A heterostructured titanium silicalite-1 catalytic composite for cyclohexanone ammoximation

Submicron-sized titanium silicalite-1 is difficult to recover in industrial process because of their fineness and rapid decrease in catalytic activity due to particle agglomeration. To solve these problems, we present a heterostructured titanium silicalite-1 (TS-1) catalytic composite using bentonite clay as the catalyst support. The catalytic composite is synthesized by hydrothermal treatment which directly crystallizes TS-1 on the bentonite clay surface. The synthesized composite has been characterized using scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy. The TS-1 crystals have been found on and between the layers of the bentonite with strong attachment. Characterizations suggest that crystallization temperature of 175 °C is the optimum hydrothermal temperature to produce TS-1 on the bentonite support with characteristics necessary to promote selective catalytic reactions. It is found that prolonged crystallization duration does not necessarily increase the crystallinity of TS-1 on the bentonite surface. The heterostructured composite is able to maintain high conversion of cyclohexanone (97%) and oxime selectivity (83%) after three reaction cycles which is contrary to the unsupported TS-1 that shows apparent decrease in activity (>10%), especially in the selectivity to oxime. The synthesized composite also has significant improvement in separation efficiency with respect to the unsupported catalytic system. Therefore, we conclude that the heterostructured TS-1 composite is a promising catalytic material for cyclohexanone ammoximation and potentially for other TS-1 related processes where catalyst recovery and reuse are required.     

多级孔钛硅分子筛制备及其催化羟基化性能

通过溶胶-凝胶法,以十六烷基三甲基溴化铵（CTAB）为模板剂,合成了多级孔钛硅分子筛（h-TS-1）。运用透射电子显微镜（TEM）、X射线衍射（XRD）、氮气等温吸附-脱附、紫外-可见漫反射光谱（DR UV-Vis）和傅里叶红外光谱（FT-IR）对h-TS-1的结构进行了表征;考察了h-TS-1在温和条件下用过氧化氢作氧化剂对直接羟基化苯和苯酚反应的催化活性。结果表明:h-TS-1除具有和TS-1相同的MFI结构和良好的晶型外,还同时具有微孔和介孔结构,平均孔径为2.67 nm;h-TS-1对目标反应的催化活性明显优于TS-1;h-TS-1具有良好的可重复利用性。     

Effect of sodium ions in synthesis of titanium silicalite-1 on its catalytic performance for cyclohexanone ammoximation

Titanium silicalite-1 (TS-1) has been hydrothermally synthesized with tetrapropylammonium hydroxide (TPAOH) as the template in the presence of various amounts of Na⁺, characterized by inductively coupled plasma, X-ray diffraction, scanning electron microscope, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and ultro-violet-visible spectroscopy and studied in cyclohexanone ammoximation. The characterization results show that with the increase of Na⁺ concentration in the synthesis, both the crystal sizes of TS-1and extra framework Ti increase but framework Ti decreases. The addition of Na⁺ below 3 mol-% of TPAOH in the synthesis does not influence the catalytic properties with above 98% conversion of cyclohexanone and 99.5% selectivity to cyclohexanone oxime. However, at the concentrations of Na⁺≥3 mol-% of TPAOH in the synthesis, the catalysts are deactivated faster with the increase of Na⁺ addition, which can be attributed to more high molecular weight byproducts deposited in the large TS-1 particles and the loss of the frame-work titanium. The results of this work are of great importance for the industry.     

钛硅分子筛TS-1催化烯烃环氧化反应的研究进展

TS-1催化的烯烃环氧化反应具有条件温和、环境友好、符合绿色化学理念、应用前景广阔等优点.该文首先介绍了不同介质中TS-1催化过氧化氢(H2O2)氧化脂肪烯烃反应的进展,结果表明,在甲醇等质子溶剂中,溶剂可以和Ti—OOH(钛氧活性中心)通过氢键作用形成活性中间体,实现烯烃的环氧化;同时,TS-1的酸中心易引发环氧化物...     

