β沸石骨架稳定性与表面酸性的红外光谱研究

用红外光谱法研究了真空热脱附和空气中焙烧两种不同的方法脱除模板剂对Hβ沸石骨架结构稳定性和表面酸性的影响.结果表明,在真空条件下加热脱除模板剂,其骨架结构保持完好且质子酸中心最多.而在空气中焙烧脱除模板剂,导致沸石骨架部分脱铝,形成大量的Lewis酸且耐酸性极差.     

抑制β沸石骨架脱铝的焙烧研究

研究了因焙烧过程升温速率对β沸石模板剂的热分解过程的影响,不同升温速率下Naβ沸石焙烧的尾气组成;还测定了Naβ沸石的TG-DTG谱,400℃下Naβ沸石的FIIR谱图,以及在不同温度下焙烧4 h后的XRD谱图及29Si、27Al的NMR结果.根据这些结果,提出了分段焙烧脱胺方法,使有机胺在260～420℃间的两个恒温段充分发生Hofmann降解反应,从而使分解产生的乙烯和水蒸气能够随空气流自然排出焙烧体系,可使焙烧过程中产生的热能得到分阶段逐步地释放,同时可避免高温下沸石骨架水热脱铝的负作用,得到骨架脱铝少、结晶度高的脱胺β沸石.     

模板剂四乙基氢氧化铵的用量对合成的β沸石结构及脱胺的影响

研究四乙基氢氧化铵（TEA-OH）模板剂用量对合成的β沸石的结构及脱胺行为的影响。合成β沸石的模板剂的较佳用量(TEA+/Al)为2.10～1.68,合成的β沸石的相对结晶度均大于84%;β沸石中的铝含量(Al/Al+Si)及骨架铝含量(TdAl/TdAl+OhAl)随晶化混合液的TEA+/Al而变,存在最佳TEA+/Al点为1.9,此时合成的β沸石非骨架铝量最少,结构硅铝比最高;含TEA的β沸石脱胺过程为Hofmann降解反应,TGA测定的失重量、DSC测定的吸热量与β沸石中TEA含量密切相关.     

完美骨架全硅β沸石性质研究Ⅰ.合成全硅β沸石与脱铝β沸石的性质比较

以四乙基氢氧化铵为模板剂,正硅酸乙酯为硅源,静置水热法合成全硅β沸石.用硝酸(13 mol/L)对硅铝比(Si/Al)为20的Na-β沸石回流脱铝.焙烧后的上述两样品经粉末X射线衍射、低温氮吸附、核磁共振、红外光谱、吸附等温线等表征,发现合成的全硅β沸石骨架与孔道结构完美并具有很高的表面疏水/亲有机物的吸附特性.     

完善骨架全硅β沸石性质研究

以四乙基氢氧化铵为模板剂,正硅酸乙酯为硅源,静置水热法合成全硅β沸石 。用硝酸(13 mol/L)对硅铝比(Si/Al)为20的Na-β沸石回流脱铝。焙烧后的上述两 样品经粉末X射线衍射、低温氮吸附、核磁共振、红外光谱、吸附等温线等表征, 发现合成的全硅β沸石骨架与孔道结构完善并具有很高的表面疏水／亲有机物的吸 附特性。     

完善骨架全硅β沸石性质研究

以四乙基氢氧化铵为模板剂，正硅酸乙酯为硅源，静置水热法合成全硅β沸石 。用硝酸(13 mol/L)对硅铝比(Si/Al)为20的Na-β沸石回流脱铝。焙烧后的上述两 样品经粉末X射线衍射、低温氮吸附、核磁共振、红外光谱、吸附等温线等表征， 发现合成的全硅β沸石骨架与孔道结构完善并具有很高的表面疏水／亲有机物的吸 附特性。     

带压水热处理对HZSM-5沸石结构和性质的影响

利用ＸＲＤ，＾２７ＡｌＭＡＳＮＭＲ，ＮＨ３－ＴＰＤ吡啶吸附ＩＲ等技术考察了带压水热处理温度对直接法ＨＺＳＭ－５沸石骨架铝的迁脱和表面酸性质的影响规律，实验发现，随着水处理温度的升高，沸石骨架铝的迁脱量增加，在带压水热处理条件（４００－６００℃）下，直接法ＨＺＳＭ－５的骨架结构稳定，其架铝不能迁脱，对ＨＺＳＭ－５（３８），于５００℃，和水蒸气压力为１．０ＭＰａ条件下热处理１２ｈ后，只能使３０．０％的     

