scholarly journals Stability of gamma-valerolactone under pulping conditions as a basis for process optimization and chemical recovery

Cellulose ◽  
2021 ◽  
Author(s):  
Marianna Granatier ◽  
Inge Schlapp-Hackl ◽  
Huy Quang Lê ◽  
Kaarlo Nieminen ◽  
Leena Pitkänen ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
Treatment Time ◽  
Reaction Times ◽  
Chemical Recovery ◽  
Wide Ph Range ◽  
Alkaline Conditions ◽  
Naoh Solution ◽  
Hydroxyvaleric Acid ◽  
Ph Range ◽  
Spent Liquor

AbstractThis study focuses on the investigation of the extent of the γ-valerolactone (GVL) hydrolysis forming an equilibrium with 4-hydroxyvaleric acid (4-HVA) in aqueous solutions over a wide pH range. The hydrolysis of a 50 wt% GVL solution to 4-HVA (3.5 mol%) was observed only at elevated temperatures. The addition of sulfuric acid (0.2 × 10–5 wt% to 6 wt%) at elevated temperatures (150–180 °C) and reaction times between 30 and 180 min caused the formation of 4 mol% 4-HVA. However, with decreasing acidity, the 4-HVA remained constant at about 3 mol%. The hydrolysis reactions in alkaline conditions were conducted at a constant time (30 min) and temperature (180 °C) with the variation of the NaOH concentration (0.2 × 10–6 wt% to 7 wt%). The addition of less than 0.2 wt% of NaOH resulted in the formation of less than 4 mol% of sodium 4-hydroxyvalerate. A maximum amount of 21 mol% of 4-HVA was observed in a 7 wt% NaOH solution. The degree of decomposition after treatment was determined by NMR analysis. To verify the GVL stability under practical conditions, Betula pendula sawdust was fractionated in 50 wt% GVL with and without the addition of H2SO4 or NaOH at 180 °C and a treatment time of 120 min. The spent liquor was analyzed and a 4-HVA content of 5.6 mol% in a high acidic (20 kg H2SO4/t wood) and 6.0 mol% in an alkaline (192 kg NaOH/t wood) environment have been determined.

scholarly journals Stability of Gamma-valerolactone Under Pulping Conditions as a Basis for Process Optimization and Chemical Recovery

2021 ◽  
Author(s):  
Marianna Granatier ◽  
Inge Schlapp-Hackl ◽  
Huy Quang Lê ◽  
Kaarlo Nieminen ◽  
Herbert Sixta
Keyword(s):  
Elevated Temperatures ◽  
Reaction Times ◽  
Chemical Recovery ◽  
Wide Ph Range ◽  
Alkaline Conditions ◽  
Naoh Solution ◽  
Hydroxyvaleric Acid ◽  
The Stability ◽  
Ph Range ◽  
Spent Liquor

Abstract This study investigates the extent of the g-valerolactone (GVL) hydrolysis forming an equilibrium with 4-hydroxyvaleric acid (4-HVA) in aqueous solutions over a wide pH range. The hydrolysis of pure 50 wt% GVL to 4-HVA (3.5 mol%) was observed only at elevated temperatures. The addition of sulfuric acid (0.2×10-5 wt% to 6 wt%) at elevated temperatures (150 – 180°C) and reaction times between 30-180 min caused the formation of 4 mol% 4-HVA but with decreasing acidity, the 4-HVA remained constant at about 3 mol%. The hydrolysis reactions in alkaline conditions were conducted at constant time (30 min) and temperature (180 °C) with variation of the NaOH concentration (0.2×10-6 wt% to 7 wt%). The addition of less than 0.2 wt % of NaOH resulted in the formation of less than 4 mol% of sodium 4-hydroxyvalerate. A maximum amount of 21 mol% of 4-HVA was observed in a 7 wt% NaOH solution. The stability after synthesis was determined by NMR analysis. To verify the GVL stability results obtained under practical conditions, Betula pendula sawdust was fractionated in 50% GVL with and without addition of H2SO4 or NaOH at 180°C and 120 min, and spent liquor was analyzed. The spent liquor contained 5.6 mol% and 6.0 mol% of 4-HVA in a highly acidic (20 kg H2SO4/t wood) and alkaline (192 kg NaOH/ t wood) environment, respectively.

