Protonic Acid Research Articles

Enhanced enzyme-based CO2 capture in countercurrent packed-bed column reactors

An enhanced CO2 hydration process with human carbonic anhydrase II (hCA II) enzyme immobilized on packing surface and micro-particles dispersed in the liquid phase was proposed. This innovative hybrid enzymatic process was simulated in a countercurrent packed-bed column reactor via an unsteady-state, isothermal, 3-D model including continuity, momentum and species (including the biocatalytic micro-particles) balance equations in the liquid and gas phases, filtration equation describing the accumulation of biocatalytic micro-particles in packed bed, chemical reaction and diffusion in hCA II enzyme washcoat and liquid film. In the hybrid enhanced immobilized enzyme CO2 capture system, hCA II enzyme supported on the surface of micro-particles works as a free solution-phase enzyme, which instantaneously catalyzes CO2 hydration reaction and upgrades significantly CO2 conversion, particularly in the region where the enzymatic process with immobilized hCA II enzyme on the packing surface is strongly limited by the diffusion. The impact of hCA II enzyme immobilized on the micro-particles surface is more important when the foremost amount of hCA II enzyme is immobilized on the packing via larger washcoat layers with enhanced mass transfer resistance, at larger feed buffer concentration and lower thermodynamic dissociation constant of the protonated acid form of buffer. Enhanced CO2 hydration process provide a reasonable CO2 conversion at a much lower liquid velocity and permits to significantly downgrade the height of the packed bed. These immobilized enzyme CO2 capture systems intend to maximize the mass transfer in packed-bed column reactors to expand the degree of utilization of the large hydration turnover of hCA II enzyme.

FLUORESCENCE AND RED SHIFT OF THE PHOTOPHYSICAL PROPERTIES FROM PROTONATED SMALL MOLECULE

In this work, the fluorescence (FL) and bathochromic of the photophysical properties from protonated small molecule in cast film state have been investigated. To realize these purposes, the material of 4’,4’’’’-(1,4-phenylene bis (2,2’:6’,2”-terpyridine) (Phtpy) as a small molecule and camphorsulfonic acid (CSA) as an acid for protonation was selected. For Phtpy, its maxima absorption is 300 nm and no FL color emission. After CSA solution was added in chlorofom solution of Phtpy, the absorption spectrum of protonated Phtpy is broaden to longer wavelength with two new peaks appear at around 350 and 370 nm. Upon direct excitation at wavelength of 300 nm, the range of FL spectrum of original and protonated Phtpy is from 320 to 580 nm and from 370 to 580 with their maxima FL intensities at 360 and 460 nm. Interestingly, protonated Phtpy emits blue FL color emission. In addition, energy gap of protonated Phtpy is smaller than that of pristine Phtpy. Finally, the FL and remarkable red shift of absorption and FL spectra of protonated Phtpy will pave the way to develop sensor and other photonic devices with high performances in the ultaviolet region.

Free-standing, thin-film, symmetric membranes: Next-generation membranes for engineered osmosis

The support layer of an asymmetric thin-film composite membrane results in structural resistance (internal concentration polarization) that significantly undermines engineered osmosis. Increasing the porosity and reducing the thickness and tortuosity of the membrane support layer reduces structural resistance; however, internal concentration polarization still impacts membrane performance. A novel, ultrathin, free-standing and symmetric membrane has been synthesized using sulfonated polyether ketone and tested for forward osmosis applications. This membrane is composed of a protonic acid group containing an aromatic polyether resin with sulfonated structural units. Polyether ketone provides high mechanical strength essential for ultrathin free-standing membranes, while sulfonation enhances the membrane hydrophilicity. These sulfonated polyether ketone membranes show promising water flux performances with impressive mechanical strength under the hydraulic operating conditions used for a FO process.

Core–Shell Structured Magnetic γ-Fe2O3@PANI Nanocomposites for Enhanced As(V) Adsorption

Core–shell structured magnetic γ-Fe2O3 coated with proton acid doping polyaniline nanocomposites (γ-Fe2O3@PANI) were synthesized and used to adsorb arsenic(V) in aqueous solutions. Results indicate...

