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1.
Carbohydr Polym ; 227: 115380, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31590848

RESUMO

Old corrugated containers with low recyclability were used as raw materials to synthesize a series of aerogels with varying cellulose concentrations in NaOH/urea solution via a freeze-drying process. The resulting aerogels had a rich porous structure with specific surface areas in the range of 132.72-245.19 m2.g-1 and mesopore volumes in the range of 0.73-1.53 cm3.g-1, and were tested for CO2 sorption at ambient temperature and pressure, displaying excellent CO2 adsorption capacities in the range of 1.96-11.78 mmol.g-1. Furthermore, the CO2/N2 selectivity of aerogels decreased with decreasing specific surface area, which was mainly caused by the decrease in CO2 capture. In addition, the CO2 sorption capacity of the sample with 2% cellulose content, CA-2, exceeded the values reported so far for many other sorbents with higher specific surface areas, and showed reasonable cyclic stability for CO2 capture. Therefore, this adsorbent represents an attractive prospect for CO2 uptake at room temperature.


Assuntos
Dióxido de Carbono/química , Sequestro de Carbono , Celulose/química , Adsorção , Géis , Papel , Porosidade , Reciclagem , Hidróxido de Sódio/química , Ureia/química
2.
Bioresour Technol ; 291: 121844, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31400704

RESUMO

A low-temperature sodium hydroxide (NaOH) pretreatment for sugarcane bagasse (SCB) was obtained via the surface response design in this study. However, a large quantity of water consumption and wastewater generation which have been the common problems for alkaline pretreatment of lignocellulose still exists in this pretreatment. In order to reduce water consumption and wastewater generation, this study attempted to perform enzymatic hydrolysis and fermentation of NaOH-treated SCB without washing process. It showed that after pretreatment and solid-liquid separation, NaOH-treated SCB could be directly hydrolysed by cellulase via pH and solid-liquid adjustment without washing steps, and the maximum enzymatic hydrolysis efficiency could reach to 70.2%. A domesticated Saccharomyces cerevisiae Y2034 which can endure 6-times diluted BL was obtained, and realized 67.5% ethanol yield from the enzymatic hydrolysate of unwashed NaOH-treated SCB. It provided a clue for converting NaOH-treated lignocellulose to ethanol at low water consumption and wastewater generation.


Assuntos
Celulose/química , Etanol/química , Saccharum/química , Hidróxido de Sódio/química , Celulose/metabolismo , Temperatura Baixa , Etanol/metabolismo , Fermentação , Hidrólise , Lignina/química , Lignina/metabolismo , Saccharomyces cerevisiae/metabolismo , Saccharum/metabolismo , Águas Residuárias/química
3.
Chem Biol Interact ; 311: 108788, 2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31401088

RESUMO

Aqueous solutions of chlorpyrifos oxon are used to study the ability of chlorpyrifos oxon to catalyze protein crosslinking. Assays for protein crosslinking can avoid artifacts by using information on the stability of chlorpyrifos oxon in solution. We undertook to determine the half-life of chlorpyrifos oxon in aqueous solution because literature values do not exist. The rate of conversion of chlorpyrifos oxon to 3,5,6-trichloro-2-pyridinol was measured at 23 °C in 20 mM TrisCl pH 8 and pH 9 by recording loss of absorbance at 290 nm for chlorpyrifos oxon and increase in absorbance at 320 nm for 3,5,6-trichloro-2-pyridinol. The half-life of chlorpyrifos oxon was 20.9 days at pH 8 and 6.7 days at pH 9. Literature reports for the stability of other organophosphorus toxicants were summarized because our current studies suggest that other organophosphorus toxicants are also crosslinking agents.