2´-carboxy-3-keto-D-arabinitol 1,5-bisphosphate, the six-carbon intermediate of the ribulose bisphosphate carboxylase reaction

1986 ◽  
Vol 313 (1162) ◽  
pp. 397-407 ◽  
Keyword(s):  
Metal Ion ◽  
Ribulose Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate ◽  
Bisphosphate Carboxylase ◽  
Wide Ph Range ◽  
Alkaline Conditions ◽  
Divalent Metal Ion ◽  
Ph Range ◽  
Short Time ◽  
Hydrolysis Of

The six-carbon intermediate of the ribulose 1,5-bisphosphate (RuBP) carboxylase reaction, 2'-carboxy-3-keto-D-arabinitol 1,5-bisphosphate (CKABP), was prepared enzymatically by quenching the reaction with acid after a short time ( ca 12 ms). Over a wide pH range (4-11), GKABP undergoes a slow ( t 1/2 = 1 h), pH-independent decarboxylation. No detectable decomposition of CKABP occurs over a six-week period at — 80 °C. The decarboxylation of CKABP is acid-catalysed and is also catalysed by deactivated enzyme lacking the activator carbamate-divalent metal ion complex. Decarboxylation is accompanied by β-elimination of the C-1 phosphate from the 2,3-enediolate. Under alkaline conditions (pH >11) CKABP undergoes hydrolysis. Non-enzymatic hydrolysis of the intermediate is also accompanied by β-elimination of the C-1 phosphate (presumably from the aci-acid of the upper glycerate 3-phosphate) and the formation of pyruvate. Fully activated enzyme catalyses the complete hydrolysis of CKABP to glycerate 3-phosphate, although enzymic hydrolysis of CKABP is limited by an event not on the direct path of carboxylation. Carbon-13 NMR analysis of [2',3- 13 C]CKABP indicates that it exists in solution predominantly (> 85%) as the C-3 ketone. In contrast, borohydride trapping of CKABP formed from [3- 18 O]RuBP indicates that the intermediate exists on the enzyme predominantly (> 94%) as the hydrated C-3 gem-diol. In solution, the hydration of the C-3 ketone of CKABP proceeds slowly ( k = 2.5 x 10 -3 s -1 ). The enzymatic hydration of CKABP must proceed at least as fast as k cat ( ca. 5 s -1 ) or at least 2000 times faster than the hydration of CKABP in solution.

A sensitive detection of Cr(vi) in wide pH range using polyethyleneimine protected silver nanoclusters

2016 ◽  
Vol 8 (28) ◽  
pp. 5684-5689 ◽  
Author(s):  
Na Xu ◽  
Quan Zhu ◽  
Xiang-Yue Kong ◽  
Lei Meng
Keyword(s):  
Fluorescence Probe ◽  
Silver Nanoclusters ◽  
Sensitive Detection ◽  
Trace Level ◽  
Wide Ph Range ◽  
Alkaline Conditions ◽  
Ph Range

A sensitive fluorescence probe of polyethyleneimine protected silver nanoclusters (AgNCs@PEI) was proposed for the detection of trace level of Cr(vi) in both acidic and alkaline conditions.

scholarly journals A Comparison Study on Fluorescence Properties of Formononetin and Ononin

2021 ◽  
Author(s):  
Jinjin Cao ◽  
Fang Lv ◽  
Ting Liu ◽  
Luchen Niu ◽  
Bocong Han ◽  
...  
Keyword(s):  
Fluorescence Enhancement ◽  
Alkaline Condition ◽  
Excitation Wavelength ◽  
Comparison Study ◽  
Spectral Difference ◽  
Experimental Conditions ◽  
Pyrone Ring ◽  
Wide Ph Range ◽  
Alkaline Conditions ◽  
Ph Range

Abstract In this work, reasons for the spectral difference between two isoflavones, Formononetin (F) and ononin (FG), are explained in the viewpoint of molecular structure through a comparison study of the fluorescence features of the two. The fluorescence enhancement of FG in hot alkaline condition is reported for the first time. For F, there was almost no fluorescence under acidic conditions, but when pH>5, its fluorescence began to increase with increasing pH due to the proton ionization of 7-OH. In the range of pH 9.3-12.0, the anion form of F produced a fairly strong and stable fluorescence with maximum excitation wavelength (λex) of 334 nm and emission wavelength (λem) of 464 nm, its fluorescence quantum yield (Yf) was measured to be 0.042. And for FG, its aqueous solution fluoresced weakly in a wide pH range until it was placed under hot alkaline conditions, which was presumed to the cleavage reaction of the γ-pyrone ring in FG by observing a significant fluorescence at λex / λem =288 / 388nm, and Yf was determined to be 0.020. The fluorescence sensitization methods of F and FG both exhibit low limits of detection (2.60 ng·mL-1, 9.30 ng·mL-1) and wide linear ranges (0.0117-1.86 μg·mL-1, 0.0146-2.92μg·mL-1). Although the structural relationship between F and FG is glycoside and aglycone, FG cannot be translated to F by glucoside hydrolysis under hot alkaline condition, the fluorescence enhancement mechanisms of the two are essentially different. The fluorescence difference between the two under different experimental conditions lays the foundation for future fluorescence quantitative analysis.

