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1.
Water Res ; 185: 116242, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32758791

RESUMO

Recently, an increasing number of pharmaceutical compounds has become fluorinated. Owing to their pharmacological efficacy, the use of these fluorinated pharmaceuticals continues to grow, and they constitute 20% of the drugs on the current market. However, only a few studies have investigated the fate and transformation of these emerging contaminants in natural and engineered aquatic environments. In the present study, the H2-based reductive transformation of three fluorinated pharmaceutical compounds (levofloxacin, sitagliptin, and fluoxetine) were investigated using alumina-supported monometallic and bimetallic catalysts of the Pt-group noble metals (i.e., Ru, Rh, Pd, and Pt) under ambient temperature and pressure conditions. Degradation of all three compounds was observed with catalytic reactivity ranging from 4.0  ×  10-3 to 2.14  ×  102 L/(min·gcat), in which fluoxetine generally showed the highest reactivity, followed by sitagliptin and levofloxacin. The fluorination yields and transformation products were characterized for each fluorinated compound and three different degradation mechanisms were elucidated: 1) hydrodefluorination of C-F bond to CH bond, 2) hydrogenation of aromatic ring, and 3) reductive cleavage of CO bond from phenyl ether. Toxicity assessment using Aliivibrio fischeri showed there were no significant changes in toxicity over levofloxacin and sitagliptin degradation, suggesting the formation of no highly toxic by-products during catalytic reduction. For fluoxetine, an increased toxicity was observed during its degradation while ECOSAR-predicted toxicity values of all identified intermediates were lower than that of fluoxetine, suggesting the formation of unidentified secondary by-products that contribute to the overall toxicity. The study showed that catalytic reduction is a promising remediation process for treating and defluorinating the fluorinated pharmaceutical compounds.


Assuntos
Halogenação , Preparações Farmacêuticas , Óxido de Alumínio , Catálise , Hidrogenação
2.
J Oleo Sci ; 69(8): 871-882, 2020 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-32641614

RESUMO

In this study, an N-heterocyclic carbene (NHC)-based metal coordinate surfactant (MCS), NHC-Au-MCS, in which the NHC framework afforded the bonding of the Au(I) at the linkage of the hydrophilic and hydrophobic moieties, was synthesized. The structure of NHC-Au-MCS was confirmed by 1H and 13C NMR spectroscopic measurements together with elemental analysis. Matrix-assisted laser desorption/ionization (MALDI), laser desorption/ionization (LDI), and electrospray ionization mass spectrometry (ESI-MS) indicated the distinct reactivity of NHC-Au-MCS, such as the exchange of Br to Cl and the formation of a cationic Au complex, where the two NHC ligands were coordinated to an Au(I) center upon laser activation. The surface tension and dynamic light scattering (DLS) measurements revealed that the coordination of Au(I) to NHC reduced the critical micelle concentration (CMC) of NHC-Au-MCS (1.3×10-5 M), which resulted in the formation of micelles at concentrations higher than the CMC in water. We also confirmed that the surface-active Au(I) complex of NHC-Au-MCS catalyzed the hydration of 1-dodecyne to 2-dodecanone in water in the absence of an organic solvent. On the basis of the detailed mechanistic investigations regarding the reactivity of NHC-Au-MCS, we revealed that NHC-Au-MCS partially translated into Au nanoparticles (AuNPs), which facilitated alkyne hydration. These mechanistic studies were supported by UV-vis measurements, transmission electron microscopy (TEM), and LDI-MS.


