Distinct roles of copper in bimetallic copper–rhodium three-way catalysts deposited on redox supports

Abstract

Copper(4.7%)-rhodium(0-2000ppm) catalysts deposited on three supports with different oxygen storage capacity (OSC) were tested under three-way catalytic cycling conditions using a low frequency and large composition fluctuations. The reducibility by hydrogen was also studied for all the catalysts in order to assess their OSC. Alumina (Al), ceriaalumina (CeAl) and ceria-zirconia (CeZr) were selected as supports. Both copper and rhodium metals favour the reduction of CeAl and CeZr at low temperature. The catalytic activity of rhodium in CO, NO and C3H6 conversion in presence of oxygen is little influenced by the oxygen mobility of the support. However the OSC of the supports allow to attenuate or even suppress the effects of the composition fluctuations and thus improves the conversion at high temperatures. For monometallic copper catalysts, copper participates to the regulation of the oxidant/reducer ratio and is determinant if the support OSC is insufficient. Moreover, the interaction between copper and the mobile oxygen of the support greatly favours the CO oxidation at low temperature, whereas it has little influence on C3H6 oxidation and disfavours the NO reduction at low temperature. No synergetic effect was observed for the bimetallic CuRh catalysts. In this case, the activity is ruled by the metal or the association metal-support which is the most active in each temperature range. The association "copper-support exhibiting mobile oxygen" is the most active for CO conversion. NO reduction depends mainly on the rhodium content, especially at low temperature, and C3H6 conversion is a little improved by rhodium addition.

Effect of iron doping into CeO2–ZrO2 on the properties and catalytic behaviour of Pd-only three-way catalyst for automotive emission control

“…However, Pd-based catalysts display limitations with respect to their performance for NO reduction reactions [18,19]. In recent years, the introduction of transition metals into TWCs [20][21][22][23][24], which promoted the NO reduction and achieved the lower light-off temperature during the cold start phase, has earned much attention in Pd-based TWCs area [25][26][27].…”

The effect of Nd on the properties of ceria–zirconia solid solution and the catalytic performance of its supported Pd-only three-way catalyst for gasoline engine exhaust reduction

“…The molar ratio of Ce:Zr is 1:4, and the additive content of neodymia is 3, 5, 8 and 10 wt.% for CZN, respectively. The fresh supports calcined at 500 • C are named as CZNx (x = 3, 5,8,10), where x means the content of neodymia. All the supports were also calcined at 1100 • C for 4 h to investigate the effect of doping on the thermal stability of CZ, and the aged supports are referred to as CZa and CZNxa, respectively.…”

“…Among the several techniques that have been developed for reducing gasoline engine exhaust, catalytic converter is regarded as the most promising solution [3][4][5][6][7]. As the key component in catalytic converter, three-way catalyst (TWC) has been successfully used for the control and suppression of automotive emission by converting basic air pollutants like carbon monoxide, hydrocarbons and nitrogen oxides simultaneously.…”

Preparation Methods and Applications of CuO-CeO2 Catalysts: A Short Review

“…importance. Reactions of environmental importance include complete oxidation of CO [1][2][3][4][5][6][7][8][9][10], oxidation of hydrocarbon [1,[11][12][13][14], oxidation of VOC [15][16][17], NO reduction by CO [18,19], NO reduction by C3H6 [20,21], NO reduction by NH3 [22], three-way catalytic convertion [23], diesel soot oxidation [24][25][26][27][28], SO2 reduction by CO to elemental sulphur [29][30][31][32], ammonia decomposition [33,34], phenol oxidation [35][36], etc.…”

“…To date, there has been frequent most use of CuO-CeO2 systems as additives to reduce the cost of noble metals in the three-way catalysts [23], for the purification of automotive exhaust gas. An excellent activity of the CuO-CeO2 systems is on record in the oxidation of CO [1], which is significantly higher than that of the commercially precious forms of metal catalysts [76].…”