Preparation and characterization of Ce-Fe-Zr-O(x)/MgO complex oxides for selective oxidation of methane to synthesize gas

A series of Ce-Fe-Zr-O(x)/MgO(x denotes the mass fraction of Ce-Fe-Zr-O,x=10%,15%,20%,25%,30%) complex oxide oxygen carriers for selective oxidation of methane to synthesis gas were prepared by the co-precipitation method.The catalysts were characterized by means of X-ray diffraction and H2-TPR.The XRD measurements showed that MgFeO4 particles were formed and Fe2O3 particles well dispersed on the oxygen carriers.The reactions between methane diluted by argon(10% CH4) and oxygen carriers were investigated.Suitable content of CeO2/Fe2O3/ZrO2 mixed oxides could promote the reaction between methane and oxygen carriers.There are mainly two kinds of oxygen of carriers:surface lattice oxygen which had higher activity but lower selectivity,and bulk lattice oxygen which had lower activity but higher selectivity.Among all the catalysts,Ce-Fe-Zr-O(20%)/MgO exhibited the best catalytic performance.The conversion of the methane was above 56%,and the selectivity of the H2 and CO were both above 93%,the ratio of H2/CO was stable and approached to 2 for a long time.     

Catalytic performance of cerium iron complex oxides for partial oxidation of methane to synthesis gas

The cerium iron complex oxides oxygen carrier was prepared by the co-precipitation method. The reactions between methane and lattice oxygen from the complex oxides were investigated in a fixed micro-reactor system. The reduced oxygen carder could be re-oxidized by air and its initial state could be restored. The characterizations of the oxygen carders were studied using XRD, O2-TPD, and H2-TPR. The results showed that the bulk lattice oxygen of CeO2-Fe2O3 was found to be suitable for the partial oxidation of methane to synthesis gas. There were two kinds of oxygen species on the oxygen carrier： the stronger oxygen species that was responsible for the complete oxidation of methane, and the weaker oxygen species （bulk lattice oxygen） that was responsible for the selective oxidation of methane to CO and H2 at a higher temperature. Then, the lost bulk lattice oxygen could be selectively supplemented by air re-oxidation at an appropriate reaction condition. CeFeO3 appeared on the oxygen carrier after 10 successive redox cycles, however, it was not bad for the selectivity of CO and H2.     

Chemical interaction of Ce-Fe mixed oxides for methane selective oxidation

Chemical interaction of Ce-Fe mixed oxides was investigated in methane selective oxidation via methane temperature programmed reduction and methane isothermal reaction tests over Ce-Fe oxygen carriers. In methane temperature programmed reduction test, Ce-Fe oxide behaved complete oxidation at the lower temperature and selective oxidation at higher temperatures. Ce-Fe mixed oxides with the Fe content in the range of 0.1–0.5 was able to produce syngas with high selectivity in high-temperature range(800–900 °C), and a higher Fe amount over 0.5 seemed to depress the CO formation. In isothermal reaction, complete oxidation occurred at beginning following with selective oxidation later. Ce1–xFexO2–δ oxygen carriers(x≤0.5) were proved to be suitable for the selective oxidation of methane. Ce-Fe mixed oxides had the well-pleasing reducibility with high oxygen releasing rate and CO selectivity due to the interaction between Ce and Fe species. Strong chemical interaction of Ce-Fe mixed oxides originated from both Fe*activated CeO2 and Ce3+ activated iron oxides(FeOm), and those chemical interaction greatly enhanced the oxygen mobility and selectivity.     

Preparation and characterization of Ce1-xFexO2 complex oxides and its catalytic activity for methane selective oxidation

A series of Ce1-xFexO2 （x=0, 0.2, 0.4, 0.6, 0.8, 1） complex oxide catalysts were prepared using the coprecipitation method. The catalysts were characterized by means of XRD and H2-TPR. The reactions between methane and lattice oxygen from the complex oxides were investigated. The characteristic results revealed that the combination of Ce and Fe oxide in the catalysts could lower the temperature necessary to reduce the cerium oxide. The catalytic activity for selective CH4 oxidation was strongly influenced by dropped Fe species. Adding the appropriate amount of Fe2O3 to CeO2 could promote the action between CH4 and CeO2. Dispersed Fe2O3 first returned to the original state and would then virtually form the Fe species on the catalyst, which could be considered as the active site for selective CH4 oxidation. The appearance of carbon formation was significant and the oxidation of carbon appeared to be the rate-determining step; the amounts of surface reducible oxygen species in CeO2 were also relevant to the activity. Among all the catalysts, Ce0.6Fe0.402 exhibited the best activity, which converted 94.52% of CH4 at 900 ℃.     

