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1.
我们通过自下而上(bottom-up)的方法制备了高宽深比、高结晶度的b轴方向上超薄的MFI沸石纳米片,为制备b轴取向MFI沸石薄膜提供了基础。采用滑动涂覆法(slip coating method)在玻璃片载体上制备了厚度约为100 nm的b轴取向MFI纳米片晶种层。采用无模板剂二次生长法,抑制晶种层面外孪晶生长,实现了晶种层的面内外延生长。在合成体系的nSiO2nNa2OnC2 H5 OHnH2 O=1:0.03:1.3:0.89、晶化时间48 h、晶化温度180℃时,制备了厚度约为200 nm的连续致密的b轴取向MFI沸石膜,与基于四丙基氢氧化铵(TPAOH)的常规合成溶液水热二次生长制备的MFI沸石膜相比,厚度降低了90%,并且保持了晶种层的b轴取向性。  相似文献   

2.
采用二次生长法,在不锈钢、α-Al2O3和莫来石多孔管状支撑体上分别合成了高渗透汽化性能的T型分子筛膜。考察了合成条件如合成时间、n(SiO2)/n(Al2O3)、n(H2O)/n(Al2O3)和硅源等对T型分子筛膜形成和分离性能的影响。通过XRD和SEM表征了膜的晶相和形貌。  相似文献   

3.
使用旋涂法在多孔α-Al2O3载体上获得了b-&h0h-取向的silicalite-1晶种层。在无模板剂存在条件下进行二次生长,通过改变合成液的碱度(OH-/Si)、水量(H2O/Si)和晶化温度等,调节膜表面的形貌和晶体取向。SEM和XRD检测结果表明,对于1SiO2:4EtOH∶xNaOH∶yH2O合成体系,x与y值的选取与分子筛膜的形貌和晶体取向紧密相关。当x=0.56时,增加y值将促进分子筛膜从随机取向到b-轴取向的转变,晶粒形貌也发生了较大变化;当y=270时,可以得到厚约为4 μm、连续且择优b-轴取向的MFI型分子筛膜。  相似文献   

4.
研究了微波场中T型分子筛的结晶过程。考察了微波加热体系中合成参数如合成时间、溶胶组成、反应压力和模板剂用量对分子筛晶化的影响。微波加热的主要优点是减少合成时间,无模板剂的溶胶在普通加热条件下的晶化时间需要120 h,而在微波场中则仅需要20~25 h。另一方面,由于微波的快速加热特性促进了稳定相钙十字沸石的生成,从而减小了次稳定相T型分子筛的结晶区间。在未添加模板剂条件时,100 ℃下微波水热合成T型分子筛的结晶区间为:20≤nSiO2/nAl2O3≤22和0.31≤ nM2O/nSiO2≤0.33(其中M2O=Na2O+K2O, nNa/nK=3和nM2O/nSiO2=11.70)。在普通加热和微波加热合成体系中,添加模板剂均能扩大结晶区间,同时还可以进一步减少合成时间。  相似文献   

5.
以硅铝干凝胶为硅源和铝源,氢氧化钠为碱源,采用类固相法快速合成了P型分子筛,并通过X射线衍射(XRD)、扫描电镜(SEM)等手段对产品进行了表征分析。结果表明,硅铝干凝胶的组成nSiO2/nAl2O3=5,晶化时间和晶化温度分别为3 h、140℃,原料的组成nNa2O/nSiO2nH2O/nSiO2=18.51时,可制备形貌均一、结晶良好的P型分子筛产品。与传统水热法相比,该方法极大地减少了合成过程的用水量,缩短了晶化时间,提高了产品的钙镁离子交换性能,从整体上优化了P型分子筛的合成工艺。  相似文献   

