# Ab Initio Multiscale Process Modeling of Ethane, Propane and Butane Dehydrogenation Reactions: A Review

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

^{®}and Catofin

^{®}[2]. While both are used for propane and isobutane dehydrogenation, they differ slightly by the reactor type and setup, and mostly by the type of catalysts used: while the former uses Pt/Sn-type catalysts, the latter uses CrO${}_{x}$ catalysts, both on alumina support and promoted with various metals, most commonly Na and K [2]. Both technologies suffer from coke deposition on the catalyst surface, requiring the use of special catalyst regeneration reactor in dehydrogenation unit, to enable recycling by burning and purging the coke deposits as gaseous products [3].

^{®}and Catofin

^{®}predominate. Non-oxidative BDH is highly endothermic, making the reaction technologically challenging. Therefore, high temperatures (800–1000 K) and low pressures (around 1 atm) are optimal for the reaction. The rate-controlling steps consist of C–H and C–C cleavage, whose rates differ depending on the backbone of the hydrocarbons involved. When C–C predominates, cracking and eventually coking occur, which is undesirable. This is affected by the catalyst used, which can be either noble metal-based or metal oxide-based.

## 2. On Multiscale Modeling

## 3. Results and Discussion

#### 3.1. Ethane Dehydrogenation

#### 3.2. Propane Dehydrogenation

#### 3.2.1. Catalysts Used in Propane Dehydrogenation Process

^{®}process simulations software [42]. Du et al. studied PDH over the $\mathrm{C}{\mathrm{r}}_{2}{\mathrm{O}}_{3}$-$\mathrm{A}{\mathrm{l}}_{2}{\mathrm{O}}_{3}$ catalyst in a circulating fluidized bed reactor with optimal operating conditions for propane with temperature at 600 ${}^{\circ}$C, pressure of P = 0.1 MPa and propane flow of 12.5 L/min. They defined a kinetic model with four non-oxidative reaction paths and used predicted hydrodynamics and species concentration distribution using the CFD model. Although the experimental propane conversion of around 39% was slightly lower than conversion obtained from simulations, which was approximately 42%, the agreement is still very good. The selectivity as obtained from the simulations was 83%, which is consistent with the experimental value of 84% [11]. Based on the results above, we conclude that in general, metal oxide catalysts give slightly lower selectivities compared to the Pt catalysts.

#### 3.2.2. Coke Formation and Catalyst Deactivation

#### 3.3. Butane Dehydrogenation

#### Catalysts Used in Butane Dehydrogenation Process

^{®}technology. At lower or higher pressures, the conversion is lower (Figure 14).

## 4. Discussion and Conclusions

## Funding

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 1.**An example of the proposed reaction mechanism for the butane dehydrogenation over Cr${}_{2}$O${}_{3}$-type catalyst. The reaction activation energy is given for all elementary steps, while cracking sites are also depicted and their activation energies were also calculated via DFT. (Reprinted with permission from [20]).

**Figure 2.**A schematic representation of the multiscale modeling, with various methods representing different temporal and spatial scales of the modeling phenomena. (Reprinted with permission from [22]. Copyright 2020 Elsevier).

**Figure 3.**Free energy diagrams (at 873 K, 0.2 bar ${\mathrm{C}}_{2}{\mathrm{H}}_{6}$, $2\xb7{10}^{-4}$ bar ${\mathrm{C}}_{2}{\mathrm{H}}_{4}$, (0.1% carbon conversion), and 0.6 bar ${\mathrm{H}}_{2}$) are presented. Solid lines represent the most relevant pathway in ethane conversion to ethylene, and dotted lines the elementary step to $\mathrm{C}{\mathrm{H}}_{3}\mathrm{CH}$*. Pathways are drawn for three different catalysts, Cu, $\mathrm{P}{\mathrm{t}}_{3}\mathrm{Sn}$ and Pt. Atomic structures are shown in the right panel (large gray spheres = surface atoms, black spheres = C atoms, small white spheres = H atoms). (Reprinted with permission from [6]. Copyright 2019 Elsevier).

**Figure 4.**Ethane conversion and ethylene selectivity versus molar ratio of ${\mathrm{C}}_{2}{\mathrm{H}}_{6}$ and ${\mathrm{O}}_{2}$ in the reactor feed obtained from CFD models, represented by lines (points are experimentally obtained results). (

**a**,

**b**) Donsì et al. results on Pt (

**a**) and Pt/Sn catalyst (

**b**). (Reprinted with permission from [7]. Copyright 2005 American Chemical Society); (

**c**) Ethane conversion and ethylene selectivity results form Stefanidis and Vlachos. (Reprinted with permission from [10]).

