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991.
Some novel cycloaddition reactions based on benzyne and olefins have been developed.These reactions were performed in the absence of a transition metal catalyst,and they displayed good yields.These cycloaddition reactions of benzyne with olefins provide effective routes for synthesizing benzocyclobutenes,biaryl compounds and 9,10-dihydrophenanthrene derivatives. 相似文献
992.
993.
以碳黑为第二模板剂在氟离子体系中一步水热合成了多级结构MCM-22分子筛组装体(简称为MCM-22-FC)。考察了碳黑和氟离子对MCM-22分子筛形貌和催化性能的影响。MCM-22-FC分子筛是由大量片状晶体交错生长形成的组装体结构,其中MCM-22的片层结构更薄,在其固有的微孔中存在的晶间孔呈现大孔和介孔的特征。MCM-22-FC负载Mo后得到的Mo/MCM-22-FC催化剂在甲烷无氧芳构化反应(MDA)中提高了苯收率和芳烃选择性,并且提高了催化剂的寿命。通过氨气程序升温脱附(NH3-TPD)表征,吡啶红外(Py-IR)表征,结合热重(TG)分析,得出的结论是Mo/MCM-22-FC在MDA中优越的催化性能是由于氟离子进入到分子筛骨架当中,形成具有拉电子效应的结构单元,从而提高了分子筛的Brönsted酸量,较多的Brönsted酸性位将更多的Mo物种迁移至分子筛孔道内部,形成更多的MoCx或MoOxCy活性物种以及更有利于大分子产物扩散的MCM-22薄片层的结构。少量过剩的Brönsted酸性位在成型后保留在Mo/HMCM-22-FC催化剂活性中心抑制了积碳的形成,也有助于改善芳烃的选择性。 相似文献
994.
哈茨木霉CGMCC 2979生物转化栀子中的京尼平苷制备京尼平 总被引:1,自引:0,他引:1
采用微生物直接转化药材的方法,将栀子中的京尼平苷转化为京尼平,无需糖苷酶和京尼平苷的制备. 在培养温度为30 ℃,pH 6.1以及栀子载量为80 g/L的条件下,48 h京尼平苷的转化率为97.8%. 转化后的京尼平通过XAD-16N大孔树脂偶联硅胶层析的方法,制备得到纯度大于95%的京尼平,收率为62.3%. 在催化、转化机制研究中,从哈茨木霉CGMCC2979的发酵液中分离得到了分子量为74.4 kDa的京尼平苷β-葡萄糖苷酶,该酶最优催化条件为50 ℃和pH 4.0-5.0. Km和Vmax分别为3.6 mmol/L和775 μmol/h/mg蛋白. 本文提供了一种简便、高效制备京尼平的新方法. 相似文献
995.
提出了一个木质纤维素生物质预处理的全绿色加工过程.以玉米秸秆和玉米芯为原料,以超临界CO2和超声偶合法对木质纤维素进行预处理.超临界CO2预处理条件为:压力15-25 MPa,温度120170℃,含水量50%,反应时间0.54 h.超声场功率600W,温度80℃,作用时间2-8 h.用纤维素酶水解反应获得的还原糖总量来评价预处理效果.结果表明,单纯超临界CO2和超临界CO2偶合超声预处理都能够提高生物质水解反应还原糖产量.对于玉米芯,超临界CO2预处理(170℃,20 MPa,3 0min)后,还原糖产率为62%(未预处理的为12%).对于玉米秸秆(170℃,20 MPa,2.5 h),还原糖产率为46.4%.对于玉米芯,超临界CO2偶合超声预处理(600 W,80℃下超声处理6 h,然后用170℃,20 MPa超临界CO2预处理30 min)后,还原糖产率为87%.对于玉米秸秆,超临界CO2偶合超声预处理(600 W,80℃下超声处理8 h,然后用170℃,20 MPa超临界CO2预处理1 h)后,还原糖产率为25.5%.与未处理生物质相比,X射线衍射结果表明玉米秸秆和玉米芯在超临界CO2和超声预处理后其结晶度没有明显变化.扫描电镜分析则发现木质纤维素的表面积显著增加. 相似文献
996.
Nanostructured ZnSe-graphene/TiO2 was synthesized by a hydrothermal-assisted approach. ZnSe-graphene/TiO2 exhibited favorable adsorption of rhodamine B, a wide wavelength absorption range, and efficient charge separation. Reactive oxygen species were generated by the oxidation of 1,5-diphenyl carbazide to 1,5-diphenyl carbazone. The sonocatalytic reaction mechanism was pro-posed. These findings potentially broaden the applications of sonocatalytic technologies. 相似文献
997.
