The role of induction heating in catalytic propane dehydrogenation

The catalytic propane dehydrogenation (PDH) reaction was carried out in a bench-scale fluidized bed utilizing both experimental and computational methods. In order to investigate the reaction kinetics of CrOx-based catalysts, an Eulerian numerical model was utilized in conjunction with a modified energy-minimization multiscale (EMMS) drag model. On the basis of which, the effects of the catalyst packing temperature, the propane weight hourly space velocity (WHSV), and the PDH catalyst composition on propane conversion were evaluated. The results revealed that, when the catalyst packing temperature increased from 823 to 923 K, the conversion rose by 104.93, 121.91, and 134.51%, for the inlet propane WHSVs of 1.24, 2.49, and 3.73 h–1, respectively. With increasing the propane WHSV from 1.24 to 4.98 h–1, the conversion dropped by 52.72, 45.62, and 39.35 %, for catalyst temperatures of 848, 873, and 923 K, respectively. The conversions with the CrOx-based catalyst were 1.5 to 2.5 times that of the Pt-based catalyst. Multivariate correlation for propane conversion was fitted, yielding an average discrepancy of 4.38%.

Catalytic propane dehydrogenation has been tested on different reactor configurations employing Pt–Sn/MgAl2O4 as a catalyst. Hollow fiber palladium membranes coupled to the two-zone fluidized bed reactor (TZFBR) combine the possibility of improving propane conversion by hydrogen removal from the reaction bed through the membrane with in situ catalyst regeneration in the lower section of the TZFBR. Experiments have been carried out at different reaction temperatures and time on stream. In addition, the optimum regenerative agent flow fraction (diluted oxygen) to be fed into the TZFBR has been determined at the reaction temperatures between 500 °C and 600 °C to get a constant catalytic activity without net deactivation. Moreover, the TZFBR with palladium membranes has been successfully tested, displacing the reaction equilibrium towards the production of propylene, and still keeping steady state in the catalytic propane dehydrogenation. These results were better than those reported in the literature for conventional reactors.

Several reactor configurations have been tested for catalytic propane dehydrogenation employing Pt-Sn/MgAl2O4 as a catalyst. Pd-Ag alloy membranes coupled to the multifunctional Two-Zone Fluidized Bed Reactor (TZFBR) provide an improvement in propane conversion by hydrogen removal from the reaction bed through the inorganic membrane in addition to in situ catalyst regeneration. Twofold process intensification is thereby achieved when compared to the use of traditional fluidized bed reactors (FBR), where coke formation and thermodynamic equilibrium represent important process limitations. Experiments were carried out at 500–575 °C and with catalyst mass to molar flow of fed propane ratios between 15.1 and 35.2 g min mmol−1, employing three different reactor configurations: FBR, TZFBR and TZFBR + Membrane (TZFBR + MB). The results in the FBR showed catalyst deactivation, which was faster at high temperatures. In contrast, by employing the TZFBR with the optimum regenerative agent flow (diluted oxygen), the process activity was sustained throughout the time on stream. The TZFBR + MB showed promising results in catalytic propane dehydrogenation, displacing the reaction towards higher propylene production and giving the best results among the different reactor configurations studied. Furthermore, the results obtained in this study were better than those reported on conventional reactors.

Newly reported integrated processes are discussed for aliphatic (paraffin) hydrocarbon dehydrogenation into olefins and subsequent polymerization into polyolefins (e.g., propane to propylene to polypropylene, ethane to ethylene to polyethylene). Catalytic dehydrogenation membrane reactors (permreactors) made by inorganic or metal membranes are employed in conjunction with fluid bed polymerization reactors using coordination catalysts. The catalytic propane dehydrogenation is considered as a sample reaction in order to design an integrated process of enhanced propylene polymerization. Related kinetic experimental data of the propane dehydrogenation in a fixed bed type catalytic reactor is reviewed which indicates the molecular range of the produced C1-C3 hydrocarbons. Experimental membrane reactor conversion and yield data are also reviewed. Experimental data were obtained with catalytic membrane reactors using the same catalyst as the non-membrane reactor. Developed models are discussed in terms of the operation of the reactors through computational simulation, by varying key reactor and reaction parameters. The data show that it is effective for catalytic permreactors to provide streams of olefins to successive polymerization reactors for the end production of polyolefins (i.e., polypropylene, polyethylene) in homopolymer or copolymer form. Improved technical, economic, and environmental benefits are discussed from the implementation of these processes.

