Gas-phase aluminium acetylacetonate decomposition: revision of the current mechanism by VUV synchrotron radiation

Grimm, Sebastian; Baik, Seung-Jin; Hemberger, Patrick; Bodi, Andras; Kempf, Andreas; Kasper, Tina; Atakan, Burak

doi:10.1039/d1cp00720c

“…The reactor temperature is considered to represent the gas temperature inside the reactor to within 100 C. 18 The pressure and residence time in the reactor have been estimated to be 10-40 mbar and up to 100 μs, respectively. 18,19 The reactor is placed in the source vacuum chamber, where the pressure was $ 5 Â 10 À5 mbar during measurements. The molecular beam exiting the pyrolysis reactor passed through a 2 mm diameter skimmer into the detection chamber, kept at a pressure of 10 À6 mbar during measurements.…”

Section: Methodsmentioning

confidence: 99%

“…The reactor temperature is considered to represent the gas temperature inside the reactor to within 100°C 18 . The pressure and residence time in the reactor have been estimated to be 10–40 mbar and up to 100 μs, respectively 18,19 . The reactor is placed in the source vacuum chamber, where the pressure was ~ 5 × 10 −5 mbar during measurements.…”

Section: Methodsmentioning

confidence: 99%

Probing the pyrolysis of methyl formate in the dilute gas phase by synchrotron radiation and theory

Lowe

¹

,

Cardona

²

,

Salas

³

et al. 2022

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The thermal dissociation of the atmospheric constituent methyl formate was probed by coupling pyrolysis with imaging photoelectron photoion coincidence spectroscopy (iPEPICO) using synchrotron VUV radiation at the Swiss Light Source (SLS). iPEPICO allows threshold photoelectron spectra to be obtained for pyrolysis products, distinguishing isomers and separating ionic and neutral dissociation pathways. In this work, the pyrolysis products of dilute methyl formate, CH 3 OC(O)H, were elucidated to be CH 3 OH + CO, 2 CH 2 O and CH 4 + CO 2 as in part distinct from the dissociation of the radical cation (CH 3 OH +• + CO and CH 2 OH + + HCO). Density functional theory, CCSD(T), and CBS-QB3 calculations were used to describe the experimentally observed reaction mechanisms, and the thermal decomposition kinetics and the competition between the reaction channels are addressed in a statistical model. One result of the theoretical model is that CH 2 O formation was predicted to come directly from methyl formate at temperatures below 1200 K, while above 1800 K, it is formed primarily from the thermal decomposition of methanol.

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“…Neither atomic iron, nor other iron-containing intermediates were detected in the gas-phase at temperatures below 900 K. If these species were formed in gas-phase reactions, we expect to be able to detect them based on previous experimental experience. [47] Additionally, previous studies of other investigators by quadrupole mass spectrometry also did not observe their formation at temperatures below 1173 K. [25] It is evident from the findings by Dyagileva et al [42] that the activation energy for the thermolysis of the Fe-Cp bond on a surface is much lower than in the gas-phase. A similar behavior is observed in our study, because a significant amount of Fe is only detected in the gas-phase after heating the reactor Table 1.…”

Section: Pyrolysis Pathways Of Ferrocenementioning

confidence: 93%

Mechanism and kinetics of the thermal decomposition of Fe(C5H5)2 in inert and reductive atmosphere: A synchrotron-assisted investigation in a microreactor

