Catalysts For Dehydrogenation Research Articles

One stone, three birds strategy for synthesis of N-doped activated carbon-supported surface-enriched and redispersed Pd NPs via plasma for formic acid dehydrogenation

Rational design of supported Pd catalysts with excellent performance for H2 production via inexpensive and sustainable formic acid (FA) dehydrogenation remains challenging. N-doped activated carbon (AC)-supported surface-enriched and redispersed Pd nanoparticles (Pd/ACCP (250 W, 10 min)) with enhanced performance for FA dehydrogenation were prepared via plasma-assisted thermal reduction (input power: 250 W, discharge time: 10 min). The TOFinitial (initial turnover frequency) of Pd/ACCP (250 W, 10 min) reached 1276 h−1, and gas generation over it for the first and third reaction cycles was 1.11 and 1.52 times higher, respectively, than that of Pd/ACC and 1.25 and 12.40 times higher, respectively, than that of Pd/AC (Sigma–Aldrich). Characterization results indicated that Pd/ACCP (250 W, 10 min) had surface-enriched and redispersed Pd species, owing to the plasma etching and strong electric field, large specific surface area, small Pd particle size, and high Pd/C atomic ratio. Enhanced N doping of AC was achieved via plasma treatment, and N mainly existed as highly active pyridine nitrogen. The plasma-based strategy yielded Pd/ACCP (250 W, 10 min) with excellent catalytic performance for FA dehydrogenation. This study provides insights into plasma-controllable synthesis of supported metal catalysts and delivers a new rational design concept of FA dehydrogenation catalysts.

Copper Phosphinate Complexes as Molecular Precursors for Ethanol Dehydrogenation Catalysts.

Nowadays, the production of acetaldehyde heavily relies on the petroleum industry. Developing new catalysts for the ethanol dehydrogenation process that could sustainably substitute current acetaldehyde production methods is highly desired. Among the ethanol dehydrogenation catalysts, copper-based materials have been intensively studied. Unfortunately, the Cu-based catalysts suffer from sintering and coking, which lead to rapid deactivation with time-on-stream. Phosphorus doping has been demonstrated to diminish coking in methanol dehydrogenation, fluid catalytic cracking, and ethanol-to-olefin reactions. This work reports a pioneering application of the well-characterized copper phosphinate complexes as molecular precursors for copper-based ethanol dehydrogenation catalysts enriched with phosphate groups (Cu-phosphate/SiO2). Three new catalysts (CuP-1, CuP-2, and CuP-3), prepared by the deposition of complexes {Cu(SAAP)}n (1), [Cu6(BSAAP)6] (2), and [Cu3(NAAP)3] (3) on the surface of commercial SiO2, calcination at 500 °C, and reduction in the stream of the forming gas 5% H2/N2 at 400 °C, exhibited unusual properties. First, the catalysts showed a rapid increase in catalytic activity. After reaching the maximum conversion, the catalyst started to deactivate. The unusual behavior could be explained by the presence of the phosphate phase, which made Cu2+ reduction more difficult. The phosphorus content gradually decreased during time-on-stream, copper was reduced, and the activity increased. The deactivation of the catalyst could be related to the copper diffusion processes. The most active CuP-1 catalyst reaches a maximum of 73% ethanol conversion and over 98% acetaldehyde selectivity at 325 °C and WHSV = 2.37 h-1.