6.
以二丙胺异构体(二正丙胺DPA和二异丙胺D-iPA)为结构导向剂,在200℃加热2组反应原料物质的量之比不同的初始凝胶,合成出了高结晶度的磷酸铝分子筛AlPO4-11。利用X射线粉末衍射分析、元素分析等表征手段,研究了凝胶的晶化过程和液相的pH值以及Al和P的浓度演化。初始凝胶各组分物质的量之比为nAl2O3nP2O5nDPA/D-iPAnH2O2=1.0:1.0:1.2:75时,以DPA为结构导向剂,晶化过程中无中间相生成,而以D-iPA为结构导向剂时,晶化过程中生成了具有12元环孔道结构的磷酸铝分子筛AlPO4-5中间相;初始凝胶各组分物质的量之比为nAl2O3nP2O5nDPA/D-iPAnH2O2=1.0:1.0:1.0:75时,以DPA为结构导向剂,晶化过程中生成了具有18元环孔道结构的磷酸铝分子筛VPI-5中间相,而以D-iPA为结构导向剂时,晶化过程中同时出现了VPI-5及AlPO4-5两种中间相。表明对于同一种有机胺,凝胶物质的量之比的改变影响了其结构导向效应。理论计算结果显示质子化的DPA及D-iPA中N原子上的电荷有差异,表明有机胺的结构微调影响其结构导向效应,但该影响依赖于凝胶组成。  相似文献   

7.
利用水热合成法,以三乙烯四胺(TETA)为模板剂,正硅酸乙酯、磷酸、氢氧化铝及乙酸钴为原料,合成了CoSAPO-34分子筛。通过扫描电子显微镜(SEM)、粉末X射线衍射(XRD)、热重(TG)、N2吸附-脱附和紫外-可见漫反射光谱(UV-Vis DRS)等方法对合成的分子筛进行表征。以吡啶-正辛烷体系为模拟油品对分子筛催化剂的脱氮效果进行评价,考察了样品的用量、光催化时间及循环催化次数对其脱氮性能的影响。结果表明:当合成原料的物质的量之比为nP2O5nAL2O3nSiO2nConTETA=1:0.26:0.82:0.81:2.05,在200 ℃晶化24 h,合成得到粒径约为50 μm、仍保持了SAPO-34分子筛的骨架结构、形貌为立方体的CoSAPO-34分子筛,而且该分子筛具有较好的热稳定性。在500 W氙灯光照条件下反应150 min,样品对质量分数为100 μg·g-1模拟油品的脱除率达到70%,循环3次光催化脱氮活性基本保持不变。  相似文献   

8.
在不同硅铝比(nSiO2/nAl2O3)的合成凝胶(含纯硅凝胶)中引入晶种,合成了纯相的EU-1分子筛。研究了铝源、模板剂和晶种添加量对EU-1分子筛的结晶度、形貌尺寸等的影响;重点研究了不同硅铝比对样品结晶度、晶粒尺寸、酸性、比表面积和孔容等的影响。将合成结果绘制成了纯相EU-1分子筛的合成条件三元图,从三元图可看出,晶种法可显著扩大纯相EU-1分子筛的合成区域。将Pt/H-EU-1用于正己烷异构化反应,结果表明,该催化剂具有优异的正己烷异构化活性及稳定性,对异构烷烃有较高的选择性。  相似文献   

9.
以廉价水玻璃为硅源,在晶种替代有机模板剂的条件下采用干胶法合成了ZSM-5分子筛。利用XRD、SEM、TEM、FTIR、N2吸附-脱附和NH3-TPD等分析方法对合成样品进行了表征和测试,考察了合成条件对ZSM-5分子筛晶化过程的影响。结果表明,在硅铝比(n/n)为30~70,钠硅比(n/n)为0.12~0.20时都可以得到结晶度良好的ZSM-5分子筛。研究发现,干胶法合成ZSM-5,在不引入外加水的情况下也可以得到ZSM-5样品,外加水的引入能够有效地提高晶化速率;与水热法合成ZSM-5分子筛相比,干胶法可以显著地缩短晶化时间,同时,合成样品的晶体尺寸也有所减小。  相似文献   

10.
十二烷基三甲氧基硅烷(DMS)和硬脂酸(STA)对α-Al2O3载体上二次生长合成的silicalite-1膜进行修饰来提高其表面疏水性。红外光谱和接触角测试结果表明,改性后改性剂以化学键的形式结合于分子筛膜表面,膜表面由亲水变为疏水。表面改性的最佳预处理温度为150℃,改性剂的最佳质量分数为10%。进一步研究了膜表面润湿特性和热稳定性之间的关系,其中DMS改性后的分子筛膜在空气中经250℃高温处理后仍保持疏水性不变。在乙醇/水分离应用中,高温脱除模板剂后缺陷的孔径分布在1~5nm时,表面改性后乙醇分离因子较改性前可提高5倍,最高可达21.6。  相似文献   

