Aqueous Triethanolamine Research Articles

Enhanced Photocatalytic Activity of Surface‐Modified TiO2 with Bimetallic AuPd Nanoalloys for Hydrogen Generation

Herein, commercial titania (TiO2‐P25) is modified with mono‐ and bi‐metallic (Au, Pd, and AuPd) nanoparticles synthesized by chemical reduction method using NaBH4 as a strong reducing agent at room temperature. Bimetallic AuPd nanoalloys homogeneous in size and well dispersed on the TiO2 surface are obtained. The charge‐carrier dynamics, which is a key factor in photocatalysis, is studied by time‐resolved microwave conductivity. The results reveal that surface modification plays a crucial role in charge‐carrier separation, increasing the activity under UV–vis light irradiation. The bimetallic AuPd nanoalloys formation is confirmed by high‐angle annular dark field scanning transmission electron microscopy and corroborated by semiempirical molecular dynamics simulations (Gupta‐LAMMPS). The surface‐modified TiO2 with bimetallic AuPd nanoalloys exhibits higher photocatalytic activity compared to TiO2 modified with their monometallic counterparts. The experimental results are also supported by density functional theory and density functional tight binding calculations, which show that alloying AuPd with low Pd content presents significant synergetic effects for hydrogen generation under UV–vis light from aqueous triethanolamine solutions. Additionally, the AuPd/TiO2 photocatalysts are stable with cycling.

Enzymatic Carboxylation of Resorcinol in Aqueous Triethanolamine at Elevated CO2 Pressure.

The fixation of CO2 by enzymatic carboxylation for production of valuable carboxylic acids is one way to recycle carbon. Unfortunately, this type of reaction is limited by an unfavourable thermodynamic equilibrium. An excess of the C1 substrate is required to increase conversions. Solvents with a high CO2 solubility, such as amines, can provide the C1 substrate in excess. Here, we report on the effect of CO2 pressures up to 1100 kPa on the enzymatic carboxylation of resorcinol in aqueous triethanolamine. Equilibrium yields correlate to the bicarbonate concentration. However, inhibition is observed at elevated pressure, severely reducing the enzyme activity. The reaction yields were reduced at higher pressures, whereas at ambient pressure, higher yields were achieved. Overall, CO2 pressures above 100 kPa have been demonstrated to be counterproductive for improving the biotransformation, as productivity decreases rapidly for only a modest improvement in conversion. It is expected that CO2 carbamylation intensifies at elevated CO2 pressures, causing the inhibition of the enzyme. To further increase the reaction yield, the in situ product precipitation is tested by the addition of the quaternary ammonium salt tetrabutylammonium bromide.

Synthesis of 2,6-Dihydroxybenzoic Acid by Decarboxylase-Catalyzed Carboxylation Using CO2 and In Situ Product Removal

For the enzymatic carboxylation of resorcinol to 2,6-dihydroxybenzoic acid (2,6-DHBA) using gaseous CO2 in an aqueous triethanolamine phase, an adsorption-based in situ product removal was demonstrated. The aim is to improve the reaction yield, which is limited by an unfavourable thermodynamic equilibrium. First, a screening for a high-affinity adsorber was carried out. Then, the application of a suitable adsorber was successfully demonstrated. This enabled achieving reaction yields above 80% using the adsorber for in situ product removal. The applied biotransformation was scaled up to 1.5 L at lab-scale. Furthermore, a downstream process based on the elution and purification of the product bound to the adsorber was developed to obtain 2,6-DHBA in high purity. Recycling is one of the key factors in this system, making it possible to recycle the reaction medium, the adsorber and the solvents in additional batches.

Carbon dioxide absorption by Ammonia-promoted aqueous triethanolamine solution in a packed bed

Carbon dioxide absorption by Ammonia-promoted aqueous triethanolamine solution in a packed bed

Effect of Ethane on the Solubility of CO2 in Aqueous Triethanolamine Solutions

Effect of Ethane on the Solubility of CO2 in Aqueous Triethanolamine Solutions

Solar thermal-activated photocatalysis for hydrogen production and aqueous triethanolamine polymerization

Solar thermal-activated photocatalysis (STAP) has been developed as an efficient sustainable technology for hydrogen generation and aqueous triethanolamine polymerization initiated by heterogeneous photocatalysts under solar light irradiation.

