Dehydrogenation Of N-butane Research Articles

Enhanced Stability and Selectivity in Pt@MFI Catalysts for n-Butane Dehydrogenation: The Crucial Role of Sn Promoter

The dehydrogenation of n-butane to butenes is a crucial process for producing valuable petrochemical intermediates. This study explores the role of oxyphilic metal promoters (Sn, Zn, and Ga) in enhancing the performance and stability of Pt@MFI catalysts for n-butane dehydrogenation. The presence of Sn in the catalyst inhibits the agglomeration of Pt clusters, maintaining their subnanometric particle size. PtSn@MFI exhibits superior stability and selectivity for butenes while suppressing cracking reactions, with selectivity for C1–C3 products as low as 2.1% at 550 °C compared to over 30.5% for Pt@MFI. Using a combination of high-angle annular dark-field scanning transmission electron microscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, and Raman spectroscopy, we examined the structural and electronic properties of the catalysts. Our findings reveal that Zn tends to consume hydroxyl groups and substitute framework sites, and Ga induces more defective sites in the zeolite structure. In contrast, the interaction between SnOx and the zeolite framework does not depend on reactions with hydroxyl groups. The incorporation of Sn significantly prevents Pt particle agglomeration, maintaining smaller Pt particle sizes and reducing coke formation compared to Zn and Ga promoters. Theoretical calculations showed that Sn increases the positive charge on Pt clusters, enhancing their interaction with the zeolite framework and reducing sintering, albeit with a slight increase in the energy barrier for C-H activation. These results underscore the dual benefits of Sn as a promoter, offering enhanced structural stability and reduced coke formation, thus paving the way for the rational design of more effective and durable catalysts for alkane dehydrogenation and other high-value chemical processes.

Dehydrogenation of n-butane to butadiene-1,3: 3. Kinetics of regeneration of coked aluminochromium catalyst

The kinetics of coke burning off at temperatures of 525–650 °C on a K-CrOx/γ-Al2O3 catalyst for single-stage dehydrogenation of n-butane to butadiene-1,3, similar to the industrial one, was studied. It was shown that under the studied conditions, the coke burning off reaction is described by a first-order kinetic equation with respect to oxygen and coke with an observed activation energy of ~93 kJ/mol. The adequacy of the kinetic model was confirmed by the coincidence of the calculated and experimental results.

Investigation of n-Butane Conversion on Pd, Rh, Ru Catalysts Supported by Al2O3 and SiO2

This study explored the dehydrogenation of n-butane using Pd, Rh, and Ru catalysts on aluminum and silicon oxide supports. Aluminum oxide (Al2O3) showed superior conversion of n-butane, especially with 1% Pd/γAl2O3, yielding 31% target alkenes. This catalyst offers potential for scaling up n-butane dehydrogenation technology.

Dehydrogenation of n-butane to 1,3-butadiene on chromia-alumina catalyst: 1. Kinetics of dehydrogenation and coke formation

The kinetics of dehydrogenation of n-butane to butadiene was studied on K-CrOx /γ-Al2O3 catalyst particles of 56–94 μm size by varying the temperature T = 550÷625 °C, the time of catalytic step TOS = 5÷30 min, and the space velocity GHSV = 4400÷35200 h–1. The catalyst was similar to the commercial one. Prior to the studies, the catalyst granules were stabilized during the reduction-dehydrogenation-regeneration cycle at 593 °C, then the catalyst particles milled to a size of 56–94 μm were stabilized during the dehydrogenation-regeneration cycle at 650 °C. The highest butadiene selectivity of ~25 mol.% was obtained at n-butane conversion of 26–30 % (GHSV = 35200 h–1) at T = 600 °C and TOS = 5 min, and the highest butadiene yield of ~10 mol.% was obtained when the conversion was increased to ~50 % (GHSV = 8800 h–1) under the same conditions. Increasing T to 625 °C, TOS to 30 min and decreasing GHSV to ~4400 h–1 resulted in an increase in by-product selectivity to ~50 mol.%. It was found that the observed activation energy of product formation rates decreases in the series: by-products > butylene > butadiene. A kinetic model is proposed that takes into account the formation of butadiene via butylene, the formation of by-products such as ethane/ethylene and methane/propylene in the butylene hydrocracking reactions, and the secondary conversion reactions of by-products. Inhibition of dehydrogenation reactions by components of the reaction mixture, coke formation and its effect on catalyst activity are also considered in the model. The adequacy of the kinetic model is confirmed by good agreement of the calculated results with the experimental data.

