Liquid-phase hydrogenation of bio-refined succinic acid to 1,4-butanediol using bimetallic catalysts

open access articleDevelopment of a Crotalaria juncea based biorefinery produce large quantity of waste glycerol after trans-esterification of the juncea seeds. This glycerol, after purification, is used as a substrate for producing succinic acid on a microbial route. Hydrogenation of this bio-refined succinic acid is carried out under high pressure in order to produce 1,4- butanediol (BDO) using a batch slurry reactor with cobalt supported ruthenium bimetallic catalysts, synthesized inhouse. It is demonstrated that, using small amounts of ruthenium to cobalt increases the overall hydrogenation activity for the production of 1,4-butanediol. Hydrogenation reactions are carried out at various operating temperatures and pressures along with changes in the mixing ratios of ruthenium chloride and cobalt chloride hexahydrate, which are used to synthesize the catalyst. The Ru-Co bimetallic catalysts are characterized by XRD, FE-SEM and TGA. Concentrations of the hydrogenation product are analyzed using Gas chromatography-Mass spectrometry (GC-MS). Statistical analysis of the overall hydrogenation process is performed using a Box-Behnken Design (BBD)

Extension of the single-event microkinetic model to alkyl substituted monoaromatics hydrogenation on a Pt catalyst

The Single-Event Micro Kinetic (SEMK) methodology, which had been successfully applied to benzene hydrogenation on a Pt catalyst, has now been extended toward substituted monoaromatics, that is, toluene and o-xylene. The single event concept Combined with thermodynamic constraints. allowed to significantly reduce the number of adjustable parameters. In addition to the number of unsaturated nearest neighbor carbon atoms, H-atom addition rate and equilibrium coefficients were assumed to depend on the carbon atom type, that is, secondary or tertiary. This leads to three additional :reaction families compared to benzene hydrogenation: Gas. phase toluene and o-xylene hydrogenation experiments were performed on 0.5 wt % Pt/ZSM-22 in a temperature range from 423 to 498 K, a total pressure range from 1 to 3 MPa, H-2 inlet partial pressures between 100 and 600 kPa and aromatic inlet partial pressures between 10 and 60 kPa. A simultaneous regression of the :SEMK,Model to an experimental data set consisting of 39 toluene and 37 o-xylene hydrogenation experiments resulted in activation energies of H additions to tertiary:carbon:atoms:that are 10.5 kJ mol(-1) higher than to secondary carbon atoms. This can be related to the steric hindrance experienced during H addition to a carbon atom bearing a substituent. The presence of a substituent on the aromatic king was found not to affect the Chemisorption enthalpies. The reaction path analysis has been carried out via differential contribution analysis and identified that the hydrogenation first, occurs at secondary carbon atoms, prior to the hydrogenation of the tertiary carbon atoms in the hydrogenation Sequence. This is in line with the distribution of hydrocarbon species on the catalyst surfac

"Narrow" Graphene Nanoribbons Made Easier by Partial Hydrogenation

It is a challenge to synthesize graphene nanoribbons (GNRs) with narrow widths and smooth edges in large scale. Our first principles study on the hydrogenation of GNRs shows that the hydrogenation starts from the edges of GNRs and proceeds gradually toward the middle of the GNRs so as to maximize the number of carbon-carbon $\pi$-$\pi$ bonds. Furthermore, the partially hydrogenated wide GNRs have similar electronic and magnetic properties as those of narrow GNRs. Therefore, it is not necessary to directly produce narrow GNRs for realistic applications because partial hydrogenation could make wide GNRs "narrower"

Highly active iridium(I) complexes for the selective hydrogenation of carbon-carbon multiple bonds

New iridium(I) complexes, bearing a bulky NHC/phosphine ligand combination, have been established as extremely efficient hydrogenation catalysts that can be used at low catalyst loadings, and are compatible with functional groups which are often sensitive to more routinely employed hydrogenation methods

Structure/activity relationships applied to the hydrogenation of α,β-unsaturated carbonyls: The hydrogenation of 3-butyne-2-one over alumina-supported palladium catalysts

