The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Blanka Wichterlová - One of the best experts on this subject based on the ideXlab platform.
-
Activity of Co Ion Sites in ZSM-5, Ferrierite, and Mordenite in Selective Catalytic Reduction of NO with Methane
Journal of Catalysis, 2000Co-Authors: Dalibor Kaucký, Jiří Dědeček, Alena Vondrová, Blanka WichterlováAbstract:Abstract Selective catalytic reduction of NO with methane (CH 4 -SCR) in an excess of oxygen was investigated over CoH–, CoNa–, CoNaK–, CoBa–, and Co x O y –Co-zeolites of ZSM-5, ferrierite, and Mordenite structures. The exchanged Co ions have been shown to exhibit activity in CH 4 -SCR of NO, while protons or oxide-like Co species in Co–zeolites contribute to the CH 4 -SCR activity mostly by enhancement of the oxidation of NO to NO 2 . The sequence of Co–zeolites activity in CH 4 -SCR of NO (per zeolite weight) was Co–ZSM-5≅Co–ferrierite⪢Co–Mordenite for the highest Co loadings at Si/Al of 12, 8.4, and 9.2, but for the average Co ion site in the zeolite (in terms of turnover frequency, TOF, values) it was Co–ZSM-5>Co–ferrierite⪢Co–Mordenite. From a comparison of the dependence of TOF values for NO conversion to N 2 per Co ion and of the relative concentrations of the exchanged α-, β-, and γ-type Co ions (determined from quantitative analysis of the characteristic Co(II) Vis spectra) on the total Co concentration, the most active Co sites were estimated. The α-type Co ions, bound to framework oxygens of the wall of the main channel of Mordenite and ferrierite, are the most active among the Co ions in these zeolites. On the other hand, in ZSM-5 the β-type Co ions, coordinated to the deformed six-membered ring at the intersection of straight and sinusoidal channels possess the highest activity. The main factors contributing to the individual Co ions' activity are suggested to be cation location in the inner zeolite volume, coordination to the framework, and distances between the Co ions.
-
co2 ion siting in pentasil containing zeolites i co2 ion sites and their occupation in Mordenite a vis nir diffuse reflectance spectroscopy study
Microporous and Mesoporous Materials, 1999Co-Authors: Jiři Dědecek And, Blanka WichterlováAbstract:VIS−NIR diffuse reflectance spectra of Co2+H−Mordenites and co-cation (K, Cs, Ca, Ba)-containing Co−Mordenites with Co/Al varying from 0.0015 to 0.35 were studied. Three different sites-coordinations of the Co2+ ions in dehydrated Mordenite were found from interpretation of optical spectra, and the populations of these sites depending on Co-ion concentration were established. The assignment of characteristic absorption bands in the VIS spectrum to the Co2+ ions located at individual cationic sites was based on knowledge of siting of K, Cs, Ca, and Ba ions in Mordenite structure. Co2+ ions are located in sites A and C of the Mordenite pocket and in site E of the main channel. In site A, occupied preferentially in CoH−Mordenite, the Co2+ ion is coordinated to six framework oxygens of the twisted eight-ring. The number of coordinated framework oxygens and detail geometry of the “boat-shape” site C is not known. This site is occupied only at high Co loading. Site E, consisted of four oxygens forming a rectang...
Tsengchang Tsai - One of the best experts on this subject based on the ideXlab platform.
-
study on optimum base treatment of Mordenite for catalytic alkylbenzene transalkylation
Catalysis Today, 2016Co-Authors: Shangtien Tsai, Peiyu Chao, Peihsiun Chao, Manjyun Fang, Shangbin Liu, Tsengchang TsaiAbstract:Abstract The effect of base-treatment by single-cycle or multiple-cycle protocol on the textural and catalytic properties of Mordenite was studied. According to BET (Brunauer, Emmett and Teller) isotherm and temperature programmed desorption of hexane isomers, Mordenite after single-cycle base-treatment generated disordered mesopores in the size of 8 nm regardless of base-treating time, and multiple-cycle treatment generated 8–14 nm mesopores interconnected with silica-blocked 12-MR micropore. The latter treatment was more effective for enhancing both of the catalytic activity and stability of Mordenite than the former. Study on optimum base-treatment condition by varying cycle number and base-treating time in each cycle was conducted. The improved catalytic performance is attributed to the mesopore formation with enhanced diffusivity.
