Synthesis Of Adipic Acid Research Articles

Tin-Based Keggin-Type Phosphomolybdate and Silicomolybdate as Catalysts for the Green Synthesis of Adipic Acid

The catalytic activity of two series of Keggin-type salts of formula Cs4-xSnxSiMo12O40 (x: 0.5 and 1) and Cs3-xSnxPMo12O40 (x: 0.25-1) was examined in the liquid phase cyclohexanone oxidation to adipic acid (AA) in the solvent absence. The materials were prepared and characterized by FTIR, UV-Vis and SEM. The adipic acid synthesis was carried out at 90°C in presence of hydrogen peroxide (30%), a green oxidant that produces only water as by-product. The effects of catalyst/substrate molar ratios and time reaction on dipic acid yields were studied. The results of this study showed that the POM-H2O2 system was found to be efficient for the production of adipic acid from the oxidation of cyclohexanone and the yields were closely dependent on the operating conditions. The highest AA yield (55%) was obtained with Cs2Sn0.5PMo12O40 using a catalyst/substrate molar ratio of 3.7×10-3 and a reaction time of 20h.

Reaction-controlled Pickering interfacial catalysis: A green route to produce crystalline adipic acid under solvent-free conditions

The pursuit of a greener adipic acid synthesis process, aiming to replace the highly polluting nitric acid oxidation method, has been a longstanding endeavor in both academic and industrial spheres. In this study, we present a reaction-controlled Pickering interfacial catalysis system, enabling the efficient oxidation of cyclohexene to adipic acid using 30 wt% hydrogen peroxide without the involvement of organic solvents. Following the reaction, the system spontaneously undergoes demulsification, facilitating easy recovery of catalyst particles via simple filtration, followed by product separation through cooling-induced crystallization. Employing high speed microscopic imaging for in-situ characterization of interfacial properties, we elucidate the influence of reaction conditions on interfacial properties and catalytic performance. The reaction-controlled Pickering interfacial catalysis system demonstrated herein offers a novel and industrially feasible strategy for developing green adipic acid synthesis route.

Sustainable Adipic Acid Production via Paired Electrolysis of Lignin-Derived Phenolic Compounds with Water as Hydrogen and Oxygen Sources.

Adipic acid (AA) is an important feedstock for nylon polymers and is industrially produced from fossil-derived aromatics via thermocatalysis. However, this process consumes explosive H2 and corrosive HNO3 as reductants and oxidants, respectively. Here, we report the direct synthesis of AA from lignin-derived phenolic compounds via paired electrolysis using bimetallic cooperative catalysts. At the cathode, phenol is hydrogenated on PtAu catalysts to form ketone-alcohol (KA) oil with 92% yield and 43% Faradaic efficiency (FE). At the anode, KA is electrooxidized into AA on CuCo2O4 catalysts, achieving a maximum of 85% yield and 84% FE. Experimental and theoretical studies reveal that the excellent catalytic activity can be ascribed to the enhanced absorption and activation capability of reactants on the bimetallic cooperative catalysts. A two-electrode flow electrolyzer for AA synthesis realizes a stable electrolysis at 2.5 A for over 200 h as well as 38.5% yield and 70.2% selectivity. This study offers a green and sustainable route for AA synthesis from lignin via paired electrolysis.

Direct synthesis of α,ω-dicarboxylic acids via dicarbonylation of cyclic ethers

α,ω-Dicarboxylic acids are important intermediates for the preparation of polyamides, polyesters and polyurethanes. However, their production pathways are limited and usually suffer from low efficiency and environmental problems. Here, we report an innovative approach to synthesize C+2 dicarboxylic acids directly from cyclic ethers by dicarbonylation. Different from the general findings that C+1 monocarboxylic acids are produced by carbonylation of cyclic ethers involving alkene intermediates, in this work, by manipulating the reaction system with RhCl3 and iodine in acetic acid, diiodide-substituted intermediates were selectively formed and subsequently converted to dicarboxylic acids in the presence of H2 and CO. As high as 84% yield of adipic acid was obtained directly from tetrahydrofuran. This catalytic system is applicable not only to a wide variety of cyclic ethers but also to different primary diols to synthesize C2-elongated α,ω-dicarboxylic acids. This work provides a novel dicarbonylation strategy for the efficient synthesis of adipic acid, glutaric acid and other important α,ω-dicarboxylic acids (such as 1,7-heptanedioic acid and 1,8-octanedioic acid) that are still not easily synthesized by other methods.

