New AlPO4-sepiolite systems as acid catalysts, I. Preparation, texture, surface-chemical properties and cyclohexene skeletal isomerization conversion

ABSTRACTThree different TiO2-SiO2 gels (Xerogel, Carbogel and Aerogel) are more active acid catalysts than other reference samples used here. As deduced from FTIR, XRD and XANES studies, the structural properties of these gels are quite different to each other, thus revealing the strong influence of the drying treatment. It is found that the degree of Si-O-Ti linking and the surface acidity follows the same trend (X 〉 C 〉 A). We conclude that supercritical drying at 600 K and 190 bars can induce Ti leaching followed by redeposition in the narrower pores of the gel. These effects modify both the textural and surface chemical properties of the resulting material.

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Effects of chemical treatment as an adjunctive of air‐abrasive debridement on restoring the surface chemical properties and cytocompatibility of experimentally contaminated titanium surfaces

Journal of Biomedical Materials Research Part B Applied Biomaterials ◽

10.1002/jbm.b.34377 ◽

2019 ◽

Vol 108 (1) ◽

pp. 183-191 ◽

Cited By ~ 1

Author(s):

Yuki Ichioka ◽

Takashi Kado ◽

Izumi Mashima ◽

Futoshi Nakazawa ◽

Kazuhiko Endo ◽

...

Keyword(s):

Chemical Treatment ◽

Chemical Properties ◽

Surface Chemical ◽

Titanium Surfaces

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Effect of High-Temperature Defibration on the Chemical Structure of Hardwood

Holzforschung ◽

10.1515/hf.2002.009 ◽

2002 ◽

Vol 56 (1) ◽

pp. 51-59 ◽

Cited By ~ 16

Author(s):

P. Widsten ◽

J.E. Laine ◽

P. Qvintus-Leino ◽

S. Tuominen

Keyword(s):

High Temperature ◽

Lignin Content ◽

Bulk Composition ◽

Chemical Properties ◽

Water Extract ◽

Fiber Surface ◽

Phenolic Hydroxyl ◽

Hydroxyl Groups ◽

Surface Chemical ◽

Alkyl Aryl

Summary The present paper aims at elucidating the effect of high-temperature defibration at different temperatures on the bulk and surface chemical properties of defibrated birch, aspen and eucalypt. The results indicate that defibration of these hardwoods results in partial depolymerization of fiber lignin via (homolytic) cleavage of interunit alkyl-aryl (β-O-4) ether bonds. This increases the phenolic hydroxyl content and produces relatively stable (phenoxy) radicals. Syringyl-type lignin is more extensively depolymerized than guaiacyl-type lignin. Defibration generates water-extractable material, which is enriched in hemicellulose-derived carbohydrates and has a substantial content of aromatic compounds rich in phenolic hydroxyl groups. The amount of water-extract and the extent of lignin interunit ether bond cleavage increase with an increase in defibration temperature. The differences between various hardwood species in this respect are small. The surface chemical composition of the fibers differs considerably from their bulk composition, but is not significantly influenced by variations in defibration temperature. Lipophilic extractives cover a large portion of the fiber surface, while the lignin content of lipophilic extractives-free fiber surfaces is 2–3 times as high as the bulk lignin content of the fibers.

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