Periodic Trends in Highly Dispersed Groups IV and V Supported Metal Oxide Catalysts for Alkene Epoxidation with H2O2

Nicholas E. Thornburg, Anthony B. Thompson, Justin M Notestein

Research output: Contribution to journalArticle

45 Citations (Scopus)

Abstract

Supported metal oxides are important catalysts for selective oxidation processes like alkene epoxidation with H2O2. The reactivity of these catalysts is dependent on both identity and oxide structure. The dependence of the latter on the synthesis method can confound attempts at comparative studies across the periodic table. Here, SiO2-supported metal oxide catalysts of Ti(IV), Zr(IV), Hf(IV), V(V), Nb(V), and Ta(V) (all of groups IV and V) were synthesized by grafting a series of related calixarene coordination complexes at surface densities less than ∼0.25 nm-2. Select catalysts were investigated by solid state NMR, UV-visible, and X-ray absorption near-edge spectroscopies. As-synthesized and calcined materials were examined for the epoxidation of cyclohexene and styrene (1.0 M) with H2O2 (0.10 M) at 45 and 65 °C. Nb catalysts emerge as high-performing materials, with calcined Nb-SiO2 proceeding at a cyclohexene turnover frequency of 2.4 min-1 (>2 times faster than Ti-SiO2) and with ∼85% selectivity toward direct (nonradical) epoxidation pathways. As-synthesized Zr, Hf, and Ta catalysts have improved direct pathway selectivities compared with their calcined versions, particularly evident for Ta-SiO2. Finally, when the materials are synthesized from these precursors but not simple metal chlorides, the direct pathway reaction rate correlates with Pauling electronegativities of the metals, demonstrating clear periodic trends in intrinsic Lewis acid catalytic behavior.

Original languageEnglish
Pages (from-to)5077-5088
Number of pages12
JournalACS Catalysis
Volume5
Issue number9
DOIs
Publication statusPublished - Jul 22 2015

Fingerprint

Epoxidation
Alkenes
Oxides
Olefins
Metals
Catalysts
Calixarenes
Lewis Acids
Electronegativity
Styrene
Catalyst selectivity
Coordination Complexes
X ray absorption
Reaction rates
Chlorides
Nuclear magnetic resonance
Spectroscopy
Oxidation
Acids

Keywords

  • calixarene
  • green chemistry
  • hydrogen peroxide
  • niobium
  • olefin epoxidation
  • supported catalyst
  • supported oxide

ASJC Scopus subject areas

  • Catalysis

Cite this

Periodic Trends in Highly Dispersed Groups IV and V Supported Metal Oxide Catalysts for Alkene Epoxidation with H2O2. / Thornburg, Nicholas E.; Thompson, Anthony B.; Notestein, Justin M.

In: ACS Catalysis, Vol. 5, No. 9, 22.07.2015, p. 5077-5088.

Research output: Contribution to journalArticle

@article{490b3d10fc464fbe882295247f7aa5a8,
title = "Periodic Trends in Highly Dispersed Groups IV and V Supported Metal Oxide Catalysts for Alkene Epoxidation with H2O2",
abstract = "Supported metal oxides are important catalysts for selective oxidation processes like alkene epoxidation with H2O2. The reactivity of these catalysts is dependent on both identity and oxide structure. The dependence of the latter on the synthesis method can confound attempts at comparative studies across the periodic table. Here, SiO2-supported metal oxide catalysts of Ti(IV), Zr(IV), Hf(IV), V(V), Nb(V), and Ta(V) (all of groups IV and V) were synthesized by grafting a series of related calixarene coordination complexes at surface densities less than ∼0.25 nm-2. Select catalysts were investigated by solid state NMR, UV-visible, and X-ray absorption near-edge spectroscopies. As-synthesized and calcined materials were examined for the epoxidation of cyclohexene and styrene (1.0 M) with H2O2 (0.10 M) at 45 and 65 °C. Nb catalysts emerge as high-performing materials, with calcined Nb-SiO2 proceeding at a cyclohexene turnover frequency of 2.4 min-1 (>2 times faster than Ti-SiO2) and with ∼85{\%} selectivity toward direct (nonradical) epoxidation pathways. As-synthesized Zr, Hf, and Ta catalysts have improved direct pathway selectivities compared with their calcined versions, particularly evident for Ta-SiO2. Finally, when the materials are synthesized from these precursors but not simple metal chlorides, the direct pathway reaction rate correlates with Pauling electronegativities of the metals, demonstrating clear periodic trends in intrinsic Lewis acid catalytic behavior.",
keywords = "calixarene, green chemistry, hydrogen peroxide, niobium, olefin epoxidation, supported catalyst, supported oxide",
author = "Thornburg, {Nicholas E.} and Thompson, {Anthony B.} and Notestein, {Justin M}",
year = "2015",
month = "7",
day = "22",
doi = "10.1021/acscatal.5b01105",
language = "English",
volume = "5",
pages = "5077--5088",
journal = "ACS Catalysis",
issn = "2155-5435",
publisher = "American Chemical Society",
number = "9",

