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Moharreri, Ehsan

Publications and source records attributed to Moharreri, Ehsan.

10 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Partial oxidation of methane to methanol on boron nitride at near critical acetonitrile

Abstract Direct catalytic conversion of methane to methanol with O 2 has been a fundamental challenge in unlocking abundant natural gas supplies. Metal-free methane conversion with 17% methanol yield based on the limiting reagent O 2 at 275 °C was achieved with near supercritical acetonitrile in the presence of boron nitride. Reaction temperature, catalyst loading, dwell time, methane–oxygen molar ratio, and solvent-oxygen molar ratios were identified as critical factors controlling methane activation and the methanol yield. Extension of the study to ethane (C2) showed moderate yields of methanol (3.6%) and ethanol (4.5%).

03 NATURAL GAS↗
DOE OSTI2021

Role of catalytic nitrile decomposition in tricopper complex mediated direct partial oxidation of methane to methanol

Synthetic homogeneous system known to date performing methane to methanol conversion using O 2 as terminal oxidant is unique and based on copper complex with piperazine-based ligand (Cu 3 L in Fig. 1) in a medium of acetonitrile. Prior work have shown that in order to achieve catalytic turnover, hydrogen peroxide is needed to regenerate the active site. We show in this paper that reaction solvent based on organic nitrile decompose concurrently with methane activation and that in the absence of either acetonitrile, Cu complex or hydrogen peroxide, the catalytic turnover does not happen. We show in this manuscript that the direct methane oxidation to methanol might have been mediated by catalytic Radziszewski oxidation between acetonitrile and H 2 O 2 . Additionally we have discovered that in the absence of methane, peroxide mediated acetonitrile decomposition also makes methanol via a background reaction which was hitherto unknown.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Trends in Solid Adsorbent Materials Development for CO 2 Capture

A review summarizing trends in materials development for CO 2 adsorption focusing on recent studies is given. Trends in computational investigations along with experimental findings are covered to find promising candidates in light of practical challenges imposed by process economics. Topics covered here include: introduction (climate change, CO 2 emissions mitigation, overview of classical computational CO 2 adsorption studies); CO 2 capture materials (C based materials [activated C {AC}, ordered porous C, C fiber, graphene], SiO 2 /Al 2 O 3 /zeolite [SiO 2 , Al 2 O 3 and nanoclays, zeolite], porous cryst. solids [metal-org. frameworks (MOF) {metal type and open metal sites, functionalized MOF, mol. sieves, MOF computational modeling, MOF databases}, zeolite imidazolate frameworks, covalent org. frameworks and polymers], metal oxides); and conclusions and future perspectives.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Energy–Geometry Dependency of Molecular Structures: A Multistep Machine Learning Approach

There is growing interest in estimating quantum observables while circumventing expensive computational overhead for facile in silico materials screening. Machine learning (ML) methods are implemented to perform such calculations in shorter times. In this paper, we introduce a multistep method based on machine learning algorithms to estimate total energy on the basis of spatial coordinates and charges for various chemical structures, including organic molecules, inorganic molecules, and ions. This method quickly calculates total energy with 0.76 au in root-mean-square error (RMSE) and 1.5% in mean absolute percent error (MAPE) when tested on a database of optimized and unoptimized structures. Using similar molecular representations, experimental thermochemical properties were estimated, with MAPE as low as 6% and RMSE of 8 cal/mol·K for heat capacity in a 10-fold cross-validation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Aerobic Self-Esterification of Alcohols Assisted by Mesoporous Manganese and Cobalt Oxide

Aerobic self-esterification of primary alcohols catalyzed by mesoporous metal oxides (manganese and cobalt oxides) is reported under base and solvent free conditions. For a range of aliphatic alcohols, up to 90 % conversions to esters was achieved. The catalytic reaction is likewise applicable to neat aldehydes as substrates with yields of up to 86 %. High pressure batch reaction for ethanol to ethyl acetate led to 22 % yield. Isotope labeling studies indicated decarboxylation on the catalyst surface. Mechanistic and kinetic experiments implicate oxygen rebound and α-carbon removal as intermediate steps. Finally, mesoporous cobalt oxide showed about 20 % higher catalytic activity compared to mesoporous manganese oxide.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Synthesis of Large Mesoporous–Macroporous and High Pore Volume, Mixed Crystallographic Phase Manganese Oxide, Mn 2 O 3 /Mn 3 O 4 Sponge

