多相催化剂的微波制备技术进展

对近年来微波技术在负载型金属催化剂、金属氧化物催化剂、负载型金属氯化物催化剂和离子改性分子筛制备中的应用进行了介绍,比较了微波加热和传统加热的实验结果。指出微波加热可以提高离子交换分子筛的交换度,可以使活性组分在载体表面实现快速均匀分散,并且促进金属氯化物与载体发生固态离子交换反应,从而提高催化剂的稳定性和反应活性。     

改性介微孔ZSM-5分子筛催化剂制备及催化甲苯甲醇烷基化反应性能

将微孔ZSM-5分子筛通过不同浓度的氢氧化钠溶液处理不同的时间制备不同的介微孔ZSM-5分子筛,然后负载五氧化二磷制备介微孔ZSM-5分子筛催化剂,对介微孔ZSM-5分子筛负载五氧化二磷催化剂进行甲苯甲醇烷基化反应评价。其中氢氧化钠溶液浓度为1.0 mol/L、处理时间为30 min得到的介微孔ZSM-5分子筛负载五氧化二磷催化剂催化甲苯甲醇烷基化反应的活性较高。对介微孔ZSM-5分子筛负载五氧化二磷催化剂进一步采用铂进行改性,将制备的催化剂用于甲苯甲醇烷基化反应,在460 ℃条件下连续反应505 h,甲苯转化率保持在10.9%,二甲苯中对二甲苯的选择性保持在96%以上。研究结果表明,五氧化二磷、铂改性的介微孔ZSM-5分子筛催化剂具有优异的甲苯甲醇烷基化反应性能。     

微波辅助制备纳米ZnO及其光催化降解染料的性能

以硝酸锌、氢氧化钠为原料,聚乙二醇400(PEG 400)为溶剂,采用微波加热共沉淀法制备纳米ZnO,并采用X射线衍射、场发射电镜及紫外-可见漫反射对样品进行表征;考察纳米ZnO对结晶紫(CV)及刚果红(CR)的光催化降解性能,以λ=365nm的紫外光为光源,考察了催化剂投加量、染液浓度、pH值以及催化时间对催化效率的影响。实验结果表明,在较少的投加量下,纳米ZnO对50mg/L的CV和CR染液的降解率可分别达到98.8%和97.4%,pH值对两种染料的光催化效果影响不大。CR及CV染液的光催化降解均符合一级动 力学。     

微孔-介孔分子筛负载氧化钴的苯催化完全氧化性能

用水热合成法合成了微孔-介孔分子筛MSZ,采用等体积浸渍法制备了Co_3O_4/微孔-介孔分子筛催化剂。用X射线衍射技术对材料进行表征,考察微孔-介孔分子筛的水热稳定性和催化剂对苯的催化完全氧化性能。研究发现,微孔-介孔分子筛水热稳定性较好,负载质量分数为35%Co_3O_4时,催化剂活性较高,活性组分晶粒的完整性和分散度是影响催化剂活性的重要因素,35%Co_3O_4/MSZ的活性高于35%Co_3O_4/MCM-41和35%Co_3O_4/ZSM-5。     

微波辐射在催化剂制备中的应用

微波作为一种独特的加热方式应用于催化剂制备中表现出明显的优越性.综述了微波在分子筛合成、活性组分在载体上的负载、载体的改性及新型材料的合成(包括纳米材料和介孔材料)等方面的研究应用.展望了微波辐射在催化剂制备中的应用前景.     

改性纳米氧化锌光催化降解水体甲醛的研究

以均匀沉淀结合微波法制备了Sn、Ag、Al(Sn、Ag、Al与Zn的摩尔比分别为:1∶9,1∶40,1∶20)共掺杂的ZnO型光催化剂,用其降解水体中的甲醛。结果表明,当甲醛溶液浓度为10 mg/L,降解2.5 h,掺Ag的ZnO催化剂对甲醛降解率可达85%以上,掺Sn的ZnO可达80%左右;当甲醛初始浓度为10 mg/L,催化剂用量为1.0 g,光催化时间为2.5 h时,掺Sn的ZnO催化剂对甲醛的降解率达到最大值,为87%左右。     