Intelligent Chemometric Modelling of Al2O3 Supported Mixed Metal Oxide Catalysts for Oxidative Dehydrogenation of n-Butane Using Simple Features

The development of efficient and selective catalysts for the oxidative dehydrogenation (ODH) of n-butane to produce butenes and butadiene with high performance has been subject of intense research in recent...

Unprecedented selectivity behavior in the direct dehydrogenation of n-butane to n-butenes with similar active Pt nanoparticle size: unveiling structural and electronic characteristics of supported monometallic catalysts.

In this work, supported Pt monometallic catalysts were prepared using oxide and carbon supports by conventional impregnation methods. Similar Pt metallic nanoparticle sizes (mean sizes about 1.8-2 nm) have been obtained using different Pt precursor loadings (0.3 to 5 wt%). For comparison, catalysts with larger nanoparticle sizes were prepared using the liquid phase reduction method. Characterization results indicate different electronic and structural characteristics for the Pt nanoparticles, comparing nanoparticles with similar and different sizes, implying that both the Pt loading and the preparation method affect the formation of different metallic phases. We used the direct dehydrogenation of n-butane to n-butenes reaction as a test reaction to study the catalytic behavior of the Pt nanoparticles obtained at different Pt atomic concentrations. Surprisingly, Pt catalysts with the lowest metallic loading show the highest selectivities to olefins. Besides, Pt catalysts supported on carbon materials showed higher selectivity to butenes than those supported on oxide materials, this was attributed to a higher electron density in the Pt active sites. Likewise, at low Pt loadings, the CNP-supported Pt nanoparticles could be confined at the defect in the nanotube structure as crystalline agglomerates of atoms with few layers or monolayers with very few surface adatom or stepped adatom nanostructures or simply as a group of atoms, thus creating active Pt sites that favor the dehydrogenation reaction over secondary reactions.

Structural reconstruction of iron oxide induces stable catalytic performance in the oxidative dehydrogenation of n-butane to 1,3-butadiene

The CO2-assisted oxidative dehydrogenation of n-butane to 1,3-C4H6 offers a perspective process for producing valuable chemicals while simultaneously utilizing CO2. In this work, iron-based ZnFe2Ox and Fe2O3 catalysts with high 1,3-C4H6 selectivity were prepared and their corresponding structure–activity relationships were investigated in detail. On basis of the in situ spectroscopic characterization, hydrogen-assisted CO2 activation pathway was captured. Kinetic studies show that Fe2O3 catalyst displays a higher reaction order depending on CO2 concentration than that of ZnFe2Ox catalyst. Fe2O3 is evidenced to serve as an effective mediator for oxygen exchange between CO2 and n-butane based on temperature-programmed experiments and deactivation kinetics analysis. Rapid deactivation is observed over ZnFe2Ox due to its strong CO2 adsorption ability, which triggers the reforming reaction accompanied by severe coke deposition. Interestingly, self-healing phenomena for catalytic performance are found on Fe2O3 catalyst after several test cycles. The reaction/regeneration cycles are proved to drive the surface reconstruction which greatly enhance its resistance to over reduction and coking. This study provides a fundamental insight into Fe-based catalysts in the CO2-assisted oxidative dehydrogenation reactions.

