Enhanced Rh-anchoring on the composite metal phosphate Y_0.33Zr₂(PO₄)₃in three-way catalysis

Abstract

Rh/Y0.33Zr2(PO4)3 formed a more thermostable bidentate interfacial linkage compared to the monodentate linkage that formed in Rh/ZrP2O7.

Metal–Support Interactions in Rhodium Catalysts Supported on Tetravalent Metal Pyrophosphates (MP2O7; M = Si, Ti, and Zr)

“…The strong first-shell peak at ∼2.0 Å was attributed to a Rh–O shell of RhO x , whereas the second shell peaks that differed from those for bulk Rh 2 O 3 implied interactions at the metal–support interface. Similar EXAFS results were obtained for Rh/ZrP 2 O 7 , Rh/AlPO 4 , and Rh/LaPO 4 in our previous studies, ,,, where detailed curve-fitting analysis suggested the contribution of a Rh–O–P at the interface between RhO x and metal phosphates. This model produced a fair fit to the as-prepared Rh/TiP 2 O 7 (Table ), supporting the RhO x –support bonding via the [P 2 O 7 ] unit.…”

“…Meanwhile, the supported Rh catalysts were prepared via impregnation of an aqueous solution of Rh­(NO 3 ) 3 (99.9% purity, Tanaka Precious Metals, Japan) followed by air drying at 100 °C and calcination at 600 °C (3 h). The metal loading (0.4 wt % as Rh metal) is a standard in a series of our previous studies and is similar to those in the commercial automotive three-way catalysts. − …”

“…(iv) The DFT calculation reveals that the Rh–O–P is more stable than Rh–O–M. The formation of interfacial Rh–O–P bonding has been confirmed to occur regardless of the metal elements (M) when Rh is supported on various metal orthophosphates (AlPO 4 , LnPO 4 , and Ln 0.33 Zr 2 (PO 4 ) 3 (Ln = rare earth)) and metal pyrophosphates (ZrP 2 O 7 ). ,,− …”

“…The electron deficiency in Rh influences the chemisorption of CO and NO and decreases the back-donation from the Rh d-orbitals to the π* molecular orbitals of these chemisorbed molecules, which is not conducive to the enhancement of the catalytic activity for CO and NO conversions. However, this negative impact of the acidity on the catalytic activity can be overcome by using basic metal phosphates such as LaPO 4 or more complex metal phosphates such as Y 0.33 Zr 2 (PO 4 ) 3 . Overall, the previous studies have been largely focused on orthophosphates, whereas the local structure and the nature of the interaction between Rh and pyrophosphates have not been studied in detail.…”

Role of Ba in an Al2O3‐Supported Pd‐based Catalyst under Practical Three‐Way Catalysis Conditions

“…Three‐way catalytic converters are widely used to control automotive emissions generated by gasoline vehicles [1–5] . Air pollutants, such as NO x , CO, and hydrocarbons (HCs), are reduced using three‐way catalysts that typically use platinum group metals (PGMs), such as Rh, Pd, and Pt, [6–14] which are beneficial for catalytic performance and durability compared to other non‐precious metals. Although catalysts that contain non‐noble metal components, such as Cu, Ni, and Fe, have recently been intensively studied, [15–21] real‐world operating systems still need large amounts of PGMs to meet strict regulations that require reductions of more than 99 % in tailpipe emissions relative to engine‐generated emissions [22] .…”