The gas phase hydrogenation of 3-butyne-2-one, an alkynic ketone, over two alumina-supported palladium catalysts is investigated using infrared spectroscopy in a batch reactor at 373 K. The mean particle size of the palladium crystallites of the two catalysts are comparable (2.4 ± 0.1 nm). One catalyst (Pd(NO3)2/Al2O3) is prepared from a palladium(II) nitrate precursor, whereas the other catalyst (PdCl2/Al2O3) is prepared using palladium(II) chloride as the Pd precursor compound. A three-stage sequential process is observed with the Pd(NO3)2/Al2O3 catalyst facilitating complete reduction all the way through to 2-butanol. However, hydrogenation stops at 2-butanone with the PdCl2/Al2O3 catalyst. The inability of the PdCl2/Al2O3 catalyst to reduce 2-butanone is attributed to the inaccessibility of edge sites on this catalyst, which are blocked by chlorine retention originating from the catalyst’s preparative process. The reaction profiles observed for the hydrogenation of this alkynic ketone are consistent with the site-selective chemistry recently reported for the hydrogenation of crotonaldehyde, an alkenic aldehyde, over the same two catalysts. Thus, it is suggested that a previously postulated structure/activity relationship may be generic for the hydrogenation of α,β-unsaturated carbonyl compounds over supported Pd catalysts

Hydrogenation of cyclohexene with LaNi5-xAlxHn metal hydrides, suspended in cyclohexane or ethanol

The hydrogenation of cyclohexene on the metal hydride forming alloys LaNi4.8Al0.2, LaNi4.9Al0.1 and LaNi5, all suspended in cyclohexane and LaNi5 suspended in ethanol, has been investigated. Two sources for hydrogen are recognized: hydrogen supplied by the gas phase and hydrogen which is available inside the metal hydride particles. For hydrogen which is supplied by the gas phase, the kinetics can be described with a two-site Langmuir-Hinshelwood relation, assuming a fast dissociative adsorption of hydrogen. The values of the rate constant, kr, and adsorption coefficient for cyclohexene, KC6H10, are lower if the hydrogenation is carried out on the metal (alpha) phase of the metal alloys instead of on the hydride (ß) phase. Also, increasing the aluminum content results in a decrease of kr and KC6H10. In ethanol, a higher reaction rate constant and a lower adsorption coefficient were observed. The hydrogenation of cyclohexene with hydrogen provided by the metal hydride particles has been described with a combination of the rate equation for the hydrogenation and the relation for the hydrogen desorption from the hydride. It was found that the reaction rate decreases during the cyclohexene conversion, because the nature of hydride particles changes from the ß into the ¿ phase as the reaction proceeds. Initially, the hydrogenation is partly limited by the transport of hydrogen from the centre of the particle to the surface

Highly selective hydrogenation of furfural over supported Pt nanoparticles under mild conditions

The selective liquid phase hydrogenation of furfural to furfuryl alcohol over Pt nanoparticles supported on SiO₂, ZnO, γ-Al2O₃, CeO₂ is reported under extremely mild conditions. Ambient hydrogen pressure, and temperatures as low as 50 °C are shown sufficient to drive furfural hydrogenation with high conversion and >99% selectivity to furfuryl alcohol. Strong support and solvent dependencies are observed, with methanol and n-butanol proving excellent solvents for promoting high furfuryl alcohol yields over uniformly dispersed 4 nm Pt nanoparticles over MgO, CeO₂ and γ-Al₂O₃. In contrast, non-polar solvents conferred poor furfural conversion, while ethanol favored acetal by-product formation. Furfural selective hydrogenation can be tuned through controlling the oxide support, reaction solvent and temperature

Highly selective electrochemical hydrogenation of alkynes: Rapid construction of mechanochromic materials

Electrochemical hydrogenation has emerged as an environmentally benign and operationally simple alternative to traditional catalytic reduction of organic compounds. Here, we have disclosed for the first time the electrochemical hydrogenation of alkynes to a library of synthetically important Z-alkenes under mild conditions with great selectivity and efficiency. The deuterium and control experiments of electrochemical hydrogenation suggest that the hydrogen source comes from the solvent, supporting electrolyte, and base. The scanning electron microscopy and x-ray diffraction experiments demonstrate that palladium nanoparticles generated in the electrochemical reaction act as a chemisorbed hydrogen carrier. Moreover, complete reduction of alkynes to saturated alkanes can be achieved through slightly modified conditions. Furthermore, a series of novel mechanofluorochromic materials have been efficiently constructed with this protocol that showed blue-shifted mechanochromism. This discovery represents the first example of cis-olefins-based organic mechanochromic materials