Room temperature efficacious synthesis of diphenylmethane over Fe/Al-MCM-41 catalysts

Fe/Al-MCM-41 (Si/Al = 25, 50, 75 and 100) were synthesized. Their catalytic activity was evaluated towards benzylation of benzene with benzyl chloride in liquid phase. The catalytic activity of Fe/Al-MCM-41(25) was higher than the other catalysts. Diphenylmethane(DPM) was obtained as the major product with 100% selectivity and with 100% conversion of benzyl chloride under optimum condition. The effect of temperature and the feed ratio, on the activity of Fe/Al-MCM-41(25) and selectivity towards DPM was studied and a possible reaction mechanism was proposed.     

Activation of ethyl acetate over metal substituted MCM-41: application to alkylation and acylation

Al-MCM-41, Fe,Al-MCM-41 and Zn,Al-MCM-41 materials with different silicon to metal ratios were synthesized hydrothermally and characterized by XRD, BET, FT-IR, Acidity measurement by pyridine adsorbed FT-IR spectroscopy, ²⁹Si and ²⁷Al MAS NMR and ESR techniques. The orderly arrangement of mesoporous materials was clearly revealed from the XRD patterns. ²⁹Si and ²⁷Al MAS NMR established the co-ordination environment of silicon and aluminium. Electron paramagnetic resonance (EPR) study confirmed the co-ordination environment of Fe in Fe,Al-MCM-41 framework. The catalytic activity of these materials was evaluated in the vapour phase alkylation and acylation of ethylbenzene with ethyl acetate in the temperature range between 250 and 400 °C. The products were found to be 1,3-diethylbenzene (1,3-DEB), 1,4-diethylbenzene (1,4-DEB), 1,2-diethylbenzene (1,2-DEB), 4-ethylacetophenone (4-EAP) and acetophenone (AP). The reaction products revealed that activation of ethyl acetate is a convenient route for both alkylation and acylation reactions. The order of the catalysts activity for the reaction is found to be Fe,Al-MCM-41 (50) > Fe,Al-MCM-41 (100) > Zn,Al-MCM-41 (50) > Zn,Al-MCM-41 (100) > Al-MCM-41 (50) > Al-MCM-41 (100). In addition to the density of acid sites, the strength of acid sites is also important for this reaction. The effects of temperature, feed ratio, WHSV and time on stream were also examined and the results are discussed.     

Photophysical properties of a naphthalimide derivative encapsulated within Si-MCM-41, Ce-MCM-41 and Al-MCM-41

4-Piperazinyl-N-methyl-1,8-naphthalimide (PMN) was synthesized and encapsulated into mesoporous molecular sieves. The fluorescent emission spectra and fluorescence decay of PMN/M-MCM-41 (where M = Si, Ce, Al) were used to investigate the photophysical properties of the hybrid composites. The emission intensity of 4-piperazinyl-N-methyl-1,8-naphthalimide can be increased by decreasing the pH environment of the hybrid composites; the emission intensity varied with different MCM-41 hosts in the order: PMN/Al-MCM-41 > PMN/Si-MCM-41 > PMN/Ce-MCM-41; the fluorescence lifetime of PMN molecules followed the same order. The reasons for the improved fluorescence intensity and the prolonged lifetime of PMN in a low pH environment and Al-MCM-41 are discussed.     

Transesterification of diethyl malonate with n-butanol over HPWA/MCM-41 molecular sieves

Mesoporous Si-MCM-41 and Al-MCM-41 (Si/Al = 100) materials were synthesized via a hydrothermal method. Three different ratios (10, 20 and 30 wt%) of heteropoly tungstic acid (HPWA) was loaded on Si-MCM-41 by wet impregnation techniques. The characteristic structural features of the prepared materials were studied by various physico-chemical techniques such as X-ray diffraction (XRD), Nitrogen physisorption (BET), temperature programmed desorption of ammonia (TPD) and transmission electron microscopy (TEM). Transesterification of diethyl malonate (DEM) with n-butanol under autogeneous conditions in a temperature range from 50 to 125 °C was selected as the test reaction for the as synthesized materials. The reactants were fed with various mole ratios in order to determine the optimal feed composition leading to maximum yields of transesterified products. The results indicated that the conversion of diethylmalonate depends on the HPWA concentration on the support, temperature, reaction time and mole ratio of the reactants. Further, the catalytic efficiency of HPWA/MCM-41 was compared with that of Al-MCM-41. The solid acid HPWA/MCM-41 catalysts have several advantages in comparison to conventional mineral acid catalysts which are heterogeneous, eco-friendly, highly active and selective in the formation of transesters.     

