Density functional theory calculation of propane cracking mechanism over chromium (III) oxide by cluster approach

Oyegoke, Toyese; Dabai, Fadimatu Nyako; Uzairu, Adamu; Jibril, Baba Y.

doi:10.2298/jsc200521044o

Cited by 3 publications

(6 citation statements)

References 25 publications

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“…The rate-determining step (RDS) obtained in this study was found to be similar to that which was identified by Oyegoke et al [17], for the cracking of propane into small molecules, although the reaction path is different (Cr-O is feasible for propane dehydrogenation while Cr-Cr route is feasible for propane cracking). The energy barrier obtained for the second C-H abstraction step in this study was found to be lower than that barrier obtained by Oyegoke et al [17] for the cracking of propyl specie on the path of Cr-Cr reaction route, which often leads to cracking of the molecule due to the high activity of the Cr sites present on the catalyst surface in agreement with literature [10]. Therefore, this suggests reducing Cr site dominance on the catalyst surface via the substitution of selected Cr sites or oxidant/oxygen use.…”

Section: Evaluation Of Thermodynamic Feasibility Of a Different Reactsupporting

confidence: 85%

“…Similarly, the findings agreed with the report of Oyegoke et al [10] on the chromium oxide sites' acidity reactivity, where Cr site was confirmed to be the most active site on a chromium oxide catalyst. However, an excess concentration of these Cr sites would tend to promote the cracking of the propane into undesired products as reported in the literature [17] where the Cr-Cr reaction route was identified to be the path promoting cracking of propane into smaller molecules (methane, ethylene, and cokes) which could lead to coking of the catalyst. Figures 5 and 6 show the reaction energies for the forward reactions of the elementary steps in the propane dehydrogenation process.…”

Section: Reaction Steps Reaction Stepsmentioning

confidence: 79%

“…Studies indicate that a 6-31G* basis set, which is widely considered the best compromise in terms of accuracy and speed, is the most frequently used basis set available for H-Kr elements. Simultaneously, heavier atoms were modeled using the LANL2DZ basis set, which uses an effective core for all atoms larger than Ne [16,17].…”

Section: Theoretical Backgroundmentioning

confidence: 99%

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Mechanistic insight into propane dehydrogenation into propylene over chromium (III) oxide by cluster approach and Density Functional Theory calculations

et al. 2020

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A preliminary study to provides insight into the kinetic and thermodynamic assessment of the reaction mechanism involved in the non-oxidative dehydrogenation (NOD) of propane to propylene over Cr2O3, using a density functional theory (DFT) approach, has been undertaken. The result obtained from the study presents the number of steps involved in the reaction and their thermodynamic conditions across different routes. The rate-determining step (RDS) and a feasible reaction pathway to promote propylene production were also identified. The results obtained from the study of the 6-steps reaction mechanism for dehydrogenation of propane into propylene identified the first hydrogen abstraction and hydrogen desorption to be endothermic. In contrast, other steps that include propane’s adsorption, hydrogen diffusion, and the second stage of hydrogen abstraction were identified as exothermic. The study of different reaction routes presented in the energy profiles confirms the Cr-O (S1, that is, the reaction pathway that activates the propane across the Cr-O site at the alpha or the terminal carbon of the propane) pathway to be the thermodynamically feasible pathway for the production of propylene. The first hydrogen abstraction step was identified as the potential rate-determining step for defining the rate of the propane dehydrogenation process. This study also unveils that the significant participation of Cr sites in the propane dehydrogenation process and how the Cr high surface concentration would hinder the desorption of propylene and thereby promote the production of undesired products due to the stronger affinity that exists between the propylene and Cr-Cr site, which makes it more stable on the surface. These findings thereby result in Cr-site substitution suggestion to prevent deep dehydrogenation in propane conversion to propylene. This insight would aid in improving the catalyst performance.