Regioselectivity in Carbonylation of Pentenoic Acid to Synthesize Cyclic Anhydrides

AbstractPentenoic acids (PEA) obtained from biomass‐derived γ‐valerolactone (GVL) can serve as a platform for sustainable and atom‐economic synthesis of adipic acid and its derivatives. Herein, the results are reported on the cyclocarbonylation reaction of PEA to synthesize five‐ (5 a), six‐ (6 a), or seven‐membered (7 a) cyclic anhydrides, with the aim to drive the reaction towards 7 a, a potential intermediate to caprolactam. Carbonylation of 4‐PEA yielded up to 73 % cyclic anhydrides, 7 a and 6 a in ratio 79 : 21. However, from 3‐PEA the same palladium‐based catalytic system in the absence of strong acids yielded 61 % 6 a and 5 a (41 : 59), indicating the inability of the catalyst to force isomerization. Isomerization, which is essential to obtain 7 a from a mixture of PEA isomers derived from GVL, does occur in presence of strong acids; however, this led predominantly to formation of smaller rings (6 a and 5 a) from 4‐PEA. Catalytic systems containing ligands with bulky tert‐butyl substituents yielded 6 a and trace amounts of 7 a. Although 7 a can be obtained from 4‐PEA in reasonable selectivity, there still remains a challenge to selectively synthesize 7 a from a mixture of PEA isomers.

Microbial Upcycling of Waste PET to Adipic Acid.

Microorganisms can be genetically engineered to transform abundant waste feedstocks into value-added small molecules that would otherwise be manufactured from diminishing fossil resources. Herein, we report the first one-pot bio-upcycling of PET plastic waste into the prolific platform petrochemical and nylon precursor adipic acid in the bacterium Escherichia coli. Optimizing heterologous gene expression and enzyme activity enabled increased flux through the de novo pathway, and immobilization of whole cells in alginate hydrogels increased the stability of the rate-limiting enoate reductase BcER. The pathway enzymes were also interfaced with hydrogen gas generated by engineered E. coli DD-2 in combination with a biocompatible Pd catalyst to enable adipic acid synthesis from metabolic cis,cis-muconic acid. Together, these optimizations resulted in a one-pot conversion to adipic acid from terephthalic acid, including terephthalate samples isolated from industrial PET waste and a post-consumer plastic bottle.

Pd/HAP Catalyzed Synthesis of Adipic Acid from 1,6‐Hexanediol under Aerial Base‐free Conditions

AbstractAdipic acid (AA), an important precursor to produce nylon‐6, nylon‐6,6, and polyurethanes, can be synthesized from biomass‐derived 1,6‐hexanediol (HDO). Herein, we examined the selective oxidation of 1,6‐hexanediol to adipic acid over Pd/support (support‐ Rice husk ash (RHA), TiO2, C, ZnO, Al2O3, La2O3, Mg(OH)2, and hydroxyapatite (HAP)) catalyst in water at 70 °C under base‐free conditions. Pd/HAP exhibited high catalytic activity among the catalysts explored, affording adipic acid (AA) selectively in 89 % yield with complete conversion of HDO. Investigating these Pd/support catalysts and several control experiments inferred that the basicity of the HAP support concertedly with Pd nanoparticle participated in achieving efficient aerial oxidation of HDO to AA, and hence avoided the need for any additional base additives. Advantageously, Pd/HAP exhibited high activity for gram‐scale reactions and long‐term stability during reusing the catalyst for several cycles without any considerable loss in the catalytic activity.

