钛硅分子筛催化剂的研究进展
Research progress of titanium silicalite catalys t
Zhangxiaoming Zhangzhaorong Soujiquan Lishuben
(Lanzhou Institute of Chemical Physics fine petrochemical intermediates National Engineering Research Center, Lanzhou 730000)
The role of titanium catalyst in the oxidation reaction of organic compounds is well known [1, 2]. Introduced in the molecular sieve framework due to the molecular sieve having a regular pore structure and large specific surface area characteristics, hetero atom, having an oxidation-reduction ability to preparenovel catalytic oxidation catalyst, has been more interesting subject in 1983 ENI [3] the T ar amasso its collaborators first successful synthesis of the titanium-containing zeolite catalyst of TS-1, a subsequent study found, Tammonia oxidation [7] S-1 with H2O2 aqueous solution as oxidant and the oxidation reaction of a series of organic compounds, such as olefin epoxidation [4], the aromatic hydrocarbon ring hydroxylation [5, 6], ketone, alkane oxidation[8, 9] and the alcohol oxidation [10] and so the process has a unique shape-selective catalytic function as compared with other types of catalytic systems, the system (1) the mild reaction conditions (atmospheric pressure, 0 - 100 ° C); (2) the unique function of the shape-selective catalytic oxidation; (3) environmental friendliness.
TS-1 has been very limited because the aperture is only about 0. 55 nm, and its range of applications where the aerodynamic diameter is greater than 0.
60 nm substrate molecules can not enter within its pores without reactivity. Orderovercome this limitation, the type of catalyst to get a wider range of applications, the majority of scientists have successfully synthesized T S-2 [11], Ti-Beta [12] and a series of large aperture zeolite catalysts.
In recent years, with the development of the petroleum refining and fine petrochemical technology requires the use of some reorganization of the oil to be effective. M41S [13, 14], HMS [15] and MSU [16] series of mesoporous molecular sieves Tiheteroatom derivatives T i-MCM-41 [17], Ti-MCM-48 [18], Ti-HMS [19, 20] and of Ti-the MSU [16] emerged, the latter in the selective oxidation of organic compoundsshowed higher catalytic activity.
This paper reviews the recent years, the progress made in terms of microporous and mesoporous titanium silicalite catalyst preparation, characterization, and catalytic reaction.
T S-1 is first synthesized, and also so far been studied most, and more thoroughly of a class of titanium silicalite catalyst. T S-1 is a Silicalite-1 isomorphously substituted derivatives thereof, having the MFI structure. TS- work and the results achieved many comments have been reported [10, 21 - 24] here only a brief overview of the TS-1 preparation, characterization, and their corresponding catalytic reaction.
The classical method of preparing a zeolite catalyst is a hydrothermal synthesis method in the the earliest patent literature, Tar amasso [3] reported two preparation T S-1 The method of one is tetraethyl orthosilicate (T EOS) and tetraethylammonium n-titanate (TEOT) as silica source and a titanium source, and tetrapropyl ammonium hydroxide (TPA OH) as templating agent;
other is a silica sol as a silicon source, and to dissolve in H2O2 the titanate as titanium source TPAOH templating agent in addition to the hydrothermal synthesis method, the TS -1 can also be obtained by the method of secondary synthesis TiCl4 and dealumination of ZSM-5 for vapor phase reaction, to give with hydrothermal synthesis method is similar to the structure [25], but this method is easy to cause anatase. Huanxin et al [26] for the titanium source, TEOS as a silicon source, and succeeded in synthesizing a T S-1 to T iCl3 The same catalytic activity, with the same reported in the literature, and the process can be effectively prevented from generation of anatase In addition, Tuel and T aarit, continuous coverage positive ions with phosphorus [27], 1, 6 - hexamethylene diammonium ion (Di -TPA) [28], tetraethyl ammonium hydroxide (TEAOH) / T PAOH and T EAOH / tetrabutyl ammonium hydroxide (T BA OH) [29] as a template to prepare T S-1 process. described using different Preparation of Template T S-1 is likely the. Preparation of Titanium Silicalite reagent over Na +, K + and other alkali metal ions of the concentration should be sufficiently low, because the alkali metal ions will hinder the titanium atom in the molecular sieve framework embedded; another the one hand, to prevent the preparation process difficult to dissolve the anatase anatase formation will lead to subsequent reaction of H2O2 decomposition and reduce the catalytic activity in order to prevent the generation of anatase, the preparation process should be vigorously stirred, so that titanium source in the silicon source is highly fragmented., Thangaraj, [7] the slower rate of hydrolysis the of tetrabutylammonium positive titanate (TBOT) Alternate TEOT, with anhydrous isopropyl alcohol as a co-solvent, and achieved good effect.