Preparation and characterization of Ce1-x NixO2 as oxygen carrier for selective oxidation methane to syngas in absence of gaseous oxygen

A citric acid complex method was employed to prepare Ce/Ni mixed oxides with various Ce/Ni ratios useful for selective oxidation methane to syngas in the absence of gaseous oxygen, and the catalytic activity measurement was investigated in a fixed bed reactor at 800 °C. The prepared oxygen carriers were characterized by various characterization techniques such as TG-DSC, XRD and TPR. The results of TG-DSC indicated that the Ce_1-xNi_xO₂ precursor generated a stable phase after the heat-treatment at temperatures above 800 °C. The XRD characterization suggested that some Ce-Ni solid solution was formed when Ni²⁺ ions was incorporated into the lattice of CeO₂, and it led to the generation of O-vacancy which could improve the oxygen mobility in the lattice of oxygen carriers. It was found that Ce_0.8Ni_0.2O₂ gave the highest activity in the selective oxidation methane to syngas reaction, and the average methane conversion, CO and H₂ selectivity reached to 82.31%, 82.41% and 87.64%, respectively. The reason could be not only attributed to the fitting amount of NiO dispersed on the CeO₂ surface and bulk but also to actual lattice oxygen amount increased in oxygen carrier.     

稀土在甲烷部分氧化制取合成气中的应用研究

稀土（La,Ce,Pr,Nd等）通常可以作为催化剂载体、助剂或与其它元素形成固溶体,成为催化剂的重要组成部分。文中系统地介绍了稀土在甲烷部分氧化（CPOM）制取合成气中的相关应用,重点分析了稀土作为催化剂载体、助剂、固溶体等在催化部分氧化制取合成气中的应用,并对其在CPOM中未来前景做出展望。     

新型太阳能选择性吸收薄膜Cu/SS-TiON(HMVF)/SS-TiON(LMVF)/Al_2O_3的制备与光学性能

对应用于太阳能光热领域的TiO_2进行掺氮,并与不锈钢(stainless steel,SS)复合,采用磁控溅射法制备SS-TiON(HMVF,high metal volume fraction)/SS-TiON(LMVF,low metal volume fraction)串联双吸收层,并制备4层结构的太阳能光谱选择性吸收光热薄膜Cu/SS-TiON(HMVF)/SS-TiON(LMVF)/Al_2O_3。利用紫外–可见分光光度计、红外光谱仪、吸收率发射率测试仪、X射线光电子能谱仪与原子力显微镜等表征该太阳能光热吸收薄膜的光学性能、成分、结构与形貌。结果表明,通过优化双吸收层的厚度与成分,沉积在Al基底上的Cu/SS-TiON(HMVF)/SS-TiON(LMVF)/Al_2O_3太阳能选择性吸收薄膜,具有较高的吸收率(0.902)和较低的发射率(0.052)。该膜系经400℃高温条件下大气退火2 h后,由于出现晶粒团聚现象,光学性能有所下降。     

Catalytic performance of Zr-doped CuO-CeO_2 oxides for CO selective oxidation in H_2-rich stream

Zr-doped CuO-CeO_2 catalysts for CO selective oxidation were designed and prepared by the hydrothermal method and coprecipitation. The experimental samples were characterized by means of N_2 adsorption-desorption isotherms, powder X-ray diffraction, temperature-programmed reduction and Xray photoelectron spectroscopy. It is observed that the catalyst prepared by hydrothermal method exhibits larger specific surface area, smaller crystalline size and higher dispersion of active components compared with those of the catalyst obtained by coprecipitation. Meanwhile, redox properties of copper oxide are improved significantly and highly dispersed copper species providing CO oxidation sites are present on the surface. Furthermore, adsorptive centers of CO and active oxygen species increase on the copper-ceria interfaces. The Zr-doped CuO-CeO_2 catalyst prepared by hydrothermal method possesses superior catalytic activity and selectivity for selective oxidation of CO at low temperature compared with those of the sample prepared by coprecipitation. The temperature corresponding to 50% CO conversion is only 73 ℃ and the temperature span of total CO conversion is expanded from 120 to 160 ℃.     

