64-18-6Relevant articles and documents
Synergistic activating effect of promoter and oxidant in single step conversion of methane into methanol over a tailored polymer-Ag coordination complex
Shavi, Raghavendra,Hiremath, Vishwanath,Sharma, Aditya,Won, Sung Ok,Seo, Jeong Gil
, p. 24168 - 24176 (2017)
Single-step conversion of methane to its oxygenated derivatives, such as methanol, is a challenging topic in C1 chemistry. The presence of Br?nsted-acidic sites, N- and O-type chelating ligands, and noble metals are demonstrated to be essential criteria for effective catalysis of this reaction. Considering these criteria, a catalytic complex was tailored herein. Poly-d-glucosamine (Ch) was used as chelating ligand for Ag, to incorporate the robust redox properties of Ag(i). The prepared AgCh complex was characterized by techniques including solid-state 1H-NMR, FE-TEM, XANES, and XPS. Besides highlighting the utility of chelate complexation for providing new materials, this study elucidates the effects of the oxidant and promoters on the methane oxidation. The catalytic activity was tested for different oxidant combinations, including hydrogen peroxide, oxygen, and carbon dioxide. Of all of them, a mixture of hydrogen peroxide and oxygen showed the highest selectivity for oxidation of methane to methanol. Further, it was observed that the addition of 1-butyl-3-methylimidazolium chloride [BMIM]+Cl- as a promoter to the hydrogen peroxide and oxygen-containing AgCh system could enhance methanol production. The methanol yield reached up to 3166 μmol, representing an 18-fold yield increase and an 8-fold methane conversion increase when compared to the results (175 μmol) without a promoter.
Mechanism of the Photooxidation of Formaldehyde Studied by Flash Photolysis of CH2O-O2-NO Mixtures
Veyret, Bernard,Rayez, Jean-Claude,Lesclaux, Robert
, p. 3424 - 3430 (1982)
The mechanism of the chain process leading to formic acid in the photooxidation of CH2O has been studied with the flash photolysis technique.Mixtures of CH2O, O2, and NO were photolyzed and the rate of appearance and yield of NO2 were monitored.Kinetic simulations of both sets of data allowed the determination of the rate constants for the main reactions HO2 + CH2O -> O2CH2OH (6), OCH2OH + O2 -> HO2 + HCO2H (8), OCH2OH + NO -> products (9) (k6=(7.5 +/-3.5)E-14; k8=(3.5 +/-1.6)E-14; k9=(4.0 +/-1.9)E-11 cm3molecule-1s-1).Quantum calculations provided estimates of the heats of formation for the radicals involved.The effect of temperature was investigated, suggesting the importance of the decomposition of the radical HOCH2O into H atom and formic acid.The validity of the global scheme is discussed along with its importance for the removal of CH2O and the production of formic acid in the athmosphere.
Drastically enhanced visible-light photocatalytic degradation of colorless aromatic pollutants over TiO2 via a charge-transfer-complex path: A correlation between chemical structure and degradation rate of the pollutants
Wang, Nan,Zhu, Lihua,Huang, Yingping,She, Yuanbin,Yu, Yanmin,Tang, Heqing
, p. 199 - 206 (2009)
Photocatalytic degradation of colorless aniline and phenolic pollutants was investigated over TiO2 under visible-light irradiation, which was confirmed to proceed via a charge-transfer-complex (CTC)-mediated pathway. The correlation between the chemical structure and the degradation rate of these pollutants was established experimentally and theoretically. It was found that an electron-donating substituent in benzene ring, which raises the highest occupied molecular orbital and lowers the ionization potential of the organic compound, is favorable to the CTC-mediated photodegradation of the pollutant, but an electron- withdrawing substituent has a reversed effect. The addition of sacrificial electron acceptors was adopted to enhance the degradation and mineralization of the aromatic pollutants. The increased degradation rate by 3 to 10 times suggests that the CTC-mediated photocatalytic technique has promising applications in the removal of colorless organic pollutants in the presence of sacrificial electron acceptors.
