Important Fine Chemicals Research Articles

Simultaneous quantification of alkanolamines and their dehydrogenation products in aqueous samples using high-performance liquid chromatography with pre-column derivatization with 2,4-dinitrofluorobenzene

BackgroundDiethanolamine, monoethanolamine, iminodiacetic acid, and glycine are important fine chemical intermediates, often requiring simultaneous quantitative analysis in various applications. This presents the challenge of accurately quantifying multiple substances within a single sample. The catalytic dehydrogenation of diethanolamine and monoethanolamine has garnered significant research interest, yet no analytical method has been reported for the simultaneous quantification of reactants and products in the dehydrogenation reaction mixtures of different alkanolamines. ResultsA high-performance liquid chromatography (HPLC) method has been developed for the simultaneous quantification of diethanolamine (DEA), iminodiacetic acid (IDA), glycine (Gly), and monoethanolamine (MEA) in aqueous solutions using 2,4-dinitrofluorobenzene (DNFB) for pre-column derivatization. The method demonstrated excellent linearity, with correlation coefficients (R2) of 0.9999, 0.9997, and 0.9998 for IDA, DEA, and Gly, respectively. The detection limits (LODs) were 0.02, 0.08, and 0.01 mg L−1, respectively. The quantification limits (LOQs) were 0.06, 0.24, and 0.03 mg L−1, respectively. Spiked recovery rates ranged from 96.99 % to 104.32 %, with relative standard deviations (RSDs) between 0.70 % and 3.03 %. For MEA and Gly, the R2 values were 0.9970 and 0.9990, the LODs were 0.12 and 0.01 mg L−1, the LOQs were 0.36 and 0.03 mg L−1, and spiked recoveries ranged from 96.24 % to 104.82 %, with RSDs between 1.22 % and 3.68 %. Compared to other methods, this HPLC approach offers superior sensitivity, accuracy, and precision. SignificanceThis method provides a robust reference for the individual or simultaneous quantification of alkanolamines, glycine, and iminodiacetic acid in aqueous matrices. It offers new insights into the simultaneous analysis of alkanolamines with multiple organic acids in complex matrices. Additionally, the method can guide the optimization of catalytic dehydrogenation processes for alkanolamines, potentially extending the advantages of dehydrogenation catalysts to other reactions.

Selective oxidation of methyl glycolate to methyl glyoxylate with molecular oxygen catalyzed by VOx/γ-Al2O3

The selective oxidation of methyl glycolate (MG) to methyl glyoxylate (MGO) using molecular oxygen in a fixed-bed reactor represents a greener and more efficient alternative to the traditional batch processing for producing this important fine chemical and intermediate. Despite its potential, detailed understanding of this catalytic reaction is still limited. In our study, VOx/γ-Al2O3 catalysts were identified as effective for the reaction, but their performance strongly depended on the structure of VOx species. The optimal catalyst with nearly monolayer dispersed VOx achieved a high MG conversion of 91% and an MGO selectivity of 71%, alongside maintaining stability for 300 h without noticeable deactivation. At a low V loading of 0.6%, isolated VOx species were formed, exhibiting the highest turnover frequency (TOF) but the lowest MGO selectivity. Increasing the V loading to 3.9% resulted in a blend of less polymeric and isolated VOx species, which decreased the TOF but enhanced MGO selectivity to 59%. With the V loading ranging from 5% to 6.2%, monolayer dispersed VOx became dominant, yielding a lower TOF and the highest MGO selectivity. A further increase in V loading caused the emergence of crystalline V2O5, which seemed to act as a bystander. Moreover, the redox cycles of V4+ and V5+ over the VOx/γ-Al2O3 catalyst played an important role in the selective oxidation of MG to MGO, while the overoxidation of MG to CO2 might take place through the V3+/V4+ redox pairs, the extent of which was determined by the structure of VOx species. These insights are crucial for developing high-performance VOx-based catalysts for the production of MGO through the selective oxidation of MG.

Recombinant Amidases: Recent Insights and its Applications in the Production of Industrially Important Fine Chemicals.