Assuntos
Clorpirifos/análogos & derivados , Ésteres/química , Organofosfatos/química , Água/química , Butirilcolinesterase/química , Butirilcolinesterase/metabolismo , Clorpirifos/química , Clorpirifos/metabolismo , Meia-Vida , Humanos , Concentração de Íons de Hidrogênio , Hidrólise , Organofosfatos/metabolismo , Hidróxido de Sódio/química , Espectrofotometria
4.
Chem Biodivers ; 16(9): e1900275, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31407869

RESUMO

The açaí fruit depulping produces large amounts of long lignocellulosic fiber bundles that are disposed in the environment. Chemical pretreatments may improve açaí fibers favoring their usage in advanced materials. This work aimed to define optimal alkali reaction parameters to improve the properties of açaí fibers. Two NaOH concentrations (5 % and 10 %) and two reaction temperatures (80 °C and 100 °C) were tested. The raw and treated fibers were analyzed by scanning electron microscopy, Fourier transformed infrared spectroscopy, X-ray diffraction, and thermal analyses. All the alkali pretreatments separated fibers from the bundles, unblocked pit channels by removing silicon structures, exposed the inner lignin, partially removed non-cellulosic compounds, and raised the cellulose crystalline index. The highest temperature and NaOH content resulted in better cleaning and isolation of the fibers, while milder conditions better preserved the cellulose crystalline structure and thermal stability.


Assuntos
Lignina/química , Hidróxido de Sódio/química , Lignina/isolamento & purificação , Tamanho da Partícula , Propriedades de Superfície , Temperatura Ambiente
5.
Chemistry ; 25(61): 13885-13889, 2019 Nov 04.
Artigo em Inglês | MEDLINE | ID: mdl-31469925

RESUMO

Precipitation reactions under flow in confined media are relevant to the control of pathological biomineralization, processes affecting aquifers, and challenges in the petroleum industry. Here we show that for a simple geometry, such conditions create macroscopic structures including helices, tubes, lamellae, slugs, and disordered patterns. All structures emerge when salt solution is slowly injected into thin capillaries filled with hydroxide solution. For the helices, the pitch is proportional to the pump rate revealing a constant period of 0.63 s. Different morphologies of the insoluble metal hydroxide can co-exist causing random transitions along the capillary. On average, 15 % of the final system contains residual hydroxide solution. While mechanically stable for flow speeds above 25 mm min-1 , structures collapse and sediment for slower injection speeds. Some of the observed features share similarities with precipitate tubes in chemical gardens and the dynamics of liquid-liquid pipe flow.


Assuntos
Precipitação Química , Hidróxido de Sódio/química , Soluções/química , Sulfato de Zinco/química
6.
Mar Drugs ; 17(8)2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31374944

RESUMO

Microalgae are considered as excellent candidates for bioactive compounds, yet microalgal residues remaining after the extraction of one or two compounds are usually discarded, which is not economical. This study demonstrates the alkaline extraction of proteins from Chlorella pyrenoidosa residue after lipid and pigment extractions, and their functional properties. Single-factor experiments and response surface methodology were used to obtain the optimal conditions for protein extraction. Based on our results, a maximum protein yield of 722.70 mg/g, was obtained under the following extraction conditions: sodium hydroxide concentration 7.90%, extraction temperature 70.00 °C, extraction time 34.80 min, and microalgal residue concentration 8.20 mg/mL. The molecular weight of microalgal residue protein isolate (MRPI) was mainly distributed at the regions of 0.18-0.50 kDa, 0.50-1.50 kDa, and 1.50-5.00 kDa. The essential amino acid content was greater than the values recommended by FAO/WHO standards; a high essential amino acid index value (1.49) was another good indication that MRPI is suitable for human consumption. Moreover, MRPI exhibited excellent emulsifying properties and antioxidant activity, which suggests it may be useful as an emulsifying agent and antioxidant. These findings could improve the extraction methods of functional protein from microalgal residue and add value to microalgae-based bioactive compound production processes.


Assuntos
Chlorella/química , Microalgas/química , Extratos Vegetais/farmacologia , Proteínas de Plantas/farmacologia , Sequência de Aminoácidos , Aminoácidos Essenciais/química , Antioxidantes/química , Antioxidantes/isolamento & purificação , Antioxidantes/farmacologia , Emulsificantes/química , Emulsificantes/isolamento & purificação , Emulsificantes/farmacologia , Alimento Funcional , Lipídeos/isolamento & purificação , Peso Molecular , Estresse Oxidativo/efeitos dos fármacos , Pigmentos Biológicos/isolamento & purificação , Extratos Vegetais/química , Extratos Vegetais/isolamento & purificação , Proteínas de Plantas/química , Proteínas de Plantas/isolamento & purificação , Hidróxido de Sódio/química , Temperatura Ambiente
7.
Food Chem ; 300: 125200, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31325748

