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Long-chain α-olefins ( ≥ C10) are normally applied in detergents, lubricants, and oil field chemicals. Due to the abundance of palm oil, the derivatives derived from palm oil, such as oleic acid (OA), can be converted to long-chain olefins via oxidative dehydrogenation (ODH) over a series of vanadium oxides (VxOy) incorporated with KIT-6 (nV-KIT-6 catalysts) synthesized by a direct hydrothermal method. Various ammonium metavanadate/tetraethyl orthosilicate molar ratios (V/Si) were evaluated over the range of 0.01–0.09. The results obtained from X-ray diffractometry, hydrogen-temperature programmed reduction, and X-ray photoelectron spectroscopy analyses revealed that the VxOy were mainly in a tetrahedral form when the V/Si molar ratios were lower than 0.05. Above this point, the formation of V2O5 crystallites was observed. The ODH of OA was performed in a continuous flow fixed-bed reactor under atmospheric pressure in the absence of solvent to avoid the interference of by-products generated from solvent oxidation. The results showed that the OA conversion and selectivity towards the desired products strongly depended on the V/Si molar ratio and the reaction temperature. The highest selectivity of olefins (alkenes + dienes) with carbon atoms in the range of C7–17 was 44%. Moreover, the selectivity to aromatics at 24% was observed at a 76% OA conversion level when the ODH was activated using the 0.05 V-KIT-6 catalyst under a 1/1 (v/v) oxygen/nitrogen gas mixture at a flow rate of 100 mL min−1 at 450 °C. Although the high selectivity towards alkenes was promoted by a higher dispersion of VxOy species on the catalyst, overdose of V/Si molar ratios produced more oxygenate compounds. The reaction mechanism for the ODH of OA was likely to be decarboxylation and decarbonylation followed by dehydration. The 0.05 V-KIT-6 catalyst also exhibited reusability over two cycles.

Catalytic dehydrogenation of ethanol produces acetaldehyde, an important precursor for several value-added chemicals such as acetic acid and acetate esters. In this paper, we demonstrate that Zn-containing MFI zeolites are highly active and selective catalysts for this process. Furthermore, we show that their activity and selectivity depend on the chemical composition and preparation of the catalysts. The best catalyst comprises 5 wt% Zn on Silicalite-1 zeolite and results in 65.2% conversion and 94.5% selectivity towards acetaldehyde at 400 ℃. We relate the high selectivity to the absence of Brønsted acidic silanol groups, which suppresses the dehydration of ethanol into ethylene. Furthermore, while pure HZSM-5 and NaZSM-5 zeolites result in dehydration products, such as ethylene and diethyl ether, Zn on NaZSM-5 zeolite also results in acetaldehyde, which confirms that Zn is the active site. Finally, we compare different preparation procedures to show that several Zn-species may be active for the catalytic reaction.

Platinum group metal (PGM)-based catalysts are known to be highly active in the total combustion of lower hydrocarbons. However, through an alternative catalyst design reported in this paper by isolating PGM-based active sites in a tungsten phosphate matrix, we present a class of catalysts for selective oxidation of n-butane, propane, and propylene that do not contain Mo or V as redox-active elements. Two different catalyst concepts have been pursued. Concept A: isolating Ru-based active sites in a tungsten phosphate matrix coming upon as ReO3-type structure. Concept B: dilution of PGM-based active sites through the synthesis of X-ray amorphous Ru tungsten phosphates supported on SiO2. Using a high-throughput screening approach, model catalysts over a wide compositional range were evaluated for C3 and C4 partial oxidation. Bulk crystalline and supported XRD amorphous phases with similar Ru/W/P compositions showed comparable performance. Hence, for these materials, composition is more crucial than the degree of crystallinity. Further studies for optimization on second-generation supported systems revealed even better results. High selectivity for n-butane oxidation to maleic anhydride and propane oxidation to an acrolein/acrylic acid has been achieved.

Designing highly active and selective metal nanocatalysts for use in liquid chemical hydrides is highly attractive but remains a critical challenge. Herein, bimetallic NiPt nanoparticles (NPs) immobilized on lanthanum oxycarbonate (NiPt/La2O2CO3) have been facilely synthesized via an alkali-assisted reduction method. The introduction of NaOH is the key factor to the formation of the well-dispersed and ultrafine NiPt NPs (2.8 nm). The obtained Ni0.6Pt0.4/La2O2CO3 exhibits an extraordinarily high catalytic activity and 100% H2 selectivity for hydrous hydrazine dehydrogenation, providing a turnover frequency value (TOF) high up to 490 h-1 at 298 K. Additionally, the NiPt/La2O2CO3 prepared with NaOH demonstrates higher catalytic performance and lower activation energy than that of NiPt/La2O2CO3_N prepared without NaOH. Moreover, the NiPt/La2O2CO3 also shows an outstanding catalytic efficiency (TOF = 1200 h-1) for dehydrogenation of hydrazine borane at 298 K. The efficient catalytic performance may be attributed to the small size effect, the strong metal-support interaction, and the NaOH promotion effect. This alkali-assisted reduction method provides a new perspective for preparing of highly efficient catalysts in clean energy application.