The current research for the synthesis of industrially important fine chemicals is more inclined towards developing enzyme-based processes. The biotransformation reactions wherein microbial cells/enzymes are used, have become essential in making the process efficient, green, and economical. Amongst industrially important enzymes, amidase is one of the most versatile tools in biocatalysis and biotransformation reactions. It shows broad substrate specificity and sturdy functional characteristics because of its promiscuous nature. Further, advancement in the area led to the development of amidase recombinant systems, which are developed using biotechnology and enzyme engineering tools. Additionally, recombinant amidases may be instrumental in commercializing the synthesis of fine chemicals such as hydroxamic acids that have a significant pharmaceutical market. Hence, the present review focuses on highlighting and assimilating the tools and techniques used in developing recombinant systems followed by their applications.

Carbon-metal versus metal-metal synergistic mechanism of ethylene electro-oxidation via electrolysis of water on TM2N6 sites in graphene.

Acetaldehyde (AA) and ethylene oxide (EO) are important fine chemicals, and are also substrates with wide applications for high-value chemical products. Direct electrocatalytic oxidation of ethylene to AA and EO can avoid the untoward effects from harmful byproducts and high energy emissions. The most central intermediate state is the co-adsorption and coupling of ethylene and active oxygen intermediates (*O) at the active site(s), which is restricted by two factors: the stability of the *O intermediate generated during the electrolysis of water on the active site at a certain applied potential and pH range; and the lower kinetic energy barriers of the oxidation process based on the thermo-migration barrier from the *O intermediate to produce AA/EO. The benefit of two adjacent active atoms is more promising, since diverse adsorption and flexible catalytic sites may be provided for elementary reaction steps. Motivated by this strategy, we explored the feasibility of various homonuclear TM2N6@graphenes with dual-atomic-site catalysts (DASCs) for ethylene electro-oxidation through first-principles calculations via thermodynamic evaluation, analysis of the surface Pourbaix diagram, and kinetic evaluation. Two reaction mechanisms through C-TM versus TM-TM synergism were determined. Between them, a TM-TM mechanism on 4 TM2N6@graphenes and a C-TM mechanism on 5 TM2N6@graphenes are built. All 5 TM2N6@graphenes through the C-TM mechanism exhibit lower kinetic energy barriers for AA and EO generation than the 4 TM2N6@graphenes through the TM-TM mechanism. In particular, Pd2N6@graphene exhibits the most excellent catalytic activity, with energy barriers for generating AA and EO of only 0.02 and 0.65 eV at an applied potential of 1.77 V vs. RHE for the generation of an active oxygen intermediate. Electronic structure analysis indicates that the intrinsic C-TM mechanism is more advantageous than the TM-TM mechanism for ethylene electro-oxidation, and this study also provides valuable clues for further experimental exploration.

Highly selective oxidation of benzene to phenol with air at room temperature promoted by water

Phenol is one of the most important fine chemical intermediates in the synthesis of plastics and drugs with a market size of ca. $30b1 and the commercial production is via a two-step selective oxidation of benzene, requiring high energy input (high temperature and high pressure) in the presence of a corrosive acidic medium, and causing serious environmental issues2–5. Here we present a four-phase interface strategy with well-designed Pd@Cu nanoarchitecture decorated TiO2 as a catalyst in a suspension system. The optimised catalyst leads to a turnover number of 16,000–100,000 for phenol generation with respect to the active sites and an excellent selectivity of ca. 93%. Such unprecedented results are attributed to the efficient activation of benzene by the atomically Cu coated Pd nanoarchitecture, enhanced charge separation, and an oxidant-lean environment. The rational design of catalyst and reaction system provides a green pathway for the selective conversion of symmetric organic molecules.

Vibronic and Cationic Features of 2-Fluorobenzonitrile and 3-Fluorobenzonitrile Studied by REMPI and MATI Spectroscopy and Franck-Condon Simulations.

