Propane Conversion Research Articles

Effect of supports on the kind of in-situ formed ZnOx species and its consequence for non-oxidative propane dehydrogenation

Non-oxidative propane dehydrogenation (PDH) to propene is the basis of various large-scale processes suffering however from high costs or environmental incompatibility of currently applied Pt- or Cr-containing catalysts. Herein, we demonstrate that active and selective catalysts can be obtained from cheap and commercially available Zr- or Ti-based supports and ZnO without producing any liquid or solid waste. Catalytically active species formed in situ under PDH conditions are composed of isolated ZnOx as concluded from X-ray absorption spectroscopic analysis. The kind of support affects the geometry of such species that is probably decisive for catalyst activity. ZnOx on the surface of LaZrOx revealed the highest Zn-related TOF of propene formation. However, the following activity order in terms of space time yield of propene formation (STYC3H6) at 550 °C and about 50% equilibrium propane conversion using a feed with 40 vol% propane was obtained: ZnO//TiZrOx > ZnO//SiZrOx > ZnO//LaZrOx > ZnO//TiO2. The best-performing catalyst showed STYC3H6 of 2 kg kgcat−1 h−1 and was durable in 8 PDH/regeneration cycles. Temporal analysis of products with submillisecond resolution suggests that H2 formation should be the rate-determining step in the course of the PDH reaction.

Effective perovskite catalysts based on rare earth vanadites for propane cracking in associated petroleum gas processing technologies

The process of propane cracking in the presence of rare earth vanadites was explored. It was shown that the samples can be attributed to mesoporous catalysts, which also contain a small amount of micropores. It was revealed that the propane conversion and the yield of light olefins grew up with an increase in the molecular weight of a catalyst, while the ethylene and propylene selectivities were enhanced; the propane conversion reached a maximum value of 96.5% with ethylene and propylene selectivities of 69.4 and 26.5%, respectively, when europium vanadite was used as a catalyst.

Enriching GaHx species via co-feeding hydrogen to boost efficient propane dehydrogenation over Ga2O3/Al2O3 catalysts

With the demand for propene and the development of shale gas, propane dehydrogenation is an effective strategy to tackle the tight propene supply. Ga-based catalysts have immense potential for propane dehydrogenation among many environmentally friendly non-precious metal catalysts. Herein, we found that the hydrogen co-feeding not only significantly improved the activity but also enhanced the stability of Ga/Al-R catalyst for propane dehydrogenation. The propane conversion rates at zero reaction time at a hydrogen concentration of 10% was 81 mmolC3H8gcat−1h−1, almost twice as high as in the absence of hydrogen (43.8 mmolC3H8gcat−1h−1). In addition, co-feeding with hydrogen significantly enhanced catalyst stability and resistance to carbon deposition. In-situ IR spectroscopy confirmed that the addition of hydrogen could effectively contribute to the production and enrichment of GaHx species. The H2-D2 exchange and elimination of GaHx species by CO2 experiments demonstrated that GaHx species was the more active site for PDH over Ga/Al-R catalyst.

Highly active and stable Y2O3 promoted TiO2-ZrO2 catalyst for propane dehydrogenation

The introduction of TiO2 has been proved to improve the reactivity of ZrO2 for propane dehydrogenation for the first time. The enhanced propane conversion for TiO2-2ZrO2 sample is mainly attributed to the increased number of active Zrcus sites and the corresponding oxygen vacancies. While the consequent excessive aciditypromoting secondary reactions is unfavorable for the selectivity to propene. Fortunately, the additionally doped Y2O3 increases both the conversion of propane and the selectivity to propene due to further incremental Zrcus sites and decreased acidity. The yield of propene remains at 34% for the optimal 5Y2O3/TiO2-2ZrO2 catalyst over the continuous 20 reaction-regeneration cycles. In addition, the adsorption mode of propane on the catalyst is determined to be a two-site mode with H atoms in methyl and methylene groups (di-σ-bonded propylene) using an in-situ FTIR technique, and the possible reaction route has also been speculated.