A redox process combining propane dehydrogenation (PDH) with selective hydrogen combustion (SHC) is proposed, modeled, simulated, and optimized. In this process, PDH and SHC catalysts are physically mixed in a fixed-bed reactor, so that the two reactions proceed simultaneously. The redox process can be up to 177.0% higher in propylene yield than the conventional process where only PDH catalysts are packed in the reactor. The reason is twofold: firstly, SHC reaction consumes hydrogen and then shifts PDH reaction equilibrium towards propylene; secondly, SHC reaction provides much heat to drive the highly endothermic PDH reaction. Considering propylene yield, operating time, and other factors, the preferable operating conditions for the redox process are a feed temperature of 973 K, a feed pressure of 1 bar, and a mole ratio of H2 to C3H8 of 0.15, and the optimal mass fraction of PDH catalyst is 0.5. This work should provide some useful guidance for the development of redox processes for propane dehydrogenation.

This work aims to evaluate the dynamic performance of a highly selective Ni-based surface during the oxidative dehydrogenation of ethane (ODH-C2). The catalyst comprises an in-house bimetallic mixed-oxide formulation with a Ni/Sn atomic ratio of 10. To corroborate its proper synthesis, it is characterized by TGA, AES, XRD, physisorption of N2 and TEM. The catalytic evaluation of the mixed oxide under dynamic conditions allows the proposition of a redox surface mechanism whose reliability is evaluated through a rigorous analysis, which is based on the development of a kinetic model and a robust experimentation program using a fully-automated micro-reaction unit and registering in-situ surface temperatures and continuous inline monitoring of oxygen and carbon dioxide. Experiments are carried out using a mixture of ethane or ethylene, oxygen and nitrogen as feedstock, at temperatures from 360 to 480 °C, total pressures from 100 to 500 kPa, and space-time values from 8.1 to 133.1 kgcat s molC2H6−1. Oxygen conversion ranges from 5% to 100% while the one for ethane varies from 5% to 60%. Besides, the selectivity and yield to ethylene vary from 30% to 90% and from 2% to 40%, respectively. The suitability of the redox mechanism is here assessed by evaluating statistical and phenomenological foundations, including Boudart’s criteria. Kinetic parameters, estimated by non-linear regression and using the reparametrized form of the Arrhenius and van’t Hoff equations, are phenomenologically well founded, such that changes of entropy and enthalpy of adsorption correctly describe the loss of mobility due to adsorption and the exothermic nature of the adsorption processes. Ethylene formation is the reaction demanding the lowest activation energy (Ea1 = 61.94 kJ mol−1), while the total oxidation of ethane is the path requiring the largest activation energy (Ea2 = 132.6 kJ mol−1). Concerning the adsorption enthalpy, ethylene exhibits the largest value ( − Δ H C 2 H 4 ° = 123.39 kJ mol−1), while carbon dioxide presents the lowest one ( − Δ H C O 2 ° = 42.00 kJ mol−1). Additional findings can be summarized as follows: activity and selectivity are recovered after the dynamic operation under oxidative conditions of the catalytic surface; carbon dioxide is identified as the only no desired byproduct; and hydroxyl surface species lead to the formation of water which affects the selectivity to ethylene, as well as the reaction rates. These findings are of interest for future studies directed at elucidating the performance of the Ni-based catalyst at larger scales, paving the way for the efficient design of the industrial reactor for the ODH-C2.

Nickel-based catalysts (40 wt% Ni) with commercial silicon-aluminum oxides as supports were prepared. The variation of the silica amount (10%, 20% and 40%) was studied. These catalytic formulations were characterized by N2 adsorption, SEM/EDX, HR-TEM, XRD, LRS and XPS, and tested in the oxidative dehydrogenation of ethane (ODHE) to produce ethylene. Besides, they were compared with a nickel-based silica-supported catalyst (NiO/SiO2). The effect of the proportion of silica in the supports on the generated Ni species, and consequently on the respective catalytic performances, was investigated. The results showed that, despite of the same NiO loading in all catalysts, different NiO-support interactions and surface amounts of non-selective oxygen species were obtained. These features had an impact on the catalytic behavior of each formulation. Remarkably, while ethylene selectivity was high and almost the same, ethane conversion increased with the silica amount in the supports. On the other hand, as expected, pure silica as a support resulted in high conversion but markedly low selectivity, favoring the total ethane oxidation to carbon dioxide. This work demonstrates that it is possible to increment the alkane conversion without sacrificing the alkene selectivity by tuning the active species properties through the increase of the amount of silica in the supports.

A systematic study on the use of noble metals (Pd, Pt, Au) supported on titanate nanotubes (NT-Ti) for selectively producing BTX and p-cymene from waste tire pyrolysis is provided here. All the materials were characterized for chemical, textural and structural properties using a range of analytical techniques. The M/NT-Ti (M: Pd, Pt, or Au) catalysts exhibit low nanoparticle sizes (1.8 Pt ≈ Au > support > non-catalyst. The Py-GC/MS suggest that the catalysts participate in the secondary reactions of dealkylation, dehydrogenation, isomerization, aromatization, and cyclization leading to a higher formation of BTX than the uncatalyzed reaction. Finally, a comprehensive reaction pathway describing the catalytic pyrolysis of WT over Pd/NT-Ti was proposed by studying the catalytic pyrolysis of individual polymers constituting the waste tires, and D, L -Limonene.

