Equipment for alkylations

Materials of Construction. In a great many cases, steel is suitable for the construction of alkylating equipment, even in the presence of the strong acid catalysts, as their corrosive effect is greatly lessened by the formation of esters as catalytic intermediate products. In the petroleum industry, sulfuric acid and hydrogen fluoride are employed on a very large scale as alkylation catalysts however, these must be substantially anhydrous to be effective so steel equipment is satisfactory. Where conditions are not anhydrous, lead-lined, Monel-lined, or enamel-lined equipment is satisfactory. In a few cases, copper or tinned copper is still used, as in the manufacture of pharmaceutical and photographic products, to lessen contamination with metals. 

Corrosion of Apparatus. Corrosion may be caused by the catalyst used in the alkylation or by the hydrogen halides formed by hydrolysis of alkyl halides. In the preparation of the N-alkyl compounds, the original amines or the alkylamines formed have an inhibiting action against corrosion. However, there are many cases in which the agents used in alkylation are corrosive. In the alkylation of aniline to diethylaniline by heating aniline and ethyl alcohol, sulfuric acid cannot be used, because it will form ether consequently, hydrochloric acid is employed, but these conditions are so corrosive that the steel autoclaves used to resist the pressure must be fitted with replaceable enameled liners. 

Certain other alkylations employing alkyl halides are carried out in an acidic medium. For exmnple, hydrobromic add is formed when methyl 

Special attention must be given to moving parts and instruments to protect against fouling due to corrosion. If steel is to be used in parts under corrosive conditions, such as valves, the parts must be designed with ample 

When dimethyl or diethyl sulfate can be used advantageously, a jacketed stirred kettle is generally used, and in these cases, the operation is carried 

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