Mitigation of High Temperature Challenges in Limestone Acidizing through the use of Chelating Agents

2021 ◽  
Author(s):  
Mandeep Khan ◽  
Mohammed Qamruzzaman ◽  
Dhirendra Chandra Roy ◽  
Ravi Raman
Keyword(s):  
High Temperature ◽  
Chelating Agents ◽  
Elevated Temperatures ◽  
Chelating Agent ◽  
Point Of View ◽  
Core Flooding ◽  
Agent Based ◽  
Asphaltene Deposition ◽  
Wide Ph Range ◽  
Ph Range

Abstract Acid jobs with conventional acid systems like hydrochloric acid in high temperature conditions is challenging on various fronts. Enhanced reactivity of strong acids results in poor penetration and severe face dissolution. Also, it aggravates the issue of corrosion of downhole equipment and may also result in sludge formation/asphaltene deposition. Worldwide, chelating agents has emerged as a standalone stimulation fluid for high temperature acidizing. Their unique attributes and properties have been proved very useful for acid jobs at elevated temperatures. However, the chelating agents-based formulations need to be carefully evaluated on various acidization parameters for a fruitful stimulation. Mumbai Offshore field has been encountering the above-mentioned problems in acidizing of its high temperature (>275°F) limestone reservoirs. The paper presents innovative solutions devised for high temperature matrix acidizing. Two chelating agents viz., EDTA (Ethylenediaminetetraceticacid) and GLDA (L-Glutamic Acid N, N-diacetic acid) were explored and evaluated with meticulous laboratory studies. The performance of the chelating agent-based stimulation fluid was compared with acetic acid. Slurry tests were performed to quantify the dissolving power of each acid. Consequently, core flooding tests were carried out to to find the optimum pH of the chelating agents from stimulation point of view. Core flooding studies were performed at anticipated injection rates on representative core samples from a payzone A, with BHT 275-290° F, from Mumbai Offshore. pH optimized formulations were tested against N-80 metallurgy coupons at reservoir temperature for corrosion potential estimation. Also, sludge, asphaltene and emulsion formation tendencies were analyzed with representative oil samples. The results convey that both EDTA and GLDA were able to mitigate the challenges encountered at elevated temperatures. EDTA and GLDA were found to stimulate the cores with wormholes formed at wide pH range with no face dissolution observed. Chelating agents enjoyed good dissolving power with negligible corrosion rates, absence of sludge and asphaltene deposition, compatibility with formation fluid and excellent iron control properties.

scholarly journals Influence of pH and Contaminant Redox Form on the Competitive Removal of Arsenic and Antimony from Aqueous Media by Coagulation

Minerals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 574 ◽  
Author(s):  
Muhammad Ali Inam ◽  
Rizwan Khan ◽  
Du Ri Park ◽  
Babar Aijaz Ali ◽  
Ahmed Uddin ◽  
...  
Keyword(s):  
Binary System ◽  
Quaternary System ◽  
Aqueous Media ◽  
Single System ◽  
Redox Species ◽  
Wide Ph Range ◽  
Alkaline Conditions ◽  
Ft Ir ◽  
Ph Range ◽  
Removal Of Arsenic

In most countries, arsenic (As) and antimony (Sb) are regulated pollutants, due to their significant impacts on the environment and human health. Iron-based (Fe) coagulants play a fundamental role in the removal of both elements from aqueous media. This study aims to investigate the competitive removal of As and Sb in relation to Fe solubility. Coagulation experiments were conducted in synthetic water under various pH and contaminant loading, using ferric chloride (FC) as a coagulant. In the single system, the pentavalent species significantly reduced the Fe solubility and thereby enhanced the mobility of As and Sb under these environmental conditions. The coexistence of pentavalent and trivalent species in the binary system considerably decreases the Fe solubility at acidic conditions while enhancing the dissolution under alkaline conditions, thus affecting the overall removal of both species. The presence of four redox species in the quaternary system decreases the Fe solubility remarkably over a wide pH range, with better Sb removal, as compared to As under similar conditions. The adsorption study of the single system showed a decrease in As(V) adsorption capacity at higher concentration, while in the binary system, the Sb(III) showed strong adsorption potential, compared to other species. In the quaternary system, the presence of all four redox species has a synergistic effect on total Sb adsorption, in comparison to the total As. Furthermore, the results of Fourier transform infrared (FT-IR) analysis of FC composite contaminant flocs confirm that the combined effect of charge neutralization and inner sphere complexation might be a possible removal mechanism. These findings may facilitate the fate, transport and comparative removal of redox species in the heterogeneous aquatic environment.

scholarly journals Thermostable Cellulases from the Yeast Trichosporon sp.

