Abstract An enhancement of the properties of pyrolysis liquids (PL) from municipal plastic waste (mainly low-density polyethylene) by catalytic hydrotreatment is required to obtain automotive quality fuels. In this context, we report the design of a pilot catalytic hydrotreatment reactor using computational fluid dynamics (CFD). This modelling technique considered fluid flows, gas diffusion, olefin hydrogenation reactions, and heat transfer. The built model allowed the development of different sensitive analysis to evaluate the influence of spatial time, heat transfer fluid (used as a reactor coolant) and hydrogen/pyrolysis liquid ratio. Possible phase changes (from gas to liquid) were analyzed by a thermodynamic approach. The results showed that the refrigerant oil allows alleviating possible temperature gradients arising from the exothermic hydrogenation reaction. It was also found that the system can be optimized in order to minimize the energy cost by adjusting the inlet temperature of the reactive gas (H2) and the refrigerant oil flow. Condensations in the reactive chamber could be avoided by working at intermediate pressures (40–60 bar) and/or increasing the feed of H2. Additionally, the results obtained with the CFD 3D model together with the condensation analysis allowed to optimize the operational regime and the pilot-reactor design in terms of dimensioning and construction materials.

We report that the cationic iridium complex (^iPrPCP)IrH⁺ catalyzes the transfer-dehydrogenation of alkanes to give alkenes and hydrogen isotope exchange (HIE) of alkanes and arenes. Contrary to established selectivity trends found for C-H activation by transition metal complexes, strained cycloalkanes, including cyclopentane, cycloheptane, and cyclooctane, undergo C-H addition much more readily than <i>n</i>-alkanes, which in turn are much more reactive than cyclohexane. Aromatic C-H bonds also undergo H/D exchange much less rapidly than those of the strained cycloalkanes, but much more favorably than cyclohexane. The order of reactivity toward dehydrogenation correlates qualitatively with the reaction thermodynamics, but the magnitude is much greater than can be explained by thermodynamics. Accordingly, the cycloalkenes corresponding to the strained cycloalkanes undergo hydrogenation much more readily than cyclohexene, despite the less favorable thermodynamics of such hydrogenations. Computational (DFT) studies allow rationalization of the origin of reactivity and the unusual selectivity. Specifically, the initial C-H addition is strongly assisted by β-agostic interactions, which are particularly favorable for the strained cycloalkanes. Subsequent to α-C-H addition, the H atom of the β-agostic C-H bond is transferred directly to the hydride ligand of (^iPrPCP)IrH⁺ to give a dihydrogen ligand. The overall processes, C-H addition and β-H-transfer to hydride, are calculated to generally have minima on the IRC surface although not necessarily on the enthalpy or free energy surfaces; these minima are extremely shallow such that the 1,2-dehydrogenations are effectively concerted although asynchronous.

Greenhouse gas anthropogenic emissions have triggered global warming with increasingly alarming consequences, motivating the development of carbon-free energy systems. Hydrogen is proposed as an environmentally benign energy vector to implement this strategy, but safe and efficient large-scale hydrogen storage technologies are still lacking to develop a competitive Hydrogen economy. LOHC (Liquid Organic Hydrogen Carrier) improves the storage and handling of hydrogen by covalently binding it to a liquid organic framework through catalytic exothermic hydrogenation and endothermic dehydrogenation reactions. LOHCs are oil-like materials that are compatible with the current oil and gas infrastructures. Nevertheless, their high dehydrogenation enthalpy, platinoid-based catalysts, and thermal stability are bottlenecks to the emergence of this technology. In this review, hydrogen storage technologies and in particular LOHC are presented. Moreover, potential reactivities to design innovative LOHC are discussed.

Temperature hysteresis is observed only in exothermic heterogeneous catalytic reactions (viz., oxidation and methanation of CO or propene hydrogenation) and is absent in the case of endothermic reactions (dehydrogenation of isobutane) or reactions with heat close to zero (viz., 2-butene isomerization). Temperature hysteresis in hydrogenation reactions was discovered for the first time. The concept of local overheating of catalyst active sites caused by poor removal of the reaction heat is proposed to provide a noncontradictory interpretation of the appearance of hysteresis loops.

Abstract For heterogeneously catalyzed multiphase reactions the formation of bubbles may have an influence on the effective reaction rate. This second of a series of two contributions deals with the Ni‐catalyzed hydrogenation of hexene, which was used as a model system for an exothermic gas/liquid (G/L) reaction, where gas/vapor bubbles may be generated by overheating of the catalyst. (In part I, results of catalytic H 2 O 2 decomposition were presented, where the evolution of gas bubbles (O 2 ) always occurs.) A criterion for the formation of vapor bubbles for exothermic G/L reactions is presented, which was verified by experiments in a reactor with an inspection window. For a particle diameter of 6 mm, the effective kinetics of hexene hydrogenation is influenced by internal and external mass and heat transfer. A new and simple method to estimate the mass and heat transfer parameters and the effectiveness factors with regard to pore and external diffusion is presented, which combines the measured temperature difference(s) and the effective rate. For the given reaction conditions, the rate of hexene hydrogenation is not influenced by the evolution of vapor bubbles.

The use of aluminum chloride in dichloromethane to crack polyolefin chains in tandem with alkylation of the resulting products has been previously reported as an efficient polyolefin recycling route. Building off this work, we report that a tandem cracking-hydrogenation system also efficiently converts polyolefins into gasoline-range light alkanes at mild temperatures without needing a hydrocarbon co-reactant. This Lewis acid and hydrogenation bifunctional system uses anhydrous aluminum chloride as the acid catalyst and Pd/C as a hydrogenation catalyst to achieve nearly 80 % conversion of low-density polyethylene (LDPE) at 70 °C in three hours, with 90+% selectivity towards gasoline-range (C 4 -C 12 ) branched alkanes. By combining the endothermic cracking reaction with the exothermic hydrogenation reaction, the thermodynamic limitations to low-temperature polyolefin deconstruction can be overcome. In using hydrogenation instead of alkylation, the system’s carbon efficiency is greatly improved, the cost of the reactants is reduced and the overall mass of both reactants and products reduced as well.

aldehyde or ketone ¢ Hydrogenation of nitriles ¢ Hydrogenation of nitroaromatics Hydrogenation 139 Selection … converted to n-alcohols by hydrogenation. Hydrogenation of oxy aldehydes Hydrogenation of aldehyde prepared … probably 4 x 8 mesh. The hydrogenation step employs a standard hydrogenation catalyst, either supported