A novel catalyst of silicon cerium complex oxides for selective catalytic reduction of NO by NH3

A series of CeO2/SiO2 and SixCe1-xO2 complex oxides supported on an activated Al2TiO5-TiO2-SiO2 complex phase (ATS) ceramics were prepared by step impregnation and co-impregnation methods, and characterized by N2-BET, XRD, SEM and NH3-TPD techniques. The effects of reaction temperature, CeO2/SiO2 loadings and Si/Ce molar ratio on the granular catalysts for NO selective catalytic reduction with ammonia (NH3-SCR) were studied. Results indicated that both CeO2/SiO2/ATS and CeO2/ATS catalysts showed the same ac...     

Na2SO4/MgO复合相变蓄热材料的制备及性能研究

研究利用熔融盐Na<,2>SO<,4>的高潜热和陶瓷材料MgO的耐腐蚀等特性,采用粉末烧结工艺制备复合相变蓄热材料;对制备过程工艺参数进行初步研究;通过化学热力学分析、SEM-EDS、TG-DTA检测,对所制备材料的性能进行初步分析.这种新型复合材料兼备了固相显热蓄热材料和相变蓄热材料两者的长处,具备了快速蓄热、快速放热及蓄热密度高的性能.     

Preparation and characterization of Ce_1-xNi_xO₂ as oxygen carrier for selective oxidation methane to syngas in absence of gaseous oxygen

A citric acid complex method was employed to prepare Ce/Ni mixed oxides with various Ce/Ni ratios useful for selective oxidation methane to syngas in the absence of gaseous oxygen,and the catalytic activity measurement was investigated in a fixed bed reactor at 800 oC.The prepared oxygen carriers were characterized by various characterization techniques such as TG-DSC,XRD and TPR.The results of TG-DSC indicated that the Ce1-xNixO2 precursor generated a stable phase after the heat-treatment at temperatures above 800 oC.The XRD characterization suggested that some Ce-Ni solid solution was formed when Ni2+ ions was incorporated into the lattice of CeO2,and it led to the generation of O-vacancy which could improve the oxygen mobility in the lattice of oxygen carriers.It was found that Ce0.8Ni0.2O2 gave the highest activity in the selective oxidation methane to syngas reaction,and the average methane conversion,CO and H2 selectivity reached to 82.31%,82.41% and 87.64%,respectively.The reason could be not only attributed to the fitting amount of NiO dispersed on the CeO2 surface and bulk but also to actual lattice oxygen amount increased in oxygen carrier.     

Ce-Fe-O mixed oxide as oxygen carrier for the direct partial oxidation of methane to syngas

The Ce-Fe-O mixed oxide with a ratio of Ce/Fe=7:3, which was prepared by coprecipitation method and employed as oxygen carrier, for direct partial oxidation of methane to syngas in the absence of gaseous oxygen was explored. The mixed oxide was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), and the catalytic performances were studied in a fixed-bed quartz reactor and a thermogravimetric reactor, respectively. Approximately 99.4% H2 se...     

Preparation,characterization and catalytic oxidation property of CeO2/Cu2+- attapulgite (ATP) nanocomposites

Cerium oxide (CeO₂) coated on copper modified attapulgite clay nanocomoposite (CeO₂/Cu²⁺-ATP) was prepared by homogeneous deposition method. The microstructures of the as-prepared CeO₂/Cu²⁺-ATP nanocomposites were characterized by X-ray diffraction (XRD), energy-dispersive spectrometer (EDS) and transmission electron microscopy (TEM). The results indicated that CeO₂ particles with average size of about 5 nm were loaded onto the Cu²⁺-ATP and were widely dispersed. Comparing the catalytic activity of ATP/CeO₂ and CeO₂/Cu²⁺-ATP, the catalytic activity was improved when a small quantity of Cu²⁺ was introduced. The loading amount of CeO₂ and reaction temperature had important effects on decolorization ratio of methyl orange (MO). When the loading amount and reaction temperature were 70% and 338 K, respectively, the decolorization ratio of MO reached over 99%, which showed excellent catalytic activity.     

