Sulfur-containing Functional Groups Research Articles

Regulating desolvation and homogenized ion flux towards highly reversible dendrite-free zinc anode

Aqueous zinc ion batteries (AZIBs) are potential in the energy storage field, however, there are inherent disadvantages that seriously hinder their development, including the dissolution and structural collapse of cathode materials, Zn-dendrite growth, and side reactions at the anode interface. The cycling life and coulombic efficiency suffer from the latter two disadvantages, thus, many artificial interface layers have been prepared to address these issues. Herein, an organic molecule with four thiophene substitution groups, 1,3,5,9-Tetrathiophenylpyrene (TTP), was designed as an artificial layer to suppress dendrites and achieve uniform zinc deposition. This strategy prolonged the lifespan of symmetrical cells with an extremely small polarization voltage of 51 mV at 0.885 mA cm−2. In particular, the strong interaction between TTP and Zn atoms not only promoted the Zn desolvation but also modulated the Zn2+ transport. Ultimately, Zn-dendrite, hydrogen evolution reaction (HER), and side reactions were significantly inhibited. The full cells constructed with V2O5 delivered long-term cycling stability over 6500 cycles with a capacity retention of 80 % after 1250 cycles at 5 A g-1 and excellent rate performance. More importantly, the sulfur-containing functional groups in the organic materials were successfully utilized to resolve the issues of Zn anodes, demonstrating the promising prospects of this strategy.

Biopolymeric Ni3S4/Ag2S/TiO2/Calcium Alginate Aerogel for the Decontamination of Pharmaceutical Drug and Microbial Pollutants from Wastewater.

The ubiquitous presence of pharmaceutical drugs and microbes in the water is leading to the development of drug resistant microbes. Therefore, efficient materials that can remove or inactivate the drug and microbe contaminants are required. In this work, nickel sulfide/calcium alginate (Ni3S4/CA), silver sulfide/calcium alginate (Ag2S/CA), modified titanium dioxide/calcium alginate (TiO2/CA), and Ni3S4/Ag2S/TiO2/calcium alginate (Ni3S4/Ag2S/TiO2/CA) aerogels have been synthesized for the removal of the oxytetracycline (OTC) drug and microbial contaminants from real beverage industry wastewater. The results revealed that Ni3S4/Ag2S/TiO2/CA aerogel is highly efficient for OTC adsorption and inactivation of microbes compared to Ni3S4/CA, Ag2S/CA and TiO2/CA aerogels. The OTC adsorption depends greatly on the solution pH, and optimum OTC removal was observed at pH 6 in its zwitterionic (OTC±) form. The formation of H-bonding and n-π electron donor-acceptors is possible to a considerable extent due to the presence of the double bond benzene ring, oxygen and nitrogen, sulfur-containing functional groups on the OTC molecules, and the Ni3S4/Ag2S/TiO2/CA aerogel. Based on the statistical analysis, root-mean-square deviation (RMSD), chi square (χ2) values, and higher correlation coefficient (R2) values, the Redlich–Peterson isotherm model and Elovich kinetic model are most suited to modelling the OTC adsorption onto Ni3S4/Ag2S/TiO2/CA. The prepared aerogels’ excellent antimicrobial activity is observed in the dark and with solar light irradiation. The zone of inhibition analysis revealed that the antimicrobial activity of the aerogels is in the following order: Ni3S4/Ag2S/TiO2/CA > TiO2/CA > Ag2S/CA > Ni3S4/CA, respectively. Moreover, the antimicrobial results demonstrated that reactive oxygen species, electrons, and active radical species are responsible for growth inhibition and killing of the microbes. These results indicated that Ni3S4/Ag2S/TiO2/CA aerogel is highly efficient in decontaminating pollutants from wastewater.

