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Journal ArticleDOI: 10.1039/D0CY01980A

Revealing fundamentals affecting activity and product selectivity in non-oxidative propane dehydrogenation over bare Al2O3

02 Mar 2021-Catalysis Science & Technology (The Royal Society of Chemistry)-Vol. 11, Iss: 4, pp 1386-1394
Abstract: A detailed study was carried out to elucidate the factors affecting the activity and, particularly, selectivity of bare Al2O3 in the non-oxidative propane dehydrogenation (PDH) to propene under industrially relevant conditions. A series of samples were synthesized by a precipitation method upon varying the ratio of OH−/Al3+ in the solution. This ratio was established to affect the ability of Al2O3 to form aluminium cations with lower coordination (Alcus) than regular surface Al3+ sites. Such defective sites show higher activity for propene formation and lower ability for coke formation. In addition to the preparation method, the kind of reducing agent for Al2O3 is decisive for creation of the desired defects, with CO showing higher reactivity owing to its ability to react with surface OH groups.

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Topics: Propene (56%), Dehydrogenation (55%)

5 results found

Open accessJournal ArticleDOI: 10.3390/CATAL11091070
03 Sep 2021-Catalysts
Abstract: Propylene is one of the most important feedstocks in the chemical industry, as it is used in the production of widely diffused materials such as polypropylene. Conventionally, propylene is obtained by cracking petroleum-derived naphtha and is a by-product of ethylene production. To ensure adequate propylene production, an alternative is needed, and propane dehydrogenation is considered the most interesting process. In literature, the catalysts that have shown the best performance in the dehydrogenation reaction are Cr-based and Pt-based. Chromium has the non-negligible disadvantage of toxicity; on the other hand, platinum shows several advantages, such as a higher reaction rate and stability. This review article summarizes the latest published results on the use of platinum-based catalysts for the propane dehydrogenation reaction. The manuscript is based on relevant articles from the past three years and mainly focuses on how both promoters and supports may affect the catalytic activity. The published results clearly show the crucial importance of the choice of the support, as not only the use of promoters but also the use of supports with tuned acid/base properties and particular shape can suppress the formation of coke and prevent the deep dehydrogenation of propylene.

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Topics: Dehydrogenation (59%), Catalysis (50%)

2 Citations

Journal ArticleDOI: 10.1021/ACSCATAL.1C02859
Lohit Sharma1, Xiao Jiang2, Zili Wu2, Andrew DeLaRiva3  +4 moreInstitutions (4)
22 Oct 2021-ACS Catalysis
Abstract: Developing an earth-abundant catalyst that is sulfur-tolerant, active, and highly selective is of great interest for valorizing natural gas streams containing sour gas. A tin-modified alumina catal...

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Topics: Dehydrogenation (59%), Sour gas (57%), Propane (55%) ... read more

1 Citations

Open accessJournal ArticleDOI: 10.1039/D1SC05381G
Pedro Castro-Fernández1, Monu Kaushik2, Zhuoran Wang2, Deni Mance1  +7 moreInstitutions (2)
01 Dec 2021-Chemical Science
Abstract: Gallia–alumina (Ga,Al)2O3(x : y) spinel-type solid solution nanoparticle catalysts for propane dehydrogenation (PDH) were prepared with four nominal Ga : Al atomic ratios (1 : 6, 1 : 3, 3 : 1, 1 : 0) using a colloidal synthesis approach. The structure, coordination environment and distribution of Ga and Al sites in these materials were investigated by X-ray diffraction, X-ray absorption spectroscopy (Ga K-edge) as well as 27Al and 71Ga solid state nuclear magnetic resonance. The surface acidity (Lewis or Bronsted) was probed using infrared spectroscopy with pyridine and 2,6-dimethylpyridine probe molecules, complemented by element-specific insights (Ga or Al) from dynamic nuclear polarization surface enhanced cross-polarization magic angle spinning 15N{27Al} and 15N{71Ga} J coupling mediated heteronuclear multiple quantum correlation NMR experiments using 15N-labelled pyridine as a probe molecule. The latter approach provides unique insights into the nature and relative strength of the surface acid sites as it allows to distinguish contributions from Al and Ga sites to the overall surface acidity of mixed (Ga,Al)2O3 oxides. Notably, we demonstrate that (Ga,Al)2O3 catalysts with a high Al content show a greater relative abundance of four-coordinated Ga sites and a greater relative fraction of weak/medium Ga-based surface Lewis acid sites, which correlates with superior propene selectivity, Ga-based activity, and stability in PDH (due to lower coking). In contrast, (Ga,Al)2O3 catalysts with a lower Al content feature a higher fraction of six-coordinated Ga sites, as well as more abundant Ga-based strong surface Lewis acid sites, which deactivate through coking. Overall, the results show that the relative abundance and strength of Ga-based surface Lewis acid sites can be tuned by optimizing the bulk Ga : Al atomic ratio, thus providing an effective measure for a rational control of the catalyst performance.