Metabolic Engineering for Effective Synthesis of 2-Hydroxyadipate.

Adipic acid is an important monomer in the synthesis of nylon-6,6. In recent years, the biosynthesis of adipic acid has received more and more attention. The pathway with l-lysine as a precursor has potential for adipic acid synthesis, and 2-hydroxyadipate is a key intermediate metabolite in this pathway. In this Letter, the biosynthesis pathway of 2-hydroxyadipate was constructed in Escherichia coli. Through enhancement of precursor synthesis and cofactors regulation, 7.11 g/L of 2-hydroxyadipate was produced in the 5 L bioreactor, which verified the scale-up potential of 2-hydroxyadipate production. Furthermore, 11.1 g/L of 2-hydroxyadipate was produced in the 5 L bioreactor on the basis of potential optimization strategies via transcriptome analysis. This is the first time for the biosynthesis of 2-hydroxyadipate. The results lay a solid foundation for the biosynthesis of adipic acid and the production of bionylon.

Toward the use of mixed microbial cultures for the biological production of adipic and levulinic acid.

Biological synthesis of high added-value compounds like adipic acid (AA), levulinic acid (LA), or polyhydroxybutyrate (PHB) using pure culture has been separately reported. However, pure culture requires sterile conditions and the use of specific carbon sources resulting in high operating costs. Different alternatives based on the use of mixed microbial cultures (MMC) have been explored to resolve this problem. MMC have been widely reported for the production of PHB, but scarcely reported for LA production and never for AA synthesis. This work presents a novel strategy for the co-production of AA LA, and PHB using MMC. The strategy consists in selecting an MMC producer of AA, LA and PHB from an inoculum obtained from a wastewater treatment plant, which is then subjected to the feast and famine culture strategy in a sequential batch reactor, coupled with a batch reactor step to enhance the accumulation of AA and LA. The results showed that the MMC could produce a 16 ± 2, 23 ± 1 and 5 ± %1 (g compound/g volatile solids) of AA, LA and PHB, respectively, using a non-fermented residual biomass rich in pentose, namely synthetic hemicellulose hydrolysate (SHH) as the carbon source. These results contribute to generating future research to better understand and optimise the biosynthesis of these compounds by MMC.

The Effect of Glyoxylate Shunt Inactivation on Biosynthesis of Adipic Acid through Inverted Fatty Acid β-Oxidation by Escherichia coli Strains

Using Escherichia coli MG1655 lacIQ, ∆ackA-pta, ∆poxB, ∆ldhA, ∆adhE, ∆fadE, PL-SDφ10-atoB, Ptrc-ideal-4-SDφ10-fadB, PL-SDφ10-tesB, ∆yciA as a core strain, derivatives capable of synthesizing adipic acid from glucose through the inverted fatty acid β-oxidation pathway were obtained. Biosynthesis of the target compound by recombinants was ensured by the primary condensation of acetyl-CoA and succinyl-CoA by 3-oxoacyl-CoA thiolase PaaJ and the catalysis of the final reaction of the cycle by acyl-CoA dehydrogenases FadE and FabI. Deletion in the strains of sucCD genes encoding components of succinyl-CoA synthase did not increase the relative intracellular availability of succinyl-CoA for target biosynthetic reactions and did not lead to an increase in adipic acid accumulation by the recombinants. The secretion of succinic and malic acids by the strains with an impaired tricarboxylic acid cycle remained almost unchanged, indicating the activity in the cells of glyoxylate shunt reactions that compete with the cycle reactions for isocitrate, required for succinyl-CoA formation. When isocitrate lyase, malate synthases A and G, and bifunctional kinase/phosphatase of isocitrate dehydrogenase were inactivated in strains due to deletion of the aceBAK operon genes and glcB, adipic acid synthesis by recombinants increased three-fold and reached 0.33 mM.