Lignin-derived biochar solid acid catalyst for fructose conversion into 5-ethoxymethylfurfural

Lignin-derived biochar materials with acid functional groups (-COOH, –SO3H and –OH) were synthesized by carbonization of lignin (LigT) at T = (300, 400, 500) °C and mix ball-milling of the carbonized solids with thiomalic acid and partial oxidation of the functional solids with H2O2. Mix ball-milling promoted interactions between biochar CO and alkoxy C–O groups and thiomalic acid –COOH groups, which allowed H2O2 to convert covalently-bonded sulfur-containing functional groups on the biochars into Brønsted acid sites. The lignin-derived biochar solid acid materials were applied as catalysts to convert fructose into 5-ethoxymethylfurfural (EMF) and ethyl levulinate (EL) via 5-hydroxymethylfurfural (HMF) intermediate in ethanol solvent. Yields of HMF, EMF and EL reached 11%, 62% and 22%, respectively at 115 °C and 6 h with 100% conversion of fructose when the reaction was conducted with Lig300(S/C = 2)-SO3H, which had the highest total acidity in this work. The activation energy (70.9 kJ/mol) for conversion of fructose into HMF was lower than that for conversion of HMF into EMF (90.2 kJ/mol). The method for synthesizing sulfonated-containing biochars is green and efficient and the lignin-derived biochar solid acid catalysts are effective for converting renewable resources into platform chemicals.

Effect of chemical treatment of multi-walled carbon nanotubes on the specific capacitance of supercapacitors

To date, the research on carbon nanomaterials has progressed rapidly. More than 400 papers were written in 2021 on the application of carbon nanomaterials in various fields. The high demand for the use of such materials has increased due to a sharp increase in the demand for semiconductor materials and materials for supercapacitor electrodes and other electrical devices. Despite the unique physical properties of carbon nanomaterials, there are limitations to their use. To solve this problem, various methods of modifying the surface, both through chemical interactions and physical adsorption, were proposed. One of these methods is chemical modification. The evaluation of effect of chemical treatment parameters on the properties of carbon nanomaterials is an urgent task due to the fact that the chemistry of the processes is poorly understood. In this work, the effect of concentrated sulfuric and nitric acids on the change of specific surface area, elemental composition, composition of functional groups, and also on the change of specific capacitance was considered. It is believed that both the porosity and the functional groups formed during oxidation contribute to the change in specific capacitance. The specific surface area of all samples decreased on average by a factor of 1.5–3 after the chemical treatment. Different oxygen and sulfur-containing functional groups are observed after the chemical treatment. The highest specific capacitance of the treated carbon nanofibers was 114 F/g.

Catalysts for dehydration of isopropyl alcohol based on chlorinated carbon fiber

Gas-phase chlorination of carbon fiber based on polyacrylonitrile was performed and active chlorine-containing precursors were obtained, in which chlorine can be replaced by sulfur-containing functional groups. It is shown that chlorination of carbon fiber samples with carbon tetrachloride at temperatures of 300, 450 and 6000C in an argon stream leads to the introduction of 0.2–1.7 mmol g–1 of chlorine into the surface layer of the fiber. The thermodesorption properties of the modified carbon fiber samples were investigated by thermogravimetry and thermoprogrammed desorption with mass spectrometric registration of products. It was established that the obtained samples exhibit a relatively high thermal stability. The study conducted by means of thermoprogrammed desorption method showed that chlorine is desorbed from the surface in a wide temperature range (up to 8000C). It was found that the treatment of chlorinated samples with sulfur-containing reagents with subsequent oxidation produce the samples of carbon fiber with a concentration of sulfo-groups up to 0.3 mmol g–1, which are catalytically active in the dehydration reaction of isopropyl alcohol in the gas phase. The temperature of 50% conversion of isopropyl alcohol to propylene was used as a measure of catalytic activity. It was found that pre-chlorination leads to an increase in the catalytic activity of the fiber modified with sulfur-containing reagents: the temperature of 50% conversion of isopropyl alcohol to propylene is 215–2900C, depending on the concentration of sulfo-groups.

Recent Advances in Post-polymerization Modifications on Polypeptides: Synthesis and Applications.

Polypeptides, a kind of very promising biomaterial, have shown a wide range of applications due to their excellent biocompatibility, easy accessibility, and structural variability. To synthesize polypeptides with desired functions, post-polymerization modification (PPM) plays an important role in introducing novel chemical structure on their side-chains. The key to PPM strategy is to develop highly selective and efficient reactions that can couple the additional functional moieties with pre-installed side-chain functionalities on polypeptides. In this minireview, classic PPM approaches and their recent progresses are summarized and categorized into five sections, including various reactions on unsaturated alkyl, oxygen-, nitrogen-, sulfur-containing and other special functional groups. In addition, we also highlight the applications of the resultant structure-diversified polypeptides in the field of biomaterial.

