Hydrogen mordenite

H(hydrogen)-mordenite catalyst The crystallites were approximate parallelepipeds, the long dimension of which was assumed to be the pore length. Their analysis was based on straight, parallel pores in an isothermal crystallite (2 faces permeable). They measured (initial) rates of dehydration of methanol (A) to dimethyl ether in a differential reactor at 101 kPa using catalyst fractions of different sizes. Results (for two sizes) are given in the table below, together with... 

Fig. 1. Counter-diffusion of (a) Benzene (B) vs. Pyridine (Py) and (b) ethylbenzene (EB) in Hydrogen Mordenite...

Kerr, Plank, and Rosinski reported the preparation and catalytic properties of aluminum-deficient zeolite Y materials 35). Topchieva and co-workers studied the catalytic properties of cationic forms of aluminum-deficient Y zeolites, the aluminum deficiency being effected by the H4EDTA method 36-40). They found that up to 50% aluminum removal increased both stability and cumene cracking activity maximum activity was observed at the 50% removal level. Increased catalytic cracking activity was observed by Eberly and Kimberlin for mordenites from which about 80% aluminum had been removed (. 1). Weiss et al. removed over 99% of the aluminum from a hydrogen mordenite and found the zeolite retained catalytic activity of the type induced by Bronsted acids 42). Although the initial activity of this material was lower than that of more aluminum-rich mordenites, the aging rate was markedly reduced, and in a relatively short time the aluminum-deficient catalyst was the most active. 

Adsorbents were synthetic zeolites 5A and 13X, manufactured by Linde, as well as an hydrogen mordenite manufactured by C.E.C.A. (Carbonisation et Charbons Actifs, Paris) the samples were in pelletized form and contained 20 wt % binder. From crystallographic data for zeolites 5A and 13X (19) and H-mordenite (20), W0 values were computed and corrected for the presence of the binder these Wo values appear in Table I. In the same way, we also studied a microporous carbon (Cecalite)... 

T,he original report by Barrer and Makki (1) that aluminum in a high A silica zeolite, clinoptilolite, could be extracted with mineral acid to give a silica pseudomorph, has given rise to considerable research on acid-extracted mordenite (2-6). Hydrogen mordenite is useful as an adsorbent and a catalyst, and its properties for some purposes are improved by partial extraction of the aluminum. Further, the ability to vary aluminum content while maintaining crystallinity offers the opportunity to leam more about the nature of the active sites in mordenite. 

R Mantha.S.Bathia.M.S.Rao Kinetics of Deactivation In Methylation of Toluene over H-ZSM-5 and Hydrogen Mordenite Catalysts itKtEng.Chem.Res. 30 (1991) 281... 

The noble metal component may be either palladium or platinum the effect of the concentration of both metals on methylpentane as well as on dimethylbutane selectivity in C6 hydroisomerization on lanthanum and ammonium Y-zeolite with Si/Al of 2.5 has been studied by M.A. Lanewala et al. (5). They found an optimum of metal content for that reaction between 0.1 and 0.4 wt.-%. The noble metal has several functions (i) to increase the isomerization activity of the zeolite (ii) to support the saturation of the coke precursors and hence prevent deactivation, as was shown by H.W. Kouvenhoven et al. (6) for platinum on hydrogen mordenite (iii) to support the hydrodesulfurization activity of the catalysts in sulfur containing feedstocks. 

Adsorption isotherms of oxygen, nitrogen, carbon dioxide, and sulfur dioxide on hydrogen-mordenite were measured at several temperatures in the range of O —IOO C. The SO2 and CO2 had considerably greater affinity for the adsorbent than the O2 and Ng. Using the pure-component data, multi-component isotherms were predicted and compared with experimental results. The more strongly adsorbed species completely overwhelm the lesser adsorbed components (e.g., SO2 vs. N2). Wherever 2 species of approximately equal affinity are adsorbed (e.g., CO2 + SOg), the temperature sensitivity of the individual components influences the extent of the competition. 

The hydrogen-mordenite (unit cell hydrated H8Al8Si4o096 24H2O) used in this study was provided by the Norton Co., Worcester, Mass., in the form of 1/16-inch pellets fabricated without a binder. This material is characterized by parallel 12-membered rings of silica-alumina tetra-hedra forming pores with effective diameters of 7-9A smaller cavities occur in the walls of the large channels. Mordenite has reported B.E.T. surface area of 400 to 500 m /gram (3) synthesis and other characteristics of this material are described well elsewhere (i, 5). 

Relatively speaking, the affinity of the hydrogen-mordenite is greatest for the SO2, then in decreasing order the CO2, N2, and O2 follow. This can be explained by differences in the electronic configurations of these adsorbates no "sieving would be expected in any of these systems since the molecular diameter of these gas molecules is well below the published pore diameters. The sorption of all the species is likely to be physical, since the calculated isosteric heats are all below 5 kcal/mole. 

