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研究了CH_3NH_2-SiO_2-P_2O_5-Al_2O_3-H_2O体系的水热结晶行为,得到了在SiO_2:Al_2O_3:H_2O=0.4:1:40(摩尔比)时CH_3NH_2、P_2_5和Al_2O_3组成变化对分子筛结晶相影响的三元相图,发现了CFSAPO-1和CFSAPO-2两种分子筛。合成了一组含硅量不同的CFSAPO-1样品,利用XRD、IR、DTA、吸附和NH_3-TPD等方法进行了理化性能测定,发现进入骨架的Si等比地取代P和Al。 相似文献
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以TiCl4为原料,在低温下分别制备了纯二氧化钛和掺磷二氧化钛水溶胶,通过XRD、TEM、FT-IR、UV-vis等进行了表征。结果表明,两类样品中的TiO2颗粒均呈锐钛矿型晶相结构,粒径小于10nm,但是掺磷二氧化钛比纯二氧化钛的结晶度更高,颗粒分散更均匀,且禁带宽度和吸光度也有一定的增大,同时掺磷二氧化钛中的磷有效地溶入二氧化钛晶格中。通过对亚甲基兰的光催化降解表明,掺磷二氧化钛水溶胶的光催化性能比纯二氧化钛水溶胶大约提高了2倍。 相似文献
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以硫脲、五水硝酸铋为前驱体,采用溶剂热法制备出S掺杂BiOBr光催化剂。利用XRD,SEM,XPS,UV-Vis DRS、光电化学性能等对所制备的光催化材料进行了一系列表征。同时,在可见光照射下对S掺杂BiOBr进行光催化固氮性能研究。结果表明:S掺杂BiOBr的晶体结构未发生改变,比表面积增大。同时,形成的氧空位有利于吸附、活化N2分子和促进光生载流子的迁移,进而提高其光催化固氮性能。与BiOBr相比,S掺杂BiOBr的光催化产氨为25.36 mg?L-1?h-1?g-1cat,是BiOBr的4.6倍。最后,经4次循环实验,S掺杂BiOBr催化剂仍保持稳定的固氮效率。 相似文献
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采用浸渍法制备了过渡金属掺杂的光催化剂MOx/TiO2(M=Cr、Mn、Fe、Co、Ni、Cu).以乙酸的光催化氧化降解反应为探针,研究了催化剂的光催化性能.研究结果表明,经过渡金属掺杂改性的二氧化钛,光催化性能都有所提高.掺杂量有一个最佳值,在最佳掺杂量时,催化剂光催化性能的提高程度与对应金属氧化物的生成焓有很好的一致性,还发现光催化性能与过渡金属离子稳定氧化态的电子亲和势与离子半径的比值间呈现火山型关系曲线. 相似文献
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采用溶胶-凝胶法制备了不同铕(Eu)掺杂量的TiO2纳米颗粒(Eu-TiO2),利用透射电镜(TEM),X射线光电子能谱(XPS),X射线衍射(XRD)及紫外可见漫反射(UV-Vis DRS)等方法对Eu-TiO2进行了物理特性的初步表征.结果表明:与未掺杂纳米TiO2比较,Eu-TiO2禁带宽度变窄,具有可见光光催化活性.在可见光下(λ≥420 nm)照射下,以光催化降解染料罗丹明B(Rhodamine B,RhB)为目标反应,探讨了Eu-TiO2不同制备条件对RhB降解光催化活性的影响,优化得到制备高活性Eu-TiO2最佳pH为3、掺杂比例(nEu/nTi)为0.05%、煅烧温度为500 ℃.研究了可见光照射下Eu-TiO2降解RhB和无色有机小分子水杨酸(SA)光催化反应条件及降解特性,RhB的12 h深度氧化矿化率为60.2%,SA的8 h降解率达到100%.通过跟踪测定可见光下Eu-TiO2光催化反应过程中氧化物种的变化,研究了可见光激发Eu-TiO2光催化反应机理,表明其光催化反应主要涉及羟基自由基(·OH)历程. 相似文献
8.
