粘土孔结构及添加铈对于催化剂上苯吸附-脱附-催化氧化性能的影响

采用3种不同孔结构的粘土材料,即Na型-蒙脱土(Na-mmt)、Al柱撑粘土(Al-PILC)和AlCe复合柱撑粘土(AlCe-PILC),以上述材料为载体,负载Mn和MnCe作为易挥发有机物(VOC)苯的氧化催化剂。利用N2吸附、程序升温还原(TPR)和程序升温表面反应(TPSR)等手段对催化剂的织构-结构、氧化-还原和吸附-脱附等性能进行了表征和分析。结果表明对于具有高比表面积和大孔径的改性粘土材料,添加适量的Ce有利于催化剂对低浓度苯的吸附,吸附量显著增加、脱附温度提高,上述条件都有利于对低浓度苯的深度氧化。同时,这一研究结果对改善"吸附-催化"一体化的低温吸附、高温脱附及氧化性能有极其重要的意义。     

Influence of Drying and Calcination on Remaining Amount and Immobile Character of Titanium on Titanium‐pillared Montmorillonite

Remove of titanium (Ti) from titanium‐pillared montmorillont (TIPM) is not expected during its application as adsorbent and photocatalyst, etc. But studies on immobilization of Ti on TIPM are seldom reported. In this work, TIPM was synthesized from TiCl₄ and Na⁺‐montmorillont (Na⁺‐MMT). Then the prepared TIPM was heated at different temperatures (100, 240 and 450°C) to yield three TIPM samples (TIPM1, TIPM2, and TIPM3). Inductively coupled plasma optical emission spectrometer (ICP‐OES) was used to determine the effect of heating temperature on the remaining amount of Ti on TIPMs. A two‐step treatment method which is often used in the pretreatment and application of TIPM was developed to investigate the immobile character of Ti on TIPMs. X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), N₂ adsorption/desorption isotherm, thermogravimetric analysis and differential scanning calorimetry (TG‐DSC) were also used to characterize TIPMs before and after the treatment. The results show that with an increase in heating temperature, the amount of Ti species remained on TIPM decreases gradually and Ti immobilization is strengthened on TIPM. For TIPM3, less than 2% Ti is removed from TIPM3 after the treatment required to simulate the practical conditions of TIPM in its application, while those of TIPM1 and TIPM2 are 6.6% and 8.4%, respectively. The reason may be that when TIPM is heated, Ti species intercalated into MMT become chemically bonded with the framework of MMT and partially migrate into the layer structure, which make Ti immobile on TIPM firmly during the treatment process.     

Fe-Al 柱撑膨润土的制备及其非均相Fenton降解橙黄II

通过离子交换方法制备不同Fe含量的Fe-Al柱撑膨润土,并且研究了其作为非均相Fenton催化剂降解橙黄II的性能.通过X射线粉末衍射(XRD),比表面积(SBET),傅里叶变换红外(FTIR)光谱,拉曼(Raman)光谱和扫描电子显微镜(SEM)研究其结构特征.结果显示,钠化膨润土的层间距为1.24 nm,经过柱撑之后,Al柱撑膨润土的层间距增大到1.77 nm,Fe-Al柱撑膨润土为1.72 nm左右,并且比表面积也有明显增大.XRD和Raman结果表明Fe/(Fe+Al)摩尔比达到20%时,样品中出现α-Fe2O3,膨润土未能形成柱撑.在橙黄II初始浓度为100 mg L-1,催化剂用量为1.0 g L-1,温度为40°C,pH为3.0,H2O2初始浓度为10 mmol L-1的条件下,考察了柱撑膨润土的Fenton催化活性.结果表明,Fe-Al柱撑膨润土的催化性能随着Fe含量的增多先增大后略有降低,当Fe/(Fe+Al)摩尔比为10%时达到最大,橙黄II溶液在4 h内色度去除率和化学需氧量(CODCr)去除率分别达到100%和87.73%,并且降解反应为非均相Fenton反应.研究了Fe-Al柱撑膨润土的重复使用性.催化剂循环使用4次,仍然具有良好的活性.     

Catalytic activity and acidity of Al pillared clays and zeolites in different hydrocarbon reactions

In comparison with zeolites, a variety of Al pillared clays did not prove as promising cracking catalysts, possibly because their Br?nsted sites are hidden. In the less demanding double bond shift isomerization, both catalyst types were comparable probably due to the presence of Lewis sites on both catalysts.     

Studies of layered and channel complexes using combined thermogravimetry and mass spectrometry

The rate of removal and uptake of guests into layered and porous materials is important in many areas of materials chemistry. Here we report on the use of atmospheric thermogravimetry linked to a mass spectrometer (TG-MS) to investigate the thermal characteristics of three different solids. We show that (i) the desorption of cyclohexylamine from the surface of a pillared acid activated smectite clay occurs in two stages, indicating two possible acidic binding sites, (ii) TG-MS is an extremely sensitive technique for probing progressive anion exchange of lithium aluminium layered double hydroxides, (iii) on heating, the perhydrate 4Na₂SO₄·NH₄Cl·2H₂O₂ releases H₂O₂ intact.We are very grateful to Miss J. Bovey for supplying us with the acid activated clay and for very helpful comments. We would like to thank Rheometric Scientific Ltd. and Leda Mass Ltd. for their advice and co-operation in designing and fitting the transfer line. Financial assistance from the EPSRC through a Quota award to ICC and a CASE award with Solvay Interox Ltd. to SDC is also appreciated.     