XPS and HR TEM Elucidation of the Diversity of Titania-Supported Single-Site Ir Catalyst Performance in Spin-Selective Propene Hydrogenation

Immobilized [Ir(COD)Cl]2-Linker/TiO2 catalysts with linkers containing Py, P(Ph)2 and N(CH3)2 functional groups were prepared. The catalysts were tested via propene hydrogenation with parahydrogen in a temperature range from 40 °C to 120 °C which was monitored via NMR. The catalytic behavior of [Ir(COD)Cl]2-Linker/TiO2 is explained on the basis of quantitative and qualitative XPS data analysis performed for the catalysts before and after the reaction at 120 °C. It is shown that the temperature dependence of propene conversion and the enhancement of the NMR signal are explained via a combination of the stabilities of both the linker and immobilized [Ir(COD)Cl]2 complex. It is demonstrated that the N(CH3)2-linker is the most stable at the surface of TiO2 under used reaction conditions. As a result, only this sample shows a rise in the enhancement of the NMR signal in the 100–120 °C temperature range.

Activation of Cr2O3 for propane dehydrogenation by doping with Pt single-atom promotor

In this work, we evaluate reaction mechanism and kinetics of propane dehydrogenation (PDH) over Pt single-atom-doped Cr2O3 catalyst by combining density functional theory calculations and microkinetic analysis. Pt single-atom-doped Cr2O3 achieves superior propane conversion and propene selectivity to PtSn alloy and pristine Cr2O3 under typical operating conditions. Pt serves as a promoter to activate nearby Cr-O Lewis-Pair sites. The promotion effect of Pt single-atom on activity is attributed to the lowered energy level of conduction band minimum of nearby O Lewis-base site, enhancing its H capture ability and accordingly facilitating first step of dehydrogenation of propane. The Pt single-atom promoter also enhances propene selectivity by adjusting the Cr-O Lewis acid-base interaction with the deep dehydrogenation product, impeding deep dehydrogenation process. This work provides theoretical insights into the feasibility of atom-level dispersion Pt promoter activating CrOx-based catalysts for PDH process, and guidance for future rational design of other oxide-supported single-atom catalysts for PDH.

Modeling the Selectivity of Hydrotalcite-Based Catalyst in the Propane Dehydrogenation Reaction.

The propylene production processes currently used in the petrochemical industry (fluid catalytic cracking and steam cracking of naphtha and light diesel) are unable to meet the increase of propylene demand for industrial applications. For this reason, alternative processes for propylene production have been investigated, and among the others, the propane dehydrogenation (PDH) process, allowing the production of propylene as a main product, has been industrially implemented (e.g., Catofin and Oleflex processes). The main drawback of such processes is closely linked to the high temperature required to reach a sustainable propane conversion that affects catalyst stability due to coke formation on the catalyst surface. Accordingly, the periodic regeneration of the catalytic bed is required. In this work, the performance in the PDH reaction of different Sn-Pt catalysts, prepared starting by alumina- and hydrotalcite-based supports, is investigated in terms of propane conversion and selectivity to propylene in order to identify a more stable catalyst than the commercial ones. The experimental tests evidenced that the best performance was obtained using the catalyst prepared on commercial pellets of hydrotalcite PURALOX MG70. This catalyst has shown, under pressure conditions of 1 and 5 bar (in order to evaluate the potential future application in integrated membrane reactors), propane conversion values close to the thermodynamic equilibrium ones in all of the investigated temperature ranges (500-600 °C) and the selectivity was always higher than 95%. So, this catalyst was also tested in a stability run, performed at 500 °C and 5 bar: the results highlighted the loss of only 12% in the propane conversion with no changes in the selectivity to propylene. Properly designed experimental tests have also been performed in order to evaluate the kinetic parameters, and the developed mathematical model has been optimized to effectively describe the system behavior and the catalyst deactivation.

