MCM-41

About: MCM-41 is a research topic. Over the lifetime, 2355 publications have been published within this topic receiving 91416 citations.

Effects of support identity and metal dispersion in supported ruthenium hydrodeoxygenation catalysts

Abstract: Substituted phenols are the most recalcitrant oxygenates in conventional pyrolysis oils and the dominant oxygenates in lower-oxygen content, formate-assisted pyrolysis oils (FAsP). Ru catalysts with a wide range of dispersion on carbon, silica, alumina, and titania supports were synthesized, characterized and evaluated for hydrodeoxygenation (HDO) activity using phenol as a model compound. Metal content, phase, and particle size were determined with ICP-OES, EXAFS/XANES, and CO pulse chemisorption, respectively. High dispersion of ruthenium on the supports converts more phenol to products. The majority of catalysts predominantly catalyze the hydrogenation (HYD) route typical of noble metal catalysts. A highly dispersed Ru/TiO2 catalyst shows unusually high selectivity toward direct deoxygenation (DDO) and outstanding activity. We suggest that the DDO pathway on titania involves a bifunctional catalyst, where hydrogen creates reduced titania sites, created by hydrogen spillover, that interact strongly with the phenol hydroxyl group.

Mesoporous molecular sieve MCM-41 supported Co–Mo catalyst for hydrodesulfurization of dibenzothiophene in distillate fuels

Abstract: A mesoporous aluminosilicate molecular sieve with MCM-41 type structure was synthesized using aluminum isopropoxide as the Al source. Supported Co–Mo/MCM-41 catalysts were prepared by co-impregnation of Co(NO3)2·6H2O and (NH4)6Mo7O24 followed by calcination and sulfidation. For comparison, conventional Al2O3-supported sulfided Co–Mo catalysts were also prepared using the same procedure. These two types of catalysts were examined at two different metal loading levels in hydrodesulfurization of a model fuel containing 3.5 wt% sulfur as dibenzothiophene in n-tridecane. At 350–375°C under higher H2 pressure (6.9 MPa), sulfided Co–Mo/MCM-41 catalysts show higher hydrogenation and hydrocracking activities at both normal and high metal loading levels, whereas Co–Mo/Al2O3 catalysts show higher selectivity to desulfurization. Co–Mo/MCM-41 catalyst at high metal loading level is substantially more active than the Co–Mo/Al2O3 catalysts.

Nickel containing MCM-41 and AlMCM-41 mesoporous molecular sieves: Characteristics and activity in the hydrogenation of benzene

Abstract: Pure siliceous and aluminosilicate mesoporous molecular sieves of MCM-41 type have been used as matrices for nickel incorporation (1.7–5%, w/w) via wet impregnation. Moreover, the AlMCM-41-32 material was modified by the cation-exchange method. The properties of the prepared catalysts were studied by means of XRD, XPS, N2-adsorption, H2-TPR, H2-adsorption and TPD. The reaction of gas-phase benzene hydrogenation was carried out on the prepared catalysts. The hydrogen spillover effect in this reaction was also studied using 3% Ni/MCM-41 and 3% Ni/AlMCM-41-32 catalysts diluted by MCM-41 and AlMCM-41-32, respectively. NiSiO3 and Ni2O3 species in the calcined precursor were shown by H2-TPR and XPS techniques. The presence of metallic aluminium is shown in the Ni/AlMCM-41-32 reduced materials. The reducibility of the catalyst is strongly influenced by the nature of the matrix and the method of preparation. The kinetic study of benzene hydrogenation on 1.7% Ni catalysts demonstrated various partial orders in hydrogen and benzene ascribed to the existence of several surface chemical processes. Investigations on the hydrogen spillover effect showed a maximum of activity for the diluted catalyst. The intensity of hydrogen spillover is strongly decreased in the presence of Al. The kinetic study with the mechanical mixtures suggested changes in the surface reactions due to the contribution of the support to the chemical processes. Moreover, the results strongly indicated that the migration of hydrogen atoms from the metal phase onto the support oxide is assisted by the aromatic hydrocarbon.

MCM-41 supported PdNi catalysts for dry reforming of methane

Abstract: A series of bimetallic PdNi catalysts supported on mesoporous MCM-41 with different Ni content (Ni/Si ratio of 0.2–0.4) was synthesized. The effect of Pd addition to Ni-containing catalysts as well as the effect of the Ni content on the surface and catalytic properties of the catalysts was studied. The samples were characterized using various techniques, such as energy-dispersive X-ray spectroscopy, N2 adsorption–desorption isotherms, X-ray diffraction, thermogravimetric and differential analyses, X-ray photoelectron spectroscopy, high resolution transmission electron microscopy and temperature-programmed reduction. Reforming of methane with carbon dioxide was used as a test reaction. The results indicated that the addition of a small amount of Pd (0.5%) to Ni-containing catalysts leads to formation of small nano-sized, easy reducible NiO particles. Agglomeration of NiO as well as of metallic nickel phase over PdNi samples increased with increasing the Ni content. Formation of filamentous carbon over surface of spent monometallic Ni and bimetallic PdNi catalyst was observed. In spite of filamentous carbon deposition, the catalytic activity and stability of bimetallic PdNi catalysts are higher than those of monometallic Ni one. Within bimetallic system, the PdNi catalyst with Ni/Si ratio of 0.3 revealed the best performance and stability caused by presence of small nickel particles well dispersed on the catalyst surface.