苯在等级孔Y型分子筛上吸附与扩散行为研究

以不同等级孔Y型分子筛为研究对象,运用XRD、N_2吸附、NH_3-TPD和Py-FTIR对其织构性质和酸性质进行表征。采用智能重量分析仪(IGA)等技术考察了苯在等级孔Y型分子筛上吸附扩散性能。结果表明,等级孔Y型分子筛在改性过程中晶型结构未发生明显变化,但改变了其孔道结构、酸类型、酸量及酸强度。苯分子在等级孔Y型分子筛上的传质性能主要与分子筛的孔道结构有关,等级孔Y型分子筛的孔容越大,扩散速率越快,更利于苯分子的扩散。而苯分子的饱和吸附量大小主要取决于等级孔Y型分子筛的酸中心类型及其强度。     

频率响应法研究噻吩在CeY分子筛上的吸附行为

以NaY、液相Ce离子交换改性的Y型分子筛(L-CeY)为研究对象,运用N2吸附、XRD、NH3-TPD和Py-FTIR等实验方法表征两种Y型分子筛的物化性能。采用频率响应技术(FR)和智能重量分析仪(IGA)研究噻吩在两种分子筛上的吸附行为,并考察噻吩在稀土离子改性Y型分子筛上的不同吸附作用模式。结果表明,频率响应技术能够有效识别分子筛孔道内发生的不同传质过程。噻吩在NaY分子筛上的吸附行为较为简单,存在孔道吸附和π电子相互作用两种吸附过程;而在L-CeY分子筛上吸附行为较为复杂,同时存在孔道吸附和"S-M"吸附等多种吸附过程,另外,在高温条件下,还存在复杂的催化反应过程。     

频率响应法研究苯在N a Y分子筛上的吸附和扩散行为

利用频率响应技术考察了苯在N a Y分子筛上的吸附、 扩散行为, 并与TG / DTG曲线和吡啶红外等技 术相结合来分析苯在分子筛上的吸附扩散机理。结果表明, N a Y分子筛中存在两种酸性中心, 即弱B酸中心和弱L 酸中心, 且以L酸中心为主; 在3 3 3、 4 2 3K时, 苯在N a Y分子筛上有两个吸附作用力, 分别是孔填充物理吸附和π电 子相互作用两种吸附形式。逐渐接近加氢催化裂化反应的温度( 5 7 3K) 时, 苯在 N a Y分子筛上的传质仍以吸附过程 为主。但是6 2 3K时, 在 N a Y分子筛上的传质以扩散过程为主, 吸附作用力弱, 易脱附, 更易于芳烃分子在其上的扩 散, 从而提高加氢裂化反应性能。     

噻吩和烃类在Cu（Ⅰ）Y分子筛上的吸附和扩散

通过液相离子交换法制备出Cu（Ⅰ）Y分子筛,并采用频率响应技术研究噻吩、苯、1-辛烯和正辛烷在Cu（Ⅰ）Y分子筛上的吸附和扩散。结果显示,噻吩和正辛烷在Cu（Ⅰ）Y分子筛上的传质过程的速控步骤为吸附过程,并存在两种不同的吸附过程,结合吸附等温线发现噻吩和Cu（Ⅰ）Y分子筛的作用力明显强于正辛烷的。苯在Cu（Ⅰ）Y分子筛上的传质过程的速控步骤为扩散过程,结合扩散系数,表明苯在Cu（Ⅰ）Y分子筛上的扩散为单一扩散过程。     

频率响应法研究噻吩在Hβ分子筛上的传质行为

用盐酸溶液改性Hβ分子筛,采用XRD、N_2吸附-脱附、NH_3-TPD等手段对Hβ分子筛晶体结构、织构性质和酸量等进行表征,以噻吩为探针分子,采用频率响应技术研究了盐酸改性Hβ分子筛对其吸附扩散性能的影响。结果表明,盐酸改性Hβ分子筛后,溶解了堵塞在Hβ分子筛孔道内的非骨架铝,增强了分子筛孔道的贯通性,提高了分子筛的传质性能。在频率响应谱图中,噻吩在改性的Hβ分子筛中传质过程的响应强度明显大于在未改性的分子筛中传质过程的响应强度,盐酸改性后Hβ分子筛的传质性能得到了改善,吸附噻吩脱硫的能力明显增强,这对催化噻吩反应、优化工业脱硫具有重要意义。     

频率响应法研究苯在Y型分子筛上的吸附扩散行为

以NaY和HY分子筛为研究对象,运用N2吸附表征两种Y型分子筛的物化性能;以苯为芳烃的模型化合物,采用频率响应技术(FR)和智能重量分析技术(IGA)相结合的方法,研究了苯在Y型分子筛上的吸附扩散行为。研究发现,苯与NaY分子筛骨架中Na+的相互作用大于苯与HY分子筛中B酸的相互作用,并且高温有利于苯在分子筛上的扩散。FR技术能够有效的识别客体分子在分子筛微孔孔道内发生的不同传质过程,并能识别出作用力的强弱,是研究微孔材料动力学的有效方法和手段。     