-
catalysis of alkaline modified Mordenite for benzene alkylation of diolefin containing dodecene for linear alkylbenzene synthesis
Journal of Catalysis, 2013Co-Authors: Jeshian Lin, S Alkhattaf, Jhaojyun Wang, Jenshi Wang, Ikai Wang, Rabindran J Balasamy, Abdullah M Aitani, Tsengchang TsaiAbstract:Abstract To improve the stability of the modified Mordenite for resolving catalyst deactivation problem in the linear alkylbenzene (LAB) synthesis, the desilication treatment was found to be more effective than other approaches such as dealumination or metal/zeolite. The improved stability of the desilicated Mordenite can be attributed to the enhanced diffusivity of oligomer by-products and coke precursors due to the enlarged mesopore size of the Mordenite. In addition, 2-phenyl LAB isomer selectivity can be tuned by modification of the microporous structure of Mordenite. The desilicated Mordenite showed unprecedented stability and the 2-pheny LAB isomer yield up to 78% even if the octadiene-containing dodecene feed was used.
-
base treated h Mordenite as stable catalyst in alkylbenzene transalkylation
Green Chemistry, 2009Co-Authors: Shangtien Tsai, Chienhao Chen, Tsengchang TsaiAbstract:The effect of post treatment methods on the pore structure of hierarchical Mordenite and its catalytic performance in transalkylation of heavy alkylbenzenes were studied. While the catalytic stability of H-Mordenite deteriorated with dealumination by acid or steam treatment, it was improved with desilication by base post treatment. Comparing to the state-of-the-art Pt/Mordenite catalysts, the desilicated H-Mordenite showed comparable stability giving the best benzene product purity at lower hydrogen and energy consumption and presented the greenest solution. The improved stability is attributed to an enhanced diffusion behavior in the meso-micro hierarchical structure. As confirmed by NMR and sorption data, base treatment can preferentially remove framework silica and re-insert octahedral aluminium into the Mordenite structure simultaneously, through which it created enlarged mesopores and defected 12-MR micropores to form a hierarchical porous structure.
Mahmoud Aghaziarati - One of the best experts on this subject based on the ideXlab platform.
-
determining an optimum catalyst for liquid phase dehydration of methanol to dimethyl ether
Applied Catalysis A-general, 2008Co-Authors: Nahid Khandan, Mohammad Kazemeini, Mahmoud AghaziaratiAbstract:Abstract The liquid-phase dehydration of methanol to dimethyl ether was investigated over various materials including synthetic zeolites, namely, ZSM-5, Y, Mordenite, Ferrierite and Beta as well as silica and alumina. The key characters investigated were the Si/Al ratio and cation exchange. The results showed that the Mordenite zeolite exchanged with H+ exhibited the highest activity in dehydration of methanol. After finding the most active catalyst, the Mordenite zeolite was modified with Cu, Zn, Ni, Al, Zr, Mg and Na via wet-impregnation method to further improve its selectivity, and characterized by AAS, XRD, NH3-TPD, NH3-FT-IR and BET surface area techniques. It was found that these materials affected activity of HM zeolite by changing its acidity. Ultimately, amongst all catalysts studied, Al-modified Mordenite zeolite exhibited optimum activity, selectivity and stability for methanol dehydration to dimethyl ether.
Tao Dou - One of the best experts on this subject based on the ideXlab platform.