Removal of citric acid from aqueous solution by catalytic wet peroxidation using effective mesoporous Fe‐MCM‐41 molecular sieves

The presence of citric acid in decontamination waste can cause complexation of radioactive cations, resulting in interferences in their removal by various treatment processes such as chemical precipitation and ion exchange, and may pose a potential danger to the environment. Mesoporous Fe‐MCM‐41 molecular sieves (Si/Fe = 25, 50, 75 and 100) were synthesized hydrothermally and characterized by X‐ray diffraction, N₂ adsorption studies, diffuse reflectance UV‐visible spectroscopy, electron paramagnetic resonance and transmission electron microscopy to evaluate the removal of citric acid from aqueous solution by the wet peroxidation method. The effect of time, pH, Si/Fe ratios of Fe‐MCM‐41 and temperature has been studied to achieve efficient removal of citric acid from the aqueous solution. Unlike homogeneous Fe³⁺ catalysis, more mineralization of citric acid was achieved by heterogeneous catalysis with Fe‐MCM‐41 with the percentage removal of total organic carbon of citric acid following the order Fe‐MCM‐41 (Si/Fe = 25) > Fe‐MCM‐41 (Si/Fe = 50) > Fe‐MCM‐41 (Si/Fe = 75) > Fe‐MCM‐41 (Si/Al = 100). Moreover, it was also observed that during the reaction only a minimum amount of iron is leaching from Fe‐MCM‐41. Copyright © 2007 Society of Chemical Industry     

Photocatalytic Disinfection of Escherichia coli over Titanium (IV) Oxide Supported on Hβ Zeolite

Fe loaded Al-MCM-41, (Si/Al = 25, 50, 75 and 100) catalysts were synthesized by hydrothermal method and characterized by the XRD, BET (surface area), FT-IR, and UV- vis and Mössbauer techniques. The liquid phase hydroxylation of phenol with hydrogen peroxide was studied and exclusive formation of dihydroxybenzene was observed. The phenol conversion was found to be almost same at various reaction temperatures viz 40, 60 and 80 °C, but at room temperature only about 30% conversion was recorded. The activity followed the order Fe/Al-MCM-41 (25) > Fe/Al-MCM-41(50) > Fe/Al-MCM-41 (75) > Fe/Al-MCM-41 (100) which was also the order of acidity. Effects of Fe content in Fe/Al-MCM-41 catalysts, solvent, phenol/H₂O₂ mole ratio on phenol conversion was examined. The reaction was also carried out over 10% iron loaded mordenite and the results are compared.     

Hybrid zeolitic-mesostructured materials as supports of metallocene polymerization catalysts

The potential application of hybrid ZSM-5/Al-MCM-41 zeolitic-mesostructured materials as supports of metallocene polymerization catalysts has been investigated and compared with the behaviour of standard mesoporous Al-MCM-41 and microporous ZSM-5 samples. Hybrid zeolitic-mesostructured solids were prepared from zeolite seeds obtained with different Si/Al molar ratios (15, 30 and 60), which were assembled around cetyltrimethylammonium bromide (CTAB) micelles to obtain hybrid materials having a combination of both zeolitic and mesostructured features. (nBuCp)₂ZrCl₂/MAO catalytic system was impregnated onto the above mentioned solid supports and tested in ethylene polymerization at 70 °C and 5 bar of ethylene pressure. Supports and heterogeneous catalysts were characterized by X-ray powder diffraction, nitrogen adsorption-desorption isotherms at 77 K, transmission electron microscopy, ²⁷Al-MAS-NMR, ICP-atomic emission spectroscopy and UV-vis spectroscopy.Catalysts supported over hybrid ZSM-5/Al-MCM-41 (Si/Al = 30-60) exhibited the best catalytic activity followed by those supported on Al-MCM-41 (Si/Al = 30-60). However, catalyst supported on ZSM-5 gave lower polymerization activity because of its microporous structure with narrower pores and lower textural properties than hybrid and mesoporous materials.Although higher acid site population shown by hybrid materials could contribute to the stabilization of the metallocene system on the support, in this case their better catalytic performance is mainly ascribed to the larger textural properties.     

