Solid-phase place exchange reaction

The objectives of this work are to study the influence of gold particles on the properties of typical catalyst supports, namely MgO and TiO. Gold has been chosen because of its relatively low catalytic activity except for oxygen transfer reactions (4). MgO, an insulator, and TiO, a semiconducting material, are widely used as catalyst supports, and for both of them metal-support interactions have been reported in the literature. Our study places main emphasis on the role of gold on thermal stability, phase transformations, solid-phase oxygen exchange activity, and adsorption characteristics of the oxides. 

Effective catalysts for preparing the polyformals were p-toluenesulfonic acid, camphorsulfonic acid, methanedisulfonic acid, and perchloric acid. Various other acidic compounds were evaluated as catalysts with tetramethylcyclobutanediol. In these experiments, 0.5 to 1.0 gram of acidic compound per mole of tetramethylcyclobutanediol was normally added. If insufficient water was obtained, more catalyst was added. If the prepolymer was obtained but an appreciable amount of brown color was present, less catalyst was then used. Compounds which did not catalyze the reaction (no water obtained) were phosphoric acid, zinc chloride, trifluoroacetic acid, and heptafluorobutyric acid. Incomplete reactions (insufficient water) took place with concentrated hydrochloric acid, concentrated nitric acid, zinc fluoroborate, or Amberlite IRC-50 ion exchange resin as catalyst. A prepolymer was obtained when boron trifluoride etherate was used, but buildup did not take place in the solid phase (catalyst probably too volatile). Brown or speckled-brown polymers (after solid-phase buildup) were obtained with catalysts containing sulfonic acid groups (benzenesulfonic, dodecylbenzenesulfonic, sulfo-acetic, methanetrisulfonic, sulfuric, p-toluenesulfonic, camphorsulfonic, and methanedisulfonic acids). To obtain white polymers from tetramethylcyclobutanediol it was necessary to treat the solvent and prepolymer reaction mixture as previously described. (White polyformals were obtained from the other diols without this treatment.)... 

An ion exchange reaction is usually considered as taking place between a solid and a liquid phase. A degree of flexibility in this definition is required in order to accommodate the various organic liquid ion exchangers which have found important application over the last 40 years, especially in the field of extraction metallurgy. The... 

Isotopic molecular oxygen can undergo three reactions in presence of a catalyst. The first reaction, the homogeneous exchange, is a scrambling of the oxygen isotopes which can take place either in the gas phase or on the catalyst surface without participation of oxygen from the solid phase. 

A comprehensive model for heterogeneous solubilization was also developed by Naik and Doraiswamy (1997), which accounts for ion exchange in the solid phase, interphase transport of the quat species, and the organic reaction. In this case, ion exchange taking place in the solid phase can be one of the rate controlling steps, since access to the anions in... 

Addition of soluble inorganic phosphorus to soil increases the soil pore water phosphorus concentration. This results in rapid adsorption of phosphorus onto soil surfaces to maintain equilibrium. Soil s capacity to adsorb additional phosphorus dictates the concentration of phosphorus in soil pore water. These adsorption processes occur within a short time period. When soil particles become saturated with phosphorus, there is an increase in phosphorus concentration in soil pore water. Reaction kinetics are on the order of minutes to hours to reach sorption equilibrium. Figure 9.21 illustrates a two-step process in which rapid phosphate exchange takes place between soil pore water and soil particles or mineral surface (adsorption) followed by slow penetration (absorption) of phosphate into solid phase. Similarly, desorption of phosphorus can also... 

Because the triphase reaction involves not merely diffusion of a single phase into the solid support, the organic reaction take places in the organic phase, and the ion-exchange reaction occurs in the aqueous phase. The catalyst support is usually lipophilic. The organic phase and aqueous phase fill the catalyst pores to form the continuous phase and the disperse phase, respectively. The interaction between quaternary salts as well as... 

It is fair to say that all metabolic processes are based on, or can be traced back to, chemical processes. By their very nature, however, many of them take place in the liquid or solid phase dictated by the cell structure in which they occur. On the other hand, many of the processes and reactions involve fundamental reactions exchanging gaseous specimens at the outer interface of a cell. An example is our respiration oxygen is extracted from the inhaled air and toxic exchange gases are expelled from the body during exhalation, e.g. one can smell in the breath of a person whether they have been drinking alcohol. 

Garcia Jimenez et al. proposed the analysis of additive mixtures by FIA, including a monolithic minicolumn placed in Figure 24.5 or before the flow cell of a monochannel FIA setup with no prior derivatization reaction. Accordingly, they developed flowthrough spectrophotometric sensors (UV absorption) based on the transient retention of analytes on several solid phases, namely, ion exchanger Sephadex DEAE A-25 [73], silica... 

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