RESUMO

Ethyl carbamate (EC) and N-nitrosoamines (NAs) are toxic contaminants which can be typically formed in fermented alcoholic beverages. In the present work, a novel approach for simultaneous analysis of EC and NAs in beer and yellow rice wine based on ice-bath assisted sodiumhydroxide purification and GC-MS/MS was firstly established. Samples were extracted with acetonitrile-ethyl acetate after addition of internal standards. The extraction solution system was purified by sodiumhydroxide solid under ice-bath. After concentration, target analytes were separated on a HP-INNOWAX quartz capillary column and determined under dynamic multiple reactions monitoring mode of MS/MS. The limits of detection and quantification (LOD and LOQ), matrix effect, recovery and precision of the method were evaluated. Results were linear in the concentration range 2-200 µg/L for all analytes of interest, with regression coefficients higher than 0.999. LODs and LOQs were in the ranges of 0.1-0.5 µg/kg and 0.5-1.5 µg/kg, respectively. The mean recoveries at three spiked levels were between 81.5% and 121.0%. The intra- and inter-day precisions were in the ranges of 2.2-9.4% and 1.6-7.9%, respectively. The validated method was successfully applied to determine thirteen targets in commercial beer and yellow rice wine. EC was detected in all beers and yellow rice wines with the concentrations ranging from 1.18 to 22.90 µg/L. Results indicated wide EC contamination and confirmed its urgency for monitoring EC in fermented alcoholic beverages.


Assuntos
Cerveja/análise , Contaminação de Alimentos/análise , Nitrosaminas/análise , Uretana/análise , Vinho/análise , Acetonitrilos/química , Fracionamento Químico/métodos , Cromatografia Gasosa-Espectrometria de Massas/métodos , Gelo , Limite de Detecção , Oryza , Reprodutibilidade dos Testes , Hidróxido de Sódio/química , Espectrometria de Massas em Tandem/métodos
8.
Int J Biol Macromol ; 138: 106-115, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31295496

RESUMO

Cytochrome c is a metalloprotein with primary physiological functions in the respiratory chain and in the regulation of cell death signals. Investigating the mechanisms leading to cytochrome c fibril formation is of primary importance for understanding its misfunctioning and, in a wider perspective, for its technologic applications in the field of bio-nanoscience. In this work, we analyzed the morphology and the spectroscopic properties of cytochrome c aggregates, combining the outcomes from electron microscopy, fluorescence, infrared and Raman spectroscopies and making use of statistical tools for the data analysis. The morphology scenario is quite complex, as it points out the presence of aggregates in the shape of platelets as well as fibers at micrometric scale. By infrared and Raman spectroscopy we analyzed the secondary and tertiary structures of unordered aggregates and fibrils, drawing a pathway for their formation at the timescales from tents to hundreds of minutes. Dependence of the fibrillation route on environmental pH, above and below the isoelectric point, and on protein concentration has also been explored. We found that it is possible to direct the process towards the formation of superstructures with different morphologies and different sizes along with fibrils, after destabilization of the native fold and the formation of ß-sheet rich structures. A different mechanism characterizes aggregate/fibril elongation of cyt c in Tris-HCl, in comparison with NaOH environment.


Assuntos
Citocromos c/química , Agregados Proteicos , Animais , Tampões (Química) , Ácido Clorídrico/química , Concentração de Íons de Hidrogênio , Cinética , Conformação Proteica em Folha beta , Estrutura Secundária de Proteína , Hidróxido de Sódio/química , Análise Espectral , Temperatura Ambiente
9.
Acta Sci Pol Technol Aliment ; 18(2): 173-184, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31256545