For the first time, the present work shows a combined theoretical and experimental analysis of the preferred adsorption sites for both methanol and methoxy species over Cu, Pt, and bimetallic Cu-Pt clusters - up to 5 atoms in size - supported on CeO2(111) as model systems. DFT+U calculations compared to methanol adsorption experiments followed by DRIFT spectroscopy over Cu, Pt, and bimetallic Cu-Pt nanoparticles supported over CeO2 octahedra, exposing only {111} crystal planes. From our DFT+U calculations, we found that methanol adsorption over the CuPt/CeO2(111) system is slightly favored, compared to the pristine CeO2(111) surface. Similarly, methoxy species formed through methanol dehydrogenation (CH3O- + H+) adsorb preferably over the metallic clusters, compared to the pristine oxide surface. This promotion is explained by the higher coordination of the methoxy species over the cluster, especially for those containing a higher amount of Cu atoms. This results highlights the oxidized Cu sites' role in the catalytic process, followed by the surface cerium atoms reduction of the support. The interaction of methanol with the substrate oxygen weakens the O-H bond, which results in a reduction in the energy barrier when the reaction occurs on the surface and interface, compared when this occurs exclusively on the metal cluster. However, after this step, the potential energy surface's depth suggests that methoxy species prefer to be adsorbed over the metal clusters. Experimentally, methanol was adsorbed over Cu, Pt, and bimetallic Cu-Pt nanoparticles supported over CeO2 {111}-octahedral particles. Through in-situ DRIFTS, bands related to adsorbed methanol and methoxy species were identified. A blue shift in all the bands was observed, related to metals’ influence in adsorbed species' vibrational mode. In the experimental spectra, new contributions in Cu-containing catalysts appeared, which were identified as adsorbed species over the metallic cluster and the interface, rationalized by calculated spectra.

A series of bifunctional ZnCe@SBA-15 catalysts with different Zn/Ce ratios were prepared by a solid-state grinding strategy and used in the conversion of ethanol to 1,3-butadiene (ETB). For the supported metal oxides, ZnO serves as the active sites for the dehydrogenation of ethanol, and CeO2 promotes the aldol-condensation reaction. Based on the results of Py-FTIR and NH3-TPD, it suggests that the yield of 1,3-butadiene is positively correlated with the number of weak Lewis acid sites on the catalyst surface, given their benefit for aldol-condensation reactions. The catalyst with an optimal Zn/Ce ratio of about 1:5 has the highest concentration of weak Lewis acid. Coupling with the ZnO sites, it contributes to a 98.4% conversion of ethanol and a 45.2% selective of 1,3-butadiene under relatively mild reaction conditions (375 °C, 101.325 kPa, and 0.54 h−1).

With the rapid development of modern industry, high-grade paving asphalt is massively required to meet the demands for modern transportation. As one of additives, natural asphalt is indispensable since it can improve the performance of paving asphalt in all aspects. However, the application of non-renewable natural asphalt is increasingly restricted by its limited reserves. It is imperative to find alternative approaches to produce high-grade paving asphalt. Fluid catalytic cracking (FCC) slurry oil is an ideal soft component for producing paving asphalt due to its high content of aromatics and resins. However, its bad ageing resistance limits its application to only low-grade paving asphalt. In the present work, a novel approach for producing high-grade paving asphalt was investigated using chemically modified FCC slurry oil and deoiled asphalt (DOA). The FT-IR and NMR results showed that dehydrogenation and condensation reaction occurred during the ageing process. From a series of aliphatic alcohols and aldehydes, propanal was selected as a proper modifier to improve the ageing resistance of FCC slurry oil. The propanal-modified slurry oil possessed more substituted aromatic units and less aromatic hydrogen atoms than other modified slurry oils, thus showing better ageing resistance. With the increase of length of aliphatic chains in modifier, the modified slurry oil contained more and longer alkyl substituent group on aromatics. Compared with the cross-linked oil (slurry oil modified by cross-linking agent), modified slurry oil possessed similar ageing resistance but higher flowing ability. Also, the effect of operation conditions on the kinematic viscosity of modified slurry oil were investigated. Blended with modified slurry oil, the penetration ratio of asphalt product increased from 53.7 to 66.2, which met the standard of 70# paving asphalt. Both the microscopic observations and FT-IR results indicated that modification process effectively reduced the oxidation degree of asphalt product, thus increasing the ageing resistance. Consequently, with aid of this process, high-grade paving asphalt was readily produced from low value oil from downstream products of refinery, instead of the depleting natural asphalt.

Formic acid (FA), which can be produced via CO2 reduction and biomass conversion, has received extensive interest as a convenient and safe hydrogen carrier due to its wide range of sources, renewable, high hydrogen content (4.4 wt%), and convenient storage/transportation. Designing highly efficient catalysts is the main challenge to realize the hydrogen production from FA. In this work, well-dispersed and electron-rich PdIr alloy nanoparticles with a size of 1.8 nm are confined in amino-modified 3D mesoporous silica KIT-6 and applied as a highly efficient catalyst for robust hydrogen production from FA at ambient temperature. Small PdIr alloy nanoparticles confined by amino-modified KIT-6 (PdIr/KIT-6-NH2) lead to better catalytic activity compared to that of Pd/KIT-6-NH2 and PdIr confined by bare KIT-6, achieving a high turnover frequency (TOF) value of 3533 h−1 at ambient temperature (303 K), 100% H2 selectivity and conversion toward the dehydrogenation of FA, which is comparable to the best heterogeneous catalysts ever reported. The high catalytic activity of PdIr/KIT-6-NH2 can be attributed to the synergistic effect between Pd and Ir, strong interaction between PdIr and KIT-6-NH2, as well as the amino-groups of KIT-6-NH2 which can act as a proton scavenger to promote the breaking of O-H bond of formic acid.