Mn(Salen)/NaY的制备及其在β-蒎烯环氧化反应中的应用

用微波固相法制备了Mn(Salen)/NaY催化剂, 并对其催化β-蒎烯环氧化反应的性能进行了考察。FT-IR结果表明,微波固相方法和常规方法均能成功地将Mn(Salen)络合物包合于微孔分子筛NaY。与常规法制备的催化剂相比,微波固相法制备的Mn(Salen)/NaY催化剂对β-蒎烯环氧化具有很高的转化率和选择性,并且重复使用后催化活性变化不大。     

煤矸石微波辅助合成沸石分子筛的研究

为探究煤矸石合成沸石分子筛的最优工艺,以煤矸石为主要原料,采用传统水浴加热与微波辅助加热的方法,合成4A型沸石分子筛与P型沸石分子筛,利用电子显微镜和X射线衍射,对其形貌和结构进行分析表征。实验通过制备相同的沸石分子筛,得出制备沸石分子筛的煤矸石需要高岭石含量较高、有害杂质含量较低及较为合适的粒径(3μm～50μm)。相较于传统水浴加热,微波辅助加热得到的沸石分子筛纯度低,但加热时间仅需30 min～40 min,而传统水浴加热合成需要24 h,同时微波辅助加热还提高了沸石分子筛反应速率和分散度。     

微波辅助双模板剂体系快速合成纳米SSZ-13分子筛及NH3-SCR脱硝性能研究

采用硅溶胶为硅源、偏铝酸钠为铝源、四甲基氢氧化铵(TMAOH)和N,N,N-三甲基金刚烷氢氧化铵(TMAdaOH)为混合模板剂，通过微波加热方式在8 h内快速合成结晶度良好的纳米SSZ-13分子筛。结合XRD和SEM理化性质表征，考察了微波辅助晶化时间、晶化温度、初始凝胶中TMAdaOH用量、硅源和铝源类型等因素对合成SSZ-13分子筛的影响，进一步通过离子交换的方式负载铜离子制备Cu-SSZ-13催化剂。结果表明，在中低温(175～350℃)区域NO_x转化率达99%,NH₃-SCR脱硝性能满足中低温脱硝催化剂的要求。     

微波加热法向分子筛中引入稀土离子

微波加热法制备Ｌａ－ＮａＸ沸石分子筛催化剂;考察微波加热条件下,交换液浓度,交换时间、微波加热功率等因素对离子交换的影响;利用正交实验,寻找交换反应的最佳工艺条件,用对比实验与传统方法进行比较。     

Cu/SSZ-13催化剂脱硝活性中心与催化性能构效关系的研究

NH₃选择性催化还原NO_x（NH₃-SCR）是目前最有应用前景的柴油车尾气净化技术,该技术的核心是开发具备优异催化性能的催化剂。以具有菱沸石（chabazite,CHA）结构的小孔分子筛SSZ-13为载体制备的Cu/SSZ-13催化剂,因具有优异的催化性能和水热稳定性能而受到广泛关注。制备了系列Cu_x/SSZ-13催化剂,并通过CO原位漫反射红外光谱（DRIFT）和H₂-TPR等方法能够确定具有高催化活性的铜离子在SSZ-13分子筛上的落位和存在状态。CO红外吸附实验发现,采用Cu(NO₃)₂水溶液离子交换法制备的Cu/SSZ-13催化剂上存在多种落位的Cu⁺活性中心。在较低的Cu⁺交换度条件下,Cu⁺优先落位于SSZ-13分子筛的八元环位置,随着交换度的提高,Cu⁺开始落位于SSZ-13分子筛双六元环的位置。H₂-TPR结果表明Cu_x/SSZ-13催化剂上也存在大量落位在八元环位置不稳定的Cu²⁺,这些Cu²⁺很容易被还原为Cu⁺。Cu_x/SSZ-13催化剂经800℃水蒸气连续老化16 h,分子筛骨架崩塌程度随着Cu含量的增加而提高,骨架铝的脱除,导致Cu物种发生团聚,而第二金属Ce元素的引入能够在一定程度上提高Cu/SSZ-13的水热稳定性。催化剂构效关系研究表明,具有一定量稳定存在的Cu⁺,并且拥有大量不稳定存在Cu²⁺的催化剂具有较宽温度范围的脱硝性能。     

