scholarly journals Catalytic Degradation of Chitosan by Supported Heteropoly Acids in Heterogeneous Systems

Catalysts ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1078
Author(s):  
Hang Zhang ◽  
Zhipeng Ma ◽  
Yunpeng Min ◽  
Huiru Wang ◽  
Ru Zhang ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Molecular Weight ◽  
Catalytic Activity ◽  
Activated Carbon ◽  
Reaction Time ◽  
High Molecular Weight ◽  
Reaction Temperature ◽  
Water Soluble ◽  
High Catalytic Activity ◽  
High Molecular Weight Chitosan

Several kinds of composite materials with phosphotungstic acid (PTA) as the catalyst were prepared with activated carbon as support, and their structures were characterized. According to the Box–Behnken central combination principle, the mathematical model of the heterogeneous system is established. Based on the single-factor experiments, the reaction temperature, the reaction time, the amount of hydrogen peroxide and the loading capacity of PTA were selected as the influencing factors to study the catalyzed oxidation of hydrogen peroxide and degradation of high molecular weight chitosan. The results of IR showed that the catalyst had a Keggin structure. The results of the mercury intrusion test showed that the pore structure of the supported PTA catalyst did not change significantly, and with the increase of PTA loading, the porosity and pore volume decreased regularly, which indicated that PTA molecules had been absorbed and filled into the pore of activated carbon. The results of Response Surface Design (RSD) showed that the optimum reaction conditions of supported PTA catalysts for oxidative degradation of high molecular weight chitosan by hydrogen peroxide were as follows: reaction temperature was 70 ℃, reaction time was 3.0 h, the ratio of hydrogen peroxide to chitosan was 2.4 and the catalyst loading was 30%. Under these conditions, the yield and molecular weight of water-soluble chitosan were 62.8% and 1290 Da, respectively. The supported PTA catalyst maintained high catalytic activity after three reuses, which indicated that the supported PTA catalyst had excellent catalytic activity and stable performance compared with the PTA catalyst.

scholarly journals Enhancing thermostability of iron ethylene polymerization catalysts through N,N,N-chelation of doubly fused α,α′-bis(arylimino)-2,3:5,6-bis(hexamethylene)pyridines

2019 ◽  
Vol 9 (8) ◽  
pp. 1933-1943 ◽  
Author(s):  
Zheng Wang ◽  
Randi Zhang ◽  
Wenjuan Zhang ◽  
Gregory A. Solan ◽  
Qingbin Liu ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Catalytic Activity ◽  
High Molecular Weight ◽  
Ethylene Polymerization ◽  
High Catalytic Activity ◽  
Polymerization Catalysts ◽  
Fe Catalyst

At temperatures up to 80 °C, high catalytic activity and high molecular weight PE was achievable using the Fe-catalyst depicted.

Study on Bio-Fuels Drop Acid by [BSPy]HSO4 Catalytic Esterification

2013 ◽  
Vol 781-784 ◽  
pp. 2433-2437 ◽  
Author(s):  
Ai Hua Zhang ◽  
Zhi Hong Xiao ◽  
Liang Bo Zhang ◽  
Ru Kuan Liu ◽  
Wu Hong Zhong ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Reaction Time ◽  
Reaction Temperature ◽  
Acid Value ◽  
Esterification Reaction ◽  
Process Conditions ◽  
High Catalytic Activity ◽  
Brønsted Acidic Ionic Liquid ◽  
The Stability ◽  
Acid Esterification

Research on the synthesis of BrOnsted acidic ionic liquid by the method of solvent, the pyrolysis bio-fuel with cornus wisoniana oil drop acid esterification reaction, the catalyst dosage, reaction time and reaction temperature on the effects of the acid dropping and in the best optimization under the condition of the stability of the catalyst were investigated. The experimental results show that [BSPHSO4 with high catalytic activity, optimization of process conditions as follows: 1.2% of catalyst, reaction temperature 75 °C, reaction time of 70 min, acid value reduced to 2.0 mg KOH/g. By optimizing the cycle experiment, the stability of the catalyst performance is good, the catalytic activity is relatively stable.

