Y分子筛的改性及在加氢脱氮反应中的催化性能

采用水热法与草酸脱铝相结合法对Y分子筛进行改性,用孔体积饱和浸渍法制备了Ni-W/γ-Al2O3-USY加氢精制催化剂,考察了改性Y分子筛对催化剂的酸性及催化剂的HDN活性的影响,并对制备的催化剂进行了酸性表征。随着草酸加入量的增多,催化剂的总酸量减少;随着处理温度的增高,弱酸和强酸量分别有不同程度的增多。催化剂中适量的USY可以明显提高催化剂的总酸量,并提供对喹啉HDN的适中酸强度,明显提高催化剂的HDN活性。     

A catalytic and characterization study of the surface acidity generated on the reduction of copper exchanged Y zeolites

Zeolite acidity, in the form of Bronsted acid sites generated on reducing a range of copper Y zeolites, was probed by infrared spectroscopy. The nature of the alkali metal co-cation (Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺) is shown to influence both the acid strength and location of the Bronsted sites. Acid strength decreases in the order CuLiY > CuNaY > CuKY > CuRbNaY > CuCsNaY. The specific effect of the alkali metal co-stations on the level of protonic activity in benzene ethylation and cumene cracking is discussed.     

Characterization and performance evaluations of sodium zeolite‐Y filled chitosan polymeric membrane: Effect of sodium zeolite‐Y concentration

Sodium zeolite‐Y (NaY zeolite) filled chitosan polymeric membranes were developed and characterized. The impact of adding different concentrations of NaY zeolite into the homogeneous chitosan membrane was investigated. The surface morphology, mechanical–physical properties, sorption, and pervaporation performance for the dehydration of isopropanol–water mixture separation by the pervaporation process were studied and evaluated. A homogeneous chitosan membrane showed preferential water sorption and permeation compared to isopropanol. The optimum concentration of NaY zeolite added to the homogeneous chitosan membrane was 0.4 wt %, which showed that the dispersion of the NaY zeolite was the most homogeneous and finely covered by the chitosan polymer in the zeolite–chitosan polymer interface. The tensile strength and percent strain at maximum of this membrane were 59.347 MPa and 27.5%, respectively. The sorption experiments showed that the degree of swelling was 6.54% with 1.01 wt % isopropanol sorbed in these membranes. The pervaporation separation tests demonstrated that the NaY zeolite filled chitosan membrane was capable for isopropanol–water mixture separation and improved the pervaporation separation index from 272 (homogeneous chitosan membrane) to 2687. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1740–1751, 2006     

Dealumination of zeolite Y by H4EDTA

Solid-state NMR shows that the treatment of zeolite Y by H₄EDTA dealuminates the zeolite framework. Since no extra-framework aluminium is found, all the Al removed from the framework is subsequently washed out of the crystallites in the form of an H₄EDTA complex. Unlike with hydrothermal dealumination or treatment with SiCl₄, H₄EDTA gives defective crystals in which framework vacancies created by the expulsion of aluminium are not healed by silicon from other parts of the framework. The likely reason for this is the slow intracrystalline diffusion of Si(OH)₄ at low temperatures.²⁹Si CP/MAS NMR and infrared spectra confirm the creation of hydroxyl nests in the zeolitic framework. A small amount of disordered siliceous phase responsible for a low intensity²⁹Si MAS NMR shoulder at –110 ppm is produced in the process.On leave from the Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, 30-239 Krakow, Niezapominajek 1, Poland.     

不同金属、配体的ML/Y对苯加氢催化性能的研究

采用自由配体法制备了系列M(Salen)/Y(M=Ni,Pd and Ru)和RuL/Y[L=phenanthroline(phen),2,2′-bipyridyl(bpy) and N,N′-ethylenebis (salicylidene-aminato) (Salen)]催化剂,分别考察了金属元素性质和不同配体性质对所制催化剂催化加氢性能的影响,结果表明Ru(Salen)/Y的催化加氢活性优于Pd(Salen)/Y和Ni(Salen)/Y;不同性质与结构的配体对所制催化剂的催化加氢性能也有很大的影响,以Salen希夫碱为配体所制备的RuL/Y催化活性高于以二联吡啶(bpy)和邻菲咯啉(phen)为配体所制备的催化剂.     

