Contents of Volume One, Summer 2001

• Higher Catalytic Activity Found by Incorporating MCM-41 into CoMo Catalyst Support
• ISRI IR Reactor Used to Study Surface Acidity of Metal Zeolite-Supported Catalysts and CO and NO adsorption on Rh/SiO₂Catalysts
• Copper(II) Ion Distribution Within TiO₂Powder
• Novel VOx Catalysts Studied for Partial Oxidation of Methane and Ammoxidation and Oxidation of Substituted Aromatics
• Studying Cu-ZSM-5 Deactivation under Wet Conditions during NOx Reduction by Propane
• IR Surface Acidity Studies of Ni Supported on Silica, Titania and Alumina

Researchers at UNICAT-UNAM, in collaboration with IMP and led by Prof. Dr. Jorge Ramirez, have found that incorporating MCM-41 into alumina support of CoMo catalysts leads to higher catalytic activity in the dibenzothiophene hydrodesulfurization (DBT HDS) reaction. A number of techniques were used to characterize the catalyst on the new support, including TPR studies with the ISRI RIG-100. These TPR studies showed the catalyst had less interaction with the support than could be observed with catalysts on pure alumina supports. The actual DBT HDS activity tests showed that, for high percentages of MCM-41, the activity of the catalyst was greater than those using pure alumina supports and increased as the MCM-41 content was increased. These activity tests were performed using the HP-100, ISRI’s automated high pressure micro-reactor system.

In addition to the above work, ISRI-HP-100 units and RIG-100 unit have been used in several proprietary studies funded by PEMEX.

References:

• J. Ramirez, R. Contreras, P. Castillo, T. Klimova, R. Zárate, R. Luna, "Characterization and Catalytic Activity of CoMo HDS catalysts supported on alumina-MCM-41" Applied Catalysis A: General 197 (2000) pp. 69-78.
• T. Klimova, D. Solis, and J. Ramirez, Catalysis Today 43 (1998) pp. 135-146.
• T. Klimova, M.L. Rojas, P. Castilllo, R. Cuevas, and J. Ramirez, Microporous and Mesoporous Materials 20 (1998), pp. 293-306.

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Along with the techniques of XRD, NMR, and Raman spectroscopy, Dr. Raul Lobo of the University of Delaware uses the well-known technique of pyridine adsorption to identify the number and type of acidic sites on catalyst surfaces. In particular, he has attempted to substitute zirconium into the framework of boron forms of the Beta zeolite. The ISRI Transmission IR Cell is well suited to the 10^-1Pa and 200 degrees C conditions required to observe the IR spectra of these zeolites. The IR suggested that the presence of Zr changed the nature of the catalyst from no acidic sites to a noticeable number of Lewis sites.

References:

• G.C. Juttu and R.F. Lobo Catalysis Letters 62 (1999) pp. 99-106

FTIR Studies of CO oxidation over Pd-Rh/SiO₂ Catalysts in an Oxidized State

The effect of catalyst preparation during CO oxidation on Pd-Rh/SiO₂ was studied via in-situ FTIR using ISRI’s IR cell-reactor by Prof. P. Araya and his group at the Chemical Engineering Department at the University of Chile in Santiago. These authors found a synenergistic effect due to the presence of oxidized Rh and reduced Pd. that depended on the precursor used during preparation by sequential impreganation.

References:

• Araya, P. and Weissmann C. Catalysis Letters 68, 1-2 (2000) pp. 33-39

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Drs. Gilberto Córdoba and Margarita Viniegra, together with other researchers in the Department of Chemistry at UAM-Iztapalapa, have used a number of techniques to do an in-depth study of the location of copper ions contained in titanium oxide powders created by the sol-gel process. Powder samples of different copper concentrations and treatment temperatures were thermally characterized using thermogravimetric analysis (TGA) and differential thermal analysis (DTA) , and single point BET surface area measurements. ISRI’s RIG-100 was primarily used to perform a number of temperature programmed reductions (TPR) on the samples as well as BET measurements. The TPR results from these experiments were verified using X-ray photoelectron spectroscopy (XPS). The TPR and XPS studies showed the presence of two different types of copper ions on the surface- one consisting of isolated copper ions and the other consisting of aggregates of copper oxide. The RIG-100 reactor was also used to prepare samples for electron spin resonance studies, which identified the presence of a third type of copper ion. This third type of ion was found to be isolated copper ions incorporated into the TiO2 network. All this shows the effectiveness of the sol-gel method as a tool for dispersion of copper within a titania network.

