钙钛矿催化材料La1-xCexCoO3+δ的制备、表征及甲烷燃烧催化性质

采用柠檬酸发泡法制备了钙钛矿LaCoO3催化材料;研究了Ce对La进行掺杂替代对催化材料性能的影响;通过BET、XRD、SEM等手段对催化材料进行了物性表征;以甲烷完全燃烧为目标反应,研究了钙钛矿La1-xCexCoO3 δ的催化性能.结果表明:铈掺杂对材料晶相有较大影响,当掺杂量x小于0.3时,粉体晶型基本不变,而当掺杂量达到0.5时,有明显CO3O4晶相出现,LaCoO3钙钛矿晶相完整性遭到破坏,当掺杂量大于0.7时,钙钛矿晶相大大弱化甚至消失;LaCoO3是一种性能优良的甲烷燃烧催化材料,Ce的掺杂替代对催化材料活性有明显影响,并增强了催化材料的高温稳定性能,铈最佳掺杂量为0.3;前驱体经700℃焙烧形成了较为完整的钙钛矿晶型,经800℃焙烧后,催化材料最高活性为:t10%=390℃,t90%=603℃.     

稀土萃取分离过程三相乳化物的研究Ⅰ——无机杂质富集沉淀导致的乳化

对中钇富铕稀土矿萃取分离过程中产生的三相乳化物进行了物相分离和组成分析,确认第一分离段发生累积性三相物乳化的主要原因是原料中的难溶性固体物质累积,后续各分离段发生累积性三相物乳化的主要原因则是由于氟离子富集后生成了较多稀土氟化物沉淀。     

电感耦合等离子体原子发射光谱法测定磷矿中微量稀土元素

样品经碱熔,溶液提取,沉淀富集后得到只含稀土元素的溶液,采用电感耦合等离子体原子发射光谱(ICP-AES)法测定磷矿中15种稀土元素La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb、Lu、Y。主要考察了共存元素间的干扰情况,选择无干扰或干扰量对分析结果可以忽略不计的谱线为最佳分析线,标准曲线法直接测定磷矿中稀土元素。本法测定结果与ICP-MS测定结果相符合,可满足日常分析要求。     

Preparation and Physicochemical Characterization of La_(1-x)Ce_xCoO_(3 δ) Perovskite Catalyst and Its Methane Catalytic Combustion

Methanecatalyticcombustionhasattractedmanyconcernsinrecentyearsbecauseofitshighefficiency ,lowenergycost ,lownitrogenoxidesemissions ,andlongtimestableoperationinleanburncondi tions[1～ 6 ] .MethanewhichisrichinChinaisthemaincomponentofnaturalgas .Successfulresearchandde velopmentofadvancedmethanecombustioncatalyticmaterialsisveryhelpfultoaddresstoday′sseriousen vironmentandenergyproblems .Oxidationcatalystsforexhaustedemissioncontrolaremainlynoblemetalsbecauseoftheirhighcatalyticactivity .H…     

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.     

微波消解-电感耦合等离子体原子发射光谱法测定稀土合金渣中主要稀土氧化物

提出了微波消解-电感耦合等离子体原子发射光谱(ICP-AES)同时测定稀土合金渣中氧化镧、氧化铈、氧化镨、氧化钕、氧化钐和氧化镝等主要稀土氧化物的分析方法。考察4种不同的消解试剂体系,优化了消解参数并选择了合适的分析线。结果表明,在以下条件下样品的消解效果最好：以HNO₃-HCl-HF-H₂O₂（V(HNO₃)∶V(HCl)∶V(HF)∶V(H₂O₂)=4∶2∶2∶1）作为消解试剂,采用四段升温的消解程序,设定的最低温度为160 ℃,最低压力为1.5 MPa,最高温度为225 ℃,最高压力为3.5 MPa,每段的最大温差不超过25 ℃,最大压差不超过1 MPa。在选定的仪器参数下,以408.671,413.765,390.843,401.255,359.260,353.171 nm 波长的谱线分别作为La,Ce,Pr,Nd,Sm,Dy的分析线,用稀土氧化物绘制校准曲线,ICP-AES法测定消解液中上述氧化物。测定结果的相对标准偏差在0.44%～0.98% 范围,加标回收率在94%～106%之间。     

氢氧化镧湿法氟化法合成氟化镧工艺研究

采用了氢氟酸直接氟化氢氧化镧浆液的制备工艺，考察了工艺的可行性。研究了氢氟酸浓度、用量、反应温度、反应时间等因素对产物含氧量、氟化率和制备过程中过滤、洗涤的影响。通过差热分析、扫描电镜、X射线衍射等手段对产品的组成、形貌、结构等进行了研究。制备工艺为固液反应，工艺简单，产品分散性好，易过滤洗涤，质量稳定，工业可操作性强，流程短。     

Preparation and Physicochemical Characterization of La1-xCexCoO3+δ Perovskite Catalyst and Its Methane Catalytic Combustion

Perovskite oxide LaCoO3 methane catalytic material was synthesized with citric acid complexation and bubbling method.The effect of doped cerium was studied on the series of La1-xCexCoO3 δ materials by means of BET,XRD and SEM techniques.Their catalytic behaviors were studied with methane catalytic complete combustion as probe reaction.The results show that doped cerium has great effect on crystal phase formation.When doped cerium is less than 0.3 (molar ratio),the crystal phase of oxide has little changed.When doped cerium is up to 0.5,Co3O4 phase is obviously discovered and the perfectibility of LaCoO3 perovskite crystal phase is deteriorated.When x is over 0.7,perovskite crystal phase is weakened or completely disappeared.Considering the crystal phase of oxides,the optimum doped cerium is about 0.3.The perovskite oxides can be formed at a low calcinations temperature of 700 ℃.When x is 0.3,the highest catalytic activity of T10% (390 ℃) and T90% (603 ℃) is obtained on the series of La1-xCexCoO3 δ materials calcined at 800 ℃.     

电感耦合等离子体原子发射光谱法测定镝铁电解粉尘中15种稀土元素

用硝酸和氢氟酸溶解试样,高氯酸冒烟除氟,在硝酸介质中用电感耦合等离子体原子发射光谱法(ICP-AES)测定了镝铁电解粉尘中La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb、Lu、Y 15种稀土元素。为了提高高含量元素的测定准确度,在测定基体元素Dy时,采用铟作内标;为了消除基体效应对稀土杂质元素测定的影响,采用基体匹配的校准曲线。镝铁电解粉尘中铁含量很低(铁的质量分数不超过1%),对测定没有影响。实验方法测定了一镝铁电解粉尘样品,结果表明,La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Ho、Er、Tm、Yb、Lu和Y 14个稀土杂质元素测定值与ICP-MS的测定值基本一致,镝和14个稀土元素的合量与重量法测得的稀土总量吻合。