Novel recyclable deep eutectic solvent boost biomass pretreatment for enzymatic hydrolysis

Deep eutectic solvent (DES) with protonic acid shows the great potential for biomass valorization. However, the acid corrosion and recycling are still severe challenges in biorefinery. Herein, a novel DES by coordinating FeCl3 in choline chloride/glycerol DES was designed for effective and recyclable pretreatment. As compared to DESs with FeCl2, ZnCl2, AlCl3 and CuCl2, DES with FeCl3 approvingly retained most of cellulose in pretreated Hybrid Pennisetum (95.2%). Meanwhile, the cellulose saccharification significantly increased to 99.5%, which was six-fold higher than that of raw biomass. The excellent pretreatment performance was mainly attributed to the high removal of lignin (78.88 wt%) and hemicelluloses (93.63 wt%) under the synergistic effect of Lewis acid and proper hydrogen-bond interaction of DES with FeCl3. Furthermore, almost all cellulose still can be converted into glucose after five recycling process. Overall, the process demonstrated designed pretreatment was great potential for the low-cost biorefinery and boost the biofuel development.

Chemiluminescence Induced Cationic Photopolymerization Using Sulfonium Salt.

A visible light cationic photoinitiating system under chemiluminescence irradiation using sulfonium salt is reported. The visible light emitted from the chemiluminescence reactions, absorbed by the sulfonium salt, essentially leads to the formation of protonic acids capable of initiating cationic polymerization of oxirane and vinyl monomers. The process is suitable for the formation of linear polymer chains as well as cross-linked functional networks with aggregation-induced emission property. Notably, high "post polymerization" efficiency in dark (∼20%) was observed, which can compensate the limited chemiluminescence fluorescence efficiency and favors to increase the conversion.

Extraction and characterization of phycocyanin from Spirulina platensis and evaluation of its anticancer, antidiabetic and antiinflammatory effect

The phycocyanin was purified by Sephadex- G-100 and RP-HPLC and protein content was found to be 52.82% and the high purity fraction was collected and RP-HPLC analysis of fractionated phycocyanin, the α-subunit and β-subunit were detected in 4.9 and 11.1(mAU). The frequency of peak 1456.26 cm−1 has showed the CH2 bending vibration and the protein amide II band was detected at 1539.20 cm−1 (CO stretching) and 2358.94 cm−1. In 1H NMR analysis, 14 chemical shifts (δ) were observed and signals confirmed namely alkyl halide, alkene, aldehyde proton and carboxylic acid. The in vivo anticancer effect was assessed by MTT assay against HepG-2 cell lines and in vivo antidiabetic effect was carried out through α-amylase and β-glucosidase enzyme inhibition methods. The promising anticancer effect 68% was noticed at the concentration of 500 μg/ml and lower anticancer effect was noticed at the concentration of 100 μg/ml against Hep-G2 cell lines. The α-amylase and β-glucosidase enzyme inhibition of phycocyanin showed dose dependent and maximum inhibition effect at 250 μg/ml. Phycocyanin anti-inflammatory effect such as inhibition of albumin denaturation, antiproteinase, hypotonicity-induced haemolysis and anti-lipoxygenase activities have been recorded maximum level at 500 μg/ml. Phycocyanin have complex structure and high molecular weight with more biomedical applications for drug development.

Hydroconversion of n-hexane over Pt-supported on fibrous silica mordenite catalysts: effect of transition metals on acidity and activity

The effect of incorporation of either Zr, Co, Mo or Zn on Pt/HFSM was investigated for the hydroconversion of n-hexane in a pulsed micro-reactor at a temperature range 423-623 K. The acidity of all the studied catalysts were investigated using pyridine adsorption and Fourier Transform Infrared Spectroscopy. The FTIR-pyridine study showed that the catalysts possessed different concentration and strength of both Lewis and Brønsted acid sites. It was revealed that the moderate acid sites distribution on PtZr/HFSM and PtZn/HFSM facilitated the isomerization of the intermediate hexene while the strong acid sites were selective towards cracking reaction. The trend for the bimetallic catalysts studied in n-hexane hydroisomerization is in the order: PtZr/HFSM>PtZn/HFSM>PtMo/HFSM>PtCo/HFSM. The highest activity for hydrocracking and hydrogenolysis were exhibited by PtMo/HFSM and PtCo/HFSM respectively. The PtZr/HFSM exhibited the highest hydroisomerization activity due to the moderate acidity and abundant Lewis acid sites capable of generating protonic acid sites by the hydrogen-spill over phenomena.