Effect of triethylamine treatment of titanium silicalite-1 on propylene epoxidation

Titanium silicalite-1(TS-1) treated with triethylamine (TEA) solution under different conditions was characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectrum (FTIR), ultraviolet-visible diffuse reflectance spectrum (UV-Vis), nitrogen physical adsorption and desorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The characterization results show that many irregular hollows are generated in the TS-1 crystals due to the random dissolution of framework silicon and the volume of the hollow cavities increase with increasing the TEA concentration, and the treatment temperature and time. The modified TS-1 samples improved in varying degrees the catalyst life for the epoxidation of propylene in a fixed-bed reactor probably due to the generation of the hollows to make it easy for the reactants and products to diffuse out of the channels.     

Characterization and catalytic properties of titanium silicalite-1 catalyst

Titanium silicalite 1 (TS-1) catalyst was prepared by three different hydrothermal synthesis methods. XRD, elemental analysis, SEM, IR,²⁹Si MAS NMR, UV-vis DRS, physical adsorption of nitrogen, and EXAFS analysis were then performed to evaluate its physical properties. For a test of catalytic activity, liquid phase 2-butanol oxidation and 1-hexene epoxidation using hydrogen peroxide as an oxidant were conducted. The crystal size of the TS-1 catalyst was shown to have a considerable effect on the 1-hexene epoxidation, and smaller crystals resulted in higher activity.     

Highly stable monolithic titanium silicalite-1 catalyst for 1-butene epoxidation

A monolithic titanium silicalite-1 (TS-1) catalyst was prepared by coating TS-1 onto a specially designed stainless-steel support. The catalyst was used in 1-butene epoxidation, a strong exothermic reaction, to produce butene oxide in a fixed-bed reactor. Compared with the traditional extruded TS-1, the monolithic catalyst demonstrates excellent catalytic stability and reusability. To understand the reason for this performance, heat conduction behaviors of the monolithic and extruded catalysts were studied and compared. This was accomplished by firstly developing a kinetic model to determine reaction kinetic parameters, and then simulating the temperature distribution within the reactor. It revealed a much lower temperature-rise over the monolithic catalyst than over the extruded catalyst. This study demonstrates that the stainless-steel support of the monolithic catalyst is effective in dissipating high reaction heat of 1-butene epoxidation, thus limits local temperature-rise within the reactor. This inhibits the formation of channel-blocking byproducts and improves the catalytic stability.     

钛硅分子筛TS-1动态过滤的研究

对钛硅分子筛TS 1微粉催化剂应用动态过滤技术 ,在动态旋叶压滤机上进行了过滤性能的研究 ,得到了过滤速率随时间的变化规律 ,并分析了操作压力对过滤速率的影响。为了结合实际工业生产的要求 ,对过滤介质进行了再生实验。该研究为TS 1微粉催化剂的过滤分离提供了一个可行的方法 ,为确定适宜的操作条件及工业应用提供了实验依据     

Structured silicalite-1 encapsulated Ni catalyst supported on SiC foam for dry reforming of methane

Structured silicalite-1 zeolite encapsulated Ni catalyst supported on silicon carbide foam (i.e., Ni@S1-SiC) was prepared using a new yet simple one-pot method, showing the significantly improved anti-sintering and anti-coking performance in comparison with the conventional supported and encapsulated Ni catalysts (i.e., Ni/S1, Ni/S1-SiC, and Ni@S1), in catalytic dry reforming of methane (DRM). The developed Ni_0.08@S1-SiC catalyst showed high CO₂/CH₄ conversions of >85% and H₂/CO molar ratio of >0.85 at 700°C, outperforming other control catalysts under investigation. Additionally, the Ni_0.08@S1-SiC catalyst demonstrated high turnover frequency (TOF) values of ~5.6 and ~2.1/s regarding to CO₂/CH₄ conversions at 400°C, exhibiting excellent stability and low pressure-drop during 100 hr on stream evaluation. Post-reaction characterization of the used catalysts demonstrated that the combination of zeolite encapsulated Ni catalysts and SiC foam enabled well-dispersed and ultrafine Ni nanoparticles, low pressure drop and intensified transfer steps, presented excellent anti-sintering and anti-coking abilities.     

