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排序方式: 共有1234条查询结果,搜索用时 15 毫秒
1.
通过"前驱体导入-原位沉积"的工艺路线,将水合氧化铈(HCO)纳米颗粒负载入强碱阴离子交换树脂(SAE)孔道内,制得复合纳米吸附剂HCO@SAE并用于污水中磷酸盐的深度去除。试验结果表明:与其母体材料SAE、粉末活性炭(PAC)和大孔吸附树脂XAD-4相比,HCO@SAE具有最佳的磷酸盐吸附性能。溶液pH值对HCO@SAE吸附磷酸盐的性能有较大影响,且在中性条件下可获得最大的磷酸盐吸附量(30.96 mgP/g)。得益于负载HCO纳米颗粒对磷酸盐的专属内配位络合作用,HCO@SAE能够在共存高浓度竞争离子的条件下实现对磷酸盐的选择性吸附。采用NaOH-NaCl混合溶液作为脱附剂可实现对吸附饱和HCO@SAE的高效再生,再生后吸附性能保持稳定,从而实现多批次循环吸附操作。  相似文献   
2.
近年来铈(Ce)基脱硝催化剂成为低温脱硝领域的研究热点,按载体类型可分为金属氧化物催化剂、二氧化钛载体催化剂、分子筛载体催化剂、活性炭及氧化铝载体催化剂等。按催化剂种类分别介绍了掺杂改性、制备工艺、反应条件等对催化剂性能的影响,并阐述了可能的原因机理。目前,铈基催化剂大多处于实验室阶段,工业化应用尚存在问题,尤其作为低温脱硝催化剂,活性中心堵塞问题更加突出,并且催化剂成本较高。未来可从催化剂制备工艺入手解决催化剂成型问题,以实现工业应用。同时探讨催化剂中毒机理,进一步提升其抗中毒能力。另外,寻求适宜的材料与铈掺杂组合,达到高效脱硝和经济效益最大化。  相似文献   
3.
氮氧化物是大气主要污染源之一,危害人体健康,并引发酸雨。随着环保法规的升级,氮氧化物排放浓度的限值要求越来越高。这要求脱硝工艺尤其是脱硝催化剂必须进一步提高脱硝性能。以ZSM-5分子筛为载体,以铜、铈为活性组分,制备脱硝催化剂活性组分;用铝胶将脱硝催化剂活性组分附着在蜂窝状陶瓷上,得到脱硝催化剂。与ZSM-5分子筛相比,脱硝催化剂活性组分增加了4.73%的铜(以CuO质量分数计)和5.40%的铈(以CeO2质量分数计),比表面积由287.04 m2/g降到275.05 m2/g,孔容、孔径未发生变化,酸性增强,晶型基本保持不变。脱硝催化剂最佳反应条件:反应时间≥60 min,反应温度≥250 ℃,空速≤10 200 h-1。脱硝催化剂在最佳反应条件下的脱硝效率约为85%。脱硝催化剂能适应较低的反应温度,并且具有较高的脱硝效率。  相似文献   
4.
对离子交换法和一步沉积法引进铈离子的系列Y分子筛进行了铈离子定位研究。建立了铈离子在Y分子筛中定位的简便有效的基础表征体系:利用Ce3d XPS谱获得Ce4+/Ce3+摩尔比,通过Ce3d谱及XPS定量结果分析铈离子在分子筛笼内外的存在情况;利用XRD和Py IR确定铈离子在笼内的定位。研究了不同方法引进不同含量铈离子的定位规律。结果表明,离子交换法较沉积法利于铈离子迁移进分子筛笼内,从而进一步迁移进β笼;Ce2O3质量分数为4%、8%、12%和14%时,离子交换法引进的铈离子基本能迁移进β笼。一步沉积法引进的Ce2O3质量分数为4%时,易进入β笼;更多的铈离子则易留在分子筛笼外,可用于防止重金属中毒。  相似文献   
5.
Diesel is the main source of world transportation due to higher combustion efficiency, compliance, consistency and cost-economy. It is also a major contributor to the world prosperity since it is used extensively. Diesel engine’s emissions are the serious hazard to the world environment and it is measured to be the major causes of air pollution. The demand in biofuels for years created a scope for aloe vera into biodiesels. Aloe vera, having higher calorific value vnthan other plant sources used as biodiesels, enhanced us in making another alternative biodiesel, which has lesser emissions and better performance. In this research work, four biodiesel blends from aloe vera oil with cerium oxide additive are explored for their performance and emission characteristics. The results proved B30 (30% biodiesel, 68% diesel and 1% cerium oxide) gives good performance when compared to other blends.  相似文献   
6.
