Catalytic transformations of m-xylene in presence of aluminum silicates

Summary

• 1. A study was made of the conditions required for the isomerization of m-xylene in presence of gumbrin and of a synthetic aluminum silicate catalyst at different temperatures and pressures.

• 2. In presence of gumbrin the isomerization of m-xylene proceeds most smoothly at 450‡ under atmospheric pressure and at a space velocity of 0.5 hour⁻¹. Under these conditions the yield of p-xylene attains 91.2% of the equilibrium amount.

• 3. The use of reduced pressure (50 mm) favors the complete elimination of undesirable methylation and demethylation reactions and makes it possible to obtain almost 100% of liquid catalyzate containing 15.6% of p-xylene. The use of hydrogen under pressure (15 atm) results in the complication of the isomerization reaction by side reactions.

• 4. The synthetic aluminum silicate was a less effective catalyst than gumbrin in that it favored side reactions and gas formation to a greater extent.

• 5. In presence of Pt-Al₂O₃ at 500‡, m-xylene was again isomerized into the o- and p-isomers, but simultaneous formation of toluene (up to 5.5%) and trimethylbenzenes (up to 2.5%) occurred.