Non-oxidative Dehydrogenation Research Articles

First principles micro-kinetic model of catalytic non-oxidative dehydrogenation of ethane over close-packed metallic facets

Catalytic dehydrogenation of light alkanes may offer more efficient routes to selectively producing light olefins, which are some of the most important chemical building blocks in the industry, in terms of scale. We present a descriptor based micro-kinetic model of the trends in selectivity and activity of non-oxidative dehydrogenation of ethane over close-packed metal facets and through varied reaction conditions. Our model predicts and explains the experimentally observed promotion effect on turnover rate from co-feeding hydrogen as an effect of the shifting equilibria in steady state. At low conversion reaction conditions over Pt, the path to ethene goes through ethane dehydrogenation to ethyl, CH3CH2∗, then to ethene while the non-selective pathway to methane and deeply dehydrogenated species is predicted to go through dehydrogenation via CH3CH∗. This implies that the desorption step of ethene is not the limiting step for selectivity and that geometric effects that stabilize CH2CH2∗ compared to CH3CH∗ are desirable properties of a better catalyst. Removing reactive bridge and 3-fold sites facilitates this, which may be achievable by sufficient concentrations of tin in platinum. The included model code furthermore provides a base for easy tuning and for expanding the study to other thermodynamic conditions, other facets, alloys or the reaction network to longer hydrocarbons or to oxidative pathways.

Vanadium-containing dendritic mesoporous silica nanoparticles: Multifunctional catalysts for the oxidative and non-oxidative dehydrogenation of propane to propylene

Abstract Vanadium-containing dendritic mesoporous silica nanoparticles (V-DMSNs) were successfully synthesized by the co-assembly and anion-assisted method. The V-DMSNs were applied as catalysts for the oxidative dehydrogenation of propane and non-oxidative dehydrogenation of propane reactions. DMSNs support exhibits good hydrothermal stability according to the effect of ageing temperature and time on the structure. V-DMSNs with different vanadium contents preserve original structural characteristics of DMSNs support with three-dimensional and center-radial pore structure. The direct co-assembly process contributes to enhancing the interaction between the VO4 species and DMSNs support. A high concentration of highly dispersed and isolated VO4 species can be achieved on the present V-DMSNs systems. The V-DMSNs catalysts show better catalytic performance in the oxidative dehydrogenation of propane compared with corresponding V/DMSNs catalysts prepared by impregnation method. V-DMSNs catalysts also show the direct dehydrogenation ability and high stability. The appropriate concentrations of isolated and neighboring VOx species are favorably involved in propane activation and propylene formation. To further investigate the structural characteristics of catalysts dynamically responding to reactive conditions, the structures of active sites and deposited carbonaceous species were analyzed by in-situ Raman spectroscopy. This work gives a novel multifunctional catalyst that shows superior catalytic performance in the oxidative and non-oxidative dehydrogenation of propane reactions.

Influence of Metal Oxide Support Acid Sites on Cu-Catalyzed Nonoxidative Dehydrogenation of Ethanol to Acetaldehyde

Selective ethanol dehydrogenation to acetaldehyde is an important reaction because acetaldehyde is a useful commodity chemical and can serve as a building block to produce other high-value products...

In-silico screening of Pt-based bimetallic alloy catalysts using ab initio microkinetic modeling for non-oxidative dehydrogenation of ethanol to produce acetaldehyde

Abstract

The effect of phase composition and crystallite size on activity and selectivity of ZrO2 in non-oxidative propane dehydrogenation

