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D. Osadchii

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Journal article (2023) - Juan J. Mercadal, Dmitrii Osadchii, Valeriya Zarubina, María José Valero-Romero, Ignacio Melián-Cabrera
The authors regret that Eq. (2) in the original manuscript was mistyped by accident. Below, an amended Eq. (2) is given. The values associated to this equation in the original publication are however correct and it does not change the discussion of the results. However, the wrong equation in the original publication can lead to confusion. Corrected equation: [Formula presented] Where [Formula presented]values (mol/h) are the molar flowrates, p is a stoichiometric factor (1 for styrene and 8 for COx). The term ‘EB’ refers to ethylbenzene. The term ‘X’ refers to the products which can be styrene or COx. The subscript ‘IN’ means the molar flow entering the reactor, whereas ‘OUT’ means the flow out of the reactor. The authors would like to apologise for any inconvenience caused. ...
Journal article (2022) - Juan J. Mercadal, Dmitrii Osadchii, Valeriya Zarubina, María José Valero-Romero, Ignacio Melián-Cabrera
An in situ thermal reactivation of a multi-walled carbon-nanostructure (MWCNT) is feasible with improved performance in the O2-mediated styrene synthesis, also called oxidative dehydrogenation of ethylbenzene (EB). The actual catalyst is the coke deposited at the beginning of the reaction on the MWCNT, denoted as ODH-coke, i.e., forming a supported organocatalyst. The deactivation mechanism is the continuing and severe coking that reduces the surface area and eventually plugs the catalyst bed. The reactivation was carried out in situ after studying the combustion kinetics of the ODH-coke, which combusts at lower temperature than the MWCNT. The reactivation generated a different catalyst than the original, formed by porous ODH-coke, unmodified ODH-coke and the MWCNT backbone. The performance of such reactivated organocatalyst was improved, becoming more selective to styrene and less to COx. This was explained by the increased concentration of ketonic and phenol groups, during the reactivation. Explaining the conversion enhancement is not straightforward because the reaction is limited in O2. For this, a model was applied that explains that the increased EB conversion is caused by the lowered COx selectivity. The model also explains the EB conversion decay with time on stream, due to the enhanced COx selectivity; though the nature of the latter effect is not yet fully understood. This work brings three main messages: (a) survival of the MWCNT backbone against gasification/combustion, (b) a better organocatalyst is formed after reactivation, and (c) a model which explains the conversion-selectivity changes (improvement and decay). The latter represents a change in paradigm since conversion and selectivity are considered independent parameters, in heterogeneous catalysis. ...