I.r. spectroscopic evidence of formyl species formed by CO and H<sub>2</sub>Co-adsorption on ZnO and Cu–ZnO

Saussey, J.; Lavalley, Jean‐Claude; Lamotte, J.; Raïs, T.

doi:10.1039/c39820000278

Cited by 64 publications

(37 citation statements)

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“…Other studies have shown that, on Cu/ZnO catalysts, CO 2 /H 2 mixtures produce a formate species that is an intermediate to CH 3 OH on both Cu and ZnO surfaces, but that CO/H 2 mixtures produce formate only on the ZnO support surface [8,[38][39][40][41][42][43]. SiO 2 has few hydroxyl groups, but slow methanation side reactions (Eq.…”

Section: Discussionmentioning

confidence: 99%

New insights into methanol synthesis catalysts from X-ray absorption spectroscopy

Meitzner¹,

Iglesia

1999

Catalysis Today

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X-ray absorption spectroscopic studies from several different groups provide a consistent structural picture of methanol synthesis catalysts. Copper metal is the principal Cu species detected in all in-situ XAS studies. A small amount of Cu(II) persisted in many samples reduced below 600 K, but it appears to be catalytically irrelevant. Cu(I) was not detected in any of the in-situ XAS studies. The Zn structure did not change in response to chemical treatments in any of the ZnO-containing methanol synthesis catalysts.We conclude that the slow approach to steady-state rate of methanol synthesis from CO/H 2 mixtures cannot result from changes in the Cu metal component of Cu/SiO 2 catalysts. By eliminating this possibility, we provide indirect evidence for the proposal that initial induction periods reflect slow changes in the surface of the SiO 2 or ZnO component in the catalysts. A bifunctional mechanism involving the formation of formate from CO on support hydroxyl groups would increase methanol synthesis rates as OH groups are formed by hydrolysis of Si-O bonds using the H 2 O formed in slow methanation side reactions. The bifunctional mechanism is not required for the synthesis of methanol from CO 2 -containing mixtures, because formate can form on Cu directly from CO 2 and H 2 .

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Section: Discussionmentioning

confidence: 99%

New insights into methanol synthesis catalysts from X-ray absorption spectroscopy

Meitzner¹,

Iglesia

1999

Catalysis Today

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“…IR bands due to Mn nþ -CO surface complexes have been recorded at 2213-2172 cm À1 [20][21][22][23][24][25][26][27][28] and at 2144-2114 cm À1 [21,22,29]. These vibrations are generally assigned to Mn 2þ -CO species [20,23,24] but some authors [21,25,29] have reported that they characterise Mn 3þ -CO carbonyls.…”

Section: Introductionmentioning

confidence: 99%

FTIR study of low-temperature CO adsorption on Mn-ZSM-5 and MnY zeolites. Effect of the zeolite matrix on the formation of Mn2+(CO) geminal species

Hadjiivanov

Ivanova

Kantcheva

et al. 2002

Catalysis Communications

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Adsorption of CO on Mn-ZSM-5 zeolite at 85 K results in formation of physically adsorbed CO, several kinds of Hbonded CO and Mn 2þ ðCOÞ x geminal species ð2202 cm À1 Þ. Decreasing the coverage during evacuation results in disappearance of the physically adsorbed CO and the H-bonded forms and in conversion of the dicarbonyls to linear Mn 2þ -CO species ð2214 cm À1 Þ. The latter are quite stable at 85 K. Coadsorption 12 CO and 13 CO reveals that the CO molecules in the geminal polycarbonyls behave as independent oscillators. In contrast, CO adsorption at 85 K on MnNaY zeolite only leads to formation of linear Mn 2þ -CO species (2210 cm À1 ) and mono-and di-carbonyls associated with residual sodium cations. The results are interpreted as evidence that site-specified geminal carbonyls are formed with cations possessing an ionic radius bigger than a critical value. This value is different for different positions in various zeolites and is bigger for cations in S II positions in Y zeolites than is the case of cations in a ZSM-5 matrix. Ó

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“…Methanol synthesis is believed to involve the hydrogenation of formyl intermediates on the catalyst surface, which are formed by CO insertion into a metal hydride, as shown in Fig.3 (Route I) [12][13][14]. Tetrahydroquinoline, with a lone pair of electrons on the nitrogen atom, is an active nucleophile.…”

Section: Discussionmentioning

confidence: 99%

Promoted Zinc Chromite Catalysts for Higher Alcohol Synthesis

Sun¹,

Roberts²

2001

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This report describes the analytical protocols that were developed during the last two years to analyze "spent" THQ (tetrahydroquinoline) slurry liquid. Identification of the components of the "spent" THQ should help to understand the influence of the slurry medium on the methanol synthesis reaction, and on other reactions with THQ as the slurry liquid.Silica gel liquid chromatography and high performance liquid chromatography (HPLC) were used to isolate and purify the major compounds in the "spent" slurry liquid. Gas chromatography/mass spectroscopy (GC/MS), Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) were applied to identify the major compounds. Methyl -, dimethyl -, and trimethyl -THQ were found to comprise more than 80% of the "spent" liquid. The balance was various methylated indoles. A methyl group always is attached to the N atom in the ring structure. Speculative mechanisms are presented that may help to understand the interaction between the catalyst and the alkylated THQ slurry liquid, and the effect of liquid composition on the methanol synthesis reaction.A poster entitled "Promoted Zinc Chromite Catalyst for Higher Alcohol Synthesis in a Slurry Reactor -2. Spent Liquid Analysis" was presented at the

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I.r. spectroscopic evidence of formyl species formed by CO and H₂Co-adsorption on ZnO and Cu–ZnO

Cited by 64 publications

References 1 publication

New insights into methanol synthesis catalysts from X-ray absorption spectroscopy

New insights into methanol synthesis catalysts from X-ray absorption spectroscopy

FTIR study of low-temperature CO adsorption on Mn-ZSM-5 and MnY zeolites. Effect of the zeolite matrix on the formation of Mn2+(CO) geminal species

Promoted Zinc Chromite Catalysts for Higher Alcohol Synthesis

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I.r. spectroscopic evidence of formyl species formed by CO and H2Co-adsorption on ZnO and Cu–ZnO

Cited by 64 publications

References 1 publication

New insights into methanol synthesis catalysts from X-ray absorption spectroscopy

New insights into methanol synthesis catalysts from X-ray absorption spectroscopy

FTIR study of low-temperature CO adsorption on Mn-ZSM-5 and MnY zeolites. Effect of the zeolite matrix on the formation of Mn2+(CO) geminal species

Promoted Zinc Chromite Catalysts for Higher Alcohol Synthesis

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I.r. spectroscopic evidence of formyl species formed by CO and H₂Co-adsorption on ZnO and Cu–ZnO