TS-1 zeolite catalyst unique shape-selective catalytic oxidation function, undoubtedly has a direct relationship with the skeleton of T i (Ⅳ) Therefore, the focus of such zeolite characterization is to determine the existence of T i (Ⅳ) in the molecular sieveits ligand environment. characterization of TS-1, except for routine characterization of X-ray diffraction (XRD), N2 adsorption / desorption method, Fourier transform infrared spectroscopy (FT-IR) 29Si magic anglespinning nuclear magnetic resonance spectroscopy
(29Si-MAS-NMR), diffuse reflectance UV - visible spectrum (DR UVVis), X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure analysis (XANES) and other technologies exist in the form of tetrahedral coordination T i (Ⅳ) provided the basis for
According to the naming of IUPAC [40], the aperture between 2 - 50 nm molecular sieves for mesoporous molecular sieves. 1990s, class zeolite inorganic materials separation, ion exchange and catalytic disciplines one of the hot to longchain surfactants as templating agent, have been successfully synthesized M41S [13, 14], HMS [15] and MSU [16] and a series of mesoporous molecular sieves. formation mechanism of the pore structure of mesoporous molecular sieve research has been reported[41 - 46] At the same
time, Ti [17 - 20], V [47], Zr [48], Mn [49] and Cr [50] with the redox ability of transition metal atoms into mesoporous molecular sieveskeleton structure, get a lot of new catalysts for the preparation of fine chemicals which T i atom isomorphous substitution in the hole titanium silicalite has important significance of theoretical research and industrial application value.
The Gont ier and T uel [20] also Press T anev to method prepared T
i-HMS, and preparation process of various factors such as the proportion of T iO2 / SiO2, isopropanol, surface active agent chain length, characteristic of the titanium source and of Surf / SiO2 system. found that in the preparation process, when the two reagents is mixed for 15 min, the resulting product had with Hex ago nal various characteristics of most of Surf / SiO2 the best ratio of 0.3 increase this proportion of the aperture increases, but the specific surface area and adsorption capacity is greatly reduced.
Reviewed above on the synthesis, characterization and catalytic oxidation properties of titanium silicalite and mesoporous molecular sieves prepared its heteroatom derivatives can be seen, the titanium silicalite as a new type of selective oxidation catalyst demandis very important to the increasing volume of the preparation of fine chemicals. especially in recent years, the success of a series of mesoporous molecular sieves synthesis and application, making the range of applications greatly broaden the field has attracted more and more attention of researchersbut we should also see that there are still many problems in the field, such as the titanium silicalite catalytic reaction mechanism, the formation mechanism of mesoporous molecular sieves and skeleton in the presence of T i (Ⅳ) way for further exploration of these issuesand research will become a research focus in the coming period.
