Catalytic transfer dechlorination of chlorobenzene over Pd/SBA-1 mesoporous molecular sieves

New dehalogenation catalysts Pd/SBA-1 mesoporous molecular sieves are synthesized and characterized by N₂ adsorption/desorption, XRD, XPS, FT-IR, DR-UV–vis and AAS. In liquid-phase catalytic transfer hydrogenation of chlorobenzene reaction, low Pd content catalyst Pd/SBA-1 is found to be an efficient catalyst in water/ethanol (2/3) solution of NaOH. The catalyst can easily be recovered and efficiently reused at least three times.     

One-pot synthesis of isobutyl toluene via combined acylation and hydrogenation over Pd–Beta zeolite

The original one-pot synthesis of isobutyl toluene by simultaneous acylation of toluene with acetic anhydride and hydrogenation of the formed isopropyltolyl ketone over Pd–Beta zeolite is described. Zeolite Beta was chosen due to its high acidic activity in toluene acylation with isobutyric anhydride as well as after modification with Pd due to a high activity in hydrogenation of isopropylphenyl ketone to isobutyl benzene. The rate of the formation of isobutyl toluene substantially increases with the hydrophobicity of zeolite Beta despite the “simultaneous” or “consecutive” mode of the experimental setup applied. It is explained by the easier desorption of polar products and faster transport from acid sites to Pd particles, on which the primary formed ketone intermediate is hydrogenated. No effect of hydrogen pressure on the formation of isobutyl toluene was observed, however, with increasing hydrogen pressure hydrogenation of toluene, used as reactant as well as solvent, proceeds at a larger extent.     

介孔分子筛SBA-15在催化领域的应用进展

从负载固体酸催化剂、金属和金属氧化物以及手性催化剂三方面综述了介孔分子筛SBA-15在催化领域应用的研究进展;并展望了介孔分子筛SBA-15在催化领域的研究方向。     

Controlling Reaction Pathways for Alcohol Dehydration and Dehydrogenation over FeSBA-15 Catalysts

The iron location in FeSBA-15 strongly influences the selectivity to dehydrogenation and dehydration in ethanol conversion. At low iron loading, Fe is present as isolated $\hbox{Fe}^{3+}The iron location in FeSBA-15 strongly influences the selectivity to dehydrogenation and dehydration in ethanol conversion. At low iron loading, Fe is present as isolated species in the amorphous silica phase. At higher loading additional aggregated forms of iron oxide exist. Isolated species in the silica matrix imply Br?nsted acidity resulting in selective formation of ethylene, whereas clusters catalyze formation of ethylene and aldehyde.     

Basic catalytic properties of as-synthesized molecular sieves

A series of as-synthesized molecular sieves have been tested and revealed useful as basic catalysts for Knoevenagel condensation under mild conditions. In order to understand the role of the Si/Al ratio, the structure, porosity and template agent, fifteen structures were synthesized and studied in this reaction. Siliceous and large pore molecular sieves showed high conversion levels (97%), while aluminum zeolites, even when containing large amount of organic material, showed distinct activity behavior, which was mainly dependent on the amount of framework silicon. This result, in addition to literature data, indicated that most likely siloxy anions (SiO⁻) are the basic active sites. XPS measurements of these hybrid organic–inorganic catalysts showed that O1s binding energy is influenced by the presence of organic template, leading to the conclusion that they are interacting with framework oxygen, possibly balancing framework anions. Calcined siliceous molecular sieves, which had only silanol groups (SiOH), showed negligible catalytic activity (lower than 2%). As-synthesized siliceous molecular sieves have proven to be useful for basic heterogeneous catalysis, particularly for the synthesis of fine chemicals or for catalytic processes demanding strong basic sites.     