Assuntos
Alquinos/química , Ouro/química , Compostos Heterocíclicos/síntese química , Nanopartículas Metálicas/química , Metano/análogos & derivados , Tensoativos/síntese química , Catálise , Compostos Heterocíclicos/química , Hidrogenação , Interações Hidrofóbicas e Hidrofílicas , Metano/síntese química , Metano/química , Micelas , Tensoativos/química , Água
3.
J Oleo Sci ; 69(7): 659-670, 2020 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-32522940

RESUMO

This work investigated the crystallization and melting behavior of cocoa butter substitute (CBS) blended with two hard lauric fats: fully hydrogenated palm kernel oil (FHPKO) and krabok seed fat (KSF). The aim was to find a way to increase the heat resistance of CBS for the production of heat-resistant compound chocolate (HRCC). Adding FHPKO to CBS increased the crystallization rate with a decrease in crystallization induction time but did not increase the heat resistance. In contrast, all KSF-CBS blends exhibited higher heat resistance than CBS and crystallized into ß' form, a preferred polymorph for fats used in compound chocolate. Only the blends with 10-60% KSF melted completely at the body temperature, indicating that they would leave no waxy mouthfeel, but the blends with 30 and 40% KSF exhibited a significant decrease in the crystallization rate compared to the original CBS. Therefore, the KSF-CBS blends with 10, 20 and 60% KSF are recommended for future use as fats for HRCC production.


Assuntos
Chocolate , Cristalização , Gorduras na Dieta , Óleo de Palmeira/química , Óleos Vegetais/química , Sapindaceae/química , Sementes/química , Temperatura de Transição , Temperatura Corporal , Qualidade dos Alimentos , Temperatura Alta , Hidrogenação , Paladar
4.
J Environ Sci (China) ; 92: 106-117, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32430113

RESUMO

Direct synthesis of dimethyl ether (DME) by CO2 hydrogenation has been investigated over three hybrid catalysts prepared by different methods: co-precipitation, sol-gel, and solid grinding to produce mixed Cu, ZnO, ZrO2 catalysts that were physically mixed with a commercial ferrierite (FER) zeolite. The catalysts were characterized by N2 physisorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), temperature programmed desorption of CO2 (CO2-TPD), temperature programmed desorption of NH3 (NH3-TPD), and temperature programmed H2 reduction (H2-TPR). The results demonstrate that smaller CuO and Cu crystallite sizes resulting in better dispersion of the active phases, higher surface area, and lower reduction temperature are all favorable for catalytic activity. The reaction mechanism has been studied using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Methanol appears to be formed via the bidentate-formate (b-HCOO) species undergoing stepwise hydrogenation, while DME formation occurs from methanol dehydration and reaction of two surface methoxy groups.


Assuntos
Dióxido de Carbono , Catálise , Hidrogenação , Éteres Metílicos , Oxirredução
5.
Food Chem ; 326: 126973, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32413757

RESUMO

The aim of this study was to substitute part of soybean phospholipid (SPC) with hydrogenated soybean phospholipid (HSPC) in curcumin-loaded liposomes (Cur-LP), in order to further enhance stability and release performances of curcumin. When the SPC/HSPC mass ratio changed from 10:0 to 5:5, vesicle size, encapsulation efficiency and alkali resistance of curcumin increased, although a small decrease in centrifugal stability was observed. Salt stability became worse as more HSPC was used (3:7 and 0:10). Owing storage at 4 °C and 25 °C, Cur-LP at a SPC/HSPC mass ratio of 5:5 performed well considering vesicle size, lipid oxidation and curcumin retention. These vesicles displayed also the best sustained-release performance in simulated digestion, attributed to the tighter lipid packing in membranes as indicated by fluorescence probes, DSC and FTIR. This study can guide the development of a Cur-LP product with improved shelf-life stability by using HSPC.


Assuntos
Curcumina/farmacocinética , Lipossomos/química , Lipossomos/farmacocinética , Fosfolipídeos/química , Varredura Diferencial de Calorimetria , Liberação Controlada de Fármacos , Estabilidade de Medicamentos , Concentração de Íons de Hidrogênio , Hidrogenação , Lecitinas , Soja/química , Espectroscopia de Infravermelho com Transformada de Fourier
6.
Water Res ; 175: 115688, 2020 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-32171095