CXN天然沸石的研究VII. 骨架高硅超稳化改性

以高硅超稳化辉沸石(STI)为基底沸石,分别经盐酸脱铝或氟硅酸铵脱铝补硅处理后制备的改性H-STI沸石,其非骨架铝含量明显减少,而后者骨架硅铝比进一步提高.X射线荧光散射光谱(XRF),27Al高分辨率魔角旋转固体核磁共振(MASNMR),红外(FT-IR)光谱等表征证明改性后的沸石骨架硅铝原子比分别为6.8和11.4.低温氮吸附表明,经盐酸处理的高硅STI沸石孔道开放完美,但经氟硅酸铵处理的样品孔道被部分堵塞.分段程序升温焙烧表明前者骨架热稳定性略差,1000℃焙烧后结构基本被破坏,而后者热稳定性较好,经相同温度段焙烧后仍保持较高的结晶度和热稳定性,其结构基本实现超稳化.     

CXN天然沸石的研究VII. 骨架高硅超稳化改性

以高硅超稳化辉沸石(STI)为基底沸石, 分别经盐酸脱铝或氟硅酸铵脱铝补硅处理后制备的改性H-STI沸石, 其非骨架铝含量明显减少, 而后者骨架硅铝比进一步提高. X射线荧光散射光谱(XRF), ²⁷Al高分辨率魔角旋转固体核磁共振(MAS NMR), 红外(FT-IR)光谱等表征证明改性后的沸石骨架硅铝原子比分别为6.8和11.4. 低温氮吸附表明, 经盐酸处理的高硅STI沸石孔道开放完美, 但经氟硅酸铵处理的样品孔道被部分堵塞. 分段程序升温焙烧表明前者骨架热稳定性略差, 1000 ℃焙烧后结构基本被破坏, 而后者热稳定性较好, 经相同温度段焙烧后仍保持较高的结晶度和热稳定性, 其结构基本实现超稳化.     

CXN天然沸石的研究Ⅶ.骨架高硅超稳化改性

以高硅超稳化辉沸石(STI)为基底沸石,分别经盐酸脱铝或氟硅酸铵脱铝补硅处理后制备的改性H-STI沸石,其非骨架铝含量明显减少,而后者骨架硅铝比进一步提高.X射线荧光散射光谱(XRF),27Al高分辨率魔角旋转固体核磁共振(MAS NMR),红外(FT-IR)光谱等表征证明改性后的沸石骨架硅铝原子比分别为6.8和11.4.低温氮吸附表明,经盐酸处理的高硅STI沸石孔道开放完美,但经氟硅酸铵处理的样品孔道被部分堵塞.分段程序升温焙烧表明前者骨架热稳定性略差,1000℃焙烧后结构基本被破坏,而后者热稳定性较好,经相同温度段焙烧后仍保持较高的结晶度和热稳定性,其结构基本实现超稳化.     

Properties of aluminium oxides obtained by calcination of the products of reductive roasting of basic aluminium-potassium sulfate

The influence of calcination conditions on changes in phase composition and porous structure was studied for hydrous aluminium oxide, obtained by leaching out potassium salts from the products of roasting basic aluminium-potassium sulfate in hydrogen atmosphere at 600°C. The product of calcination at 350°C in vacuum has the most developed porous structure with most pores of internal radius within 10–60 Å. Calcination in air atmosphere at temperatures 700, 800, 900, or 1000°C resulted in decrease of specific surface of aluminium oxide and increase of the share of pores with internal radius above 60 Å in the overall porosity of the samples. The reconstruction of the porous structure proceeds mainly as a result of coalescent sintering.     

Friedel–Crafts acylation of anisole over Cr-doped Hβ zeolite

Cr-doped Hβ zeolite is found to have better catalytic performance than Hβ zeolite in the Friedel–Crafts acylation of anisole, with acetic anhydride conversion of over 99% and nearly 100% selectivity to furnish para-methoxyacetophenone under the optimized reaction conditions. This is attributed to the increase of weak and moderately strong acid sites, caused by the Cr addition. The formation of carbonaceous materials and their coating of the acid sites are believed to be the reasons for the deactivation of the reused Cr-doped Hβ zeolite, as indicated by the Brunauer?Emmett?Teller (BET) method, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and NH₃ temperature-programmed desorption (NH₃-TPD) measurement results. The catalyst activity can be recovered by a subsequent calcination.     