Self-evolved BOx anchored on Mg2B2O5 crystallites for high-performance oxidative dehydrogenation of propane

Oxidative dehydrogenation of propane (ODHP) is a promising process for producing propene. Recently, some boron-based catalysts have exhibited excellent olefin selectivity in ODHP. However, their complex synthetic routes and poor stability under high-temperature reaction conditions have hindered their practical application. Herein, we report a self-evolution method rather than conventional assembly approaches to acquire structures with excellent stability under a high propane conversion, from a single precursor-MgB2. The catalyst feasibly prepared and optimized exhibited a striking performance: 60% propane conversion with a 43.2% olefin yield at 535°C. The BOx corona pinned by the strong interaction with the borate enabled zero loss of the high conversion (around 40%) and olefins selectivity (above 80%) for over 100h at 520°C. This all-in-one strategy of deriving all the necessary components from just one raw chemical provides a new way to synthesize effective and economic catalysts for potential industrial implementation.

CO and Propane Combustion on La0.8Sr0.2CoxFe1−xO3−δ Perovskites: Effect of Fe-to-Co Ratio on Catalytic Activity

Perovskites are promising alternative catalysts for oxidation reactions due to their lower cost compared to noble metals, and their greater thermal stability. The catalytic oxidation of CO is essential in order to control CO emissions in a series of applications whereas the catalytic combustion of propane is considered an economical and environmentally acceptable solution for energy production and gaseous pollutant management, since propane is among the organic compounds involved in photochemical reactions. This work concerns the effect of the Co/Fe ratio in the B-sites of a series of eight La0.8Sr0.2CoxFe1−xO3−δ perovskites, with x ranging from 0 to 1, on the catalytic activity towards CO and C3H8 oxidation. The perovskite oxides were synthesized using the combustion synthesis method and characterized with respect to their specific surface areas, structures, and reduction properties. Increasing the Co/Fe ratio resulted in an increase in CO and propane conversion under both oxidative and stoichiometric conditions. The increase in Co content is considered to facilitate the formation of oxygen vacancies due to the lower redox stability of the cobalt cations compared to iron cations, favoring oxygen ion mobility and oxygen exchange between the gas phase and the oxide surface, thus enhancing the catalytic performance.

Boosting the performances of protonic solid oxide fuel cells for co-production of propylene and electricity from propane by integrating thermo- and electro- catalysis

Protonic solid oxide fuel cells (p-SOFC) integrated with clean thermal energy sources are promising platforms for decarbonized chemical production in addition to power generation, such as on-purpose propylene production from propane dehydrogenation (PDH). The catalytic performance of the conventional nickel-cermet-based anode materials in p-SOFC for propane conversion is restrained by their low active surface area and proneness to coking. In this work, by integration of a highly efficient industry-relevant thermal catalyst PtGa/ZSM-5 for PDH reaction, we demonstrate that both the electrochemical and catalytic performance of the propane-fueled p-SOFC can be effectively enhanced. The PtGa catalyst integrated p-SOFC exhibits a peak power density of 93 mW cm−2 at 600 °C, which is greater by about 100% and 50% than that without catalyst or with a perovskite-based (Pr0.3Sr0.7)0.9Ni0.1Ti0.9O3 (PSNT) catalyst layer, respectively. The PDH activity and olefin selectivity of the PtGa catalyst is also significantly higher than that of the PSNT catalyst. In addition, much improved coke tolerance and propylene selectivity (over 90%) compared to the catalyst-free Ni-cermet anode materials were achieved by integrating the industrial catalyst layer. The propane conversion can be further improved by an applied current density, whereas the olefin selectivity is almost unaltered. The excellent performance of the PtGa catalyst integrated p-SOFC is attributed to the high surface area, intrinsically high catalytic activity, selectivity, and anti-coking properties of the catalytic layer for propane conversion. This work provides a general approach and a case study for boosting the performances of p-SOFCs in chemical production by integrating thermo- and electro- catalysis.

