(755e) Controlled Synthesis of High Surface Area Pd and Pt/SiO2(core)@ZrO2(shell) Catalysts for Low Temperature Oxidation Applications | AIChE

(755e) Controlled Synthesis of High Surface Area Pd and Pt/SiO2(core)@ZrO2(shell) Catalysts for Low Temperature Oxidation Applications


Liu, C. H. - Presenter, University At Buffalo
Toops, T., Oak Ridge National Laboratory
Kyriakidou, E., SUNY at Buffalo
Chen, J., University At Buffalo

Synthesis of High Surface Area Pd and Pt/SiO2(core)@ZrO2(shell)
Catalysts for Low Temperature Oxidation Applications


text-align:center;line-height:normal"> 9.0pt;font-family:" times new roman>Chih Han Liu1, Junjie
Todd J. Toops2, Eleni A. Kyriakidou1,*

of Chemical and Biological Engineering, University at Buffalo, The State
University of New York, Buffalo, NY 14260, USA

Transportation Research Center, Oak Ridge National Laboratory, Oak Ridge, TN
37831, USA

text-align:center;line-height:normal"> font-family:" times new roman>*elenikyr@buffalo.edu

justify;text-justify:inter-ideograph;line-height:normal">Future diesel oxidation catalysts
will need to perform effectively at increasingly low exhaust temperatures; this
so-called “150ºC challenge” (i.e., achieve over 90% conversion below 150oC)
arises from continued improvements in engines efficiency.  Palladium supported
on ZrO2 catalysts have been tested for their low temperature diesel
oxidation performance where 50 and 90% conversions were achieved at 160, 180ºC
for CO and 180, 195ºC for C3H6, respectively [1] " times new roman>.  Uncontrolled incorporation of ZrO2 on
high surface area SiO2, resulted in incomplete coverage of SiO2
by ZrO2, leading to decreased performance compared to Pd/ZrO2
catalysts.  Complete coverage of SiO2 by ZrO2 was thus
introduced and SiO2(core)@ZrO2(shell) supports with an
enhanced surface area of 210 m2/g were synthesized [2] " times new roman>.  Herein, SiO2@ZrO2 supports
with controlled sizes were synthesized by varying the NH4OH
concentration and feed rate, resulting in SiO2@ZrO2
spheres with average diameters of 450 nm and 202 nm (Fig. 1A, B).  The surface
areas of the synthesized SiO2@ZrO2 supports increased with
decreasing SiO2@ZrO2 diameter: 147 and 293 m2/g
for SiO2@ZrO2 supports with 450 and 202 nm diameter,

catalytic performance of 1 wt.% Pd/SiO2@ZrO2 monometallic
catalysts was evaluated using the Crosscut Lean Exhaust Emissions Reduction
Simulations (CLEERS) protocol (333 mL/min, 12% O2, 6% H2O,
6% CO2, 400 ppm H2, 2000 ppm CO, 100 ppm NO, 250 ppm C2H4,
100 ppm C3H6 ,33.33 ppm C3H8 and
210 ppm C10H22, Ar balance) under degreened and
hydrothermally aged conditions [3] " times new roman>.  Comparable T50’s of CO were observed
over 1 wt. % Pd/SiO2@ZrO2 with 450 and 202 nm support
diameter, while Pd/SiO2@ZrO2 (202 nm) had a lower T50
of THCs by 17oC (Fig. 1C).  Improved performance was achieved after
hydrothermal aging at 800oC/10h, with the T50’s of 1 wt.
% Pd/SiO2@ZrO2 (450 nm) decreasing to 187oC
(CO) and 240ºC (THCs), while even lower T50’s (176oC
(CO), 222ºC (THCs)) were achieved over the smaller support diameter (202 nm) 1
wt. % Pd/SiO2@ZrO2 catalyst.  Monometallic 1.8 wt.%
Pt/SiO2@ZrO2, as well as bimetallic Pd-Pt/SiO2@ZrO2
catalysts with Pd/Pt ratios varying from 1/3 to 3 were synthesized for an
immediate comparison with the performance of 1 wt.% Pd/SiO2@ZrO2
This work illustrates the potential of developing Pd-based oxidation catalysts
with enhanced durability and low-temperature activity using SiO2@ZrO2
core@shell shaped mixed oxide supports with controlled sizes.


justify;text-justify:inter-ideograph;line-height:normal">Figure 1.  TEM image of SiO2@ZrO2
supports with (A) 450 nm (B) 202 nm diameters, and (C) T50,90 of 1
wt.% Pd/SiO2@ZrO2 catalysts with 202, 450 nm support
diameters evaluated with the simulated diesel exhaust CLEERS protocol.


[1] M.-Y. Kim, E.A.
Kyriakidou, J.-S. Choi, T.J. Toops, A.J. Binder, C. Thomas, J.E. Parks II, V.
Schwartz, J. Chen, D.K. Hensley, Appl. Catal., B, 187, 181-194 (2016).

[2] E.A.
Kyriakidou, T.J. Toops, J.-S. Choi, M.J. Lance, J.E. Parks II, US Patent
Publication US20180250659A1 (2018).

[3] Aftertreatment
Protocols for Catalyst Characterization and Performance Evaluation:
Low-Temperature Storage Catalyst Test Protocol:
https://cleers.org/wp-content/uploads/2018/03/2018_ LTAT _