Influence of Ti Incorporation to Bimetallic Mesoporous Carbon in the Production of 2,5-Dimethylfuran from Biomass Derivatives

Catalysis Letters - Monometallic and bimetallic supported catalysts were developed to produce 2,5-dimethylfuran (DMF) trough hydrogenolysis of 5-(hydroxymethyl)furfural (HMF). Detailed...     

Studies on the synthesis of diacetyl over oxidation zeolite catalysts

Diacetyl (2,3-butanedione) synthesis from methyl ethyl ketone over oxidation zeolites using O₂ as oxidant was studied. Various zeolites with Fe, V and Ti as active sites were employed. VS-1, Ti-NCL, Ti-MCM-41 and FeBEA type materials were synthesized and characterized by BET, FTIR, XRD, pyridine adsorption and template desorption. The detailed study of the effect of reaction temperature, the effect of concentration of oxygen and the addition of water was realized. The most active catalyst was zeolites with V as oxidation center.     

Inhibition of the Hydrogenation and Hydrodesulfurization Reactions by Nitrogen Compounds over NiMo/Al2O3

The inhibiting effect of nitrogen compounds on the hydrogenation of aromatic compounds and on the hydrodesulphurization (HDS) of dibenzothiophene (DBT) and 4,6-dimethyl dibenzothiophene (4,6 DMDBT), has been systematically investigated over a commercial NiMo hydrotreating catalyst. Amongst the different nitrogen compounds considered, interestingly ammonia was found to have the strongest inhibition effect on hydrogenation as well as on hydrodesulfurization reactions. The inhibiting effects were found to increase in the order quinoline < tetrahydroquinoline < indole < indoline < ammonia for phenanthrene/tetralin hydrogenation and HDS reactions. The molecules with nitrogen atoms having higher negative Mulliken charges showed higher adsorption constants.     

Nature and Reactivity of the Active Species Formed After NO Adsorption and NO + O2 Coadsorption on an Fe-Containing Zeolite

Reactivity of the NO adspecies on Fe-ZSM-11 was studied by FTIR in situ. The effect of Fe content and the oxidation state of Fe in the samples were correlated with the catalytic activity. The relation between the adsorbed species, the Brønsted sites and catalytic activity in the SCR of NO_x to N₂ was also investigated. Moreover, FTIR allowed us to identify the active sites and the adsorption complexes present in FeMFI. Samples prepared by the sol–gel method with different Fe content displaying vastly different activity and selectivity in the reduction of NO to N₂ with isobutane in excess of O₂. Thus, in contact with pure nitric oxide, NO ions, mononitrosyl groups, nitro groups and nitrate ions have been identified. Feⁿ⁺ active sites are the most probable centers for NO oxidation to NO₂ and its further conversion to adsorbed nitro groups and nitrate ions, steps that are crucial for NO reduction. The concerted action of Feⁿ⁺ and H⁺ sites of the catalysts over the NO conversion to N₂ and isobutane conversion was analyzed.     

Kinetic Studies on Diacetyl Synthesis over V-Containing Zeolites

The gas-phase oxidation of methyl ethyl ketone (MEK) was studied on V-ZSM-5 zeolite in the presence of molecular oxygen. Two types of competitive partial oxidations, i.e., diacetyl formation and oxidative scission reaction leading to acetaldehyde and acetic acid, took place at 200–350°C. A detailed kinetic study was realized for the oxidation reaction, a linear relationship was observed between the conversion and partial pressure of oxygen, and an activation energy of 16 kcal/mol was encountered. The content of vanadium in the catalyst was also analyzed.     

Fourier Transform IR Study of NO + CH4 + O2 Coadsorption on In-ZSM-5 DeNOx Catalyst

Reactivity of the NO and NO₂ adspecies in the coadsorption of NO with CH₄ and O₂, and the effect of Si/Al ratio of In-ZSM-5 were studied by FTIR in situ. The relation between the adsorbed species and catalytic activity in the SCR of NO_x to N₂ was also investigated. The adsorption of NO over this catalyst was performed at room temperature with pure NO followed by purging with vacuum. When NO was introduced to the samples, three peaks were observed by FTIR: 1622 and 1575 cm^-1, which can be assigned to adsorbed (ONO)- over InO⁺ site and NO² over InO⁺ site, respectively, and at 1680 cm^-1 corresponding to NO₃ ^--H. Coadsorption of nitrogen monoxide, methane and oxygen at room temperature of the samples with Si/Al ratio of 17(a), 27(b) and 50(c), allowed us to determine that sample (b) has large amount of NO₂–InO⁺ adsorbed species, which are the most important intermediates in the SCR of NO_x. The bands at 1575 and 1680 cm^-1 are more intense in samples (a) and (c). When the coadsorption of the mixture was performed at 400 °C, we can see that the adsorbed species are larger in sample (b). Taking into account the catalytic performance of the catalysts and the PAC results obtained by us earlier, this last indium specie, only present in the sample with Si/Al = 27, should be associated with the catalytic active specie for the SCR of NO_x.     

Studies of Vitamin K3 synthesis over Ti-containing mesoporous material

In this paper we report the synthesis of Vitamin K3 or Menadione by selective oxidation of 2-methyl naphthalene with H₂O₂ using Ti-MCM-41 synthesized by different methods. We studied the relationship between the catalytic activity and the structural characteristics and the coordination number of Ti of the catalyst. Different parameters affecting the oxidation of 2-methyl naphthalene like amount of the catalyst, hydrogen peroxide/substrate ratio, reaction temperature and the nature of the solvent are described. The experiment design—response surface methodology is used in this work to optimize the selective oxidation of 2-methyl naphthalene to vitamin K3. The application of this methodology lead us to a better understanding of the influence of the different factors (amount of catalyst, reaction temperature, H₂O₂ and reaction time); and their interactions, reducing the operation costs, achieving efficiency and effectiveness in this process.