Janusz Janas

Interaction of allyl iodide with molybdate catalysts for the selective oxidation of hydrocarbons

Abstract The interaction of allyl iodide with MoO 3 , Bi 2 O 3 , and molybdates of Bi, Co, and Mg has been studied in the temperature range of 270–480 °C. Although practically inactive in the allylic oxidation of propylene, MoO 3 yielded 100% acrolein at 320 °C, when in contact with allyl iodide. On Bi 2 O 3 , only 1,5-hexadiene and benzene were formed, whereas bismuth molybdate produced both oxygenated and nonoxygenated products. This confirms the multicenter model of allylic oxydation, the low-valent cation being responsible for activation of the hydrocarbon molecule and Mo-O polyhedra for insertion of oxygen. Stoichiometric CoMoO 4 and MgMoO 4 were inactive in the formation of acrolein from allyl iodide because the acrolein-like intermediate formed on the surface was unable to desorb. This indicates that the third condition of an active catalyst is the ability to desorb the oxygenated product by releasing the oxygen ion of the lattice sufficiently readily. When an excess of MoO 3 is present in these molybdates, they become active in the formation of oxygenated products.

Catalytic properties of defective brannerite-type vanadates: I. Reactive specificity of (202̄) and (201) crystallographic planes of Mn1 − xφxV2 − 2xMo2xO6 in oxidation of propylene

Oxidation of propylene in the presence of Mn1 − xφxV2 − 2xMo2xO6 solid solutions (0 ≤ x ≤ 0.3, φ denotes a cation vacancy at the Mn2+ site) has been studied in an integral-flow system at 360–440 °C over a wide range of contact time. Acrolein, acrylic acid, acetic acid, acetaldehyde, CO, and CO2 were identified as the reaction products. Reactive specificity of the (202) and (201) crystallographic planes has been observed. The (202) plane is much more active and characterized by at least two types of active centers (yielding C3 and C2C1 products) able to incorporate, without desorption, more than one oxygen atom into the molecule of propylene or into the products of its degradation. On the contrary, on the (201) plane predominate centers capable of the successive, one by one, incorporation of oxygen into the organic molecule, separated by desorption-adsorption processes. A common feature of both planes is that the total combustion markedly diminishes with the increase of the composition parameter x. Detailed schemes of the reaction on both crystallographic planes are proposed and discussed.

Catalytic oxidation of CH2Cl2 on sodium doped Al2O3

Abstract Influence of the deposition of Na+ ions on γ-Al2O3 on its surface properties and catalytic activity in oxidation of CH2Cl2 by gas phase oxygen has been studied. IR spectra indicate that the concentration of OH groups is significantly reduced and Lewis acidity, related to exposed Al ions, is simultaneously decreased. Therefore, total catalytic activity is strongly depressed, no CH3Cl is formed as intermediate product, Cl2 appears in the products which is absent on pure γ-Al2O3 and the amount of CO2 is at all temperatures higher than that of CO. This indicates that parallel to the two mechanisms, operating in case of γ-Al2O3 and starting with mono- and bidentate adsorption of CH2Cl2 through its chlorine atoms on Lewis sites, a third reaction pathway appears starting with adsorption through hydrogen atoms.

Cr-doped Zr, Si-mesoporous molecular sieves as catalysts of CH2Cl2 oxidation

Abstract Zirconium-containing mesoporous silica of nominal Si/Zr ratio in the range 40–5 have been synthesized using dodecylamine as a structure-directing surfactant. The samples were characterized with PXRD, SEM/EDX, BET, CEC measurement and chemical analysis. The materials were used as supports for chromium species incorporated by means of cation exchange procedure. Gradual substitution of Si by Zr in the mesoporous framework results in an increasing structural disorder, increasing cation exchange capacity and increasing capacity for incorporation of Cr. All Cr-doped ZrMMS x catalysts are active in the deep oxidation of methylene chloride reaching 100% conversion at temperature ≥400°C. The catalytic performance depends strongly on the catalyst composition. The role of particular components in determining the catalytic activity and selectivities to various products is discussed.

NO adsorption on the active sites of Co- and/or in-containing ferrierite catalysts for the CH4-SCR-NO process

Catalytic tests, performed on Co-, In- and In/Co-ferrierites, revealed that those catalysts were efficient for the selective catalytic reduction of NO with methane (CH4-SCR) in the presence of water. Previous investigations have shown that a synergetic effect was present for the binary samples (In/Co-FER) of various exchange degrees—the conversion of NO to N2 was as high as 80–100% in a wide temperature range (520–820 K). NO sorption on In-, Co- and In/Co-ferrierites was followed by IR spectroscopy to identify nitrogen-containing species formed upon adsorption. We suggest that the synergetic effect could be due to the concurrent action of both kind of active species present in the binary catalysts: NO, adsorbed on Co2+ as mono- and dinitrosyls species could be easily transformed into nitro-oxygen compounds of higher ionic character on indium-oxygen compounds, which were introduced to the catalysts during the contact-induced ion exchange with In2O3 oxide.

Hydrotalcite-Derived catalysts for removal of nitrogen-containing volatile organic compounds

The catalytic properties of mixed oxides derived from, the multi-metallic hydrotalcites (HTs) containing Cu, Cr, V, Al and Zn were tested in the total oxidation of dimethylformamide with particular stress on to the role of the precursor composition and the temperature of thermal decomposition (400°C and 550°C). Optimum performance for the 400 series was given by the material obtained from the Cu, Zn, Cr, Al, V-HT, while in the 550 series the catalyst derived from the Cu, Cr, V-HT precursor gave best results. The observed activity and selectivity patterns are discussed in terms of the catalysts physico-chemical properties.

Selective catalytic reduction of NO with methane or ethene on ferrierite-and mordenite-type zeolites containing copper, cobalt and indium

Abstract The selective catalytic reduction (SCR) process of NO in the presence of ferrierite- and mordenite-type catalysts has been studied. Methane and ethene were used as reducing agents. The oxidising properties of the catalysts were also assessed. The catalytic performance of Cu- containing zeolites was compared for ferrierite, mordenite and ZSM-5 (with ethene). When cobalt and indium ions were present simultaneously in zeolite ferrierite, a pronounced synergetic effect was found in the title reaction using methane.

State of cobalt in CoSiBEA zeolite and ITS role in NO SCR with ethanol

Abstract Co x SiBEA catalysts (x = 0.7 and 3.6 Co wt %) prepared by two-step postsynthesis are characterized by physical techniques and investigated in NO SCR with ethanol. Their catalytic properties depend on the nature and environment of Co species as shown by XRD, diffuse reflectance UV-vis, EPR and TPR.