铜-纳米金属氧化物复合镀层的制备及组织性能研究

采用铜和纳米SiO2，TiO2粉末的复合电化学沉积，在金属表面上分别获得了金属氧化物增强Cu基复合材料镀层。对复合电沉积镀层的微观组织形貌和性能进行了分析研究。结果表明：纳米级金属氧化物粒子在电场作用下能快速沉积，形成表面致密的复合镀层，随镀覆时间的增加，复合层中微粒的粒度增加，且优先以先沉积的粒子为核心而长大。工艺参数确定后，合理选择镀覆时间就能控制复合材料的组成及沉积粒子的尺寸大小。而且参与复合的纳米级金属氧化物粒子尺寸越细小，复合镀过程中粒子的长大趋向越小，复合镀层硬度越高。     

Mercury-induced renal immune complex deposits in young (NZB x NZW)F1 mice: characterization of antibodies/autoantibodies

PURPOSE: To observe the effect of intraoperative mitomycin C on the size of the osteotomy site after dacryocystorhinostomy.: METHODS: A total of 15 eyes of 14 patients diagnosed with primary acquired nasolacrimal duct obstruction were assigned randomly to either a mitomycin C group or a control group. The surgical procedures in both groups were exactly the same, except that in the patients in the mitomycin C group, a piece of neurosurgical cottonoid soaked with 0.2 mg/ml mitomycin C was applied to the osteotomy site and then after 30 minutes was removed transnasally. Nasoendoscopic findings were recorded at the completion of the surgery and at 1 month, 3 months, and 6 months after surgery for the two groups. A computer-aided digitizer was used to calculate the surface area of the osteotomy site, and a Student's t test was used to compare the difference between the two groups. RESULTS: All patients in the mitomycin C group remained symptom free after removal of their silicone tube (100% success), and there was one patient in the control group who had recurrent epiphora (87.5% success). Septo-osteotomy adhesion was found in two patients in the control group (25%), but there was no such adhesion found in the patients in the mitomycin C group. In the mitomycin C group, the average final surface area of the osteotomy at the end of the sixth postoperative month was 27.10 +/- 5.78 mm2, whereas that of the control group was only 10.83 +/- 3.37 mm2. Although the immediate postoperative surface area of the osteotomy showed no significant difference between the two groups, a statistically significant difference was noted at 6 months. CONCLUSION: Intraoperative mitomycin C is effective in maintaining a larger osteotomy size. This modification may possibly improve success rates over the traditional dacryocystorhinostomy procedure.     

高炉渣适宜镁铝比分段管控的分析与应用

 为了给现代高炉渣适宜镁铝比(w(MgO)/w(Al2O3))提供理论依据,定性定量地指导高炉操作,针对高炉渣的适宜镁铝比问题展开研究。首先,分析了高炉渣中MgO的必要性,即在现代化大高炉的冶炼条件下,随着高Al2O3外矿用量的增加,炉渣中含有适宜的MgO是必须的。炉渣合理镁铝比可根据Al2O3质量分数不同进行分段管控：当渣中w(Al2O3)小于14%时,MgO可根据生产要求添加;w(Al2O3)为15%～17%时,适宜的镁铝比(w(MgO)/w(Al2O3))应控制在0.40～0.50,但需注意炉温的影响;当渣中w(Al2O3)大于18%时,适宜的镁铝比应控制在0.45～0.55。在理论分析与试验研究的基础上,进行了工业化应用试验。试验期炉渣镁铝比由0.51降低至0.47,高炉焦比由363.39降低至357.82 kg/t,综合燃料比由495.23降低至试验期的494.18 kg/t,取得了良好的技术经济指标,证明了现代高炉渣镁铝比分段管控技术的正确性和可应用性。     

Synthesis of mesoporous CeO2-MnOx binary oxides and their catalytic performances for CO oxidation

Mesoporous CeO2-MnOx binary oxides with different Mn/Ce molar ratios were prepared by hydrothermal synthesis and characterized by scanning electron microscopy （SEM）, N2 sorption, X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS） and H2 temperature-programmed reduction （H2-TPR）. The characterization results indicated that the CeO2-MnOx catalysts exhibited flower-like microspheres with high specific surface areas, and partial Mn cations could be incorporated into CeO2 lattice to form solid solution. The CeO2-MnOx catalysts showed better catalytic activity for CO oxidation than that prepared by the coprecipitation method. Furthermore, the CeO2-MnOx catalyst with Mn/Ce molar ratio of 1 in the synthesis gel （Ce-Mn-1） exhibited the best catalytic activity, over which the conversion of CO could achieve 90% at 135 ℃. This was ascribed to presence of more Mn species with higher oxida- tion state on the surface and the better reducibility over the Ce-Mn-I catalyst than other CeO2-MnOx catalysts.