Zeolites ion exchange

Scheme 6 Fructose can be transformed into 5-hydroxymethyl furfural (HMF) via acid-catalyzed dehydration. Solid acid catalysts applied to facilitate the reaction are zeolites, ion-exchange resins and solid inorganic phosphates. With sporadic success, notably with inorganic phosphates, other carbohydrate sources such as inulin can also be transformed into HMF.

In our experiments we screened zeolites, ion-exchange resins, heteropoly compounds and mixed metal oxides. Several alcohols were used to show the range of applicability. The selectivity was assessed by testing the formation of side products in a suspension of catalyst in alcohol (e.g. SZ in 2-ethylhexanol) under reflux for 24 hours. Under the reaction conditions, no by-products were detected by GC analysis. 

Table III. Marginal Cost-Effectiveness of Radium Removal by Zeolite Ion Exchange...

Copper(II) Ion Exchange. Starting with anhydrous Na Y and hydrated NH Y zeolites, ion exchange was carried out with filtered Cu(NO3)2 IHjO solutions of different concentrations in order to obtain samples with different Cu(II) contents. The equilibrations were carried out for 4 h at ambient temperature with v/m = 20 or 200 cm /g. 

S.S. Papadopulos Associates, Bethesda, MD 1West Valley Nuclear Services Company LLC, West Valley, NY Key words barriers, sorption, slurry wall, zeolite, ion exchange... 

Chemical analysis of scale deposits present on the surface of the failed clamp by X-ray diffraction revealed the presence of predominantly sodium iron oxide, sodium carbonate sodium chloride ( 10%), iron oxide and iron sulfide. The scale composition was consistent with the evaporated residue from the 80% quality steam, which had been leaking from the joint prior to the failure. The high sodium concentration in the scale was attributed to the zeolite ion exchange system used to soften the boiler feedwater, while the chlorides and sulfides were naturally present in the feedwater. 

Keane, M. A. (1998). Removal of copper and nickel from aqueous solution using Y zeolite ion exchangers. Colloids Surfaces A Physicochem. Eng. Aspects. 138, 1, 11-20. 

Various techniques are available for the introduction of metals into zeolites. Ion exchange and impregnation, e.g., by the incipient wetness or imbiberaent techniques, are often used. The former method introduces preferentially the cation into the zeolite, whereas the latter method also incorporates an equivalent number of anions. In both cases, the introduction of ions has to be followed by calcination and reduction steps. For zeolite-based catalysts the ion-exchange method is often preferred (97,9S). 

Taking into account the above considerations, it can be concluded that three types of the Fe-species are present in the Fe-treated Y-zeolites ion-exchanged type species, small Fe oxide clusters inside the supercages, and Fe oxides without interaction to the zeolite, and classified by combining TPR and TPS as the summary in Table 1. 

Besides the above CD processes, some of the recent novel applications of CD are outlined below. The production of amines from the hydrogenation of aniline and the selective production of diethanolamine from the reaction of monoethanolamine and ethylene oxide have been reviewed. A patent on the production of phenol from cumene hydroperoxide disclosed that solid acid catalysts such as zeolites, ion-exchange resins achieved 100% conversion with about 60 /o selectivity to phenol at 50-90°C and 0-10 psig. This process utilizes the heat of the decomposition of cumene hydroperoxide to effect the separation of the lower boiling components and hence reduces the energy cost and carbon dioxide emissions. 

The most common of the natural sedimentary zeolites found in the United States in mineable quantities are chabazite, clinoptilolite, erionite, and mordenite (2). Many crystalline zeolites decompose in acids, although mordenite and, to a lesser extent, erionite have been reported to be stable in acid solutions (2). The goal of this research was to evaluate the stability and cation-exchange capabilities of these common, natural, sedimentary zeolites in acidic solutions. The basic concepts of zeolite ion-exchange, usually emphasizing synthetic zeolites, may be found elsewhere... 

Despite the existence of basic sites in zeolites, the possibility of using zeolites as basic catalysts was forgotten for many years and it was realized only recently that they can also be successful in this field [56,57]. Two approaches have been used to prepare basic zeolites ion-exchange with alkali metal ions and generation within the pores of small clusters of alkali metals or oxides and alkaline earth oxides. Whereas simple ion-exchange with alkali metal ions produces relatively weakly basic sites, the presence of such clusters results in strongly basic sites. 

The recovery and purification of cesium-137 from Purex acid waste using a synthetic zeolite has been studied. Zeolite capacity and selectivity for cesium were determined. Stability of the synthetic zeolite to high radiation fields and chemical attack was adequately demonstrated. Kilocurie quantities of cesium-137 of 98+% chemical purity were prepared using zeolite ion exchange. 

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