Removing mercury from flue gas by sulfur-doped zeolite-templated carbon: Synthesize and adsorption mechanism

Elemental mercury is harmful to humanity and the ecological environment. It is a simple and feasible method to capture elemental mercury by carbon-based adsorbents. The purpose of this work is to develop zeolite-templated carbon with and without sulfur (ZTC and S-doped ZTC) and to explore their mercury adsorption performance. ZTC and S-doped ZTC were synthesized by chemical vapor deposition (CVD) method and their mercury adsorption performance were tested at 30 and 150 °C. Among all ZTC samples, BEA-ZTC-HS exhibited highest mercury removal efficiency (MRE) whose initial value was 99.99% (150 °C) and 97.39% (30 °C) and decreased to 96.63% and 89.15% after one hour mercury adsorption. The physical and chemical properties of the ZTC samples were characterized by various methods to explain the high MRE of BEA-ZTC-HS. The experimental results shown that BEA-ZTC-HS replicated the crystal structure of BEA zeolite faithfully and exhibited regular microporous structure and doesn’t have obvious elemental sulfur whose existence could block the micropores in ZTC. This was helpful to the mass transfer of Hg0 in ZTC. Moreover, the chemical properties of BEA-ZTC-HS shown that the introduced sulfur were mainly bonded to the carbon framework of ZTC in the form of thiophene, sulfone, sulfoxide and sulfonic acid. Those sulfur-containing functional groups provided main active sites for mercury capture and exhibited higher activity at 150 °C. Finally, Density Functional Theory (DFT) was used to reveal the adsorption mechanism of ZTC and S-doped ZTC on Hg0. Due to its good properties of regeneration, higher MRE, good thermal stability and low cost, BEA-ZTC-HS has a wide prospect for industrial application in the wide temperature ranges compared to the activated carbon injection technology.

The importance of sulfur-containing motifs in drug design and discovery

ABSTRACT Introduction Sulfur-containing functional groups are privileged motifs that occur in various pharmacologically effective substances and several natural products. Various functionalities are found with a sulfur atom at diverse oxidation states, as illustrated by thioether, sulfoxide, sulfone, sulfonamide, sulfamate, and sulfamide functions. They are valuable scaffolds in the field of medicinal chemistry and are part of a large array of approved drugs and clinical candidates. Area Covered Herein, the authors review the current research on the development of organosulfur-based drug discovery. This article also covers details of their roles in the new lead compounds reported in the literature over the past five years 2017-2021. Expert opinion Given its prominent role in medicinal chemistry and its importance in drug discovery, sulfur has attracted continuing interest and has been used in the design of various valuable compounds that demonstrate a variety of biological and pharmacological feature activities. Overall, sulfur’s role in medicinal chemistry continues to grow. However, many sulfur functionalities remain underused in small molecule drug discovery and deserve special attention in the armamentarium for treating diverse diseases. Research efforts are also still required for the development of a synthetic methodology for direct access to these functions and late-stage functionalization.

Garlic essential oil-based nanoemulsion carrier: Release and stability kinetics of volatile components.

An O/W nanoemulsion of garlic essential oil (GEO) at different oil‐to‐emulsion (O/E) ratios (5%, 10%, 15%, and 25%) was formulated to protect the volatile components of GEO. The effects of O/E ratios on the encapsulation efficiency (EE%) of volatile compounds and droplet size of nanoemulsions were studied. The results showed that with increasing in E/O ratio, droplet size increased while EE% decreased so that the droplet size was below 100 nm for all samples and the EE% was almost above 80% for most samples. The effects of various factors such as temperature (5°C–45°C), pH values (3–7), ionic strength (0–500 mM), and O/E ratios (5%–25%) on kinetic of nanoemulsions stability were studied. Reducing pH values and raising the temperature, ionic strength, and O/E ratios intensified the instability process and constant rate of instability in all nanoemulsions. The effects of temperature and O/E ratios on the release kinetics of volatile components were evaluated over time, and kinetic parameters such as release rate constant (k), Q10, and activation energy (Ea) were calculated in which results showed a zero‐degree model to describe the release kinetic behavior of most nanoemulsions. Both temperature and O/E ratios factors as well as their interaction (which had a synergistic effect) had a significant effect on increasing the release rate of volatiles so that the degree of reaction rate was changed from zero to the first order at simultaneous high levels of both factors. FT‐IR spectroscopy was carried out to study interactions among nanoemulsion ingredients. The presence of sulfur‐containing functional groups of garlic oil (thiosulphate, diallyl trisulfide, etc.) in nanoemulsions was confirmed by FT‐IR.