Fluorinated organic compounds have superior physicochemical properties than general organic compounds due to the strong C-F single bond; they are widely used in medicine, biology, pesticides, and materials science. In order to gain a deeper understanding of the physicochemical properties of fluorinated organic compounds, fluorinated aromatic compounds have been investigated by various spectroscopic techniques. 2-fluorobenzonitrile and 3-fluorobenzonitrile are important fine chemical intermediates and their excited state S1 and cationic ground state D0 vibrational features remain unknown. In this paper, we used two-color resonance two photon ionization (2-color REMPI) and mass analyzed threshold ionization (MATI) spectroscopy to study S1 and D0 state vibrational features of 2-fluorobenzonitrile and 3-fluorobenzonitrile. The precise excitation energy (band origin) and adiabatic ionization energy were determined to be 36,028 ± 2 cm-1 and 78,650 ± 5 cm-1 for 2-fluorobenzonitrile and 35,989 ± 2 cm-1 and 78,873 ± 5 cm-1 for 3-fluorobenzonitrile, respectively. The density functional theory (DFT) at the levels of RB3LYP/aug-cc-pvtz, TD-B3LYP/aug-cc-pvtz, and UB3LYP/aug-cc-pvtz were used to calculate the stable structures and vibrational frequencies for the ground state S0, excited state S1, and cationic ground state D0, respectively. Franck-Condon spectral simulations for transitions of S1 ← S0 and D0 ← S1 were performed based on the above DFT calculations. The theoretical and experimental results were in good agreement. The observed vibrational features in S1 and D0 states were assigned according to the simulated spectra and the comparison with structurally similar molecules. Several experimental findings and molecular features were discussed in detail.

Waste organic acid treatment with polyethyleneimine grafted polystyrene resin

AbstractOrganic acid is a kind of important fine chemicals with wide application, while impropriate discharges would cause serious damage to environment. In this report, two polyethyleneimine (PEI‐600, 1800) functionalized polystyrene (PS) resins were facilely prepared to remediate common organic acids. The heavier PEI‐1800 resulted in surprisingly lower nitrogen loading of PSPEI under optimal conditions due to more significant extra grafting. Therefore, PSPEI‐600 was used to adsorb two groups (aliphatic and aromatic) of eight common organic acids, and showed highest adsorptive capacities toward salicylic acid (SA) and trifluoroacetic acid (TFA). The adsorption of TFA was faster and was mainly due to strong acid–base interactions by forming ammonium carboxylate. SA possessed lower acidity, but its additional π‐π stacking and hydrogen bonding interactions with the PSPEI resin led to a slower but overall higher uptake. Kinetic studies indicated that both acid adsorptions conformed to pseudo‐second‐order kinetics, and the adsorption rate was controlled by intraparticle diffusion. The adsorptions followed Langmuir isotherms and were identified as a spontaneous endothermic process.

Thermal hazard characteristics and essential mechanism study of 1-hydroxybenzotriazole: Thermodynamic study combined DFT simulation

1-Hydroxybenzotriazole (HOBT) as an important fine chemical has been used as reactants, reagents or catalysts in over 6 million chemical synthesis reactions. The thermal decomposition characteristics of HOBT in non-isothermal, isothermal and adiabatic conditions were investigated through differential scanning calorimetry, thermogravimetric analyzer, and accelerating rate calorimeter. The apparent activation energy, thermal safety parameters, and the decomposition reaction pattern of HOBT pyrolysis were obtained based on adiabatic accelerating calorimeter experimental data. HOBT pyrolysis is a rapid exothermic process with large amounts of gas produced, and HOBT can decompose at a temperature substantially lower than the onset temperature. The severity and probability of HOBT runaway reaction were assessed. The pyrolysis mechanism paths of HOBT were explored by using TG-MS and TG-FTIR experiments couple with density functional theory calculations. The main decomposition products of HOBT were N2, NO, C2H2, C6H6, CO, HCN, and CO2 gases. This study provides guidance for safe production and application of HOBT, and formulating emergency plans for related hazards.

The novel boric acid modified material as micro separation plant for 1,3-BDO: Adsorption behavior and mechanism