Chemoselective hydrogen peroxide oxidation of primary alcohols to aldehydes by a water-soluble and reusable iron(iii) catalyst in pure water at room temperature

2017 ◽  
Vol 41 (6) ◽  
pp. 2372-2377 ◽  
Author(s):  
Qi Yan ◽  
Ye Chen Fang ◽  
Yun Xue Jia ◽  
Xin Hong Duan
Keyword(s):  
Hydrogen Peroxide ◽  
Catalytic Activity ◽  
Room Temperature ◽  
Pure Water ◽  
Water Soluble ◽  
High Catalytic Activity ◽  
Peroxide Oxidation ◽  
Primary Alcohols ◽  
Hydrogen Peroxide Oxidation

A novel, water-soluble and reusable FeCl3 catalyst showed high catalytic activity and chemoselectivity in the H2O2-oxidation of primary alcohols into aldehydes.

Syndiospecific polymerization of styrene by half-titanocene catalysts with the sulfur-containing donor ligand

e-Polymers ◽  
2014 ◽  
Vol 14 (4) ◽  
pp. 277-281 ◽  
Author(s):  
Wei Wang ◽  
Gang Zheng ◽  
Hongtao Wang
Keyword(s):  
Molecular Weight ◽  
Catalytic Activity ◽  
High Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
High Catalytic Activity ◽  
Narrow Molecular Weight Distribution ◽  
Donor Ligand ◽  
High Yields ◽  
Sulfur Containing

AbstractMonocyclopentadienyl titanium complexes of the type Cp*TiX2 L (Cp*=C5 Me5, 1: L=C6 F5 S, X=OMe; 2: L=C6 F5 S, X=Cl; 3: L=2, 6-Me2-C6 H3 S, X=OMe) have been synthesized with high yields. These complexes are used as the catalysts for the syndiospecific polymerization of styrene. High catalytic activity is observed, and a polymer with high molecular weight and narrow molecular weight distribution is obtained. It is concluded that not only the sulfur-containing donor ligand but also the anion ligand strongly affects the polymerization activity and the molecular weight of the resultant polymer.

Effects of Polymerization Parameters on Aqueous Deposited Copolymerization of Acrylonitrile and Itaconic Acid

2013 ◽  
Vol 774-776 ◽  
pp. 508-511
Author(s):  
Ya Qi Zhao ◽  
Qiao Feng ◽  
Ling Zhi Du
Keyword(s):  
Molecular Weight ◽  
Reaction Time ◽  
High Molecular Weight ◽  
Reaction Temperature ◽  
Itaconic Acid ◽  
Temperature Region ◽  
Monomer Concentration ◽  
Initiator Concentration ◽  
Molecular Weights ◽  
Total Monomer Concentration

Pure powdery high molecular weight polyacrylonitrile (HMW-PAN) copolymers were firstly synthesized by aqueous deposited polymerization (ADP) technique employing 2,2'-Azobis (isobutyramidine) dihydrochloride (AIBA) as initiator and itaconic acid (IA) as comonomer. Various PAN polymers were obtained through changing different polymerization parameters. It is indicated that with the increase of total monomer concentration, initiator concentration, reaction temperature and reaction time, polymerization conversions of PAN copolymers all increased. While the molecular weights become greater with the increase of total monomer concentration. With the increase of initiator concentration and reaction temperature (under higher reaction temperature region), the molecular weights decreased. However, the molecular weights only had very little decrease at the end of long extension of reaction time.

scholarly journals Oligochitosan Hydrochloride: Preparation and Characterization

INEOS OPEN ◽  
2021 ◽  
Vol 4 ◽  
Author(s):  
V. E. Tikhonov ◽  
◽  
B. B. Berezin ◽  
I. V. Blagodatskikh ◽  
E. A. Bezrodnykh ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Molecular Weight ◽  
Hydrochloric Acid ◽  
Physicochemical Properties ◽  
High Molecular Weight ◽  
Synthetic Approach ◽  
European Pharmacopoeia ◽  
High Molecular Weight Chitosan ◽  
Analytical Protocols

The methods commonly used for depolymerization of chitosan and preparation of oligochitosan are discussed. A synthetic approach to oligochitosan hydrochloride with a molecular weight below 16 kDa based on the treatment of parent industrial high molecular weight chitosan with a mixture of hydrochloric acid and hydrogen peroxide is described. A series of analytical protocols are used to determine the physicochemical properties and quality of resulting oligochitosan hydrochloride according to the European Pharmacopoeia 4.0.