RESUMO

Ion exchange is widely used to treat nitrate-contaminated groundwater, but high salt usage for resin regeneration and management of waste brine residuals increase treatment costs and add environmental burdens. Development of palladium-based catalytic nitrate treatment systems for brine treatment and reuse has showed promising activity for nitrate reduction and selectivity towards the N2 over the alternative product ammonia, but this strategy overlooks the potential value of nitrogen resources. Here, we evaluated a hybrid catalytic hydrogenation/membrane distillation process for nitrogen resource recovery during treatment and reuse of nitrate-contaminated waste ion exchange brines. In the first step of the hybrid process, a Ru/C catalyst with high selectivity towards ammonia was found to be effective for nitrate hydrogenation under conditions representative of waste brines, including expected salt buildup that would occur with repeated brine reuse cycles. The apparent rate constants normalized to metal mass (0.30 ± 0.03 mM min-1 gRu-1 under baseline condition) were comparable to the state-of-the-art bimetallic Pd catalyst. In the second stage of the hybrid process, membrane distillation was applied to recover the ammonia product from the brine matrix, capturing nitrogen as ammonium sulfate, a commercial fertilizer product. Solution pH significantly influenced the rate of ammonia mass transfer through the gas-permeable membrane by controlling the fraction of free ammonia species (NH3) present in the solution. The rate of ammonia recovery was not affected by increasing salt levels in the brine, indicating the feasibility of membrane distillation for recovering ammonia over repeated reuse cycles. Finally, high rates of nitrate hydrogenation (apparent rate constant 1.80 ± 0.04 mM min-1 gRu-1) and ammonia recovery (overall mass transfer coefficient 0.20 m h-1) with the hybrid treatment process were demonstrated when treating a real waste ion exchange brine obtained from a drinking water utility. These findings introduce an innovative strategy for recycling waste ion exchange brine while simultaneously recovering potentially valuable nitrogen resources when treating contaminated groundwater.


Assuntos
Destilação , Nitrogênio , Hidrogenação , Troca Iônica , Nitratos , Sais
7.
Chemistry ; 26(39): 8555-8566, 2020 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-32203626

RESUMO

Diphenanthrioctaphyrin(1.1.1.0.1.1.1.0), an expanded carbaporphyrinoid incorporating two phenanthrenylene moieties, exists as two separate, yet interconvertible, locked stereoisomers. These species demonstrate complex dynamic behavior upon protonation, consisting in multiple conformational rearrangements and anion-binding events. The formation of one of the final dicationic forms is accompanied by the inclusion of a complex anion(s) within the macrocyclic cavity yielding a pseudorotaxane-like host-guest complex. Protonation with trifluoroacetic or dichloroacetic acids followed by neutralization afforded a conformation-switching cycle, which involves six structurally different species. Analogous acidification with chiral 10-camphorsulfonic acid and subsequent neutralization generated one of the free base stereoisomers with enantiomeric excess. Therefore, it was shown that the simple acid-base chemistry of diphenanthrioctaphyrin can act as stimulus, inducing chirality into the system, allowing for the manipulation of the stereochemical information imprinted into the enantiomers of the macrocycle.


Assuntos
Ânions/química , Rotaxanos/química , Hidrogenação , Conformação Molecular , Rotaxanos/síntese química , Estereoisomerismo
8.
Water Res ; 174: 115593, 2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-32086133

RESUMO

The catalytic hydrogel membrane reactor (CHMR) is an interfacial membrane process that uses nano-sized catalysts for the hydrogenation of oxidized contaminants in drinking water. In this study, the CHMR was operated as a continuous-flow reactor using nitrite (NO2-) as a model contaminant and palladium (Pd) as a model catalyst. Using the overall bulk reaction rate for NO2- reduction as a metric for catalytic activity, we evaluated the effect of the hydrogen gas (H2) delivery method to the CHMR, the initial H2 and NO2- concentrations, Pd density in the hydrogel, and the presence of Pd-deactivating species. The chemical stability of the catalytic hydrogel was evaluated in the presence of aqueous cations (H+, Na+, Ca2+) and a mixture of ions in a hard groundwater. Delivering H2 to the CHMR lumens using a vented operation mode, where the reactor is sealed and the lumens are periodically flushed to the atmosphere, allowed for a combination of a high H2 consumption efficiency and catalytic activity. The overall reaction rate of NO2- was dependent on relative concentrations of H2 and NO2- at catalytic sites, which was governed by both the chemical reaction and mass transport rates. The intrinsic catalytic reaction rate was combined with a counter-diffusional mass transport component in a 1-D computational model to describe the CHMR. Common Pd-deactivating species [sulfite, bisulfide, natural organic matter] hindered the reaction rate, but the hydrogel afforded some protection from deactivation compared to a batch suspension. No chemical degradation of the hydrogel structure was observed for a model water (pH > 4, Na+, Ca2+) and a hard groundwater after 21 days of exposure, attesting to its stability under natural water conditions.