A series of bare ZrO2 materials composed either of monoclinic or tetragonal phase with the size of crystallites varying between 3.7 and 43.4 nm were prepared by precipitation, hydrothermal or thermal calcination methods. The samples were characterized by XRD, BET, CO-TPR, NH3-TPD, electrical conductivity measurements and operando UV–vis spectroscopy. Density functional theory calculations provided molecular insights into the kind of active site and individual steps of propane dehydrogenation to propene and hydrogen. Regardless of the phase composition, two Zr cations located at an oxygen vacancy, i.e. coordinatively unsaturated Zr cations (Zrcus sites) having, nevertheless, different chemical environment in tetragonal and monoclinic ZrO2, were concluded to be responsible for homolytic breaking of CH bonds in propane. Monoclinic ZrO2 showed, however, higher rate of propene formation and higher propene selectivity than ZrO2 stabilized in the tetragonal phase. Both the activity and the selectivity to propene increased with a decrease in the size of crystallites. The effects of phase composition and crystallite size on the PDH performance were related to the ability of ZrO2 to release lattice oxygen upon reductive catalyst treatment and thus to create Zrcus sites. The knowledge derived can be used for further optimizing PDH performance of ZrO2-based catalysts and also extended to other non-reducible metal oxides.

High-performance catalytic perovskite hollow fiber membrane reactor for oxidative propane dehydrogenation

A novel hollow fiber catalytic membrane reactor for oxidative propane dehydrogenation (OPDH) was fabricated by integrating BaBi0.05Co0.8Nb0.15O3-δ (BBCN) perovskite hollow fiber membrane with silica-supported isolated Co2+ catalyst. Two other modes of propane dehydrogenation (PDH) were studied for comparison, non-oxidative dehydrogenation (NPDH), and conventional OPDH reaction via co-feed method. The results showed excellent performance of the catalytic membrane reactor, with C3H6 yield of ~ 50% and C3H6 selectivity of ~ 74% obtained at 650 °C over a 50-h long-term stability test, which are significantly higher than values obtained in the other two conventional reaction modes. Currently, this BBCN catalytic membrane reactor showed the highest C3H6 yield and best long-term stability as compared to other perovskite membrane reactors reported in literature. Propane feeding rate should be adjusted to match the oxygen permeation through the membrane thus maintaining the optimum ratio between propane to oxygen; excess oxygen permeation leads to combustion of propylene product and loss of propylene selectivity, while low oxygen permeation leads to low propane conversion. High temperature favors oxygen permeation through perovskite membranes but also increases the probability of cracking reaction. Therefore, if there is enough oxygen permeation through the membrane, it is preferred to operate this reaction at a lower temperature to increase the selectivity of propylene.

Nonoxidative Dehydrogenation of Methanol to Methyl Formate through Highly Stable and Reusable CuMgO-Based Catalysts.

Nonoxidative dehydrogenation of methanol to methyl formate over a CuMgO-based catalyst was investigated. Although the active site is metallic copper (Cu0), the best reaction conditions were obtained by tuning the ratio of Cu/Mg and doping the catalyst with 1 wt % of Pd to achieve a very specific activity for methyl formate synthesis. On the basis of the CO2 temperature-programmed desorption study, the basic strength of the catalyst plays a role in the efficient conversion of methanol to methyl formate via dehydrogenation. These CuMgO-based catalysts show excellent thermal stability during the reaction and the regeneration processes. Approx. 80% methanol conversion with constant selectivity to methyl formate was achieved even after 4 rounds of usage for a total reaction time exceeding 200 h, indicative of their potential for practical applications.

MOF-Derived Iron Catalysts for Nonoxidative Propane Dehydrogenation

The dehydrogenation of light alkanes, sourced from cracking of traditional petrochemical feedstocks and from emerging shale gas, represents an attractive route to alkenes (ethene, propene, and bute...

Understanding Alkane Dehydrogenation through Alcohol Dehydration on γ-Al2O3

Nonoxidative dehydrogenation of alkanes is an important chemical reaction, as it can be used for production of olefins, commonly used as building blocks for a range of plastics and chemicals. Several metal oxides, including γ-Al2O3, have exhibited dehydrogenation activity, showing promise as candidates for the upgrade of alkanes. In this work we use computational chemistry methods to investigate the mechanism of ethane, propane, n-butane, and i-butane dehydrogenation pathways on strong Lewis acid–base sites of γ-Al2O3. On the basis of our calculations, it was shown that a concerted dehydrogenation mechanism is energetically preferred with the formation of a carbenium-ion-like transition state. An alkane dehydrogenation model was developed on the basis of methodology previously applied in structure–activity relations (SAR) for alcohol dehydration on metal oxides. The carbenium ion stability (CIS), shown to be a descriptor in alcohol dehydration, was used as a quantitative descriptor in alkane dehydrogenati...

