%0 Journal Article
%A Nagao, Yuki
%A Nakahara, Yunosuke
%A Sato, Takahiro
%A Iwakura, Hironori
%A Takeshita, Shoya
%A Minami, Saki
%A Yoshida, Hiroshi
%A Machida, Masato
%D 2015
%T Rh/ZrP2O7 as an Efficient Automotive
Catalyst for NOx Reduction under Slightly
Lean Conditions
%U https://acs.figshare.com/articles/journal_contribution/Rh_ZrP_sub_2_sub_O_sub_7_sub_as_an_Efficient_Automotive_Catalyst_for_NO_sub_i_x_i_sub_Reduction_under_Slightly_Lean_Conditions/2189014
%R 10.1021/cs5020157.s001
%2 https://acs.figshare.com/ndownloader/files/3823180
%K Rh
%K reactive aldehyde species
%K C 3H oxidation
%K ZrP 2O
%K ZrO 2
%K Efficient Automotive Catalyst
%K YPO
%X The
three-way catalyst performances of honeycomb-coated Rh catalysts
were studied on several metal phosphate supports (AlPO4, YPO4, ZrP2O7, and LaPO4) using various simulated exhausts with different air-to-fuel ratios
(A/F). These supports significantly
improved the NOx purification (deNOx) efficiency under slightly lean conditions
(14.6 < A/F ≤ 15.3) as
compared with conventional Rh/ZrO2 catalysts. The deNOx activity exhibited the following sequence
of increasing the mean electronegativity of the supports: ZrO2 < YPO4 < LaPO4 < AlPO4 < ZrP2O7. Although both NO–CO
and NO–C3H6 reactions contributed to
the deNOx process, the latter reaction
was more favored on Rh/ZrP2O7 than on Rh/ZrO2. Partially oxidized C3H6 was adsorbed
on Rh/ZrP2O7 in the form of reactive aldehyde
species, in contrast to the less-reactive carboxylate species adsorbed
on Rh/ZrO2. Furthermore, Rh oxide was more easily reduced
to the active metallic state on ZrP2O7 compared
with Rh/ZrO2 when the atmosphere was changed from lean
(A/F > 14.6) to rich (A/F < 14.6). Metallic Rh formed on ZrP2O7 was only slowly oxidized on exposure to excess
O2, whereas Rh on ZrO2 was readily oxidized
to less-active
Rh2O3. The high activity of Rh/ZrP2O7 toward C3H6 oxidation via aldehyde
species as well as the resistance of metallic Rh against reoxidation
are considered to be possible reasons for the enhanced deNOx performance of this catalyst in a slightly lean
region.
%I ACS Publications