Carbon Dioxide Absorption by Ammonia Promoted Aqueous Triethanolamine Solution in a Packed Bed

Carbon Dioxide Absorption by Ammonia Promoted Aqueous Triethanolamine Solution in a Packed Bed

One-step preparation of cobalt phosphate at room temperature for effective photocatalytic H2 evolution

Cobalt phosphate materials were prepared in the present work in one step at room temperature using different raw materials and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and N2 gas adsorption. Cobalt phosphates exhibit 3D flower-like structures, and the assembly of nanosheets (petals of the "flowers") of cobalt phosphate prepared with sodium phosphate and cobalt acetate as raw materials (denoted as Co-P(A)) is more incompact than that of cobalt phosphate prepared with diammonium hydrogen phosphate and cobalt nitrate as raw materials (denoted as Co-P(B)) due to the former's mildly basic environment. The cobalt phosphates show relatively high photocatalytic activity for H2 evolution reaction (HER) in the presence of Eosin Y as a sensitizer in an aqueous triethanolamine solution. The activity of Co-P(A) (0.40 mmol h-1 g-1) exceeds that of Co-P(B) (0.19 mmol h-1 g-1), which can be attributed to a more dispersive nanosheet and larger BET-specific surface area of Co-P(A). The mechanisms of photocatalytic HER and the formation of flower-like Co3(PO4)2 were discussed. The present system comprising of only abundant elements contributes toward the development of cost-efficient solar HER to achieve sustainable development.

Two Tungstates Containing Platinum Nanoparticles Prepared by Air-Calcining Keggin-Type Polyoxotungstate-Coordinated Diplatinum(II) Complexes: Effect on Sintering-Resistance and Photocatalysis

Two tungstates containing platinum nanoparticles (Pt Npts) were obtained by air-calcining α-Keggin-type diplatinum(II)-coordinated polyoxotungstates, Cs3[α-PW11O39{cis-Pt(NH3)2}2]⋅8H2O (Cs-P-Pt) and Cs4[α-SiW11O39{cis-Pt(NH3)2}2]⋅11H2O (Cs-Si-Pt), at 700–900 °C for 5 h. The polyoxotungstate Cs-P-Pt was transformed to a mixture of Pt Npts and Cs3PW12O40 upon calcination, while the Cs-Si-Pt structures were transformed to Pt Npts and Cs4W11O35. The Pt Npts generated by air-calcining Cs-P-Pt at 700 °C for 5 h were uniform with an average particle size of 3.6 ± 1.1 nm, which was much smaller than that of the Pt Npts obtained by calcining Cs-Si-Pt (19.9 ± 9.9 nm) under identical conditions. This demonstrated the significant inhibitory effect of Cs-P-Pt on aggregation during high-temperature air-calcination at a high platinum content (10.6 wt.%) and in the absence of a support. During calcination at 700–900 °C, Cs-P-Pt exhibited higher activities than Cs-Si-Pt with respect to hydrogen evolution from aqueous triethanolamine solutions under visible light irradiation in the presence of Eosin Y, α-Keggin-type mono-aluminum-substituted polyoxotungstate, and titanium dioxide. When Cs-P-Pt was calcined at 800 °C for 100 h, no decrease in activity was observed in comparison with that upon calcination for 5 h.Graphical

A Novel Donor-π-Acceptor Type Sensitizer for Dye Sensitized Photochemical Hydrogen Generation

A novel triphenylamine (TPA) based donor-π-acceptor (D-π-A) dye is synthesized and its optical and electrochemical properties are examined by UV-Vis absorption spectroscopy and cyclic voltammetry methods, respectively. The synthesized D-π-A dye plays a role as a visible light sensitizer to wide bandgap TiO2 photocatalyst. Hydrogen evolution reaction (HER) are carried out by using D-π-A dye sensitized TiO2 (Dye/TiO2) under visible light irradiation in the aqueous triethanolamine (TEOA) medium. Photoelectrochemical properties of Dye/TiO2 are investigated by using linear sweep voltammetry (LSV) and chronoamperometry (CA) techniques in the aqueous Na2SO4/TEOA solution and its transient photoelectrochemical response is reached 90 μA cm-2. In addition, phtocatalytic hydrogen evolution rates are found out as 0.52 mmol g-1 h-1 and 1.95 mmol g-1 h-1 by using of Dye/TiO2 and Dye/TiO2/Pt, respectively, which are obtained by in situ photoreduction of H2PtCl6 on the Dye/TiO2 photocatalyst. The mechanism of photochemical HER is explained by electrochemical band levels of the D-π-A dye and TiO2 photocatalyst.