Catalytic propane dehydrogenation (PDH) has mainly been studied using metal- and metal oxide-based catalysts. Studies on dehydrogenation catalysis by metal hydrides, however, have rarely been reported. In this study, PDH reactions using group IIIB and IVB metal hydride catalysts were investigated under relatively low-temperature conditions of 450 °C. Lanthanum hydride exhibited the lowest activation energy for dehydrogenation and the highest propylene yield. Based on kinetics studies, a comparison between the reported calculation results and isotope experiments, the hydrogen vacancies of metal hydrides were involved in low-temperature PDH reactions.

The use of solid oxygen carriers (SOCs) in catalytic dehydrogenation may provide a more efficient production process for small alkenes by shifting the equilibrium to the product side. In this paper we use dynamic simulations to investigate the feasibility of two-step oxidative dehydrogenation of propane to propene using a SOC. The proposed process is carried out in a cyclically operated fixed-bed reactor, filled with a mixture of a dehydrogenation catalyst and a SOC. In the first step (the dehydrogenation), propane is fed to the reactor. The SOC oxidises the hydrogen produced during the dehydrogenation. In the second step, the SOC is regenerated and the accumulated coke burned off by allowing oxygen into the reactor. We determine the cyclic steady states by simulating the process for different feed temperatures and SOC concentrations, and we show that addition of a SOC to a reactor filled with dehydrogenation catalyst increases the conversion of propane and enhances the selectivity towards propene.

Propane Oxydehydrogenation to Propylene Over Molybdenum-based Catalysts

A reduction in catalyst's activity with time-on-stream and the formation of side products are two of the problems associated with catalytic propane dehydrogenation (PDH). Previous studies have indicated that the presence of small amounts of oxygenated additives such as water can reduce coke formation and enhance catalyst activity. The aim of the present work was to develop an appropriate kinetic model for PDH over a commercial Pt–Sn/γ-Al2O3 catalyst in the presence of small amounts of water. Experimental data were obtained from a previous study where catalytic PDH was carried out in a bench scale reactor system at atmospheric pressure in the temperature range of 575–620°C in the presence of different amounts of water. The kinetics of the main dehydrogenation reaction were described in terms of a Langmuir-Hinshelwood rate expression and the effects of water on coke deposition and catalyst sintering were considered in a catalyst deactivation model to explain the observed optimum level in the amount of added water.

Propene, used on a large scale to manufacture polypropylene and several commodity chemicals, is increasingly produced by catalytic propane dehydrogenation (PDH). Atomically dispersed Pt has emerged as a promising candidate catalyst for PDH; however, stabilizing atomically dispersed Pt at high temperatures is challenging. Here, we demonstrate the use of dealuminated zeolite beta with a high Fe content as a host for stabilizing isolated Pt, which is anchored strongly to the zeolite support by Pt-Fe bonds. The isolated Pt-Fe sites exhibit promising PDH performance, including a high apparent forward rate coefficient for propene formation (404.8-26.4 mol propene/mol Pt·bar·s) and a high selectivity (≥96%) at 823 K in the presence of H2. Kinetics data characterizing the rate of PDH with a range of Pt loadings show that atomically dispersed Pt catalyzes propene formation at rates independent of H2 partial pressure, whereas metallic Pt clusters, formed at high Pt loadings, catalyze the reaction with a slightly negative dependence on H2 partial pressure. The shift in Pt speciation with Pt loading, confirmed by infrared spectroscopy of adsorbed CO, X-ray absorption spectroscopy, and high-angle angular dark field scanning transmission electron microscopy, suggests that the observed change in kinetics with Pt dispersion is a consequence of a change in the reaction mechanism.

Catalytic propane dehydrogenation is the targeted and most efficient industrial method of propylene production. The practical significance of this method is growing given the relative availability of propane as a feedstock. The review considered the prospects of developing new generation propane dehydrogenation catalysts based on transition metal oxides (Zn, Ga, Co and V), which can compete with commercial platinum- and chromium-containing catalysts. The review will announce a series of publications on this topic as part of the scientific research supported by the Russian Science Foundation.