RM3 compounds (R = rare earth metals, M = transition metals) have rarely been studied for gaseous hydrogen storage applications because of unfavorable thermodynamics. In this work, the hydrogen storage properties of a single-phase YFe3 alloy were improved by non-stoichiometric composition and alloying with Sc and Zr. Only the Y1.1–yScyFe3 (y = 0.22, 0.33) alloys consist of a single rhombohedral phase. The Sc substitution for Y leads to the reduction in the unit cell volume of the YFe3 phase, and thus significantly increases the dehydriding equilibrium pressure and decreases the dehydrogenation temperature. The alloy Y0.77Sc0.33Fe3 delivers a decomposition enthalpy change of 33.54 kJ/mol and a lowest dehydrogenation temperature of 135 °C, in comparison with 38.99 kJ/mol and 165 °C for the alloy Y1.1Fe3. The Zr substitution causes a similar thermodynamic destabilization effect, but the composition and microstructure of Y–Zr–Fe alloys need to be further optimized.

Porous carbon fibers catalysts have been prepared by electrospinning of Alcell lignin, a green carbon precursor, which could be obtained as by-product in wood-to-ethanol biorefineries. The addition of H3PO4, a well-known chemical activation agent, to the electrospinning lignin solutions, at different mass ratios and the use of different carbonization temperatures, between 500 and 1600 °C, were analyzed in order to obtain carbon fibers with a large variety of porosity and chemical surface properties. Isopropanol decomposition was used as a catalytic test. Phosphorus-containing carbon fibers showed acid character and high catalytic activity, achieving propylene selectivity of 100 % under inert atmosphere. However, the use of air atmosphere increases the isopropanol conversion but produces the formation of acetone, via oxidative dehydrogenation, at low temperatures (∼20 %). Ethanol and methanol decomposition were also evaluated in air stream for the most active phosphorus-containing carbon catalyst, showing improved alcohol conversions with minimal gasification of the carbon fibers. These results confirmed that phosphorus-containing carbon fibers prepared by electrospinning of lignin solutions were excellent catalysts for alcohol dehydration reactions.

Earth abundant metals are much less expensive, promising, valuable metals and could be served as catalysts for the borrowing hydrogen reaction, dehydrogenation and heterocycles synthesis, instead of noble metals. The uniformly dispersed zinc composites were designed, synthesized and carefully characterized by means of XPS, EDS, TEM and XRD. The resulting zinc composite showed good catalytic activity for the N-alkylation of amines with amines, ketones with alcohols in water under base-free conditions, while unsaturated carbonyl compounds could also be synthesized by tuning the reaction conditions. Importantly, it was the first time to realize the synthesis of 2-aryl-1H-benzo[d]imidazole derivatives by using this zinc composite under green conditions. Meanwhile, this zinc catalyst could be easily recovered and reused for at least five times.

The presence of oxygen vacancies and hydroxyl groups are both favorable for the methanol electrooxidation on Pt-based catalysts. Understanding and differentiating the enhancing mechanism between oxygen vacancies and hydroxyl groups for high activity of Pt catalysts in methanol oxidation reaction (MOR) is essential but still challenging. Herein, we developed two kinds of co-catalyst for Pt/CNTs, Pr6O11 is rich in oxygen vacancies but contains substantially no hydroxyl groups, while Pr(OH)3 possesses abundant hydroxyl groups without oxygen vacancies. After a sequence of designed experiments, it can be found that both oxygen vacancies and hydroxyl groups can improve the performance of Pt/CNTs electrocatalysts, but the enhancing mechanism and improving degree of oxygen vacancies and hydroxyl groups for the MOR are different. Since the oxygen vacancies are more conducive to increasing the intrinsic activity of the Pt catalyst, and the hydroxyl groups play a decisive role in dehydrogenation and deprotonation of methanol, the co-catalysts with both oxygen vacancies and hydroxyl groups mixed with Pt/CNTs have higher catalytic performance. Therefore, hydroxyl-rich Pr6O11·xH2O was prepared and used as MOR electrocatalyst after mixed with Pt/CNTs. Benefiting from the synergistic effect of oxygen vacancies and hydroxyl groups, the Pr6O11·xH2O/Pt/CNTs shows a high peak current density of 741 mA/mg, which is three times higher than that of Pt/CNTs. These new discoveries serve as a promising strategy for the rational design of MOR catalysts with low cost and high activity.

Structured catalysts have important advantages compared to powder formulations and they are required for processes intensification. In this work, three different ceramic structures: a cordierite monolith, an alumina foam and an alumina-silica paper were used as substrates for the deposition of a NiO-Al2O3 coating and tested in the oxidative dehydrogenation of ethane to produce ethylene. For comparison, a NiO-Al2O3 powder catalyst was also prepared. Nickel oxide species with different physicochemical features were obtained over each structure, evidenced by morphological (SEM-EDX) and physicochemical characterization (XRD, LRS and XPS). The best distributions of the catalytic coatings and NiO physicochemical properties were obtained when the monolith and the foam were used as substrates. These led to higher NiO-Al2O3 interactions and consequently to high ethylene selectivity values, 70–90 %, corresponding to the former an ethane conversion of 22 % and to the latter a 5 %. The distribution of the active phase on the ceramic paper was heterogeneous, with NiO agglomerations and poor NiO-support interaction thus achieving low olefin selectivity (∼ 30 %). The addition of a second element such as cerium was also studied in those structured catalysts with high selectivity, resulting in both cases in an increment of ethane conversion but a decrease in ethylene selectivity. This behavior was attributed to the generation of electrophilic oxygen species.

