A novel fused iron catalyst for ammonia synthesis promoted with rare earth gangue

Rare earth gangue, which mainly consists of mixtures of light rare earths such as lanthana, ceria, neodymium oxide and praseodymium oxide, was used as the promoter of fused iron catalysts for ammonia synthesis. The result showed that the activity of the catalyst promoted with rare earth gangue was comparable with those of commercial iron catalysts with high amount of cobalt. The role of rare earths was owed to their advantages for favoring the deep reduction of the main composite in catalyst, i.e., iron oxide. This fmding indicated that the use of rare earth gangue could decrease the content of cobalt or even completely replace cobalt, which was used to be regarded as unsub- stitutable promoters for high performance ammonia catalyst; therefore, the cost of fused iron catalysts would decrease significantly.     

Bridging complexes of rare earth and cobalt cluster as catalyst precursors for Fischer-Tropsch synthesis

Three new bridging complexes of rare earth and cobalt cluster were synthesized and characterized via ICP, IR and TG techniques. The structure of the complexes was speculated as: two rare earth atoms were bridged with four CF3COO-, and rare earth atoms were coordinated with cobalt carbonyl clusters to form a steady structure. Application of the complexes as the catalyst precursors was explored for Fischer-Tropsch synthesis. The study showed that the bridging complexes of rare earth and cobalt cluster had large molecular size and were difficult to enter pore path of γ-Al2O3, so they were dispersed on the surface of γ-Al2O3 support. In addition, the performance of Co(Ce)/ γ-Al2O3 was the best among the catalysts with complex as precursor and maintained 77.7% CO conversion at 220 oC for 80 operation hours.     

Rare earth modified Ni-Si catalysts for hydrogen production from methane decomposition

Different rare earth(RE=La, Ce, Pr, Nd, Sm, Y) and Cu modified nickel catalysts for hydrogen production from methane decomposition were synthesized by a sol-gel process and method. The catalysts were characterized or analyzed through Brumauer-Emmett-Teller(BET), X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM) techniques. And the hydrogen production performance was also evaluated by a fixed-bed and micro-reaction technique with CH4→C+H2 as a probe reaction. The results showed that rare earth modification had played a great role for nickel catalysts, for example, smaller nickel particles, good thermal stability, high activity, etc. La was the best additive among rare earth modification. The SEM of rare earth modified catalysts showed ordered flower-like structure and rare earth modification made the nickel particles move to the surface of catalysts. In addition, the SEM of nano-carbons was also changed by rare earth modification with long, narrow nano-carbon fibers or tubes obtained. Solid carbon formation was prevented by rare earth modification.     

Microwave strengthens decomposition of mixed rare earth concentrate: Microwave absorption characteristics

The potential application of microwave heating technology for processing the mixed rare earth concentrate was systematically investigated by analyzing the microwave absorption characteristics in this study. The complex permittivity was measured through resonant cavity perturbation method. The variations of permittivity, the loss factor, loss tangent and the penetration depth with the increasing temperature were investigated numerically. The results indicate that the permittivity increases as the temperature increases, and temperature has a pivotal effect on it. The mixed concentrate is high loss material at the temperature range from 600 to 800℃ according to theoretical analyses of loss tangent and penetration depth. The results of phase transition analysis prove that the variation of microwave absorption characteristics of mixed concentrate is caused by the changes of crystal and lattice structures.The reflectivity, loss factor and penetration depth of the mixed concentrate were also calculated, and the results indicate that processing the mixed concentrate by microwave heating is of high feasibility and industrial potential.     

稀土镧改性磷钨杂多酸盐催化油酸与甲醇酯化反应合成生物柴油活性研究

以H ₃PW ₁₂O ₄₀和La(NO ₃) ₃为原料,通过离子交换法制备一种稀土镧改性磷钨杂多酸盐催化剂.通过扫描电镜、红外光谱和X射线粉末衍射等表征方法,对合成的催化剂的物理及化学性能进行分析,进而通过以油酸和甲醇为反应物的酯化反应,对其催化活性进行研究.结果表明:稀土镧已经导入磷钨杂多酸的骨架结构,并与杂原子P形成配位键,有效提高磷钨杂多酸的比表面积和孔径;合成的催化剂具有完整的Keggin型结构;当反应温度为62 ℃,油酸与甲醇摩尔比为1∶6,反应时间为4.5 h,催化剂用量为反应物质量的2.5 %,油酸的转化率可达88.0 %.      

