Catalysts For Dehydrogenation Research Articles

Efficient catalytic hydrogen generation from formic acid dehydrogenation on ultrafine PdAu nanoparticles supported on modified carbon derived from rice straw

Formic acid (FA) dehydrogenation at ambient conditions is a promising route for hydrogen (H2) generation but still suffers from low activity and selectivity. Here, potassium hydroxide (KOH) and 3-aminopropyl triethoxysilane (APTES) modified porous carbon derived from the pyrolysis of rice straw (RSNPC) offers an effective support to promote the formation of ultrafine PdAu nanoparticles (NPs). Benefiting from the small sizes of PdAu NPs, the Pd0.7Au0.3/RSNPC catalyst exhibits excellent catalytic performance for FA dehydrogenation reaction with a high turnover frequency (TOF) of 6794.3 mol H2 mol catalyst−1 h−1 at ambient conditions, outperforming most of reported catalysts for FA dehydrogenation under similar conditions.

Supported silver and copper catalysts in the oxidative dehydrogenation of methanol to formaldehyde: a comparative study under industrially relevant conditions

Supported coinage-metal catalysts were prepared by strong electrostatic adsorption and used to assess the performance of silver and copper in the oxidative dehydrogenation of methanol to formaldehyde.

Mesoporous sol-gel silica supported vanadium oxide as effective catalysts in oxidative dehydrogenation of propane to propylene.

Vanadium oxide incorporated mesoporous silica (V-m-SiO2) were designed and synthesized using a surfactant-modified sol-gel method. Detailed characterization shows that monomeric [VO4] sites containing one terminal V[double bond, length as m-dash]O bond and three V-O-support bonds are dominated until atomic ratio of vanadium to silicon approaches to 5%. It is also confirmed that such V-m-SiO2 catalyst contains high proportion of vanadium oxide species interacting strongly with silica. Compared to vanadium oxide supported mesoporous silica (V/m-SiO2) prepared using a traditional impregnation method, present V-m-SiO2 catalyst exhibits more superior ability to catalyze oxidative dehydrogenation of propane to propylene. By correlation with structural data, superior catalytic performance of present V-m-SiO2 catalyst can be reasonably attributed, in part, to its favorable geometric and electronic properties rendered by the unique preparation method.

The promoting effect of boron oxide on the FeOx/Si3N4 catalyst for oxidative dehydrogenation of ethylbenzene

Stronger interaction created by B2O3 modification mitigates the oxygen reactivity of FeOx, promoting styrene selectivity in the oxidative dehydrogenation of ethylbenzene.

Development and mechanistic investigation of the dehydrogenation of alcohols with an iron(III) salen catalyst.

The iron(III) salen complex (R,R)-N,N'-bis(salicylidene)-1,2-cyclohexanediamineiron(III) chloride has been developed as a catalyst for the acceptorless dehydrogenation of alcohols. The complex catalyzes the direct synthesis of imines in good yields from different primary alcohols and amines with the liberation of hydrogen gas. The mechanism has been investigated experimentally with labelled substrates and theoretically with density functional theory calculations. In contrast to the corresponding manganese(III) salen-catalyzed dehydrogenation, it has not been possible to identify a homogeneous catalytic pathway with the iron complex. Instead, poisoning experiments with trimethylphosphine and mercury indicated that the catalytically active species are heterogeneous small iron particles.

A ligand design strategy to enhance catalyst stability for efficient formic acid dehydrogenation.

New Ir complexes bearing N-(methylsulfonyl)-2-pyridinecarboxamide (C1) and N-(phenylsulfonyl)-2-pyridinecarboxamide (C2) were employed as catalysts for aqueous formic acid dehydrogenation (FADH). The ligands were designed to maintain the picolinamide skeleton and introduce strong sigma sulfonamide moieties. C1 and C2 exhibited good stability towards air and concentrated formic acid (FA). During 20 continuous cycles, C1 and C2 could achieve the complete conversion of FA with TONs of 172 916 and 172 187, respectively. C1 achieved a high TOF of 19 500 h-1 at 90 °C and an air-stable Ir-H species was observed by 1H NMR spectroscopy.