Microbubble enhanced mass transfer efficiency of CO2 capture utilizing aqueous triethanolamine for enzymatic resorcinol carboxylation.

The present study focuses on the aeration of aqueous triethanolamine acting as reaction medium for biocatalytic carboxylations. For enhancing mass transfer in a bubble column reactor, microbubble aeration is applied and compared to conventional macrobubble aeration. Application of a 0.5 μm porous sparger enables microbubble CO2 aeration with bubble size distributions below 150 μm in Sauter mean diameter, correlating with the highest measured mass transfer rates. During CO2 saturation of the aqueous triethanolamine, bubble size distributions changed according to the level of CO2 saturation. For microbubbles, less foaming was observed compared to macrobubble aeration by a 10 μm porous sparger. This microbubble effect is attributed to their accelerated dissolution assisted by the Laplace pressure lowering the amount of bubbles reaching the surface of the liquid. The experiments reveal that the rate of interfacial area generation, which is calculated based on measured bubble size distributions, influences the biocatalyst activity.

Thermal Treatment of a Keggin‐Type Diplatinum(II)‐Coordinated Polyoxotungstate: Formation of Hydrophilic Colloidal Particles and Photocatalytic Hydrogen Production

Hydrophilic platinum‐polyoxotungstate colloidal particles formed by a self‐assembly of Cs4[{Pt(OH)2}2·SiW12O40] were successfully obtained by calcining a cesium salt of α‐Keggin‐type diplatinum(II)‐coordinated silicotungstate, Cs4[α‐SiW11O39{cis‐PtII(NH3)2}2]·11H2O (Cs‐Si‐Pt), in air at 300 °C. During the thermal treatment, the structure of the mono‐lacunary Keggin‐type silicotungstate ligand {SiW11O39} transformed to that of {SiW12O40}, and the diplatinum sites in Cs‐Si‐Pt transformed to the platinum hydroxides with the elimination of the ammonia molecules coordinated to the platinum sites. All four cesium ions in Cs4[{Pt(OH)2}2·SiW12O40] could be ion‐exchanged by four tetramethylammonium ions, and hydrophilic [(CH3)4N]4[{Pt(OH)2}2·SiW12O40] colloidal particles were also formed in aqueous solution. The calcined sample acted as a photocatalyst for hydrogen evolution from aqueous triethanolamine (TEOA) under visible light irradiation (λ = ≥440 nm) in the presence of Eosin Y, K5[α‐SiW11{Al(OH2)}O39]·7H2O, and titanium dioxide. Although relatively rapid deactivation was observed, the turnover frequency was 3588 h–1 after 20 min, and the turnover number exceeded 4600 after 3 h of light irradiation.

Hydrogen production from aqueous triethanolamine solution using Eosin Y-sensitized ZnO photocatalyst doped with platinum

Photocatalytic system for hydrogen production comprising ZnO as a photocatalyst, Eosin Y photo-sensitizer, triethanolamine electron donor and platinum co-catalyst is prepared and systematically tested under visible and simulated solar light irradiation. The results of laboratory experiments show that all studied parameters, such as a solution pH, Pt/ZnO dose, triethanolamine concentration and light intensity, notably influence the rate of photocatalytic hydrogen generation. The maximum hydrogen generation rate of 6.50 μmol min−1 is achieved at pH 7.0 and 2 g L−1 ZnO loaded with 0.75 wt% platinum, and 0.757 M triethanolamine concentration. The rate of hydrogen production as a function of triethanolamine concentration follows Langmuir-Hinshelwood kinetic model with reaction rate constant 4.50 μmol min−1 and adsorption constant 14.84 M−1 in solar light and 5.26 μmol min−1 and 6.67 M−1 in visible light, respectively. The reaction mechanism of hydrogen generation in the tested system is proposed and discussed.

Preparation of platinum nanoparticles using iron(ii) as reductant and photosensitized H2 generation on an iron storage protein scaffold.

