Unprecedented Use of NHC Gold (I) Complexes as Catalysts for the Selective Oxidation of Ethane to Acetic Acid

Abstract

The highly efficient eco-friendly synthesis of acetic acid (40% yield) directly from ethane is achieved by the unprecedented use of N-heterocyclic carbene (NHC) and N-heterocyclic oxo-carbene (NHOC) gold(I) catalysts in mild conditions. This is a selective and promising protocol to generate directly acetic acid from ethane, in comparison with the two most used methods: (i) the three-step, capital- and energy-intensive process based on the high-temperature conversion of methane to acetic acid; (ii) the current industrial methanol carbonylation processes, based in iridium and expensive rhodium catalysts. Green metrics determinations highlight the environmental advantages of the new ethane oxidation procedure. Comparison with previous reported published catalysts is performed to highlight the features of this remarkable protocol.

Commercial Gold Complexes Supported on Functionalised Carbon Materials as Efficient Catalysts for the Direct Oxidation of Ethane to Acetic Acid

“…The electronic withdrawing ligand PPh 3 associated to its steric hindrance, appears to contribute for the achievement of a lower yield of acetic acid relative to catalysts 2-4, although maintaining the oxidative selectivity. The herein obtained yields (up to 21%) are lower than the recently reported (33-39.8%) for homogeneous N-heterocyclic carbene and oxo-carbene gold(I) catalysts [51]. However, we should keep in mind the advantageous availability of the commercial Au compounds relative to harder-to-prepare and less stable carbene complexes.…”

“…Gold catalysts have been widely used in many reactions as shown by several reviews [46][47][48][49]. However, the only references found in the literature for the use of gold in ethane oxidation are from the work of Wang et al, dealing with non-supported Au-Pd nanoparticles in water, but the main product obtained was ethyl hydroperoxide [50] and our own work dealing with homogeneous N-heterocyclic carbene and oxo-carbene Au(I) compounds [51]. Therefore, to the best of our knowledge, the present work reports the first use of commercial gold complexes supported on carbon nanomaterials in the oxidation of ethane to produce acetic acid.…”

Predicting Extraction Selectivity of Acetic Acid in Pervaporation by Machine Learning Models with Data Leakage Management

“…Acetic acid is widely used as a precursor for the production of many important industrial products, including paints, adhesives, pharmaceuticals, plasticizers, and artificial fragrances . Currently, acetic acid is primarily produced from petroleum, mainly through methanol carbonylation, which requires high temperature and pressure with a large carbon footprint. − It is estimated that methanol carbonylation’s cradle-to-gate global warming potential is approximately 1 kg CO 2 eq/kg of acetic acid production, which is similar to concrete, currently one of the most carbon-intensive manufacturing products. These products are in critical need of decarbonization .…”

Unraveling the transformative pathways of Au-NHC and Au-alkynyl complexes and bridging the gap between molecular and nanoscale gold systems

“…With their distinctive chemical and catalytic properties, gold compounds have been the subject of extensive research in recent decades. Research in this field employs either welldefined gold complexes 2,12,[52][53][54][55][56][57][59][60][61][62][63][64][65][66][67][68][69][70] or gold particles ranging from subnanometer to macroscale with a well/poorly defined structure, 1,[3][4][5][6][7][8][9][10][11]14,24,[28][29][30][31][32][33][34][35][36][37]39,45,49 each demonstrating unique catalytic behavior. Gold particles of nanoscale size, specifically Au(0), have been shown to be excellent catalysts in several reactions.…”