Construction of highly stable and efficient Zn-based catalyst via Mg modification for propane dehydrogenation

Zn-based catalysts are considered a kind of efficient catalysts for propane dehydrogenation (PDH) because of their low price and non-toxicity. However, Zn-based catalysts still face problems such as the limited diffusion of reaction gas, non-uniform distribution of Zn species, and easy coking. Here, a novel double-layered silicalite-1 (DS-1) support with high specific surface area was synthesized by a crystal growth method, and an alkaline additive modification strategy has been adopted to prepare the Mg-modified Zn-based catalyst (0.1Mg5Zn@DS-1) in order to improve the catalytic activity and stability. The physical characterization results reveal that the Mg modification induces the enhanced electronic interactions between Zn sites and Mg species. Besides, the modified Mg species also reduce the Lewis acidity, allowing easier desorption of propylene and improving the propylene selectivity with anti-coking property. Furthermore, PDH evaluation results demonstrate that the optimal 0.1Mg5Zn@DS-1 catalyst achieves the propylene yield of ∼44 %, propylene selectivity of ∼95 % as well as outstanding stability and regeneration ability. This work provides a novel insight into the design of Zn-based catalysts with high activity and excellent stability.

Anchoring PdAu nanoclusters inside aminated metal-organic framework for fast dehydrogenation of formic acid

Liquid sunshine formic acid (FA), which is obtainable through CO2 hydrogenation with green H2 or biomass processing, is regarded as a prospective liquid organic hydrogen carrier (LOHC) owing to its high volumetric capacity (53 g H2 L−1), stability, and renewability. The search for effective catalysts to produce H2 from additive-free FA under ambient conditions is necessary but remains a challenge. Herein, highly dispersed and ultrafine PdAu nanoclusters (NCs) (1.2 nm) anchored by the aminated metal–organic framework (NH2-MIL-101) were successfully fabricated using a facile wet-chemical method and employed as a superior catalyst for formic acid dehydrogenation (FAD). The resulting PdAu/NH2-MIL-101 catalyst demonstrates 100 % H2 selectivity and superior performance with a turnover frequency value reaching 2921.0 h−1 at 323 K without any additive. Under similar conditions, this value is higher than the majority of published MOF-based FAD heterogeneous catalysts. The superior performance of PdAu/NH2-MIL-101 originates from a synergistic combination of the promoting effect of amino groups, the effective electronic coupling of Pd and Au, and the strong metal-support interaction between PdAu NCs and NH2-MIL-101, which promote the formation of reactive PdAu NCs and thus greatly improve catalytic performance. This work may provide important inspiration for developing highly efficient catalysts and strongly promote FA as a promising LOHC for chemical H2 storage.

Closed-loop optimization of catalysts for oxidative propane dehydrogenation with CO2 using artificial intelligence

Oxidative propane dehydrogenation with CO2 (ODPC) is an economical and ecofriendly process that produces propylene and consumes CO2 simultaneously. In this study, the catalyst composition for the ODPC reaction was optimized using a closed-loop optimization framework. A machine learning (ML) model was trained to predict the propylene yield and CO2 conversion using an in-house experimental database obtained from metal oxide catalysts containing various elements. The trained ML model optimized the chemical composition of the catalysts and simultaneously maximized the propylene yield and CO2 conversion using a metaheuristic algorithm. The proposed catalysts were prepared and their ODPC performance was evaluated. The data were included in the initial database to retrain the ML model. After this closed-loop optimization for 4 cycles, the proposed catalysts, which comprised four or five metal components, exhibited an enhanced ODPC performance compared with that of the initial database, which contained up to three metal components. Density functional theory calculations and characterization techniques were performed to investigate the role of each metal in the proposed catalyst. This study suggested a framework to optimize the chemical composition of multi-component catalysts to enhance the propylene yield and CO2 activity in the ODPC reaction.

CoNi Nanoparticles Supported on Hierarchical SAPO-34 Zeolite as a Catalyst for the Hydrolytic Dehydrogenation of Ammonia Borane

CoNi Nanoparticles Supported on Hierarchical SAPO-34 Zeolite as a Catalyst for the Hydrolytic Dehydrogenation of Ammonia Borane

PtSn propane dehydrogenation catalyst supported by γ-Al2O3: insight into the supports and active species interaction

PtSn propane dehydrogenation catalyst supported by γ-Al2O3: insight into the supports and active species interaction

