Copper-exchanged zeolites

Kieger, S., Delahay, G. and Coq, B. (2000) Influence of co-cations in the selective catalytic reduction of NO by NH3 over copper exchanged faujasite zeolites, Appl. Catal. B 25, 1. 

Rosback, D.H. (1973) Adsorbing olefins wih a copper-exchanged type Y zeolite. U.S. Patent 3,720,604. 

O Brien, J., Curtin, T., and O Dwyer, T.F. (2005) An investigation into the adsorption of aniline from aqueous solution using H-beta zeolites and copper-exchanged beta xeolites. Adsorpt. Sd. Technol, 23, 255. 

In realm of heterogeneous catalysis, a copper-exchanged zeolite (CuHY) modified with bis-oxazoline was found to exhibit modest asymmetnc induction in... 

Ruggiero, C. E., Carrier, S. M., Antholine, W. E., Whittaker, J. W., Cramer, C. J., and Tolman, W. B. (1993). Synthesis and structure and spectroscopic characterization of mononuclear copper nitrosyl complexes Models for nitric oxide adducts of copper proteins and copper exchange zeolites. J. Am. Chem. Soc. 115, 11285-11298. 

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. 

Butyrolactone reacts rapidly and reversibly with ammonia or an amine forming 4-hydroxybutyramides, which dissociate to the starting materials when heated. At high temperatures and pressures, the hydroxybutyramides slowly and irreversibly dehydrate to pyrrolidinones this dehydration is accelerated by use of a copper-exchanged Y-zeolite or magnesium silicate. 

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. 

Cu-Exchanged Zeolites. Copper ions and/or complexes exchanged into such commercially manufactured zeolites as MFI, MOR, FAU, FER, BEA and so forth have been shown to be active for deNOx catalysis with HCs. Catalytic deNOx activity for this reaction can be maximized when combining copper with the MFI structure zeolites, representatively ZSM-5, depending mainly on the nature of reductant and physicochemical properties of the zeolite employed. These Cu-based zeolites reveal the peak NOx reduction activity at higher tern-... 

The polymerization of pyrrole in zeolite channels was explored by Bein and coworkers. Pyrrole vapor was equilibrated with copper-exchanged, degassed NaY or Na-mordenite hosts at room temperature, and the formation of dark green to black samples was observed, whose infrared spectra showed the signature of bulk polypyrrole (Figure 8). The absence of detectable polypyrrole on CuNaA zeolite (whose windows are too small for adsorption of pyrrole) and the absent of d.c. 

Figure 8. Polymerization of pyrrole in copper-exchanged zeolite Y.

In the substitution with ammonia at 450°C, the Bronsted-acid activity of copper-exchanged mordenite leads to an increased conversion (Figure 6), but the steady-state conversions seem comparable. This was also observed with zeolite L [3]. However, the conversion of Cu/Na-mordenite at 400°C (data not depicted here) remains higher. The substitution selectivity seems unaltered at both temperatures. 

It is likely that the acidity of copper-exchanged zeolites plays a role in this isomerization. However, in initial experiments with copper-impregnated zeolites some isomerization was also detected. Thus the hydrogen chloride evolved during the substitution may also play a role. 

After aqueous impregnation, copper(II) chloride is present as a highly dispersed phase on the surface of zeolites. After a thermal treatment in nitrogen and subsequently in ammonia, the copper appears to be present as isolated ions in the zeolite. Therefore, impregnation is a suitable method to prepare non-acidic copper-zeolites. As copper vaporization is limited with a catalyst not having a cation excess, a zeolite pre-exchanged with ammonium ions and consecutively impregnated with copper seems especially suitable. 

Copper-exchanged zeolite ZSM-5 have received considerable attention of researchers over last several years because of their ability to promote both the total oxidation of alkanes and the decomposition of NOj [1 - 12]. However, little is known about the possibility of the CuH-ZSM-5 system modification as a result of the introduction of ions of the second active transition metal. A high and stable catalytic activity of Co/H-ZSM-5 in total oxidation of CH, was demonstrated recently [13]. Therefore, the mutual influence of two active components stabilized by H-ZSM-5 matrix is of interest. 

The duration of ion exchange affects the copper concentration of the zeolite longer exchange times lead to higher copper concentration. The exchange dynamics was studied by taking a series of zeolite samples from the ion exchange solution at different points of time. 

The amount of copper in the zeolite was measured by quantitative analysis. The results are presented in Fig. 3 as a function of the copper concentration in the ion exchange solution. The EPR intensity also gives an indication of the amount of copper exchanged onto the zeolite. These results are also depicted in Fig. 3. At low copper concentrations (up to 1 Cu/UC) the amount of Cu(II) exchanged onto the zeolite increases linearly with the copper concentration. 

The influence of the ion exchange time on the A/B ratio in the resulting zeolite samples was studied by CW-EPR. It was found that this ratio was independent of the ion exchange time (data not shown). The results of the quantitative analysis of the samples are presented in Figure 6. In this figure the amount of copper exchanged onto the zeolite is represented... 

In most studies on zeolites, alkanes and alkenes are used as the reductant alkanes are less active than alkenes. Gopalakrishnan et al. [70] studied the reduction of NO by propane over copper-exchanged zeohtes, namely mordenite, X-type and Y-type, at temperatmes ranging from 473 to 873 K. The following overall reaction occurs ... 

Cu(ll)-exchanged NaY zeolite. The exchange was performed in the same way using 1 g of zeolite and 2.22 g of CUCI2.2H2O in 13 mL of water. The solid was separated by filtration, washed and activated before use as described above. The copper content of the zeolite was 0.57 mmol g l. 

Cerium-, copper-cerium coexchanged ZSM-5, copper-MCM-22, copper- and cerium-EMT type zeolite, copper-FAU type zeolite and copper-Beta exhibit an activity of the same order as that of copper-ZSM-5 in NOx reduction under simulated Diesel exhaust conditions. Propene was used as the reducing agent. The catalysts were used in a powder form and their activities tested in a fixed-bed flow reactor at a space velocity of 50 000 H . Copper-SAPO-34 and cerium- and gallium-EMT type zeolite have a moderate activity under the same conditions. The presence of water vapor inhibits the activity of EMT-zeolites. When an ageing procedure is carried out on copper-EMT type zeolite, dealumination occurs. The increase of the Si/Al ratio of the zeolite does not limit the dealumination process. The exchange of the zeolite with lanthanum prevents the zeolite from dealumination but leads to a loss of the catalytic activity. 

Much experimental work has been performed using the copper-exchanged zeolite ZSM-5 (Cu-ZSM-5) as a catalyst for lean NOx reduction [3-7]. It shows high efficiency in the reduction of NOx by various hydrocarbons, even under oxygen in excess (10 %), especially in... 

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