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991.
Luca Lietti 《Applied catalysis. B, Environmental》1996,10(4):281-297
The reactivity of ternary V2O5&z.sbnd;WO3TiO2 de-NOxing catalysts with compositions similar to those of commercial catalysts (WO3 ca. 9% w/w, V2O5 < 2% w/w) is investigated by transient techniques (temperature programmed desorption, TPD; temperature programmed surface reaction, TPSR; and temperature programmed reaction, TPR). The results indicate that the reactivity of the ternary catalysts in the SCR reaction increases on increasing the vanadia loading, and that the ternary catalysts are more active than the corresponding binary vanadia-titania samples with the same V2O5 loading. Indeed the SCR reaction is monitored at lower temperatures and high NO conversions are also preserved at high temperatures. TPSR and TPR data show that at low temperatures the SCR reaction occurs via a redox mechanism that involves at first the participation of the catalyst lattice oxygen and then the reoxidation of the reduced sites by gas-phase oxygen. Based on TPSR and TPR data, the higher reactivity of the ternary catalysts has been related to their superior redox properties, in line with previous chemico-physical characterisation studies. The catalyst redox properties thus appear as a key-factor in controlling the reactivity of V2O5&z.sbnd;WO3TiO2 de-NOxing catalysts at low temperatures. The results also show that at high temperatures the surface acidity plays an important role in the adsorption and activation of ammonia. 相似文献
992.
不同的溶剂对煤直接液化过程产生不同的影响,其组成和性质决定了反应进行的途径。本文介绍了进行该项研究的试验装置和工艺过程,从试验结果得出了三种不同溶剂即HAO,DAO和循环溶剂对煤液化产物及各项收率的影响。 相似文献
993.
994.
《International Journal of Hydrogen Energy》2020,45(35):17504-17516
Fabrication of an electrocatalyst with remarkable electrocatalytic activity for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is important for the production of hydrogen energy. In this study, Ni–Co–W alloy urchin-like nanostructures were fabricated by binder-free and cost-effective electrochemical deposition method at different applied current densities and HER and OER electrocatalytic activity was studied. The results of this study showed that the microstructure and morphology are strongly influenced by the electrochemical deposition parameters and the best electrocatalytic properties are obtained at the electrode created at the 20 mA.cm−2applied current density. The optimum electrode requires −66 mV and 264 mV, respectively, for OER and HER reactions for delivering the 10 mA cm−2 current density. The optimum electrode also showed negligible potential change after 10 h electrolysis at 100 mA cm−2, which means remarkable electrocatalytic stability. In addition, when this electrode used as a for full water splitting, it required only 1.58 V to create a current density of 10 mA cm−2. Such excellent electrocatalytic activity and stability can be related to the high electrochemical active surface area, being binder-free, high intrinsic electrocatalytic activity and hydrophilicity. This study introduces a simple and cost-effective method for fabricating of effective electrodes with high electrocatalytic activity. 相似文献
995.
在碳酸盐岩地区,水电站的兴建会改变库坝区地下水流场,由此引起溶蚀及渗漏问题。为研究灰岩在实际条件下的平均反应速率,在常温常压条件下、相对开放的体系中进行了5组灰岩试样的室内溶解试验,对溶液的电导率、pH值和温度等进行定时检测。根据化学动力学的基本理论,建立了两组不同模型以反映溶解速率与电导率之间的函数关系,依据实测的三组溶液电导率值,求得平均反应速率参数,并将其代入另两组试验进行验证,结果较为一致。由此表明,基于电导率所建的模型可以有效地反映灰岩在实际条件下的溶解过程,可为建立灰岩介质中的反应—运移模型提供化学动力学参数。 相似文献
996.