Secondary reactions of propylene on Ga/γ-Al2O3 propane dehydrogenation catalysts

Supported Ga catalysts have been widely studied for propane dehydrogenation (PDH). In this study, Ga/γ-Al2O3 catalysts were evaluated for PDH. The propylene selectivity decreased with increasing propane conversion. It is generally thought that propylene and light gas by-products occur from chemisorbed propane and are, therefore, primary products. By extrapolating the product selectivities to zero per cent propane conversion, the initial propylene selectivity was near 100% and is a primary product. The light gas selectivities, however, are near 0% indicating that these are secondary products. The direct reaction of propylene produced the same light gas products, e.g., methane, ethylene, propane, butenes and pentenes, observed for PDH and confirmed that these occur by an independent reaction of propylene. Thus, while the intrinsic PDH propylene selectivity is high, these secondary propylene reactions lower the selectivity, especially, at higher conversions and higher partial pressures.

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

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

Agglomerated Oxidative Dehydrogenation (ODH) Catalyst

Agglomerated Oxidative Dehydrogenation (ODH) Catalyst

Reviews on Homogeneous and Heterogeneous Catalysts for Dehydrogenation and Recycling of Formic Acid: Progress and Perspectives

Reviews on Homogeneous and Heterogeneous Catalysts for Dehydrogenation and Recycling of Formic Acid: Progress and Perspectives

Facile dehydrogenation of MgH2 enabled by γ-graphyne based single-atom catalyst

Solid-state hydrogen storage is a promising roadmap for the safe and efficient utilization of hydrogen energy due to its moderate operating environment and high hydrogen storage density. However, as a representative solid-state hydrogen storage material, magnesium hydride (MgH2) is significantly limited in the commercial application due to its sluggish kinetics in the dehydrogenation process. Single-atom catalysts are a promising solution to this dilemma. However, the promising graphene-based single-atom catalysts are not yet sufficient to meet the dehydrogenation needs in engineering. To further address this dilemma, we designed a novel γ-graphyne based single-atom catalysts including eight 3d transition metals for promoting the dehydrogenation process of MgH2. Through using spin-polarized density functional theory calculations, we found that the energy barrier for MgH2 dehydrogenation has been significantly reduced even to 0.70 eV, which is far lower than the current graphene-based single-atom catalyst. In detail, the migration trajectory of hydrogen atom in the dehydrogenation process has been observed and confirmed using the ab initio molecular dynamics simulations. To investigate the intrinsic origin for its high catalytic activity of single-atom catalyst, we analyze the HMg bond activation mechanism through the electron localization function, charge density difference and crystal orbital Hamiltonian population. Finally, we found the relationship between energy barrier with electronic structure of single-atom catalyst, such as electrostatic potential and system electronegativity. This work can not only provide new ideas for the optimize of dehydrogenation catalyst, but also lay a theoretical foundation for the design of novel energy storage material.

Reducible tungsten(VI) oxide-supported ruthenium(0) nanoparticles: highly active catalyst for hydrolytic dehydrogenation of ammonia borane.

Reducible WO3 powder with a mean diameter of 100 nm is used as support to stabilize ruthenium(0) nanoparticles. Ruthenium(0) nanoparticles are obtained by NaBH4 reduction of ruthenium(III) precursor on the surface of WO3 support at room temperature. Ruthenium(0) nanoparticles are uniformly dispersed on the surface of tungsten(VI) oxide. The obtained Ru0/WO3 nanoparticles are found to be active catalysts in hydrolytic dehydrogenation of ammonia borane. The turnover frequency (TOF) values of the Ru0/WO3 nanocatalysts with the metal loading of 1.0%, 2.0%, and 3.0% wt. Ru are 122, 106, and 83 min-1, respectively, in releasing hydrogen gas from the hydrolysis of ammonia borane at 25.0 °C. As the Ru0/WO3 (1.0% wt. Ru) nanocatalyst with an average particle size of 2.6 nm provides the highest activity among them, it is extensively investigated. Although the Ru0/WO3 (1.0% wt. Ru) nanocatalyst is not magnetically separable, it has extremely high reusability in the hydrolysis reaction as it preserves 100% of initial catalytic activity even after the 5th run of hydrolysis. The high activity and reusability of Ru0/WO3 (1.0% wt. Ru) nanocatalyst are attributed to the favorable metal-support interaction between the ruthenium(0) nanoparticles and the reducible tungsten(VI) oxide. The high catalytic activity and high stability of Ru0/WO3 nanoparticles increase the catalytic efficiency of precious ruthenium in hydrolytic dehydrogenation of ammonia borane.