11.
Physico-chemical properties of Chitosan films   总被引:1,自引:0,他引:1  
Chitosan films obtained by dry phase inversion were prepared from an aqueous solution of chitosan in acetic acid. The films, of thickness less than 20 μm, were transparent, very flexible and had smooth surfaces. Increasing the film thickness induced an increase of the internal tensions and the consequent formation of a rough surface. Structural investigations by X-ray diffraction and Fourier transform IR analysis, showed that the chitosan films, as prepared, are amorphous. Further annealing to evaporate acetic acid and water traces, changed the amorphous phase into a more ordered phase, characterized by diffraction peaks at 2θ values of 9, 17, 20 and 23 degrees. Thermal investigations by TG, DTG, and DTA revealed that the decomposition of the chitosan films as prepared proceeds in two stages, starting from 180°C and 540°C.  相似文献   

12.
Kinetics of oxidation of xylitol and galactitol by hexacyanoferrate(III) ion in aqueous alkaline medium is reported. The reaction rate is of first order with respect to hexacyanoferrate(III) in each substrate. The reaction is first order at lower concentrations of xylitol and galactitol and tends towards zero order as the concentration increases. Similarly first order kinetics was obtained with respect to hydroxide ion at lower concentrations and tends to lower order at higher concentration in the oxidation of xylitol; in the oxidation of galactitol the reaction is first order with respect to hydroxide ion even up to manyfold variation. The course of reaction has been considered to proceed through the formation of an activated complex between [K Fe(CN)6]2– and substrate anion which decomposes slowly into radical and [K Fe(CN)6]3–. A probable reaction mechanism is proposed.
Kinetik und Mechanismus der Oxidation von Xylit und Galaktit mit Hexacyanoferrat(III) in wäßriger, alkalischer Lösung
Zusammenfassung Das Geschwindigkeitsgesetz der Titelreaktion ist in beiden Fällen erster Ordnung bezüglich Hexacyanoferrat(III). Die Oxidation ist erster Ordnung bei niedrigen Konzentrationen von Xylit und Galaktit und geht bei Erhöhung der Konzentration gegen null. In gleicher Weise wurde eine Kinetik erster Ordnung bezüglich Hydroxyl bei niedrigen Konzentrationen und eine erniedrigte Ordnung bei höheren Konzentrationen für die Oxidation von Xylit beobachtet; bei Galaktit bleibt die Oxidation auch bei höheren Hydroxyl-Konzentrationen erster Ordnung. Es wird angenommen, daß die Reaktion über einen aktivierten Komplex zwischen [KFe(CN)6]2– und dem Substrat-Anion verläuft; dieser Komplex zerfällt in [KFe(CN)6]3– und ein Substrat-Radikal. Ein möglicher Reaktionsmechanismus wird vorgeschlagen.
  相似文献   

13.
In the ternary system silver chloride-lithium chloride-sodium chloride the kinetics of the galvanic deposition of silver on graphite electrodes was investigated as well as its dissolution without current in the molten salt saturated with chlorine gas.In addition the emf-values were measured in the temperature range between 923 K and 1,173 K by means of, the formation cell graphite/Ag(s)/AgCl(l)–LiCl(l)–NaCl(l)/Cl2 graphite From these data the partial molar free excessGibbs energies were calculated. Using the equation for a multicomponent system as suggested byRedlich-Kister 1 G AgCl E values were obtained by a non-linear fitting process, where the fit was performed for all investigated temperatures and over the entire concentration range in the ternary system. With the parameters obtained the partial and integral excess valuesG i E ,G E ,H i E ,H E ,S i E andS E were calculated.
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14.
A plasma induced degradation process has been studied to treat 4-nitrotoluene (4-NT) present as an aqueous pollutant. The plasma was locally generated from a glow discharge around a tip of a platinum anode in an electrolytic solution. The influence of initial pH and Fe2+ on the degradation was examined. Major intermediates resulting from the degradation process were identified. Amongst the aromatic intermediates, p-hydroxybenzoic acid was the predominant degradation product. The formation of oxalic acid, malic acid was also observed. The final products of degradation were NH 4 + , NO 3 and CO2. Based on the analysis of intermediates and the kinetic considerations, the degradation was shown to follow a pseudo-first order reaction hence, a possible reaction pathway was proposed.  相似文献   