钛硅分子筛催化剂的研究进展
张小明张兆荣索继栓李树本
( 中国科学院兰州化学物理研究所精细石油化工中间体国家工程研究中心兰州730000) 含钛催化剂在有机化合物氧化反应中的作用是众所周知的[ 1, 2] . 由于分子筛具有规整的孔道结构和较大的比表面积等特点, 在分子筛骨架中引入具有
氧化还原能力的杂原子, 以制备新型的催化氧化催化剂, 一直是人们比较感兴
趣的课题. 1983 年ENI[ 3] 的T ar amasso 及其合作者首次成功地合成了含钛的分子筛催化剂TS-1. 随后的研究发现, T S-1 在以H2O2 水溶液为氧化剂的一系列有机化合物的氧化反应, 如烯烃的环氧化[ 4]、芳烃环的羟基化[ 5, 6] 、酮的氨氧化[ 7] 、烷烃的氧化[ 8, 9] 及醇的氧化[ 10] 等过程中有独特的择形催化功能. 同其他类型的催化体系相比较,该体系有( 1)反应条件温和( 常压, 0- 100℃);( 2) 独特的择形催化氧化功能;( 3)环境友好等优点。
TS-1 由于孔径只有0. 55 nm 左右, 而使其应用范围受到了很大的限制. 凡动力学直径大于0. 60 nm 的底物分子因不能进入其孔道内部而无反应活性. 为了克服这一局限性, 使该类催化剂能得到更为广泛的应用, 广大科研工作者相
继成功地合成了T S-2[ 11] 、Ti-Beta[ 12] 等一系列孔径较大的分子筛催化剂。
近年来, 随着石油炼制及精细石油化工技术的发展, 要求对一些重组分油
加以有效利用. M41S[ 13, 14] 、HMS[ 15] 及MSU[ 16] 等系列中孔分子筛及其Ti 杂原子衍生物T i-MCM-41[ 17] 、Ti-MCM-48[ 18] 、Ti-HMS[ 19, 20] 和
Ti-MSU[ 16] 等应运而生, 后者在有机化合物选择氧化中表现出较高的催化活性。
本文综述了近几年在微孔及中孔钛硅分子筛催化剂的制备、表征及催化反应等方面所取得的进展。
T S-1 是最早合成的、也是迄今为止人们研究得最多且比较彻底的一类钛硅
分子筛催化剂. T S-1 是Silicalite-1 的同晶取代衍生物, 具有MFI 的结构. 关于TS-1 的工作和所取得的成果已经有许多评述见诸报道[ 10, 21- 24] . 这里仅就TS-1的制备、表征及其相应的催化反应等方面作一简要的概述。
制备分子筛催化剂的经典方法是水热合成法. 在最早的专利文献中, Tar amasso 等[ 3] 报道了两种制备T S-1 的方法. 一种是以四乙基正硅酸酯( T EOS) 和四乙基正钛酸酯( TEOT ) 为硅源和钛源, 以四丙基氢氧化铵( TPA OH) 为模
板剂; 另一种是以硅溶胶为硅源, 以溶解于H2O2 中的钛酸酯为钛源, 用TPAOH 做模板剂.除了水热合成法之外, TS -1 也可以通过二次合成的方法得到. 以TiCl4 和脱铝的ZSM-5进行气相反应, 得到了与水热合成法类似的结构[ 25] . 但这种方法易于导致产生锐钛矿.高焕新等人[ 26] 以T iCl3 为钛源, TEOS 为硅源, 成功地合成了T S-1, 具有同文献报道同样的催化活性, 并且该过程可以有效地防止锐钛矿的产生.另外, Tuel 和T aarit 连续报道了用磷正离子
[ 27] 、1, 6-己二铵离子( Di-TPA) [ 28] 、四乙基氢氧化铵( TEAOH) / T PAOH 及T EAOH/ 四丁基氢氧化铵( T BA OH) [ 29] 为模板剂制备T S-1 的过程. 说明用不同的模板剂制备T S-1 是可能的.在钛硅分子筛的制备中, 试剂中Na+ 、K+ 等碱金属离子的浓度应足够低, 因为碱金属离子会阻碍钛原子在分子筛骨架中的嵌入; 另一方面, 要防止制备过程中产生难溶解的锐钛矿.锐钛矿的形成会导致后续反应中H2O2 的分解而降低催化活性. 为了防止锐钛矿的产生, 制备过程中应该激烈搅拌, 使钛源在硅源中高度分散. 另外, Thangaraj 等[ 7] 以水解速度较慢的四丁基正钛酸酯( TBOT ) 替代TEOT , 用无水异丙醇作为共溶剂, 取得了较好的效果。
TS-1 分子筛催化剂独特的择形催化氧化功能, 无疑与骨架中的T i( Ⅳ) 有着直接的关系.因此, 该类分子筛表征的重点在于确定T i( Ⅳ) 在分子筛中的存在方式及其配位环境. 在TS-1 的表征中, 除了用于常规表征的X 射线衍射( XRD) 、N2 吸附/ 脱附等方法外, 付里叶变换红外光谱( FT -IR) 、29Si 魔角旋转核磁共振谱( 29Si-MAS-NMR) 、漫反射紫外-可见光谱( DR UVVis)、X 光电子能谱( XPS ) 、扩展X 射线吸收精细结构分析( EXAFS) 及X 射线吸收近边结构分析( XANES) 等技术, 为以四面体配位形式存在的T i( Ⅳ) 提供了依据。
根据IUPAC[ 40] 的命名规则, 孔径介于2- 50 nm 的分子筛为中孔分子筛.