MnO2 Electrocatalysts Coordinating Alcohol Oxidation for Ultra-Durable Hydrogen and Chemical Productions in Acidic Solutions
Chen, Lisong,Han, Shuhe,Li, Yan,Shi, Jianlin,Wei, Xinfa
, p. 21464 - 21472 (2021)
Electrocatalytic hydrogen production under acidic conditions is of great importance for industrialization in comparison to that in alkaline media, which, unfortunately, still remains challenging due to the lack of earth-abundant, cost-effective and highly active anodic electrocatalysts that can be used durably under strongly acidic conditions. Here we report an unexpected finding that manganese oxide, a kind of common non-noble catalysts easily soluble in acidic solutions, can be applied as a highly efficient and extremely durable anodic electrocatalyst for hydrogen production from an acidic aqueous solution of alcohols. Particularly in a glycerol solution, a potential of as low as 1.36 V (vs. RHE) is needed at 10 mA cm?2, which is 270 mV lower than that of oxygen evolution reaction (OER), to oxidize glycerol into value-added chemicals such as formic acid, without oxygen production. To our surprise, the manganese oxide exhibits extremely high stability for electrocatalytic hydrogen production in coupling with glycerol oxidation for longer than 865 hours compared to shorter than 10 h for OER. Moreover, the effect of the addition of glycerol on the electrochemical durability has been probed via in situ Raman spectroscopic analysis and density functional theory (DFT) calculations. This work demonstrates that acid-unstable metal oxide electrocatalysts can be used robustly in acidic media under the presence of certain substances for electrochemical purposes, such as hydrogen production.
SYNTHESIS OF D-RIBO-C-NUCLEOSIDE ANALOGUES BY DEHYDRATION OF NEW D-ALLO-PENTITOL-1-YL HETEROCYCLES
Perez, Juan A. Galbis,Caballero, Reyes Babiano,Ventula, Arturo Cert
, p. 129 - 142 (1985)
The reaction of 2-amino-2-deoxy-D-glycero-D-altro-heptose hydrochloride with acyclic and cyclic 1,3-dicarbonyl compounds gives, respectively, (D-allo-pentitol-1-yl)-pyrroles and -tetrahydroindoles that can be dehydrated to yield D-ribo-C-glycosyl heterocycles having furanoid or pyranoid structures, depending on the reaction conditions.Thus, when the reactions were kinetically controlled, α- and β-D-ribofuranosyl heterocycles were obtained, but α- and β-D-ribopyranosyl heterocycles were formed under conditions of thermodynamic control.A criterion is proposed to differentiate between both structures on the basis of the mass spectra of their triacetates.
Formate ester Norrish Type II elimination: Diode laser probing of gas-phase yields
Niu, Yuping,Christophy, Elizabeth,Pisano, Patrick J.,Zhang, Ying,Hossenlopp, Jeanne M.
, p. 4181 - 4187 (1996)
Time-resolved infrared absorption spectroscopy was utilized to monitor the production of HCOOH, CO2, and CO following ultraviolet laser excitation of gas-phase formate esters. Excitation of ethyl formate at 227.5 nm resulted in formation of HCOOH and CO2. The CO2 quantum yield was estimated to be 0.5 ± 0.1. No evidence for CO formation was obtained at this wavelength. Relative quantum yields for the Norrish Type II elimination of HCOOH from ethyl, n-propyl, n-butyl, isopropyl, isobutyl, and tert-butyl formate were obtained at 227.5 and 222 nm. Normalization of the observed HCOOH yields with respect to the number of γ-hydrogen atoms resulted in reactivity trends at 227.5 nm of 1:3:9 for the abstraction of primary, secondary, and tertiary hydrogen atoms, respectively. At 222 nm, a similar reactivity trend was observed with yields per available γ-hydrogen of 1:3:7 for abstraction of primary, secondary, and tertiary hydrogen atoms. Yields were found to be independent of ester pressure over the range 100-550 mTorr. Semiempirical and ab initio calculations of the excited state hydrogen abstraction step were performed and enthalpies of activation of 8-12 kcal/mol were obtained using AM1 with configuration interaction.