RESUMO

BACKGROUND: Performing iron fortification by adding the iron compound directly into foods helps to tackle the problem of iron deficiency. However, the fortification brings about some problems as well, including undesirable organoleptic effects, oxidation, and reduced bioavailability. Ensuring appropriate encapsulation can overcome these problems. Hence, it is crucial to identify a proper excipient for protecting the iron. Glucomannan has the potential to be a suitable iron encapsulation excipient. The present work therefore sought to prepare an iron excipient from modified glucomannan using the gelation method. Glucomannan modification was conducted by either chemical reaction or in combination with another compound. METHODS: Glucomannan was isolated from Amorphophallus oncophyllus flour. To maximize encapsulation performance, glucomannan was modified by either deacetylation using NaOH (0.4 M) or in combination with alginate. After dissolving the excipient (1%), this solution was mixed with FeSO4 to obtain 25 mg of iron per 1 g of excipient. The mixture was dropped into either an ethanol or CaCl2 solution for gelation. The beads of seven variations of the resultant glucomannan-based excipient were investigated for their encapsulation efficiency, bead size, and swelling. The release of iron in the two pH solutions together with their respective release models were also evaluated. RESULTS: It was revealed that the highest iron efficiency (64%) was achieved using deacetylated glucoman- nan, which was gelled in CaCl2. However, this matrix also resulted in the highest release rate in both pH solutions. The release rate of iron was lower in the low pH solution (pH: 1.2) than in the higher pH solution (pH: 6.8) for all matrix combinations. The Korsmeyer model was the most fitting model for describing the release profile of iron in both pH solutions (R2 ≥ 0.958) for all excipient variations. CONCLUSIONS: This study suggested the potency of modified glucomannan to be pH-sensitive for iron encapsulation.


Assuntos
Amorphophallus/química , Excipientes , Ferro/administração & dosagem , Mananas/química , Alginatos/química , Cloreto de Cálcio/química , Cápsulas , Géis , Humanos , Concentração de Íons de Hidrogênio , Hidróxido de Sódio/química
10.
Food Chem ; 297: 124945, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31253310

RESUMO

Almond shell, a by-product obtained from the nut industry, was valorised into low degree of polymerisation xylooligosaccharides using alkaline pretreatment and enzymatic hydrolysis. The effect of particle size on hemicellulose recovery upon pretreatment was studied using 1 and 2 M NaOH. It was observed that particle size significantly influences hemicellulose recovery, as particles below 120 µm resulted in near complete recovery at 2 M NaOH. Enzymatic hydrolysis of hemicellulose was optimised using response surface methodology, to obtain efficient xylooligosaccharides production at low enzyme dose and high substrate concentration. For higher XOS yield, an enzyme dose of 10 U and substrate concentration <2% was optimal. The in-vitro human faecal fermentation study revealed no significant difference in gas and short chain fatty acid level among substrates evaluated. It was observed that short chain oligosaccharides produce higher level of acetate than medium chain oligosaccharides.


Assuntos
Fezes/microbiologia , Pentoses/química , Polissacarídeos/metabolismo , Técnicas de Cultura Celular por Lotes , Biomassa , Cromatografia Líquida de Alta Pressão , Endo-1,4-beta-Xilanases/metabolismo , Ácidos Graxos Voláteis/análise , Ácidos Graxos Voláteis/metabolismo , Fezes/química , Gases/química , Glucuronatos/análise , Glucuronatos/metabolismo , Humanos , Hidrólise , Oligossacarídeos/análise , Oligossacarídeos/metabolismo , Tamanho da Partícula , Polissacarídeos/química , Hidróxido de Sódio/química
11.
Food Chem ; 297: 124939, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31253337

RESUMO

Effects of the brine solution with different NaOH concentrations on the physicochemical properties, intermolecular forces, and gel properties of duck egg whites were studied. The free alkalinity, salt content and surface hydrophobicity of egg whites increased as the pickling time and NaOH concentration increased. The primary intermolecular forces (disulfide bonds and hydrophobic interactions) in the alkali egg white gels were increased firstly and then decreased, resulting from the fact that the proteins were degraded under strong alkali conditions during the late stage of the pickling process. Changes of hardness and springiness of egg white gels were closely related with the interactions of the protein molecules. Thereinto, the change tendency of springiness was in accordance with the changes of hydrogen bond of egg white gels. The colour of the egg white gels obtained from alkali treatment changed from white to amber during pickling.


