Dataset Information

The Ti₃ AlC₂ MAX Phase as an Efficient Catalyst for Oxidative Dehydrogenation of n-Butane.

ABSTRACT: Dehydrogenation or oxidative dehydrogenation (ODH) of alkanes to produce alkenes directly from natural gas/shale gas is gaining in importance. Ti₃ AlC₂ , a MAX phase, which hitherto had not been used in catalysis, efficiently catalyzes the ODH of n-butane to butenes and butadiene, which are important intermediates for the synthesis of polymers and other compounds. The catalyst, which combines both metallic and ceramic properties, is stable for at least 30?h on stream, even at low O₂ :butane ratios, without suffering from coking. This material has neither lattice oxygens nor noble metals, yet a unique combination of numerous defects and a thin surface Ti_1-y Al_y O_2-y/2 layer that is rich in oxygen vacancies makes it an active catalyst. Given the large number of compositions available, MAX phases may find applications in several heterogeneously catalyzed reactions.

SUBMITTER: Ng WHK

PROVIDER: S-EPMC5817242 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

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Publications

The Ti3 AlC2 MAX Phase as an Efficient Catalyst for Oxidative Dehydrogenation of n-Butane.

Ng Wesley H K WHK Gnanakumar Edwin S ES Batyrev Erdni E Sharma Sandeep K SK Pujari Pradeep K PK Greer Heather F HF Zhou Wuzong W Sakidja Ridwan R Rothenberg Gadi G Barsoum Michel W MW Shiju N Raveendran NR

Angewandte Chemie (International ed. in English) 20180109 6

Dehydrogenation or oxidative dehydrogenation (ODH) of alkanes to produce alkenes directly from natural gas/shale gas is gaining in importance. Ti3 AlC2 , a MAX phase, which hitherto had not been used in catalysis, efficiently catalyzes the ODH of n-butane to butenes and butadiene, which are important intermediates for the synthesis of polymers and other compounds. The catalyst, which combines both metallic and ceramic properties, is stable for at least 30 h on stream, even ...[more]

PMID: 29071772

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Project description:Propane (C3H8) and butane (C4H10) are short straight-chain alkane molecules that are difficult to convert catalytically. Analogous to propane, butane can be dehydrogenated to butenes (also known as butylenes) or butadiene, which are used industrially as raw materials when synthesizing various chemicals (plastics, rubbers, etc.). In this study, we present results of detailed first-principles-based multiscale modelling of butane dehydrogenation, consisting of three size- and time-scales. The reaction is modelled over Cr2O3(0001) chromium oxide, which is commonly used in the industrial setting. A complete 108-step reaction pathway of butane (C4H10) dehydrogenation was studied, yielding 1-butene (CH2CHCH2CH3) and 2-butene (CH3CHCHCH3), 1-butyne (CHCCH2CH3) and 2-butyne (CH3CCCH3), butadiene (CH2CHCHCH2), butenyne (CH2CHCCH), and ultimately butadiyne (CHCCCH). We include cracking and coking reactions (yielding C1, C2, and C3 hydrocarbons) in the model to provide a thorough description of catalyst deactivation as a function of the temperature and time. Density functional theory calculations with the Hubbard U model were used to study the reaction on the atomistic scale, resulting in the complete energetics and first-principles kinetic parameters for the dehydrogenation reaction. They were cast in a kinetic model using mean-field microkinetics and kinetic Monte Carlo simulations. The former was used to obtain gas equilibrium conditions in the steady-state regime, which were fed in the latter to provide accurate surface kinetics. A full reactor simulation was used to account for the macroscopic properties of the catalytic particles: their loading, specific surface area, and density and reactor parameters: size, design, and feed gas flow. With this approach, we obtained first-principles estimates of the catalytic conversion, selectivity to products, and time dependence of the catalyst activity, which can be paralleled to experimental data. We show that 2-butene is the most abundant product of dehydrogenation, with selectivity above 90% and turn-over frequency above 10-3 s-1 at T = 900 K. Butane conversion is below 5% at such low temperature, but rises above 40% at T > 1100 K. Activity starts to drop after ∼6 h because of surface poisoning with carbon. We conclude that the dehydrogenation of butane is a viable alternative to conventional olefin production processes.

Dataset Information

The Ti₃ AlC₂ MAX Phase as an Efficient Catalyst for Oxidative Dehydrogenation of n-Butane.

Publications

The Ti<sub>3</sub> AlC<sub>2</sub> MAX Phase as an Efficient Catalyst for Oxidative Dehydrogenation of n-Butane.

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