VPT法制备MCM-22分子筛催化剂颗粒及其烷基化性能

采用汽相法（VPT）制备了以成型干胶颗粒为基体的MCM-22分子筛催化剂.利用XRD、SEM和BET测试技术对所制备催化剂进行了物相表征、形貌观察和织构分析,并以苯和丙烯烷基化合成异丙苯为模型反应,在液-固固定床反应器上对所制备催化剂的性能进行了评价.结果表明：汽相法制备的MCM-22分子筛催化剂不仅具有较好的结晶度和较高的微孔表面积,而且具有更好的晶体生长取向性和更加致密的结构;在烷基化反应中也具有很好的活性、选择性和稳定性,特别是对目的产物异丙苯的选择性明显高于水热法（HTS）合成的催化剂,在异丙苯合成上具有很好的应用前景.     

Combined EXAFS and XRD for the in situ structural elucidation of solid catalysts under operating conditions

Two distinct kinds of experimental arrangement permit X-ray absorption and X-ray diffraction data to be recorded in a combined manner under in situ conditions. Results are shown for the conversion of a copper-zinc hydroxycarbonate precursor to a live water-gas shift catalyst and for a zinc oxide and a zeolite model catalyst heated to ca. 1000 ° C. The short-range and long-range structural changes accompanying the conversion of the zeolite into cordierite are charted at high temperature. EXAFS and XANES data can be recordable both in fluorescence or transmission mode with one of the arrangements, which also permits successive measurements (around more than one absorption edge) within a short space of time.     

Synthesis of acid–base bifunctional CaO/ITQ-2 zeolite catalyst for phosphorylation of dodecanol

A series of acid–base bifunctional CaO/ITQ-2 zeolite catalysts were prepared by introducing calcium into the ITQ-2 zeolite. The catalysts were characterized by X-ray diffraction, FT-IR, NH₃-TPD and CO₂-TPD. The characterization results proved that ITQ-2 zeolite was synthesized by delaminating the MCM-22 zeolite. After modification by CaO, the catalysts could simultaneously have alkaline and acidic sites with little structural change. We then studied the catalytic capabilities of the prepared catalysts in the phosphorylation of dodecanol to di-dodecyl phosphate (DAP). The results show that ITQ-2 catalyst has higher selectivity for DAP than MCM-22. Versus ITQ-2 zeolite, the CaO/ITQ-2 catalysts have excellent acid–base cooperativity. The conversion of phosphoric acid and the selectivity of di-dodecyl phosphate could reach 80.2% and 77.5%, respectively over 3 wt.%CaO/ITQ-2 at optimal conditions. The catalytic activity of CaO/ITQ-2 catalyst could be regenerated by roasting after four times of reusing.     

Isobutane/2-butene alkylation on MCM-22 catalyst. Influence of zeolite structure and acidity on activity and selectivity

The catalytic behavior of the novel MCM-22 zeolite for the continuous alkylation of isobutane with 2-butene has been investigated at a temperature of 50°C, 2.5 MPa total pressure, and a variety of olefin space velocities. At high olefin conversions the MCM-22 zeolite showed a very high initial cracking activity attributable to strong Brønsted acid sites, as well as to the existence of strong diffusional restrictions of the TMP's (formed inside the zeolite) to exit through the channels. At short times on stream (TOS), TMP's account for ca. 40% of the C₈ fraction. The olefin conversion and the cracking activity rapidly decline with TOS, while the alkylate product became richer in dimethylhexenes, indicating a predominance of 2-butene dimerization and a loss of hydrogen transfer activity as the catalyst aged. Moreover, MCM-22 gives less TMP's than large-pore zeolites (USY, beta, mordenite), but more than the mediumpore ZSM-5 at similar 2-butene conversion. The latter catalyst was much more selective for olefin dimerization than for isobutane alkylation, presumably because formation of the bulkier TMP's was strongly impeded in its smaller pores.     

Synthesis of layered MCM-22(P) in the presence of hexamethonium cations and its transformation into EUO- and MWW-type zeolites

Layered MCM-22(P) was synthesized in the presence of hexamethonium (HM) cations. Compared to zeolite EU-1 (EUO-type structure), which crystallizes in similar conditions, its formation is favored at high HM concentrations (HM/SiO₂ ≥ 0.3) and in the absence of Na₂O. HM-containing MCM-22(P) was used as starting material for zeolite formation. Upon hydrothermal treatment, HM-MCM-22(P) transforms into zeolite EU-1 and upon calcination into a MWW-type zeolite. Transformation mechanisms were studied by standard characterization techniques such as XRD, SEM and TEM. Catalytic properties of the MWW-type zeolite obtained from this precursor were evaluated in a m-xylene isomerization reaction. Compared to zeolite MCM-22 prepared with hexamethyleneimine, a higher catalytic activity and an increased isomerization selectivity were observed and discussed.     

