Research Papers

Development of an Analytical Design Tool for Monolithic Emission Control Catalysts and Application to Nano-Textured Substrate System

[+] Author and Article Information
Chad A. Baker

Research and Advanced Engineering,
Ford Motor Company,
2151 Village Rd
Dearborn, MI 48124
e-mail: cbake134@ford.com

Alaattin Osman Emiroglu

Department of Mechanical Engineering,
Abant Izzet Baysal University,
Bolu 14100, Turkey
e-mail: aosmanemiroglu@gmail.com

Rehan Mallick

Department of Mechanical Engineering,
University of Texas at Austin,
204 E. Dean Keeton,
Austin, TX 78712
e-mail: rmallick6806@gmail.com

Ofodike A. Ezekoye

Department of Mechanical Engineering,
University of Texas at Austin,
204 E. Dean Keeton,
Austin, TX 78712
e-mail: dezekoye@mail.utexas.edu

Li Shi

Department of Mechanical Engineering,
University of Texas at Austin,
204 E. Dean Keeton,
Austin, TX 78712
e-mail: lishi@mail.utexas.edu

Matthew J. Hall

Department of Mechanical Engineering,
University of Texas at Austin,
204 E. Dean Keeton,
Austin, TX 78712
e-mail: mjhall@mail.utexas.edu

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF THERMAL SCIENCE AND ENGINEERING APPLICATIONS. Manuscript received December 5, 2012; final manuscript received February 14, 2014; published online April 11, 2014. Assoc. Editor: Ranganathan Kumar.

J. Thermal Sci. Eng. Appl 6(3), 031014 (Apr 11, 2014) (11 pages) Paper No: TSEA-12-1217; doi: 10.1115/1.4026944 History: Received December 05, 2012; Revised February 14, 2014

An analytical transport/reaction model was developed to simulate the catalytic performance of ZnO nanowires as a catalyst support. ZnO nanowires were chosen because they have easily characterized, controllable features and a spatially uniform morphology. The analytical model couples convection in the catalyst flow channel with reaction and diffusion in the porous substrate material; it was developed to show that a simple analytical model with physics-based mass transport and empirical kinetics can be used to capture the essential physics involved in catalytic conversion of hydrocarbons. The model was effective at predicting species conversion efficiency over a range of temperature and flow rate. The model clarifies the relationship between advection, bulk diffusion, pore diffusion, and kinetics. The model was used to optimize the geometry of the experimental catalyst for which it predicted that maximum species conversion density for fixed catalyst surface occurred at a channel height of 520 μm.

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Fig. 1

Schematic of catalyst test rig

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Fig. 2

Schematic of alumina sample holder

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Fig. 3

SEM image of nanowires grown on Si wafer. Scale bar is 1 μm.

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Fig. 4

TEM image of nanowire after being sputter coated with 1 nm Pt/Pd. Scale bar is 10 nm.

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Fig. 8

Schematic of catalyst model with coordinate system defined. Not to scale.

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Fig. 7

Plot of conversion efficiency versus temperature for three flow rates for Si wafers coated with nanowires with 10 nm Pt/Pd sputter deposition thickness.

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Fig. 6

SEM images showing how Pt/Pd agglomeration is affected by sputter thickness. Scale bars are 100 nm.

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Fig. 5

Plot of conversion efficiency versus Pt/Pd loading on nanowires at 450 °C and 500 sccm.

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Fig. 9

Nondimensional parameters and corresponding rate-limiting mechanisms

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Fig. 10

Plot of hydrocarbon conversion efficiency versus temperature comparing performance of catalyst with control experiment

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Fig. 11

Parameterized plot showing hydrocarbon conversion efficiency as a function of temperature for various flow rates for experimental and modeling results. Values of Da, Peh, and ϕ for select temperatures are shown in Table 3.

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Fig. 12

Plot of conversion efficiency per unit volume versus channel height. Channel height is the vertical distance between adjacent catalyst plates. The baseline flow velocity was 16.7 cm/s and the temperature was 400 °C.

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Fig. 13

Contour plots showing species concentration profile as a function of x˜ and y˜ for one-term and four-term Fourier series solutions as well as the numerical solution for a fully developed parabolic flow. V·=500sccm and T = 400 °C.

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Fig. 14

Plot showing predicted conversion efficiency for the numerical model that accounts for fully developed parabolic flow and the analytical model using 1 to 10 terms. V·=500sccm.



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