**Figure 5.**Comparison of propylene selectivity of different Pt cluster size versus time-on-steam (TOS). Empty symbols represent selectivity, and filled symbols represent TOF. Diamonds-1 nm, squares-3 nm, circles-5 nm, upward-pointing triangles-7 nm, downward-pointing triangles-9 nm cluster size. (Reprinted with permission from [34]. Copyright 2015 American Chemical Society).

**Figure 6.**Conversion and selectivity of $\mathrm{P}{\mathrm{t}}_{3}\mathrm{In}$, Pt and $\mathrm{P}{\mathrm{t}}_{3}\mathrm{Sn}$ catalysts in PDH process. Reaction conditions: T = 600 ${}^{\circ}$C, atmospheric pressure, total flow rate = 50 mL/min. (Reprinted with permission from [33]. Published by The Royal Society of Chemistry).

**Figure 7.**Stability test of g-${\mathrm{C}}_{3}{\mathrm{N}}_{4}$-12 h at 500 ${}^{\circ}$C in PDH process. Reaction conditions: 0.7 g catalyst, He/${\mathrm{C}}_{3}{\mathrm{N}}_{8}$/${\mathrm{O}}_{2}$ = 4/4/1, flow rate = 18 mL/min. (Reprinted with permission from [44]. Copyright 2020 Elsevier).

**Figure 8.**Propane conversion in PDH process over Ga-Rh catalyst (Reaction conditions: t = 550 ${}^{\circ}$C, P = 1.2 bar) with different Ga-Rh molar ratios: 0 = open circles, 34 = downward-pointing triangles, 89 = upward-pointing triangles, 125 = diamonds. (Reprinted with permission from [45]. Copyright 2019 American Chemical Society).

**Figure 9.**Selectivity-conversion plot for several temperatures of BDH catalysed over V/MgO in the ICFBR (interconnected fluidized-bed reactor). The mathematical model of the ICFBR with included kinetic and fluid dynamic model of the reaction was used. It shows that for a given temperature, the ODH selectivity decreases with butane conversion, gradually at first and more steeply later. (Reprinted with permission from [53]. Copyright 2004 John Wiley and Sons, American Institute of Chemical Engineers).

**Figure 10.**Butane conversion and product selectivity versus time, for an in situ redox fluidized bed reactor during oxidative dehydrogenation of n-butane on V/MgO catalyst. The conversion of butane increases in the first half an hour until a steady state is reached. The selectivity to ${\mathrm{C}}_{4}$ is high in the beginning, but later decreases when the CO${}_{\mathrm{x}}$ is formed. (Reprinted with permission from [54]. Copyright 2001 Elsevier).

**Figure 11.**Selectivity–conversion plot for FBR (fixed bed reactor) and IMR (inert membrane reactor) of the oxidative dehydrogenation of butane over V/MgO catalyst. (Reprinted with permission from [55]. Copyright 1999 Elsevier).

**Figure 12.**The effect of the reaction temperature in the FBR. ODH reaction on V/MgO was studied by mathematical modeling of a FBR. According to the results of the study, the selectivity to ${\mathrm{C}}_{4}$ increased with the increasing temperature. (Reprinted with permission from [56]. Copyright 2002 Elsevier).

**Figure 13.**(

**Left**) Temporal evolution of the lattice coverage. (

**Right**) Lattice snapshot at the final time of the kMC simulation. Please note that there are two types of active sites on the lattice, corresponding to the binding sites for hydrocarbons (black) and hydrogen (blue). The simulation conditions are P = 1 bar and T = 950 K. (Reprinted with permission from [20]).

**Figure 14.**Butane conversion from MKM simulations at different operating conditions (temperature and pressure). Red dashed line shows the industrial conversion using the Catadiene

^{®}technology. (Reprinted with permission from [20]).

**Table 1.**The overview of the multiscale modeling results for ethane dehydrogenation process over different catalysts, reactor types, and conditions. Oxidative (O) and non-oxidative (NO) reaction types were considered.