Assuntos
Hidrogéis , Nitritos , Catálise , Hidrogenação , Oxirredução , Paládio
9.
Chem Commun (Camb) ; 56(21): 3119-3122, 2020 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-32090223

RESUMO

A highly efficient diastereoselective transfer hydrogenation of α-aminoalkyl α'-chloromethyl ketones catalyzed by a tethered rhodium complex was developed and successfully utilized in the synthesis of the key intermediates of HIV protease inhibitors. With the current Rh(iii) catalyst system, a series of chiral 3-amino-1-chloro-2-hydroxy-4-phenylbutanes were produced in excellent yields and diastereoselectivities (up to 99% yield, up to 99 : 1 dr). Both diastereomers of the desired products could be efficiently accessed by using the two enantiomers of the Rh(iii) catalyst.


Assuntos
Complexos de Coordenação/química , Cetonas/química , Ródio/química , Catálise , Inibidores da Protease de HIV/síntese química , Hidrogenação , Ligantes , Estrutura Molecular , Oxirredução , Estereoisomerismo , Relação Estrutura-Atividade
10.
J Chromatogr A ; 1619: 460955, 2020 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-32081485

RESUMO

The complexity of determining the composition of animal tissue lipids is greatly increased by the presence of plasmalogens in which the alkyl chain is linked to glycerol by an enol ether bond instead of being esterified. Acidic methanolysis of animal tissue lipids provides the simultaneous scission of acyl and alkenyl ether moieties, but the complexity of the products of reaction poses a great challenge in their gas chromatographic analysis. Two-dimensional gas chromatography with online reduction (GC-OR × GC) provided the resolution of all components contained in acid methanolyzed animal lipids, taking advantage of the selective hydrogenation of alkenyl ether methanolysis products prior to the second-dimension separation (2D). In this study, we also studied the chemical transformations occurring during the acidic methanolysis of animal lipids and the subsequent gas chromatographic analysis. In particular, we observed that using methanolysis reagents contaminated with water resulted in the undesired formation of fatty aldehydes, and we made recommendations on how to avoid these side reactions using proper methanolysis conditions. Products of acidic methanolysis were studied by GC-OR × GC, GC-MS, NMR spectroscopy, and GC with flame ionization detection (GC-FID). We defined the GC-FID elution order of animal lipid acidic methanolysis products using 100 m × 0.25 mm 100% bis(cyanopropyl)siloxane columns and two different set of elution conditions: isothermal elution at 180°C, and a temperature program optimized for dairy fats. A simple procedure for isolating dimethyl acetals (DMA) prior to GC analysis is also described.


Assuntos
Técnicas de Química Analítica/métodos , Cromatografia Gasosa , Lipídeos/química , Acetais/isolamento & purificação , Tecido Adiposo/química , Animais , Hidrogenação , Metabolismo dos Lipídeos , Espectroscopia de Ressonância Magnética , Plasmalogênios/química , Plasmalogênios/metabolismo , Siloxanas/química , Temperatura
11.
Chemistry ; 26(20): 4489-4495, 2020 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-32073730