The quest for efficient solar-to-fuel conversion has led to the development of numerous homogeneous and heterogeneous systems for photochemical stimulation of 2H+ + 2e− → H2. Many such systems consist of a photosensitizer, an H2-evolving catalyst (HEC), and sacrificial electron donor often with an electron relay between photosensitizer and HEC. Colloidal platinum remains a popular HEC. We report here a novel, simple, and high yield synthesis of Pt nanoparticles (Pt NPs) associated with human heavy chain ferritin (Hfn). The formation of the Pt NPs capitalizes on Hfn's native catalysis of autoxidation of Fe(ii)(aq) (ferroxidase activity). Fe(ii) reduces Pt(ii) to Pt(0) and the rapid ferroxidase reaction produces FeO(OH), which associates with and stabilizes the incipient Pt NPs. This Pt/Fe-Hfn efficiently catalyzes photosensitized H2 production when combined with Eosin Y (EY) as photosensitizer and triethanolamine (TEOA) as sacrificial electron donor. With white light irradiation turnover numbers of 300H2 per Pt, 250H2 per EY were achieved. A quantum yield of 18% for H2 production was obtained with 550 nm irradiation. The fluorescence emission of EY is quenched by TEOA but not by Pt/Fe-Hfn. We propose that the photosensitized H2 production from aqueous TEOA, EY, Pt/Fe-Hfn solution occurs via a reductive quenching pathway in which both the singlet and triplet excited states of EY are reduced by TEOA to the anion radical, EY−˙, which in turn transfers electrons to the Pt/Fe-Hfn HEC. Hfn is known to be a remarkably versatile scaffold for incorporation and stabilization of noble metal and semiconductor nanoparticles. Since both EY and Hfn are amenable to scale-up, we envision further refinements to and applications of this photosensitized H2-generating system.

Room-Temperature Synthesis of ZnS Nanoparticles Using Zinc Xanthates as Molecular Precursors.

Molecular precursors are suitable starting compounds for preparation of semiconductor nanoparticles (NPs), which allow for control of atomic ratio, composition, monodispersity, and particle size of nanoscaled metal sulfides/oxides. In the present study, we carried out a one-pot synthesis of ZnS NPs in aqueous triethanolamine medium at room temperature, from molecular precursor zinc xanthate as a source of both Zn2+ and S2− ions. Furthermore, we compared the products obtained from zinc ethylxanthate (Zn(C2H5OCS2)2) and zinc amylxanthate (Zn(C5H11OCS2)2). The as-prepared ZnS NPs were found to crystallize in cubic phase, which usually forms at low temperatures, with the dimension dependent on the xanthate precursor used. The long carbon-chain xanthate Zn(C5H11OCS2)2 gave spherically shaped NPs with an average diameter of 19 nm, while the NPs that originated from zinc ethylxanthate had a mean size of ~26 nm. Both nanomaterials had surface sulfur vacancies that extended their absorption spectra toward the visible region and reduced the band gap. This allowed both materials to demonstrate photocatalytic performance under visible-light irradiation. Photodegradation of methylene blue over newly prepared ZnS NPs was tested under visible light, demonstrating efficiency of 50%–60% after 180 min.

Green synthesized carbon quantum dots as TiO2 sensitizers for photocatalytic hydrogen evolution

Carbon quantum dots (CQDs) have attracted growing interest due to their superior luminescent properties, which make them excellent photosensitizers for TiO2. This study presents the green-synthesis of CQDs from edible mushroom Agaricus bisporus through microwave irradiation. In the study as-synthesized CQDs were used as a sensitizer for TiO2 in photocatalytic hydrogen evolution in aqueous triethanolamine (sacrificial reagent) under visible-light irradiation. Photocatalytic hydrogen production activity of CQD-sensitized TiO2 was found to be 472 μmol g−1 h−1 (without loading any noble metal co-catalyst) and 1458 μmol g−1 h−1 (with loading Pt co-catalyst). The study revealed that the CQDs from mushroom A. bisporus can be used as an efficient sensitizer for TiO2 in photocatalytic hydrogen production.

The Enhancement of H2 Evolution over Sr1-1.5xTbxWO4 Solid Solution under Ultraviolet Light Irradiation.

In this work, Sr1−1.5xTbxWO4 (0 ≤ x ≤ 0.2) solid solutions were synthesized via a traditional high-temperature solid state method. Le Bail fitting on the powder X-ray diffraction (XRD) pattern showed that these solid solutions are pure phase. Scanning electron microscopy showed that the SrWO4 and Sr0.82Tb0.12WO4 samples are composed of micrometer particles and submicron crystallites, respectively. Ultraviolet–visible diffuse reflectance spectra suggested that the bandgaps of Sr1−1.5xTbxWO4 are narrower than the undoped sample. The Sr0.82Tb0.12WO4 sample, with the assistance of 1.5 wt % Ru-cocatalyst, exhibits the best performance for H2 evolution in 5 vol % aqueous triethanolamine (TEOA), which results in about 6.1 and 2.8 times efficiency improvement compared with the intrinsic SrWO4 in methanol and aqueous TEOA, respectively. All the photocatalysts recycled after the photocatalytic reactions showed no degradation when checked by powder XRD.

