Dehydrogenation Of Light Alkanes Research Articles

Facile and Environmentally Friendly Synthesis of Ga2O3/MFI Catalysts for Propane Dehydrogenation.

A GaOx-based catalyst is recognized as a promising catalyst for dehydrogenation of light alkanes. Conventionally, impregnation and calcination are necessary processes for the loading of GaOx. However, the incomplete impregnation of gallium salt solution would generate wastewater, and the calcination for the dissociation of gallium salt would release harmful gases, such as SOx, NOx, and HCl. Meanwhile, the high temperature results in an excessive energy cost and undesired GaOx particle aggregation. Here, we report a facile and environmentally friendly method for the synthesis of GaOx-based catalysts. The gallium salt solution was replaced directly with liquid gallium (LG). Through a simple physical mixing method at room temperature, uniform GaOx nanoparticles with diameters of around 3.5 nm were loaded onto the surface of silicalite-1 (S-1). With the optimal GaOx/MFI catalyst, the propane conversion and propylene selectivity reached 22.9 and 90.1%, respectively, in the propane dehydrogenation reaction. The work offers a clean and economical strategy utilizing liquid metal (LM) as an impregnation solution for the preparation of GaOx-based catalysts.

Material Engineering Solutions toward Selective Redox Catalysts for Chemical-Looping-Based Olefin Production Schemes: A Review.

Chemical looping (CL) has emerged as a promising approach in the oxidative dehydrogenation (ODH) of light alkanes, offering an opportunity for significant reductions in emissions and energy consumption in the ethylene and propylene production industry. While high olefin yields are achievable via CL, the material requirements (e.g., electronic and geometric structures) that prevent the total conversion of alkanes to CO x are not clearly understood. This review aims to give a concise understanding of the nucleophilic oxygen species involved in the selective reaction pathways for olefin production as well as of the electrophilic oxygen species that promote an overoxidation to CO x products. It further introduces advanced characterization techniques such as X-ray photoelectron spectroscopy, Raman spectroscopy, electron paramagnetic resonance spectroscopy, and resonant inelastic X-ray scattering, which have been employed successfully in identifying such reactive oxygen species. To mitigate CO x formation and enhance olefin selectivity, material engineering solutions are discussed. Common techniques include doping of the bulk or surface and the deposition of functional coatings. In the context of energy consumption and CO2 intensity, techno-economic assessments of CL-ODH systems have predicted energy savings of up to 80% compared to established olefin production processes such as steam cracking or dehydrogenation. Finally, although their practical application has been limited to date, the potential advantages of the use of fluidized bed reactors in CL-ODH are presented.

STUDYING THE INFLUENCE OF ALKALINE TREATMENT AND MODIFICATION OF ZEOLITE ON ITS PHYSICAL-CHEMICAL AND CATALYTIC PROPERTIES IN THE PROCESS OF PROPANE CONVERSION TO OLEFIN HYDROCARBONS

In this work, the effect of alkaline treatment of ZSM-5 zeolite with a modulus of 100 on its physicochemical properties and activity in the process of converting propane into olefin hydrocarbons was investigated. The growing demand for lower olefins is driving the search for new ways to improve existing technologies and develop new, more efficient catalysts. Catalytic dehydrogenation of light alkanes is an alternative to the petrochemical method for producing lower olefins from cheap and available gas and oil and gas feedstocks. At the same time, dehydrogenation reactions of light alkanes have a number of features and limitations that determine the range of possible catalysts. Zeolites are a class of supports that, due to their large surface area, nanometer-sized pores, and good thermal stability, can be used to prepare catalysts for the dehydrogenation of C2−C4 alkanes. An important feature of crystalline high-silica zeolites is the ability to change their acidic properties under the influence of various pre-treatments, which opens up great opportunities for their regulation and, accordingly, the selection of the most effective catalyst for a particular chemical process. It has been shown that alkaline treatment of zeolite leads to the formation of an additional amount of mesopores, which, in turn, affects its catalytic properties in the process of converting propane into olefinic hydrocarbons. The dependence of the activity and selectivity of the zeolite catalyst on the concentration of the alkali solution used for its treatment has been established. It was found that treatment of the zeolite catalyst with a 1.0 M NaOH solution leads to an increase in its selectivity with respect to the formation of C2–C4 olefins from propane, which at a process temperature of 650 °C reaches 32.0% with a propane conversion of 81%. It has been shown that additional promotion of desilicated zeolite with magnesium or manganese increases its activity with respect to the formation of olefinic hydrocarbons from propane. For citation: Vosmerikov A.A., Vosmerikova L.N., Vosmerikov A.V. Studying the influence of alkaline treatment and modification of zeolite on its physical-chemical and catalytic properties in the process of propane conversion to olefin hydrocarbons. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 8. P. 50-58. DOI: 10.6060/ivkkt.20246708.11t.