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。     

Lewis酸型固体酸催化剂Ce-Ag-PW的制备、表征及催化酯化反应合成生物柴油性能研究

通过超声浸渍法,经Ce3+和Ag+协同改性磷钨杂多酸（HPW）制备了一种以Lewis酸性活性位为主的固体酸催化剂Ce-Ag-PW。采用X射线衍射（XRD）、傅里叶变换红外光谱（FT-IR）、扫描电镜（SEM）、透射电镜（TEM）、热重（TG）、NH₃程序升温脱附（NH₃-TPD）、吡啶吸附红外光谱（Py-IR）和X射线光电子能谱（XPS）等表征手段对其物理化学性能进行了表征分析。并以Ce-Ag-PW为经甲醇和油酸酯化反应来合成生物柴油的催化剂,对其的催化活性和稳定性进行了研究。结果表明,Ce-Ag-PW具有高催化活性和稳定性,以其为催化剂,当甲醇与油酸的物质的量比为14: 1,催化剂用量为反应物总质量的2%,反应温度为65 ℃,反应6 h后,油酸的转化率即高达91%。固体酸催化剂在经过4次循环使用后,油酸的转化率仍可达到80.5%。Ce-Ag-PW的高催化活性和稳定性可归因于Ag+可置换HPW中的质子,以及Ce3+的强吸电子作用,使其由Br?nsted酸型催化剂转化为以Lewis酸型为主的催化剂。由于Br?nsted酸位易与酯化反应过程中生成的水发生水合反应而失活,因而Lewis酸位的形成有助于减少催化剂的失活现象发生。因此,当通过油酸与甲醇酯化反应合成生物柴油时,Ce-Ag-PW是一种具有高催化活性和稳定性的以Lewis酸性活性位为主的固体酸催化剂。      

Characteristic of synergistic extraction of oxalic acid with system from rare earth metallurgical wastewater

Large amount of high concentration acidic wastewater would be produced in the conversion process of chloride rare earth into oxide rare earth.It was a mixed solution of oxalic acid and hydrochloric acid,so the recycling use was very difficult.The method of liquid-liquid extraction was proposed in this paper to achieve wastewater treatment and reclamation.The mechanism of extraction of oxalic acid from the wastewater with the systems of 50% TOB+45% kerosene and 5% 2-ethyl hexanol was investigated.The composition and structure of the extracted species and the establishment of the mathematical model of the oxalic acid extraction were determined by the use of saturation method,equimolar series method.The results showed that extraction of oxalic acid by TOB was a neutral association extraction,oxalic acid existed mainly in a molecular form in the organic phase,and the extraction combination ratio was 2:1.The duality extraction system composed of extractant TOB and TOC had synergistic extraction effect on oxalic acid and chlorhydric acid,and the extraction dislribution ratio was improved greatly.The optimum volume fiaction of TOB was 0.6-0.8.     

Effect of doping rare earth oxide on performance of copper-manganese catalysts for water-gas shift reaction

Rare earth-doped copper-manganese mixed oxide catalysts were prepared by coprecipitation and mechanical mixing using copper sulfate, manganese sulfate, and rare-earth oxides REO （REO indicates La2O3, CeO2, Y2O3, or Pr6O11） as raw materials. The samples were characterized by X-ray diffraction （XRD）, temperature-programmed reduction （TPR）, temperature-programmed reduc-tion of oxidized surfaces （s-TPR）, and temperature-programmed desorption （TPD）. Catalytic activities were tested for a water-gas shift reaction. Doping rare earth oxides did not alter the crystal structure of the original copper-manganese mixed oxides but changed the interplanar spacing, adsorption performance and reaction performance. Doping with La2O3 enhanced the activity and stability of Cu-Mn mixed oxides because of high copper distribution and fine reduction. Doping with CeO2 and Y2O3 also decreased the reduc-tion temperatures of the samples to different degrees while improving the dispersion of Cu on the surface, thus, catalytic activity was better than that of undoped Cu-Mn sample. The Pr6O11-doped sample was difficult to reduce, the dispersion of surface coppers was lowered, resulting in poor activity.     

Kinetics of nitric acid leaching of cerium from oxidation roasted Baotou mixed rare earth concentrate

The kinetics of nitric acid leaching of cerium was investigated for the oxidation roasted Baotou mixed rare earth concentrate. The effects of leaching temperature, HNO₃ concentration, liquid–solid ratio (L/S) and stirring rate on rare earth extraction were studied. The XRD and SEM mapping analysis of the samples before and after acid leaching shows that the roasted bastnaesite is completely leached. Besides, the decomposition process of oxidizing roasting was also obtained by TG–MS and XRD. Different kinetics models were applied in this leaching process. The results of dynamic fitting show that the leaching process can be described by a new variant of the shrinking-core model. And the leaching rate is controlled by both the interfacial transfer and diffusion through the product layer. The apparent activation energy is calculated as 76.78 kJ/mol and the reaction orders with respect to HNO₃ concentrations and liquid–solid ratio are determined to be 7.609 and 2.516, respectively. Besides, an empirical rate equation is obtained to describe the process.     

