Surface dehydration

Soc. Japan 47 1139-1142 Kaneko, K. Inouye, K. (1976) Electrical conductivity changes in a-FeOOH and K-FeOOH upon surface dehydration. Bull. Chem. Soc. Japan 49 3689-3690... 

Conventional heating and microwave heating of food products result in significantly different end products. Foods heated conventionally are subjected to relatively high surface temperatures, 350-450 degrees F., which results in product surface dehydration. 

Matsui H., Wagner V.E., Hill D.B., Schwab U.E., Rogers T.D., Buttom B., Taylor R.M., Superfine R., Rubinstein M., Iglewski R.H. and Boucher R.C. (2006) A physical linkage between cystic fibrosis airway surface dehydration and Pseudomonas aeruginosa biofilms. Proc Natl Acad Sci USA 103, 18131-18136... 

We have seen that cations are exposed by the surface dehydration of rutile. These cus ions act as Lewis acid (acceptor) sites for the adsorption of pyridine, ammonia... 

If the first step in the oxidation of hydrocarbons is the production of peroxy radicals (HO2, RO2) and peroxides (ROOH, HOOH, ROOR ), we see that the next stage must involve the decomposition of these intermediates, cither by free radical attack on the peroxides or by unimolecular decomposition. An additional mode of destruction is by surface dehydration to form IT2O + aldehyde. 

See work by M. Szwarc, J. Polymer Sci., 16, 367 (1955), on the decomposition of the acyl peroxides in liquid phase. Surface dehydration will produce H2O and aldehydes from the peroxy acids. 

Among the various intrinsic defects at the MgO surface, the oxygen vacancy has received the strongest attention. O vacancies can be created by thermal treatments of hydroxylated MgO surfaces. The treatment conditions of the sample, such as the temperature of calcination and the extent of surface dehydration, significantly affect the morphology and defectivity of the oxide... 

In many cases, dehydration to the aldehyde occurs at a rate slow enough to allow the hydrated form to escape from the electrode surface. Dehydration in the bulk allows other schemes for protecting the aldehyde. 

The experimental results confirm that lattice oxygen participates in the reaction. Water is formed at two sites the first part comes from the reaction of gaseous nitric oxide and adsorbed ammonia via an Eley-Rideal mechanism the other part comes from a surface dehydration process. Two adjacent V =0 groups were supposed to be the active site. From the work of Lietti and Forzatti [69] it appeared that the oxygen atoms of monomeric species are less reactive than those of polymeric metavanadate species. 

It is generally agreed that surface dehydration, typically at 600—800 K in vacuo, is a prerequisite for activity. There is still some debate as to whether ZnO must be non-stoicheiometric or not for activity to be observed, but it will become clear that it is now generally accepted that Zn-O pair sites are the active surface centres. As expected for a weak Bronsted acid, reactions of non-cyclic alkenes are limited to non-skeletal isomerizations even at 573 K isobutene does not isomerize to n-butenes. ... 

Depasse, J., Coagulation of colloidal sflica by alkaline cations Surface dehydration or interparticle bridging , J. Colloid Intetf. Sci., 194. 260. 1997. 

Dehydration of the Silica Surface. Dehydration of the silica surface, that is, removal of physisorbed water, occurs at relatively low temperatures. The threshold temperature corresponding to the completion of dehydration and the beginning of dehydroxylation by condensation of surface OH groups is estimated to be 190 10 °C (53). 

A detailed analysis of different contributions to the enthalpy and entropy changes, for a number of protein-adsorbent systems, was carried out by Norde. Lyklema, and others 117,103,118,119], They showed that the protein adsorption on solids is often endothermic and that the driving force of the process is the positive ASaiis. The main contributions to large positive values of entropy can arise from sorbent surface dehydration and from the conformational rearrangement of protein molecules upon adsorption [17]. 

Salting-out is not well understood. One popular explanation for this effect relies on the relative hydration of the protein versus bulk electrolyte. In this model, the electrolyte is assumed to bind bulk water as water of hydration near the ion s surface. Likewise, the protein needs to be hydrated with water. As the bulk electrolyte and the protein compete for bulk water to hydrate their respective surfaces, the protein become partially dehydrated and prefers to fill such exposed surface (dehydrated surface) with other protein molecules thus, facilitating crystal contacts. Thus, the solubility of the protein is reduced as the electrolyte is added to the protein solution. The effectiveness of ions (cations and anions) to cause phase separation (or lower solubility) has been documented by... 

To make yuba, one needs to make a rich soymilk. The soymilk is then heated in a flat, open pan to near boiling (-80—90°C) a film gradually forms on the liquid surface due to surface dehydration. After the film becomes toughened it can be lifted with two sticks or by passing a rod underneath. The film is hung on a line or spread... 

On some surfaces dehydration can occur in addition to dehydrogenation, and it is therefore imagined that in such cases, a second type of... 

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