340
J. Handzlik
33. Lee EL, Wachs IE (2008) In situ Raman spectroscopy of SiO 2 -supported transition metal
oxide catalysts: an isotopic 18 O− 16 O exchange study. J Phys Chem C 112:6487–6498
34. Chakrabarti A, Wachs IE (2015) The nature of surface CrO x sites on SiO 2 in different environments. Catal Lett 145:985–994
35. Peek NM, Jeffcoat DB, Moisii C, van de Burgt L, Profeta S, Scott SL, Stiegman AE (2018)
Reassessment of the electronic structure of Cr(VI) sites supported on amorphous silica and
implications for Cr coordination number. J Phys Chem C 122:4349–4358
36. Moisii C, Jeffcoat D, Peek N, van de Burgt L, Scott SL, Stiegman AE (2018) Do monooxo sites exist in silica-supported Cr(VI) materials? Reassessment of the resonance Raman
spectra. J Phys Chem C 122:17149–17160
37. Gaspar AB, Martins RL, Schmal M, Dieguez LC (2001) Characterization of Cr 2+ and ethylene
polymerization on Cr/SiO 2 catalysts. J Mol Catal A Chem 169:105–112
38. Groppo E, Damin A, Otero Arean C, Zecchina A (2011) Enhancing the initial rate of polymerisation of the reduced Phillips catalyst by one order of magnitude. Chem Eur J 17:11110–11114
39. Brown C, Krzystek J, Achey R, Lita A, Fu R, Meulenberg RW, Polinski M, Peek N, Wang
Y, van de Burgt LJ, Profeta S, Stiegman AE, Scott SL (2015) Mechanism of initiation in
the Phillips ethylene polymerization catalyst: redox processes leading to the active site. ACS
Catal 5:5574–5583
40. Chakrabarti A, Gierada M, Handzlik J, Wachs IE (2016) Operando molecular spectroscopy
during ethylene polymerization by supported CrO x /SiO 2 catalysts: active sites, reaction intermediates, and structure-activity relationship. Top Catal 59:725–739
41. Barzan C, Piovano A, Braglia L, Martino GA, Lamberti C, Bordiga S, Groppo E (2017) Ligands make the difference! Molecular insights into Cr VI /SiO 2 Phillips catalyst during ethylene
polymerization. J Am Chem Soc 139:17064–17073
42. Weckhuysen BM, De Ridder LM, Schoonheydt RA (1993) A quantitative diffuse reflectance
spectroscopy study of supported chromium catalysts. J Phys Chem 97:4756–4763
43. Liu B, Nakatani H, Terano M (2002) New aspects of the induction period of ethene polymerization using Phillips CrO x /SiO 2 catalyst probed by XPS, TPD and EPMA. J Mol Catal A
Chem 184:387–398
44. Budnyk A, Damin A, Groppo E, Zecchina A, Bordiga S (2015) Effect of surface hydroxylation
on the catalytic activity of a Cr(II)/SiO 2 model system of Phillips catalyst. J Catal 324:79–87
45. Weckhuysen BM, De Ridder LM, Grobet PJ, Schoonheydt RA (1995) Redox behavior and
dispersion of supported chromium catalysts. J Phys Chem 99:320–326
46. Weckhuysen BM, Schoonheydt RA, Mabbs FE, Collison D (1996) Electron paramagnetic
resonance of heterogeneous chromium catalysts. J Chem Soc Faraday Trans 92:2431–2436
47. Brown C, Lita A, Tao Y, Peek N, Crosswhite M, Mileham M, Krzystek J, Achey R, Fu R,
Bindra JK, Polinski M, Wang Y, van de Burgt LJ, Jeffcoat D, Profeta S, Stiegman AE, Scott
SL (2017) Mechanism of initiation in the Phillips ethylene polymerization catalyst: ethylene
activation by Cr(II) and the structure of the resulting active site. ACS Catal 7:7442–7455
48. Espelid Ø, Børve KJ (2001) Theoretical analysis of d-d transitions for the reduced Cr/silica
system. Catal Lett 75:49–54
49. Espelid Ø, Børve KJ (2002) Theoretical analysis of CO adsorption on the reduced Cr/silica
system. J Catal 205:177–190
50. Damin A, Vitillo JG, Ricchiardi G, Bordiga S, Lamberti C, Groppo E, Zecchina A (2009)
Modeling CO and N 2 adsorption at Cr surface species of Phillips catalyst by hybrid density
functionals: effect of Hartree-Fock exchange percentage. J Phys Chem A 113:14261–14269
51. Demmelmaier CA, White RE, van Bokhoven JA, Scott SL (2008) Nature of ≡SiOCrO 2 Cl and
(≡SiO) 2 CrO 2 sites prepared by grafting CrO 2 Cl 2 onto silica. J Phys Chem C 112:6439–6449
52. Demmelmaier CA, White RE, van Bokhoven JA, Scott SL (2009) Evidence for a chromasiloxane ring size effect in Phillips (Cr/SiO 2 ) polymerization catalysts. J Catal 262:44–56
53. Zhong L, Lee M-Y, Liu Z, Wanglee Y-J, Liu B, Scott SL (2012) Spectroscopic and structural characterization of Cr(II)/SiO 2 active site precursors in model Phillips polymerization
catalysts. J Catal 293:1–12