Three-pillared layer metal–organic frameworks assembled by imidazole-4,5-dicarboxylate and rigid bisimidazole ligands: synthesis,crystal structure,and sensing nitroaromatics

Three-pillared layer metal–organic frameworks based on 1H-imidazole-4,5-dicarboxylate and linear bis(imidazole) ligands generally formulated as {[Co₃(idc)₂(bib)₃]·8H₂O}_n (1), {[Cd(Hidc)(bib)_0.5]}_n (2) and {[Cd(Hidc)(bibp)]}_n (3), where H₃idc = 1H-imidazole-4,5-dicarboxylate, bib = 1,4-bis(1-imidazolyl)benzene and bibp = 4,4′-bis(1-imidazolyl)biphenyl, have been solvothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Compound 1 features a 3-D-pillared layer structure with 1-D channels, generated by honeycomb-like 2-D layer linked by bib ligands. Compound 2 consists of 2-D lumpy layers of [Cd₄(Hidc)₄], which are further connected by bridging ligands of bib to generate a pillared layer 3-D framework with 1-D channels. In 3, the 2-D corrugated honeycomb networks, structurally analogous to CFx, are pillared by bibp ligands to form a 3-D architecture with 1-D channels. Through selecting different metal ions and the length of pillared ligands, the pore sizes are adjusted in the three complexes. The potential of 2 and 3 for nitro explosive sensing is investigated through luminescence quenching experiments, which show that 3 can be applied as a fluorescent sensor for nitro compounds.     

规整Mn-Zn-Mg-Al-CO3四元LDHs层状材料的水热合成、结构及性能

以Mn(NO3)2.6H2O、Zn(NO3)2.6H2O、Mg(NO3)2.6H2O和Al(NO3)3.9H2O为原料,采用水热合成法,一步合成了Mn-Zn-Mg-Al-CO3四元LDHs层状材料。采用ICP、元素分析仪、XRD、FTIR、TG-DSC、SEM、低温氮吸附-脱附等对样品进行了表征。探讨了pH值、反应温度、反应时间和原料配比对Mn-Zn-Mg-Al-CO3四元LDHs层状材料合成的影响。结果表明,在pH=10、反应温度控制在140℃、反应时间为24 h的条件下,可以合成出结构规整、晶形良好、各层间排列紧密有序的含不同比例金属阳离子的Mn-Zn-Mg-Al-CO3四元LDHs层状材料。其吸附等温线符合V型吸附,H3滞后环,晶体内层间存在2 nm以上的孔,晶体内部结构的有序性高,层间碳酸根离子的排列整齐,通道内孔密度大、孔径小、比表面积大。     

Synthesis,structure and photoluminescence of a 3D pillared heterometallic coordination polymer containing 2D inorganic cadmium‐potassium‐oxide layer subunits

Self‐assembly of Cd(NO₃)₂ with o ‐phthalic acid monopotassium salt (KHphth) in the presence of ethylenediamine (en) produced a new heterometallic coordination polymer [CdK₂(phth)₂(en)_0.5(H₂O)]_n ( 1 ). Single‐crystal X‐ray analyses reveal that it crystallizes in a monoclinic space group P 2₁/c. a = 11.6707(6) Å, b = 8.1019(4) Å, c = 20.9503(11) Å, β = 94.6640(10)^o. The complex displays an en‐pillared 3D framework, which is constructed from 2D [CdK₂(phth)₂(H₂O)]_n layers featuring uncommon inorganic cadmium‐potassium‐oxide layers containing potassium‐oxide layers. In the solid state, complex 1 shows photoluminescence with the maximum emission intensities at 355 nm upon excitation at 312 nm. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

利用二次球形配位构筑亲水型隧道框架结构

质子化N,N,N’,N’-四苄基乙二胺可与[Fe(CN)6]3－, [SnCl6]2－和[TeCl6]2－二次球形配位分别形成可容纳客体分子的包结物晶体(1～3). 晶体1通过NH＋…NC－, NH＋…p(NC)和CH…p(NC)组合合成子, 构筑了亲水性层柱隧道结构, 孔径尺寸为1.03 nm×1.12 nm, 两个乙醇分子和两个水分子填充于隧道中; 晶体2通过CH…Cl－合成子, 构筑了亲水性层间隧道结构, 孔径尺寸为0.94 nm×0.73 nm, 三个水分子和两个氯离子填充于隧道中; 晶体3的结构与晶体2相似, 也是通过CH…Cl－合成子, 构筑了层间亲水性隧道结构, 孔径尺寸为0.94 nm×0.72 nm, 两个水分子填充于隧道中.