A Mechanistic Study of Wettability Alteration of Calcite as an Example of Carbonate Reservoirs Using Molecular Dynamics Simulation

Abstract It is common sense the wettability alteration in carbonate reservoirs stems from the oil–rock interactions; however, the exact oil component acting as the dominant role remains unclear. This study adopts molecular dynamics technology, takes {101¯4} calcite crystal surface as the mineral surface of carbonate reservoir, uses multiple single-component oils to characterize real crude oil, and conducts research on the wettability alteration of carbonate reservoirs. First, based on the chromatographic analysis results of a certain carbonate reservoir in the Middle East, the simulated oil is divided into polar and nonpolar components. Then, the Materials Studio software and the COMPASS force field were employed to study the natural wettability of the calcite surface, as well as the adsorption characteristic of different oil components and water on the surface of calcite. Results show that the surface of calcite in carbonate reservoirs is indeed water-wet under initial conditions, and the contact angle of calcite surface is equal to 68.47 deg ± 3.6 deg. However, when the crude oil component contains groups of hydroxyl functional group, especially the strongly polar component with multiple hydroxyl functional groups, such as glycerol (GLYC), will cause the originally water-wet calcite surface becomes oil-wet. The main reason for the GLYC component altering the wettability of the calcite surface is hydrogen bonding and Coulomb interaction. Moreover, the results of centroid displacement of nine oil components shown that besides the GLYC component, the rest of the eight components, including the polar component of nitrogen-containing functional groups (Indole), sulfur-containing functional groups (Benzothiophene), as well as five nonpolar components, all migrate away from the calcite surface.

Characterization of nitrogen and sulfur migration during pressurized coal pyrolysis and oxy-fuel combustion

In the present work, pressurized coal pyrolysis and oxy-fuel combustion experiments were carried out in a pressurized drop tube furnace to investigate the migration and transformation characteristics of nitrogen and sulfur. The pyrolysis experiments showed that high pyrolysis pressure inhibited the release of nitrogen and sulfur. The content of oxidized nitrogen (N-X), pyrite, sulfide, sulfoxide and sulfate in char decreased, while the content of pyridine nitrogen (N-6), pyrrole nitrogen (N-5), quaternary nitrogen (N-Q), thiophene and sulfone in char increased with the increase of pyrolysis pressure. The elevated pyrolysis temperature was conducive to the decomposition of nitrogen and sulfur-containing functional groups, and it also promoted the conversion of nitrogen and sulfur to functional groups with high stability such as N-Q and thiophene. The release of volatiles and the decomposition of nitrogen and sulfur-containing functional groups in coal were promoted by CO2 gasification. The increase of the total CO2 gasification pressure led to more nitrogen and sulfur remaining in char. During pressurized oxy-fuel combustion in O2/CO2 atmosphere, the emissions of NO, NO2 and SO2 were lower than those in air combustion. The emissions of NO, NO2 and SO2 gradually decreased with the increase of pressure at air and oxy-fuel atmospheres. The increase of temperature increased the emissions of NO and SO2 at different pressures, but the NO2 emission decreased at elevated temperature. In addition, the emissions of NO and NO2 increased, but the emission of SO2 decreased with the increase of oxygen concentration.

Matching chemical properties to molecular biological activities opens a new perspective on l-ergothioneine.

l-ergothioneine is a low-molecular weight natural product, the chemical structure of which comprises oxygen-, nitrogen- and sulfur-containing functional groups. This gives l-ergothioneine specific physicochemical properties and allows a better understanding of its chemical reactivity, which is primarily due to the 2-thio-imidazole group. Here, a review is provided of how different modes of chemical reactivity account for the reported molecular biological activities of l-ergothioneine. By matching the physicochemical properties to the biological properties of l-ergothioneine, a new perspective of the function and the mode of action of this enigmatic molecule emerges.

