Catalysts For Dehydrogenation Research Articles

Study of super-efficient defective MoVSbO catalysts used for ethane oxidative dehydrogenation by HAADF-STEM and of their thermal evolution by environmental electron microscopy and tomography

Scanning transmission electron microscopy and in situ electron tomography have been used to understand the role of structure, morphology and porosity of a remarkably active M1 phase based MoVSbO oxide catalyst for ethane oxidative dehydrogenation.

Revisiting the phosphonium salt chemistry for P-doped carbon synthesis: toward high phosphorus contents and beyond the phosphate environment.

The introduction of phosphorus and nitrogen atoms in carbo-catalysts is a common way to tune the electronic density, and thereby the reactivity, of the material, as well as to introduce surface reactive sites. Numerous environments are reported for the N atoms, but the P-doping chemistry is less explored and focuses on surface POx groups. A one-step synthesis of P/N-doped carbonaceous materials is presented here, using affordable and industrially available urea and tetrakis(hydroxymethyl)phosphonium chloride (THPC) as the N and P sources, respectively. In contrast to most of the synthetic pathways toward P-doped carbonaceous materials, the THPC precursor only displays P-C bonds along the carbon backbone. This resulted in unusual phosphorus environments for the materials obtained from direct thermal treatment of THPC-urea, presumably of type C-P-N according to 31P NMR and XPS. Alternatively, the in situ polymerization and calcination of the precursors were run in calcium chloride hydrate, used as a combined reaction medium and porogen agent. Following this salt-templating strategy led to particularly high phosphorus contents (up to 18 wt%), associated with porosities up to 600 m2 g-1. The so-formed P/N-doped porous materials were employed as metal-free catalysts for the mild oxidative dehydrogenation of N-heterocycles to N-heteroarenes at room temperature and in air.

Modulation of support properties in flower-like Pt/Al2O3 nanosheet catalysts for dehydrogenation of cycloalkanes

Flower-like Pt/Al2O3 nanosheet catalysts with modulated support properties were developed by simply varying the calcination temperature for the dehydrogenation of cycloalkanes and the support property–performance relationship was correlated.

Synthesis of an SBA-15 supported NiPtN catalyst for dehydrogenation of hydrazine hydrate

In this study, a NiPtN/SBA-15 catalyst was synthesized by a wet-impregnation method, which was validated using EDXRF, CHN analysis, XRD, SAA, and FESEM-EDS analysis and showed good catalytic activity towards dehydrogenation of hydrazine hydrate with a selectivity of 96.18% and TOF of 1133 h−1.

Waste-free life cycle of iron oxide catalysts for dehydrogenation of olefins and alkylaromatic hydrocarbons

For the processes of obtaining isoprene, styrene, divinylbenzene by dehydrogenation methods, iron oxide catalysts are used, the synthesis method of which is close to a waste-free technology. Waste is catalyst dust and chips formed during the screening stage of commercial products, flue gases formed during the activation of the catalyst. In the article, the authors consider the problems associated with waste in the production and operation of iron oxide catalysts for the dehydrogenation of olefins and alkylaromatic hydrocarbons. A method is proposed for the use of catalyst dust formed at the stage of catalyst preparation and utilization of spent iron oxide catalyst for the dehydrogenation of olefins and alkylaromatic hydrocarbons. The possibility of utilization of an ironcontaining spent catalyst for the production of iron oxide pigment and its further use in the production of building materials is shown. A number of decorative concrete samples have been prepared to study the effect of pigment as an additive on the properties of the building material. The dependence of the color gamut of the samples on the amount of pigment applied was studied, strength characteristics were studied in accordance with the regulatory requirements for strength, heat resistance and frost resistance.

Reversible transformation of sub-nanometer Ga-based clusters to isolated [4]Ga(4Si) sites creates active centers for propane dehydrogenation

This work describes how a propane dehydrogenation catalyst with isolated [4]Ga(4Si) sites can be prepared from silica-supported sub-nm gallia clusters containing [4]Ga(Ga) and [6]Ga(Ga) sites.

Highly dispersed Pd nanoparticles on a SiO2 support for dehydrogenation of dodecahydro-N-ethylcarbazole

Highly dispersed Pd catalysts for dehydrogenation of dodecahydro-N-ethylcarbazole were prepared using an amino modification method. The kinetic model and Pd particle size effect on dehydrogenation reactivity were studied.

