• Made M a n y Clathrates. Heart of the new pxocess is clathrating agents. These h a v e a metal atom, an anion, and a basic nitirogen compound. (Clathration processes w h i c h use urea or thiourea are n o t based on complexes.) A typical example is tetra-(4-acetylpyri*:£*?& dino) nidkel dithiocyanate. Component metals can include cobalt, iron, or manganese?. Pyridine a n d quinoline or their derivatives can b e used as t h e nitrogen c o m p o u n d . F o r the anion, it could be a. thiocyanate, chloride, bromide, cyanide, o r nitrite. So far, a d d s Dorsey, over 1 0 0 different complexes h a v e been made—combinations whiich c a n be used t o separate ISOMER many chemicals from various process or product: streams. Each clathration complex i s highly selective for a given isomer or isomers. Tetra-(^-methylpyridino) nickel diCLATHRATION — Sefoo f i v e separation o f isom- | thiocyanate can be used t o recover ers b y crystal formation p-xylene o r p-cymene t o make terephwifh\niefcillic-nitro comthalic acid - Today p-xylene production plexes^ runs about: 80 million pounds per year. And it is expected to get higher—perhaps to 1 0 0 million pounds per year _ _: J shortly. So far over 100 different complexes have b e e n m a d e which can b e used to Besides the p-xylene prospect, t h e separate many chemicals from various product streams. Each of these clathrat- new process c a n be used t o separate ing complexes is selective for a given isomer or isomers. When process streams m-xylene, which in turn is u s e d to make a r e treated w i t h the solid complexes, isomers are held as crystals until released isophthalic acid. Significant too: It is b y a solvent a new w a y to separate ethylbenzene and thus could provide this material in volume fox direct conversion t o styrene. • O t h e r Prospects. The clathration process m a y solve problems which have hel