Functionalized polyaniline based on protonic acid doping as a direct electron mediator to amplify sensor signals

A “label-free” electrochemical immunosensor was developed to detect α-fetoprotein (AFP) sensitively. HCS@PANI (High carbonized nanospheres@Polyaniline) is used as an electrochemical sensing platform to improve conductivity and enhanche the amount of AFP antibody (anti-AFP) immobilized on the electrode surface. PANI, which is involved by protonic acid, exhibits excellent electrochemical activity and can be used as a direct electron mediator to further amplify electrochemical signals. Under optimal conditions, the electrochemical immunosensor has a linear range of 0.001–80 ng/mL and a minimum detection limit of 0.33 pg/mL. The immunosensor is expected to be used in clinical laboratories to detect AFP and other tumor markers in human plasma for precancerous screening or cancer surveillance.

Unexpected NADPH Hydratase Activity in the Nitrile Reductase QueF from Escherichia coli.

The nitrile reductase QueF catalyzes NADPH‐dependent reduction of the nitrile group of preQ0 (7‐cyano‐7‐deazaguanine) into the primary amine of preQ1 (7‐aminomethyl‐7‐deazaguanine), a biologically unique reaction important in bacterial nucleoside biosynthesis. Here we have discovered that the QueF from Escherichia coli—its D197A and E89L variants in particular (apparent k cat≈10−2 min−1)—also catalyze the slow hydration of the C5=C6 double bond of the dihydronicotinamide moiety of NADPH. The enzymatically C6‐hydrated NADPH is a 3.5:1 mixture of R and S forms and rearranges spontaneously through anomeric epimerization (β→α) and cyclization at the tetrahydronicotinamide C6 and the ribosyl O2. NADH and 1‐methyl‐ or 1‐benzyl‐1,4‐dihydronicotinamide are not substrates of the enzymatic hydration. Mutagenesis results support a QueF hydratase mechanism, in which Cys190—the essential catalytic nucleophile for nitrile reduction—acts as the general acid for protonation at the dihydronicotinamide C5 of NADPH. Thus, the NADPH hydration in the presence of QueF bears mechanistic resemblance to the C=C double bond hydration in natural hydratases.

Enhancement of electrochemical performance of cobalt (II) coordinated polyaniline: A combined experimental and theoretical study

The cobalt (II) coordinated PANI (PANI-Co) was synthesized via a facile electropolymerization and hydrothermal process and applied for energy storage electrode material. The coordination bonding is formed between Co (II) ion and nitrogen of quinonediimine of PANI. PANI-Co achieves higher capacitance of 653 F g−1 at 1 A g−1 than PANI of 459 F g−1, and maintains high capacitance retention of 85.60% when the current density increases from 1 to 10 A g−1. The first-principles calculations result shows the protonated PANI-Co (H-PANI-Co) has much larger Fermi energy (N(E)) than the protonated PANI (H-PANI) and bare PANI, indicating its improved conductivity. The electrostatic potential of H-PANI-Co reveals the enhanced carrier transport behavior. The HOMO−LUMO energy gap decreases from 0.901 eV of PANI to 0.265 eV of H-PANI-Co. Moreover, H-PANI-Co shows less than half deprotonation energy of H-PANI, indicating more feasible protonic acid doping/dedoping process. All-solid-state supercapacitor constructed with PANI-Co electrode and gel electrolyte achieves energy density of 60.1 W h kg−1 at high power density of 900 W kg−1 and exhibits long cycle life with high capacitance retention of 83.8% after 1000 cycles. So, PANI-Co could act as an appropriate energy-storage electrode material. The first-principles calculations provide an alternative theoretical strategy to study the electrical properties of conducting polymer.

Site-Selective N-Methylation of 5,15-Diazaporphyrins: Reactive Cationic Porphyrinoids that Provide Isoporphyrin Analogues.

N-Alkylation significantly changes the electronic and optical properties, as well as the reactivity of nitrogen-containing π-conjugated molecules. In this study, it is found that treating 5,15-diazaporphyrins with methyl triflate selectively affords the corresponding N-methyl-5,15-diazaporphyrinium cations in good yield. N-Methylation substantially alters the electronic properties and reactivity of diazaporphyrins. The electron-accepting properties of the N-methyl-5,15-diazaporphyrinium cations are enhanced due to their lowered LUMO level. Stabilization of the LUMO energy enables regio- and stereoselective Diels-Alder reactions of the cationic diazaporphyrin with cyclopentadiene. N-Methylation also enhances the acidity of the inner NH protons, and thus, allows facile deprotonation to provide nitrogen-substituted isoporphyrin analogues with only one NH group in the central cavity.

