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Title: A Theoretical Study of Methanol Oxidation on RuO 2(110): Bridging the Pressure Gap

Abstract

Partial oxidation catalysis is often fraught with selectivity problems, largely because there is a tendency of oxidation products to be more reactive than the starting material. One industrial process that has successfully overcome this problem is partial oxidation of methanol to formaldehyde. This process has become a global success, with an annual production of 30 million tons. Although ruthenium catalysts have not shown activity as high as the current molybdena or silver-based industrial standards, the study of ruthenium systems has the potential to elucidate which catalyst properties facilitate the desired partial oxidation reaction as opposed to deep combustion due to a pressure-dependent selectivity “switch” that has been observed in ruthenium-based catalysts. In this work, we find that we are able to successfully rationalize this “pressure gap” using near-ab initio steady-state microkinetic modeling on RuO 2(110). We obtain molecular desorption prefactors from experiment and determine all other energetics using density functional theory. We show that, under ambient pressure conditions, formaldehyde production is favored on RuO 2(110), whereas under ultrahigh vacuum pressure conditions, full combustion to CO 2 takes place. We glean from our model several insights regarding how coverage effects, oxygen activity, and rate-determining steps influence selectivity and activity. As amore » result, we believe the understanding gained in this work might advise and inspire the greater partial oxidation community and be applied to other catalytic processes which have not yet found industrial success.« less

Authors:
 [1]; ORCiD logo [2];  [2]
  1. Stanford Univ., Stanford, CA (United States)
  2. Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1390312
Grant/Contract Number:
AC02-76SF00515; 32 CFR 168a
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
ACS Catalysis
Additional Journal Information:
Journal Volume: 7; Journal Issue: 7; 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; density functional theory; formaldehyde; methanol; pressure gap; ruthenium; selective oxidation

Citation Formats

Latimer, Allegra A., Abild-Pedersen, Frank, and Norskov, Jens K.. A Theoretical Study of Methanol Oxidation on RuO2(110): Bridging the Pressure Gap. United States: N. p., 2017. Web. doi:10.1021/acscatal.7b01417.
Latimer, Allegra A., Abild-Pedersen, Frank, & Norskov, Jens K.. A Theoretical Study of Methanol Oxidation on RuO2(110): Bridging the Pressure Gap. United States. doi:10.1021/acscatal.7b01417.
Latimer, Allegra A., Abild-Pedersen, Frank, and Norskov, Jens K.. 2017. "A Theoretical Study of Methanol Oxidation on RuO2(110): Bridging the Pressure Gap". United States. doi:10.1021/acscatal.7b01417.
@article{osti_1390312,
title = {A Theoretical Study of Methanol Oxidation on RuO2(110): Bridging the Pressure Gap},
author = {Latimer, Allegra A. and Abild-Pedersen, Frank and Norskov, Jens K.},
abstractNote = {Partial oxidation catalysis is often fraught with selectivity problems, largely because there is a tendency of oxidation products to be more reactive than the starting material. One industrial process that has successfully overcome this problem is partial oxidation of methanol to formaldehyde. This process has become a global success, with an annual production of 30 million tons. Although ruthenium catalysts have not shown activity as high as the current molybdena or silver-based industrial standards, the study of ruthenium systems has the potential to elucidate which catalyst properties facilitate the desired partial oxidation reaction as opposed to deep combustion due to a pressure-dependent selectivity “switch” that has been observed in ruthenium-based catalysts. In this work, we find that we are able to successfully rationalize this “pressure gap” using near-ab initio steady-state microkinetic modeling on RuO2(110). We obtain molecular desorption prefactors from experiment and determine all other energetics using density functional theory. We show that, under ambient pressure conditions, formaldehyde production is favored on RuO2(110), whereas under ultrahigh vacuum pressure conditions, full combustion to CO2 takes place. We glean from our model several insights regarding how coverage effects, oxygen activity, and rate-determining steps influence selectivity and activity. As a result, we believe the understanding gained in this work might advise and inspire the greater partial oxidation community and be applied to other catalytic processes which have not yet found industrial success.},
doi = {10.1021/acscatal.7b01417},
journal = {ACS Catalysis},
number = 7,
volume = 7,
place = {United States},
year = 2017,
month = 5
}

Journal Article:
Free Publicly Available Full Text
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  • A theoretical model has been developed for describing isolated vanadate species dispersed on the (101) surface of anatase that takes into account the equilibration of the supported species with gas-phase oxygen. The lowest energy of the combined solid and gas phases identifies the VOx species with the optimal structure and composition. This model of VOx species supported on the surface of anatase is then used to analyze the reaction path for methanol oxidation to formaldehyde. The chemisorption of methanol is found to proceed preferentially by addition across a V-O-Ti bond to form V-OCH3 and Ti-OH species. The rate-limiting step formore » the formation of formaldehyde takes place via the transfer of a hydrogen atom from V-OCH3 bound to an oxygen atom bridging two Ti atoms, i.e., a Ti-O-Ti group located adjacent to the supported vanadate species. This step is found to have the lowest apparent activation energy of all pathways explored for the formation of formaldehyde.« less
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