RESUMO

It is challenging to design metal catalysts for in situ transformation of endogenous biomolecules with good performance inside living cells. Herein, we report a multifunctional metal catalyst, ruthenium-coordinated oligo(p-phenylenevinylene) (OPV-Ru), for intracellular catalysis of transfer hydrogenation of nicotinamide adenine dinucleotide (NAD+ ) to its reduced format (NADH). Owing to its amphiphilic characteristic, OPV-Ru possesses good self-assembly capability in water to form nanoparticles through hydrophobic interaction and π-π stacking, and numerous positive charges on the surface of nanoparticles displayed a strong electrostatic interaction with negatively charged substrate molecules, creating a local microenvironment for enhancing the catalysis efficiency in comparison to dispersed catalytic center molecule (TOF value was enhanced by about 15 fold). OPV-Ru could selectively accumulate in the mitochondria of living cells. Benefiting from its inherent fluorescence, the dynamic distribution in cells and uptake behavior of OPV-Ru could be visualized under fluorescence microscopy. This work represents the first demonstration of a multifunctional organometallic complex catalyzing natural hydrogenation transformation in specific subcellular compartments of living cells with excellent performance, fluorescent imaging ability, specific mitochondria targeting and good chemoselectivity with high catalysis efficiency.


Assuntos
Complexos de Coordenação/química , Mitocôndrias/química , Polivinil/química , Rutênio/química , Catálise , Hidrogenação , Interações Hidrofóbicas e Hidrofílicas , Mitocôndrias/metabolismo , Nanopartículas , Água
12.
Chemistry ; 26(31): 7083-7091, 2020 Jun 02.
Artigo em Inglês | MEDLINE | ID: mdl-32073723

RESUMO

The electron donor tetrathiafulvalene (D1 ) was fused onto the electron-rich heterabuckybowl trichalcogenasumanene (D2 ) through an electron-deficient pyrazine unit (A) to give 1 c, 1 d, 2 c, and 2 d, featuring the D1 -A-D2 structure. Both D1 and D2 play a pivotal role in intramolecular charge-transfer (ICT) transitions, consequently 1 c, 2 d, 2 c, and 2 d show a broad ICT band at 450-720 nm in steady state. They exhibit two charge-separated transient states, CS1 and CS2 , that appear in sequence. CS1 has a short lifetime (542 fs), and the D1 moiety on CS1 is in the radical cation state with an absorption maximum (λmax ) at 889 nm. CS1 then converts into CS2 (λmax , 1105 nm) through an ICT between D1 .+ and D2 , affording D1 (1-δ).+ and D2 δ.+ . Compounds 1 c, 1 d, 2 c, and 2 d show protonation-induced intramolecular electron transfer that leads to absorption at λ=700-1300 nm. Owing to the existence of an electron-rich C=C bond on the D1 moiety and in situ generation of 1 O2 by the pyrazine-fused D2 moiety, compounds 1 c, 1 d, 2 c, and 2 d display self-sensitized photooxidation in 50 s.


Assuntos
Compostos Heterocíclicos/química , Pirazinas/química , Transporte de Elétrons , Elétrons , Hidrogenação , Estrutura Molecular
13.
Molecules ; 25(4)2020 Feb 23.
Artigo em Inglês | MEDLINE | ID: mdl-32102166

RESUMO

A family of complexes of the formula trans-[RuCl2(L)(R-pybox)] (R-pybox = (S,S)-iPr-pybox, (R,R)-Ph-pybox, L = monodentate phosphonite, PPh(OR)2, and phosphinite, L = PPh2(OR), ligands) were screened in the catalytic asymmetric transfer hydrogenation of acetophenone, observing a strong influence of the nature of both the R-pybox substituents and the L ligand in the process. The best results were obtained with complex trans-[RuCl2{PPh2(OEt)}{(R,R)-Ph-pybox}] (2c), which provided high conversion and enantioselectivity (up to 96% enantiomeric excess, e.e.) for the reduction of a variety of aromatic ketones, affording the (S)-benzylalcohols.


Assuntos
Cetonas/química , Oxazóis/química , Compostos de Fósforo/química , Piridinas/química , Rutênio/química , Acetofenonas/química , Catálise , Complexos de Coordenação/química , Cristalografia por Raios X , Hidrogenação , Isomerismo , Ligantes , Fosfinas/química , Fosfitos/química
14.
Carbohydr Res ; 489: 107948, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32062397

RESUMO

Rh/Al2O3 can be used as an effective chemo-selective reductive catalyst that combines the mild conditions of catalytic hydrogenation with high selectivity for azide moieties in the presence of other hydrogenolysis labile groups such as benzyl and benzyloxycarbonyl functionalities. The practicality of this strategy is exemplified with a range of azide-containing carbohydrate and amino acid derivatives.