The catalytic dehydrogenation of cyclohexane and methylcyclohexane over nickel loaded Y zeolites

The dehydrogenation of cyclohexane to benzene and of methylcyclohexane to toluene was investigated over a range of nickel Y zeolites, varying the nickel content and the nature of the alkali metal co-cation (Li⁺, Na⁺, K⁺, Rb⁺ or Cs⁺). The overall reaction is viewed as occuring via a series of consecutive dehydrogenation steps. Catalytic activity is correlated with the reaction time, the reaction temperature, the level of Ni²⁺ exchange and the effects of pyridine adsorption. The level of dehydrogenation is strongly dependent on the mass of supported nickel metal and the surface Bronsted acidity. Catalyst deactivation results from the deposition of coke on the catalyst surface which is promoted with increasing zeolite acidity.     

Competitive reactions catalyzed by NiMo-containing zeolites

The rates of benzene hydrogenation and of n-heptane hydroconversion were measured simultaneously over a series of bifunctional catalysts. The catalysts were Y zeolites containing a Ni or Mo sulfide. At 280 °C, and for the more acidic catalysts, both rates appeared linearly correlated, suggesting that the hydrogenation function was limiting.     

Advances in Oxidation Catalysis; Oxidation of Benzene to Phenol by Nutrous Oxide

Recent decades show impressive progress in oxidation catalysis, resulting in many novel industrial technologies. However, there is a difficult and challenging field, that of oxidation reactions which cannot be selectively implemented via traditional approaches. In the present paper, we discuss recent progress achieved in this particular field through the discovery of unique oxidation chemistry involving nitrous oxide.     

苯分子在Y沸石中跳跃扩散机制的动力学Monte Carlo模拟

利用动力学Monte Carlo （KMC）模拟方法计算了苯在Y沸石中扩散的自扩散系数,并考察了3种不同W-W位间跳跃扩散机制下的自扩散系数及其对温度和浓度的依赖关系.实验测量结果表明,苯在Y沸石中的长程运动主要是经S_Ⅱ-W-S_Ⅱ笼间的跳跃,基本不发生W-W之间的跳跃.相应得到的自扩散系数对温度的依赖关系较接近实验值;自扩散系数浓度依赖变化趋势为：先随覆盖量的增加而减小,到覆盖量大于S位的饱和覆盖量（每个超笼中4个分子）后,则随覆盖量增加先增后减,但也不会大于零覆盖量时扩散系数值,该情形与考虑W-W之间跳跃时完全不同.此外,模拟结果表明,使用正确的跳跃机制是KMC方法能正确模拟客体分子在沸石内扩散行为的关键.     

海藻酸钠-氢氧化镧改性Y型分子筛颗粒除氟研究

为解决除氟吸附剂分离困难、有效成分流失等问题,以海藻酸钠（SA）与氢氧化镧改性Y型分子筛（LHMS）为原料,采用滴球法制备了SA@LHMS颗粒吸附剂,并采用模拟废水对其进行了除氟研究。通过正交实验确定了吸附剂最佳制备条件,并通过间歇吸附实验测试了吸附剂投加量、pH、共存离子等因素对吸附的影响,探究了吸附速率、吸附等温线等吸附性能。结果表明,SA@LHMS吸附速率曲线符合拟二级反应速率方程;吸附等温线符合Ⅱ型等温线,为多分子层吸附;初始pH（3~12）对吸附效果没有显著影响;高浓度共存阴离子（50 mg/L）对吸附过程有一定抑制;1 mol/L和2 mol/L氢氧化钠溶液对SA@LHMS再生效果较好,经3次再生仍然保留较高的吸附能力。SA@LHMS颗粒表面和截面形态以及吸附前后颗粒的表面形态差异明显;吸附前后颗粒表面能谱（EDS）分析以及红外光谱（FT-IR）分析结果显示,吸附过程中溶液中的氟离子（F^-）与颗粒表面及内部的羟基（—OH）发生配体交换。     