Recent progress in porous catalysts for dehydrogenation of ammonia borane

The recent progress in porous materials applied as catalysts in AB solvolysis is investigated in this review. The major challenges and the future development directions for advanced porous catalysts for efficient AB solvolysis are put forward.

Self-crosslinked N-doped carbon dot supported Pd as an efficient catalyst for dehydrogenation of formic acid at room temperature

The optimized Pd/CDs-III catalyst shows 100% FA dehydrogenation within 21 min, with a TOF value of 256 h−1 at 298 K. This work provides a powerful guidance for the rational design of active catalysts for dehydrogenation of FA.

Photocatalytic treatment of Cr(VI) with ZrO2 and application of by-products as ethane dehydrogenation catalyst

Photocatalytic treatment of Cr(VI) with ZrO2 and application of by-products as ethane dehydrogenation catalyst

Multiscale modeling reveals aluminum nitride as an efficient propane dehydrogenation catalyst

First-principles-based microkinetic modeling simulations suggest AlN for light alkane dehydrogenation to olefins.

In situ observation of the on-surface thermal dehydrogenation of n-octane on Pt(111).

The catalytic dehydrogenation of alkanes constitutes a key step for the industrial conversion of these inert sp3-bonded carbon chains into other valuable unsaturated chemicals. To this end, platinum-based materials are among the most widely used catalysts. In this work, we characterize the thermal dehydrogenation of n-octane (n-C8H18) on Pt(111) under ultra-high vacuum using synchrotron-radiation X-ray photoelectron spectroscopy, temperature-programmed desorption and scanning tunneling microscopy, combined with ab initio calculations. At low activation temperatures, two different dehydrogenation stages are observed. At 330 K, n-C8H18 effectively undergoes a 100% regioselective single C-H bond cleavage at one methyl end. At 600 K, the chemisorbed molecules undergo a double dehydrogenation, yielding double bonds in their carbon skeletons. Diffusion of the dehydrogenated species leads to the formation of carbon molecular clusters, which represents the first step towards poisoning of the catalyst. Our results reveal the chemical mechanisms behind the first stages of alkane dehydrogenation on a platinum model surface at the atomic scale, paving the way for designing more efficient dehydrogenation catalysts.

Implications of Ga promotion and metal-oxide interface from tailored PtGa propane dehydrogenation catalysts supported on carbon.

Propane Dehydrogenation is a key technology, where Pt-based catalysts have widely been investigated in industry and academia, with development exploring the use of promoters (Sn, Zn, Ga, etc.) and additives (Na, K, Ca, Si, etc.) towards improved catalytic performances. Recent studies have focused on the role of Ga promotion: while computations suggest that Ga plays a key role in enhancing catalytic selectivity and stability of PtGa catalysts through Pt-site isolation as well as morphological changes, experimental evidence are lacking because of the use of oxide supports that prevent more detailed investigation. Here, we develop a methodology to generate Pt and PtGa nanoparticles with tailored interfaces on carbon supports by combining surface organometallic chemistry (SOMC) and specific thermolytic molecular precursors containing or not siloxide ligands. This approach enables the preparation of supported nanoparticles, exhibiting or not an oxide interface, suitable for state-of-the art electron microscopy and XANES characterization. We show that the introduction of Ga enables the formation of homogenously alloyed, amorphous PtGa nanoparticles, in sharp contrast to highly crystalline monometallic Pt nanoparticles. Furthermore, the presence of an oxide interface is shown to stabilize the formation of small particles, at the expense of propene selectivity loss (formation of cracking side-products, methane/ethene), explaining the use of additives such as Na, K and Ca in industrial catalysts.