Cerium Doped Pt/TiO2 for Catalytic Oxidation of Low Concentration Formaldehyde at Room Temperature
Shi, Yuanyuan,Qiao, Zhiwei,Liu, Zili,Zuo, Jianliang
, p. 1319 - 1325 (2019)
Abstract: Formaldehyde is a carcinogenic and teratogenic toxic gas. With the extensive use of a variety of building materials, indoor formaldehyde has seriously threatened human health and environment. The catalytic oxidation is considered the most promising method for the removal of formaldehyde from air. In this work, we report a Pt/TiO2 catalyst with Ce modification, and investigate its activity of catalytic oxidation of low concentration formaldehyde at room temperature. The experimental results show that the trace formaldehyde (20?mg/m3) could be completely degraded at 55?min by using Pt–Ce/TiO2 catalyst. In view of multiple characterizations, such as BET, XRD, TEM, STEM, XPS and CO adsorption, it is indicated that the modification of Ce can effectively improve the dispersion of Pt particles in the surface and reduction of Pt particle size from 2.9 to 2.2?nm. Moreover, XPS results show that the Ce in the catalyst could enhance the binding energies of Pt, provide abundant oxygen vacancies, and could increase the ratio of adsorbed oxygen atoms to lattice oxygen atoms, which is conducive to the adsorption of oxygen, leading to the improvement of catalytic activity. Graphical Abstract: [Figure not available: see fulltext.].
Micellar effect on the reaction of chromium(VI) oxidation of L-sorbose in the presence and absence of picolinic acid in aqueous acid media: A kinetic study
Saha, Bidyut,Das, Mahua,Mohanty, Rajani K.,Das, Asim K.
, p. 399 - 408 (2014)
The kinetics and mechanism of chromic acid oxidation of L-sorbose in the presence and absence of picolinic acid (PA) have been studied under the conditions, [L-sorbose]T >> [PA]T >> [Cr(VI)]T, at different temperatures. In the absence of PA, the monomeric
Oxidation of aldehydes with permanganate in acidic and alkaline media
Jaky,Szammer
, p. 420 - 426 (1997)
The oxidation mechanism of aldehydes with permanganate was studied in acidic and alkaline media on acetaldehyde, propionaldehyde, pivalaldehyde (2,2′-dimethylpropanal) and chloral substrates. On addition of water to acetaldehyde dissolved in organic solvents the rate increased, and therefore it may be stated that the hydrate form is more reactive than the aldehyde form. Acid-catalysed nucleophilic addition of permanganate is suggested. In alkaline medium a mechanism based on electron abstraction from the alkoxy anion of the hydrate is proposed. Deprotonation constants of hydrate could be calculated..
Photocatalytic degradation of chlorinated ethanes in the gas phase on the porous TiO2 pellets: Effect of surface acidity
Yamazaki, Suzuko,Ichikawa, Keiko,Saeki, Atsue,Tanimura, Toshifumi,Adachi, Kenta
, p. 5092 - 5098 (2010)
The photocatalytic degradation of chlorinated ethanes was studied in a tubular photoreactor packed with TiO2 pellets prepared by sol-gel method. The steady-state condition was not obtained, but the deterioration in the photocatalytic activity was observed during the irradiation. Effects of mole fractions of water vapor, O2, and C2H5Cl or C2H4Cl2 and reaction temperature on the photodegradation of C2H5Cl or C2H 4Cl2 were examined, and these data were compared with those obtained by the photodegradation of chlorinated ethylenes. On the basis of the products detected with and without oxygen in the reactant's gas stream, we proposed the degradation mechanism. Measurement of diffuse reflectance infrared Fourier transform spectroscopy of pyridine adsorbed on the catalysts showed that decrease in the conversion for the photodegradation of C2H 5Cl was attributable to the formation of Bronsted acid sites. Comparison of the data obtained with the TiO2 and the sulfated TiO2 (SO42-/TiO2) pellets indicated that the photodegradation of C2H5Cl was suppressed by the presence of the Bronsted sites, but that of trichloroethylene was not affected. Such a difference is attributable to the adsorption process of these reactants on the acid sites on the catalyst surface.
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Neuberg,Kobel
, p. 298,301 (1935)
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WET OXIDATION OF MODEL CARBOHYDRATE COMPOUNDS
McGinnis, Gary D.,Prince, Shawn E.,Biermann, Chris J.,Lowrimore, James T.
, p. 51 - 60 (1984)
The major product formed by wet oxidation of a series of model compounds: D-xylose, D-glucose, D-glucitol, cellulose, and dextran, was formic acid.Its yield varied according to the structure of the carbohydrate, oxygen pressure, temperature, and the presence or absence of ferric sulfate.Acetic acid was also formed; its yield was much less dependent on the structure of carbohydrate.Other products formed include methanol, acetaldehyde, acetone, and a series of hydroxylated acids.
