Synthesis of Ammonium Cyanate and Urea by Reduction of Nitric Oxide on Platinum, Rhodium, and Ruthenium Catalysts

Abstract

Nearly quantitative conversion of nitric oxide (NO) into N(2)H(4)CO has been obtained in the reduction of NO with carbon monoxide and hydrogen over platinum and rhodium catalysts. Depending on the temperature of collection, N(2)H(4)CO is isolated as ammonium cyanate or its isomer, urea. The process is an effective way of recovering fixed nitrogen from dilute industrial streams containing NO. Ammonium cyanate may play a role in the reduction of NO in automotive exhaust control.

Behavior of Non-Promoted and Ceria-Promoted Pt/Rh and Pd/Rh Three-Way Catalysts under Steady State and Dynamic Operation of Hybrid Vehicles

“…In auto exhaust, NH 3 can be formed by the direct reaction of NO with H 2 , via the hydrolysis of an isocyanate intermediate, or by the direct reaction of NO with hydrogen produced via a water−gas shift reaction (WGSR) . In a study of the reduction of NO with a mixture of CO and H 2 in the presence of H 2 O and O 2 over supported Rh and Pt catalysts, Voorhoeve et al reported NH 3 formation via an isocyanate intermediate. By investigating the role of steam reforming and the water−gas shift reaction in the behavior of three-way catalysts, Whittington et al found that both reactions become important only at temperatures higher than those needed to facilitate oxidation (i.e., only when the monolithic catalyst bed is depleted of oxygen).…”

A framework for the analysis of the security of supply of utilising carbon dioxide as a chemical feedstock

“…It is useful to compare this process for the production of urea with an alternative that is based on the use of ruthenium as a catalyst. 35 In either case, the acceptability score ranked second overall. This is due to unfavourable CO 2 emissions by these processes.…”

Mechanistic Investigation of Deactivation of Ru/Al2O3 Catalyst for Preferential CO Oxidation in the Presence of NH3

“…On the other hand, the H 2 oxidation without CO, CO 2 , and H 2 O was rapidly suppressed (Figure 5a). Since it has been reported that NO reduction by CO was faster at low temperature (<270 °C) than that by H 2 , 25,33 NO was probably reduced to N 2 O and/or N 2 by CO. Tamaru et al reported that the NO reduction by H 2 was significantly suppressed by adsorbed oxygen, 28 which was consistent with our result that the H 2 oxidation was depressed by nitrosyls (Figure 5a) in contrast to the rapid reduction of nitrosyls under a reduction atmosphere. Compared with the rapid deactivation for the PROX in the presence of CO 2 and H 2 O (Figure 3b, 150 °C), the absence of H 2 O enhanced the activity for both CO and H 2 oxidation, which made most of the catalyst bed reductive and kept the catalyst active (Figure 5b).…”

“…Voorhoeve et al studied the reduction of NO over various Ru catalysts in a gas composition of 0.13 vol % CO, 0.4 vol % H 2 , 1.3 vol % CO, 3 vol % H 2 O, and 3 vol % CO 2 balanced with He at 150-500 °C. 33 They reported that N 2 O, N 2 , and NH 3 were exhausted at 150-200 °C. Thus N 2 O and N 2 was probably formed under a reduction atmosphere (Figure 9(6, 7), in addition to the NH 3 formation by the hydrolysis of isocyanates (Figure 9(2)).…”

“…A few studies on NH 3 oxidation − and CO−NH 3 reaction , over Ru/Al 2 O 3 catalysts have been reported. In addition, a lot of studies have been reported on the NO−CO, − NO−H 2 , ,− and NO−CO−H 2 reactions ,,− over Ru/Al 2 O 3 catalysts. However, the conditions for these reactions were quite different from that for the PROX, since the PROX is conducted in the presence of O 2 and H 2 O under a H 2 -rich condition.…”