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排序方式: 共有750条查询结果,搜索用时 15 毫秒
741.
Soofia Mehdizadeh Seyed Javad Ahmadi Sodeh Sadjadi Mohammad Outokesh 《Journal of the Iranian Chemical Society》2014,11(6):1587-1592
The current study aimed at application of the plain and supported platinum nanoparticles as a heterogenous catalyst for the reduction of aromatic nitro compounds. Monodispersed platinum nanoparticles were synthesized by reduction of H2PtCl6 by ethanol in the presence of polyvinyl pyrrolidone as a stabilizer, and then were immobilized on four types of zeolites. The obtained catalyst granules were characterized by X-ray diffractometry and transmission electron microscopy. The study then focused on elaboration of the catalytic activity of the nano catalysts under different operational conditions. It was found that reaction is adequately rapid at ambient temperature, and by utilizing a sufficient amount of catalyst, can be completed in nearly 30 min. Among the utilized zeolitic supports, zeolite 4A had the highest performance, but the mechanism of its synergetic effect on the activity of platinum nano catalyst was not found and requires more investigation. 相似文献
742.
The present study introduces Robinia tree leaves as a novel and efficient biosorbent for removing Pb(II) from aqueous solutions. In order to reduce the large number of experiments and find the highest removal efficiency of Pb(II), a set of full 2(3) factorial design with two blocks were performed in duplicate (16 experiments). In all experiments, the contact time was fixed at 25 min. The main interaction effects of the three factors including sorbent mass, pH and initial concentration of metal-ion were considered. By using Student's t-test and analysis of variances (ANOVA), the main factors, which had the highest effect on the removal process, were identified. Twenty-six experiments were designed according to Doehlert response surface design to obtain a mathematical model describing functional relationship between response and main independent variables. The most suitable regression model, that fitted the experimental data extremely well, was chosen according to the lack-of-fit-test and adjusted R(2) value. Finally, after checking for possible outliers, the optimum conditions for maximum removal of Pb(II) from aqueous solution were obtained. The best conditions were calculated to be as: initial concentration of Pb(II)=40 mg L(-1), pH 4.6 and concentration of sorbet equal to 27.3 g L(-1). 相似文献
743.
Hamid Reza Khavasi Anita Abedi Vahid Amani Behrouz Notash Nasser Safari 《Polyhedron》2008,27(7):1848-1854
The 2,2′-dimethyl-4,4′-bithiazole ligand (1), (dm4bt), and its Zn and Hg complexes have been prepared. A conformational property calculation at the DFT level for the ligand shows the anti conformation is energetically more stable by about 22.83 kJ/mol and the rotational barrier is about 32.01 kJ/mol for the anti → syn conversion, a phenomena happening during complex formation. The complexes [Zn(dm4bt)Cl2] (2) and [Hg(dm4bt)Cl2] (3) have spectral properties typical for d10 metal diimine systems. The structures of the ligand and the two complexes have been determined by the single crystal diffraction method. The X-ray structure determinations show that both complexes are four coordinated by two chloride atoms and one bidentate dm4bt. In the Hg complex one of the two chlorides is set at a semi-bridging position. 相似文献
744.
Ghasemi Y Rasoul-Amini S Morowvat MH Raee MJ Ghoshoon MB Nouri F Negintaji N Parvizi R Mosavi-Azam SB 《Molecules (Basel, Switzerland)》2008,13(10):2416-2425
A unicellular microalga, Chlamydomonas reinhardtii, was isolated from rice paddy-field soil and water samples and used in the biotransformation of hydrocortisone (1). This strain has not been previously tested for steroid bioconversion. Fermentation was carried out in BG-11 medium supplemented with 0.05% substrate at 25 degrees C for 14 days of incubation. The products obtained were chromatographically purified and characterized using spectroscopic methods. 11b,17 beta-Dihydroxyandrost-4-en-3-one (2), 11 beta-hydroxyandrost-4-en-3,17-dione (3), 11 beta,17 alpha,20 beta,21-tetrahydroxypregn-4-en-3-one (4) and prednisolone (5) were the main products of the bioconversion. The observed bioreaction features were the side chain degradation of the substrate to give compounds 2 and 3 and the 20-ketone reduction and 1,2-dehydrogenation affording compounds 4 and 5, respectively. A time course study showed the accumulation of product 2 from the second day of the fermentation and of compounds 3, 4 and 5 from the third day. All the metabolites reached their maximum concentration in seven days. Microalgal 18S rRNA gene was also amplified by PCR. PCR products were sequenced to confirm their authenticity as 18S rRNA gene of microalgae. The result of PCR blasted with other sequenced microalgae in NCBI showed 100% homology to the 18S small subunit rRNA of two Chlamydomonas reinhardtii spp. 相似文献
745.