Influence of Nitrate and Phosphate on Silica Fibrous Beta Zeolite Framework for Enhanced Cyclic and Noncyclic Alkane Isomerization.

Phosphate and nitrate were loaded on silica BEA (P/HSi@BEA and N/HSi@BEA), which is fibrously protonated by the impregnation method for n-hexane and cyclohexane isomerization. The characterization analysis specified the removal of tetrahedral aluminum atoms in the framework, which was triggered by the existence of phosphate and nitrate groups in the catalyst. The exchanged role of Si(OH)Al to P-OH as active acidic sites in the P/HSi@BEA catalyst reduced its acidic strength, which was confirmed by the FTIR results. Lewis acidic sites of P/HSi@BEA performance are a significant part in the generation of high protonic acid sites, as proven by the in situ ESR study. However, FTIR evacuation and 27Al NMR revealed that the reduction in the amount of extraframework Al (EFAl) is due to its interaction with the nitrate group on the outside of the catalyst surface. The N/HSi@BEA catalyst exhibited high acidic strength because of the existence of more Si(OH)Al, which was initiated during the nitrate-incorporation process. Of significance is that the catalytic performance of n-hexane isomerization in the presence of hydrogen reached 50.3% product isomer yield at 250 °C, which might be ascribed to the presence of P-OH active sites that are responsible for accepting electrons, forming active protonic acid sites. NO3-EFAl interaction induced the formation of Brønsted acid sites, and higher mesopore volume favors the production of cyclohexane isomers up to 48.4% at 250 °C. This fundamental study exhibits that significant interactions given by such phosphate and nitrate groups with the unique silica fibrous BEA support could enhance isomerization, which contributes to the high quality of fuel.

Sourcing nitrogen from nitromethane

Organic Chemistry Nitromethane is produced in bulk quantities for use as a solvent. Its applications as a reagent have focused mainly on the acidity of the methyl protons en route to modifying the carbon center. Liu et al. now report an alternative protocol that activates the nitrogen center to produce an aminating agent. An in situ reductive reaction with triflic anhydride, formic acid, and acetic acid yields an acetylated hydroxylamine, characterized by mass spectrometry. This nitrogen donor conveniently transforms a variety of ketones and aldehydes into amides. Science , this issue p. [281][1] [1]: /lookup/doi/10.1126/science.aay9501

Esterification Between Citric Acid and <i>Callistemon citrinus</i>, Rice-Husk, <i>Garcinia dulcis</i> Catalysed by Citric Acid’s-H<sup>+</sup>- Monomers and Polymers Formation Mechanism

Esterification between citric acid molecules and molecules of <i>Callistemon citrinus</i>, rice husk and <i>Garcinia dulcis</i> (pulp-peel and pips) were carried out such as the citric acid molecules quantities (moles) were negligible against to these raw materials’ reactive molecules quantities (moles). Results showed generally an important initial, total conversions (after 60 minutes) of citric acids molecules which confirmed the essential role of raw materials’ aromatics molecules characterized by their alkene organic-function titrated with HF-0.00261N (Hydrofluoric acid) as support of citric acid’s protonic acid H⁺ catalyst (a portion of the carboxylic acids’ citric acid molecules used), support of non-ionic citric acid’s carboxylic acid (a portion of the carboxylic acids’ citric acid molecules used) and support of raw materials molecules reagents. So, the citric acid partial order of esterification of these used raw materials (<i>Callistemon citrinus</i>, rice husk and <i>Garcinia dulcis</i> (pulp-peel and pips)) with citric acid molecules were determined. Also, the brown citric acid equivalent monomers formed during esterification were calculated and their evolution were followed for all raw materials and results allowed to determine the citric acid’s protonic acid activities. In the same time, relationship between raw materials’ external specific surfaces, estimated by calculated and measured densities, and conversion or brown citric acid equivalent formed were established to conduct finally at the catalyst turnover. The variation of alkene organic-function concentration and/or quantities not only in solution but also in all by-products allowed to an ionic mechanism of these esterification with citric acid catalyzed by citric acid’s protonic acid H⁺ (a portion of the carboxylic acids’ citric acid molecules used) supported on all raw materials’ aromatics molecules and fiber structures in glass-flask where not only carbonic acids molecules but also hydrogens molecules gas were emitted. Finally, seeing that a non-negligible alkene organic-function quantities were titrated on all by-products, their valorization as catalytic support of citric acid molecules polymerization were carried out and a procedure constituted principally with estimation of dichloromethane and hexane insoluble/soluble products, titration with HF-0.00261N of the unsaturated organic-function in hexane soluble products and titration with NaOH-0.05N of the black citric acid equivalent quantities evolutions were established and the results confirmed the ionic mechanism of esterification with citric acid molecules during which not only carbonic gas and hydrogen gas were emitted but also new monomers and each equivalent saturated products (characterized by their globally white color and unsaturated organic-function titrated with HF-0.00261N), new polymers and poly-polymers (characterized by their globally black color and titrated with NaOH-0.05N) different to that obtained with radical mechanism catalyzed by Lewis acid sites were formed.

