Method for producing .alpha.-(p-isobutylphenyl)propionic acid or its alkyl esters

A method for producing .alpha.-(p-isobutylphenyl)-propionaldehyde which comprises the following steps of:

• (I) reacting isobutylbenzene and acetaldehyde in the presence of sulfuric acid to produce 1,1-bis (p-isobutylphenyl) ethane under the condition that the concentration of said sulfuric acid in the reaction system is not lower than 75% by weight based on the sum of the weights of sulfuric acid and any water formed in the reaction system, the concentration of said acetaldehyde in the reaction system is maintained at 1% by weight or lower, and said isobutylbenzene is added in excess relative to said acetaldehyde;
• (II) catalytically cracking said 1,1-bis(p-isobutylphenyl) ethane in a liquid phase at reaction temperatures in the range of 200.degree. to 350.degree. C. in the presence of a protonic acid catalyst or in a gaseous phase at reaction temperatures in the range of 300.degree. to 650.degree. C. in the presence of a solid acid catalyst or a protonic acid carrying-solid acid catalyst to produce p-isobutylstyrene and isobutylbenzene as main products;
• and
• (III) reacting said p-isobutylstyrene with carbon monoxide and hydrogen at temperatures in the range of 40.degree. to 150.degree. C. at a reaction pressure in the range of 5 to 500 kg/cm.sup.2 in the presence of a metal complex carbonylation catalyst to produce .alpha.-(p-isobutylphenyl)-propionaldehyde.

A method for producing .alpha.-(p-isobutylphenyl)propionic acid which comprises the following steps of:

• (I) reacting isobutylbenzene and acetaldehyde in the presence of sulfuric acid to produce 1,1-bis(p-isobutylphenyl) ethane under the conditions that the concentration of said sulfuric acid in the reaction system is not lower than 75% by weight based on the sum of the weights of said sulfuric acid and any water in the reaction system, the concentration of said acetaldehyde in the reaction system is maintained at 1% by weight or lower, and said isobutylbenzene is added in excess relative to said acetaldehyde.
• (II) catalytically cracking said 1,1-bis(p-isobutylphenyl) ethane in a liquid phase at reaction temperatures in the range of 200.degree. to 350.degree. C. in the presence of a protonic acid catalyst or in a gaseous phase at reaction temperatures in the range of 300.degree. to 650.degree. C. in the presence of a solid acid catalyst or a protonic acid carrying-solid acid catalyst to produce p-isobutylsytrene and isobutylbenzene as main products;
• (III) reacting said p-isobutylstyrene with carbon monoxide and hydrogen at temperatures in the range of 40.degree. to 150.degree. C. at a reaction pressure in the range of 5 to 500 kg/cm.sup.2 in the presence of a metal complex carbonylation catalyst to produce .alpha.-(p-isobutylpheneyl)-propionaldehyde;
• and
• (IV) oxidizing said .alpha.-(p-isobutylphenyl)propionaldehyde to produce .alpha.-(p-isobutylphenyl) propionic acid.