芳烃在F C C催化剂上的吸附扩散行为

利用智能重量分析仪( I GA) 和程序升温脱附技术( T P D) 研究芳烃( 苯、 对二甲苯及异丙苯) 在流化催 化裂化( F C C) 催化剂及稀土超稳 Y型分子筛上的吸附扩散行为。TG / DTG曲线表明, 芳烃在F C C催化剂及稀土超 稳Y型分子筛上只存在一种吸附模式, 推测这种吸附模式是芳烃与吸附剂之间通过π电子相互作用。另外, F C C催 化剂颗粒中, 整个传质过程中的速控步骤不是 Y型分子筛晶粒内微孔孔道中的扩散过程, 而是催化剂基质中长程的 大/介孔内的扩散过程及分子筛微孔与基质界面之间的分子交换过程。     

REY对噻吩和四氢噻吩催化转化行为的红外光谱研究

以NaY、HY、液相稀土Ce离子交换改性的Y分子筛(L-CeY)和稀土离子改性的超稳Y分子筛(HRSY-3)为研究对象,在氨气程序升温脱附(NH3-TPD)和吡啶吸附傅里叶变换红外光谱(Py-FTIR)表征其酸性能的基础上,采用原位傅里叶变换红外光谱(In situ FTIR)技术以噻吩和四氢噻吩作为探针分子,研究噻吩硫化物在稀土离子改性的Y型(REY)分子筛上的吸附及转化行为。结果表明,室温条件下噻吩在分子筛强B酸中心作用下即可发生质子化反应,质子化的噻吩分子可进一步发生低聚反应,且稀土物种和非骨架铝有关的L酸中心与B酸的协同作用促进质子化噻吩向低聚物的转化;而四氢噻吩在NaY、HY及REY型分子筛上均无催化反应发生。     

稀土离子半径对Y分子筛抗Ni性能的影响

采用液相离子交换法制备了CeY、NdY、HoY 分子筛,并通过Mitchell等体积浸渍法对其进行Ni污染。运用氨气程序升温脱附(NH3-TPD)和原位吡啶红外光谱技术(InsituPy-FTIR)对其酸性质进行表征,采用微反应活性评价装置考察其抗Ni性能。结果表明,随着稀土离子半径的减小,稀土改性Y 型分子筛抑制Ni破坏其B酸中心能力逐渐增强。进一步将酸性关联活性后发现,经Ni污染后REY 分子筛的催化裂化微反应活性亦随着稀土离子半径的减小而逐渐增强,且反应液相产物中汽油质量分数随Ni/REY分子筛催化剂中RE离子半径的减小而逐渐增加。RE离子半径越小的REY分子筛抗Ni性能越好。     

NiY/Beta复合分子筛吸附脱硫性能研究

采用液相离子交换法制备了NiY及NiY/Beta分子筛,利用智能重量分析仪测定了噻吩、苯在NiY、NiY/Beta分子筛上的吸附-脱附等温线,计算比较了噻吩、苯在分子筛上的扩散系数,同时使用固定床技术考查了改性后的分子筛对催化裂化汽油的吸附脱硫性能。结果表明,复合分子筛NiY/Beta仍然保持着较好的微孔结构,对噻吩的饱和吸附量大于苯的。而且噻吩在NiY/Beta分子筛上的相对扩散系数明显增大,而苯的扩散系数有所减少,这有利于噻吩在分子筛上的扩散过程,抑制了苯在分子筛上的吸附,从而提高了NiY/Beta复合分子筛对噻吩的选择性脱除能力。对于FCC汽油NiY/Beta复合分子筛也表现出更好的深度脱硫能力。     

Enhancing the leaching effect of an ion-absorbed rare earth ore by ameliorating the seepage effect with sodium dodecyl sulfate surfactant

Ameliorating the problem of low leaching efficiency, long leaching period, and high agent consumption should be studied to efficiently exploit ion-absorbed rare earth ore resources. In this study, the surfactant sodium dodecyl sulfate (SDS) is used to enhance the leaching effect of an ion-absorbed rare earth ore by ameliorating the seepage effect for the first time. The effects of surfactant concentration, leaching agent dosage, solution flow velocity, and solution pH on the leaching rate were explored, and the mechanism of SDS was discussed. Under the optimum conditions, the addition of a small amount of SDS (mass fraction 0.04%) can increase the leaching rate by about 5%, shorten the leaching period, and reduce the consumption of the leaching agent. SDS significantly ameliorates the seepage effect of the ore body by reducing the surface tension of the leaching agent and ameliorating the wettability of the mineral surface. This effect is the main factor that improves the leaching efficiency. DFT (density functional theory) calculation results show that SDS can react with rare earth ions, which reduces the adsorption strength on clay mineral surfaces. Hence, rare earth ions are easily exchanged by ammonium ions, and mass transfer is enhanced.     