钙沉淀-EDTA返滴定法测定稀土分离废液中草酸

采用过量加入钙标准溶液以沉淀稀土分离废液中草酸,过滤后,再以EDTA返滴定的方法测定了废液中草酸的含量。在样品溶液中加入400 g/L NaOH溶液调pH值至7.0～10.0,再加入10 mL NH₃-NH₄Cl缓冲溶液(pH 10.0),然后过量加入钙标准溶液沉淀废液中草酸,滤液再以NaOH溶液调pH值至12.0～12.5,铬蓝黑R为指示剂,用EDTA标准溶液返滴定过量钙。废液中大部分RE³⁺、Fe³⁺、Al³⁺等杂质离子在高pH值下可形成氢氧化物沉淀而得以分离,滤液中残余的Fe³⁺、Al³⁺用三乙醇胺等络合剂可消除其对铬蓝黑R指示剂的干扰。采用方法测定稀土分离废液合成样品中草酸的含量,结果与参考值一致。将方法应用于稀土分离废液实际样品中草酸的测定,测得结果相对标准偏差(RSD,n=6)为0.98%～1.9%,回收率为99%～101%。     

Double perovskite anti-supported rare earth oxide catalyst CeO_2/La_2CoFeO_6 for efficient ventilation air methane combustion

Ventilation air methane is one of available resources with a massive reserve.However,most of ventilation air methane is discharged into the air and pollutes the environment.Catalysts with high temperature resistance(>800℃)for ventilation air methane are very essential for utilization of the ventilation air methane.We mainly prepared catalysts CeO₂/La₂CoFeO₆and La₂CoFeO₆/CeO₂and comparative samples CeO₂and La₂CoFeO₆by the simple sol-gel method and calcined them under 9000C,and tested the catalytic performance of ventilation air methane combustion under the condition of 5 vol%H₂O.The experimental results show that the light-off temperature(T_1O)and complete combustion temperature(T₉₀)of the ventilation air methane combustion reaction of CeO₂/La₂CoFeO₆catalyst are 417.4 and 587.7℃,respectively.T_1Oand Tgo of La₂CoFeO₆/CeO₂only reach 425.5 and 615.8℃.The T₁₀and T_9Oof CeO₂/La₂CoFeO₆are 417.4 and 587.7℃,which are lower than those of La₂CoFeO₆[T₁₀=452.4℃and T₉₀=673.0℃)and La₂CoFeO₆/CeO₂(T₁₀=425.5℃and T₉₀=615.8℃).Therefore,the catalytic performance of the anti-supported rare earth oxide catalyst CeO₂/La₂CoFeO₆is better than that of La₂CoFeO₆and supported catalyst La₂CoFeO₆/CeO₂.     

离子型稀土矿不同采选工艺比较:基于成本的视角

离子型稀土矿采选先后经历了池浸、堆浸和原地浸矿3种工艺.目前,国家要求离子型稀土矿开发应采用原地浸矿等适合资源和环境保护要求的生产工艺,禁止采用池浸、堆浸工艺.基于离子型稀土矿床的特征、地质条件、各种工艺基本原理及优缺点,通过对不同工艺的会计成本比较和环境治理成本分析,认为从稀土矿采选会计成本的角度,3种工艺的成本相差不大;如果考虑环境治理成本,则对于地质条件复杂的矿山,采用原地浸矿工艺总成本可能最高.最后,提出了现阶段我国离子型稀土矿开采应因地制宜、有针对性地选择采选工艺及其他相关建议.      

分层取样方式对碳酸氢铵沉淀法生产碳酸稀土过程混合RECl3溶液理化指标检测结果的影响研究

稀土的提取与分离需要经过硫酸焙烧、水浸、萃取、反萃和碳沉等一系列过程,其中混合RECl₃溶液是稀土产业线中的重要中间产品,该混合稀土溶液的REO浓度、配分、密度等理化指标是评价混合RECl₃溶液产品质量的主要参数。针对一定存储条件下的混合RECl₃溶液,按照国家标准分析方法,结合X射线荧光光谱法(XRF)、电感耦合等离子体原子发射光谱法(ICP-AES)和重量法等手段,对该溶液中的REO浓度、配分、密度等项目进行检测,研究分层取样方式对3项理化指标的影响及变化规律。通过不同存放时间的变化因素绘制混合RECl₃溶液中REO浓度、密度的变化曲线,得出混合RECl₃溶液的存放时间越长,不同层面取样时这两个指标检测结果差异越大的结论;浅析了混合RECl₃溶液取样深度变化对检测结果的影响因素,对混合RECl₃溶液从表层到底层按照均匀间隔取样进行检测,得出REO浓度和密度的检测结果呈递增趋势,配分的检测结果呈轻稀土含量减少、重稀土含量增加的趋势等结论;研究了混合RECl₃溶液中REO浓度范围差异与存放一定时间内REO浓度的变化趋势,得出REO质量浓度小于50 g/L或大于250 g/L时,其检测结果变化缓慢,REO质量浓度在100～200 g/L时,其检测结果变化快速的结论。深入剖析了分层取样方式影响检测结果的基础理论,此研究可用于指导用于稀土应用产品的混合RECl₃溶液的质量控制,对规范混合RECl₃溶液的取样操作具有重要的指导意义。