90 年代, 该类分子筛成为无机材料、分离、离子交换及催化等学科领域的研究热点之一. 以长链表面活性剂为模板剂, 相继成功地合成了M41S[ 13, 14] 、HMS[ 15] 和MSU[ 16] 等一系列中孔分子筛. 关于中孔分子筛孔道结构形成机理的研究已有许多报道[ 41- 46] . 与此同时, 将Ti[ 17- 20] 、V[ 47] 、Zr [ 48] 、Mn[ 49] 和Cr[ 50] 等具有氧化还原能力的过渡金属原子引入中孔分子筛的骨架结构中, 得到了许多可用于制备精细化学品的新型催化剂. 其中T i 原子同晶
取代得到的中孔钛硅分子筛具有重要的理论研究意义和工业应用价值。
Gont ier 和T uel[ 20 ] 也按T anev 的方法制得了T i-HMS, 并对制备过
程中的各种影响因素如T iO2/ SiO2 的比例、异丙醇的作用、表面活性剂链的长
度、钛源的特性及Surf / SiO2 等做了系统的研究. 发现在制备过程中, 当两种
试剂混合15 min 后, 所得产物就已具备Hex ago nal的各种特性. Surf / SiO2 的
最佳比例为0. 3. 增加此比例, 尽管会增大孔径, 但比表面积和吸附能力则大
大降低。
以上对钛硅分子筛的合成、表征及催化氧化性能和中孔分子筛的制备, 及其杂原子衍生物等进行了综述. 从中可以看出, 钛硅分子筛作为一种新型的选择氧化催化剂, 对需求量日益增加的精细化学品的制备是非常重要的. 尤其是近几年一系列中孔分子筛的成功合成和应用, 使得该领域的应用范围大大拓宽, 已经引起越来越多的研究者的关注. 但是我们还应看到, 目前在该领域仍存在许多问题, 如钛硅分子筛催化的反应机理、中孔分子筛的形成机理及骨架中T i( Ⅳ) 的存在方式等. 这些问题的进一步探索和研究将会成为今后一段时期内
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Ti-MWW钛硅分子筛的后处理改性、表征及催化性能
Ti-MWW钛硅分子筛的后处理改性、表征及催化性能 【摘要】：本论文以新一代钛硅分子筛Ti-MWW的后处理改性及催化性能为主线,研究提高Ti-MWW催化活性的新方法,及其液相催化氧化烯烃化合物的催化性能,尤其探索Ti-MWW应用到生产环氧氯丙烷这类大宗化学品的反应过程的可能性。第一部分基于MWW分子筛层状前驱体晶体结构具有可塑性的特点,采用有机硅试剂与Ti-MWW 分子筛前驱体在高温下作用,有机硅烷进入层间,与层间的自由硅羟基发生反应,经过高温焙烧,MWW分子筛前驱体层间脱水缩合被人为阻止,得到了层间为12元环的大孔道分子筛IEZ-Ti-MWW。详细考察了不同Si/Ti比的Ti-MWW层状前驱体、硅烷化试剂用量、硝酸浓度、硅烷化试剂类型等因素的影响。这种大孔道分子筛既保持了MWW 分子筛的基本结构单元,又兼备了反应物易接近的大反应空间结构特点,因此,不论对环状烯烃还是对直链烯烃,都显示出良好的催化性能,尤其对大分子反应物环己烯的环氧化反应表现出很高的转化数(TON)。第二部分,为了提高Ti-MWW的疏水性和催化活性,用胺溶液对具有三维(3D)结构的MWW分子筛进行了后处理改性。当采用哌啶(PI)或者六亚甲基亚胺(HMI)的胺溶液在一定温度下二次晶化的过程中,3D结构材料转向了二维(2D)层状结构,进一步焙烧又将2D层状结构可逆转化到3D晶体结构,而且这种可逆结构转换仅发生在PI或者HMI存在的情况下,而若换成其他胺溶液即使是结构相似的嘧啶或者哌嗪都无法实现。当PI/SiO_2的摩尔比小于0.1在443K条件下处
理一天时,就能将3D结构转向2D层状结构,并且不受母体Si/Ti比的影响。这种结构转化没有改变活性Ti物种的量以及配位状态,但是骨架内部的硅羟基却消除了大约40%,形成了缺陷位少,结构更加“刚性”以及疏水性能良好的Ti-MWW分子筛。在酮类的肟化以及各类不同分子尺寸大小的烯烃环氧化反应中,结构重排的Ti-MWW分子筛都表现出比3DTi-MWW更优异的催化性能。第三部分,通过一种简单的后处理方法制备出含各种杂原子的类似于MCM-56结构的分子筛。酸处理回流MWW层状前驱体形成传统的3D结构材料,但当控制一定的酸处理条件即酸处理温度低于353K时,就形成了MCM-56,并RMCM-56的形成依赖于层状前驱体的晶粒大小,晶粒小有利于前驱体转换形成MCM-56。且MCM-56的形成与前驱体骨架中金属离子类型(包括B,Al,Ti,Ga或者Fe)及其含量无关。