Source | Reaction Type | Scale, Methods | Catalyst | Reactor | Conditions | Conversion | Selectivity | Coke Deposition |
---|---|---|---|---|---|---|---|---|

[4] | O | micro-kinetics, CFD | eggshell $\mathrm{Pt}/\mathrm{A}{\mathrm{l}}_{2}{\mathrm{O}}_{3}$ | adiabatic fixed bed (2D-DEM CFD), SCTR | varied | 92% (SCTR) | 67% (SCTR) | oxidative dehydrogenation reduces coke formation and number of side reactions |

[5] | O, NO | DFT, micro-kinetics | Pt | N/A | N/A | N/A | N/A | N/A |

[8] | O, dry reforming | DFT, kMC | $\mathrm{PtNi}/\mathrm{Ce}{\mathrm{O}}_{2}$ | N/A | N/A | N/A | N/A | N/A |

[9] | O | micro-kinetics, CFD | $\mathrm{Pt}/\mathrm{A}{\mathrm{l}}_{2}{\mathrm{O}}_{3}$ | microstructured (quartz) | N/A | 82.5% | 90% | N/A |

[6] | NO | DFT, micro-kinetics | metallic | N/A | 873 K, 0.2 bar ethane | N/A | N/A | N/A |

[7] | O | micro-kinetics, CFD | $\mathrm{Pt}$ and $\mathrm{Pt}/\mathrm{Sn}$ | plug-flow | 30 vol% ${\mathrm{N}}_{2}$; ${\mathrm{C}}_{2}{\mathrm{H}}_{6}/{\mathrm{O}}_{2}$ ratio varied from 1.5–2; pressure 1.2 atm and varied | 95% | up to 80% | N/A |

[30] | endothermic, NO | DFT | Pt-Sn alloy | N/A | N/A | N/A | higher Sn loading increases selectivity | Sn addition lowers coke deposition |

**Table 2.**The overview of the multiscale modeling results for propane dehydrogenation process over different catalysts, reactor types, and conditions. Oxidative (O) and non-oxidative (NO) reaction types were considered.

Source | Reaction Type | Scale, Methods | Catalyst | Reactor | Conditions | Conversion | Selectivity | Coke Deposition |
---|---|---|---|---|---|---|---|---|

[11] | endothermic, NO | reaction kinetics, CFD | $\mathrm{C}{\mathrm{r}}_{2}{\mathrm{O}}_{3}/\mathrm{A}{\mathrm{l}}_{2}{\mathrm{O}}_{3}$ | circulating fluidized bed | GHSV = 2350 h${}^{-1}$; propane flow 12.5 L/min; catalyst load 0.8 kg; 600 ${}^{\circ}$C, 0.1 Mpa | 42.4% (CFD) | 83.1% (CFD) | 0.001 g coke/g catalyst |

[13] | endothermic, NO | DFT, kMC | $\mathrm{C}{\mathrm{r}}_{2}{\mathrm{O}}_{3}$ | well-mixed CSTR | 850 K, 1 bar | N/A | 100% (kMC) | coke formation rate: ${10}^{-4}\phantom{\rule{0.166667em}{0ex}}{\mathrm{s}}^{-1}$ at 1000 K |

[41] | O | kinetic modeling, particle CFD | $\mathrm{V}/\mathrm{Zr}{\mathrm{O}}_{2}$-$\gamma $$\mathrm{A}{\mathrm{l}}_{2}{\mathrm{O}}_{3}$ | circulating fluidized bed | steam velocity: 3 m/s; time step: 0.01 s; end time: 40 s; 500, 525, 550 ${}^{\circ}$C, 1 atm | 28% (single particle flow); 20% (particle cluster flow) | 94% to propylene | low coke deposition |

[49] | endothermic, NO | DFT, kMC | Pt | N/A | N/A | N/A | 55–85% (depending on kMC lattice) | ${\mathrm{H}}_{2}$ reduces coke, regenerates active sites |

[42] | endothermic, NO | kinetics, macroscopic scale (ASPEN) | Na-doped $\mathrm{C}{\mathrm{r}}_{2}{\mathrm{O}}_{3}/\mathrm{A}{\mathrm{l}}_{2}{\mathrm{O}}_{3}$ | packed bed membrane | propane flow: 4000 kmol/h; propylene yield: 550 kton/yr; reactor volume: 421 m${}^{3}$; preheat T: 650 ${}^{\circ}$C | 45% | 90% to propylene | N/A |

[48] | endothermic, NO | kinetics [47], CFD | Pd-Ag | conventional membrane | feed flow rate: 0.75 L/min; 773 K, 1 bar | 49% (Pd membrane); 91% (Pd-Ag MR) | N/A | N/A |