Grimm¹,

Hemberger²,

Kasper³

et al. 2022

Preprint

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0

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Since its discovery in the 1950s, [1,2] the metallocene ferrocene (Fe(Cp) 2 ), is, due to its remarkable stability, [3] an extensively studied compound. [4] It is a classical sandwich complex, where two cyclopentadienyl ligands are attached to a central iron core. Ferrocene is characterized by a relatively high vapor pressure at moderate temperatures, it is nontoxic and stable in air and therefore an easy to handle precursor for the synthesis of functional materials. [5] In particular, the use of ferrocene has been successfully established in the preparation of iron-containing thin films for optoelectronic devices [6,7] or iron thin films in an oxidative atmosphere in metallurgical applications. [8] Upon thermal decomposition of Fe(Cp) 2 , iron nanoparticles (Fe-NP) can be formed which may subsequently act as functional nanomaterials for energy conversion and storage systems. [9,10] Those Fe-NPs have additionally shown excellent performance and emission characteristics in biodiesel engines [11,12] and as a burning catalyst in rocket propellants, [13] since hydrocarbon radicals, responsible for soot formation, are quenched. [11] Nowadays, ferrocene is among the most widely used precursors in the synthesis of carbon nanotubes (CNTs), [14] either as a feedstock to produce catalytic sites necessary for their growth, [15][16][17][18][19][20][21][22] or as both carbon and catalyst precursor. [23][24][25][26] Those functional nanomaterials are often manufactured by high yield, low-temperature methods, [14] as for instance by catalytic chemical vapor deposition (CCVD). The underlying synthesis routes and processes were extensively studied experimentally [15][16][17]19,20,[27][28] and numerically. [29][30][31][32][33][34] It can be concluded, that the hydrocarbon source has a major influence on the morphology, crystallinity, and growth kinetics of CNTs, mediated through its gas-phase decomposition products pertaining to its initial structure, [35] as well as the catalyst activity. The control of product quality requires understanding the gas-phase decomposition mechanism of ferrocene at various reaction conditions. The intermediates act either as a promoter of CNT growth by serving as carbon feedstock or as a detrimental impurity, lowering the growth rate by forming unwanted volatile and polyaromatic hydrocarbons, [36,37] deactivating the iron catalyst particles by forming Fe 3 C (cementite), or by carbon incorporation or encapsulation. [8] The decomposition and reduction of ferrocene, an important precursor for iron chemical vapor deposition and catalyst for nanotube synthesis, is investigated in the gas-phase. Reactive intermediates are detected to understand the underlying chemistry by using a microreactor coupled to a synchrotron light source. Utilizing soft photoionization coupled with photoelectron-photoion coincidence detection enables us to characterize exclusive intermediates isomer-selectively. A reaction mechanism for the ferrocene decomposition is proposed, which proceeds as a two-step process. Initially, the ...

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“…For the sake of clarity, the reader is referred to our work on the numerical simulation of the microreactor, which is described in detail elsewhere. [47] In brief, to determine the temperature dependence of the Fe(C 5 H 5 ) 2 mole fraction, the procedure proposed by Zhang et al, [106] was followed, where the influence of temperature-dependent signal variations of argon (m/z 40) due to a change in expansion behavior and therefore the sampling efficiency is characterized by the gas expansion coefficient λ(T). This expansion coefficient was determined by recording temperature-dependent mass spectra at a fixed photon energy of 15.8 eV in the 300-1300 K range (Figure S4, Supporting Information).…”

Section: Methodsmentioning

confidence: 99%

Mechanism and Kinetics of the Thermal Decomposition of Fe(C₅H₅)₂ in Inert and Reductive Atmosphere: A Synchrotron‐Assisted Investigation in A Microreactor