Absorptive Hydrogen Scavenging for Enhanced Aromatics Yield During Non‐oxidative Methane Dehydroaromatization on Mo/H‐ZSM‐5 Catalysts

Addition of Zr metal particles to MoCx /ZSM-5 in interpellet mixtures (2:1 weight ratio) resulted in maximum single-pass methane conversion of 27 % for dehydroaromatization at 973 K (in significant excess of the equilibrium prescribed circa 10 % conversion at these conditions) and a concurrent 1.4-5.6-fold increase in aromatic product yields due to circumvention of thermodynamic equilibrium limitations by absorptive H2 removal by Zr while retaining cumulative aromatic product selectivity. The absorptive function of the polyfunctional catalyst formulation can be regenerated by thermal treatment in He flow at 973 K, yielding above-equilibrium methane conversion in successive regeneration cycles. H2 uptake experiments demonstrate formation of bulk ZrH1.75 on hydrogen absorption by Zr at 973 K. Cooperation between absorption and catalytic centers distinct in location and function enables circumvention of persistent thermodynamic challenges in non-oxidative methane dehydrogenation.

Structure–Activity Relationships in Alkane Dehydrogenation on γ-Al2O3: Site-Dependent Reactions

A promising route to produce olefins, the building blocks for plastics and chemicals, is the nonoxidative dehydrogenation of alkanes on metal oxides, taking advantage of the Lewis acid–base surface functionalities of the oxides. However, how alkane dehydrogenation activity depends on the strength of surface acid–base site pairs is still elusive. In this work, we provide fundamental insights into the reaction mechanisms of propane dehydrogenation on different facets of γ-Al2O3 and develop structure–activity relationships, using density functional theory calculations and first-principles molecular dynamics simulations. We identified the binding energy of dissociated H2 as an activity descriptor for alkane dehydrogenation. Interestingly, a volcano relationship between catalytic activity and dissociative H2 binding energy was discovered for propane dehydrogenation, unraveling a site-dependent catalytic behavior on γ-Al2O3, with a concerted surface mechanism being energetically preferred to a sequential one on...

Oxidative and non-oxidative dehydrogenation of ethanol to acetaldehyde over different VOx/SBA-15 catalysts

In this present study, characteristics and catalytic properties of different VOx/SBA-15 catalysts for oxidative and non-oxidative dehydrogenation of ethanol to acetaldehyde were determined and well related. First, the SBA-15 supports were synthesized using the sol-gel (SG) and hydrothermal (HT) methods with Zr and La modification. Then, VOx species (2 wt% of V) were deposited on different SBA-15 supports. Among all catalysts, the V-Zr-La/SBA-15-HT showed the highest catalytic activity having 80% conversion of ethanol and acetaldehyde yield of ca. 38% at 400 °C in non-oxidative dehydrogenation, while 98% conversion of ethanol and acetaldehyde yield of ca. 40% were obtained for this catalyst at lower temperature (300 °C) in oxidative dehydrogenation. In fact, two of the most powerful techniques used to elucidate the nature of VOx species dispersed on Zr-La/SBA -15 supports were X-ray photoelectron spectroscopy (XPS), and CO2 temperature-programmed desorption. It is worth noting that isolated monomeric VOx species, particularly the V4+ species, as well as the amounts of weak basic sites essentially played important role in non-oxidative dehydrogenation and oxidative dehydrogenation of ethanol to acetaldehyde.

Atomically Precise Strategy to a PtZn Alloy Nanocluster Catalyst for the Deep Dehydrogenation of n-Butane to 1,3-Butadiene

The development of on-purpose 1,3-butadiene (BDE) technologies remains an active area in catalysis research due to the importance of BDE in industrial polymer production. Here, we report on a non-oxidative dehydrogenation catalyst for the production of BDE prepared by atomically precise installation of platinum sites on a Zn-modified SiO2 sup-port via Atomic Layer Deposition (ALD). In situ reduction x-ray adsorption spectroscopy (XAS) experiments, X-ray photoelectron spectroscopy (XPS), CO chemisorption, and high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) imaging of activated PtZn/SiO2 material, revealed the formation of a uniform, well-distributed sub-nano to nanometer PtZn (1.2 ± 0.3 nm) alloy as the active catalytic species.

