Zeolite by impregnation

In the above-mentioned studies, solid-state ion exchange was used to prepare the non-acidic catalysts. The coordination of the copper after the preparation did not receive attention. We have prepared non-acidic copper-zeolites by impregnating zeolites of the mordenite type with aqueous copper salts. The preparation and characterization of these materials and the catalytic properties in the chlorobenzene conversion with water and ammonia will be discussed here. A second objective of the present study is to investigate the possibilities of copper-zeolites in nucleophilic substitutions with other chloroaromatics than chlorobenzene as substrates. Therefore, the substitutions of chlorotoluenes and dichlorobenzenes will be tested as model reactions. 

Other basic zeolites are those prepared by Baba et al. [79], consisting of low-valent Yb or Eu species introduced into alkali ion-exchanged Y zeolites by impregnation with Yb or Eu metal dissolved in liquid ammonia then heating under vacuum at ca 470 K. These materials catalyze the Michael addition of cyclo-pent-2-enone and dimethyl malonate at 303 K, without solvent, yielding, after 20 h reaction, 81 % Michael adduct with 100% selectivity [80,81]. 

Europium and ytterbium (R/zeolite) introduced into K+-exchanged Y-zeolite by impregnation from liquid ammonia solutions similarly show various catalytic reactivities with changes in evacuation temperatures (Baba et al. 1992). The changes in the chemical state of rare earths with the evacuation temperature are studied by IR and X-ray absorption... 

Michael reaction of cyclopent-2-enone with dimethyl malonate has been studied on europium-containing Y zeolite at 30°C (Baba et al. 1995). In this case, europium was introduced into K+-exchanged zeolite by impregnation from a solution of the metal on... 

Modification of H-ZSM-5 zeolites by impregnation with H3PO4 has become a common technique to improve their activity and selectivity [190,191]. In parallel with these changes, however, the transport properties of the zeolite crystallites are also changed. As in the cases of hydrothermal treatment and coking discussed above, a combined application of PFG NMR to study both intracrystalline diffusion and intercrystalline molecular exchange may provide information about... 

Baba et al. prepared low-valent lanthanide species introduced into zeolite by impregnation from Y and Eu metals dissolved in liquid ammonia followed by evacuation at 773 K[46]. The resulting compounds catalyzed 1-butene isomerization by anionic mechanisms. TPD results with the catalysts suggest that metal imides such as EuNH act as basic sites. 

Besoukhanova et al. [29] prepared 5 wt.% Pt/L zeolites by impregnation of L zeohtes exchanged with Li, Na, K, Rb and Cs with Pt(NH3)4Cl2. A TEM study indicated that the Pt-dispersion was inhomogeneous with large particles on the external surface, 1-2.5 nm particles both inside and outside the zeolite, and cyhnders (length 4-7 nm, width 1.5 nm) inside the zeolite. It was assumed that IR bands of adsorbed CO near 2000 cm corresponded to Pt-carbonyls formed by the reaction of CO on very small nuclearity Pt-clusters (e.g., to 0.6-0.8 nm) not visible on TEM micrographs. The band near 2060 cm attributed to linear-... 

The sawdust used in this work was a radiata pine. HZSM-5 and HY pellet was purchased from Zeobuilder, Ga was impregnated over zeolites by excess water evaporation. The catalytic upgrading... 

Molybdenum/zeolite catalysts prepared by impregnating zeolites with ammonium hepiamolybdate solution generally give rise to poor dispersion of molybdenum [2]. In contrast, ion exchange would be an ideal method for loading active metal species onto supports. Few cationic forms are available as simple salts of molybdenum of high oxidation... 

MEDISORBON An adsorptive process for removing mercury and dioxins from flue-gas. The adsorbent is a dealuminated zeolite Y manufactured by Degussa. For mercury removal, the zeolite is impregnated with sulfur. Developed in 1994 by Lurgi Energie und Umwelt and piloted in Germany and The Netherlands. 

Cogel method by impregnating Ti02-Si02 cogel with TEAOH solution in the presence of some amount of aluminium ions. Crystallization at 408 K while tumbling the autoclave (60 rpm). Zeolite yields —29% Si/Al — 300. Requires lesser amount of TEA+ ions than classical prehydrolysis method... 

