晶格氧部分氧化甲烷制合成气及其氧扩散行为研究

介绍了一种在熔融盐中利用金属氧化物的晶格氧部分氧化甲烷制合成气的新方法。以NiO为氧载体对其部分氧化甲烷的氧扩散行为进行了初步研究。利用XRD和GC等分析手段,在自行设计的氧扩散行为研究反应器中对熔融盐体系和产物气进行了分析研究。结果表明,在800℃的碳酸熔融盐中,CH4通过不含NiO氧载体的熔融盐层时H2、CO浓度仅为13.67%和20%,而通过含NiO氧载体的熔融盐层时H2、CO浓度明显增至45.9%和24.5%;实验表明NiO能够提供出自身晶格氧把CH4部分氧化成n(H2)/n(CO)接近理论值2的合成气;NiO在熔融碳酸盐体系中虽有少量溶解,但主要不以离子化形式扩散氧,而是CH4与NiO分子间发生气固反应占主导,在这一过程中NiO分子中晶格氧是甲烷部分氧化的活性氧物种。     

CeO2中晶格氧直接部分氧化甲烷制取合成气的研究

介绍了一种合成气制取的新方法-熔融盐中用晶格氧直接部分氧化甲烷制取合成气技术,对该技术的概念进行了阐述.以CeO2为氧载体,对反应过程进行了热力学分析,结果表明以CeO2中晶格氧直接部分氧化甲烷制合成气是可行的.在固定床石英反应器中对非熔融盐体系下的氧载体进行了性能评价,并用XRD技术进行了氧载体的表征.在750～900 ℃温度范围内,分别对(0.462×104)/h,(0.924×104)/h,(1.386×104)/h三种空速进行了实验,同时对产物气中n(H2)/n(CO)进行了考察,结果表明,(0.924×104)/h的空速和900 ℃的温度比较适于合成气的制取,失去晶格氧的CeO2-x有着很好的氧再生能力.     

甲烷部分氧化的热力学模拟研究

甲烷部分氧化制备合成气对于提高天然气的利用价值具有重要的意义。甲烷部分氧化反应是一个非常复杂的反应体系。反应涉及部分氧化（主反应）、燃烧、重整、水煤气变换、积炭等。使用Aspen Plus和HSC Chemistry软件对甲烷部分氧化制备合成气过程进行热力学模拟计算。考察了温度、压力和CH4/O2比对CH4转化率、氢和CO选择性的影响。同时对甲烷部分氧化反应热力学平衡产物组成和积炭副反应进行了热力学计算分析。研究结果表明,随反应温度的升高,压力的减小,CH4的转化率和CO与H2的选择性均呈上升趋势。反应温度在300℃时就有相当多的积炭生成,在550℃积炭量达到最大,随后又随温度上升,积炭量逐渐减少,在900℃以上无积炭产生。     

甲烷部分氧化催化剂上的积碳研究进展

积碳是影响甲烷转化制合成气的催化剂性能的重要因素.在阐述甲烷催化部分氧化过程反应机理和催化剂体系的基础上,重点论述了甲烷催化部分氧化的催化剂失活与积碳的关系及影响催化剂的积碳因素.认为提高催化剂抗积碳性能的关键在于活性组分和负载量的改变、助剂的添加、载体的调控和制备方法的改进和储氧材料的使用,并对晶格氧催化甲烷部分氧化制合成气技术提出了展望,认为该技术具有良好的工业化应用前景.     

担载型含稀土三组份体系在二氧化碳甲烷化反应中的催化性能

用浸渍法制备了一系列氧化锆担载的含稀土Ⅷ族金属催化剂，对其在二氧化碳甲烷化过程中的催化活性作了研究，并用漫反射紫外可见光谱，ＦＴＩＲ等手段对催化剂作了表征。结果表明，含稀土新型催化剂具有催化活性高，目标产物选择性好等优点；稀土主要以氧化物形式存在于催化剂表面，参与对氢及表面含碳物种的吸附及活化；含稀土三组份催化剂的活性与所添加稀土三价离子的４ｆ电子数有关。     

添加稀土氧化物对甲烷化催化剂中镍分散度的影响

本文对稀土氧化物的助剂作用做了进一步研究，对添加１４种稀土氧化物的催化剂进行了活性表面积、ＣＯ吸附ＩＲ谱、表观活化能的测定及ＡＥＳ表面微区分析。结果表明，添加稀土氧化物助剂，提高了镍的分散度，使镍更富集于表面，增加了反应的活性中心数目，反应活化能没有降低，具有结构效应，但不同稀土元素的作用不同。这可能与稀土元素本身的性质有关。     

稀土改性Ni/γ-Al_2O_3催化剂上甲烷化反应积碳的初步研究

本文系统考察了镧系１４种稀土氧化物对镍基甲烷化催化剂积碳的影响，发现大多数稀土的添加使催化剂活性提高，寿命延长，尤以Ｄｙ，Ｐｒ，Ｓｍ效果最佳，主要作用是稀土添加剂促进了甲烷化活性中心数的增长，有抑止积碳的能力，缩短催化剂的增活期。     

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.     