Assessment of Reaction Kinetics for the Dehydrogenation of Perhydro-Dibenzyltoluene Using Mg- and Zn-Modified Pt/Al2O3 Catalysts

The catalysts utilized for the dehydrogenation of dibenzyltoluene-based liquid organic hydrogen carriers (LOHCs) remain crucial. The state-of-the-art catalyst for dehydrogenation of dibenzyltoluene-based LOHC still suffers from deactivation and by-product formation. This is crucial in terms of the efficiency of the industrial dehydrogenation plant for hydrogen production, cyclability as well as the cost of replacing the catalyst. The development of catalysts with optimum performance, minimum deactivation and low by-product formation is required to attain the full benefits of the LOHC technology. Therefore, in this study, the effect of Mg and Zn modification on Pt/Al2O3 catalyst is investigated for the catalytic dehydrogenation of perhydro-dibenzyltoluene (H18-DBT). In addition, an assessment of reaction kinetics is also conducted. High dehydrogenation performance was obtained for Mg-doped Pt/Al2O3 using a batch reactor at 300 °C and 6 h reaction time. In this case, the degree of dehydrogenation (dod), productivity and conversion obtained are 100%, 1.84 gH2/gPt/min and 99.9%, respectively. Moreover, the Mg-doped catalyst has resulted in a high turnover frequency (TOF) of 586 min−1 compared to the Zn-doped catalyst (269 min−1) and the undoped catalyst (202 min−1) at the reaction temperature of 300 °C. The amount of by-products increased with an increase in the catalytic activity, with the Pt/Mg-Al2O3 catalyst possessing the highest amount of by-products. The dehydrogenation of H18-DBT followed first-order reaction kinetics. In addition, the activation energy obtained using the Arrhenius model is 102, 130 and 151 kJ/mol for Pt/Al2O3, Pt/Zn-Al2O3 and Pt/Mg-Al2O3, respectively. Although the Mg-doped Pt/Al2O3 shows high activation energy, the higher performance of the catalyst suggests that mass transfer limitations have no major effect on the dehydrogenation reaction under the conditions used.

Facile fabrication of N-doped heterostructured hybrid particles based on montmorillonite incorporated with g-C3N4 for enhanced hydrogen production by NaBH4 in methanol

As an alternative to the currently increasing use of fossil fuels, hydrogen has become very important as a clean energy carrier. Herein, facile fabrication of N doped-heterostructured hybrid particles based montmorillonite (M) incorporated on graphitic carbon nitride (g-C3N4) with calcination and hydrothermal nitric acid activation was performed. The N-doped heterostructured g-C3N4-M hybrid material was used as a metal-free hybrid catalyst for NaBH4 dehydrogenation in methanol for the first time. The hydrogen generation rate (HGR) of 11,200 ml min−1 g−1 in methanol was obtained. XRD, SEM, FTIR, EDS, XPS and nitrogen adsorption/desorption analyses were used to characterize the physicochemical properties of heterostructured composites. Also, the mechanism of catalytic activity was evaluated with the obtained N-doped g-C3N4-M hybrid material.

Amine-functionalized Schiff base covalent organic frameworks supported PdAuIr nanoparticles as high-performance catalysts for formic acid dehydrogenation and hexavalent chromium reduction

Formic acid (FA) holds significant potential as a liquid hydrogen storage medium. However, it is important to improve the reaction rates and extend the practical applications of FA dehydrogenation and Cr(VI) reduction through the development of efficient heterogeneous catalysts. This study reports the synthesis of a uniformly dispersed PdAuIr nanoparticles (NPs) catalyst loaded with amine groups covalent organic frameworks (COFs). The alloyed NPs demonstrated exceptional effectiveness in FA dehydrogenation rate and Cr(VI) reduction. The initial turnover of frequency (TOF) value for FA dehydrogenation without additives was 9970 h−1 at 298 K, the apparent activation energy (Ea) was 30.3 kJ/mol and the rate constant (k) for Cr(VI) reduction was 0.742 min−1. Additionally, it showcased the ability to undergo recycling up to six times with minimal degradation in performance. The results indicate that its remarkable catalytic performance can be attributed primarily to the favorable mass transfer attributes of the aminated COFs supports, the strong metal-support interaction (SMSI), and the synergistic effects among the metals. This study offers a novel perspective on the advancement of efficient and durable heterogeneous catalysts with diverse capabilities, thereby making significant contributions to the fields of energy and environmental preservation.

Effect of Pt particle size on methylcyclohexane dehydrogenation over Pt/Al2O3 catalysts

A rational design of highly active and durable Pt catalysts for methylcyclohexane (MCH) dehydrogenation is essential for the utilization of liquid organic hydrogen carriers. Herein, a series of Pt/Al2O3 catalysts supported with a particle size of Pt ranging from 0.78 to 2.02 nm were synthesized and the effect of the particle size of Pt on the activity and stability of the catalyst for the MCH dehydrogenation were studied. The Pt loaded on Al2O3 with an actual average particle size of about 1.57 nm (Pt/Al2O3-1.57) has the highest activity and stability when compared to other Pt/Al2O3 catalysts. The hydrogen evolution rate of Pt/Al2O3-1.57 reaches about 656.12 mmol·gPt-1·min−1 while its apparent activation energy (38.05 KJ·mol−1) and deactivation rate (0.11 %/min) are the lowest. Both the poisoning experiment and the catalyst characterization demonstrate that the competition between the number of active sites and the strength of toluene adsorption explain why the particle size of Pt affects the MCH dehydrogenation. Additionally, the Pt/Al2O3-1.57 catalyst also maintains an excellent performance after three cycles of regeneration.