Assuntos
Aminas/síntese química , Azidas/química , Ródio/química , Aminas/química , Configuração de Carboidratos , Catálise , Hidrogenação
15.
Chemosphere ; 243: 125387, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31995867

RESUMO

Hollow porous carbon has attracted a great deal of interest as catalyst-support because of its high surface area, low density and large pore volume. Herein, we develop a layer-by-layer assembly method to effectively load Pt nanoparticles on hollow porous carbon nanospheres (Pt/HPC) through using modified-SiO2 nanospheres as the template and agar as the carbon resource. The gel properties of agar (e.g., sensitivity to temperature and high mechanical strength) makes the Pt nanoparticles well crosslink with carbon, as well as endows the carbon nanospheres with robust stability. The synthesized Pt/HPC was employed as a catalyst in the hydrogenation reduction of rhodamine B (RhB). The catalytic results demonstrate that Pt/HPC is very promising for RhB hydrogenation as compared to commercial Pt/C catalyst. It is proven that such excellent activity of Pt/HPC can be attributed to the combined merits of hollow porous architecture and well combination between HPC and Pt nanoparticles.


Assuntos
Ágar/química , Nanosferas/química , Platina/química , Rodaminas/química , Carbono/química , Catálise , Reagentes para Ligações Cruzadas/química , Hidrogenação , Nanopartículas Metálicas/química , Porosidade , Dióxido de Silício , Temperatura
16.
Top Curr Chem (Cham) ; 378(1): 11, 2020 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-31903506

RESUMO

The dramatic increase in atmospheric carbon dioxide (CO2) concentrations has attracted human attention and many strategies about converting CO2 into high-value chemicals have been put forward. Metal-organic frameworks (MOFs), as a class of versatile materials, have been widely used in CO2 capture and chemical conversion, due to their unique porosity, multiple active centers and good stability and recyclability. Herein, we focused on the processes of chemical conversion of CO2 by MOFs-based catalysts, including the coupling reactions of epoxides, aziridines or alkyne molecules, CO2 hydrogenation, and other CO2 conversion reactions. The synthesized methods and high catalytic activity of MOFs-based materials were also analyzed systematically. Finally, a brief perspective on feasible strategies is presented to improve the catalytic activity of novel MOFs-based materials and explore the new CO2 conversion reactions.


Assuntos
Dióxido de Carbono/química , Estruturas Metalorgânicas/química , Alcenos/química , Aminas/química , Aziridinas/química , Catálise , Compostos de Epóxi/química , Hidrogenação , Líquidos Iônicos/química
17.
Molecules ; 25(2)2020 Jan 12.
Artigo em Inglês | MEDLINE | ID: mdl-31940875

RESUMO

The xylitol ester of hydrogenated rosin (XEHR) was obtained for the first time from biomass-based hydrogenated rosin and xylitol using an environmentally friendly, high-pressure CO2 catalytic synthesis. This compound is intended for use as an emulsifier for food. Analyses by ICP-AES showed the absence of heavy metal residues in the product, such that it met food standards. Fourier transform infrared and nuclear magnetic resonance spectroscopies together with gel permeation chromatography confirmed the successful esterification and the formation of a monoester and diester with molar masses of 427 and 772 g/mol. The emulsification of water/soybean oil mixtures by adding the XEHR was assessed at pH values of 4, 6.86, and 10 and in the presence of NaCl, KCl, MgCl2, and CaCl2. The XEHR was found to act as an emulsifier by reducing the interfacial tension of such mixtures to less than 2 mN/m under all conditions. The highest emulsifying activity index (9.52 m2/g) and emulsifying stability index (94.53%) were obtained after adding MgCl2 (100 mM). Particle size and confocal microscopy showed that the presence of salts gave a more uniform droplet size and a finer emulsion structure. The high viscosities of the emulsions containing salts also suggested a more cohesive oil droplet network.