Identification and estimation of extra-framework aluminium in acidic mazzite by diffuse reflectance spectroscopy

Diffuse reflectance spectroscopy has been used to investigate structural modification of mazzite zeolite subjected to calcination, acid leaching and acetylacetone treatments. Extra-framework aluminium species, formed upon expulsion of aluminium from the framework, are detected by DRS because they are involved in aluminium-oxygen charge transfer transitions. Impregnation of the calcined ammonium-exchanged and acid leached samples with ethanolic acetylacetone will convert the broadened 260-280 nm band of extra-framework aluminium with distorted symmetry to a distinct well-defined 285 nm band. The appearance of this band is due to the transformation of the aluminium atoms with a different coordination number to structures with highly ordered octahedral symmetry. Washing the acetylacetone treated samples with hot ethanol leads to extraction of some of the complexed aluminium. The presence of an extracted aluminium triacetylacetonate complex in the eluant is verified by the same spectrophotometer used in its conventional mode. This suggests that a dual DR and UV-VIS spectrophotometry is an appropriate approach to study such topics.     

Incorporation of Silicon into AlPO-5 Framework Sites: Higher Thermal Stability and Lower Extra-Framework Aluminum Concentration

Diffuse reflectance spectroscopy was used to investigate the structural modification of AlPO-5 microporous aluminophosphate synthesized in the presence of a silicon source and subjected to calcination in air. Extra-framework aluminium species, formed upon calcination and expulsion of aluminium from the framework, are detected by DRS because they are involved in aluminium-oxygen charge transfer transitions. Impregnation of the calcined AlPO-5 and SAPO-5 samples with ethanolic acetylacetone converted all the extra-framework aluminium atoms with distorted symmetry to a highly ordered symmetry, as evidenced by a distinct and well-defined 280 nm band in the DR spectra. The intensity of the 280 nm absorption band in AlPO-5 is much higher than those of all SAPO-5 samples with different silicon content. This is an indication of the presence ofa considerably higher amount of extra-framework aluminium in AlPO-5. Washing the acetylacetone treated samples with hot ethanol leads to extraction of some of the complexed aluminium. The progress of extraction could be monitored by both DR and UV-vis spectrophotometry.     

杂原子Sn-β分子筛的脱铝补位两步法制备、表征及其催化环己酮Baeyer-Villiger氧化性能

采用酸处理Al-β脱铝以产生T"空位",再高温焙烧插入Sn,即脱铝补位两步法制备了杂原子Sn-β分子筛.考察了β沸石中T"空位"数量、母体硅铝比和焙烧温度等因素对Sn-β分子筛形成与性能的影响,并利用X射线衍射、红外光谱、紫外-可见光谱、扫描电镜、X射线荧光光谱和电感耦合等离子体原子发射光谱等手段及环己酮Baeyer-Villiger(B-V)氧化反应,对催化剂进行了表征和评价.结果表明,脱铝补位两步法可以制备Sn-β分子筛,且Sn以四配位形式存在于分子筛骨架中,在对环己酮B-V氧化反应中表现出较高的催化活性.     

Design of molecularly ordered framework of mesoporous silica with squared one-dimensional channels

Mesoporous silica with squared one-dimensional channels (KSW-2-type mesoporous silica), possessing a molecularly ordered framework arising from a starting layered polysilicate kanemite, was obtained through silylation of a surfactant (hexadecyltrimethylammonium, C16TMA)-containing mesostructured precursor with octoxytrichlorosilane (C8H17OSiCl3) and octylmethyldichlorosilane (C8H17(CH3)SiCl2). The presence of the molecular ordering in the silicate framework was confirmed by XRD and TEM. Octoxy groups grafted on KSW-2 can be eliminated by subsequent hydrolysis under very mild condition, and pure mesoporous silica was obtained with the retention of the kanemite-based framework. The framework is structurally stabilized by the attachment of additional SiO4 units to the framework, and the mesostructural ordering hardly changed under the presence of water vapor. A large number of silanol groups remained at the mesopore surfaces because C16TMA ions and octoxy groups can be removed without calcination. Octylmethylsilyl groups are regularly arranged at the mesopore surface due to the molecular ordering in the silicate framework. The molecularly ordered structural periodicity originating from kanemite is retained even after calcination at 550 degrees C, while that in the precursor without silylation disappeared. The synthetic strategy is quite useful for the design of the silicate framework of mesostructured and mesoporous materials with and without surface functional organic groups.     