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Journal ArticleDOI: 10.1016/J.APSUSC.2021.151205
Abstract: Incipient wetness impregnation was used to deposit dispersed tin (Sn) atoms on γ-Al2O3. The morphology and structure of the catalysts were characterized using Raman, X-ray Photoelectron Spectroscopy (XPS), and low energy ion scattering (LEIS) combined with N2-physisorption and in situ infrared diffuse reflectance spectroscopy (DRIFTS) using NH3 and CO2 as probe molecules, H2- temperature-programmed reduction (H­2-TPR), and steady-state reaction kinetics measurements. The effects of H2S on the surface chemical composition and structure of the resulting catalysts were systematically studied. The results showed isolated and well-dispersed Sn oxide sites of the deposited catalyst with nanoparticles observed only at relatively high coverages of 10% Sn at a coverage ranging from 0.48 to 2.8 Sn atoms nm−2. DRIFT spectroscopy evidenced a decrease in the number of Lewis acid sites on H2S treated Sn/Al2O3 suggesting surface tin species re-dispersing and blocking the active sites of γ-Al2O3. Overall, the surface analysis results presented here suggest that the active catalytic sites in the presence of H2S involve Al2O3 rather than bulk sulfide and Sn atoms dispersed over alumina towards propane dehydrogenation.

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Topics: Low-energy ion scattering (57%), Incipient wetness impregnation (56%), Dehydrogenation (53%) ... read more

Journal ArticleDOI: 10.1021/ACS.JPCC.1C03175
Abstract: Zn-based Al2O3-suported materials have been proposed as inexpensive and environmentally friendly catalysts for the direct dehydrogenation of propane (PDH), however, our understanding of these catalysts’ structure and deactivation routes is still limited. Here, we correlate the catalytic activity for PDH of a series of Zn-based Al2O3 catalysts with their structure and structural evolution. To this end, three model catalysts are investigated. (i) ZnO/Al2O3 prepared by atomic layer deposition (ALD) of ZnO onto γ-Al2O3 followed by calcination at 700 °C, which yields a core-shell spinel zinc aluminate/γ-Al2O3 structure. (ii) Zinc aluminate spinel nanoparticles (ZnxAlyO4 NPs) prepared via a hydrothermal method. (iii) A reference core-shell ZnO/SiO2 catalyst prepared by ALD of ZnO on SiO2. The catalysts are characterized in detail by synchrotron X-ray powder diffraction (XRD), Zn K-edge X-ray absorption spectroscopy (XAS), and 27Al solid state nuclear magnetic resonance (ssNMR). These experiments allowed us to identify tetrahedral Zn sites in close proximity to Al sites of a zinc aluminate spinel phase (ZnIV–O–AlIV/VI linkages) as notably more active and selective in PDH relative to the supported ZnO wurtzite phase (ZnIV–O– ZnIV linkages) in ZnO/SiO2. The best performing catalyst, 50ZnO/Al2O3 gives 77% selectivity to propene (gaseous products based) at 9 mmol C3H6 gcat−1 h−1 space time yield (STY) after 3 min of reaction at 600 °C. On the other hand, the core-shell ZnO/Al2O3 catalyst shows an irreversible loss of activity over repeated PDH and air-regeneration cycles, explained by Zn depletion on the surface due to its diffusion into subsurface layers or the bulk. ZnxAlyO4 NPs gave a comparable initial selectivity and catalytic activity as 50ZnO/Al2O3. With time on stream, ZnxAlyO4 NPs deactivate due to the formation of coke at the catalyst surface, yet the extend of coke deposition is lower than for the ZnO/Al2O3 catalysts, and the activity of ZnxAlyO4 NPs can be regenerated almost fully using calcination in air.

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Topics: Aluminate (57%), Zinc (53%), X-ray absorption spectroscopy (53%) ... read more

30 results found

Open accessJournal ArticleDOI: 10.1038/S41467-018-06967-8
Guodong Sun1, Zhi-Jian Zhao1, Rentao Mu1, Shenjun Zha1  +10 moreInstitutions (5)
Abstract: Noble-metal alloys are widely used as heterogeneous catalysts. However, due to the existence of scaling properties of adsorption energies on transition metal surfaces, the enhancement of catalytic activity is frequently accompanied by side reactions leading to a reduction in selectivity for the target product. Herein, we describe an approach to breaking the scaling relationship for propane dehydrogenation, an industrially important reaction, by assembling single atom alloys (SAAs), to achieve simultaneous enhancement of propylene selectivity and propane conversion. We synthesize γ-alumina-supported platinum/copper SAA catalysts by incipient wetness co-impregnation method with a high copper to platinum ratio. Single platinum atoms dispersed on copper nanoparticles dramatically enhance the desorption of surface-bounded propylene and prohibit its further dehydrogenation, resulting in high propylene selectivity (~90%). Unlike previous reported SAA applications at low temperatures (<400 °C), Pt/Cu SAA shows excellent stability of more than 120 h of operation under atmospheric pressure at 520 °C.