As an important fine chemical, the research on adsorption separation of 1,3-butanediol (1,3-BDO) is still blank. In this study, the novel boric acid modified polystyrene material PS-BA-1 (boric acid content 1.169 mmol·g−1) was synthesized via introducing boric acid pinacol ester into the matrix and deprotection reaction. The adsorption capacity of PS-BA-1 for 1, 3-BDO reached 0.422 mmol·g−1 (water) and 0.947 mmol·g−1 (EtOH), while that of commercial resin CHA-111 was only 0.258 mmol·g−1 and 0.012 mmol·g−1. Interestingly, Freundlich equation could better describe the adsorption process in water (R2 ≥ 0.989) while Langmuir equation fit the EtOH system with higher correlation coefficients (R2 ≥ 0.990), respectively, indicating the adsorption process was reversible and non-ideal in water. Meanwhile, the kinetic adsorption could be better modeled by Pseudo-second-order equation (R2water = 0.991, R2EtOH = 0.990) and the k2-water (21.094*10-2) was higher than that of EtOH (3.516*10-2), demonstrating the mass transfer diffusion rate in water was faster. The breakthrough point for PS-BA-1 was 160 ∼ 162 BV in EtOH solution which was about twice of that of water system (83 ∼ 85 BV), and the column could be completely regenerated. Subsequently, PS-BA-1 was more conducive to the separation of 1,3-BDO in binary competitive experiments, indicating six-member borate esters was more stable binding structure. The computational chemistry further certified the adsorption selectivity between 1,3-BDO and PS-BA-1 as ΔG was lowest (-11.456 kcal·mol−1).

Biosynthesis of allantoin in Escherichia coli via screening a highly effective urate oxidase.

Allantoin is an important fine chemical that can be widely used in pharmaceutical, cosmetic and agricultural industries. Currently, allantoin is mainly produced by plant extraction or chemical synthesis. Due to the cost and environmental concerns, biosynthesis of allantoin from renewable feedstock is much more desirable. However, microbial production of allantoin from simple carbon sources has not yet been achieved so far. In this study, de novo biosynthesis of allantoin was achieved by constructing an artificial biosynthetic pathway. First, screening of efficient urate oxidases and xanthine dehydrogenases enabled allantoin production from hypoxanthine, a natural intermediate in purine metabolic pathway in Escherichia coli. Then, assemble of the entire pathway resulted in 13.9 mg/L allantoin from glucose in shake flask experiments. The titer was further improved to 639.8 mg/L by enhancing the supply of the precursor, redistribution of carbon flux, and reduction of acetate. Finally, scale-up production of allantoin was conducted in a 1-L fermentor under fed-batch culture conditions, which enabled the synthesis of 2360 mg/L allantoin, representing a 170-fold increase compared with the initial strain. This study not only demonstrates the potential for industrial production of allantoin, but also provides a bacterial platform for synthesis of other purines-derived high-value chemicals.

Establishing the Reaction Pathways of the Catalytic Conversion of Erythrulose to Sulphides of Alpha‐Hydroxy Thioesters and Esters

AbstractSulphides of alpha‐hydroxy thioesters and esters (SAH(T)Es) are important fine chemicals and have great potential as platform molecules. SAH(T)Es are typically synthesized from fossil sources while little is known regarding their synthesis from carbohydrates. We report our findings about the one‐pot chemocatalytic conversion of erythrulose (ERU) to SAH(T)Es. Sn, Mo and W chlorides were the most selective catalysts towards the synthesis of S‐butyl‐4‐butylthio‐2‐hydroxybutanethioate (BBTHBT) in 1‐BuSH. The selectivity towards BBTHBT was impacted by the formation of different thioacetals (TAs). The addition of either KOH, H2O or MeOH was effective to decrease TAs formation and increase selectivity towards BBTHBT (or its ester). A kinetic profile, in situ 13C NMR measurements and experiments at different temperatures complement our studies to unravel the complicated reaction network involved in the conversion of ERU to SAH(T)Es. This insight provides a solid foundation for future improvements in the sustainable synthesis of SAH(T)Es.

Glycerol transformation to pharmaceutically important aryloxypropanediols by microwave mediated synthesis

Green chemistry, so-called sustainable chemistry, alerts the chemist to design processes that minimize the exercise and production of the unsafe substance. The current work deals with the one pot, facile and fast synthesis of bioactive, arlyoxypropanediols solvent-free reaction of glycerol with DEC and phenol was performed under modified microwave oven in presence of K2CO3. Reaction products were analyzed by GC and GC-MS. 3-phenoxy-1,2-propanediol and 1,3-diphenoxy-2-propanol were obtained as major and minor product. Reaction is found to be strictly chemoselective via transesterification of glycerol and DEC resulting in formation of in-situ cyclic carbonate. The simplicity, formability, and homogeneity of the reaction design under microwave heating were better than those prepared under conventional heating. The present investigation of glycerol conversion to aryloxypropanediols gives a clear insight into the effective use of glycerol towards pharmacologically important fine chemical. Thus microwave synthesis proved to be efficient, by faster reaction rate with high yield, with desired products and low energy consumption. In addition application of microwave mediated synthetic procedures for synthesis of pharmacologically active aryloxypropanediols will be boon towards industrial application.