Stabilization of lead and cadmium in soil by sulfur-iron functionalized biochar: Performance, mechanisms and microbial community evolution

Sulfur-iron functionalized biochar (BC-Fe-S) was designed by simultaneously supporting Fe2O3 nanoparticles and grafting sulfur-containing functional groups onto biochar to stabilize Pb and Cd in soil. The BC-Fe-S exhibited excellent stabilization performance for Pb and Cd with fast kinetic equilibrium within 5 days associating with pseudo-second-order model. The bioavailable-Pb and -Cd contents decreased by 59.22% and 70.28% with 3% BC-Fe-S treatment after 20 days of remediation. Speciation transformation analysis revealed that the increase of stabilization time and BC-Fe-S dosage with appropriate soil moisture and pH promoted toxicities decrease of Pb and Cd with transformation of labile fractions to more steady fractions. The labile fractions of Pb and Cd decreased by 12.22% and 16.21% with 3% BC-Fe-S treatment, and transformed to the residual speciation. Meanwhile, wetting-drying and freezing-thawing aging did not markedly alter the bioavailability of Pb and Cd, proving that the BC-Fe-S holds promise for stabilization of Pb and Cd in varying environmental conditions. 16S rRNA sequencing analysis demonstrated that the BC-Fe-S significantly improved diversity and composition of microbial community, especially increasing the relative abundance of heavy metal-resistant bacteria. Overall, these results suggested BC-Fe-S as a high-performance and environmental-friendly amendment with stability to remediate heavy metals polluted soil.

Investigation of ICP-MS/MS for total sulfur quantification in freshwater dissolved organic matter.

Sulfur-containing functional groups in dissolved organic matter (DOM) interact with trace metals, which in turn affects trace metal mobility and bioavailability in aquatic environments. Typical methods for identification and quantification of sulfur in DOM are costly, complex, and time intensive. Triple quadrupole inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) is capable of part per billion-level sulfur quantification in environmental samples and is a more accessible analytical technique compared with other available methods. This study is the first published investigation of ICP-MS/MS for the direct quantification of sulfur in freshwater DOM. Sulfur (32 S) detection occurs at a mass-to-charge ratio of 48 as 32 S16 O+ after removal of interferences and reaction with oxygen gas. We compare three commonly used DOM preparation methods to assess variability among replicate samples. Preparation of freshwater DOM samples by solid phase extraction followed by evaporation overnight and dissolution in 2% nitric acid results in the most accurate quantification of sulfur. Analysis of sulfur in Suwannee River Fulvic Acid standard serves as method validation, measuring a carbon-normalized sulfur concentration that is ∼20% higher than previously reported methods. We apply the ICP-MS/MS analysis method to determine sulfur concentrations in DOM from nine lakes in the northern Midwest. Carbon-normalized sulfur concentrations in the selected lakes are in general agreement with previously reported percentages of sulfur-containing formulas in DOM found by Fourier transform-ion cyclotron resonance-mass spectroscopy.

Synthesis of Enantioenriched 3,4-Disubstituted Chromans through Lewis Base Catalyzed Carbosulfenylation.

A method for the catalytic, enantioselective, carbosulfenylation of alkenes to construct 3,4-disubstituted chromans is described. Alkene activation proceeds through the intermediacy of enantioenriched, configurationally stable thiiranium ions generated from catalytic, Lewis base activation of an electrophilic sulfenylating agent. The transformation affords difficult-to-generate, enantioenriched, 3,4-disubstituted chromans in moderate to high yields and excellent enantioselectivities. A variety of substituents are compatible including electronically diverse functional groups as well as several functional handles such as aryl halides, esters, anilines, and phenols. The resulting thioether moiety is amenable to a number of functional group manipulations and transformations. Notably, the pendant sulfide was successfully cleaved to furnish a free thiol which readily provides access to most sulfur-containing functional groups which are present in natural products and pharmaceuticals.