用非等温热重分析方法对膨胀聚苯乙烯泡沫的热氧化分解特性进行了研究.样品在空气气氛下由10,℃/min、20,℃/min、40,℃/min和50,℃/min共4个升温速率从室温加热至800,℃.分别使用积分等转化率方法中的Flynn-Wall-Ozawa(FWO)和Kissinger-Akahir-Sunose(KAS)方法以及基于动力学补偿效应的恒定动力学参数方法(invariant kinetic parameter method,IKP)计算膨胀聚苯乙烯非等温热氧化分解的动力学参数.由等转化率方法得到的结果可认为膨胀聚苯乙烯泡沫在空气气氛下主要为一步反应.FWO方法和KAS方法得到的平均活化能与IKP方法得到的活化能具有较好的一致性.由IKP方法和常用固相反应机理函数在不同升温速率下动力学参数的对应准则可确定膨胀聚苯乙烯泡沫热氧化分解过程可由成核和核生长控制的机理函数(Avrami Eroféev方程)A1.7描述. 相似文献
997.
Justin C. TokashBruce E. Logan 《International Journal of Hydrogen Energy》2011,36(16):9439-9445
There is great interest in hydrogen evolution in bioelectrochemical systems, such as microbial electrolysis cells (MECs), but these systems require non-optimal near-neutral pH conditions and the use of low-cost, non-precious metal catalysts. Here we show that molybdenum disulfide (MoS2) composite cathodes have electrochemical performance superior to stainless steel (SS) (currently the most promising low-cost, non-precious metal MEC catalyst) or Pt-based cathodes in phosphate or perchlorate electrolytes, yet they cost ∼4.5 times less than Pt-based composite cathodes. At current densities typical of many MECs (2-5 A/m2), the optimal surface density with MoS2 particles on carbon cloth was 25 g/m2, achieving 31 mV less hydrogen evolution overpotential than similarly constructed Pt cathodes in galvanostatic tests with a phosphate buffer. At higher current densities (8-10 A/m2) the MoS2 catalyst had 82 mV less hydrogen evolution overpotential than the Pt-based catalyst. MoS2 composite cathodes performed similarly to Pt cathodes in terms of current densities, hydrogen production rates and COD removal over several batch cycles in MEC reactors. These results show that MoS2 can be used to substantially reduce the cost of cathodes used in MECs for hydrogen gas production. 相似文献
998.
Heat and mass transfer with electrochemical reaction in an anode-supported flat-tube solid oxide fuel cell (FT-SOFC) is studied by means of three-dimensional numerical simulation. The distributions of the reaction fields in the anode-supported FT-SOFC are found to be similar to those in the planar SOFC with co-flow arrangement. However, in comparison with the latter, the concentration and activation overpotentials of the former can be reduced by additional reactant diffusion through the porous rib of the fuel channel. Parametric survey reveals that, for a fixed activation overpotential model, the output voltage can be improved by increasing the pore size of anode, while the cross-sectional geometry has smaller effect on the cell performance. Based on the results of three-dimensional simulation, we also develop a simplified numerical model of anode-supported FT-SOFC, which takes into account the concentration gradients in the thick anode of complex cross-sectional geometry. The simplified model can sufficiently predict the output voltage as well as the distributions of temperature and current density with very low computational cost. Thus, it can be used as a powerful tool for surveying wide range of anode-supported FT-SOFC design parameters. 相似文献
999.
1000.
主要分析了脱硫反应产物层形成过程中的传递反应过程特性。研究发现,脱硫剂颗粒产物层形成过程与蒂勒数密切相关,至产物层形成时转化率仅仅决定于蒂勒数,随蒂勒数的增加而降低,与此阶段持续的时间无关,蒂勒数是描述脱硫反应产物层形成过程中传递反应特性的重要参数,它同时反映了化学反应速度、扩散速度的影响。本文还考察了粒径、孔隙分布方式以及温度对反应过程的影响,证实了随着温度和孔隙率的升高反应转化率相应提高,反应平均孔径在100~300nm之间的孔隙更利于进行脱硫反应,热重分析(TGA)实验结果进一步证实了理论分析的正确性。 相似文献