Me-OMS-1s分子筛催化叔丁基过氧化氢分解制备叔丁醇

采用静态水热法合成了Me-OMS-1s(Me=Mg,Co,Ni,Cu)分子筛催化剂,对合成的分子筛进行了X射线衍射和电感耦合等离子体发射光谱表征,并系统考察了反应温度(318~338 K)、反应时间(0.5~6 h)和催化剂用量(1.67~8.33 mg·ml^-1)对Me-OMS-1s催化叔丁基过氧化氢分解制备叔丁醇反应性能的影响。研究结果表明,合成的分子筛均为钡镁锰矿型(todorokite)氧化锰;在选择的多相催化反应条件下,Me-OMS-1s均有催化叔丁基过氧化氢歧化分解的反应活性,反应物叔丁基过氧化氢具有较高的转化率,产物叔丁醇的选择性均为100%。Me-OMS-1s催化叔丁基过氧化氢歧化分解的反应活性顺序为:Cu-OMS-1 > Mg-OMS-1 > Ni-OMS-1 > Co-OMS-1。叔丁基过氧化氢的转化率随反应温度的升高、反应时间的延长和Me-OMS-1s用量的增大而显著增大。     

Zirconocene bis(perfluorooctanesulfonate)s-catalyzed acylation of alcohols, phenols, thiols, and amines under solvent-free conditions

Air-stable zirconocene bis(perfluorooctanesulfonate)s [Cp₂Zr(OPf)₂, OPf = OSO₂C₈F₁₇] showing high Lewis acidity and high thermal stability was prepared by reacting Cp₂ZrCl₂ with AgOPf, and examined as a catalyst for acylation reactions. It was found that in the acetylation of various alcohols, phenols, thiols, and amines by equimolar of acetic anhydride, Cp₂Zr(OPf)₂ exhibits high activity and selectivity to desired products under mild and solvent-free conditions. In the acylation of 2-phenylethanol across various acylating reagents, it also shows good catalytic efficiency. In a test of ten cycles, Cp₂Zr(OPf)₂ shows little loss of activity. The results afford a general and efficient method for the acylation of alcohols, phenols, thiols, and amines using zirconium bis(perfluorooctanesulfonate) as catalyst.     

微孔-中孔复合分子筛的合成研究进展

概述了最近几年引起人们广泛关注的微孔-中孔复合分子筛的合成情况,重点介绍了不同复合模式的微孔-中孔复合分子筛的合成方法,包括单模板剂法、双模板剂法、附晶生长法、孔壁晶化法、碱处理法、微孔沸石硅源法等一系列方法,分析了各种合成方法的优点。从目前已取得的研究结果看,附晶生长法和碱处理法值得进一步关注。     

Oxidative dehydrogenation of ethane with carbon dioxide over silica molecular sieves supported chromium oxides:Pore size effect

SBA-15 with varied pore size from 4 to 8 nm were synthesized by tuning the temperature of hydrothermal treat-ment,the supports were then used to load the active phase CrOx through a conventional impregnation method.The resulting catalysts were characterized by small/wide angle XRD,N2 adsorption/desorption,FT-IR,TEM-EDX,XPS,TPR and CO2-TPD to study the feature of structure,surface chemical state,redox and basicity.It was found from these results that the metal species could be well dispersed on catalysts with larger pore size.Cr6+species could enter into the framework by substituting the Si atoms of SBA-15,and Cr3+mainly exist on extra frame-work Pore size had profound effects on reducibility,surface composition and basicity.Cr6+species were neces-sary to activate the C-H bonds of alkanes,while the basicity played an important role in activating C-O bonds of CO2.The best performances were achieved over the sample Cr supported on SBA-15 with a pore diameter of 7 nm in oxidative dehydrogenation of ethane in the presence of CO2.     

The skeletal isomerization of 1-butene over Zn-silicoaluminophosphate molecular sieves

Oxidative dehydrogenation of propane was studied over MgMoO₄-MoO₃ catalysts with a wt% of MoO₃ varying from 0 to 100. The samples were characterized by XRD, EPR, DTA, laser Raman, and BET. The catalytic behavior of the mechanical mixtures was quite different from that of pure phases. These differences were discussed in terms of possible synergy effects between the phases. Propane conversion and selectivity to propene were closely related to the change in redox properties of the catalysts due to the appearance of Mo⁵⁺ ions.     

