First Phenol Carboxylation with CO2 on Carbon Nanostructured C@Fe-Al2O3 Hybrids in Aqueous Media under Mild Conditions

Abstract

Novel hybrid materials with integrated catalytic properties and hydrophobic response, C@Fe–Al2O3 hybrid samples, were presented and tested as catalysts for phenol reaction in aqueous solutions at atmospheric pressure and mild temperature conditions, using CO2 as a feedstock. A series of carbon-coated γ-alumina pellets (C@Fe–Al2O3) were synthesized and characterized by TGA, Brunauer–Emmett–Teller (BET) method, Raman spectroscopy, SEM, TEM, and XPS in order to get comprehensive knowledge of their properties at the nanoscale and relate them with their catalytic behavior. The results obtained correlated their catalytic activities with their carbon surface compositions. The application of these materials as active catalysts in the Kolbe–Schmitt reaction for CO2 conversion in aqueous media was proposed as an alternative reaction for the valorization of exhausts industrial effluents. In these early tests, the highest conversion of phenol was observed for the hybrid samples with the highest graphitic characteristic and the most hydrophobic behavior. Carboxylation products such as benzoic acid, p-hydroxybenzoic acid, and salicylic acid, have been identified under these experimental conditions.

A critical review of the production of hydroxyaromatic carboxylic acids as a sustainable method for chemical utilisation and fixation of CO2

“…Since the Kolbe-Schmitt reaction was first reported in 1884 [10], numerous investigations have focused on overcoming either the two-pot, high pressure or batch mode nature of the industrially applied carboxylation process. This has led to the development of various carboxylation methodologies, categorised by the use of novel activation/carboxylation agents [53,55], heterogeneous catalysts [48][49][50][51][52]and homogeneous stoichiometric reagents [35,53,54] as shown in Table 1. These new developments attempt to reduce the long reaction times and high CO 2 pressures that characterise the conventional Kolbe-Schmitt reaction.…”

“…The first Kolbe-Schmitt type reaction using heterogeneous catalyst was recently reported [49]. Carbon coated -alumina pellets (C@Fe-Al 2 O 3 ), a new 𝛾 hybrid materials catalyst, were synthesised to give both catalytic and hydrophobic characteristics for phenol reaction in aqueous solutions at atmospheric pressure and mild temperature conditions, using CO 2 as a feedstock [49]. The Kolbe-Schmitt reaction is inhibited by the presence of water, since anhydrous phenoxide is considered as the intermediate for carboxylation of the aromatic ring [10].…”

“…One of the added CO 2 moieties performs an electrophilic attack on the benzene ring, whereas the old CO 2 moiety becomes a molecule of solvent. 58 development of various carboxylation methodologies, categorised by the use of novel activation/carboxylation agents, 53,55 heterogeneous catalysts [48][49][50][51][52] and homogeneous stoichiometric reagents 35,53,54 as shown in Table 1. These new developments attempt to reduce the long reaction times and high CO 2 pressures that characterise the conventional Kolbe-Schmitt reaction.…”

Organic Base-Mediated Carboxylation of (Hetero)aromatic Compounds Using Supercritical Carbon Dioxide (scCO2)

“…The selectivity of the Kolbe-Schmitt reaction has been reported to be affected by temperature, pressure, and the type of alkaline metal used. 8,28 Mechanistically, we believe that the steric bulk of DBU prevents ortho carboxylation. Additionally, DBU mediated carboxylation mitigates the use of highly hygroscopic alkaline metal phenoxides allowing the reaction to be performed in a one-pot process with wet CO2.…”

N-Formylation of Amines with Carbon Dioxide and Hydrogen Catalyzed by Ionic Liquid-Assisted Ru Complexes

“…However, CO 2 is also a nontoxic, abundant, cheap, and renewable C1 resource. , The transformation of CO 2 into various compounds such as urea, salicylic acid, carbonates, polymers, alcohols, and formic acid has been extensively studied. − The main obstacles for the utilization of CO 2 are the low energy content and the high chemical stability of CO 2 . Carbon capture, utilization, and storage (CCUS) is considered to be a technically and economically feasible method to reduce greenhouse gas emissions .…”