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

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

Highly efficient immobilized PN3P-pincer iridium catalyst for dehydrogenation of neat formic acid

Formic acid (FA) has been well recognized as one of the most promising hydrogen carriers. The dehydrogenation of the FA could offer an efficient process to on-demand hydrogen generation with a suitable catalyst. Homogeneous catalysts have demonstrated superior activity and selectivity compared to traditional heterogeneous catalysis. However, the latter is preferred for large-scale applications. By incorporating the homogeneous organometallic complex onto an appropriate support, the unique features of both types of catalysts can be combined and utilized effectively. Herein, we synthesized an immobilized PN3P-Ir pincer catalyst (2) supported onto KCC-1, a 3D fibrous silica nanosphere that exhibits a high surface area and contains a tetracoordinate aluminum site. To reduce the use of volatile additives, the choice of cesium formate (CsO2CH) was found to be crucial as at 80–90 °C, CsO2CH could act as a reaction medium and serve as basic additive. Remarkable reactivities under neat conditions were achieved with a TOF of 13,290 h-1 and a TON of up to 540,000. The comparative study indicates a significant improvement of 2 from its homogenous counterpart, PN3P-IrH3 (1).

Highly efficient dehydrogenation of dodecahydro-N-ethylcarbazole over Al2O3 supported PdCo bimetallic nanocatalysts prepared by galvanic replacement

NEC is one of the most promising liquid organic hydrogen storage materials. The highly efficient and low cost dehydrogenation catalysts are crucial for large-scale hydrogen storage. In this paper, Co/Al2O3 precursors were prepared by chemical reduction, and then a series of Pd1Con/Al2O3 catalysts for 12H-NEC dehydrogenation was prepared by galvanic replacement of Pd2+ using Co as a template and reducing agent. The prepared catalysts were characterized by TEM, FT-IR, XPS, H2-TPR and H2-TPD. The results demonstrated that Pd1Con NPs were uniformly dispersed over the surface of Al2O3 in the form of Co@Pd core-shell structure, CoPd alloy and PdNPs, with an average particle size of 2.78 nm. The electron transfer occurred between Co and Pd. For the dehydrogenation of H12-NEC, the produced Pd1Co5/Al2O3 catalyst exhibited excellent catalytic activity. The dehydrogenation efficiency was 100% at 180 °C for 3 h and 98.5% at 150 °C for 6 h, and TOF reached 1.414 gH2/gPd min−1, which was significantly higher than that of monometallic Pd/Al2O3 catalysts and that reported in the literature. The kinetic studies of the catalytic 12H-NEC dehydrogenation showed that 4H-NEC→NEC is the rate-limiting step with the highest apparent activation energy of 68.72 kJ/mol. The hydrogen release efficiency remained essentially unchanged after four cycles.

Unraveling surface and bulk dynamics of iron(III) molybdate during oxidative dehydrogenation using operando and transient spectroscopies

Iron(III) molybdate (Fe2(MoO4)3) is a commercial catalyst for the oxidative dehydrogenation (ODH) of methanol, but it has recently been shown to be relevant for other substrates as well. Despite its commercial use, a detailed mechanistic understanding of Fe2(MoO4)3 catalysts at the surface and in the bulk has been lacking, largely hampered by the lack of suitable spectroscopic methods, directly applicable under reaction conditions. Using propane ODH as an example, we highlight the potential of operando Raman and impedance spectroscopy combined with transient IR spectroscopy, to identify surface active sites and monitor the hydrogen transfer and oxygen dynamics. By comparison with the behavior of reference compounds (MoO3, MoOx/Fe2O3) a mechanistic model is proposed. The presence of iron greatly influences the reactivity behavior via oxygen diffusion but is moderated in its oxidative capacity by surface MoOx. Our approach directly elucidates fundamental properties of Fe2(MoO4)3 of general importance to selective oxidation catalysis.