Effect of the Glyoxylate Shunt Inactivation on Biosynthesis of Adipic Acid Through the Inverted Fatty Acid β-oxidation by <i>Escherichia coli</i> Strains

Using Escherichia coli MG1655 lacIQ, ∆ackA-pta, ∆poxB, ∆ldhA, ∆adhE, ∆fadE, PL-SDφ10-atoB, Ptrc-ideal-4-SDφ10-fadB, PL-SDφ10-tesB, ∆yciA as a core strain, the derivatives capable of synthesizing adipic acid from glucose through the inverted fatty acid β-oxidation pathway were obtained. Biosynthesis of the target compound by recombinants was ensured upon the primary condensation of acetyl-CoA and succinyl-CoA by 3-oxoacyl-CoA thiolase PaaJ and the catalysis of the final reaction of the cycle by acyl-CoA dehydrogenases FadE and FabI. Deletion in the strains of sucCD genes encoding components of succinyl-CoA synthase did not increase the relative intracellular availability of succinyl-CoA for target biosynthetic reactions and did not lead to an increase in adipic acid accumulation by the recombinants. The secretion of succinic and malic acids by the strains with an impaired tricarboxylic acid cycle remained almost unchanged, indicating the activity in the cells of glyoxylate shunt reactions that compete with the cycle reactions for isocitrate, required for succinyl-CoA formation. When isocitrate lyase, malate synthases A and G, and bifunctional kinase/phosphatase isocitrate dehydrogenase were inactivated in strains due to deletion of the aceBAK operon genes and glcB, adipic acid synthesis by recombinants increased threefold and reached 0.33 mM.

The Effects of Acid and Hydrogen Peroxide Stabilizer on the Thermal Hazard of Adipic Acid Green Synthesis

The synthesis of adipic acid, which is formed by the reaction of cyclohexene oxidized by hydrogen peroxide (H2O2), is hazardous because of the highly exothermic nature of this reaction and H2O2 decomposition. The objective of this comprehensive study was to investigate and illustrate the effects of sulfuric acid (H2SO4) and H2O2 stabilizer (EDTA) on the thermal hazard of H2O2 decomposition and the green synthesis of adipic acid, which also provided a reference to reduce the risk of the reactions. Various calorimetry techniques were carried out to characterize the exothermic behavior of the reactions. An HPLC device was used to characterize the yield of adipic acid and the conversion rate of the raw materials, cyclohexene and H2O2. Meanwhile, density functional theory calculations were performed to understand the reaction mechanism and the associated energies of H2O2 decomposition catalyzed by sodium tungstate dihydrate (Na2WO4·2H2O). Finally, combined with the calorimetry results, the risk of the adipic acid synthesis reaction was assessed using the intrinsic control index method (ITHI). The results show that the addition of H2SO4 and EDTA can reduce the exothermic heat of the H2O2 decomposition reaction and the green synthesis reaction of adipic acid. The yield of adipic acid was also increased. The hazard level of stage A was IV, and to remove more reaction heat, it was recommended to enhance the reflux cooling of stage A. The hazard level of stage B was I, which was very low and no further measures could be taken.

Oxidation of Cyclohexane/Cyclohexanone Mixture with Oxygen as Alternative Method of Adipic Acid Synthesis

Herein, an alternative method for adipic acid (AA) synthesis of industrial importance has been reported. The proposed novel method involves the one-step, solvent-free oxidation of a cyclohexane/cyclohexanone (CH/CH=O) mixture, with a cheap oxidizing agent such as O2 or air under mild conditions in the presence of N-hydroxyphtalimide (NHPI) and transition metals as catalysts. It has been showed that CH/CH=O mixture under applied mild conditions oxidized faster than CH and CH=O separately. This was due to the greater oxidizability of CH=O compared to CH. The peroxyl radicals formed by CH=O oxidation initiated the oxidation of the less reactive CH. Additionally, CH=O increased the polarity of the reaction mixture, promoting the solubility of NHPI. The influence of type and amount of catalyst, cyclohexane to cyclohexanone ratio, temperature, time, type of oxidizing agent on the composition of CH/CH=O oxidation products have been reported.