Assuntos
Clara de Ovo/química , Géis/química , Cloreto de Sódio/química , Hidróxido de Sódio/química , Animais , Patos , Eletroforese em Gel de Poliacrilamida , Ligações de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Temperatura Ambiente
13.
Chem Pharm Bull (Tokyo) ; 67(5): 461-466, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31061371

RESUMO

Crystallization by pH adjustment, as a type of reaction crystallization, is a solid-liquid separation method widely used in the area of pharmaceutical and pharmaceutical intermediate manufacturing. On the other hand, 3-alkenyl cephem compound is a typical zwitterionic pharmaceutical intermediate that possesses both an amino group and a carboxylic acid group. Such structure affords three main pH regions in solution and results in difficulties using crystallization by pH adjustment for isolation. As a consequence, 3-alkenyl cephem compound is usually crystallized at the point away from the solubility curve, causing unrestricted nucleation and flocculation behavior for the deposited particles which is difficult to filtrate. In this study, the pKa of 3-alkenyl cephem compound was intensively investigated to inhibit the nucleation. An optimal pH level point was also sought to make monodisperse particles. In particular, during crystallization by pH-modulation operation, the key point was identified to be the number of primary particles aggregated in the secondary particles. It was revealed that the increment number of primary particles led to the generation of larger monodisperse particles. This investigation, combined with solid-liquid equilibrium, enabled the acquisition of target species with good operability for filtration process. This present investigation becomes the prosperity in the zwitterion compound production that it has hardships to crystallize and filtrate.


Assuntos
Antibacterianos/química , Compostos Azo/química , Cefalosporinas/química , Cristalização/métodos , Concentração de Íons de Hidrogênio , Hidróxido de Sódio/química , Solubilidade
14.
Anal Chim Acta ; 1069: 66-72, 2019 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-31084742

RESUMO

A simple paper-based analytical device (PAD) has been developed to rapidly detect formaldehyde (FA) in food samples. The analysis was based on sulfite assay where FA reacted with excess sulfite to generate sodium hydroxide (NaOH) that was quantified on PAD using acid-base titration. The PAD consisted of a central sample zone connected to ten reaction and detection zones. All detection zones were pre-deposited with polyethylene glycol (PEG) with phenolphthalein (Phph) as an indicator. Reaction zones contained different amounts of the titrant, potassium hydrogen phthalate (KHP). On flowing into reaction zones, the NaOH product reacts with KHP to reach the end point. In the presence of excess NaOH, unneutralized NaOH reached the detection zone and caused Phph color change from colorless to pink. In contrast, when NaOH was less than KHP, the detection zone remained colorless. Concentration of FA can be quantified from the number of pink detection zone(s) which were correlated with a known amount of pre-deposited KHP on the PAD. Total analytical process could be completed within 5 min. Areas of each zone and amounts of reagents added to the corresponding zones of the PAD were optimized to obtain reproducible and accurate results. PAD gave ranges of FA detection of 100-1000 mg L-1 with an interval of 100 mg L-1 and the limit of detection (LOD) was 100 mg L-1. PADs were stable for up to a month under dark and cold conditions. Analysis of FA in food samples using PAD agreed well with those from the classical sulfite assay.


Assuntos
Contaminação de Alimentos/análise , Formaldeído/análise , Papel , Concentração de Íons de Hidrogênio , Hidróxido de Sódio/química , Sulfitos/química
15.
Environ Sci Pollut Res Int ; 26(19): 19434-19444, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31077050

RESUMO

The feasibility of anaerobic digestion on the release of biogas and heavy metals from contaminated rice straw pretreated with NaOH solution was studied. The results show that NaOH pretreatment can significantly boost the release of biogas and heavy metals from rice straw using anaerobic digestion. Under the optimal conditions for biomass pretreated 6% (w/w) NaOH with a solid-to-solution ratio of 1:20, total biogas and methane yields of 446.3 mL/g and 263.5 mL/g volatile solids were achieved, which were 22.18% and 41.59% higher than those of the control without NaOH pretreatment, respectively, and the release percentages of Cd, Pb, Cu, and Zn from rice straw reached 86.95-97.69%. The release of heavy metals from rice straw can contribute to both the degradation of lignin by NaOH pretreatment and the utilization/transformation of lignocellulose via anaerobic digestion. The acidification levels and total volatile fatty acid contents significantly influence on the release of heavy metals. Based on the Illumina HiSeq sequencing analysis, the dominant phyla in the biogas residues were proteolytic (Bacteroidetes) and hydrogen-producing (Firmicutes) bacteria, while the growth of Methanospirillum and Methanosaeta in anaerobically digested effluent was promoted. The results revealed that anaerobic digestion combined with NaOH pretreatment is suitable for the disposal of heavy metal-contaminated biomass.