AgCo13X改性分子筛的制备与吸附脱硫性能

采用液相离子交换法制备了以金属离子Co2+和Ag+共同改性的AgCo13X分子筛吸附剂,并用XRD、NH3-TPD、BET和TG等技术对其结构进行表征。在模拟柴油中考察了吸附剂对二苯并噻吩(DBT)的脱硫性能。结果表明:AgCo13X分子筛的脱硫性能优于单一离子改性的Co13X和Ag13X分子筛;而Co13X和Ag13X分子筛的脱硫性能又明显高于未改性的13X分子筛。当Ag+离子交换浓度为0.1 mol/L时制备的Co2+和Ag+共同改性的AgCo13X分子筛具有最好的脱硫性能,其脱硫率为99.91%。剂油比为0.02 g/mL,当吸附时间为1 h即可达到吸附平衡;吸附剂具有良好的稳定性和再生性,再生后的脱硫率达到98.21%。     

国产天然斜发沸石的物性及离子交换性能研究

通过化学组成分析、扫描电镜、X射线衍射、差热热重和比表面积分析对来自国内6省15个沸石矿点的沸石样品进行了表征,并分别测定了沸石的全交换容量及其对纯钾溶液和海水中K+的交换容量.结果表明,大多数矿点的沸石样品主要含斜发沸石,5号样品主要由丝光沸石组成,11、13号沸石样品属于斜发沸石和丝光沸石的混合物;6号和7号样品比表面积分别为42.48 m2/g和40.56 m2/g,其他都在10～30m2/g之间;沸石样品可稳定加热至500℃,温度过高,会导致内部结构破坏;1、2、3、6、7、9、15号沸石的全交换容量及其对纯钾液和海水中K+交换容量较高,分别在110～165 mg/g和55～67 mg/g以及15～22 mg/g,属于品质较高的斜发沸石,具有较高的工业利用价值.     

Growth and morphology of ZnO nanorods prepared from Zn(NO3)2/NaOH solutions

ZnO nanorods on ZnO-coated seed surfaces were fabricated by a solution chemical method using supersaturated Zn(NO₃)₂/NaOH solution. The seed surfaces were coated on glass substrates by sol–gel processing and PEG addition. The mechanism of crystal growth and the factors affecting the rod growth were elucidated. The morphology and structure of both the seed surface and successive nanorods were analyzed by using SEM, XRD, TEM and SAED. Nucleation on the ZnO seed surface is crucial for rod growth since rods can only be observed on ZnO-coated substrates. Supersaturation is also required for rod growth and the Zn²⁺ ion and NaOH concentrations must be varied synchronously to maintain the high level of supersaturation. The average diameter and length of the ZnO nanorods increase to different degree with increasing precursor concentration. The dependence of rod growth on temperature shows that the maximum rod growth rate at any given concentration of Zn²⁺ occurs at a specific temperature, and the optimal temperature increases with Zn²⁺ ion concentration. Densely thick nanorods oriented perpendicularly to the substrate can be obtained by controlling the seed surface with PEG assistance.     

Study on deactivation of Cu–Zn–Al catalysts in the synthesis of N-ethylethylenediamine

The performance of a Cu–Zn–Al catalyst employed in the synthesis of N-ethylethylenediamine from ethylenediamine and ethanol was studied. The results showed that the activity of the Cu–Zn–Al catalyst decreased with time-on-stream. Fresh and deactivated catalysts were characterized by XRD, XPS, N₂ adsorption–desorption and TEM. It was found that the crystallite size of Cu and ZnO in the deactivated catalyst were much bigger than those for the fresh catalyst. In addition, channels in the deactivated catalyst were blocked by carbonaceous deposits, so the surface area and pore volumes of the deactivated catalyst were much smaller than in the fresh catalyst. Therefore, it was concluded that the deactivation of the Cu–Zn–Al catalyst was mainly caused by the growth in the Cu and ZnO crystallite sizes and carbonaceous deposits.     