Deactivation of an Fe-based catalyst in the dehydrogenation of light alkanes under H2S co-feeding: A case study

The effectiveness of a Ru-Fe/SiO2 catalyst, which exhibits excellent propane dehydrogenation with H2S co-feeding, was verified for the dehydrogenation of various lower alkanes. When the dehydrogenation characteristics of C2–C4 alkanes were evaluated under H2S co-feeding, the Ru-Fe/SiO2 catalyst exhibited a high dehydrogenation activity in all cases. However, a significant degradation tendency of the catalyst was observed when lighter alkanes with smaller carbon numbers were used as the feedstock. The deposition of coke (carbon) and solid sulfur and the reduction of Fe species were identified as the main factors responsible for catalyst degradation. To further evaluate the factors affecting catalyst degradation, the effect of co-feeding H2 with the gas feedstock on the catalyst performance was investigated. The reaction stability improved significantly with the co-feeding of H2 during ethane and propane dehydrogenation reactions. This outcome is attributed to the smooth reduction and removal of the carbon accumulated on the catalyst surface, which is the main cause of catalyst degradation.

Doping Efects on Ethane/Ethylene Dehydrogenation Catalyzed by Pt2X Nanoclusters.

The catalytic dehydrogenation of light alkanes is key to transform low-cost hydrocarbons to high value-added chemicals. Although Pt is extremely efficient at catalyzing this reaction, it suffers from coke formation that deactivates the catalyst. Dopants such as Sn are widely used to increase the stability and lifetime of Pt. In this work, the dehydrogenation reaction of ethane catalyzed by Pt3 and Pt2X (X=Si, Ge, Sn, P and Al) nanocatalysts has been studied computationally by means of density functional calculations. Our results show how the presence of dopants in the nanocluster structure affects its electronic properties and catalytic activity. Exploration of the potential energy surfaces show that non-doped catalyst Pt3 present low selectivity towards ethylene formation, where acetylene resulting from double dehydrogenation reaction will be obtained as a side product (in agreement with the experimental evidence). On the contrary, the inclusion of Si, Ge, Sn, P or Al as dopant agents implies a selectivity enhancement, where acetylene formation is not energetically favoured. These results demonstrate the effectiveness of such dopant elements for the design of Pt-based catalysts on ethane dehydrogenation.

Acid-leaching treated ZnO-based materials as highly efficient microwave catalysts for oxidative dehydrogenation of propane by CO2

The oxidative dehydrogenation of propane by CO2 (CO2-ODHP) reaction has received much attention for its potential to produce high-value propylene from two underutilized reactants and to eliminate CO2. However, it is a great challenge to maintain high propylene selectivity with high propane conversion for CO2-ODHP reaction, especially for non-expensive and environmentally friendly catalysts. Herein, a new and effective ZnO/S-1(1.0)-based microwave catalyst for CO2-ODHP was developed by a simple impregnation method and acid leaching treatment. Interestingly, the acid leaching treatment significantly enhanced the catalytic activity and stability. Importantly, both the conversion of propane and the selectivity of propylene were significantly enhanced in the microwave catalytic reaction mode (MCRM). An amazingly high conversion of ∼60 % and selectivity of ∼92 % is achieved. This method of significantly improving the catalytic activity and stability after a simple acid leaching treatment can provide some inspiration for light alkane dehydrogenation reactions.