与3DTi-MWW相比,含钛MCM-56具有更大的外表面,因此在各类不同分子大小的烯烃以叔丁基过氧化氢为氧化剂的环氧化反应中以及具有更大分子尺寸的脱除轻油中二苯并噻吩的氧化反应中,Ti-MCM-56都表现出优异的催化活性。最后,我们考察了Ti-MWW分子筛在氯丙烯以双氧水为氧化剂环氧化制备环氧氯丙烷过程中的催化活性,并与典型的钛硅分子筛TS-1、Ti-MOR和Ti-Beta进行了比较。采用Ti-MWW分子筛/H_2O_2/乙腈催化体系,通过对环氧氯丙烷合成工艺条件的考察及优化,氯丙烯、双氧水的转化率以及环氧氯丙烷的选择性都能达到99%以上。Ti-MWW的最好溶剂为乙腈或者丙酮,从而有效的抑制了溶剂化开环反应副产物的形成。而最主要副产物之一的3-氯-1,2-丙二醇对
钛硅分子筛的合成研究 1
钛硅分子筛TS-1合成及应用研究 ****学院***0902 *** 摘要:本文重点综述了近年来钛硅分子筛催化材料的合成、改性及其催化应用的研究进展，包括钛硅分子筛( T S-1) 的水热合成方法和同晶取代合成法、钛硅分子筛双氧水体系的应用研究及近年中孔钛硅分子筛的进展. 关键词：钛硅分子筛TS-1；催化氧化；双氧水；合成 The Syntheses and Applications of Titanium Silicalite TS Molecular Sieves Abstract：Recent developments in the synthesis，modification andcatalytic properties of titanium silicalite molecular sieve are reviewed，including the developments in the synthesis of TS-1 with hydrothermal，applicat ions of t itanium silicalite cataly tic ox idation system using hydr ogen pero xide, and research of mesopo rous titanium silicalite mo lecular sieves. 自1983年有专利报道了以TS-1类钛硅分子筛为催化剂、稀双氧水(H 2O 2 质量分 数为30%)为氧化剂催化氧化苯酚同时生产邻、对苯二酚以来,有关分子筛类催化剂的羟基化反应报道甚多,研究得也最为充分。TS-1分子筛的诞生掀起了有机物非均相选择性催化氧化的一场革命,特别是对于在温和条件下,用稀双氧水溶液为氧化剂的选择性氧化具有独特的性能。TS-1分子筛催化剂使反应具有如下显著优点:①反应条件温和,可在常压、低温(20~100℃)下进行;②氧化目的产物收率高,选择性好;③工艺过程简单;④由于使用低浓度过氧化氢作为氧化剂,氧化源安全易得;⑤还原产物为H 2 O,反应体系没有引入杂质,不会造成环境污染。它的成功开发被认为是20世纪80年代沸石催化的里程碑,为研究高选择性的烃类氧化反应、开发绿色工艺奠定了基础。 1. 钛硅分子筛TS-1 水热合成方法 钛硅沸石分子筛是指在沸石分子筛骨架中含有钛原子的一类杂原子分子筛, 现有TS-1、TS-2、TiB、TS-48、ETS-10 等,。T S-1 的合成是由Taramasso等人[１]于1983 年首先报道的, 合成使用硅酸四乙酯( TEOS) 为硅源, 钛酸四乙酯
钛硅分子筛催化剂的研究进展
Research progress of titanium silicalite catalys t Zhangxiaoming Zhangzhaorong Soujiquan Lishuben (Lanzhou Institute of Chemical Physics fine petrochemical intermediates National Engineering Research Center, Lanzhou 730000) The role of titanium catalyst in the oxidation reaction of organic compounds is well known [1, 2]. Introduced in the molecular sieve framework due to the molecular sieve having a regular pore structure