掺杂Ti02的光催化性能研究进展 总被引:16,自引:0,他引:16
本文综述了掺杂TiO2在可见光范围的内应及其光催化性能的研究状况,讨论了掺杂金属离子的种类、浓度、光催化剂的粒径以及其它因素对TiO2光催化活性的影响。列出了掺杂TiO2的制备方法,并对今后的研究作了展望。 相似文献
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The physicochemical and catalytic properties of cobalt- and silicon-substituted AlPO-5 molecular sieves were studied by means of temperature-programmed reduction, temperature-programmed desorption of ammonia and the reaction of toluene disproportionation. 相似文献
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Large pore aluminophosphate-based molecular sieves like AlPO4-5, MAPO-5, MnAPO-5 and ZAPO-5 were synthesised hydrothermally using triethylamine as a structure directing agent. These materials
were characterised by X-ray diffraction (XRD),27A1 and31P MAS-NMR, ICP-MS,n-butylamine-TPD, BET and SEM. The catalytic performance of these materials was tested for isopropylation of benzene with 2-propanol
at 250, 300, 350 and 400°C. The products were cumene,p-DIPB (p-diisopropylbenzene) andm-DIPB (m-diisopropylbenzene). MnAPO-5 was found to be more active than the other catalysts. Maximum conversion (20%) was noted at
350°C over MnAPO-5. The selectivity to DIPB was found to decrease with time on stream but the selectivity to cumene showed
an increase after 3 h of time on stream 相似文献
14.
Yingcai Long Weihong Zhang Heyong He 《Journal of inclusion phenomena and macrocyclic chemistry》1987,5(3):363-372
The novel crystalline aluminophosphate CFAP-7, having a characteristic X-ray powder diffraction pattern, has been synthesized hydrothermally in a system consisting of di-n-butylamine-(NH4)2O–P2O5–Al2O3–H2O at 120 to 140°C, the P2O5 and Al2O3 sources of which were provided by (NH4)3PO4·3H2O and Al2(SO4)3 in aqueous solution, respectively. Investigations by DTA, TG, DTG, XRD, and IR indicate transformation of the original product (form A) into more stable crystal forms B and C on heating at about 180°C and 240°C, respectively, while liberating water and amine. Isotherms for the adsorption of water and methanol at 23°C show that both form B and form C are molecular sieves with a window dimension of 4.3–4.9 Å, and a methanol volume adsorbtion greater than that of water. 相似文献
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Nickel-incorporated hexagonal mesoporous aluminophosphate (NiHMA) molecular sieves were found to be highly efficient heterogeneous catalysts for the chemo- and regioselective reduction of nitroarenes and carbonyl compounds as well as the reductive cleavage of azo functions, including bulkier substrates, by the hydrogen transfer method. 相似文献
16.
Xu Wen-Yang Guo Chang-Jie Do Tao 《Journal of inclusion phenomena and macrocyclic chemistry》1986,4(4):325-331
A member of the novel family of crystalline microporous aluminophosphates, AlPO4-12, was synthesized by hydrothermal crystallization using different aluminum-containing compounds. Three new crystalline phases were obtained by varying the composition of the reaction mixture. The effect of the synthesis conditions on the hudrothermal process and the kinetics of crystallization are discussed. The apparent activation energies obtained for AlPO4-12 are 20.9 and 14.6 kcal/mol for nucleation and crystallization, respectively. The adsorption isotherms of one AlPO4-12 product were measured. 相似文献
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Experimental isotherms describing the adsorption of pure N2, CH4 and CO in AlPO4-11, AlPO4-17, and AlPO4-18 were determined using the volumetric method at 40°C and at 23°C (AlPO4-11 only) over a pressure range up to 123 kPa, and subsequently fitted with the Langmuir or Freundlich equations, as well
as the Flory-Huggins Vacancy Solution Theory equation. The capacities for the adsorbates investigated were found to depend
on the geometry of the sieve pore size, as well as the molecular dimensions and the polority of the adsorbate involved. At
40°C and over the investigated pressure range, AlPO4-11 and AlPO4-17 adsorbed pure CH4 in the highest amounts, while AlPO4-18 had a slightly higher capacity for pure CO.