}

TY - JOUR

T1 - Periodic Trends in Highly Dispersed Groups IV and V Supported Metal Oxide Catalysts for Alkene Epoxidation with H2O2

AU - Thornburg, Nicholas E.

AU - Thompson, Anthony B.

AU - Notestein, Justin M

PY - 2015/7/22

Y1 - 2015/7/22

N2 - Supported metal oxides are important catalysts for selective oxidation processes like alkene epoxidation with H2O2. The reactivity of these catalysts is dependent on both identity and oxide structure. The dependence of the latter on the synthesis method can confound attempts at comparative studies across the periodic table. Here, SiO2-supported metal oxide catalysts of Ti(IV), Zr(IV), Hf(IV), V(V), Nb(V), and Ta(V) (all of groups IV and V) were synthesized by grafting a series of related calixarene coordination complexes at surface densities less than ∼0.25 nm-2. Select catalysts were investigated by solid state NMR, UV-visible, and X-ray absorption near-edge spectroscopies. As-synthesized and calcined materials were examined for the epoxidation of cyclohexene and styrene (1.0 M) with H2O2 (0.10 M) at 45 and 65 °C. Nb catalysts emerge as high-performing materials, with calcined Nb-SiO2 proceeding at a cyclohexene turnover frequency of 2.4 min-1 (>2 times faster than Ti-SiO2) and with ∼85% selectivity toward direct (nonradical) epoxidation pathways. As-synthesized Zr, Hf, and Ta catalysts have improved direct pathway selectivities compared with their calcined versions, particularly evident for Ta-SiO2. Finally, when the materials are synthesized from these precursors but not simple metal chlorides, the direct pathway reaction rate correlates with Pauling electronegativities of the metals, demonstrating clear periodic trends in intrinsic Lewis acid catalytic behavior.

AB - Supported metal oxides are important catalysts for selective oxidation processes like alkene epoxidation with H2O2. The reactivity of these catalysts is dependent on both identity and oxide structure. The dependence of the latter on the synthesis method can confound attempts at comparative studies across the periodic table. Here, SiO2-supported metal oxide catalysts of Ti(IV), Zr(IV), Hf(IV), V(V), Nb(V), and Ta(V) (all of groups IV and V) were synthesized by grafting a series of related calixarene coordination complexes at surface densities less than ∼0.25 nm-2. Select catalysts were investigated by solid state NMR, UV-visible, and X-ray absorption near-edge spectroscopies. As-synthesized and calcined materials were examined for the epoxidation of cyclohexene and styrene (1.0 M) with H2O2 (0.10 M) at 45 and 65 °C. Nb catalysts emerge as high-performing materials, with calcined Nb-SiO2 proceeding at a cyclohexene turnover frequency of 2.4 min-1 (>2 times faster than Ti-SiO2) and with ∼85% selectivity toward direct (nonradical) epoxidation pathways. As-synthesized Zr, Hf, and Ta catalysts have improved direct pathway selectivities compared with their calcined versions, particularly evident for Ta-SiO2. Finally, when the materials are synthesized from these precursors but not simple metal chlorides, the direct pathway reaction rate correlates with Pauling electronegativities of the metals, demonstrating clear periodic trends in intrinsic Lewis acid catalytic behavior.

KW - calixarene

KW - green chemistry

KW - hydrogen peroxide

KW - niobium

KW - olefin epoxidation

KW - supported catalyst

KW - supported oxide

UR - http://www.scopus.com/inward/record.url?scp=84941104384&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84941104384&partnerID=8YFLogxK

U2 - 10.1021/acscatal.5b01105

DO - 10.1021/acscatal.5b01105

M3 - Article

VL - 5

SP - 5077

EP - 5088

JO - ACS Catalysis

JF - ACS Catalysis

SN - 2155-5435

IS - 9

ER -