Polyaniline Doped with Protonic Acids: Optical and Morphological Studies

Polyaniline Doped with Protonic Acids: Optical and Morphological Studies

Synthesis of polyaniline by chemical oxidative polymerization and characteristic of conductivity and reflection for various strong acid dopants

Herein, polyaniline (PANI) is synthesized via chemical oxidative polymerization of aniline monomer with ammonium persulfate as initiator by maintaining the flow rate and stirring for 8 h at room temperature. Particle sizes up to 54.716 μm are obtained, with a viscosity reaching 1.87 mPa-s at 270 min. The highest temperature during polymerization was 32 °C at 210 min. Thus, the polymer molecules undergo propagating process to form polymer chains. Fourier transform infrared spectroscopy confirms the presence of the PANI molecule, which reveals a complete reaction when the double-bond peak at 3442 cm−1 disappears from the spectrum and new peaks appear corresponding to benzoic and quinoid molecules at 1300-1600 cm−1. This ensures that all aniline molecules are converted to PANI with no residual. We conclude that PANI is synthesized via oxidative polymerization. The electrical conductivity of PANI is driven by protonic acids. The conductivity increases upon adding protonic acids as a strong acid-doping agent. Thus, PANI-HClO4 exhibits best conductivity. The best material candidate for a microwave-absorbing material is thus PANI-EB because it has the highest reflection loss at -29.69 dB at 11.812 GHz, whereas PANI-HClO4 has only -2.74 dB reflection loss at 12.400 GHz.

Protonic acid doping of low band-gap conjugated polyions

Conjugated polyions (CPIs) offer synthetic tunability and selective processing into insulating, semiconducting and metallic states simply by controlling acidity.

Nitromethane as a nitrogen donor in Schmidt-type formation of amides and nitriles.

The Schmidt reaction has been an efficient and widely used synthetic approach to amides and nitriles since its discovery in 1923. However, its application often entails the use of volatile, potentially explosive, and highly toxic azide reagents. Here, we report a sequence whereby triflic anhydride and formic and acetic acids activate the bulk chemical nitromethane to serve as a nitrogen donor in place of azides in Schmidt-like reactions. This protocol further expands the substrate scope to alkynes and simple alkyl benzenes for the preparation of amides and nitriles.

Proton-Coupled Electron Transfer Kinetics for the Photoinduced Generation of a Cobalt(III)-Hydride Complex.

Studying the formation of transition metal hydride complexes via proton-coupled electron transfer is important for developing next-generation molecular catalysts for hydrogen evolution. We report herein the study of stepwise photoinduced reduction and protonation of [CoIICp(dppe)]+ (Cp = cyclopentadienyl, dppe = 1,2-bis(diphenylphosphino)ethane) to form the corresponding hydride complex [HCoIIICp(dppe)]+. Reaction intermediates were optically tracked using transient absorption spectroscopy, and a combination of experimental fitting and kinetic simulations was used to determine apparent rate constants for electron transfer and proton transfer with a range of acid sources. A linear free energy relationship is observed between measured apparent proton transfer rate constants and acid strength, but marked differences from previously electrochemically determined protonation rate constants are found. These deviations, which stem from ground-state reactivity present in photochemical experiments, highlight the challenges in comparing mechanistic studies using different techniques.