Atmospheric Pressure H2 Research Articles

Ester hydrogenolysis via β-C-O bond cleavage catalysed by a phenanthroline-based PNNP-cobalt(I) complex.

A Co(I) catalyst bearing a phenanthroline-based PNNP ligand (2,9-bis((diphenylphosphanyl)methyl)-1,10-phenanthroline) exhibits long-range metal ligand cooperation behavior using a ligand backbone as a hydrogen reservoir and catalyses hydrogenolysis of benzyl benzoate derivatives via β-C-O cleavage with atmospheric pressure H2.

Revealing High-Temperature Reduction Dynamics of High-Entropy Alloy Nanoparticles via In Situ Transmission Electron Microscopy.

Understanding the behavior of high-entropy alloy (HEA) materials under hydrogen (H2) environment is of utmost importance for their promising applications in structural materials, catalysis, and energy-related reactions. Herein, the reduction behavior of oxidized FeCoNiCuPt HEA nanoparticles (NPs) in atmospheric pressure H2 environment was investigated by in situ gas-cell transmission electron microscopy (TEM). The reduction reaction front was maintained at the external surface of the oxide. During reduction, the oxide layer expanded and transformed into porous structures where oxidized Cu was fully reduced to Cu NPs while Fe, Co, and Ni remained in the oxidized form. In situ chemical analysis showed that the expansion of the oxide layer resulted from the outward diffusion flux of all transition metals (Fe, Co, Ni, Cu). Revealing the H2 reduction behavior of HEA NPs facilitates the development of advanced multicomponent alloys for applications targeting H2 formation and storage, catalytic hydrogenation, and corrosion removal.

Mild Hydrodeoxygenation of Phenols into Cycloalkanes under Ambient Hydrogen Pressure over a Ni/H‐Beta Catalyst

AbstractHydrodeoxygenation of phenols is an important process for producing six‐membered ring hydrocarbons from lignin. The reaction generally requires high temperatures (300 °C or higher) and high‐pressure H2 gas. In recent years, milder reactions at around 100 °C under atmospheric pressure H2 have been developed by using noble metal catalysts. On the other hand, the reaction with less expensive base metal catalysts still requires either of high temperatures or high‐pressure H2, or the both. Herein, we performed the reaction of various phenols over a Ni/H‐Beta catalyst in octane at 110 °C under atmospheric pressure H2 in a batch reactor to give the corresponding cyclohexanes in 96–33% yield. The reaction proceeds through formation of cyclohexene intermediates, which are eventually converted to cyclohexanes either directly or via transient arene intermediates.

Surface Modification of a Supported Pt Catalyst Using Ionic Liquids for Selective Hydrodeoxygenation of Phenols into Arenes under Mild Conditions.

The selective and efficient removal of oxygenated groups from lignin-derived phenols is a critical challenge to utilize lignin as a source for renewable aromatic chemicals. This report describes how surface modification of a zeolite-supported Pt catalyst using ionic liquids (ILs) remarkably increases selectivity for the hydrodeoxygenation (HDO) of phenols into arenes under mild reaction conditions using atmospheric pressure H2 . Unmodified Pt/H-ZSM-5 converts phenols into aliphatic species as the major products along with a slight amount of arenes (10 % selectivity). In contrast, the catalyst modified with an IL, 1-butyl-3-methylimidazolium triflate, keeps up to 76 % selectivity for arenes even at a nearly complete conversion of phenols. The IL on the surface of Pt catalyst may offer the adsorption of phenols in an edge-to-face manner onto the surface, thus accelerating the HDO without the ring hydrogenation.

Unexpected Pd/C-catalyzed room temperature and atmospheric pressure hydrogenation of 2-methylenecyclobutanones

Pd/C-catalyzed hydrogenation reaction of 2-methylenecyclobutanones (2-MCBones) occurs at their exocyclic CC sites regio-specifically to produce 2-substituted cyclobutanones, which are useful building blocks for the synthesis of drug and pesticide intermediates and are key intermediates in the total synthesis of many natural products. Surprisingly, atmospheric pressure H2 in balloon can be used as the cheap, clean and safe reductant and the reaction occurs smoothly at room temperature (25 °C). Quantitative calculation demonstrates that the release of the intramolecular ring strain caused by the combined effect of the four-membered ring and exocyclic CC bond in 2-MCBones provides additional dynamic driving forces for the reaction. The higher hydrogenation energy releasing of the exocyclic CC than CO was also found to be the causation for good regio-selectivity of the reaction. These new findings may broaden the understandings on the catalytic hydrogenation reactions of strained organic molecules.

