Phenolic Carboxyl Research Articles

CO2 capture and utilization by biocatalytic synthesis of carboxylic acids: a process design study

The search for less energy-intensive processes is pushing toward a diversification of Carbon-Capture and Utilization/Sequestration (CCU/S) pathways. Biocatalytic processes offer sustainable solutions characterized by extremely mild operating conditions. Over the last decade, post-combustion CO2 capture based on enzymatic reactive absorption experienced remarkable growth from the laboratory to the demonstration scale. The present study explores a novel CCU concept based on phenol carboxylation catalyzed by cofactor-free decarboxylases. The design of the CCU process includes CO2 capture by alkaline solvents boosted by carbonic anhydrase followed by bicarbonate fixation via enzymatic phenol carboxylation. Phenols generated from fractional pyrolysis of biomass were assumed as carboxylation substrates. Two process layouts have been developed and modelled, and reliable experimental data and kinetic model supported the computations. Simulated best cases prove to be feasible options for integrating the enzyme cascade with the conventional CO2 absorption/desorption loop and lignocellulose biomass-derived substrates.

Sustainable CO2 Fixation onto Bio-Based Aromatics

Carboxylation reactions using carbon dioxide (CO2) as a reactant to produce new C-C bonds represent one of the most promising routes in carbon capture and utilization practices, which yield higher-atom and energy-efficient products. Kolbe–Schmitt-type reactions represent the carboxylation of aromatic compounds to their carboxylic acid derivatives. This study was the first and only to systematically investigate, thoroughly explain preparation procedures, and minutely describe the analytical methods of Kolbe–Schmitt and Marasse carboxylation of phenol. Most importantly, this study provides guidelines for the utilization of state-of-the-art technology in this century-old yet not sufficiently described reaction system. Kolbe–Schmitt carboxylation of phenol was found to be possible using sodium hydroxide (NaOH), potassium hydroxide (KOH), and sodium carbonate (Na2CO3), while the Marasse method was active only with potassium carbonate (K2CO3) as a reactant. The formation of metal phenoxide is the rate-determining step, which, however, could be more efficiently prepared under reflux. A new, simple, and repeatable HPLC method was described to identify and quantify all possible products of mono- and dicarboxylated phenols. It was found that all procedures result in the highest selectivity for salicylic acid (SA), followed by minor amounts of 4-hydroxybenzoic acid (4HBA) and 4-hydroxyisophthalic acid (4HiPh).

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

AbstractA straightforward site-selective method for the direct carboxylation of resorcinols (3-hydroxyphenol derivatives), phenols, and indoles is reported. The products were obtained in moderate to high yields using supercritical carbon dioxide as an electrophile and solvent under basic conditions. This method offers solvent and metal free conditions without the cumbersome exclusion of air or water with convenient purification.

Nickel-catalyzed para-selective carboxylation of phenols with CBr4/MeOH

1,10-Phenanthroline-assisted, Ni(ii)-catalyzed para-carboxylation of phenol derivatives is reported.

Determination and Calculation of Sodium Phenol Carboxylation Heat Release

Determination and Calculation of Sodium Phenol Carboxylation Heat Release

Direct Phenol Carboxylation by Carbon Dioxide Over Hydroxides/Carbonates – Revisiting Kolbe-Schmitt Reaction for Bio-Based Aromatics

Direct Phenol Carboxylation by Carbon Dioxide Over Hydroxides/Carbonates – Revisiting Kolbe-Schmitt Reaction for Bio-Based Aromatics

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

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.

Hydroxymethylation followed by α-bromoisobutyrylation as an effective and precise method for characterization of functional groups of hydroxymethylated lignin

The direct use of lignin results in the synthesis and production of low-value materials. Therefore, the chemical modification of lignin increases not only its reactivity, but also improves its compatibility and better dispersion in the lignin-based polymeric materials where lignin acts as a good substitute for oil-based polyols. Systematic studies were conducted in the present work. Hydroxymethylated lignin (HML) was synthesized via its reaction with formaldehyde, and functional groups present in the sol fraction of HML were then quantitatively investigated by aqueous potentiometric/conductometry titration prior to any further modification and by 1HNMR and FTIR techniques after reacting with α-bromoisobutyryl bromide, resulting in brominated HML (BHML). To calculate moles of hydroxyl groups per gram of HML, 1HNMR of BHML was recorded in the presence of a given amount of N,N-dimethylformamide as an internal standard. It was found that the number of hydroxyl groups increases from 6.44 mmol/g in the lignin to 7.77 mmol/g in the HML. The moles of phenolic hydroxyl and carboxyl groups per gram of HML were calculated using aqueous titration. It was found that the moles of phenolic hydroxyl groups in the HML decrease by 19.8% compared to lignin. Due to poor solubility of the HML in tetrahydrofuran, BHML was used in the GPC analysis, from which the number average molecular weight ($$\bar{M}_{\rm{n}}$$) of the HML was obtained after some calculations to be 1014 g/mol. It was observed that modification of lignin with formaldehyde increases not only its functional groups but also increases its molecular weight by creating methylene bridges between the two lignin molecules.

