The Synergic Effects of Iron Carbides on Conversion of Syngas to Alkenes

Issues and challenges of Fischer-Tropsch synthesis catalysts

Depletion of oil and gas resources is a major concern for researchers and the global community. Researchers are trying to develop a way to overcome these issues using the Fischer-Tropsch synthesis (FTS) process. The FTS reaction converts a mixture of hydrogen and carbon monoxide gases into a liquid fuel. The reactions are performed in the reactor and in the presence of a catalyst. A series of catalysts, such as iron, cobalt, nickel, and ruthenium, have been used for the FTS process. In iron-based catalysts, the Fe5C phase is the active phase that produces C5+ hydrocarbons. At higher conversion rates, the presence of water in the products is a problem for cobalt catalysts because it can trigger catalyst deactivation mechanisms. Ni-based catalysts play key roles as base catalysts, promoters, and photothermal catalysts in FTS reactions to produce different useful hydrocarbons. Ruthenium catalysts offer not only high activity but also selectivity toward long-chain hydrocarbons. Moreover, depending on the Ru particle size and interaction with the oxide support, the catalyst properties can be tuned to enhance the catalytic activity during FTS. The detailed reaction pathways based on catalyst properties are explained in this article. This review article describes the issues and challenges associated with catalysts used for the FTS process.

Recent advances in bifunctional synthesis gas conversion to chemicals and fuels with a comparison to monofunctional processes

In order to meet the climate goals of the Paris Agreement and limit the potentially catastrophic consequences of climate change, we must move away from the use of fossil feedstocks for the production of chemicals and fuels. The conversion of synthesis gas (a mixture of hydrogen, carbon monoxide and/or carbon dioxide) can contribute to this. Several reactions allow to convert synthesis gas to oxygenates (such as methanol), olefins or waxes. In a consecutive step, these products can be further converted into chemicals, such as dimethyl ether, short olefins, or aromatics. Alternatively, fuels like gasoline, diesel, or kerosene can be produced. These two different steps can be combined using bifunctional catalysis for direct conversion of synthesis gas to chemicals and fuels. The synergistic effects of combining two different catalysts are discussed in terms of activity and selectivity and compared to processes based on consecutive reaction with single conversion steps. We found that bifunctional catalysis can be a strong tool for the highly selective production of dimethyl ether and gasoline with high octane numbers. In terms of selectivity bifunctional catalysis for short olefins or aromatics struggles to compete with processes consisting of single catalytic conversion steps.

Coordination-induced bond weakening in NiC3: An experimental and theoretical investigation

Mass-selected photoelectron velocity-map imaging spectroscopy in conjunction with the density functional theory calculations was employed to investigate the geometrical and chemical bonding properties of NiC3-/0. Both the photoelectron spectrum and photoelectron angular distribution were measured from the spectra, yielding useful geometrical and electronic information about NiC3-/0. The complementary theoretical calculations suggest that the linear and fan-like structures were both populated experimentally in the cluster beam. Further comparative study on the synergistic donor-acceptor interactions in both isomers revealed the side-on coordination-induced bond weakening in the fan-like isomer as compared to the linear isomer. These findings will shed light on the structure-dependent reactivity of transition metal carbides.

Photoelectron velocity-map imaging spectroscopy of nickel carbide: Examination of the low-lying electronic states

The photoelectron detachment of nickel carbide anion has been characterized using the photoelectron velocity-map imaging spectroscopy, allowing for a precise assignment of the electron affinity, vibrational frequencies, energy spacing and...