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.     

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.     

从废稀土荧光粉回收稀土

稀土荧光粉广泛应用于发光材料行业,并且用量每年都在不断增长,同时产生的废旧稀土荧光粉也越来越多.因此,从中回收稀土不仅有利于保护环境,而且有利于资源的充分利用.物理方法难以从废旧稀土荧光粉中分离得到高纯度单一稀土,化学方法则可以获得单一高纯稀土.而它的瓶颈在于浸出和分离的高效性及经济性.本文对废稀土荧光粉回收稀土技术的现状进行了分析,认为已具有从废旧稀土荧光粉中提取单一、高纯稀土的成套新技术.     

Global rare earth resources and scenarios of future rare earth industry

It is known to all that China is abundant in rare earth resources.But rare earth deposits are really not that rare in the earth crust.In the five continents,i.e.Asia,Europe,Australia,North and South America,and Africa,there are about thirty four countries found to have rare earth deposits;Brazil might surpass China and rank the first in rare earth deposits.At present,investment in rare earth production was surged,there have been about 200 projects,and the total production for 25 of them would be more than 170 thousand tons after 2015,a multi-supply system on rare earths is being established worldwide.Cautions on the investment of rare earth production are involved.     

含稀土高岭土精矿回收离子相稀土工艺研究

高岭土精矿具有粒度细、黏度大、渗透性能差、固液分离难、含铝高等特点,南方高岭土常伴有稀土,怎样从精矿中提取合格的稀土,目前国内外还没有一套成熟的工艺技术应用于工业生产上。依据高岭土矿中的稀土赋存特点,通过实验室小试、扩试和工业试验,探索出了一套成熟的工艺技术流程,把浸矿液与高岭土精矿加入到捣浆池中进行搅拌浸取,将矿浆通过板框压滤机压滤,得到的滤饼即是提取稀土后的高岭土精矿,滤液经后续处理即得到稀土产品。同时建成了生产线,已生产稀土10余t,为回收高岭土精矿中的离子型稀土提供了有效工艺。     

碱熔预处理对废旧稀土荧光粉中稀土提取的影响

针对废旧稀土荧光粉特性,采用高温碱熔与酸浸相结合的方法处理废旧稀土荧光粉,考察碱熔温度、氢氧化钠用量、碱熔时间对稀土浸出率和铝回收率的影响,并对碱熔过程中的物相及形貌变化进行分析.结果表明,在碱熔温度为1050℃、氢氧化钠与废粉质量比为2.5∶1、碱熔时间为2 h 条件下,其稀土浸出率可达98%以上,铝回收率可达98%.通过对碱熔产物物相和形貌分析表明,废粉晶体结构被有效破坏,其中稀土以稀土氧化物形式存在,碱熔产物变成无定型云絮状.     

Effect of different mixing ways in palladium/ceria-zirconia/alumina preparation on partial oxidation of methane

The effect of the mixing ways of Ce0.7Zr0.3O2-Al2O3 mixed oxides on the partial oxidations of methane （POM） was investigated over Pd/Ce0.7Zr0.3O2-Al2O3 catalysts, the mixing ways including salt precursor mixing （ATOM）, precipitator mixing （MOL）, and powder mechanically mixing （MECH）, respectively. The test results indicated that among the three samples, Pd/ATOM had the best catalytic activity while Pd/MOL had the best stability in the stability test. Both the activity sequences of the fresh and used samples were consistent with the order of Pd dispersion. According to the X-ray diffraction （XRD） and BET characterization, the interaction of Ce^4＋, Zr^4＋, and Al^3＋ in the ATOM mixed oxide was in favor of performing higher catalytic activity and thermal stability. The stability test indicated that Pd/MOL had the highest Pd dispersion and least coke formation on the active sites calculated by the Hz-chemisorption and TG results, which was considered to relate to its superior activity of POM to other catalysts.