Novel solid basic catalysts by nitridation of zeolite beta at low temperature

New basic solid catalysts are obtained by nitridation of zeolite beta at temperatures as low as 300 °C. These materials exhibit excellent catalytic activity in the Knoevenagel condensation of benzaldehyde with dicyanomethane (malononitrile). Nitridated samples of zeolite beta were prepared by treating the parent materials in an ammonia flow at temperatures between 300 °C and 800 °C for 24 h and 48 h, respectively. Samples of zeolite beta nitridated at 300 °C for 24 h or 48 h exhibited excellent catalytic activities which are higher than those observed for beta-type catalysts nitridated at higher temperatures and higher than activities reported earlier for ammonia treated aluminosilicates, AlPOs, SAPOs, and mesoporous silicon oxinitride materials. The nitridated beta zeolites were characterized by powder XRD, FTIR, nitrogen adsorption and elemental analysis techniques. It is suggested that the presence of silanol groups along with basic –NH₂ functional groups is responsible for the exceptional activity of the catalysts treated at low temperature.     

Electrochemically controlled ion exchange: Copper ion exchange with sodium zeolite Y

An electrochemically controlled method to drive ion exchange within zeolites is applied to the incorporation of Cu²⁺ into NaY. The technique uses the polarised liquid/liquid interface to transfer sodium ions selectively - and controllably - from the exchange medium, into an adjacent organic phase. The electrochemical removal of the unwanted ions from the exchange medium drives equilibrium toward greater exchange of the desired ion. Analytical data in support of the ion-exchange process is presented and an approximate calculation of the extent of ion exchange, as a function of charge passed, is described. This method has the potential to be very effective for the exchange of ions with low affinity for the parent zeolites, and to reach 100% exchange.     

Mesoporous zeolite single crystal catalysts: Diffusion and catalysis in hierarchical zeolites

During the last years, several new routes to produce zeolites with controlled mesoporosity have appeared. Moreover, an improved catalytic performance of the resulting mesoporous zeolites over conventional zeolites has been demonstrated in several reactions. In most cases, the mesoporous zeolites exhibit higher catalytic activity, but in some cases also improved selectivity and longer catalyst lifetime has been reported. The beneficial effects of introducing mesopores into the zeolites has in most instances been attributed to improved mass transport to and from the active sites located in the zeolite micropores. Here, we briefly discuss the most important ways of introducing mesopores into zeolites and, for the first time, we show experimentally that the presence of mesopores dramatically increases the rate of diffusion in zeolite catalysts. This is done by studying the elution of iso-butane from packed beds of conventional and mesoporous zeolite catalysts. Moreover, we discuss in detail the recent observation of improved activity and selectivity in the alkylation of benzene with ethene using mesoporous zeolite single crystal catalysts. For this reaction, we show by calculation of the Thiele modulus that this improved performance can be mainly attributed to a diffusional limitation of ethylbenzene in the zeolite pores. This is verified in new ethylbenzene dealkylation experiments where mesoporous zeolite catalysts show significantly improved activity over conventional zeolite catalysts.     

Olefin oligomerization via zeolite catalysis

Oligomerization of terminal and internal long-chain, linear olefins has been successfully demonstrated using large pore zeolites with high silica-to-alumina ratios as catalysts. Both reactant and product selectivities have been demonstrated using 12-membered ring zeolites for the oligomerization of C₁₂–C₁₈ olefins. The catalytic activity of these zeolites decreases in the order faujasite > mordenite > pentasil; the activity of the Y-zeolites depends primarily upon the silica-to-alumina molar ratio, but not on the total acidity. 1-tetradecene oligomerization, followed by oligomer hydrogenation, yields synthetic lubricant base stocks with excellent physical characteristics.     