Electrocatalytic hydrogen evolution is an efficient and economical technology to address environmental contamination and energy crises, but the development of such a sustainable hydrogen production system with high-efficiency and energy-saving remains a great challenge. Here, we present a novel strategy to design a self-driven dual hydrogen production system for efficient hydrogen production based on highly dispersed Rh single atoms supported on oxygen-functionalized Ti3C2Ox MXene (Rh-SA/Ti3C2Ox) catalyst. The bifunctional Rh-SA/Ti3C2Ox catalyst exhibited remarkable catalytic activities towards both pH-universal hydrogen evolution reaction (HER) and hydrazine oxidation reaction (HzOR). Using Rh-SA/Ti3C2Ox as the electrode in the self-driven dual hydrogen production system by combing the Zn-H2 battery and overall hydrazine splitting units, an ultra-high H2 generation rate of 45.77 mmol h−1 can be achieved. Density functional theory calculations indicate that the atomically dispersed Rh single atoms can not only make the free energy of adsorbed H (ΔG*H) more thermoneutral for HER but also largely decrease the free-energy barrier of the dehydrogenation of adsorbed NHNH2 for HzOR.

12 figures, 2 tables.-- Supplementary information available.-- © 2023. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/, The catalytic performance of SWCNT was notably improved in the oxidative dehydrogenation of ethylbenzene (EB) to styrene (ST) upon a double-function purification in one step of the raw SWCNT. This consists of lowering the MeOx concentration and generating surface C=O groups after processing it in nitric acid at controlled conditions, while preserving the structure. The textural improvement was ascribed to the cutting of the tubes/bundles by oxidation and to MeOx removal itself (dilution effect). Both EB conversion and ST selectivity increased with a parallel lowering of the undesired COx selectivity. The conversion was interpreted by the enhancement of the intrinsic properties (i.e., more surface ketonic groups) but also to the higher load of SWCNT in the bed upon purification; both factors contribute to a higher number of active sites (C=O) in the bed for styrene formation. The most purified catalyst underperformed in conversion once the purification altered the SWCNT structure notably. Thus, preserving the structure is an important condition to achieve high conversion and yield. The better selectivity was explained in two ways; more styrene-forming sites (C=O) or less COx-forming sites (uncoated MeOx) in the bed, or both. The styrene yield per catalyst volume was improved by an average of ca. 240 % in comparison to the non-purified SWCNT. Deactivation is critical in maximizing the purification effect on the intrinsic and volumetric yields. In practical terms, the purification method proved to enhance the reaction; the selectivity towards the unwanted COx was significantly lowered with a gain towards styrene, achieving comparable selectivity values as in the conventional process, but operated at much lower temperature., This work was supported by the Netherlands Organization for Scientific Research (NWO), under the Vidi grant no. 10284 (www.nwo.nl/en/projects/10284), carried out at Groningen University and completed by I.M.C. at La Laguna University. J.H. Marsman and L. Falco are thanked for assisting in the commissioning of the gas analysis system. A.M. acknowledges the Spanish Ministry of Science and Innovation (RYC2018-024561-I) and to the regional government of Aragon (DGA E13_20R). Additional funding was received from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 823717 – ESTEEM3). E.G.B. thanks financial support from Gobierno de Aragón (Grupo Reconocido DGA T03_20R).

The hybrid material composed of palladium nanoparticles (PdNPs) functionalized with N-heterocyclic carbene ligands (NHCs) immobilized onto the surface of reduced graphene oxide (rGO) results in an efficient catalytic material towards hydrogenation and dehydrogenation of N-heterocycles. The rGO plays a dual role by acting as a carbocatalyst in acceptorless dehydrogenation of N-heterocycles and as a support for the palladium nanoparticles facilitating its interaction with molecular hydrogen turning this hybrid material into an effective hydrogenation catalyst. Hot filtration experiments support the heterogeneous nature of the process underlining the strong interaction of palladium nanoparticles with the graphene enabled by π-interactions of the ligand with the support. The mild conditions used in both transformations of this system without requiring any additives facilitates its potential application in hydrogen storage technologies in the form of liquid organic hydrogen carriers (LOHCs). At the same time, the hybrid material is a robust and efficient catalytic platform that can be recovered and reused up to eight runs in both transformations without significant deactivation. The use of a single solid catalysts that is recyclable in hydrogen conversion and reconversion through (de)hydrogenation of N-heterocycles paves the way for the development of efficient hydrogen storage materials., MICIU/AEI/FEDER (PID2021-126071OB-C22 and PID2021-122900NB-I00). Universitat Jaume I (UJI-B2018-23). Generalitat Valenciana (ACIF/2019/100). RYC2019-026693-I/AEI/10.13,039/501100011033.

In recent years, several methods for the direct desaturation of aliphatic compounds have been developed, facilitated by the unique combination of photoredox and transition-metal catalysis. Hereby, alkenes with high functionalization potential can be prepared in a straightforward fashion. We adapted a previously reported system involving tetrabutylammonium decatungstate (TBADT) as hydrogen atom transfer (HAT) agent and a cobaloxime co-catalyst for dihydrogen evolution for the dehydrogenative preparation of linear enamides and enecarbamates from saturated precursors. The substrate scope includes several natural products and drug derivatives. The reaction does not require noble metal catalysts, exhibits short reaction times compared to previous methods and is suitable for the late-stage functionalization of drug derivatives.