Kinetic Insights into Boron-Based Materials Catalyzed Oxidative Dehydrogenation of Light Alkanes.

High selectivity toward alkenes in oxidative dehydrogenation (ODH) of light alkanes makes boron-based materials promising catalysts. However, many key mechanistic aspects are still debated due to the challenge of capturing fleeting reaction intermediates. Kinetic analysis, including determining reaction orders and activation energy, could be informative for reactions involving radical intermediates but has not been extensively exploited. This Review summarizes the current understanding of the apparent alkane reaction order and the apparent activation energy in the boron-catalyzed ODH. Despite varying compositions and structures, a majority of boron-based catalysts share many common features, including alkene selectivity, the evolution and the formation of active site, and the apparent kinetic properties. These common trends could be attributed to the shared gas-phase radical-mediated reaction pathways and the formation of active hydroxylated boron oxide species on boron-containing materials under ODH conditions. Values of apparent alkane reaction orders and apparent activation energies are sensitive and reliable experimental measures of the contributions of the gas-phase radical-mediated and surface-mediated pathways, suggesting the outline of a general mechanistic framework of the boron-catalyzed ODH.

Deep Potential Molecular Dynamics Study of Propane Oxidative Dehydrogenation.

Oxidative dehydrogenation (ODH) of light alkanes is a key process in the oxidative conversion of alkanes to alkenes, oxygenated hydrocarbons, and COx (x = 1,2). Understanding the underlying mechanisms extensively is crucial to keep the ODH under control for target products, e.g., alkenes rather than COx, with minimal energy consumption, e.g., during the alkene production or maximal energy release, e.g., during combustion. In this work, deep potential (DP), a neural network atomic potential developed in recent years, was employed to conduct large-scale accurate reactive dynamic simulations. The model was trained on a sufficient data set obtained at the density functional theory level. The intricate reaction network was elucidated and organized in the form of a hierarchical network to demonstrate the key features of the ODH mechanisms, including the activation of propane and oxygen, the influence of propyl reaction pathways on the propene selectivity, and the role of rapid H2O2 decomposition for sustainable and efficient ODH reactions. The results indicate the more complex reaction mechanism of propane ODH than that of ethane ODH and are expected to provide insights in the ODH catalyst optimization. In addition, this work represents the first application of deep potential in the ODH mechanistic study and demonstrates the ample advantages of DP in the study of mechanism and dynamics of complex systems.

Investigation of AFeO3 (A=Ba, Sr) Perovskites for the Oxidative Dehydrogenation of Light Alkanes under Chemical Looping Conditions.

Oxidative dehydrogenation (ODH) of light alkanes to produce C2-C3 olefins is a promising alternative to conventional steam cracking. Perovskite oxides are emerging as efficient catalysts for this process due to their unique properties such as high oxygen storage capacity (OSC), reversible redox behavior, and tunability. Here, we explore AFeO3 (A=Ba, Sr) bulk perovskites for the ODH of ethane and propane under chemical looping conditions (CL-ODH). The higher OSC and oxygen mobility of SrFeO3 perovskite contributed to its higher activity but lower olefin selectivity than its Ba counterpart. However, SrFeO3 perovskite is superior in terms of cyclic stability over multiple redox cycles. Transformations of the perovskite to reduced phases including brownmillerite A2Fe2O5 were identified by X-ray diffraction (XRD) as a cause of performance degradation, which was fully reversible upon air regeneration. A pre-desorption step was utilized to selectively tune the amount of lattice oxygen as a function of temperature and dwell time to enhance olefin selectivity while suppressing CO2 formation from the deep oxidation of propane. Overall, SrFeO3 exhibits promising potential for the CL-ODH of light alkanes, and optimization through surface and structural modifications may further engineer well-regulated lattice oxygen for maximizing olefin yield.