Direct dehydrogenation of propane over Co@silicalite-1 zeolite: Steaming-induced restructuring of Co2+ active sites

The chemical state of the Co-relevant active site determines the catalytic performance of the Co-containing zeolite catalysts in non-oxidative propane dehydrogenation (PDH) reaction. Herein, we demonstrate that the moderate steaming pre-treatment is an available strategy to enhance catalytic activity of silicalite-1 zeolite-supported Co catalyst through tuning the Co state. The steaming-treated Co@S-1-steam catalyst exhibits sevenfold increased specific reaction rate (0.44 s−1) than the untreated Co@S-1 catalyst and maintains 95 % propylene selectivity in the PDH reaction at 590 °C. By comprehensive characterizations on the structural properties of the catalysts, multiple roles of steaming treatment are discovered. Steaming treatment can induce the reductive restructuring of the Co catalytic sites in zeolite micropores to form tetrahedral Co2+ species with enhanced dispersion and unsaturation degree, and significantly accelerate the selective activation of propane CH bonds. Furthermore, it also reduces the surface acidity and consequently promotes the desorption of propylene intermediates for enhancing the catalytic reaction rate and anti-coke stability.

Experimental and theoretical investigations into propane dehydrogenation over MIL-101(Cr/Al) derived catalysts

Propane dehydrogenation is commonly operated at temperatures exceeding 600 °C due to thermodynamic requirements. However, high temperature accelerates the deactivation of catalysts because of the coke deposition. Therefore, it is quite necessary to develop catalysts with high catalytic activity and improved anti-coking ability. To this end, an Al-doped Cr2O3 catalyst derived from MIL-101(Cr/Al) is prepared in this work. The preparation conditions, including the carbonization temperature of MIL-101 and the proportion of Cr/Al, are optimized via experimental studies. Meanwhile, the adsorption and dehydrogenation behaviors of propane on the catalyst are investigated using Density Functional Theory (DFT) methods. Findings indicate that the optimum carbonization temperature and Cr/Al proportion are 900 °C and 6:4, respectively. Under the reaction condition of P = 0.1 MPa, T = 580 °C and GHSV = 800 h−1, the propane conversion and propylene selectivity on the Cr6/Al4 catalyst are 19.5% and 92.0%, respectively. The activity stability of the Al-doped Cr2O3 is elongated significantly due to the lower desorption energy of propene and higher energy barrier for the coke formation on the catalyst. In sum, the present work completed via experiments and DFT calculations will lead to a better understanding of the Al-doped Cr2O3 catalyst and guide the rational design of anti-coking catalysts for propane dehydrogenation.

Highly efficient hydrogen evolution from formic acid using B, N co-doped carbon-supported Pd nanoparticles

A facile novel B, N co-doped carbon was fabricated by high-temperature pyrolysis of a mixture of ethylenediamine tetraacetic acid disodium salt and boric acid, on which Pd nanoparticles were loaded to synthesize highly efficient Pd/BNC catalyst for dehydrogenation of formic acid. The type and content of N are regulated by the doping of B elements in carbon materials. The high content of N and B doping provides more anchor sites for Pd and strengthens the interaction between the support and Pd nanoparticles, thus forming highly dispersed Pd nanoparticles and regulating the electronic property of Pd. Therefore, the obtained Pd/BNC catalyst displayed enhanced performance (TOF = 2760 h−1) and a lower activation barrier (31.84 kJ/mol). Furthermore, the catalyst also exhibited wonderful cycling stability for hydrogen evolution from formic acid.

Preparation and Characterization of Sisal Fibre Carbon Catalyst for Propane Oxidative Dehydrogenation

Preparation and Characterization of Sisal Fibre Carbon Catalyst for Propane Oxidative Dehydrogenation

Re-dispersion of active Zn species on modified S-1 zeolite as an efficient catalyst for direct dehydrogenation of propane

Highly active and inexpensive catalysts for propane dehydrogenation (PDH) are required for largescale propylene production in industrial application. Compared to Pt- and Cr-based catalysts, Zn-based nanomaterial is a promising candidate due to its environmental friendliness and coking-resistant but remains a great challenge. In this study, we developed a novel multi-component structure consisting of low Pt and abundant active Zn species highly dispersed on Fe-doped S-1 zeolite as PDH catalyst. Specifically, Fe-doping in S-1 support provided anchoring sites for loading Zn species with uniform distribution. Moreover, the very small amount of Pt was applied as promoter, which is beneficial to achieve the re-dispersion of Zn species with the formation of Znδ+ and Zn2+ active sites. The resulting 0.05Pt5Zn1Fe@S-1 catalyst exhibited the outstanding performance (conversion of propane: 40%, selectivity of propylene: 85%, and yield of propylene: 31.39%) as well as satisfactory regeneration ability. This improvement can be ascribed to the synergistic coupling between Pt promoter and the highly dispersed Zn species on modified S-1 support. This study opens a new way to design efficient and stable dehydrogenation catalysts.