Efficient catalysis of mesoporous Al-MCM-41 for Mukaiyama aldol reactions

Mesoporous aluminosilicates, Al-MCM-41 (Si/Al = 20 and 50), efficiently catalyzed Mukaiyama aldol reaction of benzaldehyde with 1-(trimethylsiloxy)cyclohexene in CH₂Cl₂ at 0 °C to afford the corresponding β-trimethylsiloxy ketone in quantitative yield. On the other hand, mesoporous silica (MCM-41), amorphous SiO₂–Al₂O₃, and H–Y and H-ZSM-5 zeolites barely catalyzed the reaction. Additionally, the less ordered Al-MCM-41 prepared by mechanical compression exhibited much lower catalytic activity compared with Al-MCM-41, indicating that the presence of the ordered mesoporous structure in aluminosilicates is crucial for the catalysis. The Al-MCM-41 catalyzed Mukaiyama aldol reaction was applicable to a wide range of aldehydes and silyl enol ethers. Furthermore, the Al-MCM-41 catalyst could be recycled at least three times without any loss in the yield. Thus, mesoporous aluminosilicates are promising heterogeneous catalysts for fine chemicals synthesis.     

Efficient catalysis of mesoporous Al-MCM-41 for Mukaiyama aldol reactions

Mesoporous aluminosilicates, Al-MCM-41 (Si/Al = 20 and 50), efficiently catalyzed Mukaiyama aldol reaction of benzaldehyde with 1-(trimethylsiloxy)cyclohexene in CH₂Cl₂ at 0 °C to afford the corresponding β-trimethylsiloxy ketone in quantitative yield. On the other hand, mesoporous silica (MCM-41), amorphous SiO₂–Al₂O₃, and H–Y and H-ZSM-5 zeolites barely catalyzed the reaction. Additionally, the less ordered Al-MCM-41 prepared by mechanical compression exhibited much lower catalytic activity compared with Al-MCM-41, indicating that the presence of the ordered mesoporous structure in aluminosilicates is crucial for the catalysis. The Al-MCM-41 catalyzed Mukaiyama aldol reaction was applicable to a wide range of aldehydes and silyl enol ethers. Furthermore, the Al-MCM-41 catalyst could be recycled at least three times without any loss in the yield. Thus, mesoporous aluminosilicates are promising heterogeneous catalysts for fine chemicals synthesis.     

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.     

Characterization and catalytic performance of mesoporous molecular sieves Al-MCM-41 materials

Mesoporous Al-MCM-41 materials of different Si/Al ratios have been synthesized and characterized by X-ray powder diffraction, ²⁷Al and ²⁹Si MAS NMR, differential thermogravimetric analysis, N₂ adsorption measurements, FT-IR and catalytic cracking of alkanes. The experimental results show that the incorporation of aluminium into the framework of MCM-41 has a great effect on the degree of long-distance order, the surface acidities and the mesoporous structures of the materials. With increase of the aluminium content, the amounts of tetrahedral framework aluminium and the acid sites on the samples increase, but the acid strength decreases. Al-MCM-41 materials exhibit high activity for n-C₁₆ ⁰ cracking and good selectivity for producing low carbon alkylenes, particularly for i-C₄ ⁼.     

Mesoporous molecular sieves: alkylation of anisole using tert-butylalcohol

Mesoporous aluninosilicate Al-MCM-41 molecular sieves with Si/Al ratios 25, 50, 75 and 100 have been synthesized under hydrothermal condition and these materials were characterized by XRD, FTIR, BET and pyridine adsorption techniques. The catalytic performance was examined in the vapor phase tert-butylation of anisole with tert-butanol at the temperatures between 150 and 250 °C under atmospheric pressure. The results indicate that Al-MCM-41 (25) was found to be more active than its relatives. The major products are found to be 4-tert-butyl anisole (4-TBA), 2-tert-butyl anisole (2-TBA) and 2,4 di-tert-butyl-anisole (2,4-DTBA). Maximum conversion of anisole is observed at 175 °C and decreased thereafter with increasing temperature. The influence of molar feed ratio, influence of temperature, WHSV and time on stream on the selectivity of products was investigated and the results are discussed.     

Catalytic performance of metal ion doped MCM-41 for methanol dehydration to dimethyl ether

Metal ion doped MCM-41 mesoporous molecular sieves (M-MCM-41, M = Al, Ga, Sn, Zr and Fe) were prepared using a hydrothermal synthesis method, with metal chlorides serving as the dopant sources. The M-MCM-41 structures were characterized by Fourier transform infrared spectroscopic (FTIR) analysis, X-ray diffraction, energy dispersive spectroscopy and N₂ adsorption–desorption measurement. The surface of M-MCM-41 acidities were determined by NH₃ temperature-programmed desorption and pyridine-adsorption FTIR analysis, and their catalytic performance for methanol dehydration to dimethyl ether (DME) was evaluated. The results showed that the prepared M-MCM-41, which exhibited a structure similar to that of MCM-41 with long-range ordered mesoporous structure, contained weak acidic sites. The number of weak acid sites in Al-MCM-41 increased as the Al content increased. The Al content in Al-MCM-41 had an important effect on its catalytic performance, where the highest catalytic activity was 80 and 100 % DME selectivity was achieved at a Si/Al molar ratio of 10. For MCM-41 doped with various types of metal ions, M-MCM-41 (M = Al, Ga, Sn and Zr) also presented a similar wide distribution of acidity, and their catalytic activities were ranked in the following order: Al-MCM-41 > Ga-MCM-41 > Zr-MCM-41 > Fe-MCM-41 > Sn-MCM-41, which were related to the coordination of the metal ions.     