Preparation of bisphenol-A over zeolite catalysts

The reaction of phenol and acetone to give bisphenol-A (4,4-isopropylidenediphenol) has been investigated using zeolite as catalysts. The zeolites are less active and selective than the cation-exchange resin, Amberlyst-15.     

生产氯代环己烷的工艺研究

苯部分加氢生产氯代环己烷,经济,安全,无环境污染,从理论上探讨了采用苯部分加氢制环己烯,再由环己烯与氯化氢加成生产氯代环己烷工艺的可行性及反应条件。同时考察了所得产品的分离方法,以及在分离过程中的影响因素：温度、压力、回流比、加热量等,发现采用变回流比时,操作所得产品最理想。     

Nanosized zeolite films for vapor-sensing applications

Colloidal zeolites LTA and BEA sized below 100 nm were synthesized as building blocks for the controlled growth of thin microporous films on piezoelectric sensor devices (quartz crystal microbalance, QCM). The zeolite films were prepared on pre-seeded gold substrates on QCM devices. Initially, a layer of colloidal particles was deposited on the support through chemical bonding with a silane coupling agent, followed by hydrothermal growth. BEA- and LTA-type zeolite films with thicknesses of 250 and 450 nm, respectively, were prepared by optimizing the synthesis conditions. The application of these zeolite films in microsensors for water and organic compounds is presented. The importance of the zeolite structure type with respect to the sensitivity towards different organic and water vapors at various concentrations is discussed. Both zeolites are thermally stable and show reproducible responses during long-term experiments. Based on these results, it was concluded that both zeolite films could be used effectively as humidity sensor materials for water vapor sensing purposes. High sensitivity, good reversibility and long life were demonstrated for this type of zeolite film at low water concentrations. In comparison to LTA, the BEA films show a higher sorption capacity towards water vapor and no rejection of pentane, hexane and cyclohexane, due to the larger pore size of the BEA structure.     

新型镍催化剂在苯加氢中的应用研究

采用溶胶-凝胶法制备新型镍催化剂。采用微型反应装置,在反应压力为0.78MPa,氢苯摩尔比为6.5∶1,反应温度358.15~633.15K的实验条件下,研究了在NiO-MoO3/Al2O3-TiO2催化剂上苯加氢生成环己烷的反应。结果表明,在383.15~513.15K的温度范围内苯的转化率为100%,反应所得环己烷的纯度超过99.8%。     

Rhodium supported in basic zeolite Y: A selective and stable catalyst for CO hydrogenation

Catalysts prepared by a condensation reaction of Rh(CO)₂(acac) within the supercages of zeolite Y made basic by treatment with NaN₃ are active for CO hydrogenation and selective for low-molecular-weight olefins and methanol. High partial pressures of CO (or CO + H₂) stabilize the catalyst. The predominant species in the catalyst are suggested to be rhodium carbonyl clusters trapped in the zeolite cages.     

Phenol alkylation with methanol: effect of sodium content and ammonia selective poisoning of an HY zeolite

Sodium exchange and ammonia selective poisoning of the acid sites of an HY zeolite (Si/Al=20) were carried out and their effects on the catalytic properties for the alkylation of phenol with methanol (200C, 1 atm and N₂/reactants molar ratio of 4) were evaluated. Results show that the reaction is highly sensitive to the number and strength of the acid sites of the catalyst. A decrease in the number of acid sites by sodium exchange of the protons or by ammonia selective poisoning produces important changes in the selectivity of the reaction. In fact, a high increase in the anisole/cresol ratio is observed as the percentage of exchanged sodium in the zeolite increases, while the ammonia selective poisoning shows that at low desorption temperatures (250C) only anisole is formed while at higher desorption temperatures both anisole and cresols were observed. These results show that anisole formation requires sites with lower acid strength compared to those necessary for cresol formation.