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Section: Evaluation Of Thermodynamic Feasibility Of a Different Reactsupporting

confidence: 85%

Section: Reaction Steps Reaction Stepsmentioning

confidence: 79%

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Mechanistic insight into propane dehydrogenation into propylene over chromium (III) oxide by cluster approach and Density Functional Theory calculations

et al. 2020

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“…However, the literature shows that studies were primarily concentrating their investigations on using platinum-based catalysts. [8][9][10][11][12][13][14][15][16][17][18] Only a few studies gave preferential attention to chromium-based catalysts, [19][20][21][22][23][24][25][26][27][28][29][30][31][32] while some have investigated other catalyst forms like zeolite, nickel, gallium oxide, and many others. [33][34][35][36] Existing reports show that some works deployed an experimental approach to study the catalysts.…”

Section: Introductionmentioning

confidence: 99%

“…Among the few studies that have reported on the use of chromium-based catalysts is the report of Oyegoke et al, 28 which indicated that the chromium site played a significant role in controlling the reaction compared to the oxygen site on the Cr 2 O 3 catalyst. Another report 29 showed that highly concentrated chromium sites on the chromium-based catalyst can promote deeper dehydrogenation, cracking the intermediates to undesired products. It was further reported that the reaction paths with moderate chromium site participation favoured better selectivity for propylene production.…”

Section: Introductionmentioning

confidence: 99%

Impact of Mo and W on CrXO3 (X = Cr, Mo, W) Catalytic Performance in a Propane Non-oxidative Dehydrogenation Process

Oyegoke

Dabai

Waziri

et al. 2022

Kemija U Industriji

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The impact of molybdenum (Mo) and tungsten (W) on improving the catalytic characteristics of the chromium-based catalyst, Cr 2 O 3 , was explored in this study. The use of semi-empirical and density functional theory computational methods was deployed to understand the impact of the substitution of the chromium (Cr) with Mo and W on the catalyst, CrXO 3 (where X = Cr, Mo, W) in the production of propylene from propane. Findings from the investigation confirmed that the surface modified with Mo showed better potential for improving the catalyst selectivity, retarding propylene dehydrogenation, cracking, and coking path than W, which offered a lower selectivity. The use of Mo was found to have better facilitated the propylene production due to its lower affinity for coke and cracking promoting adsorbates accounted for its sites, including easier desorption of propylene and higher barrier of deep dehydrogenation for preventing the production of undesired products, unlike the use of W. This study, therefore, recommends the use of Mo for the improvement of the catalyst that could result in better propylene yield, which could aid in meeting its rising market demand.

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Computational study of propene selectivity and yield in the dehydrogenation of propane via process simulation approach

Oyegoke

Dabai

Waziri

et al. 2023

Physical Sciences Reviews

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Propene is a vital feedstock in the petrochemical industry with a vast range of applications. And there is a continuous rise in propene demand. To gain insight into how the on-purpose method could help meet the demand in the propene market, we investigated the impact of temperature (T) and pressure (P) on product distribution in terms of product yield and selectivity using the process simulation approach. Existing related studies were deployed to identify possible products that could be evaluated in the simulation. In the study, we used Gibbs minimization (with Gibb’s reactor) to predict the likely products obtained at different T and P. The impact of feed purity on product distribution was also evaluated. The study was aided by using the Aspen HYSYS process simulator, while Design Expert was used to search for the optimum conditions for higher conversion, yield, and selectivity. Results obtained for the modeling and simulation of the process show that operating the production process at a lower pressure would favor higher selectivity within the temperature range of 500–600 °C. In comparison, the one run at a higher pressure was predicted to be only promising, showing better selectivity within the range of 550–650 °C. The feed purity significantly impacts the propene amount, especially for one with sulfur impurity, leading to the formation of smaller olefins and sulfide compounds. Our study reveals the importance of reviewing feed purity before charging them into the dehydrogenation reactor to prevent poisoning, coking, and other activities, which do lead to undesired products like methane and ethylene. A catalyst can also be designed to efficiently dehydrogenate the propane to propene at a lower temperature to prevent side reactions.

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Density functional theory calculation of propane cracking mechanism over chromium (III) oxide by cluster approach

Cited by 3 publications

References 25 publications

Mechanistic insight into propane dehydrogenation into propylene over chromium (III) oxide by cluster approach and Density Functional Theory calculations

Mechanistic insight into propane dehydrogenation into propylene over chromium (III) oxide by cluster approach and Density Functional Theory calculations

Impact of Mo and W on CrXO3 (X = Cr, Mo, W) Catalytic Performance in a Propane Non-oxidative Dehydrogenation Process

Computational study of propene selectivity and yield in the dehydrogenation of propane via process simulation approach

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