Preparation of MgO/MCM-22 catalysts by a novel two-step impregnation and their shape-selective performance in the synthesis of p-xylene

Shape-selective catalysts of MgO/MCM-22 were prepared by a novel two-step impregnation method and evaluated in the catalytic synthesis of p-xylene by alkylation of toluene with dimethyl carbonate. The two-step impregnation process combines the advantages of general impregnation and complexation impregnation for the preparation of metallic-oxide modified zeolite shape-selective catalysts. The coverage of the acidic sites on the external surface of the zeolite and the adjustment of the pore size of the zeolite can be achieved by two-step impregnation. Consequently, significant improvement in selectivity for p-xylene over the MgO/MCM-22 catalyst was realized.     

Selective Deep Catalytic Cracking Process of Hydrocarbon Feedstocks for the Production of Light Olefins: II. Cooperative Effect of Thermal Cracking and Catalytic Reactions Observed in a 1-Zone Reactor

Hybrid catalysts comprising a chromium-based cocatalyst and a silica-rich ZSM-5 zeolite, when doped with lithium, showed quite a high on-stream stability even at a relatively high reaction temperature (735 °C). The cooperative effect of the thermal cracking and the catalytic reactions, and the interactions between the two catalyst components of the hybrid catalyst, resulted in maximum production of light olefins when the hybrid catalyst contained 40 wt% of zeolite. The main chemical links between the thermal cracking (TC) and the catalytic reactions were the conversions of diolefins and large olefins, the latter being produced by the TC and the active sites of the chromium-bearing cocatalyst, respectively.     

Zeolite MCM-22 Supported Heterogeneous Chromium Catalyst for Ethylene Polymerization

The chromium alkyl complex Cp*Cr(py)Me₂ (Cp* = ⁵-pentamethylcyclopentadienyl, py = pyridine, Me = methyl) has been affixed to the surface of zeolite MCM-22 via methane elimination. The resulting composite material has been characterized by a variety of physical methods. The results are consistent with the presence of isolated organometallic fragments linked to the solid support by a covalent chromium–oxygen bond. Activation of this material with methylaluminoxane (MAO) yielded a highly active catalyst for the polymerization of ethylene. The polyethylene thus formed featured high molecular weights (M_w 4 × 10⁶) and narrow molecular weight distributions (M_w/M_n 3.5).     

Cerium ion-exchanged layered MCM-22: preparation,characterization and its application for esterification of fatty acids

A series of cerium ion-exchanged MCM-22 catalysts was prepared by post-synthetic ion-exchange route. The resultant cerium-exchanged MCM-22 zeolite was systematically characterized using FTIR, powder X-ray diffraction (XRD), N₂ adsorption and desorption analysis, scanning electron microscopy, thermogravimetric analysis and diffuse reflectance UV–Vis spectral studies. The XRD pattern and FTIR data confirmed the MCM-22 structure. The diffuse reflectance UV–Vis spectroscopy showed coordination nature of the cerium ions. The cerium exchange MCM-22 zeolite showed promising activity for the esterification of fatty acids, achieving a maximum conversion of 75% at 70 °C in 24 h. Importantly the catalytic activity increases upon recycle due to hydrophic nature of recycled catalyst.     

Preparation self-bonded zeolite MCM-22 bodies by vapor-phase transport method

Self-bonded bodies of zeolite MCM-22 were prepared by vapor-phase transport method. The resultant materials were characterized by means of XRD, SEM, NH₃-TPD, BET, ²⁷Al MAS NMR, Pascal 140 and Pascal 240. It was found that the bodies, prepared by aluminosilicate gel, had been transformed into zeolite MCM-22. The zeolite bodies that were composed of MCM-22 crystal chips avoided binder accession. The total acid sites, the specific surface area, mechanical resistance and the average pore radius of the zeolite bodies reached 1.01 × 10⁻³ mol/g, 486.82 m²/g, 126 N/cm and 57.93 nm, respectively.     

分子筛催化剂上二异丙苯异构化反应

通过筛选5种不同的催化剂，最终确定β沸石分子筛对二异丙苯异构化反应有良好的催化性能。考察了反应温度和空速对异构化反应转化率及选择性的影响，结果表明，170 ℃、3.5 MPa、空速2 h^－1下，β沸石上对二异丙苯的转化率45%，间二异丙苯的选择性69%。对催化剂的稳定性进行了考察，结果表明，在二异丙苯异构化反应中该催化剂表现出良好的稳定性。     