液固相同晶取代法制备Sn-NaY催化环己酮Baeyer-Villiger氧化

以微孔分子筛NaY为载体,SnCl_4·5H_2O为锡源,通过液固相同晶取代法制备催化材料Sn-NaY,研究了脱铝预处理和焙烧两个因素对制备Sn-NaY的影响.采用FT-IR、UV-Vis、XRD、N_2物理吸附、ICP、NH_3-TPD、吡啶红外、激光拉曼等手段对催化材料进行了表征.结果表明:对载体进行脱铝预处理有利于分子筛在催化剂制备过程中保持良好的骨架结构,焙烧有利于进入分子筛骨架中的Sn(Ⅳ)与硅羟基成键,从而形成有催化活性的四配位的Sn(Ⅳ),而空气氛围下焙烧容易产生骨架外SnO_2物种.Sn-NaY催化环己酮Baeyer-Villiger氧化结果表明,在环己酮0.03 mol,n(H_2O_2)∶n(酮)=1.5∶1,0.35 g催化剂,15 mL乙腈,70℃反应24 h的工艺条件下,N_2氛围焙烧的同晶取代脱铝催化剂性能最好,环己酮的转化率可达44%,己内酯的选择性为62%.     

Variation of Aluminium Distribution in Small-Sized ZSM-5 Crystals during Desilication

Hollow ZSM-5 zeolites of size below one micrometer can be produced by desilication of crystals with aluminium zoning. The parent crystals have a core–shell structure: the core part has nearly no aluminium, whereas the aluminium content in the shell increases when extending to exterior surface. Transmission electron microscopy confirmed the preservation of the crystalline shell after base leaching, but could not identify its subtle change. An increase of the Si/Al ratio of the surface was detected upon leaching the parent material to form the hollow zeolite by using ambient pressure X-ray photoelectron spectroscopy and infrared spectroscopy of substituted alkylpyridines. ²⁷Al MAS NMR showed that base leaching results in a reduced percentage of distorted tetrahedrally coordinated aluminium. The reprecipitation of dissolved species occurs and tetrahedrally coordinated tin atoms can thus be introduced to the shell framework. Overall, the formation of hollow ZSM-5 zeolites by desilication involves not only the removal of silicon-rich core, but also a reduced percentage of exterior aluminium-related acid sites, which should be considered while using hollow zeolites in acid-catalyzed reactions.     

乙烯催化转化制备乙二醇反应中TS-1分子筛的失活

采用连续循环反应的方式考察了TS-1分子筛在催化双氧水氧化乙烯制备乙二醇反应中的失活过程.其中,新鲜、反应后和再生的TS-1分子筛采用氮气物理吸附、XRF、SEM、XRD、FT-IR和UV-vis等技术进行表征,反应后分子筛表面的吸附物种分别采用FT-IR、GC-MS和TG-DTA进行定性和定量分析.结果表明,反应过程中TS-1分子筛未发生明显的Ti物种的流失,乙二醇低聚物等大分子有机物在分子筛微孔通道内的聚集而引起的孔道堵塞和活性Ti位点可及度的降低是分子筛部分失活的主要原因.失活后的催化剂可以通过双氧水处理移除其表面吸附的物种而部分再生,而高温焙烧可以彻底清除分子筛孔道内沉积的有机物从而恢复分子筛的催化活性.     

以无机铝盐为前驱体用溶胶凝胶法合成中孔氧化铝

以水合硝酸铝(Al(NO3)3·9H2O)为前驱体, 通过乙醇介质中环氧丙烷的开环反应促使形成了透明的块状氧化铝凝胶. 凝胶在常压下干燥并于700 ℃焙烧后得到中孔无定型氧化铝. 通过改变环氧丙烷的加入量实现了氧化铝孔径和孔体积等宏观结构性能的调节. 用扫描电镜(SEM)、傅立叶变换红外光谱(FI-IR)和差热分析(DTA)等方法对样品进行了表征. 由于合成中存在环氧丙烷开环产物作为液体模板剂的造孔作用, 在氧化铝凝胶中造成了孔分布曲线具有双峰分布的墨水瓶状孔. 反应过程中pH值的测定和红外光谱的表征结果都证明环氧丙烷是一种很好的质子消耗剂, 其开环促使铝离子水解聚合并形成凝胶网络结构. 同时根据表征结果对环氧丙烷参与的溶胶凝胶氧化铝的合成机理进行了探讨.