Control of coordinatively unsaturated Zr sites in ZrO2 for efficient C\u2013H bond activation

Due to the complexity of heterogeneous catalysts, identification of active sites and the ways for their experimental design are not inherently straightforward but important for tailored catalyst preparation. The present study reveals the active sites for efficient C–H bond activation in C1–C4 alkanes over ZrO2 free of any metals or metal oxides usually catalysing this reaction. Quantum chemical calculations suggest that two Zr cations located at an oxygen vacancy are responsible for the homolytic C–H bond dissociation. This pathway differs from that reported for other metal oxides used for alkane activation, where metal cation and neighbouring lattice oxygen form the active site. The concentration of anion vacancies in ZrO2 can be controlled through adjusting the crystallite size. Accordingly designed ZrO2 shows industrially relevant activity and durability in non-oxidative propane dehydrogenation and performs superior to state-of-the-art catalysts possessing Pt, CrOx, GaOx or VOx species.

Zirconium Modification Promotes Catalytic Activity of a Single-Site Cobalt Heterogeneous Catalyst for Propane Dehydrogenation

The effect of Zr modification on the catalytic activity of Co/SiO2 was investigated for nonoxidative propane dehydrogenation. Isolated Zr on SiO2 surface sites were prepared by organometallic synthesis using Zr(OtBu)4 as a precursor. The resulting Zr/SiO2 support was functionalized with Co2+ ions via strong electrostatic adsorption. Spectroscopic (diffuse reflectance infrared Fourier transform spectroscopy, UV–vis, electron paramagnetic resonance) and microscopic characterization (transmission electron microscopy, scanning transition electron microscopy) results are consistent with single-site cobalt that preferentially associates with the mono-dispersed Zr at a variety of loadings and Co/Zr ratios. The oxidation state of Co in the as-prepared Co/SiO2 and Co–Zr/SiO2 was both +2 with tetrahedral and octahedral geometries, respectively. In situ X-ray absorption near edge structure and extended X-ray absorption fine structure results confirmed that the oxidation state of Co remained as +2 under reaction condition for both Co/SiO2 and Co–Zr/SiO2 samples and both catalysts have tetrahedral Co2+ as the active catalyst. Despite similar Co coordination environments, the catalytic activity and selectivity was significantly improved by the Zr modification of the silica support versus Co/SiO2. This was attributed to the change in oxygen donor ability and Co–O bond strength of the ≡SiO–Zr–O sites of Co–Zr/SiO2 compared with the ≡SiO– ligands in Co/SiO2. These results show that tuning of the support SiO2 oxygen donation ability by use of an anchoring site (e.g., ≡SiO–Zr–O–) can be used to alter both rate and selectivity of propane dehydrogenation with single-site heterogeneous catalysts. These results also show some preference for Co2+ active sites to associate with ≡SiO–Zr–O– sites over ≡SiO–.