Study on the performance of petroleum coke after electrolytic desulfurization in NaBr-CH3COOH system

ABSTRACT In this paper, CH3COOH is used to adjust the electrolyte, control different acid concentrations, and use the ·OOH, HBrO, BrO3 − produced by the electrolyte on the anode to oxidatively desulfurize the petroleum coke particles suspended in the electrolyte. The desulfurized petroleum coke was analyzed by NB/SH/T 0527–2019 indicators and SEM, TGA, XRD, FTIR, and XPS to explore the degree and regularity of desulfurization conditions on the quality of petroleum coke, and explore the mechanism of the desulfurization process. The experimental results show that the NaBr-CH3COOH system has different desulfurization effects under different acid concentration conditions of pH = 2 ~ 6, and the impact on the quality of petroleum coke is also significantly different. A large acid concentration has a high desulfurization yield of petroleum coke. The desulfurization effect is best at pH = 2, and the desulfurization yield can reach 88.92%, but it has a certain impact on the quality indicators of the petroleum coke industry. The heating value of petroleum coke is slightly reduced, and the volatile content the ash yield content has increased compared with the original coke. The change is mainly due to the scission of the branch, the reduction of carbon atoms due to the oxidation reaction, and other side reactions that occur during the electrolytic oxidation reaction, which makes the oxygen content increase and the combustion performance becomes better. XPS analysis results show that the macromolecular structure of petroleum coke is hardly destroyed. According to the changes of oxygen-containing functional groups and sulfur-containing functional groups on the surface of petroleum coke, the mechanism of petroleum coke desulfurization was preliminarily explored.

The chemical structure and thermal evolution of oil Sands bitumen: Experimental and molecular simulation study

In this study, the chemical structural units of two Indonesian oil sands bitumen (OSB) samples were experimentally characterized by advanced techniques. The results show that the chemical structure of OSB samples was dominated by aliphatic structures, with aliphatic carbon ratios of 0.54 and 0.58, respectively. The aromatic carbon structure exhibits a high degree of condensation, but a small number of rings. The structures with the most oxygen-containing functional groups consist of hydroxyl and aliphatic ethers. The sulfur-containing functional groups mainly consist of aliphatic sulfur, followed by aromatic sulfur. By studying the thermal evolution pattern of OSB functional groups at different temperatures, it was found that aliphatic structures form a large number of olefins and alkanes during pyrolysis. In contrast, aromatic structures undergo condensation reactions to form highly polymeric structures that are more difficult to decompose. Moreover, aliphatic sulfur is the main sulfur-containing functional group. It exhibits poor thermal stability and gets easily reduced during pyrolysis, which is more significant than aromatic sulfur. At the same time, only hydroxyl and aromatic ethers in the structure of oxygen-containing functional groups exhibit better thermal stability, even in OSB, at a final temperature of 500 °C. Based on the experimental research, the alicyclic structure was used as a “bridge” and the “archipelago” type molecular structure model of OSB was constructed. After energy optimization, the total energies of DBI and EBI were 6410.08 and 6028.55 kJ mol−1, respectively. The model was compact and stable, showing a more obvious formation of sheet type structure.

Co-pyrolysis of rice straw with industrial wastes: Waste disposal and environmental remediation.

To reduce waste volumes and recover valuable products, char was synthesized via co-pyrolysis of rice straw (RS) with spent tires, sulfur wastes, and CO2. The inclusion of wastes and CO2 in pyrolysis of RS was hypothesized to enhance the sorption ability of char for various contaminants, including 2,4-dinitrotoluene (DNT), 2,4-dichlorophenol (DCP), lead, barium, chromate (CrO42-), and selenate (SeO42-). Using a lab-scale electrical furnace, the co-pyrolysis was conducted, and the soprtion capacity of char was evaluated via a series of batch sorption experiments. The maximum sorption capacity of spent tire-RS char for DNT was 16.8 ± 0.2 mg g-1, much higher than that of RS biochar (10.1 ± 0.3 mg g-1) due to increasing carbon content from the spent tires. The sorption of DCP to the spent tire-RS char was also enhanced via hydrophobic sorption to carbon residues, although not to the same degree of DNT due to deprotonation of the DCP. Compared with RS biochar, co-pyrolysis with raw sulfur wastes and CO2 enhanced sorption of lead, barium, and chromate, which can be attributed to increased cation and anion exchange capacities resulting from developments of oxygen or sulfur-containing functional groups. Sorption of selenate was strongly affected by pH. The results suggest that co-pyrolysis of agricultural and industrial wastes and CO2 is a promising option for the final waste disposal and the production of valuable char, which can be selectively customized for various types of contaminants as sorbents.

