合成碳酸二甲酯的催化剂研究进展

碳酸二甲酯以其优良的性质在化学反应和石油产品中得到了广泛应用.作者介绍了合成碳酸二甲酯的4种方法,包括甲醇氧化羰基化法、酯交换法、尿素醇解法和二氧化碳-甲醇合成方法.重点介绍了每种方法使用的催化剂对碳酸二甲酯的选择性及对副产品的影响.综述了负载型分子筛催化剂在催化合成碳酸二甲酯研究进展.研究负载型分子筛催化剂催化合成碳...     

Reaction mechanism of the direct carboxylation of methanol to dimethylcarbonate: experimental and theoretical studies

The formation of dimethylcarbonate (DMC) from MeOH and CO₂ under [Nb(OMe)₅]₂ catalysis follows a different route (“acid-plus-base activation” of methanol) with respect to other known catalytic systems such as Sn(IV) and dicyclohexylcarbodiimide (DCC) that promote a “double-base activation”. The reaction intermediates and related transition states obtained from density functional (DFT) calculations are presented. Experimental data also feature a different reaction mechanism.     

Quadri‐Synergetic Effect for Highly Effective Carbon Dioxide Fixation and Its Application to Indoloquinolinone

The first copper‐catalyzed cyclic anti‐nucleometallation–carboxylation of 2‐alkynylanilines with carbon dioxide in the presence of dimethylzinc (ZnMe₂) and cesium fluoride (CsF) for the effective synthesis of indolyl‐3‐carboxylic acids and indolodihydropyran‐2‐one is described. Through a mechanistic study, it is unveiled that the metal ions Cu²⁺, Zn²⁺, Cs⁺ and F⁻ are working together for this CO₂‐based highly efficient carboxylation.     

聚酰胺胺树形分子对羧基化聚乙烯的表面修饰

通过紫外光接枝方法,以丙烯酸为单体对低密度聚乙烯薄膜进行表面改性,然后用聚酰胺胺(PAMAM)分子对羧基化的聚乙烯表面进行修饰,制备了表面固定PAMAM树形分子的低密度聚乙烯薄膜。通过接触角测量,衰减全反射红外光谱,扫描电镜等方法的表征,证明丙烯酸成功接枝到聚乙烯薄膜表面,聚酰胺胺树形分子通过与羧基的结合形成团簇结构,反映了接枝链在薄膜表面的聚集状态。     

单分散纳米二氧化硅微球的制备及羧基化改性

采用改进工艺条件的Stober法制备纳米SiO_2微球.用场发射扫描电镜(FESEM)分析了纳米二氧化硅的形貌、粒径.结果表明,通过温度梯度法和控制氨水浓度变化制备出高圆度、单分散、粒径可控的纳米级二氧化硅微球.用KH-550硅烷偶联剂和丁二酸酐对纳米二氧化硅表面羧基化改性.采用X射线能谱仪(EDS)、热重(TGA)、傅里叶红外(FTIR)等手段对改性后纳米二氧化硅的结构、元素种类及含量进行了表征.结果表明,纳米二氧化硅表面成功接枝了羧基官能团.     

大比表面积羧基化聚苯乙烯微球的制备及表征

为了获得羧基化的聚合物微球,利用改进的二步溶胀法,以无皂乳液聚合制备的聚苯乙烯种子微球溶胀羧基功能单体和交联剂,制备羧基化改性聚苯乙烯微球,研究羧基单体种类、种子球添加量对微球的影响,确定了最佳的聚合反应条件,并采用XPS和扫描电子显微镜表征了聚合物结构和微球的形貌.结果表明:以苯乙烯-二乙烯苯-甲基丙烯酸为原料聚合得...     

常压羧化法制备2,6-二羟基苯甲酸

研究了间苯二酚常压羧化法制备2,6-二羟基苯甲酸。分析了Kolbe-Schmitt羧化反应机理,选择了该反应的适宜溶剂。通过正交试验确定了反应的最佳参数。在优化的反应参数(间苯二酚/碳酸钾摩尔比1∶0.5,反应温度155～160℃,反应时间6～7h,溶剂为二甲基乙酰胺)下,2,6-二羟基苯甲酸收率达29.38%。     

Performance of combined use of chlorosilanes and AlCl3 in the carboxylation of toluene with CO2

Carboxylation of toluene with CO₂ for the production of p‐toluic acid was shown to be promoted by the addition of Me₂PhSiCl, Ph₂SiCl₂, Ph₃SiH, or Ph₃SiCl into the AlCl₃ activated system, and the reaction activity was in the increasing order of Ph₂SiCl₂ < Me₂PhSiCl < Ph₃SiH < Ph₃SiCl. The spectrum of IR indicated that CO₂ could be effectively activated by AlCl₃ or Ph₃SiCl independently. DFT calculation was carried out to estimate the electrophilic potentials of the chlorine bridged AlCl₃···chlorosilane complex in the form of the APT atomic charges of Si and Al. The much higher activity of Ph₃Si‐Cl···AlCl₃ over AlCl₃‐AlCl₃ was considered due to its higher valences of Si and Al which are +2.107 and +1.833 compared with the +1.814 of Al in the latter. The mechanism of CO₂ activation under the action of double Lewis acid sites of Si and Al and the subsequent carboxylation of toluene was consequently proposed. © 2016 American Institute of Chemical Engineers AIChE J, 63: 185–191, 2017     

亚胺基二乙酸螯合纤维的合成与性能研究

以氯甲基化聚丙烯接枝苯乙烯纤维(chloramethylated polypropylene grafted styrene,CPP-g-St)为原料,采用胺基化和羧甲基化两步法反应,制备一种具有选择吸附性的亚胺基二乙酸螯合纤维(iminodiacetic acid chelate fiber,IDACF),并利用正交实验法研究了时间、浴比、温度、氯乙酸的用量对羧甲基化反应的影响。所制备的亚胺基二乙酸螯合纤维对Cu2+的螯合吸附容量为65.54mg·g-1,纤维对Cu2+的吸附容量是对Fe3+的10.52倍。采用元素分析(EA)、傅里叶红外光谱(FT-IR)、扫描电镜(SEM)、热重(TG)测试手段对纤维的结构和性能进行了表征。结果表明,经过两步反应后,亚氨基二乙酸基成功接枝到原料纤维表面,制备出的纤维具有良好的热稳定性。     

The response of Arundo donax L. (C3) and Panicum virgatum (C4) to different stresses

In this work, two perennial rhizomatous grasses (Arundo donax L. (giant reed; C₃) and Panicum virgatum L. (switchgrass; C₄)) considered as promising energy crops have been subjected to four different types of stress in two experiments: (i) both species were subjected to four salinity and water stress treatments [well-watered with non-saline solution (WW S−), low-watered with non-saline solution (WS S-), well-watered with saline solution (WW S+) and low-watered with saline solution (WS S+)]; and (ii) both species were subjected to three temperature and light treatments [ambient temperature and light (C), ambient temperature and darkness (AD) and cold temperature and darkness (CD)]. Photosynthetic and physiological parameters as well as biomass production were measured in these plants. It can be hypothesized that a higher photosynthesis rate (A_sat) was be observed in switchgrass as a consequence of its C₄ metabolic pathway. However, our results indicated a similar A_sat at the beginning of the experiment for both species. This could be due to switchgrass being an NAD-ME C₄ type whereas giant reed has been reported as a C₃ species with a high photosynthetic rate. We showed that switchgrass seems to be more resistant to stresses such as water stress, salinity and cold than giant reed in our greenhouse conditions.