Jinlong Gong

Angewandte Chemie International EditionVolume 57, Issue 36 p. 11504-11504 Author ProfileFree Access Jinlong Gong First published: 07 August 2018 https://doi.org/10.1002/anie.201807832AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Graphical Abstract “My favorite place on earth is my hometown—Lanzhou, Gansu Province. I chose chemistry as a career because chemistry changes the world and chemistry creates the world …” Find out more about Jinlong Gong in his Author Profile. Jinlong Gong The author presented on this page has published more than 10 articles in Angewandte Chemie in the last 10 years. His most recent contribution is featured on the inside back cover of this issue: “Low-Coordinated Edge Sites on Ultrathin Palladium Nanosheets Boost Carbon Dioxide Electroreduction Performance”: W. Zhu, L. Zhang, P. Yang, C. Hu, Z. Luo, X. Chang, Z.-J. Zhao, J. Gong, Angew. Chem. Int. Ed. 2018, https://doi.org/10.1002/anie.201806432; Angew. Chem. 2018, https://doi.org/10.1002/ange.201806432. The work of J. Gong has been featured on the cover of Angewandte Chemie: “Dendritic Hematite Nanoarray Photoanode Modified with a Conformal Titanium Dioxide Interlayer for Effective Charge Collection”: Z. Luo, T. Wang, J. Zhang, C. Li, H. Li, J. Gong, Angew. Chem. Int. Ed. 2017, 56, 12878; Angew. Chem. 2017, 129, 13058. Date of birth: June 24, 1979 Position: Cheung Kong Chair Professor, School of Chemical Engineering and Technology, Tianjin University E-mail: jlgong@tju.edu.cn Homepage: www.gonglab.org ORCID: 0000-0001-7263-318X Education: 2001 BS, Tianjin University 2004 MS, Tianjin University 2008 PhD supervised by C. Buddie Mullins, University of Texas at Austin 2009–2010 Postdoc with Prof. George M. Whitesides, Harvard University Awards: 2014 Te-Pan Hou Chemical Engineering Innovation Award; 2015 NSFC Outstanding Young Investigator Award; 2016 Cheung Kong Chair Professor (Ministry of Education); 2017 The SCEJ (Society of Chemical Engineers, Japan) Award for Outstanding Asian Researcher and Engineer; 2017 ACS Sustainable Chemistry & Engineering Lectureship Award Current research interests: Heterogeneous catalysis; surface science; green energy conversion; CO2 utilization; synthesis and applications of nanostructured material Hobbies: Hiking, reading, soccer, table tennis, billiards My favorite place on earth is my hometown—Lanzhou, Gansu Province. I chose chemistry as a career because chemistry changes the world and chemistry creates the world. If I won the lottery, I would donate the money to support education in underdeveloped areas of northwest China. If I were not a scientist, I would probably be a military surgeon or a professional cat/dog breeder. Guaranteed to make me smile is when I see my daughter after I get home from work or traveling. My favorite author (fiction) is The Count of Monte Cristo (Alexandre Dumas). My favorite food is Lanzhou beef noodles. My favorite music is albums by Wei Dou (a Chinese rock singer). My favorite motto is “Seek the truth from facts”. I like refereeing because it makes me more critical and thoughtful. My 5 top papers: 1“Enhanced Surface Reaction Kinetics and Charge Separation of p–n Heterojunction Co3O4/BiVO4 Photoanodes”: X. Chang, T. Wang, P. Zhang, J. Zhang, A. Li, J. Gong, J. Am. Chem. Soc. 2015, 137, 8356. (Properly designed cocatalysts can achieve higher charge-separation efficiency in the bulk as well as faster surface reaction kinetics.) 2“Sub-10 nm rutile titanium dioxide nanoparticles for efficient visible-light-driven photocatalytic hydrogen production”: L. Li, J. Yan, T. Wang, Z.-J. Zhao, J. Zhang, J. Gong, N. Guan, Nat. Commun. 2015, 6, 5881. (New insights into the functionalities of defects in visible-light photocatalytic activity.) 3“Synergistic Cocatalytic Effect of Carbon Nanodots and Co3O4 Nanoclusters for the Photoelectrochemical Water Oxidation on Hematite”: P. Zhang, T. Wang, X. Chang, L. Zhang, J. Gong, Angew. Chem. Int. Ed. 2016, 55, 5851; Angew. Chem. 2016, 128, 5945. (Can help design effective cocatalytic systems with multiple functional components.) 4“Hydroxyl-Mediated Non-oxidative Propane Dehydrogenation over VOX/γ-Al2O3 Catalysts with Improved Stability”: Z.-J. Zhao, T. Wu, C. Xiong, G. Sun, R. Mu, L. Zeng, J. Gong, Angew. Chem. Int. Ed. 2018, 57, 6791; Angew. Chem. 2018, 130, 6907. (Catalytic performance is closely connected to the concentration of superficial V−OH species on the catalyst.) 5“On the role of Ce in CO2 adsorption and activation over lanthanum species”: X. Li, Z.-J. Zhao, L. Zeng, J. Zhao, H. Tian, S. Chen, K. Li, S. Sang, J. Gong, Chem. Sci. 2018, 9, 3426. (Ce addition can promote the formation of bidentate carbonate, and results in the best coke elimination performance.) Volume57, Issue36September 3, 2018Pages 11504-11504 ReferencesRelatedInformation

Hydroxyl-Mediated Non-oxidative Propane Dehydrogenation over VOx /γ-Al2 O3 Catalysts with Improved Stability.