Assuntos
Biocombustíveis/análise , Metais Pesados/análise , Metano/análise , Oryza/química , Eliminação de Resíduos/métodos , Hidróxido de Sódio/química , Anaerobiose , Bacteroidetes/crescimento & desenvolvimento , Biomassa , Ácidos Graxos Voláteis/análise , Estudos de Viabilidade , Firmicutes/crescimento & desenvolvimento , Lignina/química , Caules de Planta/química
16.
Carbohydr Polym ; 217: 178-189, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31079675

RESUMO

Natural fibers are emerging as best alternatives for synthetic materials in selective applications. These fibers may not have the required properties in its raw form and hence needs some alterations in its characteristics. Likely, this article reports enhancement in surface and structural properties of Thespesia populnea bark fiber treated with NaOH under various concentration and soaking period. Fibers treated with 5% NaOH for 60 min yields noteworthy mechanical strength (678.41 ± 48.91 MPa) owing to its relatively high cellulose fraction (76.42%). Fourier transform infrared spectra endorses the removal of non-cellulosic compounds and X-ray diffraction studies reveals 13.6% growth in the size of cellulose crystals on optimally treated fibers. Weibull distribution model statistically interprets the reliability of acquired tensile test results. Finally, microscopic examinations with scanning electron microscopy and atomic force microscopy explore that fiber surface turns rough after alkali treatment and makes it appropriate for reinforcement in polymer matrices.


Assuntos
Celulose/química , Malvaceae/química , Casca de Planta/química , Hidróxido de Sódio/química , Celulose/isolamento & purificação , Módulo de Elasticidade , Hidrólise , Propriedades de Superfície , Temperatura Ambiente , Resistência à Tração
17.
Appl Biochem Biotechnol ; 189(3): 774-786, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31119528

RESUMO

In this research, a core-shell immobilized lipase was constructed with the cost-effective bamboo carrier. Natural bamboo powder was pretreated by different methods. The results of SEM and BET demonstrated that alkali pretreatment increased the surface roughness with formed wrinkles and micropores, facilitating the lipase adsorption on the pretreated carrier. The optimal immobilization conditions were obtained through the response surface method, and the optimized conditions were 2 wt% sodium hydroxide solution, 1.2 wt% sodium alginate, and 0.69 wt% calcium chloride at a calcification time of 100 min. Under this condition, the immobilized lipase showed an excellent protein adsorption rate and thermal stability. When the core-shell structured immobilized lipase was used in wax ester synthesis system, the esterification yield (80%) did not show an obvious decline after 17 batches. The results indicated that the core-shell immobilized lipase is effective for the biocatalytic reaction, and the immobilization method is a promising strategy for future enzyme immobilization and modification in industrial applications.


Assuntos
Enzimas Imobilizadas/química , Enzimas Imobilizadas/metabolismo , Lipase/química , Lipase/metabolismo , Temperatura Ambiente , Adsorção , Alginatos/química , Biocatálise , Candida/enzimologia , Estabilidade Enzimática , Esterificação , Ésteres/química , Concentração de Íons de Hidrogênio , Poaceae/química , Hidróxido de Sódio/química
18.
Orig Life Evol Biosph ; 49(1-2): 1-18, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31004318

RESUMO

Syntheses under shock in nitrogen bubbled samples of the water - formamide - bicarbonate - sodium hydroxide system at pH 8.63, 9.46 and 10.44 were performed in the stainless steel preservation capsules. The maximum temperature and pressure in the capsules reached 545 K and 12.5 GPa respectively. Using the LC-MS-MS analysis, the 21 synthesis products have been identified, including amines and polyamines, carboxamide, acetamide and urea derivatives, compounds containing aniline, pyrrolidine, pyrrole, imidazole, as well as alcohol groups. It was found that the Fischer-Tropsch-type syntheses with catalysis on the surface of the stainless steel of the conservation capsule associated with the adsorbed hydrogen cyanide reactions and transamidation processes play the main role in the shock syntheses. Formation reactions of all the above-mentioned compounds have been suggested. It was proposed that hydrogen cyanide, ammonia, isocyanic acid, aminonitrile, aminoacetonitrile, as well as adsorbed species H(a), CH(a), CH2(a), CHOH(a), NH2(a) and H2CNH(a) are especially important for the formation of the products. A reduction reaction of adsorbed bicarbonate with hydrogen to formaldehyde has been first postulated. In the studied system also classical reactions take place - Wöhler's synthesis of urea and Butlerov's synthesis of methenamine. It was suggest that material of meteorites may be an effective catalyst in the Fischer-Tropsch-type syntheses at falling of the iron-nickel meteorites in the water - formamide regions on the early Earth. It was concluded that life could have originated due to the impact of meteorites on alkaline water-formamide lakes located near volcanoes on the early Earth.