References:

• G. Córdoba, M. Viniegra, J.L.G. Fierro, J. Padilla and R. Arroyo " TPR, ESR and XPS Study of Cu+2 Ions in Sol-Gel Derivated TiO2" Applied Catalysis A: General 197 (2000) pp. 69-78

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Investigators at the Institute for Applied Chemistry Berlin-Adlershof have highly dispersed vanadium oxide on mesoporous siliceous MCM supports to create new catalysts for the partial oxidation of methane to formaldehyde. After characterizing the catalysts using a number of techniques, they used the ISRI RIG-100 as a micro-reactor to test the catalysts’ performance with and without cofeeding of steam. This testing showed that while the activation energy and reaction order data were similar to VOx on silica supports, the investigators could attain significantly higher space-time yields with the novel catalysts. The ammoxidation and oxidation of substituted aromatics on vanadium-containing catalysts have also been studied by researchers of the same group.

References:

• H.Berndt, A. Martin, A. Brückner, E. Schrier, D. Müller, H. Kosslick, G.-U. Wolf, and B. Lücke, “Structure and Catalytic Properties of Vox/MCM materials for the Partial Oxidation of Methane to Formaldehyde”, Journal of Catalysis, 191 (2000) pp. 384-400.
• A. Martin and B. Lücke, “ Ammoxidation and Oxidation of Substituted Aromatics on Vanadium Containing Catalysts", Catalysis Today 57, (2000) 61-70.

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In the Area of Chemical Engineering at UAM-Iztapalapa, Drs. Gustavo Fuentes and Sergio Gómez, together with doctoral candidate Angel Martínez, have been trying to elucidate the mechanism of the deactivation of the catalyst Cu-ZSM-5 during the selective catalytic reduction of NOx by propane under wet conditions. By connecting their RIG-100 to a mass spectrometer, they are able to follow the molecules evolved during temperature programmed experiments such as H2-TPR, TPD, and TPO to attain activity and structure characteristics of these NOx reduction catalysts. By combining other techniques such as EPR and UV-Vis with the characterization results, they are able to observe a direct correlation between the activity and copper species present in the different catalyst samples.

References:

• A. Martînez, S.A. Gómez, and G.A. Fuentes, " Deactivation of CU-ZSM-5 during Selcetive Catalytic Reduction of NO by Propane under Wet Conditions" Catalyst Deactivation 1997, C.H. Bartholomew and G.A. Fuentes (Editors), Stud. Surf. Sci. Catal., Vol 111, Elsevier (1997) p. 225
• S.A. Gómez, C. Campero, A. Martînez, and G.A. Fuentes, "Changes in Cu2+ Environment upon Wet Deactivation of CU-ZSM-5 of NOx Catalysts" Applied Catalysis A: General 197 (2000) pp. 157-164

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Dr. Jir-Mirn Jehng of National Chung Hsing University in Taiwan also uses the pyridine adsorption technique and couples it ammonium adsorption as well. The pretreatments in his ISRI IR reactor range up to 500 degrees C and he pulls vacuum up to 10^-4 torr. He is interested in nickel catalysts that use alumina, silica and titania as supports. He studies the effect that varying the nickel concentration has on the number of Lewis sites available.

Contact:

• Dr. Jih-Mirn Jehng, Department of Chemical Engineering, Naional Chung Hsing University, Taichung Taiwan R.O.C. at jmjehng@nchu.edu.tw

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