Vapour-phase hydrolysis

The kinetics of vapour phase hydrolysis of aryl chlorides... 

A typical example of such materials is fumed (or pyrogenic) silica, which is produced by a vapour phase hydrolysis of silicon tetrachloride SiCL in an oxygen-hydrogen flame (Brinkmann et al. 2006) ... 

Titaniiun dioxide used as a support was prepared in different manners such as vapour-phase hydrolysis of titanium tetrachloride, hydrolysis of titanium sulfate and butylate in an aqueous medium. After thermal treatment at 550°C, the samples of TiO represented anatase with a specific surface area from 20 to 100m2/g. 

After suitable hydrolysis the techniques outlined above may be used for DCAA determination. As yields of vapour phase hydrolysis have been shown to be consistently higher than those of the classical 6mol/LHCl/110°C/24h method Keil and Kirchman, 1991) the first technique is described in the following (Tsugita et al., 1987). 

It was first described in 1608 when it was sublimed out of gum benzoin. It also occurs in many other natural resins. Benzoic acid is manufactured by the air oxidation of toluene in the liquid phase at 150°C and 4-6 atm. in the presence of a cobalt catalyst by the partial decarboxylation of phthalic anhydride in either the liquid or vapour phase in the presence of water by the hydrolysis of benzotrichloride (from the chlorination of toluene) in the presence of zinc chloride at 100°C. 

Obtained synthetically by one of the following processes fusion of sodium ben-zenesulphonate with NaOH to give sodium phenate hydrolysis of chlorobenzene by dilute NaOH at 400 C and 300atm. to give sodium phenate (Dow process) catalytic vapour-phase reaction of steam and chlorobenzene at 500°C (Raschig process) direct oxidation of cumene (isopropylbenzene) to the hydroperoxide, followed by acid cleavage lo propanone and phenol catalytic liquid-phase oxidation of toluene to benzoic acid and then phenol. Where the phenate is formed, phenol is liberated by acidification. 

Some companies are successfully integrating chemo- and biocatalytic transformations in multi-step syntheses. An elegant example is the Lonza nicotinamide process mentioned earlier (.see Fig. 2.34). The raw material, 2-methylpentane-1,5-diamine, is produced by hydrogenation of 2-methylglutaronitrile, a byproduct of the manufacture of nylon-6,6 intermediates by hydrocyanation of butadiene. The process involves a zeolite-catalysed cyciization in the vapour phase, followed by palladium-catalysed dehydrogenation, vapour-pha.se ammoxidation with NH3/O2 over an oxide catalyst, and, finally, enzymatic hydrolysis of a nitrile to an amide. 

Investigations carried out have shown that controlled hydrolysis co-precipitation method and sol-gel method with use of polyvinylalcohol as template allow to prepare superacid WO3/Z1O2 materials which are highly active in n-hexane isomerization and vapour-phase benzene nitration with nitric acid. Doping of WO3/Z1O2 with Fe and Mn ions, as well as with silica and alumina [6] does not improve the catalytic properties in n-hexane isomerization. 

Metaxylenol is an important intermediate for the manufacture of para chloro meta xylenol which is used a disinfectant. Meta xylenol may be produced by liquid phase or by vapour phase reaction. Metaxylenol is produced by sulphonation of xylene followed by hydrolysis in liquid phase but this yeilds many other by-products(l,2,3). However, catalytic conversion of isophorone yields meta xylenol selectively and the amounts of other by-products can be controlled (4,5,6). 

Nicotinic acid is an important intermediate for pharmaceuticals and serves as a provitamin in food additives for animal feeding. It is produced by the Lonza process (involving oxidation of 2-methyl-5-ethyl pyridine using nitric acid) or by the Degussa process.The latter process involved hydrolysis of P-cyanopyridine, which in turn was produced by amminoxidation of P-picoline. A third process involving selective vapour phase oxidation of P-picoline catalysed by vanadium titanium oxide catalyst has also been described. ... 

General Methods.—Trost and his co-workers have extended their earlier studies of the synthesis of cyclopentanes based on thermolysis of vinylcyclopropanes, and shown that it is expedient to use the recently developed 1-lithiocyclopropyl phenyl sulphide (32) for the preparation of the appropriate vinylcyclopropane precursor. Thus addition of (32) to ketone (33), followed by dehydration of the intermediate hydroxy-sulphide with SOCI2, led to (34), which on thermolysis in the vapour phase at 350 °C, then hydrolysis, gave the cyclopentenone (35). An identical approach to cyclopentane annelation has been used by Miller in a synthesis of (36) from cyclopent-2-enone. 

---