MCM-22 分子筛的合成及液相烷基化合成乙苯性能研究

对各种条件下合成的MCM-22沸石进行了表征研究。研究表明晶化时间对MCM-22沸石的层间结构有着显著的影响,晶化40 h后,其结构趋向稳定。MCM-22沸石沸石具有较高的B酸含量,强酸中心主要为B酸,MCM-22晶体呈片状结构,其结构中存在丰富的大孔。以MCM-22沸石为催化剂考察了其催化乙烯和苯的液相烷基化的反应性能。结果表明,MCM-22沸石催化剂具有优良的选择性,在低苯烯比(B/E)的反应条件下,其反应稳定性优良。在乙烯质量空速达到0.7 h~(-1),苯烯摩尔比(B/E)可以降低到2.0,乙苯选择性达到84%,二甲苯含量小于50 mg/kg。     

Synthesis,characterization and catalytic properties of mesoporous MCM-48 containing zeolite secondary building units

Mesoporous aluminosilicate MCM-48 containing zeolite secondary building units in the pore wall has been synthesized in alkaline media with a two-step procedure. The aluminosilicate precursors comprising zeolite secondary building units were first synthesized by carefully controlling reaction conditions and then were assembled using co-templates of gemini surfactant [C₁₈H₃₇N(CH₃)₂(CH₂)₃-N(CH₃)₂C₁₈H₃₇]²⁺ (18-3-18) and triethanolamine (TEA). X-ray Diffraction (XRD) patterns of the as-made samples indicated that highly ordered mesostructured MCM-48 was formed. Transmission Electron Microscopy (TEM) images further verified the formation of MCM-48 with uniform cubic pore channel system having the pore opening diameter of about 25 ?. Compared with the conventionally synthesized MCM-48, the as-synthesized MCM-48 sample showed an adsorption band at 520–600 cm⁻¹ in its FT-IR spectrum, which was assigned to five-membered ring vibration from zeolite structure. This suggested the presence of zeolite building units in the pore wall. N₂ adsorption data showed that the material had a much higher specific surface area (1 200 m²/g) than the conventional MCM-48(1 100 m²/g). Finally, the catalytic performance of the as-made MCM-48 was evaluated by hydrogenation dealkylation reaction of heavy aromatic hydrocarbons. Catalytic results showed that the as-made MCM-48 catalyst exhibited higher conversion than the conventional MCM-48 catalyst. The as-made mesostructured MCM-48 may have a potential catalytic application in the conversion of bulky molecules. Translated from Journal of Fuel Chemistry and Technology, 2006, 34(1): 105–108 [译自: 燃料化学学报]     

Regulation of isobutane/1-butene adsorption behaviors on the acidic ionic liquids-functionalized MCM-22 zeolite

The adsorption ratio of isobutane/1-butene on the catalyst surface is one of the most important factors for the C4 alkylation process.Regulation of isobutane/1-butene adsorption ratio on the zeolite-supported acid catalyst is a big challenge for catalyst preparation.To regulate the isobutane/1-butene adsorption ratio,four types of ionic liquid (i.e.,IL) with different alkyl chain lengths and different acid group numbers were synthesized and were subsequently immobilized onto the MCM-22 zeolite.The as-synthesized IL-immobilized MCM-22 (i.e.,MCM-22-IL) was characterized by FTIR,TGA,BET,XPS and XRD,and their adsorption capacities and adsorption molar ratios of isobutane to 1-butene (I/O) were investigated to correlate with surface features of MCM-22-IL Results showed that the immobilization of ILs led to a decrease of specific surface area and pore volume.But the surface density of acid groups was increased and the adsorption molar ratio of isobutane/1-butene (I/O) was significantly improved by the immobilization of ionic liquids.The adsorption molar ratio of I/O is substantially improved from 0.75 to above 0.9 at 300 kPa upon immobilizing ILs.Although the alkyl chain length of ILs was found to have little effect on the adsorption molar ratio of I/O,the increase of acid group numbers led to a dramatic decrease in the adsorption I/O ratio.The results illustrated that immobilizing ionic liquids is an effective way to modify the textural,chemical and morphological properties of MCM-22.Accordingly,the immobilization of ionic liquids provides a novel and a feasible way to regulate the adsorption I/O ratio on an adsorbent or a solid catalyst.     

Alkylation of benzene with ethane over platinum-loaded zeolite catalyst

Alkylation of benzene with ethane was carried out using various zeolite catalysts at temperature ranges of 400–550°C. Loading of platinum onto zeolite greatly enhanced the yield of ethylbenzene. Among the zeolites tested, H-ZSM5 and H-MCM22 showed catalytic activities. By contrast, mordenite did not yield ethylbenzene. Moderate acid strength distribution is the key factor of zeolite catalysts. Optimum catalyst and conditions for this reaction are as follows. The platinum-loaded H-ZSM5 catalyst containing 6.8 wt% Pt, at a reaction temperature of 500°C, afforded ethylbenzene and styrene formation rates of 14.2 and 0.8 mmolh^–1g-cat^–1, respectively (benzene-based yields 7.3 and 0.4%). In the alkylation of benzene with ethane over platinum-loaded H-ZSM5, ethene was initially formed from ethane over the metallic platinum. Then the alkylation proceeded over the acid sites of H-ZSM5.     