Assuntos
Emulsificantes/síntese química , Ésteres/química , Aditivos Alimentares/síntese química , Resinas Vegetais/química , Xilitol/química , Biomassa , Dióxido de Carbono/química , Emulsificantes/análise , Ésteres/análise , Aditivos Alimentares/análise , Humanos , Concentração de Íons de Hidrogênio , Hidrogenação , Cloreto de Magnésio/química , Tamanho da Partícula , Pressão , Óleo de Soja/química , Tensão Superficial , Água/química , Xilitol/análise
18.
Bioresour Technol ; 297: 122492, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31796376

RESUMO

In this study, the Mo-promoted Ir/SiO2 (Ir-MoOx/SiO2) catalysts combined with the zeolite HZSM-5 were used for the direct conversion of microcrystalline cellulose (MCC) to liquid fuel (C5/C6 alkanes) in n-dodecane/H2O system. A synergistic effect was formed between the partially reduced MoOx species and the Ir particles, which effectively promoted the catalytic activity of Ir/SiO2 catalyst. When the Mo/Ir molar ratio was 0.5, a high yield of C5/C6 alkanes (91.7%) was achieved at 210 â„ƒ for 12 h. In addition, the main component of C5/C6 alkanes was n-hexane, which was proven to be obtained by the hydrogenolysis of the key intermediate, sorbitol, formed from the hydrolysis and hydrogenation of MCC.


Assuntos
Alcanos , Dióxido de Silício , Catálise , Celulose , Hidrogenação
19.
Biosci Biotechnol Biochem ; 84(1): 37-42, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31578944

RESUMO

The monoterpene, trans-p-menth-3-ene-1,2,8-triol, is a naturally occurring alcohol isolated from several herbal plants. In the present work, the asymmetric synthesis of both enantiomers of this natural product was achieved using Sharpless asymmetric dihydroxylation as the key step. A reversal of enantiofacial selectivity was observed in the asymmetric dihydroxylation.


Assuntos
Monoterpenos Cicloexânicos/química , Monoterpenos Cicloexânicos/síntese química , Extratos Vegetais/química , Extratos Vegetais/síntese química , Cromatografia em Gel , Cristalização , Monoterpenos Cicloexânicos/isolamento & purificação , Cromatografia Gasosa-Espectrometria de Massas , Hidrogenação , Hidroxilação , Isomerismo , Conformação Molecular , Extratos Vegetais/isolamento & purificação , Sílica Gel
20.
Talanta ; 208: 120409, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31816787

RESUMO

A new and simple method for Ni determination in hydrogenated vegetable fat (HVF) has been developed using a RP-DLLME sample preparation procedure for further determination by flame atomic absorption spectrometry (FAAS) and graphite furnace atomic absorption spectrophotometry (GFAAS). The RP-DLLME procedure includes simultaneous microextraction and preconcentration of Ni in HVF, using 5.0 g of HVF preheated (75 °C) and diluted in 5.0 mL of xylene, with the addition of a dispersant/extractant mixture (n-propanol/dilute HNO3). The sample was manually stirred and centrifuged and the aqueous phase was collected for further Ni determination by FAAS and GFAAS. RP-DLLME was carried out using only 700 µL of n-propanol and 300 µL of 2.0 mol L-1 HNO3. The recovery varied from 93.3% to 101.5% for HVF. The LODs and LOQs were 40 and 90 ng g-1 for FAAS, and 0.41 and 1.36 ng g-1 for GFAAS. The proposed analytical method is viable and this is the first application of RP-DLLME to solid fat samples, with Ni determination as an example of application. This method consumes small amounts of reagents, with lower toxicity as compared to microwave decomposition. Furthermore, the key features of the RP-DLLME method include simplicity of operation, high sample mass, reduced reagent consumption, and use of diluted HNO3 as an extractant.


Assuntos
Gorduras na Dieta/análise , Contaminação de Alimentos/análise , Microextração em Fase Líquida/métodos , Níquel/análise , Óleo de Soja/química , Antioxidantes/química , Hidroxitolueno Butilado/química , Ácido Cítrico/química , Hidrogenação , Espectrofotometria Atômica/métodos
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