and large specific surface area characteristics, hetero atom, having an oxidation-reduction ability to preparenovel catalytic oxidation catalyst, has been more interesting subject in 1983 ENI [3] the T ar amasso its collaborators first successful synthesis of the titanium-containing zeolite catalyst of TS-1, a subsequent study found, Tammonia oxidation [7] S-1 with H2O2 aqueous solution as oxidant and the oxidation reaction of a series of organic compounds, such as olefin epoxidation [4], the aromatic hydrocarbon ring hydroxylation [5, 6], ketone, alkane oxidation[8, 9] and the alcohol oxidation [10] and so the process has a unique shape-selective catalytic function as compared with other types of catalytic systems, the system (1) the mild reaction conditions (atmospheric pressure, 0 - 100 ° C); (2) the unique function of the shape-selective catalytic oxidation; (3) environmental friendliness. TS-1 has been very limited because the aperture is only about 0. 55 nm, and its range of applications where the aerodynamic diameter is greater than 0. 60 nm substrate molecules can not enter within its pores without reactivity. Orderovercome this limitation, the type of catalyst to get a wider range of applications, the majority of scientists have successfully synthesized T S-2 [11], Ti-Beta [12] and a series of large aperture zeolite catalysts. In recent years, with the development of the petroleum refining and fine petrochemical technology requires the use of some reorganization of the oil to be effective. M41S [13, 14], HMS [15] and MSU [16] series of mesoporous molecular sieves Tiheteroatom derivatives T i-MCM-41 [17], Ti-MCM-48 [18], Ti-HMS [19, 20] and of Ti-the MSU [16] emerged, the latter in the selective oxidation of organic compoundsshowed higher catalytic activity. This paper reviews the recent years, the progress made in terms of microporous and mesoporous titanium