2019 ◽  
Vol 2019 ◽  
pp. 1-6 ◽  
Author(s):  
Hanane Touijer ◽  
Najoua Benchemsi ◽  
Mohamed Ettayebi ◽  
Abdellatif Janati Idrissi ◽  
Bouchra Chaouni ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
Cellulose Fiber ◽  
Cellulosic Biomass ◽  
Measured Temperature ◽  
Cellulolytic Microorganisms ◽  
Lignocellulosic Substrates ◽  
Wide Ph Range ◽  
Ph Range ◽  
Hydrolysis Of ◽  
Optimal Ph

Objectives. Identification of cellulolytic microorganisms is of great interest to the hydrolysis of cellulosic biomass. This study focuses on the identification of cellulolytic yeasts and the optimization of cellulase activities produced by the best performing isolate. Results. 30 cellulolytic yeast isolates were selected. Enzymes produced by an isolate from the Trichosporon genus showed the property to hydrolyze different substrates: carboxymethyl cellulose (CMC), cellulose fiber, and filter paper (FP). The optimum measured temperature was 55°C for CMCase and 60°C for FPase. The optimal pH was 5 for CMCase and 4 to 6 for FPase. The effect of the substrates concentration showed that the best activities were obtained at 100 mg/mL CMC or FP. The highest activities were 0.52 for the CMCase and 0.56 for the cellulase fiber at 10 min incubation, 0.44 IU/mL at 15 min incubation, and 24 h FPase preincubation. Conclusion. Cellulases produced by the studied yeast are capable of hydrolyzing soluble and insoluble substrates at elevated temperatures and at a wide pH range. They are considerable interest in the production of fermentable sugars from lignocellulosic substrates.

Rapid Crystallization and Kinetic Freezing of Site-Disorder in the Lithium Superionic Argyrodite Li6PS5Br

2019 ◽  
Author(s):  
Ajay Gautam ◽  
Marcel Sadowski ◽  
Nils Prinz ◽  
Henrik Eickhoff ◽  
Nicolo Minafra ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
Synthesis Method ◽  
Reaction Times ◽  
Ionic Conductivities ◽  
Ionic Transport ◽  
High Energy ◽  
Superionic Conductors ◽  
Rapid Crystallization ◽  
Site Disorder ◽  
Fast Cooling

<p>Lithium argyrodite superionic conductors are currently being investigated as solid electrolytes for all-solid-state batteries. Recently, in the lithium argyrodite Li<sub>6</sub>PS<sub>5</sub>X (X = Cl, Br, I), a site-disorder between the anionsS<sup>2–</sup>and X<sup>–</sup>has been observed, which strongly affects the ionic transport and appears to be a function of the halide present. In this work, we show how such disorder in Li<sub>6</sub>PS<sub>5</sub>Br can be engineered <i>via</i>the synthesis method. By comparing fast cooling (<i>i.e. </i>quenching) to more slowly cooled samples, we find that anion site-disorder is higher at elevated temperatures, and that fast cooling can be used to kinetically trap the desired disorder, leading to higher ionic conductivities as shown by impedance spectroscopy in combination with <i>ab-initio</i>molecular dynamics. Furthermore, we observe that after milling, a crystalline lithium argyrodite can be obtained within one minute of heat treatment. This rapid crystallization highlights the reactive nature of mechanical milling and shows that long reaction times with high energy consumption are not needed in this class of materials. The fact that site-disorder induced <i>via</i>quenching is beneficial for ionic transport provides an additional approach for the optimization and design of lithium superionic conductors.</p>

Polarographic and spectrophotometric behaviour of some N-p-phenyl substituted benzamidines

1991 ◽  
Vol 56 (12) ◽  
pp. 2791-2799 ◽  
Author(s):  
Juan A. Squella ◽  
Luis J. Nuñez-Vergara ◽  
Hernan Rodríguez ◽  
Amelia Márquez ◽  
Jose M. Rodríguez-Mellado ◽  
...  
Keyword(s):  
Spectrophotometric Study ◽  
Absorption Bands ◽  
Electrochemical Parameters ◽  
Wide Ph Range ◽  
Group A ◽  
Substituent Constants ◽  
Ph Range ◽  
The Waves

Five N-p-phenyl substituted benzamidines were studied by DC and DP polarography in a wide pH range. Coulometric results show that the overall processes are four-electron reductions. Logarithmic analysis of the waves indicate that the process are irreversible. The influence of the pH on the polarographic parameters was also studied. A UV spectrophotometric study was performed in the pH range 2-13. In basic media some variations in the absorption bands were observed due to the dissociation of the amidine group. A determination of the pK values was made by deconvolution of the spectra. Correlations of both the electrochemical parameters and spectrophotometric pK values with the Hammett substituent constants were obtained.

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