Coke Deposition on Pt-Based Catalysts in Propane Direct Dehydrogenation: Kinetics, Suppression, and Elimination

Abstract

Pt-based catalysts are widely used in propane dehydrogenation to meet the dramatically increased demand of propylene from an on-purpose catalytic process. Although the process has been commercialized with high selectivity for decades, the prevention of coke deposition is still a daunting challenge. Herein, in order to provide a full coverage of the impact of coke deposition, we critically analyze the process of coke formation on Pt-based catalyst. First, the intrinsic nature of coke, including composition, distribution, and effects, is presented. The developments of kinetics model of coke growth are discussed and compared to offer insight into mechanism of coke formation. Moreover, the focus is put on the ways to prevent coke, which included cofeeding reductant gas, promoter, and support engineering. The advantage and limitation of each method is well elaborated, and the unique working principle behind each prevention method is uncovered. The new developments of single atom/site and confined metal cluster strategies are indicated. The regeneration of the deactivated catalyst is also discussed, which has a direct influence on the coke elimination and metal dispersion. In the end, the possible optimization strategies are suggested for the future Pt catalyst rational design. The current work provides a comprehensive summary of the coke formation, which lays out a solid and essential base for the further developments of Pt catalysts in propane direct dehydrogenation.

Single Atoms Anchored in Hexagonal Boron Nitride for Propane Dehydrogenation from First Principles

“…[30] In addition to Pt, [1,31] Au [32][33] and Ru [34][35] are also popular singleatom systems. When combined with a thermally stable support such as h-BN, these SACs may offer attractive advantages for dehydrogenation of propane, especially in anti-coking and in improving the turnover frequency per Pt atom, as coke formation [36] is a known problem for the conventional Pt/ alumina catalyst where Pt exists as nanoclusters of 15-25 atoms. [25] Answering these questions computationally can help guide the experimental discovery of h-BN-supported single atoms for PDH.…”

Propylene Synthesis: Recent Advances in the Use of Pt-Based Catalysts for Propane Dehydrogenation Reaction

“…The exact composition of the coke is, to date, the subject of study. It has been suggested that the coke formed on PtSn-based catalysts in PDH reaction mainly consists of three kinds of species: aliphatics, aromatics and pregraphite, with the aliphatic one constituting most of the deposit, with the C/H ratio of around 1.5 [95]. Raman studies on exhausted Pt-Sn/SBA-16 catalysts have shown an increase in coke crystal size from 60 to 180 min on stream and from 180 to 300 min under reaction [96].…”

“…The cofeeding of hydrogen decreases the coke formation rate and increases the stability of the catalyst by removing the precursor of coke, while the cofeeding of water decreases the coke formation while increasing the activity by decreasing the apparent activation energy of propane conversion [95].…”

Process Intensification of the Propane Dehydrogenation Considering Coke Formation, Catalyst Deactivation and Regeneration—Transient Modelling and Analysis of a Heat-Integrated Membrane Reactor

“…The quasi steady-state assumption results from the significant higher reaction rates R 1 -R 5 (Equations ( 1)-( 5)) in comparison to the overall coke formation rate (Equation (18)). The squared difference between the experimental and simulated values is minimized for the parameter estimation by the objective function:…”

“…Thus, a periodic catalyst regeneration is necessary, reducing space-time yield and productivity. To avoid coke formation, various approaches are studied, such as the co-feed of hydrogen and steam, the structure and size of the active catalyst component, the effect of the catalyst promoter and the modification of the catalyst support [18]. In this contribution, the focus lays on the exothermic (ΔH R 0 = -118 kJ/mol) oxidative propane dehydrogenation with oxygen (ODH), since present oxygen depresses coking.…”