The paper analyses the corrosion behaviour of naturally and artificially aged AA2024 alloy in NaCl solution and in the presence of an environment-friendly corrosion inhibitor, CeCl3. On the basis of the values of polarisation resistance and corrosion current density, the corrosion resistance of the protective inhibitor film is established as well as the general corrosion resistance of this aluminium alloy. Resistance to pit formation is determined based on the difference in pitting and corrosion potentials while resistance to pit growth is determined based on the amount of charge consumed during pit growth. A scanning electron microscope is used to examine the morphology of the pits formed during the pitting corrosion testing, as well as to determine the cerium content on intermetallic particles and the matrix AA2024 alloy. The corrosion behaviour of AA2024 alloy is investigated after different test periods in NaCl solution and in the same solution with the CeCl3 inhibitor. The corrosion resistance of both tempers of AA2024 alloy is more than one order of magnitude higher in the presence of CeCl3. An explanation of the observed differences in the corrosion behaviour of the naturally and artificially aged AA2024 alloy is proposed. Different corrosion behaviour of the alloy after different test periods is also explained.  相似文献   
7.
Four catalysts based on Ni and Ni–Ce supported on two γ-aluminas with different morphology (nanofibers and nanograins) have been prepared and studied in the dry reforming of simulated biogas. Catalysts were characterized by N2 physisorption, X-ray diffraction (XRD), temperature-programmed reduction (TPR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), inductively coupled plasma with optical emission spectrometer (ICP-OES), chemisorption of H2 and elemental analysis (EA) to determine their most relevant physicochemical properties. Characterization results show that metallic Ni particles supported on nanofibered alumina (NFA) presents a higher dispersion and smaller size than that supported on the nanograiny alumina (NGA) probably due to the higher mesoporosity presented by the NFA support. On the other hand, the incorporation of Ce has a similar effect than the fibrous morphology, decreasing also the size of the Ni metallic particles and increasing their dispersion. In the dry reforming of synthetic biogas (CH4/CO2 = 1.5) the nanofibered alumina containing 5 wt% Ni and 1.5 wt% Ce (NiCe/NFA) showed the highest catalytic activity at 750 °C (98% CO2 conversion) and stability (7.7% nickel sinterization level and 2.9 wt% carbon deposition). The stability of this catalyst was also demonstrated at 750 °C during 55 h of reaction time with a loss of activity at the steady state under 2%. In addition, the catalyst was regenerated at 600 °C in oxygen flow, recovering completely its initial catalytic performance. The excellent catalytic behavior of NiCe/NFA material has been related to the fibrous morphology of the alumina support, which promotes a better dispersion of the supported Ni metal particles, decreasing their size and increasing the number of actives sites where dry reforming reaction can take place. In addition, the incorporation of Ce seems to have also an important role by increasing the Ni-support interactions, decreasing sinterization of the metallic Ni particles and coke deposition. The contribution of both effects (morphology and Ce), separately and in combination, have been proved to enhance significantly the catalytic activity and stability of the synthesized catalysts in the dry reforming of simulated biogas.  相似文献   
8.
In this study, combustion synthesis of cerium oxide nanoparticles was reported using cerium nitrate hexahydrate as starting material as well as urea, glycine, glucose, and citric acid as fuels. The influence of fuel type on structure, microstructure, band gap, and corrosion inhibition was investigated. X-ray diffraction (XRD) patterns and scanning electron microscopy micrographs showed that CeO2 nanoparticles with different morphologies were obtained depending on the fuel type. Microstructural changes from unreacted gel to sponge-like morphologies were resulted by varying the fuel type from urea, glycine, and glucose to citric acid. In addition to Ce–O bonds, Fourier transform infrared analysis showed carbon bonds of carbonaceous compositions from incomplete combustion which were declined during combustion reaction. Furthermore, corrosion analyses showed that samples synthesized using urea fuel released the most Ce+4 ions and could have better protection than other samples.  相似文献   
9.
Nano sized La0.4F3:Ce0.45,Tb0.15(core), La0.4F3:Ce0.45,Tb0.15(Ti O2)(core) shell, La0.55F:Ce0.45, and La0.85F3:Tb0.15 particles were synthesized by adopting co-precipitation technique in acidic environment and coated with Ti O2 to form a core-shell structure by adopting a mechanical dispersion method at room temperature. The synthesized materials were characterized using X-ray diffraction(XRD), transmission electron microscopy(TEM), Fourier transform infrared spectroscopy(FTIR), ultraviolet-visible spectroscopy(UV-Vis) absorption, photoluminescence and lifetime spectroscopy. The crystal structure of La0.4F3:Ce0.45,Tb0.15 remained the same as La F3 after being doped with Ce and Tb ions but with a slight decrease in the lattice parameter. TEM image confirmed the formation of a core-shell structure. The La0.4F3:Ce0.45,Tb0.15/Ti O2 exhibited Tb3+ fluorescence enhancement by a factor of 1.76. Scintillation from the synthesized materials was also observed under X-ray excitation.  相似文献   
10.
采用真空烧结法以TiC粉、纯Mo粉、纯Cr粉、羰基Fe粉、鳞片状石墨等为原料,制备了TiC基钢结硬质合金,并采用含Ce的环烷酸稀土作为成形剂,通过加入不同含量的Ce元素对其进行改性。利用SEM、万能实验机、洛氏硬度计等对烧结试样进行显微组织和性能分析。结果表明,添加稀土元素进行改性后的合金试样接近全致密;同时,TiC更加均匀地分布于基体中;添加Ce元素质量分数为0.2%时,合金抗弯强度达到最大值,相比不含Ce的合金试样提高近28%。  相似文献   
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