Optimization of synthesis of ethyl-tret-butyl ether used as high octane additives to motor fuels was implemented. Process has been realized on the basis of al­ky­la­ti­on reaction of ethanol with isobutylene in presence of new heterogeneous catalyst. By method of multidimensional analysis the best conditions for obtaining a tar­get product have been found out tar­get: temperature – 20–50⁰C and ratio ethanol:isobutylene – 3:1.