Kinetics and new mechanism study of CO2 absorption into water and tertiary amine solutions by stopped‐Flow technique

The objective of the present work was to find the accurate kinetic models and mechanism for CO2 absorption into tertiary amine solution, aiming at understanding the contribution of the CO2 reaction with H2O, OH−, and tertiary amines on the overall reaction rate. First, the kinetics of CO2 absorption into water instead of a buffer solution were studied using the stopped‐flow technique at 293–313 K, with initial CO2 molar concentration of 1.1–37.3 mM. The experimental first‐order reaction rate constant () was determined to be about 1000 times larger than the value for CO2 absorption into buffer solution reported in the reference. The was then correlated by a proposed semiempirical model and a simplified theoretical model, giving the activation energy for CO2 reacting with H2O as fitted by the simplified theoretical model in good agreement with the value of previous research. Also, the pH values and hydroxyl ion concentrations of aqueous Diethylaminoethanol (DEEA) solutions were determined at 293–313 K, with DEEA molar concentration of 0.1–0.4 M and CO2 loading of 0–0.626 mol/mol. In addition, the observed first‐order reaction rate constant ( k0_DEEA) of binary DEEA‐H2O solution with DEEA molar concentration of 0.1–0.4 M reacting with CO2 was determined at 293–313 K. It should be pointed out that the kinetic experiments of CO2 absorption into DEEA solution was done with the molar ratio of DEEA to CO2 fixed at 20. The values of k0_DEEA were then fitted and predicted by four models (i.e., termolecular model, base‐catalyzed model, the improved model, and Khalifah model). The results show the improved model and Khalifah model can predict k0_DEEA well with an average absolute relative difference (AARD) <5%. The predicted results indicate that the contribution of OH− to k0_DEEA cannot be ignored for the absorption of CO2 into tertiary amine solutions, and could be responsible for 50–70% of the total absorption reaction rate. Furthermore, the k0 value of CO2 absorption into aqueous triethanolamine and CO2‐loaded DEEA solution were further investigated and comprehensively discussed, suggesting that both pK a and the CO2 solubility affect k0, with pK a having a much more significant effect. © 2018 American Institute of Chemical Engineers AIChE J, 65: 652–661, 2019

Quantification of synthetic food dyes in beverages or pharmaceutical tablets by solid phase extraction (spe) followed by UV/VIS spectrophotometry

Synthetic food dyes (E102, E104, E110, E122, E124, E132, E133) were concentrated by solid phase extraction on aminopropyl modified silica with aqueous sodium hydroxide or selected amines as eluents. Ponceau 4R (E124) was used as the model dye in the studies of the elution step. The recoveries of E124 differed depending on the eluent and ranged from 76% (AMP) to over 90% (TEA, imidazole, NaOH). Diluted aqueous triethanolamine (TEA) was found to be a suitable eluent for E124 but other dyes were eluted more effectively with NaOH. The solid extraction process was combined with UV/VIS spectroscopy to quantify synthetic dyes in drinks and OTC pharmaceutical tablets. The SPE-UV/VIS spectroscopic method was validated in terms of linearity, accuracy (recovery of dyes from spiked preparations), precision (repeatability, intermediate precision) and limits of detection/quantification. The method was found sufficiently fast, easy and reliable for the routine control of dyes in these types of products.

A consensus conference for cognitive endpoints for clinical trials and natural history studies in MPS diseases

SnS nano-particles are synthesized wet chemically using SnCl2.2H2O (tin(II) chloride) as Sn source and C2H5NS (thioacetamide) as S source in aqueous triethanolamine. Ammonia solution is used to maintain the pH ∼12 at room temperature. This step produces dark brown SnSx (x>1), which is bath sonicated with occasional stirring for 20 minutes for preventing the particles from agglomerating, followed by washing, drying and annealing at 500 °C in N2 atmosphere for 1 hr to obtain nearly phase pure SnS. The as-prepared SnS exhibits spherical morphology with average particle size in the range of 30 to 60 nm