Efficient Electrochemical Reduction of Carbon Dioxide to Acetate on Nitrogen-Doped Nanodiamond
Liu, Yanming,Chen, Shuo,Quan, Xie,Yu, Hongtao
, p. 11631 - 11636 (2015)
Electrochemical reduction of CO2 is an attractive technique for reducing CO2 emission and converting it into useful chemicals, but it suffers from high overpotential, low efficiency or poor product selectivity. Here, N-doped nanodiam
Mechanism of C-C bond formation in the electrocatalytic reduction of CO2 to acetic acid. A challenging reaction to use renewable energy with chemistry
Genovese, Chiara,Ampelli, Claudio,Perathoner, Siglinda,Centi, Gabriele
, p. 2406 - 2415 (2017)
Copper nanoparticles on carbon nanotubes are used in the reduction of CO2 to acetic acid (with simultaneous water electrolysis) in a flow electrocatalytic reactor operating at room temperature and atmospheric pressure. A turnover frequency of about 7000 h-1 and a carbon-based Faradaic selectivity to acetic acid of about 56% were observed, indicating potential interest in this approach for using renewable energy. The only other products of reaction detected were formic acid and methanol (the latter in some cases), besides H2. The reaction mechanism, particularly the critical step of C-C bond formation, was studied by comparing the reactivity in tests with CO2 or CO, where formic acid or formaldehyde where initially added. The results indicate the need for having dissolved CO2 to form acetic acid, likely via the reaction of CO2?- with surface adsorbed -CH3 like species. The pathway towards formic acid is instead different from the route of the formation of acetic acid.
Mechanism of methylphosphonic acid photo-degradation based on phosphate oxygen isotopes and density functional theory
Xia, Congcong,Geng, Huanhuan,Li, Xiaobao,Zhang, Yiyue,Wang, Fei,Tang, Xiaowen,Blake,Li, Hui,Chang, Sae Jung,Yu, Chan
, p. 31325 - 31332 (2019)
Methylphosphonic acid (MPn) is an intermediate in the synthesis of the phosphorus-containing nerve agents, such as sarin and VX, and a biosynthesis product of marine microbes with ramifications to global climate change and eutrophication. Here, we applied the multi-labeled water isotope probing (MLWIP) approach to investigate the C-P bond cleavage mechanism of MPn under UV irradiation and density functional theory (DFT) to simulate the photo-oxidation reaction process involving reactive oxygen species (ROS). The results contrasted with those of the addition of the ROS-quenching compounds, 2-propanol and NaN3. The degradation kinetics results indicated that the extent of MPn degradation was more under alkaline conditions and that the degradation process was more rapid at the initial stage of the reaction. The phosphate oxygen isotope data confirmed that one exogenous oxygen atom was incorporated into the product orthophosphate (PO4) following the C-P bond cleavage, and the oxygen isotopic composition of this free PO4 was found to vary with pH. The combined results of the ROS-quenching experiments and DFT indicate that the C-P bond was cleaved by OH-/OH and not by other reactive oxygen species. Based on these results, we have established a mechanistic model for the photolysis of MPn, which provides new insights into the fate of MPn and other phosphonate/organophosphate compounds in the environment.
Kinetics of the Ru(III) Catalyzed Oxidation of Formaldehyde and Acetaldehyde by Alkaline Hexacyanoferrate(III)
Awasthi, Anil K.,Upadhyay, Santosh K.
, p. 729 - 736 (1985)
The kinetics of ruthenium(III) catalyzed oxidation of formaldehyde and acetaldehyde by alkaline hexacyanoferrate(III) has been studied spectrophotometrically.The rate of oxidation of formaldehyde is directly proportional to while that of acetaldehyde is proportional to k/>, where k, k' and k" are rate constants.The order of reaction in acetylaldehyde is unity while that in formaldehyde falls from 1 to 0.The rate of reaction is proportional to T in each case.A suitable mechanism is proposed are discussed. -Keywords: Kinetics; Mechanism; Oxidation; Ru(III) catalyzed
Grundmann,Kreutzberger
, (1954)
Conversion of saccharides into formic acid using hydrogen peroxide and a recyclable palladium(ii) catalyst in aqueous alkaline media at ambient temperatures
Zargari,Kim,Jung
, p. 2736 - 2740 (2015)
We have developed an effective method that converts a variety of mono- and disaccharides into formic acid predominantly. Our recyclable NHC-amidate palladium(ii) catalyst facilitated oxidative degradation of carbohydrates without using excess oxidant. Stoichiometric amounts of hydrogen peroxide and sodium hydroxide were employed at ambient temperatures.