Grimm

¹

,

Hemberger

²

,

Kasper

³

et al. 2022

Adv Materials Inter

Self Cite

View full text Add to dashboard Cite

Since its discovery in the 1950s, [1,2] the metallocene ferrocene (Fe(Cp) 2 ), is, due to its remarkable stability, [3] an extensively studied compound. [4] It is a classical sandwich complex, where two cyclopentadienyl ligands are attached to a central iron core. Ferrocene is characterized by a relatively high vapor pressure at moderate temperatures, it is nontoxic and stable in air and therefore an easy to handle precursor for the synthesis of functional materials. [5] In particular, the use of ferrocene has been successfully established in the preparation of iron-containing thin films for optoelectronic devices [6,7] or iron thin films in an oxidative atmosphere in metallurgical applications. [8] Upon thermal decomposition of Fe(Cp) 2 , iron nanoparticles (Fe-NP) can be formed which may subsequently act as functional nanomaterials for energy conversion and storage systems. [9,10] Those Fe-NPs have additionally shown excellent performance and emission characteristics in biodiesel engines [11,12] and as a burning catalyst in rocket propellants, [13] since hydrocarbon radicals, responsible for soot formation, are quenched. [11] Nowadays, ferrocene is among the most widely used precursors in the synthesis of carbon nanotubes (CNTs), [14] either as a feedstock to produce catalytic sites necessary for their growth, [15][16][17][18][19][20][21][22] or as both carbon and catalyst precursor. [23][24][25][26] Those functional nanomaterials are often manufactured by high yield, low-temperature methods, [14] as for instance by catalytic chemical vapor deposition (CCVD). The underlying synthesis routes and processes were extensively studied experimentally [15][16][17]19,20,[27][28] and numerically. [29][30][31][32][33][34] It can be concluded, that the hydrocarbon source has a major influence on the morphology, crystallinity, and growth kinetics of CNTs, mediated through its gas-phase decomposition products pertaining to its initial structure, [35] as well as the catalyst activity. The control of product quality requires understanding the gas-phase decomposition mechanism of ferrocene at various reaction conditions. The intermediates act either as a promoter of CNT growth by serving as carbon feedstock or as a detrimental impurity, lowering the growth rate by forming unwanted volatile and polyaromatic hydrocarbons, [36,37] deactivating the iron catalyst particles by forming Fe 3 C (cementite), or by carbon incorporation or encapsulation. [8] The decomposition and reduction of ferrocene, an important precursor for iron chemical vapor deposition and catalyst for nanotube synthesis, is investigated in the gas-phase. Reactive intermediates are detected to understand the underlying chemistry by using a microreactor coupled to a synchrotron light source. Utilizing soft photoionization coupled with photoelectron-photoion coincidence detection enables us to characterize exclusive intermediates isomer-selectively. A reaction mechanism for the ferrocene decomposition is proposed, which proceeds as a two-step process. Initially, the ...

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Gas-phase aluminium acetylacetonate decomposition: revision of the current mechanism by VUV synchrotron radiation

Abstract: Although aluminium acetylacetonate, Al(C5H7O2)3, is a common precursor for chemical vapor deposition (CVD) of aluminium oxide, its gas phase decomposition is not very well investigated. Here, we studied its thermal...

Cited by 27 publications

References 92 publications

Probing the pyrolysis of methyl formate in the dilute gas phase by synchrotron radiation and theory

Probing the pyrolysis of methyl formate in the dilute gas phase by synchrotron radiation and theory

Mechanism and kinetics of the thermal decomposition of Fe(C5H5)2 in inert and reductive atmosphere: A synchrotron-assisted investigation in a microreactor

Mechanism and Kinetics of the Thermal Decomposition of Fe(C₅H₅)₂ in Inert and Reductive Atmosphere: A Synchrotron‐Assisted Investigation in A Microreactor

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Gas-phase aluminium acetylacetonate decomposition: revision of the current mechanism by VUV synchrotron radiation

Abstract: Although aluminium acetylacetonate, Al(C5H7O2)3, is a common precursor for chemical vapor deposition (CVD) of aluminium oxide, its gas phase decomposition is not very well investigated. Here, we studied its thermal...

Cited by 27 publications

References 92 publications

Probing the pyrolysis of methyl formate in the dilute gas phase by synchrotron radiation and theory

Probing the pyrolysis of methyl formate in the dilute gas phase by synchrotron radiation and theory

Mechanism and kinetics of the thermal decomposition of Fe(C5H5)2 in inert and reductive atmosphere: A synchrotron-assisted investigation in a microreactor

Mechanism and Kinetics of the Thermal Decomposition of Fe(C5H5)2 in Inert and Reductive Atmosphere: A Synchrotron‐Assisted Investigation in A Microreactor

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Product

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Mechanism and Kinetics of the Thermal Decomposition of Fe(C₅H₅)₂ in Inert and Reductive Atmosphere: A Synchrotron‐Assisted Investigation in A Microreactor