Zeolitic imidazolate framework-8 as an efficient and facile heterogeneous catalyst for the acceptorless alcohol dehydrogenation to carboxylates

Zeolitic imidazolate framework-8 (ZIF-8) is a representative Zn-based metal–organic framework (MOF) featuring high porosity, good stability, and large surface area. Owing to these fascinating properties, ZIF-8 exhibits promising potential in catalysis. With our continuous interest in catalyst development of alcohol-involving green transformations, we intended to exploit the capability of ZIF-8 in catalyzing the acceptorless dehydrogenation of alcohols to carboxylates. The preparation of ZIF-8 at room temperature possesses advantages such as environmental friendliness and easy operation. Subsequently, various techniques were adopted to characterize the structures, morphology, and chemical states of both fresh and reused catalysts. Notably, the catalyst displayed good reusability since it could be reused at least 5 times without considerable loss of catalytic activity. It was also perceived that KOH was an indispensable component of this catalytic process. More specifically, KOH not only worked as one of the starting materials but also provided the basic environment to promote this catalysis. Furthermore, the aldehyde was confirmed as a key intermediate for this catalytic process. Based on additional experiments and literature reports, we proposed [Zn–N] as the active sites and presented a plausible catalytic cycle.

Suppressing Deep Oxidation by Detached Nano-sized Boron Oxide in Oxidative Dehydrogenation of Propane Revealed by the Density Functional Theory Study

The remarkable reactivity and selectivity of boron-based catalysts in the oxidative dehydrogenation (ODH) of light alkanes offer a sustainable path for the efficient conversion of light alkanes to olefins, while the origin of their unique ability to suppress deep oxidation remains to be studied. Concerning the leaking of boron oxide under ODH conditions, here, the ability of detached nano-sized boron oxide to eliminate propoxyl radicals, which is crucial to the high selectivity of olefins, was evaluated by means of density functional theory calculations. The results show that the barrier to the reaction is about 24 kcal/mol, suggesting that the detached nano-sized boron oxide can capture the propoxyl radicals under ODHP conditions to suppress the deep oxidation. The chemical environment may impose moderate influence by modulating their oxophilicity, and the boron sites that bear fewer hydroxyl groups show stronger affinity for the propoxyl radicals. This suggests that the inner tri-coordinated boron sites are more reactive than the edge boron sites in the elimination of alkoxyl radicals in the ODH of light alkanes, which is opposite to their ability to activate atmospheric dioxygen. This study enriches our understanding on the specific nature of boron-containing catalysts in suppressing the deep oxidation of light alkanes in their ODH.

Deactivation origins and stability-enhancing strategies of Sn/SiO2 catalysts for ethane dehydrogenation

A low-cost and environment-friendly Sn/SiO2 catalyst, highly active and selective for ethane dehydrogenation, is an effective alternative for high-cost Pt and toxic CrOx-based catalysts. While the catalyst deactivates fast due to the loss and aggregation of Sn species. In order to solve the problem, complexation impregnation method and in-situ synthesis approach have been tried to enhance the stability of Sn-based catalyst. As for the former one, a relatively stable performance of 5Sn/SiO2 catalyst can be achieved due to depressed Sn loss and coke deposition, while there is still room for improvement. When the latter strategy is applied, 5Sn-MCM-41 catalyst demonstrates the optimal dehydrogenation performance, with 44.0% of ethane conversion and 98.8% of ethylene selectivity, and no obvious decreasing trend is observed in the progress of 18 h reaction due to the well dispersion and anchoring of Sn species on the framework of MCM-41.