Investigation of the mechanism of catalytic oxidation of propylene to acrolein and acrylonitrile*1

Kinetic Modeling of the Partial Oxidation of Propylene to Acrolein: A Systematic Procedure for Parameter Estimation Based on Non-isothermal Data

“…The scheme includes in total 10 reaction pathways to form acrolein and all byproducts. It is well-known and widely accepted that the formation of acrolein takes place in two substeps. ,,− , In the first step, a hydrogen abstraction from propylene results in the formation of a π-allyl-complex at the catalyst surface as an intermediate species. This formation is accepted as the rate-determining step of the propylene oxidation to acrolein.…”

“…Catalytic propylene oxidation has already been investigated for about the last 50 years, whereby detailed studies regarding the mechanism of the main reaction were carried out several times. − As a result of this extensive research, the single elementary steps of the partial oxidation are very well-known, including a first hydrogen abstraction from the propylene molecule to form an intermediate complex at the catalyst surface followed by an incorporation of lattice oxygen and the second hydrogen abstraction. − The first hydrogen abstraction is widely accepted as the rate-determining step of the macroscopic reaction step. Regarding the state of oxidation, the sequence of these partial steps leads to a so-called reduced catalyst which is then reoxidized by gas-phase oxygen.…”

Identifying the Unique Properties of α-Bi2Mo3O12 for the Activation of Propene

“…6 , 7 , 8 , 9 Both experimental and theoretical studies have identified this step to be the abstraction of a hydrogen atom from the terminal methyl group to produce a physisorbed allyl radical. 10,11,12,13,14 Isotopic labeling studies have shown that the oxygen atoms involved in propene oxidation come from the catalyst surface and not from adsorbed O2, which only serves to reoxidize the catalyst. 15,16, The elementary steps by which allyl radicals are converted to acrolein or acrylonitrile have been the subject of a number of studies.…”

“…The best single-phase catalyst for propene oxidation and ammoxidation is considered to be alpha bismuth molybdate, α-Bi 2 Mo 3 O 12 , though some researchers have suggested that other bismuth molybdate phases, such as β-Bi 2 Mo 2 O 9 and γ-Bi 2 MoO 6 , exhibit similar activities. − Mechanistic studies of propene oxidation and ammoxidation have therefore focused on the three primary bismuth molybdate phases, with particular emphasis on the α-Bi 2 Mo 3 O 12 phase. The activation energy and partial pressure dependencies for both reactions are the same, leading to the conclusion that the rate-limiting step is the same. − Both experimental and theoretical studies have identified this step to be the abstraction of a hydrogen atom from the terminal methyl group to produce a physisorbed allyl radical. − Isotopic labeling studies have shown that the oxygen atoms involved in propene oxidation come from the catalyst surface and not from adsorbed O 2 , which only serves to reoxidize the catalyst. , The elementary steps by which allyl radicals are converted to acrolein or acrylonitrile have been the subject of a number of studies. ,− …”

Acetonitrile (CAS No. 75-05-8)

“…2 É bem conhecido que a oxidação da acroleína na presença de amônia leve à nitrila insaturada correspondente (Equação 1). 3 Inúmeros trabalhos na literatura propõem a possibilidade de obter uma conversão completa, ou quase completa da acroleína em acrilonitrila. 4 No entanto, na descrição destes inúmeros processos, é mencionada sempre a existência de uma série de reações secundárias que levam à formação de pequenas quantidades de subprodutos, como: acetonitrila, propionitrila e também vários alcoóis.…”