不同类型分子筛催化剂上香兰素丙二醇缩醛的合成

以香兰素和1,2－丙二醇为原料,HZSM－5、HY、USY、HB、HMCM－22和HMCM－41不同类型分子筛为催化剂,催化合成了香兰素1,2－丙二醇缩醛。对上述分子筛进行了N2吸附—脱附、吸附吡啶的FT－IR表征。结果表明,HMCM－22分子筛具有最高的活性,各种分子筛活性顺序为：HMCM－22〉H13〉USY〉HY〉HZSM－5〉HMCM－41。HMCM－22分子筛具有最高的催化活性,因为它具有最大的二次孔的体积和适宜的酸性。     

Vapour phase esterification of butyric acid with 1-pentanol over Al-MCM-41 mesoporous molecular sieves

Al-MCM-41 molecular sieves with Si/Al ratios 25, 50, 75 & 100 were synthesized hydrothermally and characterized systematically by various analytical and spectroscopy techniques. Their catalytic activity was evaluated for the vapour phase reaction of butyric acid with 1-pentanol. Pentyl butyrate was obtained as the only product. Reaction parameters such as temperature, molar ratio and feed rate were optimized for higher butyric acid conversion. The time-on-stream study was carried out at optimum conditions resulting in gradual decrease in the activity of the catalyst.     

分子筛SBA-15对有机气体的吸附-脱附性能

以聚乙二醇-聚丙三醇-聚乙二醇为模板剂,正硅酸乙酯为硅源,在不同晶化温度下制备了比表面积和晶化不同的SBA-15介孔分子筛,用穿透曲线和程序升温脱附考察了分子筛对甲苯和乙酸乙酯的吸脱附性能。实验结果表明,随着晶化温度从80 ℃升高到135 ℃,SBA-15分子筛对有机气体吸附量减少,脱附温度降低。通过比较发现,分子筛对甲苯的吸附容量比对乙酸乙酯的吸附容量小,SBA-15分子筛呈现亲乙酸乙酯和憎甲苯的性能。     

Thermosensitivity control of polyethlyenimine by simple acylation

Branched polyethylenimine (b-PEI), an amine-rich polymer, can obtain thermosensitivity by a simple acylation reaction. The resulting N-acylated b-PEI derivatives showed a similar lower critical solution temperature (LCST) transition as their linear correspondent, poly(N-alkyloxazoline). Three acyl groups (propionyl, and isobutyryl, and n-butyryl) were introduced and resulted in LCSTs ranging from 10 °C to 90 °C depending on the structure and environment. The hydrophobicity of N-acylated b-PEI can be controlled by varying the acyl group and degree of acylation. Because the LCST transition is determined by the delicate balance between the hydrophobicity and hydrophilicity of the polymers, an increase of the hydrophobicity in N-acylated b-PEI lowers the transition temperature. Also, N-acylated b-PEI contains tertiary amines as well as unacylated primary or secondary amines which can be protonated during acidification from a pH of 7.4 to a pH of 5.5. The LCST transition was observed at elevated temperatures due to the increase of hydrophilicity by the protonation in the acidic environment. The LCST was also influenced by the salt concentration. A decrease of the LCST was observed as the NaCl concentration increased, probably due to the dominance of the salting-out effect. The very simple introduction of thermosensitivity into pre-existing polymers can be easily applied for the development of various dual or multiple signal-sensitive polymer systems.     

Methylation of 2-naphthol over molecular sieves

The mesoporous molecular sieves of the type MCM-41 with different pore openings (40, 64 and 80 Å) were used as catalysts in the gas-phase methylation of 2-naphthol by methanol at 473 K. Their catalytic activity was compared with that of BEA, SAPO-5 and SAPO-11. The molar ratio of 2-naphthol : methanol was varied from 1 : 4 to 1 : 6. The alkylation of the hydroxyl group (O-alkylation) as well as of the aromatic ring (C-alkylation) proceeded. The best yield of 2-methoxynaphthalene was achieved using MCM-41 40 Å and molar ratio 2-naphthol : methanol = 1 : 6.     