In situ infrared study of photoreaction of ethanol on Au and Ag/TiO2
Rismanchian, Azadeh,Chen, Yu-Wen,Chuang, Steven S.C.
, p. 16 - 22 (2016)
An in situ IR technique was used to study the role of Au and Ag additives on photocatalytic reaction of ethanol on TiO2 at 300 K. Au and Ag additives increased water/ethanol coverage and decreased the rate of ethanol's C-H scission, a step involving in scavenging photogenerated holes. Au and Ag promoted adsorption of ethanol as monodentate ethoxy, accelerated its conversion to formate (HCOO-ad) and acetate (CH3COO-ad). In contrast, adsorbed ethanol on TiO2 did not produce IR-observable products and exhibited a Stark effect with a decreased C-H intensity upon accumulation of photogenerated electrons.
KINETICS AND MECHANISM OF OXIDATION OF SOME ALCOHOLS BY OSMIUM TETROXIDE
Singh, Bharat,Singh, A. K.,Singh, M. B.,Singh, A. P.
, p. 715 - 718 (1986)
Spectrophotometric studies of the kinetics of oxidation of 2-methylpropan-1-ol and 2-butanol by an alkaline solution of osmium tetroxide have been reported.A first-order dependence to osmium tetroxide was observed.A first-order dependence to both 2-methylpropan-1-ol and alkali at low concentration tends to zero order at higher concentrations.In the case of 2-butanol, first-order kinetics is exhibited with respect to 2-butanol but first-order kinetics observed at lower concentrations of alkali decrease at higher concentrations.A negligible ionic strength effect of the medium was observed.Activation parameters have been computed.A suitable mechanism in conformity with our kinetic observations has been suggested.
Multiple isotope effect study of the acid-catalyzed hydrolysis of formamide
Marlier, John F.,Campbell, Erica,Lai, Catherine,Weber, Michael,Reinhardt, Laurie A.,Cleland
, p. 3829 - 3836 (2006)
Multiple isotope effects were measured at the reactive center of formamide during acid-catalyzed hydrolysis in water at 25 °C. The mechanism involves a rapid pre-equilibrium protonation of the carbonyl oxygen, followed by the formation of at least one tetrahedral intermediate, which does not appreciably exchange its carbonyl oxygen with the solvent (kh/kcx = 55). The pKa for formamide was determined by 15N NMR and found to be about -2.0. The formyl-hydrogen kinetic isotope effect (KIE) is indicative of a transition state that is highly tetrahedral (Dk obs = 0.79); the carbonyl-carbon KIE (13kobs = 1.031) is in agreement with this conclusion. The small leaving-nitrogen KIE (15kobs = 1.0050) is consistent with some step prior to breaking the C-N bond as rate-determining. The carbonyl-oxygen KIE ( 18kobs = 0.996) points to attack of water as the rate-determining step. On the basis of these results, a mechanism is proposed in which attachment of the nucleophile to a protonated formamide molecule is rate determining.
Spectroscopic and electrochemical characterization of heteropoly acids for their optimized application in selective biomass oxidation to formic acid
Albert, Jakob,Lueders, Daniela,Boesmann, Andreas,Guldi, Dirk M.,Wasserscheid, Peter
, p. 226 - 237 (2014)
Different Keggin-type polyoxometalates have been synthesized and characterized in order to identify optimized homogeneous catalysts for the selective oxidation of biomass to formic acid (FA) using oxygen as an oxidant and p-toluenesulfonic acid as an additive. Applying the optimized polyoxometalate catalyst system H8[PV5Mo7O 40] (HPA-5), a total FA-yield (with respect to carbon in the biogenic feedstock) of 60% for glucose within 8 h reaction time and 28% for cellulose within 24 h reaction time could be achieved. The transformation is characterized by its mild reaction temperature, its excellent selectivity to FA in the liquid product phase and its applicability to a very wide range of biogenic raw materials including non-edible biopolymers and complex biogenic mixtures.