silicalite catalyst preparation, characterization, and catalytic reaction. T S-1 is first synthesized, and also so far been studied most, and more thoroughly of a class of titanium silicalite catalyst. T S-1 is a Silicalite-1 isomorphously substituted derivatives thereof, having the MFI structure. TS- work and the results achieved many comments have been reported [10, 21 - 24] here only a brief overview of the TS-1 preparation, characterization, and their corresponding catalytic reaction. The classical method of preparing a zeolite catalyst is a hydrothermal synthesis method in the the earliest patent literature, Tar amasso [3] reported two preparation T S-1 The method of one is tetraethyl orthosilicate (T EOS) and tetraethylammonium n-titanate (TEOT) as silica source and a titanium source, and tetrapropyl ammonium hydroxide (TPA OH) as templating agent;
Ti-MWW钛硅分子筛合成新方法及其催化性能的研究
Ti-MWW钛硅分子筛合成新方法及其催化性能的研究 【摘要】：本论文以提高新一代钛硅分子筛Ti-MWW的催化活性,改善Ti-MWW分子筛的工艺流程为目的,开发了两种新合成方法；以扩大Ti-MWW分子筛在有机反应中的应用范围为目的,开展了含有介孔的Ti-MWW分子筛的合成研究,并将其应用于催化大尺寸底物分子的氧化反应；最后探索Ti-MWW分子筛应用到生产吡啶类氮氧化物这类大宗化学品的反应过程的可能性。第一部分采用廉价的无机钛源六氟钛酸(H2TiF6)在水热条件下合成了Ti-MWW分子筛,考察了各种合成条件包括助晶化剂硼酸的用量、模板剂的用量、凝胶组成等因素对产物的影响。与经典有机钛源法相比,无机钛源法节约了60%以上的硼酸,并且得到的Ti-MWW分子筛的物化性质发生了很大的变化。X-射线粉末衍射表明此方法制备的样品在高温焙烧后保留部分层状结构；红外光谱表明分子筛骨架内部的硅羟基减少,即疏水性能增强,并且与杂原子相关的吸收峰位置发生改变。因此,与经典有机钛源法相比,无机钛源法合成的Ti-MWW分子筛对直链烯烃环氧化、环己酮氨肟化等反应都显示出更优异的催化性能；尤其在大分子反应物环己烯的环氧化、甲基吡啶的氧化反应中,反应物的转化率以及目的产物的收率都提高2倍以上。第二部分采用分子筛二次合成法-杂原子液固相置换法,首次合成出无非骨架钛的Ti-MWW分子筛。利用MWW型分子筛骨架构成以及结构可逆转化的特点,以六氟钛酸为钛源进行杂原子置换；在常温常压下向MWW型分子筛骨架引入活性中心Ti物
种,并且利用无机钛源的阴离子最先占据分子筛表面一些空穴位,有效地阻止非骨架Ti物种(260nm处紫外吸收峰)的形成。本部分详细考察了各种合成条件包括置换反应时间、温度、前驱体的种类、前驱体预处理的酸量、钛源的种类、投料配比(Si/Ti)等因素的影响。类似地,以这种简单的方法合成出高钛含量的且拥有12元环大孔道的IEZ-Ti-MWW分子筛。反应评价表明,此方法制备的Ti-MWW分子筛的催化性能远远高于文献所报道的各种方法合成的Ti-MWW。与现有工业化生产工艺不同的是,以此方法合成的Ti-MWW分子筛将无需酸处理过程,就可以直接用于催化反应,从源头上避免产生大量的有害性废水,为合成工艺的简化以及新技术开发打下了坚实的基础。