Ahmad Reza Massah Roozbeh Javad Kalbasi Anahita Shafiei 《Monatshefte für Chemie / Chemical Monthly》2012,141(10):643-652
Abstract
ZSM-5 has been modified as supported sulfuric acid (ZSM-5-SO3H) and introduced for the first time as a mild, convenient, reusable, and heterogeneous catalyst. Various types of aldehydes were efficiently converted to their 1,1-diacetates using a catalytic amount of ZSM-5-SO3H in excellent yields under solvent-free and heterogeneous conditions at room temperature. The deprotection of 1,1-diacetates has also been achieved using this novel catalyst in ethanol. The procedure is operationally simple, environmentally benign, and only a stoichiometric amount of anhydride is used. 相似文献746.
The effect of shear strain on the iron α-ε phase transformation has been studied using a rotational diamond anvil cell (RDAC). The initial transition is observed to take place at the reduced pressure of 10.8?GPa under pressure and shear operation. Complete phase transformation was observed at 15.4?GPa. The rotation of an anvil causes limited pressure elevation and makes the pressure distribution symmetric in the sample chamber before the phase transition. However, it causes a significant pressure increase at the centre of the sample and brings about a large pressure gradient during the phase transformation. The resistance to the phase interface motion is enhanced due to strain hardening during the pressure and shear operations on iron and this further increases the transition pressure. The work of macroscopic shear stress and the work of the pressure and shear stress at the defect tips account for the pressure reduction of the iron phase transition. 相似文献
747.
Javad Azizian Farhad Hatamjafari Ali Reza Karimi 《Journal of heterocyclic chemistry》2006,43(5):1349-1352
A series of some new spiro‐1,4‐dihydropyridine derivatives have been synthesized in good yields in a four component, and solvent‐free process by condensation of isatins, primary amines, ethyl cyanoacetate and cyclohexanone on solid support montmorillonite K10 相似文献
748.
Javad Azizian Ali A. Mohammadi Ebrahim Soleimani Ali R. Karimi Mohammad R. Mohammadizadeh 《Journal of heterocyclic chemistry》2006,43(1):187-190
A mild and stereoselective three‐component one‐step synthesis of cis‐isoquinolonic acid using silica sulfuric acid as a heterogeneous catalyst from an aldehyde, amine and homophthalic anhydride in acetonitrile is described. This new method produces pure products in high yields (81‐91%). 相似文献
749.
Safari J. Naeimi H. Ghanbari M. M. Sabzi Fini O. 《Russian Journal of Organic Chemistry》2009,45(3):477-479
Russian Journal of Organic Chemistry - 相似文献
750.
MnO2/TiO2-ZrO2, which was synthesized by the adsorption method, demonstrated very high catalytic activity in the selective oxidation of benzyl alcohols to benzaldehydes with excellent yields and selectivity in short reaction times. The physical and chemical properties of MnO2/TiO2-ZrO2 were investigated by XRD, XRF, BET, FT-IR and SEM techniques. The influence of the catalyst support (SBA-15, ZSM-5, TiO2-ZrO2 and Y), type of metal oxide supported, method of loading and amount of manganese nitrate loading have been thoroughly investigated. Moreover, the catalyst has shown excellent reusability in the process. 相似文献