Nonuniform Electric Field-Enhanced In-Source Declustering in High-Pressure Photoionization/Photoionization-Induced Chemical Ionization Mass Spectrometry for Operando Catalytic Reaction Monitoring
Wan, Ningbo,Jiang, Jichun,Hu, Fan,Chen, Ping,Zhu, Kaixin,Deng, Dehui,Xie, Yuanyuan,Wu, Chenxin,Hua, Lei,Li, Haiyang
, p. 2207 - 2214 (2021)
Photoionization mass spectrometry (PI-MS) is a powerful and highly sensitive analytical technique for online monitoring of volatile organic compounds (VOCs). However, due to the large difference of PI cross sections for different compounds and the limitation of photon energy, the ability of lamp-based PI-MS for detection of compounds with low PI cross sections and high ionization energies (IEs) is insufficient. Although the ion production rate can be improved by elevating the ion source pressure, the problem of generating plenty of cluster ions, such as [MH]+·(H2O)n (n = 1 and 2) and [M2]+, needs be solved. In this work, we developed a new nonuniform electric field high-pressure photoionization/photoionization-induced chemical ionization (NEF-HPPI/PICI) source with the abilities of both HPPI and PICI, which was accomplished through ion-molecule reactions with high-intensity H3O+ reactant ions generated by photoelectron ionization (PEI) of water molecules. By establishing a nonuniform electric field in a three-zone ionization region to enhance in-source declustering and using 99.999% helium as the carrier gas, not only the formation of cluster ions was significantly diminished, but the ion transmission efficiency was also improved. Consequently, the main characteristic ion for each analyte both in HPPI and PICI occupied more than 80%, especially [HCOOH·H]+ with a yield ratio of 99.2% for formic acid. The analytical capacity of this system was demonstrated by operando monitoring the hydrocarbons and oxygenated VOC products during the methanol-to-olefins and methane conversion catalytic reaction processes, exhibiting wide potential applications in process monitoring, reaction mechanism research, and online quality control.
The Promotion Effect of NaCl on the Conversion of Xylose to Furfural?
Fang, Qianying,Hu, Changwei,Jiang, Zhicheng,Li, Zheng,Luo, Yiping
, p. 178 - 184 (2020)
In this work, the promotion effect of NaCl on the conversion of xylose to furfural in H2O was studied. It was found that xylose conversion and furfural yield increased with NaCl concentration. NaCl decreased the pH of the solution providing H+ for the acid catalytic dehydration of xylose. The formation of oligomers was determined by GPC and ESI-MS in the initial stage of reaction, especially at low temperature. Excess NaCl promoted the formation of humins in the late stage of the reaction. NaCl could also change the decomposition route of formic acid. Meanwhile, NaCl had the ability of phase separation. Combining these effects with organic solvent during the reaction could inhibit the formation of humins and increase the yield of furfural. In NaCl-H2O-THF biphasic system without other catalyst, the optimal furfural yield of 76.7% and selectivity of 77.6% were achieved at 463 K in 2 h.
Crystal structure of an S-formylglutathione hydrolase from pseudoalteromonas haloplanktis TAC125
Alterio, Vincenzo,Aurilia, Vincenzo,Romanelli, Alessandra,Parracino, Antonietta,Saviano, Michele,D'Auria, Sabato,de Simone, Giuseppina
, p. 669 - 677 (2010)
S-formylglutathione hydrolases (FGHs) constitute a family of ubiquitous enzymes which play a key role in formaldehyde detoxification both in prokaryotes and eukaryotes, catalyzing the hydrolysis of S-formylglutathione to formic acid and glutathione. While a large number of functional studies have been reported on these enzymes, few structural studies have so far been carried out. In this article we report on the functional and structural characterization of PhEst, a FGH isolated from the psychrophilic bacterium Pseudoalteromonas haloplanktis. According to our functional studies, this enzyme is able to efficiently hydrolyze several thioester substrates with very small acyl moieties. By contrast, the enzyme shows no activity toward substrates with bulky acyl groups. These data are in line with structural studies which highlight for this enzyme a very narrow acyl-binding pocket in a typical α/β-hydrolase fold. PhEst represents the first cold-adapted FGH structurally characterized to date; comparison with its mesophilic counterparts of known three-dimensional structure allowed to obtain useful insights into molecular determinants responsible for the ability of this psychrophilic enzyme to work at low temperature.