One-pot methodologies for the synthesis of copper supported in mesoporous silica was developed. Parameters such as pH, time, and temperature of aging interfered in the loading of Cu impregnated. The Cu loadings affected both the textural properties of the silica support and the Cu nanoparticles. As the Cu loading increases, the catalyst showed more reduced Cu nanoparticles with a higher Cu-Cu coordination number (NCu-Cu). The bond length Cu-Cu (RCu-Cu) also correlates linearly with the NCu-Cu and appears to be dependent on the particle size and not affected by electronic parameters. It was possible to identify that the RCu-Cu parameter correlated linearly with the activity per site of Cu.

Although the oxidative dehydrogenation of propane with CO2 (CO2-ODP) is a sustainable route for producing propylene with the tandem conversion of CO2 to the value-added CO, its industrialization is...

The scandocene alkyl complex (C5Me5)2ScCH2SiMe3 was found to be an efficient catalyst for the dehydrocoupling of the non-cyclic boranes, dicyclohexylborane and thexylborane, with amines under mild conditions. The reactions afforded the corresponding aminoboranes in high yields with good functional group tolerance. The stoichiometric reaction of scandium alkyl with amine led to the isolation of a scandium amide complex, which was shown to be an active species during the catalysis. Although a borane-coordinated scandium hydride was also obtained from the stoichiometric experiment, it was not involved in the catalytic cycle. In addition, kinetic studies provided insight into this intermolecular dehydrogenation reaction.

Boron nitride (BN) as an emerging and revolutionary metal-free catalyst has demonstrated great potential in various oxidative dehydrogenation reactions. However, traditional BN sheets always presen...

This study examined the role of the support material on the coupling of 1,4-butanediol (BDO) dehydrogenation and nitrobenzene (NB) hydrogenation over copper-based catalysts. The catalysts, 10Cu/MgO (10CM), 10Cu/Al2O3 (10CA), 10Cu/MgO-Al2O3 (10CMA), and 10Cu/SiO2 (10CS), were prepared using the impregnation method. The coupling reaction results conducted at 250 °C were compared with those of the individual reactions. The individual BDO dehydrogenation to γ-butyrolactone (GBL) conversion (99%) and hydrogenation of NB to aniline (AN) conversion (85 %) were high over 10CS. In contrast, 10CA produced tetrahydrofuran (THF) as a major product from BDO. Interestingly, the coupling process over the 10CM catalyst produced the best performance in converting NB (65%) to AN (99%) and BDO (85%) to GBL (99%). The superior performance of Cu/MgO in coupling process catalyst is mainly due to the high hydrogen adsorption ability compared to the other catalysts under limited hydrogen environments, which helps retain the active hydrogen on the catalyst surface for a longer time. The characterization of the catalysts showed that a high basic nature and the optimal amount of active copper sites (Cu0/Cu1+) are responsible for the best performance of 10CM, followed by 10CS and 10CMA.

Cationic amidotitanocene complexes [Cp2 Ti(NPhAr)][B(C6 F5 )4 ] (Cp=η5 -C5 H5 ; Ar=phenyl (1 a), p-tolyl (1 b), p-anisyl (1 c)) were isolated. The bonding situation was studied by DFT (Density Functional Theory) using EDA-NOCV (Energy Decomposition Analysis with Natural Orbitals for Chemical Valence). The polar Ti-N bond in 1 a-c features an unusual inversion of σ and π bond strengths responsible for the balance between stability and reactivity in these coordinatively unsaturated species. In solution, 1 a-c undergo photolytic Ti-N cleavage to release Ti(III) species and aminyl radicals ⋅NPhAr. Reaction of 1 b with H3 BNHMe2 results in fast homolytic Ti-N cleavage to give [Cp2 Ti(H3 BNHMe2 )][B(C6 F5 )4 ] (3). 1 a-c are highly active precatalysts in olefin hydrogenation and silanes/amines cross-dehydrogenative coupling, whilst 3 efficiently catalyzes amine-borane dehydrogenation. The mechanism of olefin hydrogenation was studied by DFT and the cooperative H2 activation key step was disclosed using the Activation Strain Model (ASM).

Pincer ligated coordination complexes of base metals have shown remarkable catalytic activity for hydrogenation/dehydrogenation of CO2 . The recently reported MeN[CH2 CH2 (i Pr2 )]2 Co(I)PNP-pincer complex was shown to exhibit substantially higher catalytic activity in comparison to the corresponding catalyst, HN[CH2 CH2 (i Pr2 )]2 Co(I)PNP, bearing a secondary nitrogen center on the pincer ligand. Here, we computationally investigate the mechanisms for hydrogenation of CO2 to formate catalyzed by these two Co-PNP complexes to explain how such a small structural difference could have a sizable impact on their catalytic activity. Plausible hydrogenation routes were examined in details and our findings provide solid support for the experimental observations. Our results reveal that such trends in catalytic activity could be explained from the lower activation barrier for the hydride transfer step upon changing the pincer nitrogen center from secondary to tertiary.

Biowaste derived ethanol is an important feedstock for carbon neutral hydrogen production. It is liquid at atmospheric conditions, has a high hydrogen to carbon ratio, and it can be generated from ...

Copper nanoparticles on silica support are cheap and effective catalysts for dehydrogenation of n-butanol, a biomass-derived building block which is increasingly used. Ultrasonically assisted Cu catalysts are prepared, characterized, and tested for the conversion of n-butanol to n-butanal. The best performance in terms of overall conversion of n-butanol and selectivity to butanal was offered by ultrasound-prepared process of the Cu nanoparticles. In conventional wet impregnation method, Cu nanoparticles on the surface of support tend to aggregate in some sort of cubic aggregates with the size of 4–5 µm and because of this, the percentage of the centers of silica (on which intermolecular dehydration reactions occur) is higher compared to Cu metallic centers (that promotes the dehydrogenation reaction). The ultrasound reduction stage used in the preparation of catalysts provides a better coverage of the catalyst surface by Cu nanoparticles that have a more uniform dimension, which offers a greater selectivity to butanal (more than 95%) and a negligible selectivity to butene.

