连续固溶体, 并且随着CaO含量的增加, 晶格氧的电荷密度增加, 催化剂的碱性增强, 使得CaO-ZrO₂催化剂在碳酸丙烯酯和甲醇酯交换合成碳酸二甲酯过程中获得了高活性和高稳定性.     

Thermal properties of polypropylene post-consumer waste (PP PCW)

Differential scanning calorimetry has been used to study the heat flow during melting and crystallisation of a range of polypropylene post-consumer waste (PP PCW) grades and blends. The heat flow curves and the heat capacity curves indicated that the PP PCW grades and blends contained contaminants even after manual sorting and a cleaning process. The enthalpies of the PP PCW grades were lower than that for the virgin grades, as a result of degradation. Small amounts of polymeric contaminants (up to 10%) did not affect the enthalpies of PP PCW although other contaminants may have had some effect. The enthalpies of the PCW blends could in general be predicted by a linear additive rule, which is of importance for recycling a variety of PP PCW products.The authors would like to thank Dr. M. Killen (Basell Australia Pty. Ltd.), Mr. P. Slaven (Citiwide MRF), Dasma Valley Waste Prop. Ltd. and Mr. I. Janetzki (Huhtamaki Australia Ltd.) for supplying materials for this project. Financial support for the project was provided by Basell Australia and Ecorecycle Victoria, Australia.