Unravelling the pathway for the dehydrogenation of n-butane to 1,3-butadiene using thermodynamics and DFT studies

Dehydrogenation of n-butane is one of the main on-purpose method for producing 1,3- butadiene. Thermodynamics studies revealed that reasonable yields of 1,3-butadiene can only be achieved at higher temperatures, while the formation of butene isomers are favored at lower temperatures, confirming that 1,3-butadiene is a secondary product. In the present study, NiO/Al2O3 and Ni-BiOx/Al2O3 catalysts, having 10 and 20 wt% Ni and 10 and 30 wt% Bi loading were synthesized. Experimental testing using fixed bed reactor validated that the addition of BiOx improved 1,3-butadiene selectivity from 20 % to 43 % with similar n-butane conversion, at 500 °C. Also, density functional theory (DFT) studies for n-butane adsorption on Ni (111) and Bi-Ni (111) surfaces confirmed that, the addition of Bi promoters to the Ni surface modifies the n-butane adsorption strength resulting in lower adsorption energies of −0.02 eV weaker than −0.36 eV on Ni (111) surfaces. The reaction pathways investigation for the successive dehydrogenation route of n-butane on the most stable structures of Ni (111) and Bi-Ni (111) surfaces revealed that 1-butene pathway via the formation of 1-butyl, is most favorable relative to the 2-butene pathway via 2-butyl formation. This is due to the higher activation barrier for the formation of 2-butene intermediate on both Ni (111) and Bi-Ni (111) surfaces.

Structure-dependence and metal-dependence on atomically dispersed Ir catalysts for efficient n-butane dehydrogenation

Single-site pincer-ligated iridium complexes exhibit the ability for C-H activation in homogeneous catalysis. However, instability and difficulty in catalyst recycling are inherent disadvantages of the homogeneous catalyst, limiting its development. Here, we report an atomically dispersed Ir catalyst as the bridge between homogeneous and heterogeneous catalysis, which displays an outstanding catalytic performance for n-butane dehydrogenation, with a remarkable n-butane reaction rate (8.8 mol·gIr−1·h−1) and high butene selectivity (95.6%) at low temperature (450 °C). Significantly, we correlate the BDH activity with the Ir species from nanoscale to sub-nanoscale, to reveal the nature of structure-dependence of catalyst. Moreover, we compare Ir single atoms with Pt single atoms and Pd single atoms for in-depth understanding the nature of metal-dependence at the atomic level. From experimental and theoretical calculations results, the isolated Ir site is suitable for both reactant adsorption/activation and product desorption. Its remarkable dehydrogenation capacity and moderate adsorption behavior are the key to the outstanding catalytic activity and selectivity.

Influence of Zn and Fe promoters on Ni-Bi/γ-Al2O3 catalyst for oxidative dehydrogenation of n-butane to butadiene

This study investigated the effects of Zn and Fe metal oxide species as promoters on NiO-Bi2O3/γ-Al2O3 in the oxidative dehydrogenation (ODH) of n-butane to produce butadiene. Ni-Bi-O, Ni-Zn-Bi-O, Ni-Fe-Bi-O, and Ni-Zn-Fe-Bi-O catalysts supported on γ-Al2O3 were synthesized, characterized, and evaluated in a packed bed flow reactor at different temperatures and O2/n-butane molar ratios. Substituting 50 wt.% of Ni with one or both promoters were found to enhance both the butadiene selectivity. Among the synthesized catalysts, Ni-Zn-Fe-Bi-O/γ-Al2O3 (10 wt.% Ni-5 wt.% Zn-5 wt.% Fe-30 wt.% Bi) showed the highest butadiene selectivity of 49.0% with 18.6% n-butane conversion at 450 °C and a molar feed ratio of O2/n-butane = 2.0. This enhanced performance was attributed to the synergetic effects of Ni, which simultaneously improved the first-step dehydrogenation selectivity via a promotion with Zn and the second-step dehydrogenation selectivity by the incorporation of Fe. Moreover, Zn allowed the surface reduction to occur at lower temperatures, while Fe balanced the densities of strong basic sites with weak and moderate acid sites (0.183 mmol CO2/g-cat and 0.188 mmol NH3/g-cat, respectively). The aforementioned results were confirmed with CO2/NH3 temperature-programmed desorption and H2 temperature-programmed reduction experiments. Under this reaction condition, the catalyst maintains good stability over 15 h of time-on-stream.