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Topics: Dehydrogenation (57%), Platinum (56%), Catalysis (53%) ... read more

188 Citations

Journal ArticleDOI: 10.1002/ANIE.201507119
Lei Shi1, Gao-Ming Deng1, Wen-Cui Li1, Shu Miao2  +3 moreInstitutions (2)
16 Nov 2015-Angewandte Chemie
Abstract: In heterogeneous catalysis, supports play a crucial role in modulating the geometric and electronic structure of the active metal phase for optimizing the catalytic performance. A γ-Al2O3 nanosheet that contains 27% pentacoordinate Al(3+) sites can nicely disperse and stabilize raft-like Pt-Sn clusters as a result of strong interactions between metal and support. Consequently, there are strong electronic interactions between the Pt and Sn atoms, resulting in an increase in the electron density of the Pt sites. When used in the propane dehydrogenation reaction, this catalyst displayed an excellent specific activity for propylene formation with >99% selectivity, and superior anti-coking and anti-sintering properties. Its exceptional ability to maintain the high activity and stability at ultrahigh space velocities further showed that the sheet construction of the catalyst facilitated the kinetic transfer process.

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Topics: Dehydrogenation (54%), Heterogeneous catalysis (53%), Catalysis (52%)

174 Citations

Journal ArticleDOI: 10.1016/J.CERAMINT.2006.05.002
Abstract: Al2O3–ZrO2 composite gel precursor powder containing 5–15 mol% ZrO2 was prepared by wet chemical route. The washed gel containing pseudoboehmite and amorphous zirconia was characterized with respect to DTA/TG, XRD and IR spectroscopy. The DTA/TG result indicates three-stage decomposition for pseudoboehmite and single stage decomposition for amorphous zirconia. In the calcined powder phase evolution of Al2O3 follows the sequence pseudoboehmite ! bayerite ! boehmite ! g-Al2O3 ! u-Al2O3 ! a-Al2O3, while that of ZrO2 follows amorphous ZrO2 ! t-ZrO2 ! (t + m)ZrO2. FTIR studies revealed that the number of M–OH and M–O bond increase on increasing mol% of ZrO2 due to a change in the cationic charge of the composite powder. TEM photograph of calcined powder showed both dispersed nano-size spherical particle as well as agglomerated particles. EPMA confirmed the near uniform distribution of zirconia particles in the alumina matrix. # 2006 Published by Elsevier Ltd and Techna Group S.r.l.

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171 Citations

Open accessJournal ArticleDOI: 10.1016/J.JCAT.2014.10.018
Bo Hu1, Bo Hu2, Andrew “Bean” Getsoian1, Neil M. Schweitzer3  +12 moreInstitutions (3)
Abstract: We report the synthesis, characterization, and catalytic performance for gas phase propane dehydrogenation of single-site Co2+ ions supported on silica. Spectroscopic characterization by resonance Raman, electron paramagnetic resonance, and X-ray near-edge and extended absorption fine structure revealed that tetrahedrally coordinated Co2+ ions are chemisorbed into the trisiloxane rings on the surface of amorphous silica. In situ XAS shows that Co is not oxidized by air nor reduced by hydrogen even at 650 °C. For catalytic propane dehydrogenation, single-site Co2+/SiO2 exhibits selectivities >95% at 550 °C and >90% at 650 °C with stable activity over 24 h. Calculations with hybrid density functional theory support a non-redox mechanism for activation of C–H and H–H bonds by Co2+ similar to that previously reported for single-site Zn2+/SiO2.

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130 Citations

Open accessJournal ArticleDOI: 10.1039/C6CY01886F
Avelino Corma1, E. Corresa1, Yannick Mathieu1, Laurent Sauvanaud1  +3 moreInstitutions (2)
Abstract: The possibility to fulfill the increasing market demand and producers' needs in processing crude oil, a cheap and universally available feedstock, to produce petrochemicals appears to be a very attractive strategy. Indeed, many petrochemicals are produced as side streams during crude oil refining, which primary goal remains transportation fuel production. Availability of some critical feedstocks may then depend on local refining policy. In order to improve flexibility, it has been proposed to directly crack crude oil to produce petrochemicals, in particular light olefins (ethylene, propylene, butenes), using technologies derived from fluid catalytic cracking. This paper attempts to review the main research works done on the topic in the literature in the last five decades, focussing on process as well as catalyst technology, with a special interest for fluid catalytic cracking (FCC) based technology that can be used towards maximizing chemicals from crude oil. Factors investigated include use of severe cracking conditions, on-purpose additives (from ZSM5 to more exotic, metal doped additives), recycle streams and multiple riser systems.

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Topics: Oil refinery (61%), Fluid catalytic cracking (58%), Downstream (petroleum industry) (55%) ... read more

114 Citations