Mordenite-type Zeolite Research Articles

Solid-state ion exchange in zeolites: Part II. Alkaline earth chlorides / mordenite

Solid-state ion exchange of protons of acidic and non-acidic OH groups for alkaline earth cations in mordenite-type zeolites was investigated by means of TGA, temperature-programmed evolution of gases, IR and in-situ IR/GC measurements. The solid-state ion exchange occurs in two stages, i.e. via a low-temperature and a high-temperature process. Replacement of the protons of the acidic OH groups by alkaline earth cations considerably decreases the activity of hydrogene mordenite for catalysing hydrocarbon reactions such as conversion of ethylbenzene. The catalytic activity is greatly restored by treatment with water vapor subsequent to solid-state ion exchange.

Study of the chemisorption of formic acid on mordenite type zeolites, NaZ and HZ by 13C and 27AI MAS-NMR

L'etude par RMN-MAS du 13 C et de 27 Al de la chimisorption de HCOOH sur des zeolithes Z de type mordenite met en evidence les centres actifs et les intermediaires reactionnels

Synthesis of mordenite type zeolite using silica from rice husk ash

Synthesis of mordenite type zeolite using silica from rice husk ash

Recent developments in catalysis by zeolites

The catalysis of hydrocarbon cracking, isomerisation, alkylation, hydrogen transfer and related reactions, by zeolites has been extensively studied during the last two decades. Much of the work in this area has been carried out on faujasite and mordenite—type zeolites in their acidic forms. As a result of the enormous number of studies devoted to this subject a fair understanding of acid—catalysis by zeolites has resulted. Recently several excellent reports have reviewed the subject 11—71 . A characteristic feature of zeolites is their promoting effect in bimolecular reactions and their selectivity due to the shape of thc channels. The shape—selectivity has also been reviewed recently 8—10 I. More recently among the many branches of zeolite chemistry three topics have attracted the attention i.e. i) Since the discovery of a new class of zeolites called ZSM—5 or pentasil at Mobil Laboratories interest has been refocussed on shape selectivity catalysis by small pore zeolites of the mordenite or

Synthesis of Mordenite Type Zeolites

Synthesis of Mordenite Type Zeolites

EPR investigation of the structure and reactivity of Pd(I) species generated in synthetic mordenite-type zeolite

A mordenite-type zeolite exchanged with Pd(NH 3) 4 2+ ions has been studied by EPR spectroscopy after heat treatment at 500°C in flowing oxygen and then in vacuo. The signal with g ∥ = 2.97 and g ⊥ = 2.146 was unambiguously assigned to Pd(I) ions bonded to four lattice oxygen ions in a pseudo-square-planar symmetry at the center of an eight- or a twelve-membered ring of the zeolite. Pd(I)CO or Pd(I)OH (or H 2O) adducts were formed and characterized by g ∥ = 2.41 and g ⊥ = 2.105 or g ∥ = 2.35 and g ⊥ = 2.105 , respectively The decrease in the g values with respect to initial Pd(I) ions was interpreted in terms of the ligand effect, with the CO or the OH adduct in an axial position of a pyramidal square-planar complex, and the equatorial positions occupied by the four lattice oxygen ions. The adsorption of molecular oxygen led to a new EPR signal with g ⊥ = 2.050 and g ∥ 1.99 and a hyperfine structure of a sextet and an eleven-line pattern of 77-gauss splitting due to singly or doubly 17O-labeled diatomic oxygen species. The spectrum was attributed either to an O 2 − ion freely rotating about the internuclear axis or to an O 2 3− ion of V-center type.

Effect of Transition Metal lons on Cyclohexene Formation over Zeolite Catalyst

Oxidative dehydrogenation of cyclohexane was investigated at 180. v2900C over several kinds of X, Y and mordenite type zeolites of which Na were ion exchanged with transition metal ions. The: metal ions employed in this study were Cr(III), Cr(III), Fe(III), Co(III), Cu(1), Cu(III)and Tl(1). This reaction was observed over Na and Cq type Y zeolite catalysts, but carbon. dioxide was fermed in preference to cyclohexene or benzene. Oxidative dehydrogenation was.., . accelerated by exchange with the transition metal ions, especially by Fe(III), which were found to adsorb oxygen. The catalysts exchanged with the other metal ions showed a similar catalytic action as of Na type Y zeolite with rather lower activity. A pretty good selectivity with respect to partial dehydrogenatfon of cyclohexane to cyclohexene was obtained, in the presence of steam, over X and Y type zeolites exchanged with Fe(III)io s. Mordenite catalysts showed no catalytic activity for this reaction. The Fe(II)X catalyst was the most excellent of all catalysts used in this study, and the selectivity for dehydrogenation of cyclohexane to cyclohexene and benzene was increased with an increase in the degree of ion exchange, while combustion reaction was decreased.