Use of a reactor system comprising: one or more supercritical upgrading reactors and one or more supercritical upgrading standby reactors, in which the one or more supercritical upgrading reactors and the one or more supercritical standby reactors operate at a temperature greater than a critical temperature of water and a pressure greater than a critical pressure of water; where the one or more supercritical upgrading reactors and the one or more supercritical upgrading standby reactors comprise a first catalyst layer and a second catalyst layer, the second catalyst layer disposed vertically below the first catalyst layer in the one or more supercritical upgrading reactors and the one or more supercritical upgrading standby reactors; where the first catalyst layer and the second catalyst layer comprise at least a heterogeneous porous metal containing catalyst; where the first catalyst layer comprises a first void volume ratio and the second catalyst layer comprises a second void volume ratio where the second void volume ratio is lesser than the first void volume ratio; and one or more controllers coupled to at least one of the one or more supercritical upgrading reactors and at least one of the one or more supercritical standby reactors, in which the controller allows the supercritical upgrading reactor and the supercritical standby reactor to alternate functions, such that the supercritical standby reactor is converted to a supercritical upgrading reactor that upgrades a combined feed stream and the supercritical upgrading reactor is converted to a supercritical standby reactor that performs a cleaning operation by the delivery of a cleaning fluid, for supercritical upgrading of a petroleum-based composition. one or more supercritical upgrading reactors and one or more supercritical upgrading standby reactors, in which the one or more supercritical upgrading reactors and the one or more supercritical standby reactors operate at a temperature greater than a critical temperature of water and a pressure greater than a critical pressure of water; where the one or more supercritical upgrading reactors and the one or more supercritical upgrading standby reactors comprise a first catalyst layer and a second catalyst layer, the second catalyst layer disposed vertically below the first catalyst layer in the one or more supercritical upgrading reactors and the one or more supercritical upgrading standby reactors; where the first catalyst layer and the second catalyst layer comprise at least a heterogeneous porous metal containing catalyst; where the first catalyst layer comprises a first void volume ratio and the second catalyst layer comprises a second void volume ratio where the second void volume ratio is lesser than the first void volume ratio; and one or more controllers coupled to at least one of the one or more supercritical upgrading reactors and at least one of the one or more supercritical standby reactors, in which the controller allows the supercritical upgrading reactor and the supercritical standby reactor to alternate functions, such that the supercritical standby reactor is converted to a supercritical upgrading reactor that upgrades a combined feed stream and the supercritical upgrading reactor is converted to a supercritical standby reactor that performs a cleaning operation by the delivery of a cleaning fluid, for supercritical upgrading of a petroleum-based composition.