[46] | exothermic, O | Monte Carlo | $\mathrm{VMgO}$ | N/A | N/A | N/A | model: 95%; experiment: 75% | N/A |

[43] | exothermic, O | DFT, kinetic study | hexagonal-BN | N/A | flow rate: 30 mL/min; 2.5 vol% of propane; 500–600 ${}^{\circ}$C | 500 ${}^{\circ}$C: 0.3%; 600 ${}^{\circ}$C: 38.2%; 600 ${}^{\circ}$C at 24 h: 43% | 94% at 500 ${}^{\circ}$C (propylene); 36% at 600 ${}^{\circ}$C (propylene); 75% (${\mathrm{C}}_{2}$+${\mathrm{C}}_{3}$ alkenes) | N/A |

[44] | exothermic, O | DFT, kinetic study | graphite-${\mathrm{C}}_{3}{\mathrm{N}}_{4}$ | N/A | flow rate: 18 mL/min; 500 ${}^{\circ}$C, 1 atm | 12.8% | 74.4% to propylene; 14.9% to ethylene | using oxidant (oxygen): coke deposition lower, lifetime increased |

[32] | endothermic, NO | DFT | Pt on BN nanosheet | N/A | N/A | N/A | N/A | hydrogen added to reduce coke |

[34] | endothernic, NO | DFT, kinetic study | Pt (various cluster size) | quartz | 0.05 g catalyst; 723–813 K, isothermal; 1–8 kPA ${\mathrm{C}}_{3}{\mathrm{H}}_{8}$, 1–10 kPa ${\mathrm{H}}_{2}$ | larger Pt clusters lower conversion | ∼1 nm Pt cluster: 51.9%; ∼9 nm Pt cluster: 95.8% | larger Pt clusters lower coke formation |

[45] | endothermic, NO | DFT, MD | Ga-Rh supported liquid metal solution | tubular quartz | propane flow: 8.9 mL/min; 550 ${}^{\circ}$C, 1.2 bar | 10–20% | ∼92% | N/A |

[33] | endothermic, NO | DFT, microkinetics | Pt, $\mathrm{P}{\mathrm{t}}_{3}\mathrm{In}$, $\mathrm{P}{\mathrm{t}}_{3}\mathrm{Sn}$ | N/A | total flow rate: 50 mL/min; 600 ${}^{\circ}$C, 1 atm | 5–20% (Figure 6) | 80–98% (Figure 6) | addition of In slows coke formation |

**Table 3.**The overview of the multiscale modeling results for butane dehydrogenation process over different catalysts, reactor types, and conditions. Oxidative (O) and non-oxidative (NO) reaction types were considered.

Source | Reaction Type | Scale, Methods | Catalyst | Reactor | Conditions | Conversion | Selectivity | Coke Deposition |
---|---|---|---|---|---|---|---|---|

[51] | endothermic, O | DFT-PBE, MD | ${\mathrm{V}}_{2}{\mathrm{O}}_{5}$ (001) | N/A | low temperature | N/A | N/A | N/A |

[52] | endothermic, O | DFT | ${\mathrm{V}}_{2}{\mathrm{O}}_{5}$ | N/A | N/A | N/A | N/A | N/A |

[53] | O | kinetic modeling, fluid dynamic | $\mathrm{V}/\mathrm{MgO}$ | internally circulating fluidized bed | 215 g catalyst; relative velocity: 1.5–5.5; feed rate: 1–4; 773–873 K | ∼33% (773 K) | ∼55% (773 K) | N/A |

[54] | O | kinetic modeling, gas and solid flow model | $\mathrm{V}/\mathrm{MgO}$ | two-zone fluidized bed | total feed rate: 223 Ncm${}^{3}$/min; 23 g catalyst; 773–873 K | ∼60% | ∼50% | N/A |

[55] | endothermic, O | kinetic and reactor modeling | $\mathrm{V}/\mathrm{MgO}$ | inert membrane (FBR, IMR) | 2.8 g catalyst; flow rate: 100–600 Nml/min; 773 K | ∼55% | 30% (butadiene), 10% (butenes) | N/A |

