Title: Methane Conversion to Ethylene and Aromatics on PtSn Catalysts

Abstract

Pt and PtSn catalysts supported on SiO₂ and H-ZSM-5 were studied for methane conversion under nonoxidative conditions. Addition of Sn to Pt/SiO₂ increased the turnover frequency for production of ethylene by a factor of 3, and pretreatment of the catalyst at 1123 K reduced the extent of coke formation. Pt and PtSn catalysts supported on H-ZSM-5 zeolite were prepared to improve the activity and selectivity to non-coke products. Ethylene formation rates were 20 times faster over a PtSn(1:3)/H-ZSM-5 catalyst with SiO₂:Al₂O₃ = 280 in comparison to those over PtSn(3:1)/SiO₂. H-ZSM-5-supported catalysts were also active for the formation of aromatics, and the rates of benzene and naphthalene formation were increased by using more acidic H-ZSM-5 supports. These catalysts operate through a bifunctional mechanism, in which ethylene is first produced on highly dispersed PtSn nanoparticles and then is subsequently converted to benzene and naphthalene on Brønsted acid sites within the zeolite support. The most active and stable PtSn catalyst forms carbon products at a rate, 2.5 mmol of C/((mol of Pt) s), which is comparable to that of state-of-the-art Mo/H-ZSM-5 catalysts with same metal loading operated under similar conditions (1.8 mmol of C/((mol of Mo) s)). Scanning transmission electron microscopy measurements suggestmore » the presence of smaller Pt nanoparticles on H-ZSM-5-supported catalysts, in comparison to SiO₂-supported catalysts, as a possible source of their high activity. As a result, a microkinetic model of methane conversion on Pt and PtSn surfaces, built using results from density functional theory calculations, predicts higher coupling rates on bimetallic and stepped surfaces, supporting the experimental observations that relate the high catalytic activity to small PtSn particles.« less

Authors:

Gerceker, Duygu ^[1]; Motagamwala, Ali Hussain ^[1]; Rivera-Dones, Keishla R. ^[1]; Miller, James B. ^[1]; Huber, George W. ^[1]; Mavrikakis, Manos  ^[1];

• Search DOE PAGES for author "Mavrikakis, Manos"
• Search DOE PAGES for ORCID "0000-0002-5293-5356"

Dumesic, James A.  ^[1]

• Search DOE PAGES for author "Dumesic, James A."
• Search DOE PAGES for ORCID "0000-0001-6542-0856"

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+ Show Author Affiliations

1. Univ. of Wisconsin-Madison, Madison, WI (United States)

Publication Date:

Wed Feb 15 00:00:00 EST 2017

Research Org.:

Univ. of Wisconsin, Madison, WI (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER); USDOE Office of Science (SC), Basic Energy Sciences (BES)

Contributing Org.:

US Air Force Office of Scientific Research (AFOSR); US Army Engineer Research and Development Center (ERDC); US Navy DoD Supercomputing Resource Center (Navy DSRC); Univ. of Wisconsin-Madison

OSTI Identifier:

1475188

Alternate Identifier(s):

OSTI ID: 1395572

Grant/Contract Number:  

SC0014058; FC02-07ER64494

Resource Type:

Accepted Manuscript

Journal Name:

ACS Catalysis

Additional Journal Information:

Journal Volume: 7; Journal Issue: 3; Journal ID: ISSN 2155-5435

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Aromatics; ethylene; H-ZSM-5; methane conversion; microkinetic model; particle size; platinum; tin; aromatics