A Green Approach to Ethyl Acetate: Quantitative Conversion of Ethanol through Direct Dehydrogenation in a Pd–Ag Membrane Reactor

Abstract

Pincers do the trick: The conversion of ethanol to ethyl acetate and hydrogen was achieved using a pincer-Ru catalyst in a Pd-Ag membrane reactor. Near quantitative conversions and yields could be achieved without the need for acid or base promoters or hydrogen acceptors (see scheme).

Environmentally benign synthesis of amides and ureas via catalytic dehydrogenation coupling of volatile alcohols and amines in a Pd-Ag membrane reactor

“…The Pd-Ag/ceramic membranes were prepared by the Ag-controlled electroless co-plating of Pd and Ag [3,33]. Before plating the supports were cleaned sequentially by ethanol, 4% aqueous KOH solution and deionized water and well Pd seeding activated [34].…”

“…Since such a reaction can only be carried out at a reaction temperature higher than the boiling point of the reactant (ethanol 78°C) and therefore, the produced hydrogen needs to be removed from the reaction system to overcome chemical equilibrium and also to avoid pressure build-up. The selective removal of hydrogen by an ultrathin Pd-Ag membrane reactor was demonstrated to be a viable solution [3]. From the previous studies we also noticed that the reaction rate of dehydrogenative reactions is typically slow, presumably because of the relatively low reaction temperature.…”

“…Therefore, a relatively long reaction time (typically in several hours) is required in order to achieve high conversion rate, but this also imposes a high requirement in membrane selectivity since otherwise the material loss during the reaction will be substantial. A membrane selectivity over 2000 for H 2 /N 2 was used in our previous studies as a good indicator of membrane quality [3]. Such a high selectivity requirement can be easily achieved by Pd-Ag membranes fabricated through a silver concentration-controlled co-plating method, but it is very challenging for other hydrogen selective membranes, such as polymer, silica, zeolite or carbon molecular sieve membranes [4].…”

A new class of PN3-pincer ligands for metal–ligand cooperative catalysis

“…However, challenges exit, especially with the aim of higher conversion to avoid the need for the separation of the ester products from the reaction mixtures, due to the required high reaction temperature and the equilibrium limit in a closed system. A defect-free Pd-Ag membrane reaction was thus designed for the removal of the liberated hydrogen in situ, enabling the reaction to proceed at elevated temperatures and to reach quantitative conversion and EA production yields [93]. Furthermore, both of the liberated H 2 fluxes and the inner pressure of the reactor could be used to monitor the reaction progress in real-time.…”

Synthesis of mixed-ligand cobalt complexes and their applications in high cis-1,4-selective butadiene polymerization

“…The extensive and diverse coordination chemistry of the cobalt complexes have provided diversified catalytic properties as the product microstructures, such as cis-1,4, trans-1,4, 1,2 enchainment and their combinations crucially depends on catalyst formulation, controlling of the product's properties by catalyst design and chosen has thus been feasible. Publications to date have described various ligands supported metal complexes, in particular, asymmetry PN 2 and PN 3 type ligands, which developed by us and Milstein, respectively, [9][10][11][12][13] have attracted much attention as the dissociation of labile metal-phosphine bond (metal-P bond is weak with respective to metal-N bond) tends to generation of open site available for small molecule coordination and activation, while the intact two metal-N bonds could effectively chelated , stabilize the metal center, as well as induce regio-and stereoselectivity. Relevant X-ray analysis data were collected on a Bruker SMART APEX diffractometer with a CCD area detector, using graphite monochromated Mo K radiation (λλ = 0.71073 Å).…”