Assuntos
Bicarbonatos/química , Evolução Química , Formamidas/química , Origem da Vida , Compostos de Potássio/química , Hidróxido de Sódio/química , Cromatografia Líquida , Concentração de Íons de Hidrogênio , Meteoroides , Espectrometria de Massas em Tandem , Água/química
19.
Sci Total Environ ; 675: 203-212, 2019 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-31030128

RESUMO

In order to realize the efficient utilization of biorefinery corncob lignin, the promising catalytic oxidation strategy was carried out by using ZrCl4 and NaOH as the co-catalyst and dioxygen as the oxidant in MeCN/H2O. GC/MS, GC-FID, and MALDI-TOF/MS were employed to recognize the produced monomers and oligomers, and GPC was used to monitor the molecular weight changes of lignin fragments. In addition, specific structural evolution of corncob lignin during ZrCl4/NaOH-catalyzed oxidation were revealed by quantitative 13C (Q13C) and 2D HSQC NMR techniques. Results showed that the total yields of produced oxidation monomers reached 6.8 wt%, and aromatic aldehydes were the major species, in which vanillin and 4-hydroxybenzaldehyde were the two dominant products. After ZrCl4/NaOH-catalyzed oxidation, the weight-average molecular weight of corncob lignin and its products decreased from 2000 Da to 300 Da after oxidation with 16 h. Moreover, Q13C NMR analysis showed the decrease percentage of CO aliphatic carbons (including methoxyl carbons), the increase percentage of CC aliphatic and carbonyl carbons, and the relative stable percentage of aromatic carbons with reaction prolonged. These results combined with the further confirmation from HSQC indicated the oxidative cleavage of CO aliphatic linkages and removal of methoxy groups within corncob lignin, as well as the formation of CC aliphatic bonds and carbonyl groups. The work presented a comprehensive insight into the catalytic oxidative depolymerization of biorefinery corncob lignin.


Assuntos
Acetonitrilos/química , Lignina/química , Hidróxido de Sódio/química , Zircônio/química , Catálise , Modelos Químicos , Oxirredução
20.
PLoS One ; 14(4): e0216117, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31026266

RESUMO

Using a mixture of neutral primary amine dehydroabietylamine (DHAA) and long-chain cetyltrimethyl ammonium bromide (CTAB) as the template, ordered lamellar supermicroporous silicas were synthesized with NaOH as the base source and tetraethylorthosilicate (TEOS) as the silica source. The concentrations of DHAA, CTAB, and NaOH in the synthesis system had great effects on the structural properties of the samples. When the molar ratio of components was nTEOS:nCTAB:nDHAA:nNaOH:nH2O = 1:0.114:0.00457:0.5:60, the material showed a lamellar phase with the highest ordering degree. By adding only a trace amount of DHAA into the synthesis system, the structure of the samples could be transformed from cubic phase to lamellar phase, since the added DHAA solubilized in CTAB micelles to change the effective surfactant ion pair packing parameter. The dosage of CTAB should be moderate; too high or too low will decay the ordering degree of the lamellar structure.A much higher concentration of NaOH resulted in an ethanol-rich solvent in which the DHAA did not solubilize in the micelles of CTAB, but adsorbed at the hydrophilic headgroup-solvent interface. Accordingly, a structural transformation from lamellar phase to hexagonal phase occurred.


Assuntos
Dióxido de Silício/química , Dióxido de Silício/síntese química , /química , Cátions , Cetrimônio/química , Nitrogênio/química , Porosidade , Hidróxido de Sódio/química , Temperatura Ambiente , Difração de Raios X
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