Nano Carbon as Catalyst for the Dehydrogenation of Alkanes to Produce Olefin

The escalating need for energy around the globe increases the production rate of several chemicals. This report elucidates the production process of olefins through the Dehydrogenation of light alkanes using nanocarbon as a catalytic material. There are several catalysts used to produce olefins. However, there are many problems associated with these catalysts, such as the encapsulation of catalytic particles with coke which retard the product formation. Therefore, nanocarbon is considered the substitute in place of Pt, Pd, Ga, etc. It is also observed that 37% of the production rate has been increased by using nanoparticles as a catalyst. Moreover, using carbon nanoparticles as a catalyst will reduce global warming as carbon is the primary source of the greenhouse effect, increasing the development of a sustainable environment. The activity of the catalyst is highly dependent on the surface-active sites of the substance. Because the greater the number of active sites, the more significant the reactive sites will be, and the rate of reaction escalates.

Synthesis gold and jade type core shell structure Pt@Sn in deboronated MWW zeolite and its good performance for light alkane dehydrogenation

The Pt@Sn core–shell structure was generated in MWW zeolite catalysts prepared by atom-planting incorporated Sn and deposition–precipitation (DP) loaded Pt for direct dehydrogenation of ethane or propane and CO2 oxidative dehydrogenation. The introduced Sn species can immobilize cubic structure Pt nanoparticle with well dispersed particles by DP method through the charge’s attraction. The stronger charge transfer between Pt-Sn improves the catalyst activity for the C-H band breaking of alkane. The zeolite skeleton incoporated Sn formed Sn-O-Si bond and can be broken to be extracted from the zeolite structure as SnO2 under the dehydrogenation process. The extracted SnO2 in the ‘half-cup’ external supercage encapsulates the Pt nanoparticle and forms the gold and jade type core–shell structure, which reduces the Pt agglomeration and modifies the Pt nanoparticle crystal edge and corner active sites and reduced the C-C band cleavage to side products and coke formation, thus improving the dehydrogenation selectivity and stability.

Speciation and interconversion of atomically dispersed extra-framework Ga in ZSM-5 zeolite

Ga/ZSM-5 has been studied for a long time for its efficiency in catalytic dehydrogenation and conversion of light alkanes. Atomically dispersed extra-framework Ga species, such as [Ga]+(I), [GaH2]+(III), [GaO]+(III), [GaHOH]+(III), [Ga(OH)2]+(III) and [GaH]2+(III), etc. were proposed as reaction centers for such processes. To rationale the observed catalytic performances of Ga/ZSM-5, we investigated the electronic structures of these Ga species and pathways for their interconversion in zeolite channels by first-principles based calculations. Results from thermodynamics calculations at conditions relevant to experiments show that [Ga]+(I) is plausible at high temperature and low PH2O, and [Ga(OH)2]+(III) is plausible at low temperature and high PH2O. On pathways for interconversion of proposed Ga species, the calculated energy and free energy barriers for H2 dissociation and H2O formation are among the highest and correlate with involvement of Ga centers and their coordination with H and O-containing ligands. The coordination of framework O to Ga center are rather flexible, making dynamic formation of undercoordinated Ga species feasible at operation conditions and these species may attend subsequent chemical processes. We expect the findings would help to understand the formation and evolution of atomically dispersed reaction centers in zeolite channels under operation conditions.