Design of PtM (M = Ru, Au, or Sn) bimetallic particles supported on TS-1 for the direct dehydrogenation of n-butane

In this study, a theoretical model based on the use of PtM (M = Ru, Au, or Sn) bimetallic clusters supported on titanium silicalite (TS-1) was built and used to investigate the dehydrogenation of n-butane. The catalysts that were suitable for the dehydrogenation process were screened using the cluster model, and a relationship between the d-band center and the energy barrier of the first dehydrogenation step was established. To verify the theoretical results, a series of PtM bimetallic particles supported on TS-1 were prepared and tested in the n-butane dehydrogenation reaction. The order of increasing turnover frequencies and the apparent activation energies of the PtM bimetallic catalysts were essentially consistent with the theoretical results. This study can be used to guide the design of catalysts toward the dehydrogenation of n-butane.

Dehydrogenation of Propane and n-Butane Catalyzed by Isolated PtZn4 Sites Supported on Self-Pillared Zeolite Pentasil Nanosheets

Propene and 1,3-butadiene are important building-block chemicals that can be produced by dehydrogenation of propane and butane on Pt catalysts. A challenge is to develop highly active and selective catalysts that are resistant to deactivation by Pt sintering and coke formation. We have recently shown (Qi , J. Am. Chem. Soc. 2021, 143, 21364−21378) that these objectives can be met for propane dehydrogenation (PDH) using atomically dispersed Pt anchored to neighboring ≡SiOZn-OH groups bonded to the framework of dealuminated zeolite BEA. In the present study, we demonstrate that significantly superior performance can be achieved using self-pillared pentasil (SPP) zeolite nanosheets as supports. Following catalyst reduction in H2, atomic resolution, scanning transmission electron microscopy (STEM), and X-ray absorption spectroscopy (XAS) indicate that Pt is stabilized in structures well approximated as (≡Si-O-Zn)4-5Pt. These species are highly active, selective, and stable for PDH to give propene and for n-butane dehydrogenation (BDH) to give 1,3-butadiene. No catalyst deactivation was observed after 12 days of time on stream, and the selectivity remained at nearly 100% for PDH conducted at 823 K and a weight hourly space velocity (WHSV) of 1350 h–1. The apparent rate coefficient for PDH on this catalyst is significantly higher than that reported previously for Pt-containing catalysts. For BDH at 823 K and a WHSV of 3560 h–1, the selectivity to butene isomers and 1,3-butadiene is 98.9%, and the selectivity to 1,3-butadiene is 45%. We propose that the high catalyst stability observed during PDH and BDH is a consequence of a large fraction of the Pt-containing centers being located on the external surface of the zeolite nanosheets, where nascent coke precursors can desorb before condensing to form coke.

Alkali metal halide-coated perovskite redox catalysts for anaerobic oxidative dehydrogenation of n-butane.

Oxidative dehydrogenation (ODH) of n-butane has the potential to efficiently produce butadiene without equilibrium limitation or coke formation. Despite extensive research efforts, single-pass butadiene yields are limited to <23% in conventional catalytic ODH with gaseous O2. This article reports molten LiBr as an effective promoter to modify a redox-active perovskite oxide, i.e., La0.8Sr0.2FeO3 (LSF), for chemical looping–oxidative dehydrogenation of n-butane (CL-ODHB). Under the working state, the redox catalyst is composed of a molten LiBr layer covering the solid LSF substrate. Characterizations and ab initio molecular dynamics (AIMD) simulations indicate that peroxide species formed on LSF react with molten LiBr to form active atomic Br, which act as reaction intermediates for C─H bond activation. Meanwhile, molten LiBr layer inhibits unselective CO2 formation, leading to 42.5% butadiene yield. The redox catalyst design strategy can be extended to CL-ODH of other light alkanes such as iso-butane conversion to iso-butylene, providing a generalized approach for olefin production.