PEG2000对MCM-22分子筛结构特性和催化性能的影响

以六亚甲基亚胺为模板剂,在动态水热合成MCM-22分子筛的过程中,加入有机辅助剂聚乙二醇2000(PEG2000),考察有机辅助剂PEG2000对MCM-22分子筛结构、酸性以及催化性能的影响。由X射线衍射谱图可以看出,合成时加入适量的PEG2000,可以得到结晶较好的MCM-22晶体,但结晶度稍微有些降低。由氮吸附脱附测试结果可以看出,适量助剂PEG2000的加入,改变了分子筛的最可几孔径分布,最可几孔径由0.556 nm提高至0.587 nm,孔容由0.35 m3/g增加到0.59 m3/g,BET比表面积由410 m2/g增加到456 m2/g。NH3-TPD方法测试样品的酸性结果显示,加入适量的PEG2000后,分子筛的强酸位得到加强。另外用合成的分子筛作为催化剂,以苯与丙烯烷基化为模型反应,考察了MCM-22分子筛的活性以及选择性,结果显示催化剂的活性有较大提高,然而对异丙苯的初始选择性降低,随着反应的进行,异丙苯的选择性却很快地增长。     

Shape-selective alkylation of isopropylnaphthalene on MCM-22 zeolite

An MCM-22 zeolite with an Si/Al ratio 13 was found to exhibit higher selectivity to β,β-diisopropylnaphthalene in the alkylation of isopropylnaphthalene with isopropylalcohol, as compared with other zeolites such as mordenite, Y and beta having similar Si/Al ratios. This high selectivity is ascribed to the specific pore shape of MCM-22 zeolite. The gradual increase in the selectivity with reaction time is due to its pore modification by coke deposit.     

Dimerization of Hexadecene with Acid Mesoporous Silica-Alumina Catalysts

Catalytic dimerization of 1-hexadecene is shown to be a promising path to make high quality base oil. The base oil is produced by hexadecene dimerization with acid mesoporous silica-alumina catalyst, followed by distillation and hydrogenation. The base oil stock had a high viscosity index (typically 140–150) and a low volatility (Noack typically less than 8 %). The best performance in hexadecene dimerization was achieved with the MCM-22 zeolite embedded MCM-41 catalyst within the silica-alumina catalysts compared. Commercial mesoporous silica-alumina catalysts behaved similarly to a non-commercial MCM-41 catalyst. Y-zeolite and ion exchange resin Amberlyst-35 deactivated fast.     

Synthesis,characterization and catalytic properties of mesoporous MCM-48 containing zeolite secondary building units

Mesoporous aluminosilicate MCM-48 containing zeolite secondary building units in the pore wall has been synthesized in alkaline media with a two-step procedure. The aluminosilicate precursors comprising zeolite secondary building units were first synthesized by carefully controlling reaction conditions and then were assembled using cotemplates of gemini surfactant [C₁₈H₃₇N(CH₃)₂(CH₂)₃N(CH₃)₂C₁₈H₃₇]²⁺ (18-3-18) and triethanolamine (TEA). X-ray Diffraction (XRD) patterns of the as-made samples indicated that highly ordered mesostructured MCM-48 was formed. Transmission Electron Microscopy (TEM) images further verified the formation of MCM-48 with uniform cubic pore channel system having the pore opening diameter of about 25 Å. Compared with the conventionally synthesized MCM-48, the as-synthesized MCM-48 sample showed an adsorption band at 520 600 cm^-1 in its FT-IR spectrum, which was assigned to five-membered ring vibration from zeolite structure. This suggested the presence of zeolite building units in the pore wall. N2 adsorption data showed that the material had a much higher specific surface area (1 200 m₂/g) than the conventional MCM-48(1 100 m₂/g). Finally, the catalytic performance of the as-made MCM-48 was evaluated by hydrogenation dealkylation reaction of heavy aromatic hydrocarbons. Catalytic results showed that the as-made MCM-48 catalyst exhibited higher conversion than the conventional MCM-48 catalyst. The as-made mesostructured MCM-48 may have a potential catalytic application in the conversion of bulky molecules.     

动态法合成MCM-22分子筛及其表征

以六亚甲基亚胺(HMI)为模板剂,采用动态水热晶化法合成出MCM—22沸石分子筛。采用XRD表征对其进行物相分析;采用氨脱附—程序升温脱附(NH3—TPD)法表征其酸性质。结果表明:合成过程中易生成混晶,而适宜的SiO2/Al203比和碱度可以合成出比较纯的MCM—22分子筛。采用常规的离子交换方法可以将其转变为氢型样品。