Selective Conversion of Propane by Electrothermal Catalysis in Proton Exchange Membrane Fuel Cell.

Electrochemical conversion of alkanes to high value-added oxygenated products under a mild condition is of significance. Herein, we effectively couple the electrocatalysis of H2 O2 with the thermo-catalysis of propane oxidation in the cathode of proton exchange membrane fuel cell. Specifically, H2 O2 is in-situ generated on the nitric acid-treated carbon black (C-acid) via 2e- process of oxygen reduction reaction, and then transports to the Fe active sites of MIL-53 (Al, Fe) metal-organic frameworks for propane oxidation. Based on this strategy, the space-time yield of C3 oxygenated products of propane oxidation reaches 2.65 μmol h-1 cm-2 , which represents a new benchmark for electrochemical alkane oxidation in the fuel-cell-type electrolyzer. This study highlights the importance of multifunctional composite catalysts in the field of electrosynthesis.

High propylene selectivity in methanol conversion over metal (Sm, Y, and Gd) modified HZSM-5 catalysts in the methanol to propylene process

A protonated form of Zeolite Socony Mobil-5 (H-ZSM-5) catalyst (with Si/Al = 200) was synthesized through a hydrothermal method from various sources of silica, including Ludox, silicic acid, and tetraethyl orthosilicate. We also investigated the effect of loading the catalyst with yttrium (Y), samarium (Sm), and gadolinium (Gd), respectively, on the acidic properties of the catalyst. We compared the catalytic performance of the catalysts with different loadings in methanol to hydrocarbon conversion. The catalysts were characterized using X-ray diffraction analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, surface area analysis measurements, thermogravimetric analysis, and temperature-programmed desorption. Among the metal-loaded Ludox-based H-ZSM-5 catalysts (LHZs), the Sm/LHZ catalyst had the best performance with 68.8 % propylene selectivity due to its high amount of weak and intermediate acid sites at 480 °C, WHSV = 1 h−1 in a methanol to propylene conversion. However, the Gd-LHZ catalyst significantly increased the selectivity toward ethane and propane during the conversion.

Fe-doped MnO2 as an efficient catalyst for low temperature propane oxidation

Manganese oxides were received extensive attention on account of its low cost, variable valence state and excellent redox properties. Herein, we successfully prepared various Fe-doped MnO2 catalysts to further improve the catalytic activity of MnO2 on propane. Physicochemical characterization results displayed that with the increase of Fe doping amounts, the crystalline phase of MnO2 gradually changed from α-MnO2 and β-MnO2 to Fe2O3, the particle size of catalysts decreased and the specific surface area increased. However, increasing the content of Fe could not monotonically enhance the catalytic performance of catalysts on propane. When the molar ratio of Fe/Mn was 0.25, the largest amount of Mn4+ species and lattice oxygen species were exposed on the surface of Mn8Fe2, and showed the best low temperature reducibility, which was ascribed to the synergistic effect between Mn and Fe was enhanced. It presented optimal catalytic activity for propane oxidation with temperature of propane conversion at 90% (T90) as low as 279 °C under 0.1% propane and 5% O2. This work provided a new way to design and synthesize efficient non-noble metal catalysts for the elimination of propane, which had certain application value.

Photo-thermal synergistic catalytic oxidative dehydrogenation of propane over a spherical superstructure of boron carbon nitride nanosheets

The oxidative dehydrogenation of propane (ODHP) is an attractive reaction for increasing the production of light olefins due to its favorable thermodynamic and kinetic characteristics. However, the overoxidation of propene to thermodynamically favored COx leads to a trade-off between propane conversion and propene selectivity, limiting the optimization of the overall catalytic performance. Here we show that photo-thermal synergistic catalysis driven by a spherical superstructure of semiconducting boron carbon nitride nanosheets (SS-BCNNSs) breaks the conversion–selectivity trade-off, resulting in a remarkable enhancement of propane conversion, along with a well-maintained selectivity for propene under mild conditions. The mechanism study shows that the introduction of light irradiation during the ODHP process could change the reaction order, activate the reactants, and reduce the activation energy for ODHP. DFT calculations reveal that the photogenerated electrons provided by SS-BCNNSs promote oxygen adsorption and significantly reduce the energy barrier for generating active B-O·species, which in turn produces more active sites and enhances the reactivity.