Propane Oxidative Dehydrogenation on Nanosized Boron Carbide: Effect of Boron Content and Its Oxidation Implicated by DFT Calculations

Metal-free boron-containing materials are growing to be promising choices in oxidative dehydrogenation (ODH) of light alkanes to alkenes, while it remains unclear how the boron content and the second element that constitutes the scaffold to accommodate B in the materials may influence their catalytic activity. Herein, by means of the density functional theory study of nanosized boron carbide, we studied the mechanisms of ODH of propane (ODHP) catalyzed by three types of boron carbides, B13C2, B4C, and h-BC, which differ from each other in their B contents and their chemical topologies. The influence of hydroxyl coverage on the surface was also evaluated to address the structure–catalytic activity relationship in the ODHP reaction. The calculations show that (1) the B element content and the hydroxyl groups could regulate the electronic structure and significantly increase the highest occupied molecular orbital (HOMO) energy to promote chemical reactivity. (2) Boron carbide with higher coverage of hydroxyl groups on the surface (B13C2-H and B4C-H) exhibits higher activity for catalyzing ODHP reaction owing to the enhanced nucleophilicity, which is further confirmed by the noncovalent interaction (NCI) analysis. (3) The reactivity of the catalyst is positively correlated with the B content, and the ODHP catalyzed by B13C2 is kinetically more favorable than that by B4C and h-BC. This study is expected to enrich our understanding of the structure–activity relationship of boron-based catalysts in the ODH system and benefit the optimization of the catalytic systems.

Improved Performance of Commercial Catalyst 13 wt % Cr-γ-Al2O3 for Direct Ethane Dehydrogenation to Ethylene

For the improvement of commercial catalyst 13 wt % Cr-γ-Al2O3 for the dehydrogenation of light alkanes to olefins, 13 wt % Cr-x wt % Ce-γ-Al2O3 catalysts with x equaling 0, 2.5, 5, 7.5, and 10, named as 0Ce, 2.5Ce, 5Ce, 7.5Ce, and 10Ce, are prepared by the incipient wetness impregnation method, characterized by X-ray diffraction, transmission electron microscopy, Raman, UV–vis, X-ray photoelectron spectroscopies, and temperature-programmed reduction and evaluated for ethane dehydrogenation to ethylene. Their performance increases with Ce addition to 5 wt % and then decreases and attenuates with time. 5Ce demonstrates the highest dehydrogenation activity and better regeneration ability than 0Ce. It is found that the as-prepared 5Ce contains more active amorphous Cr6+ species and less crystalline Cr3+ species (α-Cr2O3) than 0Ce, other than the Ce species of CeO2. The reasons for the better dehydrogenation and regeneration performance of 5Ce are that the CeO2 particles in 5Ce physically separate the Cr species, promoting the formation of Cr6+ species, preventing their aggregation and migration to form less active α-Cr2O3 and inactive α-(Cr, Al)2O3, and preserving more active Cr6+ species in the as-prepared and regenerated catalysts.

Catalytic cracking of supercritical n-dodecane over macro-meso-HZSM-5 coatings by vertical secondary growth

Hierarchical HZSM-5 zeolite coatings are extensively investigated for catalytic cracking of supercritical fuels to benefit the thermal management of hypersonic aircraft. However, there is still a challenge for preparing zeolite coatings combining the high diffusion property, strong mechanical strength and a large amount of Brønsted acid sites. Herein, the macro-meso-HZSM-5 coatings with meso-HZSM-5 grains vertically welding on the compact and randomly oriented zeolite basal layer were fabricated on the inner wall of the stainless-steel tubes by ammonia-assisted vertical secondary growth, using amphiphilic organosilane as a meso-porogen. The structure benefited the breaking of the trade-off between diffusion and acidity of the coating. And by adjusting the dosage of inorganic ammonium salt and the crystallization time, the synthesis mechanism of the coatings was speculated. Inorganic ammonium salt facilitated the formation of macropores and the vertical growth of crystals with (00 h)&(10 h) orientation (pseudo-c-orientation). The chemical composition of the seed layer was adjusted using Si-MFI, Al-MFI or Ga-MFI as seeds, and the mechanical strength was enhanced by the intergrowth of zeolite phase in the seed layer. The macro-meso-HZSM-5 coating synthesized with Al-MFI as the seed (MZC-Al-2N), exhibited an excellent catalytic conversion and stability for cracking of supercritical n-dodecane (550 °C and 4 MPa), with the initial reaction rate and the deactivation rate being three times and 52 % of the conventional HZSM-5 coating, respectively, due to the combination of the improved diffusion property as well as the suitable acidity. The coating synthesized using Ga-MFI seed showed a lower activity, but a higher heat sink compared with MZC-Al-2N, probably due to the dehydrogenation of light alkanes over the synergistic effect between the Brønsted acid sites and the extra-framework Ga species.