Amorphous CeOx Islands on Dealuminated Zeolite Beta to Stabilize Pt Nanoparticles as Efficient and Antisintering Catalysts for Propane Dehydrogenation.

Pt-based catalysts have been widely used in propane dehydrogenation due to their superior activation of C-H bonds and weak scission of C-C bonds. However, in the process of repeated calcination to remove deposited coke, the active Pt species tend to sinter, resulting in a significant decline in catalytic activity. In this study, amorphous CeOx islands loaded on dealuminated Beta zeolite were prepared via simple wetness impregnation. Then, partially embedded Pt nanoparticles in CeOx islands were obtained after reduction owing to the affinity of CeOx for Pt. In the propane dehydrogenation reaction, Pt/Ce5-SiBeta with a Ce loading of 4.55 wt % and Pt loading of 0.72 wt % exhibited the highest activity and the lowest inactivation constant at 550 °C. More importantly, due to the anchoring effect of CeOx on Pt, the catalytic activity of Pt could be recovered after a simple calcination-reduction regeneration process, avoiding the chlorination treatment for the redispersion of Pt species used in industry. In addition, to improve the selectivity of the Pt/Ce5-SiBeta catalyst, a PtSn/Ce5-SiBeta catalyst with excellent activity, selectivity, and recycling stability has been prepared by introducing Sn into Pt/Ce5-SiBeta. The use of amorphous CeOx islands to improve the sintering resistance of Pt opens up new prospects for the design of stable industrial dehydrogenation catalysts.

Cellulose nanocrystals supported ternary alloy nanoclusters catalysts for efficient hydrogen production from formic acid

Formic acid has gained a lot of attention as one of the most promising liquid hydrogen storage carriers. Designing efficient and cost-effective heterogeneous catalysts for formic acid dehydrogenation can effectively address the challenges of in-situ hydrogen production, storage and transportation. In this study, the Au0.4Pd0.6Pt0.2 alloys with an ultrafine size (∼2nm) were prepared on amino-modified cellulose nanocrystals (CNC) with a total metal consumption of only 0.01mmol. The interaction between the support and nanoclusters provided the stable local environment for the catalysts, which showed remarkable HCOOH catalytic performance at low metal dosage, with TOFinitial of is 4478 h−1 and an Ea of 54.06kJ mol−1 at 323K, and the selectivity of hydrogen is 100%. Density functional theory (DFT) calculations demonstrated that the optimized local electron environment facilitated the OH bond cleavage and reduced the binding energy barrier between H*. This finding is beneficial to the development of more effective catalysts in the future.

Coffee charcoal as a green catalyst for oxidative dehydrogenation

Nitrogen heterocyclic (N-heterocyclic) compounds are extensively present in natural products and active drug molecules. However, their synthesis typically requires the use of noble metal catalysts and harsh conditions. In this study, we report a novel approach using coffee charcoal as a green catalyst for the mildly mechanically driven oxidative dehydrogenation of N-heterocyclic compounds. A one-step strategy was employed to construct a microporous coffee charcoal catalyst with C defects, in-situ co-doping of multi-atoms (N, O), and abundant modification of functional groups (–OH and –COOH). Under room temperature and with H2O as solvent, the coffee charcoal catalyst demonstrates a high yield of approximately 94 % and allows for gram-scale reactions with H2O being the only by-product. Moreover, the catalyst exhibits excellent reusability, maintaining its activity for over 13 cycles. Results indicate that the defects and atom doping can enhance the adsorption of O2, which is then activated to singlet oxygen (1O2) through the conversion of –OH functional groups on the catalyst’s surface. The singlet oxygen (1O2) can strengthen the oxidative dehydrogenation of N-heterocyclic compounds. Furthermore, the mechanically driven technique both activates the reaction interface and supplies the necessary reactive energy, thus providing a comprehensive explanation for the mild reaction conditions observed. In conclusion, our research proposes a sustainable and environmentally friendly method for the oxidative dehydrogenation of N-heterocyclic compounds, which can drive crucial reactions with significant relevance to sustainability.

CrOx–SiO2 Catalysts in Nonoxidative Propane Dehydrogenation: Effect of Adding Cerium Dioxide

CrOx–SiO2 Catalysts in Nonoxidative Propane Dehydrogenation: Effect of Adding Cerium Dioxide

Recent Advances in Metal−Zeolite Catalysts for Direct Propane Dehydrogenation

Recent Advances in Metal−Zeolite Catalysts for Direct Propane Dehydrogenation

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.