Effect of Mo content on oxidative dehydrogenation of propane with CO2 over ZnOx catalysts supported on Mo–Zr mixed–oxides

The production of propylene from readily available propane sources is of great importance as it serves as a crucial building block for producing numerous value-added chemicals. Oxidative dehydrogenation of propane with carbon dioxide (ODPC) has been proposed as a viable and eco-friendly approach for simultaneous propylene production and carbon dioxide reduction. In this study, ZnOx catalysts were prepared by supporting them on a range of molybdenum–zirconium (Mo–Zr) mixed–oxides with varying Mo contents, aiming to utilize them for ODPC applications. The incorporation of suitable quantities of Mo in zirconium dioxide (ZrO2) supports increases the surface concentration and enhances the dispersion of ZnOx, thereby demonstrating promotional effects on the surface properties of the supported ZnOx catalysts. Notably, the ZnOx catalyst supported on a Mo–Zr mixed–oxide, with an optimized Mo content, exhibits a propane conversion rate more than two-fold higher than that of the catalyst without Mo in ODPC. Furthermore, the introduction of Mo into the ZrO2 supports effectively inhibits the formation of coke by suppressing the cleavage of C–C bonds in propane. In comparison, the supported ZnOx catalysts with higher Zn loadings, show that a Mo–Zr mixed–oxide support effectively suppresses the formation of bulk ZnOx more than an unmodified ZrO2 support, leading to improved ODPC performance. The promoting effects of Mo emphasize the potential of utilizing mixed–oxide supports for ZnOx catalysts in ODPC, demonstrating a promising opportunity for enhancing catalytic performance.

Surface Chemistry and Catalytic Reactivity of Borocarbonitride in Oxidative Dehydrogenation of Propane

AbstractBorocarbonitride (BCN) materials are newly developed oxidative dehydrogenation catalysts that can efficiently convert alkanes to alkenes. However, BCN materials tend to form bulky B2O3 due to over‐oxidation at the high reaction temperature, resulting in significant deactivation. Here, we report a series of super stable BCN nanosheets for the oxidative dehydrogenation of propane (ODHP) reaction. The catalytic performance of the BCN nanosheets can be easily regulated by changing the guanine dosage. The control experiment and structural characterization indicate that the introduction of a suitable amount of carbon could prevent the formation of excessive B2O3 from BCN materials and maintain the 2D skeleton at a high temperature of 520 °C. The best‐performing catalyst BCN exhibits 81.9 % selectivity towards olefins with a stable propane conversion of 35.8 %, and the propene productivity reaches 16.2 mmol h−1 g−1, which is much better than hexagonal BN (h‐BN) catalysts. Density functional theory calculation results show that the presence of dispersed rather than aggregated carbon atoms can significantly affect the electronic microenvironment of h‐BN, thereby boosting the catalytic activity of BCN.

Surface Chemistry and Catalytic Reactivity of Borocarbonitride in Oxidative Dehydrogenation of Propane.

Borocarbonitride (BCN) materials are newly developed oxidative dehydrogenation catalysts that can efficiently convert alkanes to alkenes. However, BCN materials tend to form bulky B2 O3 due to over-oxidation at the high reaction temperature, resulting in significant deactivation. Here, we report a series of super stable BCN nanosheets for the oxidative dehydrogenation of propane (ODHP) reaction. The catalytic performance of the BCN nanosheets can be easily regulated by changing the guanine dosage. The control experiment and structural characterization indicate that the introduction of a suitable amount of carbon could prevent the formation of excessive B2 O3 from BCN materials and maintain the 2D skeleton at a high temperature of 520 °C. The best-performing catalyst BCN exhibits 81.9 % selectivity towards olefins with a stable propane conversion of 35.8 %, and the propene productivity reaches 16.2 mmol h-1 g-1 , which is much better than hexagonal BN (h-BN) catalysts. Density functional theory calculation results show that the presence of dispersed rather than aggregated carbon atoms can significantly affect the electronic microenvironment of h-BN, thereby boosting the catalytic activity of BCN.