J. Handzlik
33. Lee EL, Wachs IE (2008) In situ Raman spectroscopy of SiO 2 -supported transition metal
oxide catalysts: an isotopic 18 O− 16 O exchange study. J Phys Chem C 112:6487–6498
34. Chakrabarti A, Wachs IE (2015) The nature of surface CrO x sites on SiO 2 in different environments. Catal Lett 145:985–994
35. Peek NM, Jeffcoat DB, Moisii C, van de Burgt L, Profeta S, Scott SL, Stiegman AE (2018)
Reassessment of the electronic structure of Cr(VI) sites supported on amorphous silica and
implications for Cr coordination number. J Phys Chem C 122:4349–4358
36. Moisii C, Jeffcoat D, Peek N, van de Burgt L, Scott SL, Stiegman AE (2018) Do monooxo sites exist in silica-supported Cr(VI) materials? Reassessment of the resonance Raman
spectra. J Phys Chem C 122:17149–17160
37. Gaspar AB, Martins RL, Schmal M, Dieguez LC (2001) Characterization of Cr 2+ and ethylene
polymerization on Cr/SiO 2 catalysts. J Mol Catal A Chem 169:105–112
38. Groppo E, Damin A, Otero Arean C, Zecchina A (2011) Enhancing the initial rate of polymerisation of the reduced Phillips catalyst by one order of magnitude. Chem Eur J 17:11110–11114
39. Brown C, Krzystek J, Achey R, Lita A, Fu R, Meulenberg RW, Polinski M, Peek N, Wang
Y, van de Burgt LJ, Profeta S, Stiegman AE, Scott SL (2015) Mechanism of initiation in
the Phillips ethylene polymerization catalyst: redox processes leading to the active site. ACS
Catal 5:5574–5583
40. Chakrabarti A, Gierada M, Handzlik J, Wachs IE (2016) Operando molecular spectroscopy
during ethylene polymerization by supported CrO x /SiO 2 catalysts: active sites, reaction intermediates, and structure-activity relationship. Top Catal 59:725–739
41. Barzan C, Piovano A, Braglia L, Martino GA, Lamberti C, Bordiga S, Groppo E (2017) Ligands make the difference! Molecular insights into Cr VI /SiO 2 Phillips catalyst during ethylene
polymerization. J Am Chem Soc 139:17064–17073
42. Weckhuysen BM, De Ridder LM, Schoonheydt RA (1993) A quantitative diffuse reflectance
spectroscopy study of supported chromium catalysts. J Phys Chem 97:4756–4763
43. Liu B, Nakatani H, Terano M (2002) New aspects of the induction period of ethene polymerization using Phillips CrO x /SiO 2 catalyst probed by XPS, TPD and EPMA. J Mol Catal A
Chem 184:387–398
44. Budnyk A, Damin A, Groppo E, Zecchina A, Bordiga S (2015) Effect of surface hydroxylation
on the catalytic activity of a Cr(II)/SiO 2 model system of Phillips catalyst. J Catal 324:79–87
45. Weckhuysen BM, De Ridder LM, Grobet PJ, Schoonheydt RA (1995) Redox behavior and
dispersion of supported chromium catalysts. J Phys Chem 99:320–326
46. Weckhuysen BM, Schoonheydt RA, Mabbs FE, Collison D (1996) Electron paramagnetic
resonance of heterogeneous chromium catalysts. J Chem Soc Faraday Trans 92:2431–2436
47. Brown C, Lita A, Tao Y, Peek N, Crosswhite M, Mileham M, Krzystek J, Achey R, Fu R,
Bindra JK, Polinski M, Wang Y, van de Burgt LJ, Jeffcoat D, Profeta S, Stiegman AE, Scott
SL (2017) Mechanism of initiation in the Phillips ethylene polymerization catalyst: ethylene
activation by Cr(II) and the structure of the resulting active site. ACS Catal 7:7442–7455
48. Espelid Ø, Børve KJ (2001) Theoretical analysis of d-d transitions for the reduced Cr/silica
system. Catal Lett 75:49–54
49. Espelid Ø, Børve KJ (2002) Theoretical analysis of CO adsorption on the reduced Cr/silica
system. J Catal 205:177–190
50. Damin A, Vitillo JG, Ricchiardi G, Bordiga S, Lamberti C, Groppo E, Zecchina A (2009)
Modeling CO and N 2 adsorption at Cr surface species of Phillips catalyst by hybrid density
functionals: effect of Hartree-Fock exchange percentage. J Phys Chem A 113:14261–14269
51. Demmelmaier CA, White RE, van Bokhoven JA, Scott SL (2008) Nature of ≡SiOCrO 2 Cl and
(≡SiO) 2 CrO 2 sites prepared by grafting CrO 2 Cl 2 onto silica. J Phys Chem C 112:6439–6449
52. Demmelmaier CA, White RE, van Bokhoven JA, Scott SL (2009) Evidence for a chromasiloxane ring size effect in Phillips (Cr/SiO 2 ) polymerization catalysts. J Catal 262:44–56
53. Zhong L, Lee M-Y, Liu Z, Wanglee Y-J, Liu B, Scott SL (2012) Spectroscopic and structural characterization of Cr(II)/SiO 2 active site precursors in model Phillips polymerization
catalysts. J Catal 293:1–12