Synthesis of highly ordered mesoporous P63/mmc and p6mm phases by adding alcohols to the system for the SBA-1 synthesis

The influence of acidity, alkyl chain length of alcohols, synthesis temperature and time on the molecular sieve synthesis by adding alcohols to the system for the SBA-1 synthesis were studied. Upon increasing the concentration of alcohols (C_mH_2m+1OH) in the mixture of tetraethyl orthosilicate (TEOS), cetyltriethylammonium bromide (CTEABr), HCl and H₂O, highly ordered P6₃/mmc and p6mm phases were formed when m = 2 and 3 ≤ m ≤ 6, respectively. The amount of HCl was an important factor for the phase-selection under acidic conditions.     

酞菁铜/介孔分子筛复合催化剂催化氧化巯基乙醇的研究

采用浸渍法将α-八-(异戊氧基)酞菁铜分别负载在SBA-15和MCM-41介孔分子筛上,制备了CuPc/SBA-15和CuPc/MCM-412种复合催化剂。通过紫外-可见吸收光谱、红外光谱和N2吸附方法对催化剂的结构和组成进行了表征。测试了2种催化剂对巯基乙醇的催化氧化性能,并考察了温度对催化氧化活性的影响。实验结果表明,在pH=11时,CuPc/SBA-15催化氧化巯基乙醇的转化率高于CuPc/MCM-41;随着温度的升高,CuPc/SBA-15对巯基乙醇的转化率逐渐增大,并计算了CuPc/SBA-15催化反应在25℃时的活化能Ea为30.50kJ/mol。     

Synthesis of highly stabilized mesoporous molecular sieves using natural clay as raw material

Mesoporous molecular sieves were hydrothermally synthesized from natural clay and sodium silicate by using cetyl trimethyl ammonium bromide (CTAB) as a template. The samples were characterized by means of XRD, TEM, TPR, FT-IR and N₂ physical adsorption. The results show that well-ordered and highly stabilized mesoporous molecular sieves were obtained by adjusting the proportion of raw materials. The pore structure of the as prepared mesoporous molecular sieves was not damaged after calcination at 850 °C for 3 h or hydrothermal treatment at 100 °C for 10 days. The mesoporous ordering became better after hydrothermal treatment, but the pore shrank and the surface area decreased after thermal treatment. The stability of the as prepared mesoporous molecular sieves depends on the stability of the clay present in mesoporous pore walls. The presence of clay in the walls can be certified by the regular pore channel images as determined by TEM and XRD analyses.     

添加剂对介孔分子筛AlPO_4结构的影响

采用聚乙二醇为添加剂,十六烷基三甲基溴化铵为模板剂,异丙醇铝为铝源和磷酸为磷源,在水热条件下合成了介孔AlPO4分子筛.XRD和TEM结果表明,PEG的引入可得到六方介孔AlPO4分子筛;FT-IR分析表明.添加剂的引入并没使模板剂的脱除变得困难,MAS-NMR结果表明介孔Al-PO4骨架中不含有AlO6结构和Al2O3等杂相化含物.根据高聚物在水溶液中的性质和相似相容原理.提出了添加剂PEG的作用机理.     

Catalytic hydroxylation of benzene over vanadium-containing molecular sieves

Vanadium-containing molecular sieves with mesopore structures such as MCM-41 and MCM-48, and micropore structures such as BEA and MFI were synthesized by hydrothermal method. XRD, FT-IR, UV–Vis DRS, EPR and XANES were used to characterize their structure, electronic states, and active sites of vanadium species. All the vanadium containing molecular sieves exhibit a pre-edge peak in the V K-edge XANES. The charge transfer transition bands appear at 250 and 340 nm are attributed to the [V^V=O]³⁺ species in the tetrahedral framework position and in the surface wall, respectively. Upon calcining the as-synthesized vanadium-containing samples in the air, V^IV species are oxidized to V^V which is EPR silent. V^V is reduced reversibly by dehydration at 723 K. As for catalytic hydroxylation of benzene, V-MCM-41 shows the highest activity where the turnover number is 64 h⁻¹ at 343 K. Under the higher temperature and the higher acidic conditions, respectively, the catalytic activity is enhanced.