Degradation of CI Reactive Red 141 by heterogeneous Fenton‐like process over iron‐containing ZSM‐5 zeolites

The Fenton‐like oxidation of CI Reactive Red 141 was investigated over iron‐containing ZSM‐5 zeolites. Iron was loaded by ion exchange or through hydrothermal synthesis. The oxidation process was carried out in an aqueous solution using hydrogen peroxide as the oxidant. The catalyst prepared by ion exchange with a silicon/aluminium ratio of 42 zeolite showed the highest activity (97% decolorisation and 52% chemical oxygen demand reduction at an initial pH of 3.5) after an oxidation duration of 2 h. The chemical oxygen demand reduction increased with the increasing amount of iron loaded to the zeolite. The FeZSM‐5 catalyst, prepared by hydrothermal synthesis in the presence of oxalic acid, showed very good activity in terms of mineralisation (99% of chemical oxygen demand reduction). The iron leaching was noticeably low (below the European Union directives of 2 mg dm^?3) for the above‐mentioned catalysts.     

High porous carbon with Cu/ZnO nanoparticles made by the pyrolysis of carbon material as a catalyst for steam reforming of methanol and dimethyl ether

Cu/ZnO/carbon catalysts for steam reforming reactions were prepared by the technique to obtain much amount of metals highly dispersed on the porous carbon. The preparation method includes the carbonization of an ion exchange resin loaded with metal cations. By containing ZnO in the resin, the agglomeration of Cu particle during the carbonization was suppressed within the carbon matrix due to the difference in the behavior of carbonization and migration between Cu and Zn in the same ion exchange resin, and the Cu particle size was reduced. Thus, the obtained Cu3Zn1 catalyst had more than double the Cu surface area of the catalyst contained only Cu, regardless of lower Cu content. Methanol steam reforming test showed that the catalysts’ activity was positively correlated with Cu surface area. Also in dimethyl ether (DME) steam reforming reactions using the composite catalysts with γ-Al₂O₃, the catalytic activity tracked with the surface area covered by Cu. The optimized Cu/ZnO/carbon catalyst composite showed a high DME conversion of 0.87 even at the low temperature of 300 °C and with GHSV = 2000 h⁻¹, which was due to high dispersion of Cu on the micropore structure of carbon support.     

原料配比对水热体系合成A/X复合沸石的影响

无模板剂条件下,采用水热体系合成出A/X复合沸石。用XRD粉末衍射法研究了原料配比(硅铝比、水钠比及钠硅比,均为摩尔比)对合成A/X复合沸石的影响,表明A/X复合沸石在较窄范围内生成。TEM照片显示合成样品晶粒均匀,粒度约为200 nm。A/X复合沸石的钙离子交换值达到与4A沸石同水平,镁离子交换值远远高于4A沸石,且随X型沸石质量分数的升高而增大。     

Catalytic combustion of hexane over transition metal modified zeolites NaX and CaA

Hexane deep oxidation was studied over NaX and CaA zeolites modified by ion exchange with transition metals (Mn²⁺, Co²⁺, Fe³⁺), the percentage of ion exchanged, determined by ICP-MS, varying between 39 and 98%. Parent and exchanged zeolites were characterized by X-ray diffraction (XRD), N₂ physisorption, temperature-programmed reduction (TPR), oxygen and ammonia temperature-programmed desorption (TPD) and inverse gas chromatography (IGC). Catalytic activities were evaluated through the recording of light-off curves in a pulsed microreactor, catalytic activity being correlated with physicochemical properties of the solids (crystallinity, surface acidity, adsorption properties and morphological parameters). As general trend, CaA zeolites are more active than NaX zeolites. Mn-exchanged CaA zeolite was the most active catalyst for hexane oxidation, whereas the addition of Fe to the zeolites leads to strong chemical and morphological changes in the parent zeolite.     

改性HZSM-5分子筛催化乙醇胺合成哌嗪

利用离子交换法对HZSM-5分子筛进行改性,得到了KCl-ZSM-5,NiO-ZSM-5,ZnO-ZSM-5,KCl-NiO-ZSM-5和KCl-ZnO-ZSM-5分子筛催化剂,采用X射线衍射(XRD)和扫描电镜(SEM)对催化剂进行表征,并考察了改性HZSM-5分子筛对乙醇胺(MEA)合成哌嗪(PIP)的催化性能。结果表明:HZSM-5分子筛经KCl,NiO和ZnO改性后出现了相应的特征衍射峰,且其表面较改性前出现许多小晶粒;改性后催化剂的活性有所降低,但哌嗪的选择性明显提高。KCl-NiO-ZSM-5催化性能较好,在常压,温度360℃,NH3和MEA物质的量之比为0.7的条件下,原料MEA的转化率和PIP的选择性分别是66.34%和28.66%。