Production of biodiesel by esterification of palmitic acid over mesoporous aluminosilicate Al-MCM-41

Biodiesel has been obtained by esterification of palmitic acid with methanol, ethanol and isopropanol in the presence of Al-MCM-41 mesoporous molecular sieves with Si/Al ratios of 8, 16 and 32. The catalytic acids were synthesized at room temperature and characterized by atomic absorption spectrometry (AAS), thermal analysis (TG/DTA), X-ray diffraction (XRD), nitrogen absorption (BET/BJH), infrared spectroscopy (IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The reaction was carried out at 130 °C whilst stirring at 500 rpm, with an alcohol/acid molar ratio of 60 and 0.6 wt% catalyst for 2 h. The alcohol reactivity follows the order methanol > ethanol > isopropanol. The catalyst Al-MCM-41 with ratio Si/Al = 8 produced the largest conversion values for the alcohols studied. The data followed a rather satisfactory approximation to first-order kinetics.     

The catalytic performance for LDPE destruction over aluminum-incorporated mesoporous silicates

The aim of this study was to investigate the aluminum-incorporated mesoporous silicate (Al-MPS) as a thermal catalyst for the destruction of low density polyethylene (LDPE). Various Al-MPS (Si/Al molar ratios = 117.6, 58.8, 39.2 and 29.4) materials were successfully synthesized without any structural damage. With regard to the X-ray diffraction (XRD) pattern, the main peak of 2θ = 64.0 in Al₂O₃ did not show until the incorporation of Si/Al = 58.8. This result implies the aluminum ions were stably substituted into the silicon site of the mesoporous framework. The hexagonal straight pore size increased to about 8.0 nm in Al (Si/Al = 58.8)-MPS, but then decreased in the range of 3.0–5.0 nm in Al (Si/Al = 29.4)-MPS. In relation to the amount of incorporated aluminum, the Al-MPS absorbed many pyridine molecules, implying the acidities on the external surfaces up to Si/Al = 58.8, but this amount decreased somewhat above a Si/Al ratio of 39.2. The catalytic decomposition of LDPE was enhanced in Al (Si/Al = 58.8)-MPS and particularly, the selectivity to light hydrocarbons below C₄ reached 43%.     

Pyrolysis of biomass in the presence of Al-MCM-41 type catalysts

Al-MCM-41 type mesoporous catalysts were used for converting the pyrolysis vapours of spruce wood in order to obtain better bio-oil properties. Four Al-MCM-41 type catalysts with a Si/Al ratio of 20 were tested. The catalytic properties of Al-MCM-41 catalyst were modified by pore enlargement that allows the processing of larger molecules and by introduction of Cu cations into the structure.Spruce wood pyrolysis at 500 °C was performed and the products were analysed with the help of on-line pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). In addition, thermogravimetry/mass spectrometry (TG/MS) experiments were applied for monitoring the product evolution under slow heating conditions (20 °C/min) from 50 to 800 °C.Levoglucosan is completely eliminated, while acetic acid, furfural and furanes become quite important among cellulose pyrolysis products over the unmodified Al-MCM-41 catalyst. The dominance of phenolic compounds of higher molecular mass is strongly cut back among the lignin products. Both the increase of the yield of acetic acid and furan and the decrease of large methoxyphenols are repressed to some extent over catalysts with enlarged pores. The Cu modified catalyst performed similarly to the catalyst with enlarged pore size in converting the pyrolysis vapours of wood, although its pore size was similar to the unmodified Al-MCM-41.     