H3PMo12O40@MOF as a New Catalytic System for Cycloxexanone Oxidation to Adipic Acid

Keggin-type phosphomolibdic acid (H3PMo12O40, PMo12) encapsulated in the mesocages of chromium-based terephthalate metal–organic framework (MIL-101), was established to be an active and new green catalyst for the adipic acid (AA) synthesis via cyclohexanone (-One) oxidation in free solvent conditions and hydrogen peroxide as green oxidant. In this paper, we wish to report the synthesis of MIL-101 with different high loadings of the PMo12 nanocrystals incorporated within the large pores of MIL-101. Two and five POMs per large cavity can be incorporated into the matrix of MIL-101 respectively, xH3PMo12@ MIL101 with x=0, 2 and 5, they were characterized by several physic-chemical technics, then investigated in the reaction oxidation with 30 mmol –One at 90 ° C for 20h. A sequenced addition of 0.5ml of H2O2 (30%) was made every 30 min. The catalysts have shown good activity and the purity of AA was invistigeted by 1H and 13C NMR.

A transparent self-healable multistimuli-responsive novel supramolecular Co(II)-metallogel derived from adipic acid: Effective hole transport layer for polymer solar cells

A fascinating approach for the instantaneous synthesis of adipic acid as a low molecular weight gelator and cobalt(II)-ion based metallogel through one-shot mixing in N,N-dimethyl formamide medium has been attained under ambient condition and at room temperature. The rheological study was applied to investigate the mechanical property of the synthesized Co(II)-metallogel. Through thixotropic experiments, the self-healing ability of the synthesised cobalt metallogel is established. The layered structure of the metallogel was envisaged through FESEM and the present elements were characterized through EDX mapping investigations. The potential metallogel formation approach has been examined using FT-IR, and the Powder X-ray diffraction pattern verifies the crystallinity of the Co(II)-metallogel's xerogel form. The absorption characteristics of this gel showed transparent in the visible to near infrared region of solar spectrum. The semiconducting property of the metallogel has been further confirmed and verified and with electronic device characterization and charge career mobility evaluation and found that this gel exhibits quite high hole mobility. We have used this as hole transport layer for polymer solar cells using PM6:Y6 as active layer and compared with the MoO3 as hole transport layer. The power conversion efficiency for Co(II)-metallogel (Co-AD) as hole transport layer 13.15 % which is higher than that for MoO3 counterpart (12.17 %). The higher power conversion efficiency for Co(II)-metallogel is associated with enhanced value of fill factor owing to the more efficient charge transport and suppressed charge recombination.

Concepts of Heterogeneously Catalyzed Liquid‐Phase Oxidation of Cyclohexene with tert‐Butyl Hydroperoxide, Hydrogen Peroxide and Molecular Oxygen

AbstractThe oxidation of hydrocarbons is of great significance for the chemical industry as it provides access to valuable functionalized chemicals. The oxidation of cyclohexene has raised much interest because it enables the direct synthesis of adipic acid, which is an important building block in polymer chemistry. However, the selective oxidation of cyclohexene is rather challenging due to its two reactive centers so that epoxidation or allylic oxidation may occur leading to a variety of products. Whether the oxidation takes place at the allylic C−H bond or at the C=C bond is strongly influenced by the chosen oxidant and catalyst, and different reaction mechanisms can occur. Therefore, this concept article aims at giving a broad overview of the recent advances in the selective cyclohexene oxidation over heterogeneous transition metal‐based catalysts using environmentally benign oxidants like tert‐butyl hydroperoxide, H2O2 and molecular O2.

Identification of the reaction network for the synthesis of adipic acid using machine learning coupling with target factor analysis

AbstractThis study investigated the reaction network of the oxidation of cyclohexanone with nitric acid through machine learning (ML) model coupling with target factor analysis (TFA). Experiments for the synthesis of adipic acid (AA) were carefully designed and carried out in a microreactor system. An artificial neural network (ANN) model was applied and optimized by training on experimental data. To assess the established ANN model, a comparison between the predicted concentrations of the products and those calculated with the power law kinetic model was implemented. TFA was then performed on both the experimental data and the data simulated by ANN for identifying the candidate reactions and finding out the temperature boundaries. Based on the identification results of the reaction network, the kinetic characteristics of this oxidation process under various operational conditions were further researched through the incremental approach and simultaneous approach.