Reactions related with hydroxyl, carboxyl and alkyl side chain at different temperature stages and the effects on low-rank coal ignition

Low-rank coal contains abundant hydroxyl, carboxyl and alkyl side chains, and reactions related to these groups are the main reason for the spontaneous combustion of low-rank coal. Here, two different low-rank coals (BRXL, YJL52) are selected. Firstly, the ignition temperatures of the coals are determined by thermogravimetric method. Secondly, the coals are heated at 100°C temperature intervals before the ignition temperature in the thermogravimetry, and infrared measurement is performed to explore the changes of these groups. Combining previous studies in the literatures with infrared analysis, it is found that reactions related are as follows: phenolic hydroxyl converting into alcoholic hydroxyl, alcoholic hydroxyl further oxidizing to carboxyl, and carboxyl decarboxylating into alkyl side chains. After that, the changes of phenolic hydroxyl and carboxyl on the surface of the coal at 100°C temperature intervals are determined by titration, which further reveal the main reactions occurred in every temperature interval. Additionally, the actual heat release in different temperature ranges is discussed with the reaction enthalpies of the above-mentioned main reactions. As a result, the key temperature stage that causes spontaneous combustion is found. The screening study in this paper on the reaction of low-rank coal before spontaneous combustion provides a theoretical basis for the control of spontaneous combustion of low-rank coal.

Influence of Base-Catalyzed Organosolv Fractionation of Larch Wood Sawdust on Fraction Yields and Lignin Properties

Lignocellulose-based biorefineries are considered to play a crucial role in reducing fossil-fuel dependency. As of now, the fractionation is still the most difficult step of the whole process. The objective of this study is to investigate the potential of a base-catalyzed organosolv process as a fractionation technique for European larch sawdust. A solvent system comprising methanol, water, sodium hydroxide as catalyst, and anthraquinone as co-catalyst is tested. The influence of three independent process variables, temperature (443–446 K), catalyst loading (20–30% w/w), and alcohol-to-water ratio (30–70% v/v), is studied. The process conditions were determined using a fractional factorial experiment. One star point (443 K, 30% v/v MeOH, 30% w/w NaOH) resulted in the most promising results, with a cellulose recovery of 89%, delignification efficiency of 91%, pure lignin yield of 82%, residual carbohydrate content of 2.98% w/w, and an ash content of 1.24% w/w. The isolated lignin fractions show promising glass transition temperatures (≥424 K) with high thermal stabilities and preferential O/C and H/C ratios. This, together with high contents of phenolic hydroxyl (≥1.83 mmol/g) and carboxyl groups (≥0.52 mmol/g), indicates a high valorization potential. Additionally, Bjorkman lignin was isolated, and two reference Kraft cooks and a comparison to three acid-catalyzed organosolv fractionations were conducted.

Embedded characteristics and macromolecular structure of sporinite of Pingdingshan coal in Early Permian

ABSTRACT The sporinite of Pingdingshan coal in Early Permian was mainly microsporinite with less macrosporinite. The aggregated sporinite was scattered in the desmocollinite; the dispersed sporinite was mostly oriented and embedded in the desmocollinite adjacent to the macerals of vitrodetrinite, inertodetrinite, liptodetrinite, etc. To explore the macromolecular structure of sporinite in Pingdingshan coal, the equal density gradient method was chosen to enrich sporinite with the density gradient being primarily 1.16–1.20 g/cm3. The spectral parameters of sporinite were analyzed by FTIR, NMR, XPS, etc. Results indicated that the sporinite had an aliphatic-aromatic structure and it was mostly composed of aliphatics with less aromatics and medium content of C = O oxygen-containing functional group. Each fragrant cluster in sporinite had an average of 1-2 aromatic rings, and the structure of the aromatic carbon was mainly types of naphthalene and benzene. The sporinite contained mostly oxygen atom in the form of phenolic hydroxyl oxygen, carboxyl oxygen, and ether oxygen, of which phenolic hydroxyl oxygen and carboxyl oxygen were the most prominent. In addition, nitrogen atom existed mostly in the form of pyridine. The structural model of the sporinite was constructed and optimized by Materials Studio. The macromolecular structure model of sporinite in Pingdingshan coal had a molecular formula of C203H244N2O30 and a relative molecular weight of 3192.10. The corresponding density of the predictive model in the minimum potential energy is 1.19 g/cm3, and the results are consistent with the experimental values. The results are helpful to understand the macromolecular characteristics of sporinite and will provide the theoretical basis for the classification and fine utilization of Pingdingshan coal.