scholarly journals Physicochemical and Antifungal Properties of Clotrimazole in Combination with High-Molecular Weight Chitosan as a Multifunctional Excipient

Marine Drugs ◽  
2020 ◽  
Vol 18 (12) ◽  
pp. 591
Author(s):  
Bożena Grimling ◽  
Bożena Karolewicz ◽  
Urszula Nawrot ◽  
Katarzyna Włodarczyk ◽  
Agata Górniak
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Weight Ratio ◽  
Scanning Calorimetry ◽  
Minimal Inhibitory Concentrations ◽  
Dissolution Tests ◽  
Effective Combination ◽  
The Impact ◽  
High Molecular Weight Chitosan

Chitosans represent a group of multifunctional drug excipients. Here, we aimed to estimate the impact of high-molecular weight chitosan on the physicochemical properties of clotrimazole–chitosan solid mixtures (CL–CH), prepared by grinding and kneading methods. We characterised these formulas by infrared spectroscopy, differential scanning calorimetry, and powder X-ray diffractometry, and performed in vitro clotrimazole dissolution tests. Additionally, we examined the antifungal activity of clotrimazole–chitosan mixtures against clinical Candida isolates under neutral and acid conditions. The synergistic effect of clotrimazole and chitosan S combinations was observed in tests carried out at pH 4 on Candida glabrata strains. The inhibition of C. glabrata growth reached at least 90%, regardless of the drug/excipient weight ratio, and even at half of the minimal inhibitory concentrations of clotrimazole. Our results demonstrate that clotrimazole and high-molecular weight chitosan could be an effective combination in a topical antifungal formulation, as chitosan acts synergistically with clotrimazole against non-albicans candida strains.

Effect of High Molecular Weight Water-Soluble Chitosan on the Trabecular Bone and Thickness in Ovariectomized Rats

2007 ◽  
Vol 29 (3-4) ◽  
pp. 439-449 ◽  
Author(s):  
Han-Jung Chae ◽  
Geun-Youn Lee ◽  
Sun-Kyung Yang ◽  
Do-Sung Kim ◽  
Ki-Jung Yun ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Trabecular Bone ◽  
High Molecular Weight ◽  
Water Soluble ◽  
Ovariectomized Rats

Interaction of Streptococcus mutans Glucosyltransferases with Teichoic Acids

1980 ◽  
Vol 29 (2) ◽  
pp. 376-382
Author(s):  
H. K. Kuramitsu ◽  
L. Wondrack ◽  
M. McGuinness
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Streptococcus Mutans ◽  
Teichoic Acid ◽  
Lipoteichoic Acid ◽  
Water Soluble ◽  
Heat Inactivation ◽  
Teichoic Acids ◽  
Insoluble Glucan

The Streptococcus mutans GS5 glucosyltransferase activities (both water-soluble and -insoluble glucan-synthesizing fractions) were inhibited by purified lipoteichoic acid. In vitro sucrose-dependent colonization of smooth surfaces by strain GS5 was also markedly reduced in the presence of the amphipathic molecules. The inhibition of soluble glucan synthesis by lipoteichoic acid appeared to be competitive with respect to both sucrose and primer dextran T10. These inhibitory effects were dependent on the presence of the fatty acid components of lipoteichoic acid since deacylated lipoteichoic acids did not inhibit glucosyltransferase activity. However, the deacylated molecules did interact with the enzymes since deacylated lipoteichoic acid partially protected the enzyme activity against heat inactivation and also induced the formation of high-molecular-weight enzyme complexes from the soluble glucan-synthesizing fraction. The presence of teichoic acid in high-molecular-weight aggregates of glucosyltransferase isolated from the culture fluids of strain GS5 was suggested by the detection of polyglycerophosphate in these fractions. In addition to strain GS5, two other organisms containing polyglycerophosphate teichoic acids, Lactobacillus casei and Lactobacillus fermentum , were demonstrated to bind glucosyltransferase activity. These results are discussed relative to the potential role of teichoic acid-glucosyltransferase interactions in enzyme binding to the cell surface of S. mutans and the formation of high-molecular-weight enzyme aggregates in the culture fluids of the organism.

Sign in / Sign up

Export Citation Format

Share Document