不同Pt-SnO2制备工艺对乙醇燃料电池性能影响

本文在石墨烯改性碳纤维的基础上,通过添加聚偏氟乙烯(PVDF)造孔、浸渍法、水热法制备出不同的Pt-SnO2/改性碳纤维阳极催化剂。以扫描电镜(SEM)、X射线衍射仪(XRD)、拉曼光谱图、电催化性能、单电池发电性能等手段来表征和测试,结果表明添加PVDF造孔后催化剂催化性能最好,峰电流密度可达137.33mA.cm-2,其电阻也明显减少,当制备成单电池时也具有最高功率密度,为22.89 mW.cm-2。     

Uniform-sized molecularly imprinted polymer for metsulfuron-methyl by one-step swelling and polymerization method

Uniform-sized molecularly imprinted polymer (MIP) beads for metsulfuron-methyl (MSM) were firstly prepared by one-step swelling and polymerization method using 4-vinylpyridine (4-VPY) and ethylene glycol dimethacrylate (EDMA) as functional monomer and cross-linker, respectively. The preparation was optimized by varying the ratio of MSM to 4-VPY. The chromatographic behaviors of MSM and other structurally related sulfonylureas (SUs) on the resultant MIP column were evaluated. The imprinted polymer revealed specific affinity to the template and the fair resolution of SUs was also obtained. Furthermore, the uniform-sized MSM-MIP was used as the solid phase extraction (SPE) material to enrich MSM in real water samples before reversed-phase HPLC (RP-HPLC) analysis. The recovery of MSM from 100 mL of drinking water at a 50 ng/L spike level was 99.59% with R.S.D. of 1.13%. The detection limit was about 6.0 ng/L of MSM when enriching a 100 mL water sample.     

A selective one-step synthesis of tris N-alkylated cyclens

A general one-step synthesis for tris N-alkylated cyclens with good yield and unprecedented selectivity is presented. Tris and 1,4-bis N-alkylated cyclens, as the only two major products are isolated. Furthermore, according to the single crystal X-ray structures of tris and 1,4-bis N-alkylated cyclen 1 and 1a, one nitrogen atom on the cyclen ring can be protonated under this reaction condition, which prevents its further alkylation, and gives rise to the regioselectivity ultimately.     

Applicability of the Kissinger equation in thermal analysis

Pt/WO_x–ZrO₂ bifunctional catalysts were synthesized using impregnation and polymeric precursor methods. After the synthesis process the samples were calcined at 600, 700 and 800°C and characterized by X-ray diffraction, nitrogen adsorption and temperature programmed reduction study by thermogravimetry. DTG-TPR profiles showed between three and five reduction events at different temperatures attributed to platinum reduction and to different stages of tungsten species reduction. A comparative study of the synthesis method influence on the DTG-TPR curves was accomplished.     

Convenient one-step synthesis of 5-carboxy-seminaphthofluoresceins

The one-step synthesis and characterization of a series of regioisomerically pure 5-carboxy-seminaphthofluoresceins (5-carboxy-SNAFLs) is reported. The optical properties were determined in aqueous buffer at around biological pH, and highly pH sensitive, large Stokes-shift fluorophores with emission in the deep-red to near-infrared region were identified.     

介孔纳米 MoPO-AlPO4 的制备及其对异丁烯选择氧化的催化性能

 分别采用溶胶-凝胶法和等体积浸渍法制备了 MoPO-AlPO4 催化剂, 考察了钼物种存在状态对催化剂晶格氧活性以及异丁烯选择氧化反应性能的影响. N2 吸附-脱附、X 射线衍射、高分辨透射电镜、X 射线光电子能谱、傅里叶变换红外光谱、程序升温还原和微反实验结果表明, 与浸渍法制备的催化剂相比, 溶胶-凝胶法制备的 MoPO-AlPO4 催化剂为介孔纳米材料, 其比表面积和孔数量均有较大程度的提高. 在浸渍法制备的催化剂中, 钼物种以四面体 MoO42− 和八表面体 MoO66− 形式存在; 而在溶胶-凝胶法制备的催化剂中钼物种主要以四面体 MoO42− 的形式存在, 并有部分钼物种嵌入到了 AlPO4 骨架中. 钼物种的种类对异丁烯选择氧化反应的活性和选择性有较大影响, 溶胶-凝胶法制备的催化剂由于嵌入 AlPO4 骨架中钼物种的存在, 异丁烯选择氧化反应性能得到较大提高.     

Influence of preparation method on the structure and catalytic activity of supported solid sulfuric acid

Summary FT-IR and ²⁹Si-NMR studies suggested the interaction of H₂SO₄ with the SiO₂ support in the material synthesized by the sol-gel method. ¹H-NMR results showed that the acid strength of solid sulfuric acid was almost the same as that of liquid sulfuric acid. The catalyst showed higher catalytic activity and stability than that prepared by impregnation method.     

Characterization of the active phase of NiMo/Al2O3 hydrodesulfurization catalysts

The active phase of the NiMo/Al₂O₃ catalyst for hydrodesulfurization reactions has been investigated in this work. Special attention has been focused on the effect of the order of metal impregnation on the formation of the active phase in the reaction. The Mo and Ni oxides and their sulfides on the alumina were investigated by XPS and DRS analyses. The Ni-Mo oxides or precursor of the active phase which are chemically bonded between Mo and Ni were also confirmed from the binding energy shifts of the XPS peaks. The amount of Ni-Mo oxides was determined after the formation of metal oxides during calcination. The Ni-Mo sulfide (active phase) was then induced through sulfidation. It was important that Mo should be located at the tetrahedral sites on the alumina with a high Mo dispersion. These results indicated that there are two important factors in preparing highly efficient Ni-Mo catalysts; one is that Mo should be located at the tetrahedral coordination on Al₂O₃ in high dispersion (Mo/Al₂O₃) and the other is that the Ni species should be supported on MoAl₂O₄ to form Ni-Mo oxides which change into the Ni-Mo sulfide active sites by sulfidation.     

Spectroscopic analysis and in situ monitoring of impregnation and extraction of polymer films and powders using supercritical fluids

A range of vibrational spectroscopic techniques are used to monitor supercritical fluid extraction and impregnation of polymers. Impregnation processes of this type show potential as alternative apporaches to the synthesis of polymer based catalysts and new materials. Methods have been devised using conventional Fourier transform infrared spectroscopy for real time monitoring of the extraction and impregnation of polyethylene films using an organometallic complex, CpMn(CO)₃ (Cp = η⁵ ? C₅ H₅) as a spectroscopic probe. Both low and high density powdered polyethylene may be impregnated using supercritical carbon dioxide. The resulting materials are analysed using FTIR photoacoustic spectroscopy, diffuse reflectance infrared spectroscopy and FT Raman spectroscopy to probe both the impregnated bulk of the polymer and surface-coated material. © 1994 John Wiley & Sons, Inc.     

One-step synthesis of inherently chiral p-tert-butylcalix[4]azacrown

A one-step procedure is developed to synthesize inherently chiral p-tert-butylcalix[4]azacrown 1 through etherification between p-tert-butylcalix[4]arene and compound 3, which can be amplified to efficiently prepare more inherently chiral calix[4]arenes in ABHH substitution pattern.