Low-cost catalysts for the control of indoor CO and PM emissions from solid fuel combustion

Cu-Mn based mixed oxide type low-cost catalysts have been prepared in supported form using mesoporous Al(2)O(3), TiO(2) and ZrO(2) supports. These supports have been prepared by templating method using a natural biopolymer, chitosan. The synthesized catalysts have been characterized by XRD, BET-SA, SEM, O(2)-TPD and TG investigations. The catalytic activity for CO as well as PM oxidation was studied, in a view of their possible applications in the control of emissions from solid fuel combustion of rural cook-stoves. The trend observed for the catalytic activity of the synthesized catalysts for CO oxidation was ZrO(2)>TiO(2)>Al(2)O(3) while for PM oxidation it was observed to be TiO(2)>ZrO(2)>Al(2)O(3). The effect of CO(2), SO(2) and H(2)O on CO oxidation activity was also investigated, and despite partial deactivation, the catalysts show good CO oxidation activity. An effective regeneration treatment was attempted by heating the partially deactivated catalysts in presence of oxygen. Redox properties of TiO(2) and ZrO(2) and their structure appeared to be responsible for their promotional activity for CO and PM oxidation reactions. These unordered mesoporous materials could be useful for such reactions where mass transfer is more important than shape and size selectivity.     

X-ray investigation of solid solution partitioning in 2.25Cr-1Mo steel after extended elevated temperature service in power station

Abstract

Carbide phase transformation and alloying element partitioning in service exposed (about 45 000-160 000 h) 2.25Cr-1Mo boiler tubes from a thermal power station were studied using X-ray diffraction and X-ray fluorescence techniques on electrochemically extracted carbide precipitates. The objective of the present investigation was to develop a faster method of health assessment of this steel at elevated temperatures on a routine basis. Various carbide phases were detected with different lengths of service. The molybdenum content in extracted carbide specimens showed a systematic decrease with aging. Replenishment of molybdenum in the matrix may be a useful indicator in life assessment of this steel. When the dissolved molybdenum content in the matrix was less than ~0.8 wt-%, the hardness of service exposed specimens was found to decrease. However, carbide precipitates extracted from new specimens subjected to accelerated heat treatment at 600 and 700 ° C showed an increase in molybdenum content with increase in temperature. The X-ray data were supplemented by microscopy, EDAX and hardness measurements.     

Numerical investigation for prediction of pollutants formation type CO and NO in premixed turbulent flame using an extended coherent flame model

This study describes a numerical effort to predict pollutant species such as CO and NO formed in premixed turbulent flame using an extended coherent flame model. This model is used to predict pollutant emissions of methane-air combustion. A semi-global kinetic scheme is tested, using a two steps reaction mechanism of Westbrook and al. The model combines coherent flame model to estimate the CO formation and the well-stirred reactor concept for calculating the NO and all other species which are taken into account in this investigation. Essentially, we assume that CO is analysed near the flame zone because is formed with very fast intermediate reaction compared to the other characteristic times. Other species formed with longer time are supposed to take place in high temperature region where can be consider that corresponding kinetics are best represented by homogeneous reactor conditions. Numerical results for emission species and dynamic parameters in premixed flame of methane-air are given for a duct combustor where the flame is stabilised behind a rod flame holder with a blockage ratio is taken as 6% and a mass flow rate $\dot{m}$ _a=35 g/s.     

