共沉淀-喷雾干燥法制备钴酸镧催化剂

以共沉淀-喷雾干燥法制备钙钛矿型LaCoO3催化剂,并比较了喷雾干燥及普通烘箱干燥对催化剂的影响。对合成的催化剂粉体进行了BET-比表面积、XRD、SEM、TPR-H2表征。结果表明,喷雾干燥所制备的前驱体在600℃焙烧即可得到单一钙钛矿相结构的催化剂粉体,形成钙钛矿结构的焙烧温度降低50℃~100℃。喷雾干燥方法制得的催化剂对甲烷燃烧反应的催化活性明显高于用普通烘箱干燥方法制得的催化剂,起燃温度为T10=394℃。     

稀土氟化镧对多孔铝的性能影响研究北大核心

采用添加造孔剂的方法制备多孔铝试样。研究烧结温度和稀土氟化镧含量对多孔铝材料的性能影响。结果表明,烧结温度为600℃时多孔铝材料的烧结性能最佳;稀土氟化镧的适量加入可以提高多孔铝的力学性能;稀土氟化镧添加量为0.5%时,多孔铝材料的抗压强度和弹性模量最佳,分别为52.4 MPa和1.56 GPa。     

稀土镧在La-Mo合金粉中的存在形式及对钼粉性能的影响

通过对添加硝酸镧的二氧化钼在不同温度还原后钼粉的X射线衍射检测分析,研究了稀土镧在La-Mo合金粉中的存在形式;对La-Mo合金粉的粒度、氧含量、SEM照片等结果与纯钼粉对比分析,研究了稀土镧对La-Mo合金粉性能的影响。结果表明:随着还原的进行,稀土镧由以La2O3和钼酸镧的形式存在,逐渐转化为以唯一的La2O3形式存在;稀土镧强烈地抑制了钼粉颗粒的长大;由于稀土镧的加入,钼粉氧含量增加;La-Mo合金粉形貌为规则的多面体,分布不均匀。     

稀土掺杂对LaSrCoO4催化剂性能的影响

采用聚丙烯胺溶胶-凝胶法制备了类钙钛矿La0.7Nd0.3SrCoO4和La0.7Ce0.3SrCoO4复合氧化物催化剂,考察了它们对CO和C3H8的催化氧化活性,并运用XRD,IR,TPR和TPD等手段对催化剂进行了表征.结果表明,稀土掺杂后的LaSrCoO4复合氧化物均为K2NiF4型结构,不同稀土掺杂对LaSrCoO4复合氧化物的CO和C3H8氧化活性的影响不同,Nd掺杂能增加Co3+、化学吸附氧和晶格氧的数量,提高复合氧化物的活性.     

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。     

镧对黑曲霉生长代谢的影响

研究了单一稀土离子La3+对黑曲霉生长代谢的影响。结果表明:在培养基中添加适宜浓度的La3+后,固体平板上菌体生长速率提高,液体培养基中菌体生长量增大。当La3+浓度为40mg/L时,菌体生长速率、生长量及CMC酶活力均达到最大值,此后随离子浓度的增大而逐渐减小。滤纸酶活力则在La3+浓度为20mg/L时达到峰值,随后也随离子浓度的升高而逐渐降低。     

甲烷磺酸镧在酯化反应中的催化活性

合成了甲烷磺酸镧,用红外、热重分析对其进行表征。热重分析结果表明所合成的甲烷磺酸镧分子中含四个结晶水,La2O3含量的实测值与理论计算值基本相符。以甲烷磺酸镧为催化剂,研究了其催化氯乙酸与异丙醇酯化反应中各种因素对酯化率的影响。反应条件为:醇酸摩尔比1.2∶1,催化剂用量1.0%(以酸的摩尔数计量),反应时间2.5h,反应温度为回流温度,苯作为带水剂,最高酯化率可达95.5%。与其它Lewis酸催化剂比较,甲烷磺酸镧的催化活性最好。     