The CVD catalyst exhibits good catalytic performance for the selective oxidation/ammoxida-tion of propene as shown in Table 8.5. Propene is converted selectively to acrolein (major) and acrylonitrile (minor) in the presence of NH3, whereas cracking to CxHy and complete oxidation to C02 proceeds under the propene+02 reaction conditions without NH3. The difference is obvious. HZ has no catalytic activity for the selective oxidation. A conventional impregnation Re/HZ catalyst and a physically mixed Re/HZ catalyst are not selective for the reaction (Table 8.5). Note that NH3 opened a reaction path to convert propene to acrolein. Catalysts prepared by impregnation and physical mixing methods also catalyzed the reaction but the selectivity was much lower than that for the CVD catalyst. Other zeolites are much less effective as supports for ReOx species in the selective oxidation because active Re clusters cannot be produced effectively in the pores of those zeolites, probably owing to its inappropriate pore structure and acidity. 

Re-Pt interactions have also been evidenced by EXAFS analysis of catalysts prepared by impregnation of a solution of HRe(CO)s in zeolite-containing anionic... 

To prepare alkali- or alkaline earth-modified zeolites or mesoporous moleeular sieves, identieal general methodologies are used. Thus, alkaline earth eation-exehanged zeolites are prepared by exehange of the zeolite in the sodium form in aqueous solution of alkaline earth metal salts, followed by washing and ealeination. Alkaline earth metal oxides loaded in zeolites are also prepared by impregnation of alkaline earth metal salts sueh as nitrates, aeetates, or ethoxides followed by ealeination (70,215,216). 

A further possibility for side-chain alkylation of toluene is oxidative methylation with methane. Catalysts with occluded alkali metal oxides, prepared by impregnating zeolites with alkali metal hydroxides followed by calcination, usually exhibit better performance.441 Further enhancement was achieved by impregnating ion-exchanged zeolites 442 Significant improvements in stability and the yields of Cg hydrocarbons were also observed when NaX was impregnated with 13% MgO which was found to increase the amounts of active sites.443... 

A unique titanium(IV)-silica catalyst prepared by impregnating silica with TiCLt or organotitanium compounds exhibits excellent properties with selectivities comparable to the best homogeneous molybdenum catalysts.285 The new zeolite-like catalyst titanium silicalite (TS-1) featuring isomorphous substitution of Si(IV) with Ti(IV) is a very efficient heterogeneous catalyst for selective oxidations with H2C>2.184,185 It exhibits remarkable activities and selectivities in epoxidation of simple olefins.188,304-306 Propylene, for instance, was epoxidized304 with 97% selectivity at 90% conversion at 40°C. Shape-selective epoxidation of 1- and 2-hexenes was observed with this system that failed to catalyze the transformation of cyclohexene.306 Surface peroxotitanate 13 is suggested to be the active spe-... 

Microporous superbasic catalysts based on zeolites suitable for alkene isomerization were developed by Martens et al. [28-30]. They have high activity in the 1-butene isomerization and side-chain alkenylation of xylene [31], and are prepared by impregnating a dehydrated zeolite (NaY) with NaN3 in alcoholic solution. Subsequent decomposition of the azide inside the zeolite pores produces metallic sodium particles Nax°and cationic sodium clusters Na43+. The high catalytic activity was attributed to the ionic sodium clusters as they could be detected using ESR spectroscopy. 

Otherwise, by impregnating a Pd precursor onto a basic K-exchanged FAU zeolite a highly selective bifunctional catalyst is obtained for the low-pressure one-step synthesis of 2-ethylhexanal (a component of perfumes and fragrances) from M-butyraldehydc and H2 in a fixed-bed reactor/12,131 Under optimum reaction... 

MF1 type zeolites are known to show enhanced selectivity to p-substituted products in alkylation and isomerization of aromatic molecules [e.g. 1,2,3,4]. This shape selectivity is more pronounced with larger zeolite crystals and can be further enhanced by modification of the parent zeolites through post-synthesis treatments like impregnation with basic oxides, metal salts or the deposition of silica or coke [3,5,6,7]. The gain in selectivity is, however, usually accompanied with loss in catalytic activity and in some cases more rapid deactivation [8,9]. Despite the large number of patents and reports in open literature, the reasons for the enhancement of shape selectivity of MFI zeolites by post-synthesis treatment and the limits of the severity of this treatment are not unequivocally explained to date. 

The catalysts were prepared using 50 wt.% of ZSM-5 with varying level of ion exchange. The zeolite was subjected to two- or one-step treatment with ammonium chloride solution. Zeolite was incorporated by.a method in which zeolite and aluminium hydroxide were pasted, mixed and extruded. The catalysts contained 8 or 12 wt % of NiO 4 wt.% were introduced in the course of the carrier forming process, the remaining portion of nickel being loaded by impregnation. 

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