第三部分采用碱性硅溶胶或正硅酸乙酯作为硅源,钛酸四丁酯作为钛源,以蔗糖炭化得到的碳小颗粒为硬模板,在微孔模板剂六氢吡啶的共同作用下,水热合成了含有介孔的Ti-MWW分子筛；并且对具有介孔的Ti-MWW分子筛的催化性能进行了考察。由于介孔孔道的存在,增加了大分子反应物和催化剂活性中心的接触机会,并且改善了扩散性能,含有介孔的Ti-MWW在3-甲基吡啶氧化反应中表现出更高的单位反应活性(TON)。第四部分,我们考察了以过氧化氢为氧化剂,Ti-MWW 分子筛催化氧化吡啶及其衍生物制备吡啶类氮氧化物的过程中的表现,并与典型的钛硅分子筛TS-1、Ti-Beta和Ti-MOR进行了比较。采用Ti-MWW分子筛/H2O2催化体系,在无溶剂条件下,通过对吡啶氮氧化物合成工艺条件的考察与优化,吡啶的转化率以及吡啶氮氧化物的选择性都能达到97%以上。对于催化大尺寸的甲基吡啶分子氧化反应,
钛硅分子筛的结构与物化特性研究进展
钛硅分子筛的结构与物化特性研究进展 于晓东 曹 钢 (北京燕化石油化工股份公司化学品事业部,102501) 对钛硅分子筛的结构和物化特性的研究进行了综述,讨论了金属离子、非骨架TiO 2和表面酸性等对该分子筛的物化特性的影响。 关键词: 钛硅分子筛 特性 表面酸性 收稿日期: 2001-12-17。 作者简介:于晓东,工程师。1992年毕业于华东化工学 院,曾从事异丙苯、乙基苯酚等的工艺开发工作,后就读于母校,获硕士学位,现从事化工工艺开发工作。 钛硅分子筛(TS )由于其良好的催化性能,近年来,一直是分子筛催化剂领域的研究热点。对于该分子筛的合成、应用已有大量文献报道[1～5],但有关它的表面性质方面的报道较少。作者对TS -1的合成、表征及其在苯羟基化中的应用进行了详细的研究[6]。本文从金属离子、非骨架TiO 2和表面酸性等三个方面对该分子筛的结构与物化特性的研究进展进行了综述。1 钛硅分子筛的结构 TS -1是具有MFI 结构的晶体,自首次成功 合成以来,研究者通过F T -IR 、XRD 、XPS 、EX 2 AFS 、Raman 等测试手段(见表1),对其结构特征进行了大量研究。一般认为,TS -1和其它含钛 分子筛中的钛离子均为四价。 XAN ES 和EXAFS 研究表明,骨架钛为完美 的四面体结构[TiO 4],它随机地分布在分子筛骨 架中,Ti —O 键长为0.180～0.181nm 。Ti (IV )进入分子筛骨架改变了单元晶胞参数,如由XRD 获得的TS -1(1.1%Ti )的晶格常数为a =2.011nm 、b =1.992nm 、c =1.339nm ,而单斜晶系Sili 2calite -1和铝的类似物ZSM -5的晶胞常数分别 为a =2.010nm 、b =1.987nm 、c =1.336nm 和 a =2.007nm 、 b =1.992nm 、 c =1.342nm 。https://www.wendangku.net/doc/359078482.html,lini 等[7]研究发现,晶胞常数与骨架钛(而不是非骨架钛)的含量呈线形关系。根据晶格扩展的特点,他们认为TS —1中骨架钛的上限含量为2.5%。 表1 钛硅分子筛的表征方法 表征方法 说 明 X 射线衍射(XRD ) 测定钛硅沸石最基本的方法之一,采用Cuk α靶在2θ=10～500,了解沸石的结晶情况和结构特征。 付里叶变换红外光谱(FT -IR )一般采用kBr 压片法,在波数400～1400cm -1范围扫描,测定分子筛骨架的振动谱图原子吸收光谱/电感耦合等离子体原 子发射光谱(AAS/ICP -AES )用于样品的化学分析,测定沸石中钛和硅的含量。 扫描电子显微镜(SEM ) 用来观察钛硅沸石的结晶形貌,包括晶粒、尺寸及粒度分布等。 差热分析/热重分析(DTA/TGA )用来测定沸石微孔中吸附液体的脱附温度、有机模板剂的分解温度和沸石的热稳定性。紫外-可见光反射光谱(UV -vis ) 用来测定钛硅沸石中钛的配位态和化合价X -光电子光谱(XPS ) 用于表征钛硅沸石中钛的状态及沸石表面组成X -吸附近边结构(XAN ES )/扩展X -吸附精细结构(EXAFS ) 用于测定钛硅沸石中钛离子的局部结构激光拉曼光谱(Raman )测定沸石骨架振动谱图 比表面测定(SSA ) 常用BET 法来测定沸石的比表面积、孔径及其分布 在IR 、Raman 等振动谱图中,钛硅分子筛,(TS -1、TS -2、TS -48、TS -β等)有一共同的 特征吸收峰,即960～970cm -1吸收带。在Sili - 综述 石化技术,2002,9(1):53～55