Showing papers by "Masakazu Iwamoto published in 1991"

Removal of nitrogen monoxide through a novel catalytic process. 1. Decomposition on excessively copper-ion-exchanged ZSM-5 zeolites

Abstract: Repeated ion exchange of the ZSM-5 zeolite using aqueous copper(II) acetate solution was found to bring about excess loading of copper ions above an exchange level of 100%. The high activity of the resulting catalyst for NO decomposition was consistent for at least 30 h even at short contact time and low NO pressure. The number of copper ions that can adsorb NO molecules has been determined by a temperature-programmed desorption technique combined with IR measurement; 94% of Cu{sup 2+} ions in ZSM-5 were active for the adsorption. The activity of excessively copper ion exchanged ZSM-5 zeolite was slightly reduced by the oxygen in the feed gas while that of zeolite, of which the loading amount of copper was less than 100%, was greatly diminished under the same condition. SO{sub 2} completely poisons the activity at 673-923 K, but the activity can be regenerated at the higher temperature treatment.

Cu-ZSM-5 zeolite as highly active catalyst for removal of nitrogen monoxide from emission of diesel engines

Abstract: The catalytic activity of alumina for the title reaction has been found to be greatly improved by the loading of copper. The addition of copper resulted in lowering the active temperature region, the higher maximum activity, and the enhancement of the reaction rate. The maximum effect was observed at 0.3 wt% of the loading amount of copper. A similar enhancement was also confirmed on SiO2-Al2O3.

Enhancement of catalytic activity of alumina by copper addition for selective reduction of nitrogen monoxide by ethene in oxidizing atmosphere

Abstract: The catalytic activity of alumina for the title reaction has been found to be greatly improved by the loading of copper. The addition of copper resulted in lowering the active temperature region, the higher maximum activity, and the enhancement of the reaction rate. The maximum effect was observed at 0.3 wt% of the loading amount of copper. A similar enhancement was also confirmed on SiO2-Al2O3.

Removal of Nitrogen Monoxide over Copper Ion-exchanged Zeolite Catalysts

Abstract: Direct decomposition and selective reduction of nitrogen monoxide over copper ion-exchanged zeolite catalysts are proposed as new methods for removal of NO. The copper ion-exchanged ZSM-5 zeolite (Cu-Z) was the most active catalyst for decomposition of NO. The activity of Cu-Z zeolites increased with increase in the exchange level. The zeolites with copper ion-excange levels of 100% or more, which could be prepared by repeating ion exchange of the ZSM-5 zeolite using aqueous copper(II) acetate solution or addition of ammonia into the aqueous copper(II) nitrate solution, showed significantly high activity even in the presence of oxygen and at high GHSV region. It was clarified concerning Cu-Z, by using IR, ESR, phosphorescence, TPD, and CO adsorption measurements that (1) the Cu2+ ions exchanged into zeolite were reduced to Cu+ and/or Cu+-Cu+ through evacuation at elevated temperature, (2) after exposure to oxygen at 773K and subsequent evacuation, about 40% copper ions in zeolite existed as Cu+ ions, (3) the NO- species formed by adsorption of NO on Cu+ would be an intermediate in the NO decomposition, and (4) redox cycle of Cu+_??_Cu2+ in the zeolite is probably a key step to achieve the decomposition reaction. Selective reduction of NO by hydrocarbon in the presence of oxygen was first found by the authors and Cu-Z was remarkably effective for NO removal at temperatures as low as 523-673K. The activity for this selective reduction in NO+C3H6+O2 system was not poisoned very much by addition of SO2. The conversion into N2 was changed to 85% (773K) in the presence of SO2, from 100% in the absence of SO2, which is in contrast with the fact that the catalytic activity for direct decomposition NO was completely lost on adding the same amount of SO2. Furthermore, the reduction rate over Cu-Z at 573K was higher than those over H-zeolite and alumina catalysts at 723 and 773K, respectively, which have been reported to be active, after findings by the authors.

Copper Ion-exchanged Zeolites as Active Catalysts for Direct Decomposition of Nitrogen Monoxide

Abstract: The exhaust gases from vehicle engines and industrial boilers contain considerable amounts of harmful nitrogen monoxide (NO). To remove NO, catalytic reduction processes using NH 3 , CO or hydrocarbons have been applied, but several problems remain to be solved. It is suggested here that a catalytic decomposition process be used for NO removal. The catalytic performance of copper ionexchanged zeolites for NO decomposition is summarized. Maximum activity was observed around 823–376 K. From the correlation among the zeolite structure, the aluminum content, exchange level of copper ions, and the catalytic activity, it follows that the zeolite structure would be the factor determining the effectiveness of Cu 2+ ions, and the catalytic activity of the effective Cu 2+ ion is probably controlled by the Al content. A reaction mechanism is then suggested on the basis of IR, ESR, phosphorescence, temperature programmed desorption, and kinetic data.

Cu‐ZSM‐5 Zeolite as Highly Active Catalyst for Removal of Nitrogen Monoxide from Emission of Diesel Engines.

Abstract: Copper ion-exchanged ZSM-5 zeolite is the most active for the selective reduction of nitric oxide by ethene in the presence of oxygen at temperatures as low as 437–

Direct Amination of 2-Methylpropene with Ammonia into t-Butylamine on Proton-exchanged ZSM-5 Zeolite Catalyst

Abstract: Proton-exchanged ZSM-5 zeolite with silica/alumina = 51 showed a pronounced catalytic activity for the title reaction and it was suggested that this reaction would proceed on Bronsted acid site.

One-step formation of ethyl methyl ketone from 1-butene and water on ultrastable Y-type zeolite catalyst

Abstract: Proton exchanged ultrastable Y-type zeolite with silica/alumina = 40 showed a pronounced catalytic activity for the formation of ethyl methyl ketone directly from 1-butene and water. The formation rate of ethyl methyl ketone was much higher than those on MoO3-based catalysts in the oxidation of 1-butene by oxygen. It was suggested that the basic site necessary for the formation of ethyl ketone directly from 1-butene and water would be the pentacoordinated Al.