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Provided herein is an alkane dehydrogenation catalyst, a method of manufacturing an alkane dehydrogenation catalyst, and a method of converting alkanes to alkenes.
Disclosed is a catalyst system, its methods of preparation and its use for producing, among others, alkenes and/or saturated or unsaturated oxygenates and, which include at least one of an aldehyde and an acid (such as propyl aldehyde, acrolein, acrylic acid, isobutyl aldehyde, methacrolein, methacrylic acid), comprising subjecting the corresponding an alcohol or a diol selected from the group consisting of propanol, propanediol and isobutanol that is derivable from biomass, to a vapor phase process over the catalytic system described herein in the presence of a gas mixture of oxygen, air or nitrogen and/or other suitable diluting gas. In the case where one of 1-propanol, or 1,2-propanediol or 1,3-propanediol or a mixture thereof is subjected to a vapor phase catalytic process over the said catalytic system in the presence of air or oxygen, and a co-fed gas, such as nitrogen or other diluting gas, the product is at least one of propylene, propyl aldehyde, acrolein and acrylic acid. In the case where isobutanol is subjected to such a process, the product is at least one of isobutylene, isobutyl aldehyde, methacrolein and methacrylic acid. The catalyst system comprises a single catalytic zone or multi-catalytic zones, in each of which the composition of the co-feed and other reaction parameter can be independently controlled.
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Commercially available carbon blacks serve as capable metal-free catalysts for the selective hydrogenation of carbon–carbon multiple bonds under aerobic conditions using hydrazine as the terminal reductant. The reaction, which proceeds through a putative diimide intermediate, shows high tolerance to a variety of functional groups, including those sensitive to nucleophilic displacement by hydrazine, aerobic oxidation, or hydrazine-mediated reduction. Hydrazine chemisorbs strongly to the carbon surface, attenuating its native oxidative reactivity and allowing for selective hydrogenation. The catalytic sequence established here effectively umpolungs the reactivity of carbon, thus enabling the use of this low-cost material in selective reduction catalysis.
Abstract Regioselective hydrofunctionalization of alkynes represents a straightforward route to access alkenyl boronate and silane building blocks. In previously reported catalytic systems, high selectivity is achieved with a limited scope of substrates and/or reagents, with general solutions lacking. Herein, we describe a selective copper‐catalyzed Markovnikov hydrofunctionalization of terminal alkynes that is facilitated by strongly donating cyclic (alkyl)(amino)carbene (CAAC) ligands. Using this method, both alkyl‐ and aryl‐substituted alkynes are coupled with a variety of boryl and silyl reagents with high α‐selectivity. The reaction is scalable, and the products are versatile intermediates that can participate in various downstream transformations. Preliminary mechanistic experiments shed light on the role of CAAC ligands in this process.
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Several varieties of cycloaddition as well as nucleophilic and free radical addition to the highly reactive central bond of the title fluorocarbon ( 1 ) are described. [2 + 2] Cycloaddition to 1 has made available four of the five known representatives of the [2.2.2]propellane ring system, which are rare because of their extreme strain (in the absence of fluorine substitution) and high reactivity. Two of these, a propellanone and a propellene, are first reported here. Quantum mechanical calculations have shed light on many of these transformations.
In this study, tungstenocene(IV) dichloride was successfully deposited and grafted on the surface of a commercially-available non-ordered silica support via either a liquid-phase or a dry impregnation approach. After a high-temperature calcination step, two W(VI)-grafted silica catalysts, with a metal loading around 1.2–1.7 wt.%, were obtained. They were fully characterized by physisorption and spectroscopic techniques, which evidenced well-dispersed tungsten oxide polyoxo cluster sites, for the catalyst prepared via liquid-phase grafting, and evenly dispersed larger monoclinic tungsten(VI) oxide aggregates, for the catalyst prepared via dry impregnation, respectively. Both W/SiO 2 solids showed moderate to good conversion values in the epoxidation of (R)-(+)-limonene and methyl oleate (up to 68%), in the presence of aqueous hydrogen peroxide, with good selectivity to the desired epoxides (63% and 78%, respectively). Lastly, the heterogeneous character of the most interesting W/SiO 2 catalyst prepared via dry impregnation was confirmed by a hot centrifugation test and by an extended recovery and reuse of the solid in six catalytic runs.
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Heterogeneously catalyzed hydroformylation reactions avert the problems of separation in homogeneous reactions, reduce the discharge of phosphorus-containing wastes, and prevent the loss of precious metals. This review summarizes the developments of catalysts for heterogeneous hydroformylation in the last decade and proposes potential modification methods for future improvements. The hydroformylation properties of different reactants are compared in order to emphasize the fact that various olefins face unique challenges. The hydroformylation of ethylene requires the enhancement of catalytic activity and chemoselectivity, whereas that of propylene needs improvements in both chemoselectivity and regioselectivity. The hydroformylation of longer-chain olefins and styrene seeks further improvement in regioselectivity. The catalytic properties of activity, selectivity, and stability can be tuned through electronic effects (bimetallic effects, phosphine ligands, and single-atom catalysts), steric hindrance (encapsulation structures, diphosphine ligands, and local functional groups), and reaction condition optimization (temperature, pressure, and solvents). Furthermore, the understanding of these effects is critical in future catalyst design for heterogeneous hydroformylation reactions.
Databases of sooting indices, based on measuring some aspect of sooting behavior in a standardized combustion environment, are useful in providing information on the comparative sooting tendencies of different fuels or pure compounds. However, newer biofuels have varied chemical structures including both aromatic and oxygenated functional groups, which expands the chemical space of relevant compounds. In this work, we propose a unified sooting tendency database for pure compounds, including both regular and oxygenated hydrocarbons, which is based on combining two disparate databases of yield-based sooting tendency measurements in the literature. Unification of the different databases was made possible by leveraging the greater dynamic range of the color ratio pyrometry soot diagnostic. This unified database contains a substantial number of pure compounds (≥ 400 total) from multiple categories of hydrocarbons important in modern fuels and establishes the sooting tendencies of aromatic and oxygenated hydrocarbons on the same numeric scale for the first time. Then, using this unified sooting tendency database, we have developed a predictive model for sooting behavior applicable to a broad range of hydrocarbons and oxygenated hydrocarbons. The model decomposes each compound into single-carbon fragments and assigns a sooting tendency contribution to each fragment based on regression against the unified database. The model’s predictive accuracy (as demonstrated by leave-one-out cross-validation) is comparable to a previously developed, more detailed predictive model. The fitted model provides insight into the effects of chemical structure on soot formation, and cases where its predictions fail reveal the presence of more complicated kinetic sooting mechanisms. Our work will therefore enable the rational design of low-sooting fuel blends from a wide range of feedstocks and chemical functionalities.
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