Relating the Synthesis Method of VOX/CeO2/SiO2 Catalysts to Red-Ox Properties, Acid Sites, and Catalytic Activity for the Oxidative Dehydrogenation of Propane and n-Butane

Relating the Synthesis Method of VOX/CeO2/SiO2 Catalysts to Red-Ox Properties, Acid Sites, and Catalytic Activity for the Oxidative Dehydrogenation of Propane and n-Butane

Electronic interaction between Cr3+ ions in chromia-alumina catalysts for light alkane dehydrogenation

In this work chromia-alumina catalysts have been studied by the electron paramagnetic resonance (EPR) spectroscopy in the temperature range -120–200 °C. It was observed, that the activity of the catalysts in the dehydrogenation of n-butane and i-butane correlates with the amount of strongly interacting Cr3+ ions of the amorphous chromia phase. A disproportionate increase in the antiferromagnetic coupling energy ΔE between Cr3+ ions was shown in the concentration range 4.7–9.8%wt.Cr (from 210 to 420 cm−1) and 9.8–13.3%wt.Cr (from 420 to 450 cm−1). It was established, that an increase in the exchange interaction between Cr3+ ions is more favourable for the dehydrogenation of i-butane as compared to n-butane.

CO2 oxidative dehydrogenation of n-butane to butadiene over CrOx supported on CeZr solid solution

1,3-Butadiene (BD) is a key raw material for the synthesis of rubber, but its efficient synthesis is a challenge. Direct dehydrogenation of n-butane in CO2 (CO2ODHB) represents an ideal way to produce BD and use the waste CO2 source. In the present work, several catalysts of CrOx supported on CeZr solid solutions were developed and applied in catalyzing the CO2ODHB to BD. Among these, a 10%CrOx/Ce0.5Zr0.5O2 could achieve the reaction with 25% of n-butane conversion and 70% of BD selectivity at 823 K. The prepared catalysts were characterized using the techniques of XRD, UV–vis-DR, XPS, Raman, N2 adsorption/desorption, FT-IR, TEM, H2-TPR, NH3-TPD, and CO2-TPD, etc. The results indicated that compared with other catalysts, the 10% CrOx/Ce0.5Zr0.5O2 catalyst possessed the highest Cr6+ species concentration and balanced acidic-basic sites, contributing to the outstanding performance in the reaction. These findings provide a strategy to build a catalyst with the stable valence of Cr6+ species, and hopefully, offer an important reference to establish other CeZr solid solution catalysts with regulable acidic-basic and textural properties.

Mechanism and Kinetics of n-Butane Dehydrogenation to 1,3-Butadiene Catalyzed by Isolated Pt Sites Grafted onto ≡SiOZn–OH Nests in Dealuminated Zeolite Beta

An interest in the on-purpose production of 1,3-butadiene (1,3-BD) has grown, as a consequence of the decline in naphtha cracking for the production of ethene and propene, products that can now be produced economically by thermal dehydrogenation of ethane and propane contained in natural gas. In this study, the mechanism and kinetics of n-butane dehydrogenation to 1,3-BD are explored over atomically distributed Pt sites grafted onto dealuminated zeolite BEA (DeAlBEA) in the form of (≡Si–O–Zn)4–6Pt complexes. Reaction of n-butane dehydrogenation carried out at 823 K with 2.53 kPa n-butane/He and a weight-hourly space velocity (WHSV) of 14.5 h–1 produced 1,3-BD with a turnover frequency of 0.45 mol 1,3-BD (mol Pt)−1 s–1. Space-time studies and identification of the reaction intermediates suggest that n-butane first undergoes dehydrogenation primarily to 1-butene, which then rapidly isomerizes to produce an equilibrated mixture of 1-butene and 2-butene. 1-Butene then undergoes secondary dehydrogenation to produce 1,3-BD. We report, here, a detailed study of the kinetics of n-butane dehydrogenation to butenes and 1-butene dehydrogenation to 1,3-BD over isolated Pt sites. Both reactions exhibit a Langmuir–Hinshelwood dependence on n-butane and 1-butene partial pressures, respectively. Comparison of effective forward rate constants of n-butane dehydrogenation to butenes (k1f) and butene dehydrogenation to 1,3-BD (k2f) shows that the isolated Pt sites grafted onto DeAlBEA exhibit a very high activity for sequential dehydrogenation of n-butane to 1,3-BD relative to other Pt-based catalysts previously reported.

