Step-change variation of acid concentration in a percolation reactor for hydrolysis of hardwood hemicellulose

2000 ◽  
Vol 72 (3) ◽  
pp. 289-294 ◽  
Author(s):  
Sung Bae Kim ◽  
Dong Moon Yum ◽  
Soon Chul Park
Keyword(s):  
Acid Concentration ◽  
Step Change ◽  
Percolation Reactor ◽  
Hydrolysis Of

Hydrolysis of trioxaadamantane ortho esters. I. Dialkoxycarbocation – ortho ester equilibrium and acidity function

1984 ◽  
Vol 62 (6) ◽  
pp. 1068-1073 ◽  
Author(s):  
Robert A. McClelland ◽  
Patrick W. K. Lam
Keyword(s):  
Acid Concentration ◽  
Intramolecular Interaction ◽  
Uv Spectroscopy ◽  
Equilibrium Constants ◽  
Hydrolysis Product ◽  
Acidity Function ◽  
Ortho Ester ◽  
Aromatic Substituent ◽  
Ortho Esters ◽  
Hydrolysis Of

3-Aryl-2,4,10-trioxaadamantane ortho esters (T) undergo a rapid equilibration with a ring-opened dioxan-2-ylium ion (DH+) prior to hydrolysis to product (a 1,3,5-cyclohexanetriol monobenzoate). The cation is stable in concentrated H2SO4 solutions where it has been characterized by nmr spectroscopy. It is observed using uv spectroscopy in dilute acids, and the ratio [DH+]/[T] at equilibrium has been measured as a function of acidity. Reversibility of the ring opening is established by the pattern of plots of cation absorbance versus acid concentration and by the observation that solutions containing cation on neutralization or dilution yield ortho ester, not hydrolysis product. Equilibrium constants for the reaction [Formula: see text] have been measured by obtaining the acidity function HT for this system. The effects of the aromatic substituent and the steepness of the acidity function plot versus acid concentration are interpreted in terms of a strong intramolecular interaction in the cation between the cationic center and the hydroxyl oxygen.

scholarly journals Organic Acid-Catalyzed Subcritical Water Hydrolysis of Immature Citrus unshiu Pomace

Foods ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 18
Author(s):  
Sang-Bin Lim
Keyword(s):  
Citric Acid ◽  
Organic Acid ◽  
Acid Concentration ◽  
Subcritical Water ◽  
Biological Activities ◽  
Citrus Unshiu ◽  
Citric Acid Concentration ◽  
Acid Catalyzed ◽  
Inhibitory Activities ◽  
Hydrolysis Of

Immature Citrus unshiu pomace (ICUP) was hydrolyzed under organic acid-catalyzed, subcritical water (SW) conditions to produce flavonoid monoglucosides (hesperetin-7-O-glycoside and prunin) and aglycons (hesperetin and naringenin) with high biological activities. The results of single-factor experiments showed that with 8 h of hydrolysis and an increasing citric acid concentration, the yield of flavonoid monoglucosides (hesperetin-7-O-glycoside and prunin) increased from 0 to 7% citric acid. Afterward, the hesperetin-7-O-glycoside yield remained constant (from 7 to 19% citric acid) while the pruning yield decreased with 19% of citric acid, whereas the aglycon yield increased continuously. In response surface methodology analysis, a citric acid concentration and hydrolysis duration of 13.34% and 7.94 h were predicted to produce the highest monoglucoside yield of 15.41 mg/g, while 18.48% citric acid and a 9.65 h hydrolysis duration produced the highest aglycon yield of 10.00 mg/g. The inhibitory activities of the SW hydrolysates against pancreatic lipase (PL) and xanthine oxidase (XO) were greatly affected by citric acid concentration and hydrolysis duration, respectively. PL and α-glucosidase inhibition rates of 88.2% and 62.7%, respectively, were achieved with 18.48% citric acid and an 8 h hydrolysis duration, compared to 72.8% for XO with 16% citric acid and 12 h of hydrolysis. This study confirms the potential of citric acid-catalyzed SW hydrolysis of ICUP for producing flavonoid monoglucosides and aglycons with enhanced enzyme inhibitory activities.