Unveiling Complete Ethanol Oxidation through a Hybrid Enzymatic and Organic Catalyst Cascade in an Electrochemical Micro-Reactor Device

Biological fuel cells have been extensively reported as a efficient and sustainable device to convert chemical energy to electrical energy [1]. Biofuel cells (BFCs) are alternative energy sources which use enzymes (enzymatic biofuel cell) or microorganisms (microbial fuel cell) as the electrocatalysts instead of the traditional noble metal catalysts. Ethanol is a fuel that can be used in combined enzymatic fuel cell due to its high energy density (8.03 kW h kg -1), low emission, and storage security [2]. The advantage of enzymes is that they exhibit high specificity and turnover rate, however, mimicking the natural metabolism from ethanol through electrometabolic pathways is enormously difficult. To overcome the limitations of using multiple enzymes to achieve the complete ethanol oxidation, a small molecule organic catalyst can be employed. TEMPO (2,2,6,6-tetramethylpiperidin-1-yl) oxyl) is a small organic catalyst that does not present limited substrate specificity such as enzymes face, due to its ability to oxidize oxygen, nitrogen and sulfur-containing functional groups. Thus, hybrid system enables improvement at the rate of electrocatalytic oxidation of several biofuels [2 - 4]. Herein, we described the development of a hybrid catalytic architecture combining an organic oxidation catalyst, 4-amino-TEMPO (TEMPO-NH2), and a recombinant enzyme, oxalate decarboxylase (OxDc) to catalyze complete ethanol electrooxidation. The catalyst system was coupled with a novel small scale electrolysis cell utilizing polycaprolactone (PCL) and carbon composite electrodes for bulk electrolysis. Electrochemical meansurements and product detection by nuclear magnetic resonance (NMR) after 12 hours of electrolysis have shown for the first time that an organic catalyst and decarboxylase enzyme enhances the overall steps in the cascade operating at acidic pH enabling enhanced electrochemical oxidation of ethanol to CO2. To validate the reaction sequence, a novel micro-reactor device enabled low-cost product analysis and allows for high analyte sensitivity. Overall, this work demonstrated that bi-cascade of TEMPO-NH2 and OxDc can be combined in an electrochemical cell to synergistically catalyze the oxidation of substrates that make up the steps of the ethanol oxidation cascade and is promising for a wide array of applications, including biosensors, environmental monitoring, and biofuel cells.

Dehydration of isopropyl alcohol with activated carbon functionalized with Br- and S-containing reagents

Bromination of activated carbon GSGD was performed and active bromine-containing precursors were obtained, in which bromine is capable of being replaced by sulfur-containing functional groups. Bromination with liquid bromine and a solution of bromine in potassium bromide at room temperature leads to the introduction of 0.44–0.45 mmol g–1 of bromine into the surface layer of activated carbon. The treatment of brominated samples with sulfur-containing reagents with subsequent oxidation allows obtaining carbon samples that are catalytically active in the dehydration reaction of isopropyl alcohol in a gas phase. The temperature of complete conversion of isopropyl alcohol to propylene is a measure of catalytic activity. The concentration of sulfogroups in the prepared samples is up to 0.3 mol g–1. Thermogravimetry and thermoprogrammed desorption with mass spectrometric registration of products were used to study the thermal stability of modified activated carbon samples. The influence of the nature of brominating reagents, hydrolysis conditions and oxidation conditions on the structure, surface concentration of grafted S-containing groups and catalytic properties of the obtained materials was studied. Pre-bromination leads to an increase in the catalytic activity of activated carbon modified with sulfur-containing groups and the temperature of complete conversion of isopropyl alcohol to propylene decreases up to 400C depending on the concentration of sulfogroups.