Design of Ammonia Borane Dehydrogenation Catalysts Using Previous Study Data, Public Data, and Machine Learning

Design of Ammonia Borane Dehydrogenation Catalysts Using Previous Study Data, Public Data, and Machine Learning

When Pt nanoparticles meet oxygen-deficient Co3O4: Enabling superior performance towards on-demand hydrogen generation from hydrolytic dehydrogenation of dimethylamine borane

The regulation of the metal-support interaction in heterogeneous catalysts can promote the activation of reactants, which is beneficial for the hydrolytic dehydrogenation reaction. Herein, the hydrolytic dehydrogenation of dimethylamine borane (DMAB) is systematically studied on the oxygen vacancy (Ov) enriched Pt-Co3O4 heterogeneous catalyst with the metal-support interaction. It is found that the metallic Pt site facilitates the adsorption of DMAB molecules and the Ov on Co3O4 support as an electron-rich center cooperates with the adjacent Pt site to dissociate water molecules. The in situ Raman and attenuated total reflectance (ATR)-Fourier transform infrared (FTIR) spectroscopy reveal the effective activation and cleavage of the O-H in water and the B-H in DMAB over the Pt-Co3O4 catalyst. The optimal Pt-Co3O4 catalyst exhibits the extraordinary activity for the catalytic hydrolysis of DMAB at 303 K, delivering a high specific hydrogen generation rate (64063 mL min−1 gpt−1) and a competitive turnover frequency (TOF, 23880 molH2 molPt−1 h−1). This performance outperforms most of the reported heterogeneous catalysts for DMAB dehydrogenation. More importantly, the Pt-Co3O4 catalyst achieves the desirable on-demand hydrogen production by using special chemical switches. This finding provides the fundamental understanding of metal-oxide systems with the collaborative interfacial catalysis for boosting DMAB dehydrogenation.

Creation of a Highly Active Small Cu-Based Catalyst Derived from Copper Aluminium Layered Double Hydroxide Supported on α-Al2 O3 for Acceptorless Alcohol Dehydrogenation.

A highly dispersed carbonate-intercalated Cu2+ -Al3+ layered double hydroxide (CuAl LDH) was created on an unreactive α-Al2 O3 surface (CuAl LDH@α-Al2 O3 ) via a simple coprecipitation method of Cu2+ and Al3+ under alkaline conditions in the presence of α-Al2 O3 . A highly reducible CuO nanoparticles was generated, accompanied by the formation of CuAl2 O4 on the surface of α-Al2 O3 (CuAlO@α-Al2 O3 ) after calcination at 1073 K in air, as confirmed by powder X-ray diffraction (XRD) and Cu K-edge X-ray absorption near edge structure (XANES). The structural changes during the progressive heating process were monitored by using in-situ temperature-programmed synchrotron XRD (tp-SXRD). The layered structure of CuAl LDH@α-Al2 O3 completely disappeared at 473 K, and CuO or CuAl2 O4 phases began to appear at 823 K or 1023 K, respectively. Our synthesised CuAlO@α-Al2 O3 catalyst was highly active for the acceptorless dehydrogenation of benzylic, aliphatic, or cyclic aliphatic alcohols; the TON based on the amount of Cu increased to 163 from 3.3 of unsupported CuAlO catalyst in 1-phenylethanol dehydrogenation. The results suggested that Cu0 was obtained from the reduction of CuO in the catalyst matrix during the reaction without separate reduction procedure and acted as a catalytically active species.