A method to minimize catalyst deactivation rate and coke laydown, and maximize desired reaction rate in processing of industrially significant reactions under supercritical conditions to generate a reaction mixture stream including formed reaction products and reactants, said contacting at a desired catalyst temperature of about 1-1.2 critical temperature of the resulting reaction mixture and at a pressure between the critical pressure of the reaction mixture and a pressure necessary to establish said reaction mixture fluid density of greater than 0.65 gm/cc.