Исследование каталитической активности K2CO3 в реакции карбоксилирования фенола натрийэтилкарбонатом

The catalуtic activitу of К2СО3 in the carboxуlation reaction of phenol with sodium ethуl carbonate has been investigated. The aim of the research was to develop a new efficient method for producing salicylic acid which is widely used in pharmaceuticals and other type preparations, also used in agriculture as an effective plant growth promoter. The most widespread synthesis method of salicylic acid is the Kolbe-Schmitt of phenol carboxylation, but it has a number of serious disadvantages. One of the alternative methods is the use of alkali metal salts of mono ethers of the carbonic acids as carboxylating agents in the carboxylation of phenol. In order to improve the method of production of salicylic acid, the catalytic activity of the К2СО3 catalyst at the carboxylation of phenol with sodium ethyl carbonate was studied for the first time. The effect of the process parameters (temperature, pressure, reaction time, ratio of catalyst to carboxylating agent) on the yield of the target product was studied. It was found optimal conditions: T=160°C, PCO2=10 atm, τ=7(4+3) h, [К2СО3]:[SEC]=0.07:1 at which the yield of the target product was 80%. The yields of the target product at phenol carboxylation with sodium ethyl carbonate in the presence and without K2CO3 were determined. It was found that К2СО3 shows the catalytic activity during carboxylation reaction.

Expanding Substrate Specificity of Salicylate Decarboxylase by Site-directed Mutagenesis for Expansion of the Entrance Region Connecting to the Substrate Access Tunnel

Salicylate decarboxylase (Sdc, EC 4.1.1.91) from the yeast Trichosporon moniliiforme WU-0401 catalyzes the carboxylation of phenol to salicylic acid and is applicable to enzymatic Kolbe-Schmitt rea...

(Fe3+)-UVC-(aliphatic/phenolic carboxyl acids) systems for diethyl phthalate ester degradation: A density functional theory (DFT) and experimental study

Diethyl phthalate ester (DEP) can be degraded in Fe3+-UV- aliphatic/phenolic carboxyl acids systems, and the degradation can be significantly influenced by different physical chemical properties of the organic acids. In this study, a density function theory (DFT) approach combined with multilinear regression analysis demonstrates that the lowest unoccupied molecular orbital energy (ELUMO) significantly negatively influenced DEP degradation. The correlation coefficient of the regression is −19.3 mM L−1 h−1. The standardized partial correlation coefficient is −0.674. The aliphatic acids group has higher catalytic ability than the phenolic carboxyl acids group, and by shifting the dominant LUMO configuration from C3s3d to Fe4s3d orbitals, Fe3+ significantly accelerates the catalytic reactions of the aliphatic acids/UV systems. Further analysis demonstrates that electron withdrawing hydroxyl group on the aliphatic acids increases the photo catalytic effects of aliphatic acids/UV system. This study highlights the important role of ELUMO of organic acids on their photocatalytic ability towards degradation of organic pollutants.

Bioreactor microbial ecosystems with differentiated methanogenic phenol biodegradation and competitive metabolic pathways unraveled with genome-resolved metagenomics

BackgroundMethanogenic biodegradation of aromatic compounds depends on syntrophic metabolism. However, metabolic enzymes and pathways of uncultured microorganisms and their ecological interactions with methanogenic consortia are unknown because of their resistance to isolation and limited genomic information.ResultsGenome-resolved metagenomics approaches were used to reconstruct and dissect 23 prokaryotic genomes from 37 and 20 °C methanogenic phenol-degrading reactors. Comparative genomic evidence suggests that temperature difference leads to the colonization of two distinct cooperative sub-communities that can respire sulfate/sulfite/sulfur or nitrate/nitrite compounds and compete for uptake of methanogenic substrates (e.g., acetate and hydrogen). This competition may differentiate methanogenesis. The uncultured ε-Proteobacterium G1, whose close relatives have broad ecological niches including the deep-sea vents, aquifers, sediment, limestone caves, spring, and anaerobic digesters, is implicated as a Sulfurovum-like facultative anaerobic diazotroph with metabolic versatility and remarkable environmental adaptability. We provide first genomic evidence for butyrate, alcohol, and carbohydrate utilization by a Chloroflexi T78 clade bacterium, and phenol carboxylation and assimilatory sulfite reduction in a Cryptanaerobacter bacterium.ConclusionGenome-resolved metagenomics enriches our view on the differentiation of microbial community composition, metabolic pathways, and ecological interactions in temperature-differentiated methanogenic phenol-degrading bioreactors. These findings suggest optimization strategies for methanogenesis on phenol, such as temperature control, protection from light, feed desulfurization, and hydrogen sulfide removal from bioreactors. Moreover, decoding genome-borne properties (e.g., antibiotic, arsenic, and heavy metal resistance) of uncultured bacteria help to bring up alternative schemes to isolate them.