镧对碳纳米管负载型Ni-B非晶态合金乙炔加氢性能的影响

采用超声辅助的浸渍-还原法制备了N i-B/CNT s及L a改性的N i-B/CNT s非晶态合金催化剂,运用ICP、XPS、TPR、H2-TPD、CO化学吸附法对催化剂进行表征,并研究了催化剂的乙炔选择加氢性能。与N i-B/CNT s相比,添加适量L a提高了活性N i表面积,增强了N i的富电子性,促进了催化剂还原、氢脱附性能,并具有更好的加氢活性,L a的适宜添加量为5%~8%(质量分数)。     

镧对纯净钢夹杂物和耐腐蚀的影响

通过观察纯净钢中稀土夹杂物的形态，测试电化学腐蚀EIS谱和极化曲线，研究稀土元素镧对纯净钢耐腐蚀性能的影响。试验结果表明，镧加入纯净钢中，可变质夹杂物和改善夹杂物形态，从而提高了纯净钢耐腐蚀性能。     

甲基磺酸镧催化缩醛化反应性能的研究

以正辛醛和乙二醇为原料,甲基磺酸镧为催化剂,合成了正辛醛缩乙二醇。采用正交实验法考察了影响收率的因素。其最优条件为,正辛醛∶乙二醇∶催化剂∶带水剂为1m o l∶1.2m o l∶7.5g∶75mL,反应在回流温度下进行,反应时间3.0h,收率可达87.2%。用此方法合成了其它三种缩醛,同样获得满意结果。证明甲基磺酸镧对缩醛化反应具有较高的催化活性。     

Effect of Complex Agents on Structure and Activity of Fe-Substituted Rare Earth Hexaaluminate Catalysts for Methane Combustion

A series of catalysts were prepared by using complex sol-gel methods.Experimental results confirm the effect of different agents on structure and activity of Fe-substituted rare earth hexaaluminate catalyst (LaFeAl11 O19 ) for methane combustion.The catalyst is yielded by complex sol-gel, respectively using three different complex agents (maltose, glucose and citric acid).XRD demonstrated that haxaaluminate is the major phase of catalyst prepared by maltose,while LaAlO3 is the major one of the catalyst by glucose and citric acid.At the same time, there is a little LaFeO3 and surface areas as well as 29.5 nm particle diameter when the complex agent is maltose.However, T10 ( temperature for 10% conversion of methane) and T100 ( temperature for 100% conversion of methane) for catalyst by glucose is 543 and 758 ℃, which is the best among the three complex agents for methane combustion.     

制备Nb—Si细粉新方法

电弧熔炼之后,在电弧熔炼室内直接对铌含量（原子分数）为70％－85％的Nb-Si合金进行氢化,无需进行任何活化处理,就能够将Nb-Si合金粉碎成为细小粉末。     

WO_3负载的金属催化剂催化性能研究

通过共沉淀法制备了一系列WO3负载的金属催化剂,以甲醇低温裂解、苯加氢和甲苯加氢为探针反应,考察了其催化性能。实验发现对甲醇低温裂解反应,WO3负载的金属催化剂没有提高金属催化剂的催化活性,载体WO3对甲醇低温裂解反应没有促进作用;而对苯和甲苯加氢反应,WO3负载的金属催化剂的活性却大大提高,载体WO3对苯和甲苯发生加氢反应有明显的促进作用。这是由于吸附在不饱和W中心上的苯和甲苯,与金属活性中心活化的溢流氢发生反应,分别生成环己烷和甲基环己烷。     

Effect of ferrosilicon addition on the composition of inclusions in 16Cr-14Ni-Si stainless steel melts