Development of an Iridium-Based Catalyst for High-Pressure Evolution of Hydrogen from Formic Acid.

A highly efficient and recyclable Ir catalyst bearing a 4,7‐dihydroxy‐1,10‐phenanthroline ligand was developed for the evolution of high‐pressure H2 gas (>100 MPa), and a large amount of atmospheric pressure H2 gas (>120 L), over a long term (3.5 months). The reaction proceeds through the dehydrogenation of highly concentrated aqueous formic acid (FA, 40 vol %, 10 mol L−1) at 80 °C using 1 μmol of catalyst, and a turnover number (TON) of 5 000 000 was calculated. The Ir catalyst precipitated after the reaction owing to its pH‐dependent solubility in water, and 94 mol % was recovered by filtration. Thus, it can be treated and recycled like a heterogeneous catalyst. The catalyst was successfully recycled over 10 times for highpressure FA dehydrogenation at 22 MPa without any treatment or purification.

Multi‐fuel scaled‐down autothermal pure H2 generator: Design and proof of concept

This article presents experimental results of an autothermal scaled‐down system for H2 production. Pure atmospheric pressure H2, separated in situ by Pd–Ag membranes, is produced by steam reforming (SR) of methane, ethanol, or glycerol. Oxidizing the SR effluents in a separate compartment supplies the heat. The oxidation feed is axially distributed to avoid hotspots. The 1.3 L system, comprises 100 cm2 of membrane area, and generates H2 flow rate equivalent to 0.15 kW at an efficiency of ∼25%. This process leads to comparable performance when different fuels are used. A mathematical model, validated by the measurements, predicts that increasing the membrane area relative to the outer surface area will substantially increase the efficiency and power output. This design serves as proof of concept for on‐board pure H2 generators, with flexible fuel sources, and holds a great promise to reduce the need for special H2 transport and storage technologies for portable or stationary applications. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2112–2125, 2016

Intensification of shock-induced combustion by electric-discharge-excited oxygen molecules: numerical study

Mechanisms of combustion enhancement in a supersonic H2–O2 reactive flow behind an oblique shock wave front are investigated when vibrational and electronic states of O2 molecule are excited by an electric discharge. The analysis is carried out on the base of updated thermally nonequilibrium kinetic model for the H2–O2 mixture combustion. The presence of vibrationally and electronically excited O2 molecules in the discharge-activated oxygen flow allows to intensify the chain mechanism and to shorten significantly the induction zone length at shock-induced combustion. It makes possible, for example, to ignite the atmospheric pressure H2–O2 mixture at the distance shorter than 1 m behind the weak oblique shock wave at a small energy Es = 1.2 × 10–2 J · cm–3 input to O2 molecules. At higher pressure it is needed to put greater specific energy into the gas in order to ignite the mixture at appropriate distances. It is shown that excitation of O2 molecules by electric discharge is much more effective for accelerating the hydrogen–oxygen mixture combustion than mere heating the gas.

Atomic layer epitaxy on (001) GaAs: Real-time spectroscopy

Using reflectance-difference spectroscopy, we perform the first real-time spectroscopic investigation of the evolution of the (001) GaAs surface to cyclic and noncyclic exposures to atmospheric pressure H2, H2 and trimethylgallium, and H2 and AsH3 that simulate growth by atomic layer epitaxy. None of our observations are consistent with any previously proposed simple model. The results emphasize the necessity of real-time measurements for the analysis of complex surface reactions.

Arsenic dimers and multilayers on (001)GaAs surfaces in atmospheric pressure organometallic chemical vapor deposition

Arsenic dimers and multilayers are shown to exist on (001)GaAs surfaces under atmospheric pressure (AP) organometallic chemical vapor deposition (OMCVD) conditions. We obtained reflectance-difference spectra from surfaces in AP H2 that are equivalent to those obtained from the (2×4) and disordered-c(4×4) reconstructions prepared in ultrahigh vacuum by molecular beam epitaxy. Implications for models of OMCVD growth.