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 Brønsted) 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., Coordination geometry and Lewis acidity of Ga and Al (bulk and surface) sites in mixed oxide gallia–alumina nanoparticles is correlated with the performance in propane dehydrogenation.

Background In the traditional ethylbenzene dehydrogenation process, much superheated steam is needed to ensure the activity and stability of the catalyst, inevitably leading to high energy consumption. Methods A novel ethylbenzene dehydrogenation process based on a circulating fluidized bed (CFB) reactor was used for the ethylbenzene dehydrogenation reaction under a low steam-to-oil ratio. In this work, a series of Fe-Al-based catalysts were prepared by a sol-gel method and the effect of alumina content on the catalytic performance of Fe-Al-based catalyst for ethylbenzene dehydrogenation was investigated. Significant findings Among a series of Fe-Al-based catalysts, the FeAl40 catalyst (the Fe-Al-based catalyst with 40 wt. % alumina) had the highest dehydrogenation activity and suitable attrition resistance for the CFB reactor. Further investigation found that the adding alumina could inhabit the formation of KFe11O17, leading to poor stability. Interestingly, the high activity of the FeAl40 catalyst could be completely recovered through a reaction-regeneration operation. Compared with the conventional ethylbenzene dehydrogenation process, the CFB process benefits from high activity, low steam-to-oil ratio and no induction period. Consequently, the FeAl40 catalyst had high dehydrogenation activity (∼51 wt. % yield of styrene) and low preparation cost, showing an extraordinary potential for industrial application.

Here, we study the influence of the Cu modified (Zr + Ce)O2-Al2O3 systems composition and synthesis conditions on their catalytic properties in the ethanol conversion. First, we obtained varios ratios mixed Al-Zr supports at different synthesis temperatures using a sol-gel method. Then we modified the surface of the oxides by Cu, reduced in hydrogen flow. All obtained systems demonstrated а high alcohol conversion and selectivity to acetaldehyde. The surface area (SBET), the pore volume, and the pore distribution were measured by the nitrogen adsorption method. The structure of the samples have been investigated by XRD and XAS-spectroscopy. A correlation between the synthesis temperature and contents of mixed oxide support and textural properties were observed. The results show that Al-Zr mixed oxide support structure plays a crucial role in forming a Cu active site for ethanol dehydrogenation to acetaldehyde.

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...

Synthesis of surfactants based on linear alkylbenzenesulfonates is a complex multi-stage process that includes the following stages: alkanes dehydrogenation on Pt-containing catalyst, dienes hydrogenation on Ni-containing catalyst, HF-catalyzed alkylation of benzene with alkenes, and sulfonation of linear alkylbenzenes (LAB) with sulfur trioxide in a film reactor yielding alkylbenzene sulfonic acid (ABSA). When developing mathematical models of multi-stage processes it is necessary to consider the contingency of the apparatuses in the chemical-technological system. The design of the sulfonation reactor, as well as the feedstock composition and the dehydrogenation unit performance, i.e., the LAB flowrate to sulforator, significantly affects the ABSA synthesis efficiency. The studies were performed using the unsteady mathematical models of conjugated dehydrogenation and sulfonation processes. As a result, we determined the optimal design of the sulfonation reactor with number of tubes n = 40 and diameter d = 43 mm. We also outlined the preferred method for increasing the ABSA yield by switching to a double-reactor alkane dehydrogenation scheme with a flowrate of 100 m3/h for two dehydrogenation reactors. This increases yield of alkenes and LAB by 71 %wt.

Commercial pure γ-Al2O3 and SiO2 (1−30 wt.%) doped γ-Al2O3 were characterized as acid catalysts in ethanol conversion and used as supports for NiO and MoO3. Supported catalysts were prepared by incipient wetness impregnation. All catalytic materials were characterized by BET, XRD, FE-SEM microscopy, UV–vis and IR spectroscopies. Pure and silica-doped NiO/Al2O3 materials were used as precursors of metal catalysts for CO2 hydrogenation. Pure and silica-doped MoO3/Al2O3 materials were used as catalysts for ethanol oxidative dehydrogenation to acetaldehyde. These data show that the addition of silica in moderate amounts selectively influences a part of the alumina surface and strongly modifies the dispersing properties of alumina support. In particular, silica preferentially bonds over the strongest Lewis acid-base sites of γ-Al2O3, where also Ni2+ and molybdate species tend to interact. Being the SiO2-Al2O3 interaction stronger than the NiO-Al2O3 interaction and the MoO3-Al2O3 interaction, silica displaces nickel and molybdate species to less preferential sites where their interaction with exposed alumina is weaker. This results in more easily reducible Ni2+ species and larger Ni metal particles for silica doped Ni/Al2O3, and more monomeric and less polymeric molybdate species for silica doped MoO3/Al2O3.