TS-1分子筛催化环己酮氨肟化反应的失活动力学

采用间歇反应器,对液相环己酮氨肟化过程中TS-1分子筛的催化活性变化规律进行了考察,在失活原因分析的基础上建立失活动力学模型:rde=1.01×1014exp(-1.17R×T105)C0A.76C0B.82C0C.38a1.64,并对模型参数进行估值。     

在玻璃上合成有取向的silicalite-1分子筛膜及其生长机理

引言 分子筛膜具有规则的微孔结构、良好的化学和热稳定性,在气体分离、催化膜反应器、化学传感器以及分子筛改性电极等方面有广泛的应用前景[1-2],是催化和分离新材料领域的研究热点之一.     

应用于环己酮氨肟化反应的TS-1研究进展

环己酮氨肟化工艺是己内酰胺新技术发展的必然趋势之一,而钛硅分子筛TS-1的制备是环己酮氨肟化工艺的核心技术。但由于TS-1合成成本昂贵,合成条件苛刻,制备重复性差,制约了工业化的发展,仍需要不断的技术进步。本文针对这一主题,对环己酮氨肟化反应所需的TS-1催化剂的制备包括TS-1的改性、大颗粒TS-1的制备、复合TS-1的制备、TS-1的成型及其他的TS-1制备工艺等技术进行了系统综述。在环己酮氨肟化反应中,提高TS-1的催化活性、解决工业上TS-1的分离和回收难题、提高TS-1制备的稳定性和产量、降低成本等是未来TS-1研究的发展趋势。     

钛硅分子筛中钛原子落位的讨论

采用计算化学方法,使用密度泛函理论计算TS-1分子筛十二个不同T位的5T模型、8T模型与模板剂TEA+结构和能量,讨论Ti原子进入TS-1分子筛的优先落位。通过对弛豫能结果的分析,发现T3和T12位的结构柔性最大。通过Ti进入十二个不同T位的取代能和其与TEA+相互作用能的比较,得出不同T位的优先顺序为T1、T12T2、T3、T6、T7、T8、T9T4、T5、T10、T11。综合比较结构的柔性和总能量,得出了T12位是钛原子的最优先落位。     

Epoxidation of Propylene with Hydrogen Peroxide Over TS-1 Catalyst Synthesized in the Presence of Polystyrene

Titanium silicalite-1 (TS-1) catalyst was synthesized in the presence of polystyrene (PS) particles (denoted as TS-1_PS catalyst) for use in the epoxidation of propylene with hydrogen peroxide. For the purpose of comparison, TS-1 catalyst was also synthesized by a conventional method (in the absence of polystyrene particles). In the epoxidation of propylene, the TS-1_PS catalyst showed a higher conversion of hydrogen peroxide and a higher selectivity for propylene oxide (PO) than the TS-1 catalyst. Consequently, the TS-1_PS catalyst showed a higher yield for PO than the TS-1 catalyst. Characterization results showed that the high catalytic performance of TS-1_PS was attributed to the enhanced hydrophobic property of the catalyst and the suppressed formation of anatase TiO₂ in the catalyst.     

混合型TS-1/CNF催化剂的过滤性能及催化活性

纳米碳纤维（CNF）是一种新型的碳基催化剂载体。采用机械湿混的方式制得了混合型钛硅分子筛/纳米碳纤维（TS-1/CNF）催化剂,研究了其在水相体系中的过滤性能,以及在环己酮氨氧化反应中的催化活性。与单独TS-1相比,混合型TS-1/CNF催化剂的团聚体宏观尺寸较大,CNF交织形成的大量大孔非常有利于液体的穿透,使得TS-1/CNF催化剂具有良好的过滤性能,因而可改善TS-1在水相体系中的分离问题。SEM观察显示,CNF具有独特的长纤维结构以及较大的外表面,为TS-1微粒提供了较多的附着点,使得TS-1能均匀分布在CNF表面上。TS-1颗粒与直径处于相同尺度的CNF之间可能存在着较强的分子间作用力、静电作用力及疏水作用力,可避免分散和过滤过程中两者的分离。混合型TS-1/CNF催化剂上环己酮氨氧化反应的结果表明,环己酮的转化率接近100%,环己酮肟收率达98.4%,与纯TS-1的催化活性相当。     