Structure and catalytic activity of Al-MCM-48 materials synthesised at room temperature: Influence of the aluminium source and calcination conditions

MCM-48 aluminosilicates with different aluminium contents were synthesised by a room temperature procedure using tetraethoxysilane and aluminium sulfate, isopropoxide or tert-butoxide as metal sources. The samples were characterised by X-ray diffraction, nitrogen adsorption at 77 K, and ²⁷Al MAS NMR and the catalytic activity tested in the reaction of 1-butene double bond position isomerisation. The influence of the synthesis time and calcination conditions, such as heating rate and time at final temperature, on the structural and catalytic properties of the materials was also evaluated. Aluminium isopropoxide and sulfate allowed the preparation of well structured Al-MCM-48 materials, with high specific pore volume and uniform pore size, and with the majority of the aluminium incorporated in tetracoordinated environment after calcination, at least down to Si/Al of 15. The highest initial conversions were found for samples with Si/Al = 20 and 30 prepared with aluminium isopropoxide and calcined using a heating rate of 3 K min⁻¹, with those of samples prepared with aluminium sulfate being slightly lower. Al-MCM-48 materials with high specific pore volume and uniform size were also synthesised using aluminium tert-butoxide, but the materials were less well ordered, presented a higher proportion of hexa- and pentacoordinated Al species and exhibited lower initial conversions, independently of the synthesis time or calcination conditions tested. It is concluded that aluminium isopropoxide and sulfate are more adequate metal sources than aluminium tert-butoxide to prepare Al-MCM-48 catalysts by this room temperature method and a calcination heating rate of 3 K min⁻¹ instead of 1 K min⁻¹ produces more effectively active catalysts.     

t-Butylation of p-cresol with t-butyl alcohol over mesoporous Al-MCM-41 molecular sieves

Selective liquid-phase t-butylation of p-cresol with t-butyl alcohol (t-BuOH) to produce 2-t-butyl-p-cresol (TBC) has been conducted over Al-MCM-41 catalysts with different Si/Al ratios. The effects of various reaction parameters such as temperature, reaction time and n_t-BuOH:n_p-cresol ratio on the conversion of p-cresol and the selectivity of TBC have been systematically investigated as well. When the Si/Al ratio of Al-MCM-41 catalysts is increased from 21 to 104 (respectively yielding Al-MCM-41(21), Al-MCM-41(42), Al-MCM-41(62), Al-MCM-41(83) and Al-MCM-41(104)), both the conversion of p-cresol and the yield and selectivity of TBC decrease due to the decrease of the number of Brønsted acid sites of the Al-MCM-41 catalysts. Al-MCM-41(21) catalyst is found to give the highest conversion of p-cresol (88.2%) and the highest selectivity of TBC (90.40%) under the optimal n_t-BuOH:n_p-cresol mole ratio of 2:1, the optimal reaction temperature of 90 °C and the optimal reaction time of 2 h. Furthermore, Al-MCM-41(21) can be recycled up to at least four times without losing its catalytic performance for butylation reaction.     

Al-MCM-41介孔分子筛吸附喹啉的性能

在碱性条件下,采用水热晶化法,以偏硅酸钠为硅源,铝酸钠为铝源,CTAB为结构模板剂,成功合成出了含铝介孔分子筛Al-MCM-41。采用XRD、BET等手段对合成的Al-MCM-41进行表征,对柴油中的氮化物喹啉进行了吸附实验,考察了Al-MCM-41介孔分子筛对氮化物喹啉的吸附能力,探究了硅铝比为60的Al-MCM-41分子筛对喹啉溶液吸附的热力学和动力学行为,测得353.15～393.15 K 温度范围内的吸附等温线数据,用Langmuir、Freundlich方程对此进行拟合,并根据热力学原理计算得到吸附过程中的ΔH、ΔG、ΔS值和吸附表观活化能。结果表明, 硅铝比为60的Al-MCM-41具有较大的孔容、比表面积和较窄的孔径分布,结晶度和有序性高。等温吸附平衡符合Freundlich 等温线模型,其ΔH -0.7682 kJ·mol^-1,ΔG -28.1215 kJ·mol^-1, ΔS 73.2434 J·mol^-1·K^-1,吸附动力学符合Pseudo拟二级方程,E_a为2.8575 kJ·mol^-1。     

Novel synthesis of ordered mesoporous materials Al-MCM-41 from bentonite

This paper reports the synthesis of ordered mesoporous materials Al-MCM-41 with a specific surface area of 1018 m²/g from bentonite. Pretreated bentonite was simultaneously used as silica and aluminum sources without addition of silica or aluminum reagents. Orthogonal experiments were adopted to optimize the processing parameters. The samples were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), N₂ adsorption–desorption measurements and Fourier transform infrared spectra (FTIR) techniques. The obtained materials were hexagonal Al-MCM-41. Calcination removed the surfactant while new bonds increased the crosslinking of the frameworks. Proper Si/Al molar ratio was critical for the formation of highly ordered mesoporous materials.