The model parameters obtained by fitting the experimental pure-component isotherms permitted the prediction of binary adsorption
information for the CO−N2, CH4−CO, and CH4−N2 gas mixtures at 101.3 kPa total pressure, using the Extended Langmuir Model, the Ideal Adsorbed Solution Theory, and/or the
Flory-Huggins Vacancy Solution Theory for mixtures. An explanation of the behaviour predicted by each model for each adsorption
system is attempted. 相似文献
18.
原位合成负载型MSU系列分子筛 总被引:1,自引:1,他引:0
采用原位合成法,使用壬基酚聚氧乙烯醚(Tx-15)和脂肪醇聚氧乙烯醚(AEO-19)做为模板剂,在中性条件下合成W.MSU-1和W-MSU-2介孔分子筛,合成中使用乙酰丙酮(HAcac)作为助剂,考察其对介孔结构的影响,通过X射线衍射仪(XRD)、傅里叶红外光谱仪(FT-IR)、扫描电镜(SEM)、低温N2吸附对样品进行表征.结果表明,加入过渡金属氧化物有助于介孔的形成,助剂的使用提高了孔的结构参数. 相似文献
19.
Jacek Michalik Marek Danilczuk Janusz Turek Jaroslaw Sadlo 《Research on Chemical Intermediates》2007,33(8):793-806
This paper presents studies on paramagnetic intermediates, free atoms and radicals produced in γ-irradiated molecular sieves and their reactions with adsorbate molecules or exchangeable cations. Four different systems
have been investigated using EPR spectroscopy, Na-A/CH4, AgNa-A/CH3OH, Ag-SAPO-11/C2H4 and AgCs-rho/NH3. It was found that methyl radicals are formed in two different sites in Na-A/CH4 and in one of them they are stable at room temperature. The formation of Ag·CH2OH+ radical cation with one-electron bond between silver and carbon has been established in AgNa-A/CH3OH by EPR experiments with [13C]CH3OH and DFT calculations. In Ag-SAPO-11/C2H4 the stabilisation of biligand silver/ethylene complex, Ag0(C2H4)2 was postulated based on EPR and DFT results. Tetrameric silver clusters (Ag
4
3+
) produced radiolytically in AgCs-rho/NH3 strongly interact with two ammonia molecules as was deduced from the changes in superhyperfine structure of high-field EPR
line of Ag
4
3+
pentet for zeolite exposed to [14N]NH3 and [15N]NH3. The presented examples clearly show that the combination of radiation methods with EPR technique is very useful to study
the structure and reactivity of paramagnetic intermediates. 相似文献
20.
Cerium‐doped titanium dioxide (TiO2) with a hollow fiber structure was successfully prepared using ammonium ceric nitrate and tetrabutyltitanate as precursors and cotton fiber as the template. The effects of cerium (Ce)‐doping on the crystallite sizes, crystal pattern, and optical property of the prepared catalysts were investigated by means of techniques such as scanning electron microscopy (SEM), X‐ray diffraction (XRD), BET surface area, and UV‐vis diffuse absorption spectroscopy. SEM observation showed that the prepared TiO2 fibers possessed fibrous shape inherited from the cotton fiber and had a hollow structure. As confirmed by XRD and UV‐vis diffuse absorption spectroscopy examinations, Ce‐doping restrained the growth of grain size and extended the photoabsorption edge of TiO2 hollow fiber into the visible light region. The present photocatalyst showed higher photocatalytic reactivity in photodegradation of highly concentrated methylene blue (MB) solutions than pure TiO2 under UV and visible light, and the amount of Ce‐doped significantly affected the catalytic property. In the experiment condition, the photocatalytic activity of 0.5 mol% Ce‐doped TiO2 fiber was optimal of all the prepared samples. In addition, the possibility of cyclic usage of the photocatalyst was also confirmed. The material was easily removed by centrifugal separation. Therefore, using the template method and by doping with cerium, TiO2 may hopefully become a low‐energy consuming, high activity and green environmentally friendly catalytic material. 相似文献