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排序方式: 共有2371条查询结果,搜索用时 15 毫秒
71.
Xiu Ling ZHANG Wei Min GONG* Bin DAI Chang Hou LIU Plasma Chemistry Laboratory Dalian University of Technology Dalian Center of Analysis Dalian Institute of Light Industry Dalian 《中国化学快报》2002,(2)
The oxidative coupling of methane (OCM) to C2 hydrocarbons using carbon dioxide as oxidant is an attractive process from environmental point of view. Only a few research papers reported for it1-3. In general, the yield of C2 hydrocarbons was about 6%. This indicated that the method of catalytic activation was unfavorable to the reaction. It is necessary for us to find a new method in order to activate reaction and improve C2 hydrocarbon yield. Non-equilibrium plasma is a cold plasma in… 相似文献
72.
Direct Synthesis of Oxygenates from Water and Methane via Dielectric-barrier Discharge 总被引:1,自引:0,他引:1
BaoWeiWANG GenHuiXU 《中国化学快报》2004,15(7):779-780
In this investigation, a clean, atomic economic and direct synthesis of oxygenates (methanol, ethanol) form water and methane via dielectric-barrier discharge was developed at room temperature and under atmospheric pressure. The effect of discharge voltage on this process was studied. The results showed that the conversion of water can be as high as 7%, the selectivity of methanol and ethanol can be as high as 100%. 相似文献
73.
A comparative study of pretreatment methods for the determination of 10 elements (As, Cd, Pb, V, Ni, Mn, Cr, Cu, Fe, Al) in atmospheric aerosols by electrothermal atomic absorption spectrometry (ETAAS) was conducted. For the digestion of the particulates collected in filters, six methods were compared using a mixture of HNO3 and HF with or without the addition of various oxidative agents (HClO4 or H2O2) or acids (HCl). The comparative study was performed using loaded cellulose filter samples, which were digested in Parr bombs and heated in a conventional oven at 170 °C for 5 h. The extraction efficiency and blanks were compared and it was proved that the digestion method using only HNO3–HF extracted most of the metals and gave the lowest blanks. The HNO3–HF mixture was selected for the development of an improved microwave digestion method specific for aerosol-loaded filters. The operating parameters were optimized, so that quantitative recovery of the reference materials NIST 1649a urban dust and NIST 1648 urban particulate matter was achieved. The blank of cellulose and teflon filters were also determined and compared. Teflon filters present the lowest blanks for all the elements. The obtained limits of detection for each type of filters were adequate for environmental monitoring purposes. ETAAS instrumental operation was also optimized for the compensation and the elimination of interferences. The temperature optimization was performed for each metal in every type of filter and optimized parameters are proposed for 10 elements. 相似文献
74.
JinguangXu ZhijianTian JunweiWang YunpengXu ZhushengXu LiwuLin 《天然气化学杂志》2003,12(2):105-112
Conventional oven drying (COD) and supercritical drying (SCD) methods were applied to the preparation of Mn-substituted hexaaluminate (BaMnA111O19-α) catalysts. The effect of drying methods on phase composition, specific surface area, pore structure, reduction behavior of Mn^3 ions, and combus-tion activity of the samples was investigated. The homogenous mixing of the components in the sol-gel process could be maintained by SCD, and the hexaaluminate phase was almost the only phase of the resulting materials after calcination. H2-TPR revealed that the Mn^3 ions in the sample obtained by SCD were easier to be reduced than that by COD. Moreover, the samples obtained by SCD have higher surface area, narrower pore size distribution, and higher combustion activity than those obtained by COD. 相似文献
75.
使用穆斯堡尔谱,ESR和XRD等技术表征了未添加助剂和添加LiCl的Fe2O3/SiO2催化剂.XRD结果指出,添加LiCl的Fe2O/SiO2催化剂出现铁酸盐和α-方石英的衍射峰,这种结果的出现与该催化剂有较高的C2烃选择性密切相关。穆斯堡尔谱结果表明:添加LiCl的Fe2O3/SiO2催化剂有更高的结构对称性.这种结构对分子氧的活化起着重要的作用.氯的存在大大降低了氧的离解吸附的速率,减少了原子氧的吸附位的数目,并可除去吸附的原子氧,该氧种对COx的生成有利. 相似文献
76.
《天然气化学杂志》1995,(2)
The catalytic performance of Mn/TiO_2,La-Mn/TiO_2,Li-La-Mn/TiO_2 etc for the oxidetive coupling of methane(OCM)was investignted.Thecatalysta were cheracterised with X-ray diffraction(XRD)and X-rayphotoelectron spectroscopy(XPS).The results reveal that catalyst Li-La-Mn/TiO_2 exhibits high activity and C_2 selectivity;Ti in this catalyst exists asTi~( 4) state;Li can promote the formation of lanthanum tituate via theinteraction between La and TiO_2;the formed La_2Ti_2O_7 and La_4Ti_9O_(24) aredistributed in the inner surface layer and Mn exists in outer surface layer in lowvalence states.The high activity and C_2 selectivity of catalyst Li-La-Mn/TiO_2are intimately related to the valence states of Mn,Li,La and theirdistribution on the catulyst surface layer. 相似文献
77.
从甲基弯菌M ethylosinus trichosporium IMV3011的膜中分离出颗粒性甲烷单加氧酶(Particulate MMO,Pmmo)t和NADH脱氢酶,只有当两者同时存在,并添加去垢剂解离膜组分时,NDAH才能为pMMO提供还原当量,对苯二酚能够在整细胞和膜水平代替NADH作为PMMO的电子供体,对于纯化的PMMO,对苯二分配仍是有效的电子供体,而NADH却是无效的电子供体。在NADH脱氢酶存在下,NADH可将对苯醌还原为对苯二酚,纯化过程中,采用对苯二酚作为PMMO活性分析时的电子供体,不必共纯化NADH脱氢酶,且有利于对PMMO活性中心进行深入研究。 相似文献
78.
甲烷氧化偶联反应在不同催化剂体系上动力学的研究各不相同,我们已报道了La-Ba-O系复合氧化物催化剂对此反应的优良催化性能。本文则是对该催化剂上的甲烷氧化偶联反应的动力学进行初步探讨。 相似文献
79.
80.
LIN Jun-Fan YAN Ya-XieDepartment of ChemistryInstitute of Chemistry Chemical EngineeringNanjing UniversityNanjing Jiangsu 《天然气化学杂志》1995,(2)
A series of perovskite type oxides La_(1-x)A_(x)MnO_3(x=0.1 for A=Li,Na,K;x=0.1~0.5 for A=Li)have been prepared by impregnation.Experimental results showed that the substitution of La~(3 ) by Li~ inLaMnO_(3 ?) greatly increased the selectivity to ethane and ethylene for theoxidative coupling of methane.Temperature-programmed desorption of oxygenproved the presence of oxygen vacancies in the oxide lattice.The higher Mn~(4 )/Mn_t ratio in oxide made the formation of oxygen vacancies easier on the oxidesurface.The general formula of the oxides is La_(1-x)Li_(x)Mn'V'_(y)O_(3-y),V=vacancy. 相似文献