Metabolic engineering of Escherichia coli for production of hydroxytyrosol

Hydroxytyrosol is an important fine chemical and is widely used in food and medicine as a natural antioxidant. Production of hydroxytyrosol through synthetic biology is of important significance. Here we cloned and functionally characterized a hydroxylase encoding gene HpaBC from Escherichia coli BL21, and both subunits of this enzyme can be successfully expressed to convert the tyrosol into hydroxytyrosol. A HpaBC gene integration expression cassette under the tac promoter was constructed, and integrated into the genome of a tyrosol hyper-producing E. coli YMG5A*R using CRISPR-Cas9 technology. Meanwhile, the pathway for production of acetic acid was deleted, resulting in a recombinant strain YMGRD1H1. Shake flask fermentation showed that strain YMGRD1H1 can directly use glucose to produce hydroxytyrosol, reaching a titer of 1.81 g/L, and nearly no by-products were detected. A titer of 2.95 g/L was achieved in a fed-batch fermentation conducted in a 5 L fermenter, which is the highest titer for the de novo synthesis of hydroxytyrosol from glucose reported to date. Production of hydroxytyrosol by engineered E. coli lays a foundation for further construction of hydroxytyrosol cell factories with industrial application potential, adding another example for microbial manufacturing of aromatic compounds.

Chemical Fixation of Carbon Dioxide by Heterogeneous Porous Catalysts

AbstractAs the ultimate carbon emission of the combustion process, carbon dioxide (CO2) is a serious environmental hazard in increasing the global climate temperature through the greenhouse effect. Porous heterogeneous catalysts have drawn huge interest for carbon capture and in the past decades; significant developments can be observed in their fabrication and implementation for CO2 capture and conversion. In this context, the emerging development in major porous heterogeneous catalysts such as MOFs, COFs, metal oxides etc. for CO2 capture and conversion are discussed. Their physiochemical properties and their influence on the efficiency for CO2 capture and conversion are enlightened. The review provides a concise report on various types of heterogeneous catalysts, current trends, their application in CO2 reduction and fixation for the synthesis of fuels and other important fine chemicals and future research directions for the deployment of porous heterogeneous catalysts in Carbon dioxide capture and conversion.

Production of γ-aminobutyric acid from monosodium glutamate using Escherichia coli whole-cell biocatalysis with glutamate decarboxylase from Lactobacillus brevis KCTC 3498

γ-Aminobutyric acid (GABA), an important fine chemical in pharmacotherapy and food industries, is used as a novel material in the nylon industry and has attracted attention for its potential application in large scale production. Search for new genes and strains, development of efficient reaction systems, such as fermentation and bioconversion, and use of cheap starting material like monosodium glutamate (MSG) can make GABA production using less expensive bulk chemicals possible. Therefore, in this study, we constructed a recombinant Escherichia coli whole-cell system for GABA production that expressed glutamate decarboxylase (GAD) from Lactobacillus brevis and used MSG as the starting material. We also optimized the reaction conditions for MSG to GABA conversion, such as citrate buffer concentration, pyridoxal 5′te concentration, temperature, MSG concentration, and cell density (OD600). The optimized whole-cell system converted MSG to GABA via seven repetitive cycles resulting in an average conversion rate of 86% (71.7 mM/h) within 42 h.

Chemoselective Hydrogenation of Functionalized Nitroarenes into Anilines by Supported Molybdenum Catalysts

AbstractAnilines are the most important fine chemicals that have been widely used as the intermediates of industrial products. Herein, a new series of nanostructured Mo‐based catalysts were reported, such as MoOx/ZSM‐5(25), MoOx/ZSM‐5(50) and MoOx/SBA‐15, which can serve as efficient catalysts in the hydrogenation of nitroarenes by using hydrogen as the reducing reagent to afford functionalized anilines. Those catalysts showed both excellent activity and high chemoselectivity of the nitro group even though other reducible groups (C−X, C=C, C=O and C≡N) were exiting. This protocol constitutes an economically responsible pathway for the synthesis of anilines in high yields, good functional group compatibility and high chemselectivity.