[56] | endothermic, O | kinetic and reactor modeling | $\mathrm{V}/\mathrm{MgO}$ | fixed bed, porous membrane | total flow rate: 4.5×10${}^{-4}$ mol/s; 748–823 K, 101.3 kPa; c(${\mathrm{O}}_{2}$) = 2–10%; c(${\mathrm{C}}_{4}{\mathrm{H}}_{1}0$) = 2–10%; c(${\mathrm{H}}_{2}O$) = 0–3%; c($\mathrm{C}{\mathrm{O}}_{2}$) = 0–3% | 70% (825 K) | 10% (butene), 60% (butyne) | N/A |

[58] | endothermic, NO | DFT, kinetic modeling | Ni(111) | N/A | 284.1 K–1028.2 K | N/A | N/A | coke deposition from deep dehydrogenation |

[59] | exothermic, O | DFT, kinetic modeling | $\mathrm{NiFe}$ bimetallic | quartz tube | inlet gas flow: 40 mL/min; 873 K, 1 atm | N/A | N/A | adding Fe to Ni improves performance |

[60] | endothermic, NO | DFT, DFT-D3 (vdW) | Ni(111) | N/A | N/A | N/A | N/A | N/A |

[61] | endothermic, NO | DFT, kinetic modeling | $\gamma $-$\mathrm{A}{\mathrm{l}}_{2}{\mathrm{O}}_{3}$ | N/A | 823 K | N/A | N/A | N/A |

[3] | endothermic, O | MCMC | $\mathrm{G}{\mathrm{a}}_{2}{\mathrm{O}}_{3}/\mathrm{A}{\mathrm{l}}_{2}{\mathrm{O}}_{3}$ | fixed bed | 793–853 K, 1 atm | 0.4–17.5% | N/A | no deactivation after 60 consecutive cycles |

[62] | NO | DFT | Pt/B/$\mathrm{Si}{\mathrm{O}}_{2}$, Pt/$\mathrm{Si}{\mathrm{O}}_{2}$ | quartz | GHSV: 2700 h${}^{-1}$; total flow rate: 100 mL/min; 823 K | N/A | 70% | coke surface deposit: 1.01% (Pt/$\mathrm{Si}{\mathrm{O}}_{2}$); 0.68% (Pt/B/$\mathrm{Si}{\mathrm{O}}_{2}$) |

[63] | endothermic, NO | DFT, kinetic modeling, microcalorimetrics | Pt-Zn/X-zeolite | down-flow | 673–773 K, 0.01–0.04 atm | 0.45% | 95–100% | N/A |

[64] | NO | kinetic and reactor modeling | Pt-In | zeolite membrane | feed rate: 50 cm${}^{3}$/min; 773 K, 1–1.4 atm | ∼42% (0.3 atm) | N/A | high hydrogen permeation induces catalyst deactivation |

[65] | NO | QM/MM, CBMC | Brønsted Acidic Zeolite | N/A | >673 K | N/A | N/A | N/A |

[66] | NO | DFT, QM/MM, CBMC | Brønsted Acidic Zeolite | tubular quartz | zeolite weight: 8–15 mg; 773 K | N/A | N/A | N/A |

[20] | endothermic, NO | DFT, kMC, MKM | $\mathrm{C}{\mathrm{r}}_{2}{\mathrm{O}}_{3}$(0001) | CSTR, PFR | GHSV: 100–20,000 h${}^{-1}$; 650–1500 K, 0.1–10 bar | ∼5% (950 K); ∼40% (1200 K); ≲95% (1500 K) | ∼90% 2-butene; ∼20% butadiene | significant deactivation after 10 h (Figure 13) |

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**MDPI and ACS Style**

Skubic, L.; Sovdat, J.; Teran, N.; Huš, M.; Kopač, D.; Likozar, B.
Ab Initio Multiscale Process Modeling of Ethane, Propane and Butane Dehydrogenation Reactions: A Review. *Catalysts* **2020**, *10*, 1405.
https://doi.org/10.3390/catal10121405

**AMA Style**

Skubic L, Sovdat J, Teran N, Huš M, Kopač D, Likozar B.
Ab Initio Multiscale Process Modeling of Ethane, Propane and Butane Dehydrogenation Reactions: A Review. *Catalysts*. 2020; 10(12):1405.
https://doi.org/10.3390/catal10121405

**Chicago/Turabian Style**

Skubic, Luka, Julija Sovdat, Nika Teran, Matej Huš, Drejc Kopač, and Blaž Likozar.
2020. "Ab Initio Multiscale Process Modeling of Ethane, Propane and Butane Dehydrogenation Reactions: A Review" *Catalysts* 10, no. 12: 1405.
https://doi.org/10.3390/catal10121405