Vapor-phase treatment

The new Brownsville, Tex., plant for the manufacture of synthetic liquid fuels from natural gas makes use of this reaction to increase the octane number of its product by as much as 20 units. Synthetic naphtha produced over iron catalyst is highly olefinic and contains substantial amounts of straight-chain isomers with terminal double bonds (8). The shifting of these double bonds toward the center of the molecule may be accomplished by vapor-phase treatment employing synthetic cracking catalyst in the fluid state, under mild catalytic cracking conditions. Oxygenated compounds also present are converted under the isomerization conditions to hydrocarbons and water. 

A large number of catalysts and swelling agents have been studied for the acetylation reaction. The best acetylation conditions have been reported in vapor phase treatment with uncatalysed acetic anhydride in xylene solutions at 100-130 C (28). Acetylation reaction between wood and acetic anhydride proceeds as follows 0... 

Table III. Effect of Behavior Various in Chir. Swelling Agents and Catalysts on (4 Hour Vapor-Phase Treatment with WPG and Shrinkage-Swelling Thioacetic Acid.)(41) ...

The fibrous acetylation process is performed in the presence of a suitable liquid, such as benzene, in which the reaction product is insoluble and which thereby retains the fiber form. For fibrous acetylation vapor-phase treatment with acetic anhydride can also be used. Besides sulfuric acid, perchloric acid and zinc chloride have been used as catalysts. 

Very recently, zeolites have also been modified by chlorine (13) and chlorine-related compounds at high temperature (14, 15). The known modification methods can be further classified as either liquid or vapor phase treatments. The acid washing, organic complexing agent extraction and chromic salt treatments fall into the first class while the steaming and the chlorine and related compounds reactions belong to the second class. 

The problem of mass vapor-phase methods for the deacidification of books or textiles has received a great deal of attention in the last few years. Such treatments are best applied to current books in which the paper is still strong. Rebuilding strength into textiles or books by a vapor-phase treatment is eminently desirable. Both problems are discussed in this volume. When solved, the processes will probably be carried out in special plants by chemists rather than by conservators. 

Usually, basic catalysts have been used in the reaction. The early work was done by Zimakov and Pokrovskil [38], McMillin [39], Barnes et al. [40], etc. For a typical example, ethylene oxide (EO), catalyzed with triethylamine, was used as a vapor phase treatment [39]. 

The reaction with acetic anhydride can be conducted in a liquid or vapor phase. However, the vapor phase treatment results in a product with poorer properties than the liquid phase [51]. Therefore, the treatment has been carried out usually in liquid phase. Goldstein et al. [49] reported that uncatalyzed acetylation in xylene at 100-130°C is the best condition. 

The ESCA results do not indicate a dramatic change in C/Si ratios following HMDS treatment, liquid or vapor phase 0/Si ratios of HMDS treated samples, particularly after vapor phase treatment, do indicate a detectable lowering of the relative oxygen surface concentration compared to blank wafers, consistent with dehydration which is known to also occur with HMDS treatment Q). 

Acetylation can also be done by vapor-phase treatments, but the diffusion rate varies inversely as the square of the thickness (37, 56). Because of this effect, vapor-phase treatment has been applied only to thin veneers. 

There are four vapor phase treatment processes (a) thermal destruction, (b) catalytic incinerahon, (c) ozone destruction with ultraviolet radiation, and (d) granular carbon adsorption (GAC). Processes a-c are not widely utilized due to cost and/or effectiveness of treatment. Thermal destruction is an effective process, but the operating cost is very high due to energy requirements. Catalytic incineration, shown in Fig. 7, has lower energy requirements compared to the thermal destruction process, but it is not effective in eliminating low levels of chlorinated organic compounds. Ozone destruction with an ultraviolet radiation process has limited performance data available as a result, the performance of this process must be examined in a pilot study for the particular VOC in question in order to determine operational parameters. The most commonly used vapor phase treatment process for VOC is carbon adsorption. 

Demetallation of Heteroatom Zeolites through High-temperature Vapor-phase Treatment... 

H. Yuan, Y. Nishiyama, and S. Kuga, Surface esterification of cellulose by vapor-phase treatment with trifluoroacetic anhydride, Cellulose, 12 (2005) 543-549. 

Protection of Glass Fibers. This is definitely produced by vapor phase treatment with organosUanes. They coat the glass fibers and keep them from scratching and weakening each other. Since they provide coupling later, this is a double benefit. 

Some fibers can be coated with polymer layers by immersing them in an electrolyte, where electrochemical polymerization takes place, or by vapor-phase treatment of oxidant-containing carriers with the monomers (Mafinauskas 2001). In this latter case, fibrous materials are charged by sorption with FeClj, provided from aqueous or ethereal solution, and then treated with a pyrrole vapor, either in vacuum or from its solution in toluene. 

R. J. Ruderman, C.W.R. Wade, WD. Shepard, cuid F. Leoncffd, Prolonged resorption of collagen sponges Vapor-phase treatment with formaldehyde, /. Biomed. Mater. Res., 7, 263-265,1973. 

Chlorine containing species not only attack surface hydroxyl but react with most metals and metal oxides forming the rather volatile metal chlorides and oxychlorides. This is the basis for the purification of the porous body by vapor phase treatment. A generalized reaction with CI2 is shown as follows ... 

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