Liquid Phase Zinc Chloride Process

Zinc chloride is also a catalyst for a liquid-phase process using concentrated hydrochloric acid at 100-150°C. Hydrochloric acid may be generated in situ by reacting sodium chloride with sulfuric acid. As mentioned earlier, methyl chloride may also be produced directly from methane with other chloromethanes. However, methyl chloride from methanol may be further chlorinated to produce dichloromethane, chloroform, and carbon tetrachloride. 

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. 

For example, rearrangement of a-pinene oxide produces, among the ten or so major products, campholenic aldehyde, the precursor of the sandalwood fragrance santalol. The conventional process employs stoichiometric quantities of zinc chloride but excellent results have been obtained with a variety of solid acid catalysts (see Fig. 2.23), including a modified H-USY [70] and the Lewis acid Ti-Beta [71]. The latter afforded campholenic aldehyde in selectivities up to 89% in the liquid phase and 94% in the vapor phase. 

At about 98% conversion, hexamethylene diamine is obtained in 90% yield. The process is a liquid-phase operation, carried out at 120°C. The catalyst is a triphenyl phosphite-Ni(0) complex. It appears that the addition of a promoter such as zinc chloride to the nickel ligand results in a composition that catalyzes the conversion of 2-methylbutenenitrile (the undesired branched isomer) into the linear 3-pentenenitrile [173], which may be recycled into the second process step for isomerization to 4-pentenenitrile. 

Several studies on the use of phosphonium ionic liquids for selective extraction of metal cations from aqueous solution were reported. Binnemans and co-workers described a green extraction process in which cobalt was separated as a tetrachlorocobaltate(ii) complex in a tri(he yl)tetradecylphosphonium chloride ionic liquid phase. This left behind nickel, magnesium and calcium in the aqueous phase. The overall process showed a vety low environmental impact since no additional organic solvents were required. Other processes to extract zinc(n) nickel(II) and cobalt(II), cadmium (11), palladium and... 

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