Supported boron-based catalysts for oxidative dehydrogenation of light alkanes to olefins

Boron-based catalysts have shown great fundamental and practical value in oxidative dehydrogenation (ODH) of light alkanes to olefins.

Multiscale modeling reveals aluminum nitride as an efficient propane dehydrogenation catalyst

First-principles-based microkinetic modeling simulations suggest AlN for light alkane dehydrogenation to olefins.

Suppressing Deep Oxidation by Detached Nano-sized Boron Oxide in Oxidative Dehydrogenation of Propane Revealed by the Density Functional Theory Study

The remarkable reactivity and selectivity of boron-based catalysts in the oxidative dehydrogenation (ODH) of light alkanes offer a sustainable path for the efficient conversion of light alkanes to olefins, while the origin of their unique ability to suppress deep oxidation remains to be studied. Concerning the leaking of boron oxide under ODH conditions, here, the ability of detached nano-sized boron oxide to eliminate propoxyl radicals, which is crucial to the high selectivity of olefins, was evaluated by means of density functional theory calculations. The results show that the barrier to the reaction is about 24 kcal/mol, suggesting that the detached nano-sized boron oxide can capture the propoxyl radicals under ODHP conditions to suppress the deep oxidation. The chemical environment may impose moderate influence by modulating their oxophilicity, and the boron sites that bear fewer hydroxyl groups show stronger affinity for the propoxyl radicals. This suggests that the inner tri-coordinated boron sites are more reactive than the edge boron sites in the elimination of alkoxyl radicals in the ODH of light alkanes, which is opposite to their ability to activate atmospheric dioxygen. This study enriches our understanding on the specific nature of boron-containing catalysts in suppressing the deep oxidation of light alkanes in their ODH.

Correlation between the Properties of Surface Lattice Oxygen on NiO and Its Reactivity and Selectivity towards the Oxidative Dehydrogenation of Propane.

Modified NiO catalysts with controllable vacancies and dopants are promising for alkene production from oxidative dehydrogenation (ODH) of light alkanes, and a molecular understanding of the modification on elementary reaction steps would facilitate the design of highly efficient catalysts and catalytic processes. In this study, density functional theory (DFT) calculations was used to map out the complete reaction pathways of propane ODH on the NiO (100) surfaces with different modifiers. The results demonstrated that the presence of vacancies (O and Ni) and dopants (Li and Al) alters the electrophilicity of surface oxygen species, which in turn affects the reactivity towards C-H bond activation and the overall catalytic activity and selectivity. The strongly electrophilic O favors a radical mechanism for the first C-H activation on O followed by the second C-H activation on O-O site, whereas weak electrophilic O favors concerted C-H bond breaking over Ni-O site. The C-H bond activation proceeds through a late transition state, characterized by the almost completion of the O-H bond formation. Consequently, the adsorption energy of H adatom on O rather than p-band center or Bader charge of O has been identified to be an accurate descriptor to predict the activation barrier for C-H breaking (activity) as well as the difference between the activation barriers of propene and CH3 CCH3 (selectivity) of ODH.

Solid catalysts for the dehydrogenation of long-chain alkanes: lessons from the dehydrogenation of light alkanes and homogeneous molecular catalysis

Solid catalysts for the dehydrogenation of long-chain alkanes: lessons from the dehydrogenation of light alkanes and homogeneous molecular catalysis