Influence of Zn and Fe Promoters on Ni-Bi/Γ-Al2o3 Catalyst for Oxidative Dehydrogenation of N-Butane to Butadiene

Influence of Zn and Fe Promoters on Ni-Bi/Γ-Al2o3 Catalyst for Oxidative Dehydrogenation of N-Butane to Butadiene

N-butane dehydrogenation on PtSnIn and PtSnGa trimetallic catalysts supported on structured materials prepared by washcoating

The aim of this work was to evaluate PtSnIn and PtSnGa catalysts supported on structured materials, composed of a thin layer of γ- Al2O3 deposited on compact spheres of α-Al2O3, in the non-oxidative dehydrogenation of n-butane to n-butene.The trimetallic catalysts supported on γ-A-wc showed better catalytic behaviour in terms of activity, selectivity to all butenes, and a low deactivation along the reaction time, compared to the monometallic catalyst. PtSnIn/γ-A-wc and PtSnGa/γ-A-wc catalysts with the highest In or Ga loading showed better performance than those with a lower content of promoters. The results of the pulse experiments clearly indicated the important effect of the promoters added to Pt, both by sharply increasing the selectivity to butenes and by decreasing the carbon formation during the first steps of the reaction.The characterization of the metallic phase showed that the addition of promoters such as Sn and In or Sn and Ga produce geometric effects, dilution and blocking effects on Pt atoms. XPS results confirmed the presence of surface metallic Pt(0), In(0) or Ga(III), Sn(II)/Sn(IV) species in a high concentration and minor amounts of surface Sn(0), probably forming alloy particles with Pt and the third metal.The PtSnIn (0.5)/γ-A-wc catalyst which showed the best catalytic behaviour in flow experiments was submitted to successive reaction-regeneration cycles in order to determine its catalytic stability. There was a small yield decrease in the first two cycles, but from the third cycle onwards the yields to butenes proved to be more stable. These results were very promising mainly if compared to those obtained for the monometallic Pt catalyst. Characterization results of the catalyst after cycles showed that the metallic phase did not undergo significant modifications.

Regulating coordination number in atomically dispersed Pt species on defect-rich graphene for n-butane dehydrogenation reaction

Metal nanoparticle (NP), cluster and isolated metal atom (or single atom, SA) exhibit different catalytic performance in heterogeneous catalysis originating from their distinct nanostructures. To maximize atom efficiency and boost activity for catalysis, the construction of structure–performance relationship provides an effective way at the atomic level. Here, we successfully fabricate fully exposed Pt3 clusters on the defective nanodiamond@graphene (ND@G) by the assistance of atomically dispersed Sn promoters, and correlated the n-butane direct dehydrogenation (DDH) activity with the average coordination number (CN) of Pt-Pt bond in Pt NP, Pt3 cluster and Pt SA for fundamentally understanding structure (especially the sub-nano structure) effects on n-butane DDH reaction at the atomic level. The as-prepared fully exposed Pt3 cluster catalyst shows higher conversion (35.4%) and remarkable alkene selectivity (99.0%) for n-butane direct DDH reaction at 450 °C, compared to typical Pt NP and Pt SA catalysts supported on ND@G. Density functional theory calculation (DFT) reveal that the fully exposed Pt3 clusters possess favorable dehydrogenation activation barrier of n-butane and reasonable desorption barrier of butene in the DDH reaction.