scholarly journals Chemical Hydrolysis of the Polysaccharides of the Tamarind Seed

2017 ◽  
Vol 56 (4) ◽  
Author(s):  
Juan Carlos González-Hernández ◽  
Lorena Farías Rosales ◽  
Miguel Ángel Zamudio Jaramillo ◽  
Mariana Álvarez-Navarrete ◽  
Juan Carlos Vera Villa ◽  
...  
Keyword(s):  
Acid Concentration ◽  
Reducing Sugars ◽  
Xylitol Production ◽  
Tamarind Seed ◽  
Chemical Hydrolysis ◽  
Feasible Option ◽  
Production Stages ◽  
Main Production ◽  
Biotechnological Processes ◽  
Hydrolysis Of

<p>Biotechnological processes with lignocellulose materials are promising technologies for the production of chemicals and energy involving the same main production stages: hydrolysis of the hemicellulose and the cellulose to monomeric sugars, fermentation, recovery of the product, and concentration. We studied the effect of different treatments on the release of reducing sugars (RS) from seeds. Three factors were tested: temperature from 86 to 130.2 °C; acid concentration, 0.32 to 3.68% (v/v); and exposure time, from 13.2 to 40 min. Two acids were tested. Temperature and time were the factors that had more effect on hydrolysis, whereas no interactions between factors had a significant effect on the release of RS. The best conditions for RS release were for both acids (2% v/v), 130.2 °C, and 30 min, with a concentration of about 110 g/L. Results suggest tamarind seed is a feasible option for xylitol production.</p>

The hydrolysis of thioacetic, thiobenzoic, and three substituted thiobenzoic acids in perchloric and sulfuric acids

1978 ◽  
Vol 56 (7) ◽  
pp. 935-940 ◽  
Author(s):  
John T. Edward ◽  
Graeme Welch ◽  
Sin Cheong Wong
Keyword(s):  
Sulfuric Acid ◽  
Activity Coefficients ◽  
Acid Concentration ◽  
Perchloric Acid ◽  
Transition States ◽  
Sulfuric Acid Concentration ◽  
Thiobenzoic Acid ◽  
The Difference ◽  
Different Response ◽  
Hydrolysis Of

The rates of hydrolysis of thioacetic, thiobenzoic, and three substituted thiobenzoic acids increase with concentration of solvent sulfuric or perchloric acid to a maximum in 30–40% acid and then decrease. Yates–McClelland r, Bunnett–Olsen [Formula: see text], and Hammett ρ parameters, and entropies of activation indicate an AAC2 mechanism over this range of acid concentrations. In acid concentrations above 50–60% the rates increase sharply and the same mechanistic criteria now indicate an AAc1 mechanism. The difference between the rate–acidity profile of thiobenzoic acid and that of ethyl thiolbenzoate can be explained by the different response of the activity coefficients of their transition states to increase in sulfuric acid concentration.

Effect of Ultrasound on Acid-Alcohol Treated Hydrolysis of Starch

2011 ◽  
Vol 391-392 ◽  
pp. 1330-1333
Author(s):  
Jie Zheng ◽  
Lin Yang ◽  
Rong Liu ◽  
Zhi Hua Zhang ◽  
Qian Li ◽  
...  
Keyword(s):  
Hydrochloric Acid ◽  
Acid Concentration ◽  
Reaction Temperature ◽  
Corn Starch ◽  
Alcohol Concentration ◽  
Hydrochloric Acid Concentration ◽  
Factors Affecting ◽  
Fat Substitutes ◽  
Hydrolysis Of ◽  
Temperature Time

Excessive intake of fat will damage human health seriously, and it can also cause obesity, high blood pressure, atherosclerosis and coronary heart disease. So low fat foods gradually become highly widespread. As a result, fat substitutes are focused, which have the same physical and sensory properties as fat, and can be used in place of fat in many cases. In this work, fat substitute was prepared by acid-alcohol treated hydrolysis of corn starch with and without ultrasound. Some factors affecting the DE of starch hydrolysate were investigated by experiments with and without ultrasound, including reaction temperature, time, ethanol concentration, and hydrochloric acid concentration. Enhancements of the hydrolysis by ultrasound was observed.The results showed that the DE increased with the rise of reaction temperature, time and hydrochloric acid concentration. However, it decreased as the increase of alcohol concentration. Ultrasound can accelerate the hydrolysis evidently, and increased the DE by at least 22.22%.