Sulfur promoted nickel catalysts supported on MgAl2O4 and SiO2 were investigated for the dehydrogenation of propane. The catalysts were prepared by the impregnation method using ammonium sulfate as the sulfiding agent. The catalysts were evaluated in both the sulfated form, NiO/MgAl2O4-20 wt%SO4 and NiO/SiO2-20 wt%SO4, in addition to the reduced form, Ni/MgAl2O4-20 wt%SO4 and Ni/SiO2-20 wt%SO4, which contained the sulfided species. Physicochemical properties of the catalysts were characterised by XRD, BET, TEM, TGA, NH3-TPD, FTIR and TPR techniques to investigate the particle size, surface area, morphology, acidic properties and stability of the catalysts on both MgAl2O4 and SiO2 supports. Structural and textural characterization of the catalysts revealed that NiO/MgAl2O4-20 wt%SO4 and Ni/MgAl2O4-20 wt%SO4 displayed highly dispersed particles in comparison to the catalysts on the SiO2 support. H2-TPR analysis showed that the reducibility of the smaller particles on the MgAl2O4 support was hindered. In addition, the stronger metal-support interactions on MgAl2O4 enhanced the stability of the catalyst which enables increased activity and facilitated the desorption of olefins, leading to a high selectivity of above 70 % for propylene.

Sustainable production of aromatics, especially benzene, toluene and xylenes (BTX), is essential considering their broad applications and the current global transition away from crude oil utilization. Aromatization of lower olefins, particularly ethene and propene, offers great potential if they are derived from more circular alternative carbon feedstocks such as biomass and waste plastics. This work aims to identify the preferred olefin feed, ethene or propene, for BTX production in a fixed-bed reactor. A commercial H-ZSM-5 (Si/Al = 23) catalyst was used as a reference catalyst, as well as a Ga-ZSM-5 catalyst, prepared by Ga ion-exchange of the H-ZSM-5 catalyst. At 773 K, 1 bar, 45 vol % olefin, 6.75 h(-1), propene aromatization over the Ga-ZSM-5 catalyst exhibited higher BTX selectivity of 55 % and resulted in slower catalyst deactivation compared to ethene aromatization.

The value of catalytic dehydrogenation of aliphatics (CDA) in organic synthesis has remained largely underexplored. Known homogeneous CDA systems often require the use of sacrificial hydrogen acceptors (or oxidants), precious metal catalysts, and harsh reaction conditions, thus limiting most existing methods to dehydrogenation of non- or low-functionalized alkanes. Here we describe a visible-light-driven, dual-catalyst system consisting of inexpensive organophotoredox and base-metal catalysts for room-temperature, acceptorless-CDA (Al-CDA). Initiated by photoexited 2-chloroanthraquinone, the process involves H atom transfer (HAT) of aliphatics to form alkyl radicals, which then react with cobaloxime to produce olefins and H2. This operationally simple method enables direct dehydrogenation of readily available chemical feedstocks to diversely functionalized olefins. For example, we demonstrate, for the first time, the oxidant-free desaturation of thioethers and amides to alkenyl sulfides and enamides, respectively. Moreover, the system's exceptional site selectivity and functional group tolerance are illustrated by late-stage dehydrogenation and synthesis of 14 biologically relevant molecules and pharmaceutical ingredients. Mechanistic studies have revealed a dual HAT process and provided insights into the origin of reactivity and site selectivity.

In comparison to the traditional petroleum-based plastics, polylactic acid, the most popular biodegradable plastic, can be decomposed into carbon dioxide and water in the environment. However, the natural degradation of polylactic acid requires a substantial period of time and, more importantly, it is a carbon-emitting process. Therefore, it is highly desirable to develop a novel transformation process that can upcycle the plastic trash into value-added products, especially with high chemical selectivity. Here we demonstrate a one-pot catalytic method to convert polylactic acid into alanine by a simple ammonia solution treatment using a Ru/TiO2 catalyst. The process has a 77% yield of alanine at 140 °C, and an overall selectivity of 94% can be reached by recycling experiments. Importantly, no added hydrogen is used in this process. It has been verified that lactamide and ammonium lactate are the initial intermediates and that the dehydrogenation of ammonium lactate initiates the amination, while Ru nanoparticles are essential for the dehydrogenation/rehydrogenation and amination steps. The process demonstrated here could expand the application of polylactic acid waste and inspire new upcycling strategies for different plastic wastes.

The catalytic properties of modified synthetic (A, X, Y) and natural (MOR, Clp) zeolites have been studied in the reactions of oxidative dehydrogenation of butyl alcohols to corresponding carbonyl com-pounds. It has been established that bimetallic zeolite catalysts show higher activity in these reactions

The oxidative dehydrogenation of alicyclic diene hydrocarbons refers to scarcely studied heterogeneous catalytic reactions which proceed with the participation of oxygen. The dehydrogenation of methylcyclopentane is an endothermic reaction. To improve the reaction kinetics, this research was to develop a structured catalyst by conductive metals (Cu, Zn, Co, Cr) support which could hold an adherent catalytic layer. The active phase was impregnated onto these support metals and the developed catalyst was tested for the dehydrogenation of methylcyclopentane. The catalyst preparation involved three main key steps which were support oxidative reaction, loading of active particles on the catalyst surface, preparation of an active catalyst layer on the surface finally bringing the catalyst into the active phase. Different types of catalyst activation and deactivation mechanisms stability have been studied in this investigation. The advantage of this works, the oxidative dehydrogenation of methylcyclopentane is that it occurs at the expense of oxygen in the air. The zeolite structure study helped identify the effect of the combination of catalysts, and adsorption of metals on clinoptilolite and dispersion on the selectivity of the catalyst particles. Numerical values of the kinetic parameters were calculated