络合法制备Ce-Zr-O固溶体作为CO_2重整CH_4催化剂载体的研究

以草酸、柠檬酸、甘氨酸、聚乙烯吡咯烷酮(PVP)为络合剂,采用络合分解法制备Ni-Ce-ZrO2催化剂,考察了所制备Ni-Ce-ZrO2催化剂的CO2重整CH4催化性能,并对所得催化剂进行了XRD、BET和H2-TPR表征。实验结果表明,不同络合剂对催化剂的晶型结构有很大影响,以PVP为络合剂更有利于形成均匀的Ce-Zr-O立方固溶体,且催化剂PVP-NiCeZr具有较大的比表面积、孔容和孔径,在反应中也具有最高的CH4和CO2转化率,其初始转化率分别为83.3%和87%,合成气中H2/CO接近于1。PVP-NiCeZr表现出良好的反应稳定性,反应后100h其热失重率仅为1.8%,这归因于Ce-Zr-O立方固溶体结构更有利于活性氧的移动,增加了催化剂表面积炭与氧的接触,提高了催化剂的抗积炭性能,也有利于提高Ni活性组分的抗烧结团聚能力。     

相变燃料电极实现固体氧化物电池高效可逆CO/CO2转化

固体氧化物电池可实现CO/CO₂的可逆转化,在电能和化学能相互转化过程中显示出巨大潜力.然而,其商业化进展一直受到燃料极抗积碳性能差的限制.本工作中,我们发展了一种CoFe合金纳米颗粒和Ruddlesden-Popper层状结构Sr₃Fe_1.25Mo_0.75O₇-δ复合新型燃料电极(CoFe-SFM),其可以通过钙钛矿Sr₂Fe_7/6Mo_0.5Co_1/3O_6-δ在还原气氛中退火发生相变得到.电化学阻抗谱和弛豫时间分步法分析可知CoFe-SFM电极通过改善体相氧化学扩散能力和表面氧交换过程来增强CO氧化和CO₂还原动力学.在固体氧化物燃料电池模式下,800℃的最大功率达到259 mW cm^-2;在固体氧化物电解电池模式下,1.3 V工作电压下单电池的电解电流密度为-0.453 A cm^-2,都远超对比电极材料.在20次SOFC-SOEC循环操作条件下,CoFe-SFM燃料极依然保持稳定的微结构和抗积碳性能,电池性能保持良好.该工作可为CO₂转化、抗积碳电极材料设计和提升电极表界面反应动力学提供一定的指导作用.     

CuO促进Ce_xZr_(1-x)O_2固溶体催化剂用于低温CO选择氧化的研究

采用共沉淀法制备了一系列催化剂,并利用XRD,XPS对催化剂结构进行了表征,考察了铜掺杂量,焙烧温度,空速以及CO_2和H_2O的存在对选择氧化消除CO反应的影响。结果表明,在600℃焙烧后的催化剂具有最佳的催化活性和选择性,而且在CO_2和H_2O的存在下140℃也能达到有效消除CO(100 ppm以下)的目的,同时选择性可达到了70．1%。100h的连续测试显示,催化剂具有良好的稳定性。     

Glass dispersion favours ionic conduction in 6Li2SO4-4Li2CO3 composite solid electrolyte

The effect of a dispersion of 7Li₂O-3B₂O₃ glass on the electrical conductivity of 6Li₂SO₄-4Li₂CO₃ eutectic has been studied. The samples were prepared by two different methods. With the dispersion of glass into the crystalline matrix a prominent increase in the conductivity has been observed. The results have been explained in the light of dispersed phase theory using microstructural evidence. These results would provide a new approach for achieving an enhancement in the ionic conductivity of solid electrolytes.     

Isotype Heterojunction-Boosted CO2 Photoreduction to CO

Photocatalytic conversion of CO2 to high-value products plays a crucial role in the global pursuit of carbon-neutral economy.Junction photocatalysts,such as the...     

Double-lens extended fractional Fourier transform

A double-lens extended fractional Fourier transform (EFRT) is proposed. In the double-lens setup, arbitrary-order EFRTs including real orders and complex orders can be carried out. To verify that the single-lens EFRT and the double-lens EFRT are equivalent, numerical simulations and optical experiments for the real-order EFRT and the complex-order EFRT are performed. Their results indicate that the double-lens EFRT is consistent with the single-lens EFRT. Thus the double-lens setup can be regarded as another basic optical configuration. Compared with the single-lens EFRT, the double-lens EFRT has some advantages.