3D structured TiO2-based aerogel photocatalyst for the high-efficiency degradation of toluene gas
Dai, Li,Guan, Jie,Li, Shijie,Li, Xueying,Yu, Wei,Zhang, Li
, p. 2272 - 2281 (2022/02/16)
Photocatalytic technology is a green , environmentally friendly, energy-saving technology, which is considered to be an ideal method for removing volatile organic compounds (VOCs). At present, photocatalytic technology mostly uses powdered catalysts, which is not conducive to recycling and restricts the contact between the gas and catalyst. In this work, a three-dimensional (3D)-structured TiO2-based aerogel with TiO2 as the main body and all the components beneficial to photocatalysis was prepared for the first time. Under simulated sunlight irradiation, the toluene-removal rate of the Pt-loaded TiO2 and reduced graphene oxide (RGO) composite aerogel (denoted as Pt-TiO2/RGO aerogel, or PTA thereafter) was 60.47% higher than that of the pure RGO aerogel, and 56.03% higher than that of the bare TiO2 nanofibers. The block-shaped composite aerogel could be easily recycled, and the C/C0 of toluene using the recycled sample decreased by only 5.31% in the 5th run. The Pt-TiO2/RGO composite aerogel had the highest photocatalytic degradation rate of toluene with a relative humidity (RH) of 60-80%, which is conducive to the purification of VOCs in high-humidity areas. The 3D aerogel enriches the contact between the solid photocatalyst and the toluene molecules, and also solves the problem of low adhesion between the catalyst and the carrier. This work provides a new perspective for the efficient removal of toluene gas by constructing a highly active 3D TiO2 aerogel with an increased gas-solid reaction rate.
Photocatalytic removal of benzene over Ti3C2T: XMXene and TiO2-MXene composite materials under solar and NIR irradiation
Calvino, José J.,Constantinescu, Gabriel,Frade, Jorge R.,Kovalevsky, Andrei V.,Labrincha, Jo?o A.,Lajaunie, Luc,Lopes, Daniela V.,Sergiienko, Sergii A.,Shaula, Aliaksandr L.,Shcherban, Nataliya D.,Shkepu, Viacheslav I.,Tobaldi, David M.
, p. 626 - 639 (2022/01/22)
MXenes, a family of two-dimensional (2D) transition metal carbides, nitrides and carbonitrides based on earth-abundant constituents, are prospective candidates for energy conversion applications, including photocatalysis. While the activity of individual MXenes towards various photocatalytic processes is still debatable, these materials were proved to be excellent co-catalysts, accelerating the charge separation and suppressing the exciton recombination. Titanium-containing MXenes are well compatible with the classical TiO2 photocatalyst. The TiO2 component can be directly grown on MXene sheets by in situ oxidation, representing a mainstream processing approach for such composites. In this study, an essentially different approach has been implemented: a series of TiO2-MXene composite materials with controlled composition and both reference end members were prepared, involving two different strategies for mixing sol-gel-derived TiO2 nanopowder with the Ti3C2Tx component, which was obtained by HF etching of self-propagating high-temperature synthesis products containing modified MAX phase Ti3C2Alz (z > 1) with nominal aluminium excess. The prospects of such composites for the degradation of organic pollutants under simulated solar light, using benzene as a model system, were demonstrated and analysed in combination with their structural, microstructural and optical properties. A notable photocatalytic activity of bare MXene under near infrared light was discovered, suggesting further prospects for light-to-energy harvesting spanning from UV-A to NIR and applications in biomedical imaging and sensors.
Direct catalytic benzene hydroxylation under mild reaction conditions by using a monocationic μ-nitrido-bridged iron phthalocyanine dimer with 16 peripheral methyl groups
Tanaka, Kentaro,Teoh, Chee-Ming,Toyoda, Yuka,Yamada, Yasuyuki
supporting information, p. 955 - 958 (2022/02/07)
Direct catalytic hydroxylation of benzene under mild reaction conditions proceeded efficiently in the presence of a monocationic μ-nitrido-bridged iron phthalocyanine dimer with 16 peripheral methyl groups in an acetonitrile solution with excess H2O2. Mechanistic studies suggested that the reaction was catalyzed by a high-valent iron-oxo species generated in situ. Moreover, the peripheral methyl groups of the catalyst were presumed to have enhanced the production rate of the iron-oxo species.