THE HYDROLYSIS OF ACID AMIDES IN CONCENTRATED HYDROCHLORIC ACID SOLUTIONS

1942 ◽  
Vol 20b (5) ◽  
pp. 73-81 ◽  
Author(s):  
B. S. Rabinovitch ◽  
C. A. Winkler
Keyword(s):  
Activation Energy ◽  
Hydrochloric Acid ◽  
Acid Concentration ◽  
Reaction Rates ◽  
Activation Energies ◽  
Acid Solutions ◽  
Hydrochloric Acid Solutions ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

The Arrhenius constants have been evaluated for the hydrolysis of formamide, acetamide, propionamide, and benzamide in hydrochloric acid solutions over the concentration range 1 to 10 N. There is approximate correspondence between reaction rates and activation energies for the series of amides. An increase in observed activation energy with increasing acid concentration was found for all amides. The maximum in rate of hydrolysis, which occurs at higher acid concentrations, is discussed and accounted for by the variation in the Arrhenius constants with acid concentration.

Complexes of Nickel(II) and Copper(II) With 5,5,7-Trimethyl-1,4-Diazepane. Preparation and Kinetics of Acid-Hydrolysis

1986 ◽  
Vol 39 (2) ◽  
pp. 239 ◽  
Author(s):  
NF Curtis
Keyword(s):  
Acid Hydrolysis ◽  
Acid Concentration ◽  
Reaction Rates ◽  
Borohydride Reduction ◽  
Kinetics Of Hydrolysis ◽  
Rapid Reaction ◽  
Kinetics Of ◽  
Hydrolysis Of

The cyclic diamine 5,5,7-trimethyl-1,4-diazepane, tmdz, is formed by borohydride reduction of 5,7,7-trimethyl-2,3,6,7-tetrahydro-1H-1,4- diazepine , which is formed by a rapid reaction between ethanediamine and 4-methylpent-3-en-2-one. Salts of the cations [Ni( tmdz )2]2+ and [Cu( tmdz )2]2+ were prepared, and their properties are reported. The kinetics of hydrolysis of [Ni( tmdz )2]2+ and [Cu( tmdz )2]2+ and bis (1,4- diazepane )nickel(II), [Ni( dach )2]2+, in aqueous HCl/NaCl media have been studied. Reaction rates are independent of acid concentration over the ranges used . Ni2+,0.1-1 mol l-1 H+ in 1 mol l-1 Cl -, kobs(25°C) = 9.1(1)×10-7 s-1, kobs(50°C) = 2.0(1)×10-5 s-1,ΔH‡96(2)kJ mol-1,0.08-4 mol l-1, H+ in 4 mol l-1 Cl -, kobs (25°pC) = 2.0(3)°10-7 s-1. Cu2+, 0.04-1 mol l-1 H+, 1 mol l-1 Cl -, kobs (25°C) = 0.028(2) s-1, for the displacement of the second ligand . [Ni( dach )2]2+, 0.1-1 mol l-1 H+, 1 mol l-1 Cl -, kobs (25°C) = 0.051(2) s-1. [Ni( tmdz )2]2+ reacts more rapidly with NaOH/edta : 1 mol l-1 NaOH , 0.1 mol l-1, Na2(edtaH2), kobs (25°C) = 7.3(3)×10-3 s-1, 0.5 mol l-1 NaOH , 0.1 mol l-1 Na2(edtaH2), kobs (25°C) = 4.5(3)×10-3 s-1.

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