Early adsorption studies indicated that the effective micropore openings in natural and synthetic mordenites were about 4A (2) and not ca. 7A as required by structural data. Later it was shown that this probably was caused by partial blocking of the main channels by calcium and/or sodium cations (3, 22). Sorption in the side channels is limited normally to molecules smaller than n-butane (4.9A) (3), while the main channels in hydrogen-mordenite are nearly filled by the larger cyclohexane (22), benzene, and neopentane molecules (3) of critical diam-... 

Hydrogen-mordenites are active at 200°-260 C for the isomerization of n-butane, cyclohexane (22), and o-xylene (23). They also ex-... 

A palladium-hydrogen-mordenite catalyst with a 10.8/1 silica/alumina mole ratio was evaluated for the hydroisomerization of cyclohexane. The rate of reaction followed a first-order, reversible reaction between cyclohexane and methylcyclopentane. The energy of activation for this reaction between 400° and 500°F was 35.5 it 2.4 kcal/mole. Cyclohexane isomerization rates decreased with increasing hydrogen and cyclohexane-plus-methylcyclopentane partial pressure. These effects are compatible with a dual-site adsorption model. The change of the model constants with temperature was qualitatively in agreement with the expected physical behavior for the constants. 

Site I is in the centre of the highly distorted 8 ring window, and in natural mordenite at least can be occupied by Na, K, and Ca in fully hydrated versions. In hydrogen mordenite any residual Na apparently occupies this site. Sites II,... 

Hydrogen Mordenite. Very interesting results were obtained by Barrer and Klinowski" who prepared hydronium large-port mordenites by acid exchanging sodium mordenite at 25 °C, and by decomposing 1S1H4 mordenite at... 

In this study, the fouling characteristics of copper exchanged hydrogen mordenite (CuHM) for NOx reduction by NH3 is examined to understand the effect of sulfur on the catalytic activity. This paper deals with sulfur tolerance of CuHM catalyst for NO... 

Scheme 4. Shape-selective isopropylation of naphthalene using hydrogen-mordenite catalyst, and names of important products.

Table 8 shows the recent results from our laboratory [Lai and Song, 1996]. The catalytic reactions were mainly conducted at 200-250 °C for 0.15-8 h under an initial pressure of 0.79 h a N2 or H2 using six catalysts a hydrogen Y zeolite, a lanthanum ion-exchanged Y zeolite, a hydrogen mordenite, and three noble metal loaded mordenites. Selected results are given in Table 7. Pt- and Pd-loaded mordenites displayed the highest selectivity towards /rani-DeHN (nearly 100%), with a Zrani-DeHN/cw-DeHN ratio of about 13 under H2 at 2(X)°C however, they are less effective under N2. Pre-reduction of Pt/HM30A could improve its catalytic effectiveness in N2 atmosphere.

The procedure for alkylation of polynuclear aromatics with mordenite catalysts developed at Dow Chemical [15,16] requires sodium mordenite with an SI from 0.6 to 1.0. The crystalline aggregates of mordenite range in size from 1-20 pm and are formed from crystallites ranging in size from 500-5000 A. The selected sodium mordenite is treated with inorganic acids to make hydrogen mordenite (HM). HM is calcined at 400-700 °C and further treated with strong acid to produce catalyst precursors. The severity of the thermal and acid treatments, the number and sequence of the treatments, and the type of binder defines the properties of the 3-DDM catalysts. 

Product by Boiling Range Feed Product from Platinum Hydrogen Mordenite... 

The nitrogen oxide content of dissolver off-gases can be further reduced to 10 ppm by adding NH3 to the gases leaving the absorber and passing the mixture over a hydrogen mordenite catalyst [P4], which reduces NO to N2 and H2 0. 

Pyridine chemisorption on hydrogen mordenite has been studied (11). As the calcination temperature was increased from 200° to 600°C, the population of Bronsted acid sites decreased and of Lewis acid sites increased. Above 300°C, 2 absorption bands (1462 and 1455 cm-1) were observed, suggesting the presence of 2 types of Lewis acid sites. Cannings suggested the following structures ... 

Fig.1 Counter-diffusion of a benzene (B) vs pyridine (Py) and b vs ethylbenzene (EB) in hydrogen mordenite (H-MOR) [11]...

The interpretation of the above IR results of the H20/zeolite system was supported by inelastic neutron scattering (INS) studies by Jobic et al. [658] of H2O adsorbed on hydrogen mordenite. These experiments were carried out in the range below 2000 cm. Activated and water-free H-mordenite gave INS bands at 320 and 1060 cm. On the basis of quantum mechanical calculations, these were assigned to the out-of-plane (yoh) and in-plane (6oh) deformation vibrations of the zeolitic OH groups, since these were predicted at 322 and 1047 cm". On... 

Fig. 45. IR bands of pyridine (nigt, mode, [679]) adsorbed on Bronsted acid sites (B-sites), true Lewis sites (L-sites) and cations (C-sites) in hydrogen faujasite-type zeolite H-Y (H-FAU), hydrogen mordenite (H-MOR) and sodium mordenite (Na-MOR) see text...

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