The silicon deoxidation equilibrium between the 16Cr-14Ni-1.5Mn-Si melts and the CaO-SiO₂-8MgO-5CaF₂ (basicity=1.8) slag at 1743 K was investigated to understand the effect of aluminum and silicon contents on the composition of inclusions. Therefore, the ferrosilicon alloys with different aluminum content were chosen based on the preceding objective. In addition, the phase stability diagram of the inclusions was computed using commercial thermodynamic software based on the Gibbs energy minimization principles. The content of MnO in the inclusions sharply decreases with increasing silicon content when the steel melts were deoxidized by the ferrosilicon alloys containing high aluminum (FeSi-H). The content of SiO₂ in the inclusions slightly increases with increasing silicon content when the FeSi-L is used, while a maximum value is shown at [Si]=1.5 pct when the FeSi-H is used. The content of MgO in the inclusions increases by increasing the content of silicon, regardless of the kinds of ferrosilicon alloys. The use of the FeSi-L as a deoxidizer could suppress the formation of Al₂O₃ in the inclusions, while the content of Al₂O₃ increases with increasing silicon content when the FeSi-H is used. When the FeSi-H is used as a deoxidizer, the inclusions are the glassy type with the composition of Mn-silicates at [Si]≤1.3 pct, while the Mg(Ca)-silicates with the composition of the forsterite phase are observed in the steel composition of [Si]=3.3 pct. When the steel melts were deoxidized by the FeSi-L alloys, the inclusions are the glassy-type Mn-silicates at [Si]=0.8 pct, while the Mn-silicates containing the cristobalite phase are observed at [Si]=1.5 to 2.4 pct. In the composition of [Si]=3.3 pct, the Mg-silicates with the composition of the rhodonite phase are observed. The log(X _SiO2/X _MnO) of the inclusions linearly increases by increasing the log [a _Si · a _O / a _Mn] with the slope close to unity when the FeSi-L is used as a deoxidizer, while the slope of the line is about 2 times greater than that of the expected value when FeSi-H is used. The log (X _MgO/X _MnO) of the inclusions linearly increases by increasing the log [a _Mg/a _Mn] with slopes greater than the expected value of unity.     

Lanthanum Modified Ni/γ-Al2O3 Catalysts for Partial Oxidation of Methane

La modified Ni/γ-Al2O3 catalysts prepared by co-precipitation method using NaOH-Na2CO3 as a precipitator show high activity and selectivity for the partial oxidation of methane (POM). Meanwhile, the addition of La is beneficial for the formation of an active component and stability of support. We investigated some factors including calcining temperature, nickel content, and space velocity, which turned out to have a strong influence on catalytic activity and selectivity. By XRD and TPR, it is concluded that Ni0 reduced from amorphous NiAl2O4 is the major active component for POM.     

Cerium and Lanthanum Modified Pd/Al_2O_3 Catalysts for Methanol Decomposition

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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.     

Effect of Novel Supporter on Catalytic Combustion of Methane

A new catalyst support, Ce-Mg-O, was prepared in a novel way macromolecule surfactant modified method and was used as a catalyst support for low-temperature methane combustion. The results indicate that the new type of FeOx/Ce- Mg-O catalyst exhibits high activity in low-temperature methane combustion, such that the T90 at which 90% conversion of methane occurs can be obtained at 560 ℃. The structure of the catalyst and the effect of the supporter on catalytic activity were characterized by transmission electronic microscopy （TEM）, X-ray diffraction （XRD）, and temperature-programmed reduction （TPR）. The results indicate that the high catalytic activity of FeOx/Ce-Mg-O over methane combustion is strongly dependent on the particle size, typical crystal phase of the Ce-Mg-O, and the interaction of FeOx and Ce-Mg-O.     

Catalytic Performance for Oxidative Coupling of Methane over Eu_2O_3 Catalysts Promoted by Alkaline Earth Flourides

ＣａｔａｌｙｔｉｃＰｅｒｆｏｒｍａｎｃｅｆｏｒＯｘｉｄａｔｉｖｅＣｏｕｐｌｉｎｇｏｆＭｅｔｈａｎｅｏｖｅｒＥｕ２Ｏ３ＣａｔａｌｙｓｔｓＰｒｏｍｏｔｅｄｂｙＡｌｋａｌｉｎｅＥａｒｔｈＦｌｏｕｒｉｄｅｓＬｏｎｇＲｕｉｑｉａｎｇ（龙瑞强），ＷａｎＨｕｉｌ...     

镨在三效催化剂中的作用

本文采用溶胶 -凝胶法制备了负载在γ- Al2 O3上 ,含有 Ce- Zr、Pr- Zr、Ce- Pr- Zr固溶体的样品。进行了三效催化活性的评价 ,程序升温还原 ( TPR)表征和储氧量的测定。结果表明 ,样品均具有较高的三效催化活性 ,尤其是含有 Pr的样品 ,老化后在富氧区 ( S=1 .30 )的 NOx 转化率较高 ,达到 65%以上 ,其中由 Pr修饰的 Ce- Zr固溶体的样品的储氧量最大。