低成本TS-1的制备及其在丙烯环氧化中的应用

综述了低成本钛硅分子筛TS-1的制备及其在丙烯环氧化反应中的应用研究进展。低成本TS-1制备过程实现工业化主要存在粉末状TS-1的回收和过氧化氢的生产、储存等问题。提高活性及进一步降低成本是研究的重点。过氧化氢的生产与丙烯环氧化过程的集成是未来的发展方向。     

TS-1合成时晶种与模板剂的协同导向作用

在无机钛硅原料体系合成TS - 1时 ,加入晶种 ,模板剂TPABr (orTPAOH)的用量大量减少甚至可以低于极限用量。实验发现晶种和模板剂具有协同导向作用 ,并对产生这种协同作用进行了讨论。     

Copolymerization of 1-butene and 1-hexene with supported titanium catalyst

With TiCl₄/MgCl₂ (Ti) and Al(i-Bu)₃ (Al) as catalysts, the thermoplastic copolymer of 1-butene(Bt) and 1-hexene(He) was synthesized successfully. The effects of Bt/He, Ti/(He+Bt), Al/Ti, temperature and reaction time on conversion, catalyst efficiency(CE), intrinsic viscosity([η]) and insoluble content were studied. The copolymer was analyzed with Fourier transform-infrared (FTIR) and nuclear magnetic resonance (¹H-NMR). Results showed that the optimal polymerization conditions were: He/Bt = 0.25, temperature 40°C−50°C, Al/Ti = 400−500, Ti/(Bt+He) = 3 × 10⁻⁵ − 4 × 10⁻⁵, time 4 h. Intrinsic viscosity was found to increase with increasing Ti/(Bt+He) and decreasing Al/Ti and polymerization temperature. When the molar content of He, Al/Ti and polymerization temperature increased, the insoluble content in CH₂Cl₂ of copolymers decreased. When Ti/(Bt+He) and reaction time increased, the insoluble content in CH₂Cl₂ of copolymers also increased. The crystallization and stereoregularity of poly(1-butene) decreased with the addition of He. Translated from China Synthetic Rubber Industry, 2006, 29(6): 429–434 [译自: 合成橡胶工业]     

负载钛催化1-己烯聚合

研究了负载钛催化1-己烯(He)聚合的规律,考察了聚合条件对转化率和聚合物性能的影响。结果表明:以MgCl2为载体的负载钛高效催化剂体系催化合成的聚1-己烯(PHe)为高相对分子质量、无定型、透明的弹性体;较适宜的合成条件是Ti/He(摩尔比)为(3～5)×10-5,Al/Ti(摩尔比)为250～300,温度为30℃;氢气压力是调节相对分子质量的有效手段,随着氢气压力的不断增加,聚合物的相对分子质量急剧下降。     

TiCl4／MgCl2-AIEt3体系合成聚1-丁烯

以负载钛体系（简称Ti）为主催化剂,三乙基铝（简称Al为助催化剂,加氢汽油为溶剂,用溶液聚合法合成了聚1-丁烯。研究了n（Ti）／n（Bt）、n（Al）／n（Ti）、反应温度、反应时间对转化率、催化效率、聚合物的特性粘数[η]及其全同立构含量的影响。结果表明,随n（Ti）／n（Bt）增加,转化率和催化效率都不断提高;随n（Al）／n（Ti）增加、反应温度升高,转化率和催化效率呈先上升后下降趋势;随n（Al）／n（Ti）、n（Ti）／n（Bt）增大和反应温度的升高,特性粘数逐渐下降,但其对全同立构含量影响较小。