Supported vanadium oxides are one of the most promising alternative catalysts for propane dehydrogenation (PDH) and efforts have been made to improve its catalytic performance. However, unlike Pt-based catalysts, the nature of the active site and surface structure of the supported vanadium catalysts under reductive reaction conditions still remain elusive. This paper describes the surface structure and the important role of surface-bound hydroxyl groups on VOx / γ-Al2 O3 catalysts under reaction conditions employing in situ DRIFTS experiments and DFT calculations. It is shown that hydroxyl groups on the VOx /Al2 O3 catalyst (V-OH) are produced under H2 pre-reduction, and the catalytic performance for PDH is closely connected to the concentration of V-OH species on the catalyst. The hydroxyl groups are found to improve the catalyst that leads to better stability by suppressing the coke deposition.

Co-Production of Ethylene and Hydrogen Via Non-Oxidative Dehydrogenation of Ethane Below 400oc

Ethylene, a major intermediate in manufacture of polymers and petrochemicals, is conventionally produced by energy intensive high temperature (higher than 800oC) steam cracking of ethane. By using a proton-conducting solid oxide cell (SOC), ethylene and pure hydrogen can be co-produced at a much lower temperature via electrochemical dehydrogenation. In this paper, we report high efficient co-production of hydrogen and ethylene on a proton-conducting Ni-BaZr0.1Ce0.7Y0.2–xYbxO3-δ (BZCYYb) hydrogen electrode supported SOC below 400oC. The SOC presents high Faraday efficiency as well as an ethylene selectivity close to 100%. Our approach decreases the processing energy demand dramatically with no CO2 emission when compared with the traditional ethane steam cracking process. The low temperature electrochemical dehydrogenation process in this study provides a promising prospective for next-generation petrochemical manufacturing, shifting the paradigm from thermal chemical practice to energy-saving and eco-friendly regime.

NiAu Single Atom Alloys for the Non-oxidative Dehydrogenation of Ethanol to Acetaldehyde and Hydrogen

Gold is examined here as an alternative to copper for the selective dehydrogenation of ethanol to acetaldehyde and hydrogen. Despite its high selectivity, gold is only active at temperatures higher than 250 °C for this reaction. We demonstrate that addition of a small amount of Ni on either supported or unsupported Au surfaces induces resistance to sintering, along with a beneficial effect on the catalytic activity. NiAu alloys prepared here with Ni as the minority component to the limit of atomic dispersion in the gold surfaces, catalyze the reaction beginning below 150 °C. A significant decrease of the apparent activation energy from 96 ± 3 kJ/mol for the monometallic Au to 59 ± 5 kJ/mol for the alloy was found. The Ni dispersion and concentration as a function of gas environment was followed by in situ DRIFTS and by XPS. The stability of the catalyst morphology was investigated through post-reaction microscopy imaging and long-term stability tests under reaction conditions. As shown via dynamic reaction experiments, acetaldehyde and H2 were selectively produced up to 280 °C. A small drop of selectivity at higher temperatures is attributed to the formation of Ni clusters, as proven by CO-DRIFTS on the used sample. Comparison with samples of higher Ni loading, where Ni clusters are formed, clearly shows that they catalyze the undesired full decomposition of ethanol to CO, CH4, and H2.

Sulfur introduction in V–K/γ-Al2O3 catalyst for high performance in the non-oxidative dehydrogenation of isobutane

Sulfur was introduced, for the first time into V–K/γ-Al2O3 catalysts, due to which their performance in the non-oxidative dehydrogenation of isobutane promoted remarkably.