The controlled synthesis of mixed crystallographic phase Mn 2 O 3 /Mn 3 O 4 sponge material by varying heating rates and isothermal segments provides valuable information about the morphological and physical properties of the obtained sample. The well-characterized Mn 2 O 3 /Mn 3 O 4 sponge and applicability of difference in reactivity of H 2 and CO 2 desorbed during the synthesis provide new developments in the synthesis of metal oxide materials with unique morphological and surface properties. Here, we report the preparation of a Mn 2 O 3 /Mn 3 O 4 sponge using a metal nitrate salt, water, and Dextran, a biopolymer consisting of glucose monomers. The Mn 2 O 3 /Mn 3 O 4 sponge prepared at 1 °C·min –1 heating rate to 500 °C and held isothermally for 1 h consisted of large mesopores–macropores (25.5 nm, pore diameter) and a pore volume of 0.413 mL/g. Furthermore, the prepared Mn 2 O 3 /Mn 3 O 4 and 5 mol %–Fe-Mn 2 O 3 /Mn 3 O 4 sponges provide potential avenues in the development of solid-state catalyst materials for alcohol and amine oxidation reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Comprehensive Magnetic Study of Nanostructured Mesoporous Manganese Oxide Materials and Implications for Catalytic Behavior

Magnetic behavior of nanostructured mesoporous manganese oxide materials, designated UCT-1 and UCT-18, were studied using a combination of superconducting quantum interference device (SQUID) magnetometry and 55 Mn zero-field spin–echo nuclear magnetic resonance (NMR). Curie–Weiss fits to the magnetic susceptibility for the UCT-1 and UCT-18 samples calcined at 550 °C yielded paramagnetic moment values consistent with spin-only Mn 3+ ions in the α-Mn 2 O 3 phase ( S = 2, 4.90 μ B ). However, the magnetization and NMR results reported here clearly identify a small amount of the Mn 3 O 4 second phase (ferrimagnetic with T C ≈ 43 K) that does not appear in X-ray diffraction (XRD). We report the study resulted in the observation of fascinating magnetic behavior: (1) exchange bias, which occurs in cases where a ferromagnetic (or ferrimagnetic) phase forms a boundary with an antiferromagnetic phase and (2) a magnetic contribution attributed to uncompensated spins on the surfaces of the α-Mn 2 O 3 nanoparticles. The presence of Mn 3 O 4 and the interplay of Mn 3+ and Mn 2+ impact the catalytic properties.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Photocatalytic water splitting—The untamed dream: A review of recent advances

Here, photocatalytic water splitting using sunlight is a promising technology capable of providing high energy yield without pollutant byproducts. Herein, we review various aspects of this technology including chemical reactions, physiochemical conditions and photocatalyst types such as metal oxides, sulfides, nitrides, nanocomposites, and doped materials followed by recent advances in computational modeling of photoactive materials. As the best-known catalyst for photocatalytic hydrogen and oxygen evolution, TiO 2 is discussed in a separate section, along with its challenges such as the wide band gap, large overpotential for hydrogen evolution, and rapid recombination of produced electron-hole pairs. Various approaches are addressed to overcome these shortcomings, such as doping with different elements, heterojunction catalysts, noble metal deposition, and surface modification. Development of a photocatalytic corrosion resistant, visible light absorbing, defect-tuned material with small particle size is the key to complete the sunlight to hydrogen cycle efficiently. Computational studies have opened new avenues to understand and predict the electronic density of states and band structure of advanced materials and could pave the way for the rational design of efficient photocatalysts for water splitting. Future directions are focused on developing innovative junction architectures, novel synthesis methods and optimizing the existing active materials to enhance charge transfer, visible light absorption, reducing the gas evolution overpotential and maintaining chemical and physical stability

36 MATERIALS SCIENCE↗