Yong-Qian Fu Long-Fei Yin Hua-Yue Zhu Ru Jiang Shuang Li Qing Xu 《Applied biochemistry and biotechnology》2014,174(6):2019-2030
The effects of pellet morphology, diameter, density, and interior structure on L-lactic acid fermentation by Rhizopus oryzae were characterized for different inoculum sizes and concentrations of peptone and CaCO3. Inoculum size was the most important factor determining pellet formation and diameter. The diameter decreased with increasing inoculum size, and larger pellets were observed for lower inoculum sizes. Peptone concentration had the greatest effect on pellet density, which increased with increasing peptone concentration. L-lactic acid production depended heavily on pellet density but not on pellet diameter. Low-density pellets formed easily under conditions of low peptone concentration and often had a relatively hollow structure, with a thin condensed layer surrounding the pellet and an extraordinarily loose biomass or hollow center. As expected, this structure greatly decreased production. The production of L-lactic acid increased until the density reached a certain level (50–60 kg/m3), in which the compact part was distributed homogeneously in the thick outer layer of the pellet and loose in the central layer. Homogeneously structured, denser pellets had limited mass transfer, causing a lower overall turnover rate. However, the interior structure remained nearly constant throughout all fermentation phases for pellets with the same density. CaCO3 concentration only had a slight influence on pellet diameter and density, probably because it increases spore germination and filamentous hypha extension. This work also provides a new analysis method to quantify the interior structure of pellets, thus giving insight into pellet structure and its relationship with productivity. 相似文献
998.
Zongchao Jia Ying Liu Maurycy Daroch Shu Geng Jay J. Cheng 《Applied biochemistry and biotechnology》2014,173(7):1667-1679
This article presents a study on screening of microalgal strains from the Peking University Algae Collection and heterotrophic cultivation for biodiesel production of a selected microalgal strain. Among 89 strains, only five were capable of growing under heterotrophic conditions in liquid cultures and Chlorella sp. PKUAC 102 was found the best for the production of heterotrophic algal biodiesel. Composition of the growth medium was optimised using response surface methodology and optimised growth conditions were successfully used for cultivation of the strain in a fermentor. Conversion of algal lipids to fatty acid methyl esters (FAMEs) showed that the lipid profile of the heterotrophically cultivated Chlorella sp. PKUAC 102 contains fatty acids suitable for biodiesel production. 相似文献
999.
Rui Yang Kristof Van Hecke Bao Yi Yu Guang Yue Li Guang Hua Cui 《Transition Metal Chemistry》2014,39(5):535-541
Two coordination polymers, [Co(L1)(IPA] n (1) and {[Ag(L2)(HMIPA)]·H2O} n (2) (H2IPA = isophthalic acid, L1 = 1,2-bis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene, H2MIPA = 5-methylisophthalic acid, L2 = 1,6-bis(5,6-dimethylbenzimidazol-1-yl)hexane, have been synthesized and characterized by physicochemical and spectroscopic methods, as well as single-crystal X-ray diffraction. In 1, six-coordinated cobalt centers are bridged by L1 and IPA2? ligands to generate a (4,4) two-dimensional layer. However, complex 2 features a 1D chain structure, which is further extended by O–H···O hydrogen bonding interactions into a 2D supramolecular layer with (63) topology. The fluorescence and thermal gravimetric analysis of both complexes were also explored. Furthermore, the complexes 1 and 2 exhibit remarkable catalytic properties for the degradation of methyl orange dyes in a Fenton-like process. 相似文献
1000.
Guangying Wang Gang Liu Yufeng Du Wenshu Li Shuhui Yin Shuzhan Wang Yanhui Shi Changsheng Cao 《Transition Metal Chemistry》2014,39(6):691-698
The complexes [PdX2Py]2(di-NHC) (X = Br or Cl) in which di-NHC represents a di-N-heterocyclic carbene, featuring a rigid phenylene spacer between the carbene units, have been prepared from reactions of the corresponding diimidazolium halide salts with PdCl2 in pyridine. The molecular structures of three of the complexes were determined by X-ray diffraction studies. The influences of different substitutions and of the halide ligand (Br or Cl) on the structure and reactivity of the complexes have been studied. The catalytic activity of the binuclear palladium complexes was tested in the Mizoroki–Heck reaction of styrene with bromobenzene. 相似文献