Biochemical characterization and substrate profiling of a reversible 2,3-dihydroxybenzoic acid decarboxylase for biocatalytic Kolbe-Schmitt reaction.

Reversible benzoic acid decarboxylases are versatile biocatalysts by taking advantage of both decarboxylation and carboxylation reactions, especially for the biocatalytic Kolbe-Schmitt reaction. In the course of developing a benzoic acid decarboxylase tool-box, a putative benzoic acid decarboxylase gene from Fusarium oxysporum was heterologously over-expressed in Escherichia coli, the recombinant protein was purified and characterized. The purified enzyme exhibited relatively high catalytic efficiencies for the decarboxylation of 2, 3-dihydroxybenzoic acid and carboxylation of catechol (kcat/Km = 2.03 × 102 and 1.88 mM-1 min-1, respectively), and thus characterized as 2, 3-dihydroxybenzoic acid decarboxylase (2, 3-DHBD_Fo). The enzyme also catalyzed the decarboxylation of various substituted salicylic acids with different groups at varied positions except 5-position and the carboxylation of phenol and the substituted phenols. In a preparative reaction, catechol was carboxylated into 2, 3-dihydroxybenoic acid with 95% conversion by adding dodecyldimethylbenzylammonium chloride into the reaction system, and the product was isolated in 72% yield. These results demonstrate that 2, 3-DHBD_Fo is a valuable addition to the benzoic acid decarboxylase tool-box with potential practical applications.

Carboxylation of phenol and its derivatives with sodium ethyl carbonate

AbstractA comparison activity of phenol and its derivatives in carboxylation reaction with sodium ethyl carbonate was carried out (the ratio between substrate and sodium ethyl carbonate was 2:1, T=185°С, Pco

Amine-Mediated Enzymatic Carboxylation of Phenols Using CO2 as Substrate Increases Equilibrium Conversions and Reaction Rates.

A variety of strategies is applied to alleviate thermodynamic and kinetic limitations in biocatalytic carboxylation of metabolites in vivo. A key feature to consider in enzymatic carboxylations is the nature of the cosubstrate: CO2 or its hydrated form, bicarbonate. The substrate binding and activation mechanism determine what the actual carboxylation agent is. Dihydroxybenzoic acid (de)carboxylases catalyze the reversible regio-selective ortho-(de)carboxylation of phenolics. These enzymes have attracted considerable attention in the last 10 years due to their potential in substituting harsh conditions typical of chemical carboxylations (100-200 °C, 5-100 bar) with, ideally, greener ones (20-40 °C, 1 bar). They are reported to use bicarbonate as substrate, needed in large excess to overcome thermodynamic and kinetic limitations. Therefore, CO2 can be used as substrate by these enzymes only if it is converted into bicarbonate in situ. In this contribution, we report the simultaneous amine-mediated conversion of CO2 into bicarbonate and the ortho-carboxylation of different phenolic molecules catalyzed by 2,3-dihydroxybenzoic acid (de)carboxylase from Aspergillus oryzae. Our results show that under the newly developed conditions a significant thermodynamic (up to twofold increase in conversion) and kinetic improvement (up to approx. fivefold increase in rate) of the biocatalytic carboxylation of catechol is achieved.

Regioselective Enzymatic Carboxylation of Bioactive (Poly)phenols.

In order to extend the applicability of the regioselective enzymatic carboxylation of phenols, the substrate scope of o‐benzoic acid (de)carboxylases has been investigated towards complex molecules with an emphasis on flavouring agents and polyphenols possessing antioxidant properties. o‐Hydroxycarboxylic acid products were obtained with perfect regioselectivity, in moderate to excellent yields. The applicability of this method was proven by the regioselective bio‐carboxylation of resveratrol on a preparative scale with 95% yield.

ChemInform Abstract: Carboxylation of Phenols with CO2 at Atmospheric Pressure.

AbstractThis convenient and efficient method for the ortho‐carboxylation of phenols under atmospheric CO2 pressure provides an alternative to the Kolbe—Schmitt method, which requires very high pressures of CO2.