-
one pot synthesis of hierarchical Mordenite and its performance in the benzylation of benzene with benzyl alcohol
Journal of Materials Science, 2015Co-Authors: Cuijuan Sun, Weibin Fan, Yanyue Wang, Aidong Lan, Peide Han, Tao DouAbstract:Hierarchical Mordenite with micropores and mesopores was one-pot synthesized through a soft-templating method using a special diquaternary ammonium-type surfactant as a mesoporogen. The obtained samples were characterized by XRD, N2 physisorption, SEM, TEM, TG-DTG, 27Al and 29Si NMR spectroscopy, and NH3-TPD techniques. The catalytic performance of the hierarchical Mordenite compared to that of conventional Mordenite and mesoporous AlMCM-41 material was evaluated in the benzylation of benzene with benzyl alcohol. The results show that the hierarchical Mordenite is highly crystalline and possesses large mesopore volume and strong acidity. Moreover, the prepared hierarchical Mordenite catalyst is high-efficiency for the conversion of benzyl alcohol into diphenylmethane due to the superior mass transfer ability and largely accessible acid sites. The apparent reaction rate constant for HMOR is 23 times that for CMOR and 8 times that for AlMCM-41. These results suggest that hierarchical zeolites with mesoporosity and strong acidity may be the ideal catalysts in reactions involving large molecules.
S Alkhattaf - One of the best experts on this subject based on the ideXlab platform.
-
catalysis of alkaline modified Mordenite for benzene alkylation of diolefin containing dodecene for linear alkylbenzene synthesis
Journal of Catalysis, 2013Co-Authors: Jeshian Lin, S Alkhattaf, Jhaojyun Wang, Jenshi Wang, Ikai Wang, Rabindran J Balasamy, Abdullah M Aitani, Tsengchang TsaiAbstract:Abstract To improve the stability of the modified Mordenite for resolving catalyst deactivation problem in the linear alkylbenzene (LAB) synthesis, the desilication treatment was found to be more effective than other approaches such as dealumination or metal/zeolite. The improved stability of the desilicated Mordenite can be attributed to the enhanced diffusivity of oligomer by-products and coke precursors due to the enlarged mesopore size of the Mordenite. In addition, 2-phenyl LAB isomer selectivity can be tuned by modification of the microporous structure of Mordenite. The desilicated Mordenite showed unprecedented stability and the 2-pheny LAB isomer yield up to 78% even if the octadiene-containing dodecene feed was used.
-
kinetics of toluene alkylation with methanol catalyzed by pure and hybridized hzsm 5 catalysts
Chemical Engineering Journal, 2012Co-Authors: Wahab O Alabi, Luqman Atanda, Rabindran Jermy, S AlkhattafAbstract:Abstract A kinetic study of toluene alkylation with methanol was performed over pure HZSM-5, Mordenite/ZSM-5 (hybrid of Mordenite and HZSM-5), and ZM13 (composite mixture of HZSM-5 and MCM-41 at pH 13). Experimental runs were conducted using a batch fluidized bed reactor at temperatures of 300, 350 and 400 °C and reaction times of 3, 5, 7, 10, 13, 15 and 20 s. The rate of toluene methylation and toluene disproportionation were studied on the three catalysts (toluene alkylation is usually accompanied by toluene disproportionation on acid catalyst). Based on the results obtained, a simplified power law kinetic model consisting of three reactions was developed to estimate the activation energies of toluene methylation and disproportionation simultaneously. Coke formation on catalysts was accounted for using both reaction time and reactant conversion decay functions. All parameters were estimated based on quasi-steady state approximation. Estimated kinetic parameters were in good agreement with experimental results. The order of alkylation ability of the catalysts was found to be ZM13 > HZSM-5 > Mordenite/ZSM-5, while the reverse is for toluene disproportionation (Mordenite/ZSM-5 > HZSM-5 > ZM13). Thus, alkylation of toluene is most favorable on ZM13 due to combined effect of mesoporosity induced through its synthetic route and acid content. Toluene/MeOH molar ratio of 1:1 was most suitable for toluene alkylation reaction.