Effect of thermal treatment on K3PW12O40 for cyclohexene oxidation reaction to adipic acid

The use of heteropolysalts in the cyclohexene oxidation reaction has shown good results, but there is still a significant solubility of this catalyst in the aqueous phase of the reaction medium which is not discussed in most articles dealing with this subject. A thermal treatment, such as calcination step, can significantly affect the properties of a catalyst, including its solubility, sedimentation and acidity. These effects are very important in batch reaction processes and frequently neglected. Thus, the main objective of this work was to study the effect of different calcination temperatures (200 and 600 °C) on the solubility and the acidity of Keggin-type catalysts (K3PW12O40). In addition, the effect of reaction temperature (65, 75 and 85 °C) on the conversion and distribution of products in the oxidation of cyclohexene with these two catalysts was analyzed. The heteropolysalts were characterized using XRD, Raman spectroscopy, N2 physisorption, SEM-EDS, acid-base titration and NH3-TPD. XRD and Raman results showed that the catalysts synthesis was carried out successfully and the thermal treatments did not affect the polyanion structures, even at the highest temperature (600 °C). When compared to the catalyst treated at 600 °C, the KPW-200 catalyst showed greater solubility in the reaction medium. However, it achieved 100% conversion and the highest yield of adipic acid (89%) at 75 °C, in addition to the highest density of acid sites. Tests were performed using the aqueous phase of the post-reaction solution to evaluate the occurrence of homogeneous catalysis under the same conditions. The results showed that, despite the solubilization of the catalyst, there was no adipic acid formation, only of intermediate compounds. Thus, the contribution of homogeneous catalysis in the synthesis of adipic acid is discarded, and the acidity of the catalyst seems to be the determining parameter in the formation of this product. Acidity can influence both the oxidation and hydrolysis steps present in the reaction mechanism and can justify these results.

Electrocatalytic synthesis of adipic acid coupled with H2 production enhanced by a ligand modification strategy

Adipic acid is an important building block of polymers, and is commercially produced by thermo-catalytic oxidation of ketone-alcohol oil (a mixture of cyclohexanol and cyclohexanone). However, this process heavily relies on the use of corrosive nitric acid while releases nitrous oxide as a potent greenhouse gas. Herein, we report an electrocatalytic strategy for the oxidation of cyclohexanone to adipic acid coupled with H2 production over a nickel hydroxide (Ni(OH)2) catalyst modified with sodium dodecyl sulfonate (SDS). The intercalated SDS facilitates the enrichment of immiscible cyclohexanone in aqueous medium, thus achieving 3.6-fold greater productivity of adipic acid and higher faradaic efficiency (FE) compared with pure Ni(OH)2 (93% versus 56%). This strategy is demonstrated effective for a variety of immiscible aldehydes and ketones in aqueous solution. Furthermore, we design a realistic two-electrode flow electrolyzer for electrooxidation of cyclohexanone coupling with H2 production, attaining adipic acid productivity of 4.7 mmol coupled with H2 productivity of 8.0 L at 0.8 A (corresponding to 30 mA cm−2) in 24 h.

Green synthesis of cyclohexanone to adipic acid over Fe–W oxides incorporated mesoporous carbon support

We have prepared iron and tungsten oxides incorporated mesoporous carbon (MC) catalysts using a simple hydrothermal methodology with different carbon sources, and the catalytic performance was investigated for cyclohexanone oxidation. An adequate amount of metal oxide loading has displayed a key role in the selective catalyst for adipic acid (AA) synthesis. The MC catalyst has shown its prime activity under the influence of redox properties of W5+/W6+ and Fe2+/Fe3+ as promoters. The 10%Fe 90%W-MC fructose as a carbon source catalyst has provided its best selectivity of 87% for AA at 120 °C.