Platinum-based supported intermetallic alloys (IMAs) demonstrate exceptional performance in catalytic propane dehydrogenation (PDH) primarily because of their remarkable resistance to coke formation. However, these IMAs still encounter a significant hurdle in the form of catalyst deactivation. Understanding the complex deactivation mechanism of supported IMAs, which goes beyond conventional coke deposition, requires meticulous microscopic structural elucidation. In this study, we unravel a nonclassical deactivation mechanism over a PtZn/γ-Al2O3 PDH catalyst, dictated by the PtZn to Pt3Zn nanophase transformation accompanied with dezincification. The physical origin lies in the metal support interaction (MSI) that enables strong chemical bonding between hydroxyl groups on the support and Zn sites on the PtZn phase to selectively remove Zn species followed by the reconstruction towards Pt3Zn phase. Building on these insights, we have devised a solution to circumvent the deactivation by passivating the MSI through surface modification of γ-Al2O3 support. By exchanging protons of hydroxyl groups with potassium ions (K) on the γ-Al2O3 support, such a strategy significantly minimizes the dezincification of PtZn IMA via diminished metal-support bonding, which dramatically reduces the deactivation rate from 0.2044 to 0.0587 h-1. These findings decode the nonclassical PDH deactivation mechanism over supported IMA catalysts and elaborate a new logic for the design of high-performance IMA based PDH catalysts with long-term stability.

Co/Al2O3 catalysts with different Co3O4 loadings were studied in catalytic dehydrogenation of propane. The optimal results of 21.5 wt% propylene yield and 83.6 % selectivity were obtained at 5 wt% loading. XRD, DRS and XPS results showed that at loadings below 10 wt%, the “surface Co spinel” formed from tetrahedral Co2+ ions during the course of reaction constituted the active site for dehydrogenation reaction. Whereas at high loadings (above 10 wt%), only Co3O4 crystallites presented, which were easily reduced to metallic Co species, resulting in dramatically enhanced cracking reaction and the formation of abundant methane.

Catalytic dehydrogenation of propane over a PtSn/SiO2 catalyst with oxygen addition: Selective oxidation of H2 in the presence of hydrocarbons

Catalytic propane dehydrogenation is an attractive method to produce propylene while avoiding the issues of its traditional synthesis via naphtha steam cracking of naphtha. In this contribution, a series of Pt-Sn/SBA-16 catalysts were synthesized and evaluated for this purpose. Bimetallic Pt-Sn catalysts were more active than catalysts containing only Pt. The catalyst with the best performance was assessed at different reaction times of 0, 60, 180, and 300 min. The evolution of coke deposits was also studied. Thermogravimetric analysis demonstrated the presence of two types of coke on the catalyst surface at low and high temperature, respectively. Raman results showed an increased coke’s crystal size from 60 to 180 min on stream, and from 180 to 300 min under reaction, Raman suggested a reduction in the crystal size of coke. Also transmission electron microscopy confirmed a more evident agglomeration of metallic particles with reaction times higher than 180 min. These results are consistent with the phenomena called “coke migration” and the cause is often explained by coke movement near the particle to the support; it can also be explained due to sintering of the metallic particle, which we propose as a more suitable explanation.

This paper describes the synthesis and application of γ-Al2O3 supported SmCoO3 perovskite-type oxide in the catalytic propane dehydrogenation to propene. Various techniques including X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR), transmission electron microscopy (TEM), thermogravimetric analysis (TG) and X-ray photoelectron spectra (XPS) were used to characterize the physico-chemical properties of SmCoO3/Al2O3 and derived Co-based catalyst. The characterization results reveal that the perovskite lattice confinement can lead to better dispersed cobalt oxide and restrain the reduction to metallic Co species. Under the high weight hourly space velocity (3 h−1), the propane conversion and propene selectivity of the reduced SmCoO3/Al2O3 catalyst were 25% and 94%, respectively, and obviously higher than those of the reduced SmCoO/Al2O3 catalyst used as a referential sample prepared by an incipient wetness impregnation method. A large amount of coke was formed over the used SmCoO/Al2O3 catalyst. Instead, the SmCoO3/Al2O3-derived Co-based catalyst can greatly reduce the amount of coke deposition. The superior catalytic performance and anti-coking ability of SmCoO3/Al2O3 catalyst are attributed to the formation of a large amount of well-dispersed surface Co2+ species, especially small CoO nanoparticles, and the absence of metallic Co species.