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.     

Synthesis and Characterization of Al-MCM-41 and Al-MCM-48 Mesoporous Materials

A novel route in the synthesis of Al-MCM-41 and Al-MCM-48, using tetraethoxysilane (TEOS) and sodium aluminate (NaAlO₂) as Si and Al source has been obtained. The effect of surfactant nature and the synthesis conditions such as surfactant/Si ratio and hydrothermal treatment time on the formed mesostructure regularity has been studied. Different methods of template removal have also been evaluated. The samples were characterized by X-ray diffraction, nitrogen physisorption, FT-IR, and solid-state MAS NMR spectroscopy.     

MCM-41沸石分子筛的合成与应用

对MCM-41沸石的结构、合成方法、模板剂、催化方面的应用及合成原料进行了综述。     

Hydrothermal synthesis, characterization, and photocatalytic performances of Cr incorporated, and Cr and Ti co-incorporated MCM-41 as visible light photocatalysts for water splitting

A series of Cr incorporated, and Cr and Ti co-incorporated MCM-41 photocatalysts were synthesized by hydrothermal method. X-ray diffraction (XRD), UV–vis diffuse reflectance spectra (UV–vis), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence analysis (XRF), N₂ adsorption–desorption isotherms and Raman spectra were used to investigate the effects of the incorporated elements on the structure of MCM-41. The experimental results for photocatalytic water splitting under visible light irradiation (λ > 430 nm) demonstrated that the photocatalytic activities of Cr-MCM-41 and Cr-Ti-MCM-41 catalysts for hydrogen production decreased with an increase in the amount of Cr incorporated. Compared with the Cr-MCM-41 which had the same amount of incorporated Cr, the Cr-Ti-MCM-41 exhibited much higher hydrogen evolution activities.     

Double organic modification by 3‐chloropropyl and methyl groups on pure silica MCM‐41 and Ti‐MCM‐41: efficient catalyst for epoxidation of cyclododecene

Simultaneous surface modification by 3‐chloropropyl and methyl groups on the same Si atoms resulted in hydrophobic and highly ordered mesoporous silica with a very high surface area. ¹³C and ²⁹Si MAS NMR spectra indicate homogeneous grafting of chloropropyl and methyl groups in the silica matrix and this organically modified Ti‐MCM‐41 shows outstanding catalytic performance in the epoxidation of cyclododecene using tert‐butyl hydroperoxide as oxidant. This revised version was published online in July 2006 with corrections to the Cover Date.     

MCM-41-supported Co-Mo catalysts for deep hydrodesulfurization of light cycle oil

Light cycle oil (LCO), a by-product of the fluid catalytic cracking (FCC) process in a petroleum refinery, can be used as a blendstock for the production of diesel and jet fuels. Regulatory and operational issues result in need for new and more active catalysts for the deep hydrodesulfurization (HDS) of diesel feedstocks, such as LCO. This paper reports the activity of a mesoporous molecular sieve MCM-41-supported Co-Mo catalyst in comparison to a commercial γ-alumina (Al₂O₃)-supported Co-Mo catalyst for the desulfurization of a LCO with a sulfur content of 2.19 wt.%. The HDS of dibenzothiophene, 4-methyldibenzothiophene, and 4,6-dimethyldibenzothiophene—polyaromatic sulfur compounds present in LCO—and their relative reactivities in terms of conversion were examined as a function of time on stream in a fixed-bed flow reactor. The MCM-41-supported catalyst demonstrates consistently higher activity for the HDS of the refractory dibenzothiophenic sulfur compounds, particularly 4,6-dimethyldibenzothiophene. The presence of a large concentration of aromatics in LCO appears to inhibit the HDS of the substituted dibenzothiophenes.     

Thermoporometry as a new tool in analyzing mesoporous MCM-41 materials

Thermoporometry, a calorimetric procedure, is applied for measuring the pore size distribution, pore volume and surface area of mesoporous MCM-41 molecular sieves using water as the adsorbate. A series of MCM-41 materials with various pore diameters was synthesized and subjected to the new method. The results are compared with nitrogen physisorption. Both methods are complementary, whereby the former provides also information about the pore shape. MCM-41 materials with pores wider than 50 Å also allow the use of benzene as the adsorbate in thermoporometry.     

The ring transformations of 1,2,3,4-diepoxybutane (2,2′-bioxirane) catalysed by various aluminosilicates

The transformations of a molecule containing two adjacent epoxide rings, 2,2-bioxirane that is, were studied over various acidic aluminosilicates (HZSM-5, HY-FAU, AlMCM-41), for the first time, In the 373–473 K temperature range, in a pulse reactor, a ring-opening–ring-enlargment reaction producing furan only occured over the zeolites and it was the predominant reaction on AlMCM-41 as well. The driving force of this transformation route is water formation via elimination from 2,2-bioxirane. Suprising is the lack of the mono- or dialdehyde, the would-be products of the cleavage of the sterically more hindered C–O bonds – an acid-catalysed reaction typical for alkyl-substituted oxiranes.     

New acid catalyst comprising heteropoly acid on a mesoporous molecular sieve MCM-41

New solid acid catalysts, consisting of heteropoly acid (HPA) H₃PW₁₂O₄₀ (PW) supported on a mesoporous pure-silica molecular sieve MCM-41, have been prepared and characterized by nitrogen physisorption, X-ray diffraction, FT-IR, and³¹P magic angle spinning NMR. The PW/MCM-41 compositions with PW loadings from 10 to 50 wt% have 30 Å uniformly-sized mesopores. HPA retains the Keggin structure on the MCM-41 surface and forms finely dispersed HPA species. No HPA crystal phase is developed even at HPA loadings as high as 50 wt%. PW/MCM-41 exhibits higher catalytic activity than H₂SO₄ or bulk PW in liquid-phase alkylation of 4-t-butylphenol (TBP) by isobutene and styrene. In the alkylation of TBP by styrene, PW/MCM-41 shows a size selectivity compared to bulk PW and PW/SiO₂, providing higher yields of a 2-(1-phenylethyl)-4-t-butylphenol, at the expense of the more bulky 2,6-bis-(1-phenylethyl)-4-t-butylphenol. The PW/MCM-41 compositions, having strong acid sites and a regular mesoporous system, are promising catalysts for the acid-type conversion and formation of organic compounds of large molecular size.     

Isomerization and Hydrocracking of n-Decane over Bimetallic Pt–Pd Clusters Supported on Mesoporous MCM-41 Catalysts

n-Decane hydroconversion has been investigated on bifunctional catalysts comprising bimetallic Pt–Pd clusters supported on an AlMCM-41 (n_Si/n_Al = 23) mesoporous molecular sieve. The catalytic activity of the bimetallic Pt–Pd catalysts is higher than that of the monometallic Pt and Pd catalysts. The good balance between the two catalytic functions, namely acid sites and metal sites, also results in a higher isomer yield at a substantially lower reaction temperature. Moreover, cracking on the metal sites (hydrogenolysis) is largely suppressed over certain bimetallic catalysts.