Enabling High Activity Catalyst Co3O4@CeO2 for Propane Catalytic Oxidation via Inverse Loading.

Propane catalytic oxidation is an important industrial chemical process. However, poor activity is frequently observed for stable C-H bonds, especially for non-noble catalysts in low temperature. Herein, we reported a controlled synthesis of catalyst Co3O4@CeO2-IE via inverse loading and proposed a strategy of oxygen vacancy for its high catalytic oxidation activity, achieving better performance than traditional supported catalyst Co3O4/CeO2-IM, i.e., the T50 (temperature at 50% propane conversion) of 217 °C vs. 235 °C and T90 (temperature at 90% propane conversion) of 268 °C vs. 348 °C at the propane space velocity of 60,000 mL g-1 h-1. Further investigations indicate that there are more enriched oxygen vacancies in Co3O4@CeO2-IE due to the unique preparation method. This work provides an element doping strategy to effectively boost the propane catalytic oxidation performance as well as a bright outlook for efficient environmental catalysts.

One‐pot synthesis of V doped mesoporous SiO2 catalysts for selective oxidation of ethane and propane

AbstractA series of vanadium‐doped mesoporous SiO2 catalysts were prepared using a one‐pot emulsion method. The effects of VOx species with different structures on C−H bond activation and product selectivity in ethane and propane selective oxidation were investigated using X‐ray diffraction (XRD), N2 adsorption‐desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman, ultraviolet‐visible diffuse reflectance spectroscopy (UV‐Vis DRS), hydrogen temperature programmed reduction (H2‐TPR), and ammonia temperature programmed desorption (NH3‐TPD) characterizations. The results revealed that the highly dispersed isolated tetrahedral VOx species on the catalyst gradually polymerized into highly dispersed oligomeric VOx species with the increased V loading. The former is beneficial for the formation of olefins and total aldehydes during the selective oxidation of propane. Oligomeric VOx species are conducive to improving the selectivity of ethylene and acetaldehyde in the selective oxidation of ethane. The highest catalytic performances for selective oxidation of ethane and propane were obtained at a temperature of 650 °C. The conversion of ethane was 41.6 %, with a corresponding yield of ethylene and acetaldehyde of 23.6 % over a 0.5 V−SiO2 catalyst. In contrast, the propane conversion was 61.5 %, with a corresponding total yield of olefins and aldehydes of 41.3 % over a 1.0 V−SiO2 catalyst.

Tandem propane dehydrogenation and surface oxidation catalysts for selective propylene synthesis.

Direct propane dehydrogenation (PDH) to propylene is a desirable commercial reaction but is highly endothermic and severely limited by thermodynamic equilibrium. Routes that oxidatively remove hydrogen as water have safety and cost challenges. We coupled chemical looping-selective hydrogen (H2) combustion and PDH with multifunctional ferric vanadate-vanadium oxide (FeVO4-VOx) redox catalysts. Well-dispersed VOx supported on aluminum oxide (Al2O3) provides dehydrogenation sites, and adjacent nanoscale FeVO4 acts as an oxygen carrier for subsequent H2 combustion. We achieved an integral performance of 81.3% propylene selectivity at 42.7% propane conversion at 550°C for 200 chemical looping cycles for the reoxidization of FeVO4. Based on catalytic experiments, spectroscopic characterization, and theory calculations, we propose a hydrogen spillover-mediated coupling mechanism. The hydrogen species generated at the VOx sites migrated to adjacent FeVO4 for combustion, which shifted PDH toward propylene. This mechanism is favored by the proximity between the dehydrogenation and combustion sites.