15.
Equimolar mixtures of 3,5-dimethylpyrazole (1) with four NH-imidazoles (2–5) have been studied by13C and 15N CPMAS NMR and by DSC. In three cases, the solid mixture behaves as the sum of the individual components [imidazole (2), 2-methylimidazole (3) and 2,4(5)-dimethylimidazole (5)]. In one case [4,5-dimethylimidazole (4)], the mixture corresponds to a new species in which the dynamic behavior of1 no longer exists.  相似文献   

16.
Thiomorpholine as well as alkyl substituted thiomorpholines and their Sdioxides, respectively, are transformed into the corresponding N-Aminothiomorpholines by nitrosation (1–5) followed by the reduction with zinc in acetic acid/acetic acid anhydride under simultaneous formation of the corresponding N-acetyl derivates, and hydrolysis by hydrochloric acid (6–9). Examples of this method are described. 4-Aminothiomorpholines and their Sdioxides react with aldehydes or ketones to give azomethines (10–31). Acylation with mono-and dicarbonic acid chlorides leads to the N-acyl derivatives32–44.Mannich condensation is also possible. By oxidation with yellow mercury oxide tetracenes are formed (46–47).
Teil der DissertationM. Schmitz, Techn. Hochschule Aachen, 1975.  相似文献   

17.
An attempt was made to study the oxidation of manganese by air in synthetic waters. A series of batch experments were performed at differnet values of concentration, temperature and pH. Unoxidized manganese in the solution was determined by formaldoxime spectrometric method. Results of these studies indicated that the air oxidation of manganese soluble in water can be effectively performed in basic media and that oxidation yield increasedwith an increase in pH and concentration. The yield was very high in the presence of manganese dioxide, sepiolite or clinoptilolite in solution and, the oxidation was almost completed especially at high values of pH and concentration. The reaction was found to be first order with respect to Mn2+ with a very low activation energy. A yield of 62% was obtained for the air oxidation of wastewater taken from the treatment plant of Corum Municipality.  相似文献   

18.
Solid state reaction of CuO and Al2O3 with a flux of PbO about 930°C and reaction time of 8d gives the new compound Cu2Al4O7. The red single crystals were examined by energydispersive microanalysis and X-ray diffraction methods. Cu2Al4O7 has cubic symmetry, space group ,a=908.0 pm. The typical coordination of Cu+ (CN=6 and CN=12) and the interstitial arrangement of the AlO4-tetrahedra are discussed with respect to related compounds.
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19.
CoNb2O6 can be prepared by reaction of stoichiometric amounts of CoO (thermical decomposition of cobaltoxalate) and Nb2O5 in argon-atmosphere up to 1,400 °C. The isolated red-brown single crystals have tetragonal symmetry (a=472.6;c=305.4 pm; space group P42/mnm-D 4h 14 ). Electron probe micro-analysis of the single crystals verifies the composition Co0.33Nb0.67O2. Co2+ and Nb5+ occupy statistically the metal positions of the rutil-type structure. The differences between Co0.5Nb0.5O2 (CoNbO4AlNbO4-type) and Co0.38Nb0.67O2 (CoNb2O6) are discussed.
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20.
Ten novel and stable free radicals of nitronyl-, imino-nitroxide and hydrazyl type compounds were synthesized and their physico-chemical properties investigated. UV-Vis and ESR spectroscopic data, as well as the lipophilicities and specific hydrophobic areas of the compounds are compiled. The reaction of these radical compounds with nitric oxide and nitrogen dioxide was also investigated. The radicals synthesized, show selectivity in their reaction with these nitric oxides, depending on their structure (nitronyl-nitroxide radicals react with NO, while hydrazyl radicals react with NO2). The processes are easily monitored by UV-Vis or ESR spectroscopy.  相似文献   

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