Explaining surface interactions for common associated gangues of rare earth minerals in response to the oxalic acid

In the flotation of rare earth minerals(REMs), oxalic acid is reportedly acting both as a depressant and p H modifier. Although results of testing have established the significance of oxalic acid in the flotation process, its specific role in either the recovery or selectivity of REMs over their common gangue minerals is not well understood. Pulp p H reduction trials with alternative acids have not shown the same effect on the REMs recovery or the depression of gangue phases. This work studies the effect of oxalic acid on the surface of common REMs gangue minerals(quartz and carbonates(dolomite and calcite)) in a series of conditioning tests. Gangue surface analyses by time of flight secondary ion mass spectroscopy(TOFSIMS) indicate that oxalic acid inhibits the transfer of secondary ions generated during the conditioning process from one mineral to another. In this regard, the oxalate anion acts to fix ions in solution through chelation, limiting their participation in surface adsorption.     

Pulling growth technique towards rare earth single crystals

Pulling growth technique serves as a popular method to grow congruent melting single crystals with multiscale sizes ranging from micrometers to centimeters.In order to obtain high quality single crystals,the crystal constituents would be arranged at the lattice sites by precisely controlling the crystal growth process.Growing interface is the position where the phase transition of crystal constituents occurs during pulling growth process.The precise control of energy at the growing interface becomes a key technique in pulling growth.In this work,we review some recent advances of pulling technique towards rare earth single crystal growth.In Czochralski pulling growth,the optimized growth parameters were designed for rare earth ions doped Y_3Al_5O_(12)and Ce:(Lu_(1-x)Y_x)_2Si O_5on the basis of anisotropic chemical bonding and isotropic mass transfer calculations at the growing interface.The fast growth of high quality rare earth single crystals is realized by controlling crystallization thermodynamics and kinetics in different size zones.On the other hand,the micro pulling down technique can be used for high throughput screening novel rare earth optical crystals.The growth interface control is realized by improving the crucible bottom and temperature field,which favors the growth of rare earth crystal fibers.The rare earth laser crystal fiber can serve as another kind of laser gain medium between conventional bulk single crystal and glass fiber.The future work on pulling technique might focus on the mass production of rare earth single crystals with extreme size and with the size near that of devices.     

STUDY OF ADSORPTION OF RARE EARTH ELEMENTSBY FERRIC OXIDE GEL

Thereexistthreeformsofrareearthelements(REE)intheknownnaturalores:mineralcrystallineform,isomorphousreplacementformandexchangeableionicadsorptionform.Resently,however,anewkindofsecondaryoreofrareearthelementswidelydistributedintheoxidationzoneofthelargerbast--naesitedepositshasbeendiscoveredintheSouthwestofChinaandVietnam.Theneworelookslikeblackearthyefflorescence,andmainlyconsistsofamorphousFe--MnoxideandSt--Aloxide.Theformeraccountsfor74.14%(volumerate)andthelatter25.86%(volumerate).Ther…     

载银沸石/稀土/尼龙共混物的性能

以沸石为载体,AgNO3溶液为交换液,通过离子交换法将Ag离子交换进入沸石中,制成了载银沸石,并将其与稀土添加入尼龙(PA)中共混制备了载银沸石/稀土/PA复合材料。对复合材料进行力学性能和流变性能分析。结果表明,随着添加组分质量分数的增加,改性纤维的拉伸强度降低,当载银沸石和稀土质量分数达3%时,断裂强度明显大幅度下降。共混体系的流变曲线表现出明显的切力变稀行为,表明共混体系为假塑性流体。其表观黏度随剪切速率的增大而减小,随温度升高而降低,随着添加组分质量分数的增加而减小。共混体系的非牛顿指数随添加组分质量分数增加而降低,流变性能得到改善。     

负载型钯催化剂完全氧化性能的研究

研究了以含有稀土的Ｆｅ－Ｃｒ－Ａｌ合金为载体的铂催化剂的制备及其催化燃烧性能。实验表明：在苯蒸汽浓度为３２４０ｍｇ／ｍ３，空速为３００００／ｈ的催化燃烧实验条件下，经特殊工艺制得的最优催化剂，在９００℃高温下于空气中的烧后，完全燃烧温度为２４０℃，取得了令人满意的结果，同时，提出了催化剂制备的最优方案，并对其催化活性机理进行了初步探讨。     

Effects of rare earth elements on the microstructure and properties of magnesium alloy AZ91D

The effects of rare earth elements on the microstructure and properties of Magnesium alloy AZ91D alloy were studied.The different proportion of rare earth elements was added to the AZ91D and the tensile tests were carried out at different temperatures.The experimental results show that at room temperature or at 120℃ the AZ91D‘s decrease with the increasing amount of the rare earth elements.however,the ductility is improved.The influence of 0.14%Sb(mass fraction)on the AZ91D‘s strength is like that of rare earth elements(0.2%-0.4%)(mass fraction).Microstructure graphs demonstrate that appropriate amount of rare earth elements (0.1%-0.2%) can fine AZ91D‘s grain and improve its ductility.