Oxidative esterification of acetol with methanol to methyl pyruvate over hydroxyapatite supported gold catalyst: Essential roles of acid-base properties

Acetol is a major light oxygenate and readily produced from staged or fast pyrolysis of lignocellulose biomass. Herein we report that acetol can be selectively converted to methyl pyruvate, an important fine chemical, through oxidative esterification over Au-based catalysts. Detailed experimental studies showed that Au on amphoteric supports with appropriate strength and balanced ratio of acid and base sites can facilitate the desired oxidative-esterification pathway without accelerating undesired aldol-condensation or Cannizzaro reactions. In particular, hydroxyapatite (with a Ca/P ratio of 1.62) supported Au achieved 87% selectivity to methyl pyruvate at an acetol conversion of 62%. Au/hydroxyapatite (ratio of Ca/P = 1.62) catalyst exhibits superior performance toward the production of methyl pyruvate from biomass-derived acetol, where the featured acid-base properties in hydroxyapatite play an indispensable role.

A novel approach towards chemoselective reduction of nitro to amine

Chemo selective reduction of a wide range of aromatic nitro compound has been performed by using inexpensive Zn powder and CuSO4 system in water medium at room temperature. This system has high tolerance to other highly reducible groups present in nitro substance along with high conversation and selectivity. This chemo-selective reduction also provides a facile root for the synthesis of other industrially important fine chemicals or biologically important compounds where other highly reducible groups are present in close proximity to the targeted nitro groups.

Microwave‐Assisted Efficient One‐Pot Multi‐Component Synthesis of Octahydroquinazolinone Derivatives Catalyzed by Cu@Ag Core‐Shell Nanoparticle

AbstractCore‐shell Cu@Ag nanocatalyst have been synthesized via a two‐step thermal decomposition and galvanic displacement reaction. The nanocatalyst was intensively characterized by various analytical techniques. The formation of core‐shell nanoparticle (NPs) was initially confirmed by UV‐vis analysis followed by high resolution transmission electron microscopy (HRTEM) micrograph with Energy Dispersive X‐ray spectroscopy (EDS) mapping and line scan. This catalyst was found to be a highly efficient catalyst for the synthesis of octahydroquinazolinones. Compared with others, core‐shell nanoparticle of Cu@Ag shows better catalytic activity and much efficiency with high yield of product in less time. The higher activity of Cu@Ag core‐shell nanoparticles can be attributed to the increased oxidation stability of Cu nanoparticles by placing it in the core, lattice contraction and synergistic effect between the two metals. In this study, aromatic aldehydes with various functional groups were employed for the synthesis of octahydroquinazolinones. Later, the catalyst was found to be recyclable upto 5 cycles without any significant loss of activity. Our studies provide a platform for designing other potential core‐shell catalyst for the synthesis of biologically important fine chemicals.

Selective oxidation of monoethanolamine to glycine over supported gold catalysts: The influence of support and the promoting effect of polyvinyl alcohol

Glycine is an important fine chemical used in many fields, and the traditional synthetic methods like Strecker synthesis and ammoniation of chloroacetic acid use highly toxic reagents or produce equal molar byproducts. Herein, selective aerobic oxidation of monoethanolamine (MEA) to glycine using Au catalysts supported on various supports, including Al2O3, SiO2, TiO2, ZnO, and ZrO2, was investigated and the correlation between acid-base properties of the catalysts and catalytic performance was established. Catalysts with higher base content exhibited higher initial activity and that with lower acid content gave higher glycine selectivity. The influence of preparation methods was revealed using Au/ZrO2 with the best catalytic performance and it was demonstrated that the presence of polyvinyl alcohol (PVA) has a significant promoting effect. In-situ FTIR and 1H NMR analysis revealed that the hydrogen bonds between PVA and MEA can enhance adsorption of MEA on catalysts, resulting in doubled turnover frequency (TOF) and improved MEA conversion; and the preferential hydrogen bonds between the amino group of MEA and the hydroxyl of PVA can prevent the coordination of amino group with Au nanoparticles, favoring reaction of the hydroxyl group of MEA on the active sites, accounting for the enhanced glycine selectivity. The reaction conditions were optimized and the optimal yield of glycine was 95%.