NOVELTY - Producing olefins and aromatic compounds from a feedstock, comprises: introducing a hydrocarbon feedstock and a catalyst composition within a reactor; monitoring the temperature in the reactor at at least one location that is at or adjacent to the inlet; modifying one or more parameters; allowing at least a portion of the feedstock to be converted to at least one of olefins and aromatic compounds within the reactor; and removing a product stream containing the olefins and aromatic compounds from the outlet of the reactor.    USE - The method is useful for producing olefins and aromatic compounds from a feedstock including polyolefins, polyethylene, polypropylene, polystyrene, polyethylene terephthalate (PET), PVC, polyamide, polypolycarbonate, polyurethane, polyester, natural and synthetic rubber, tires, filled polymers, composites, plastic alloys, plastics dissolved in a solvent, biomass, bio oils and petroleum oils (all claimed).    ADVANTAGE - The process ensures effective conversion of plastics directly to petrochemical products, such as olefins and aromatics that minimize formation of methane and that maximizes the yield of olefins and aromatics.    DETAILED DESCRIPTION - Producing olefins and aromatic compounds from a feedstock, comprises: introducing a hydrocarbon feedstock and a catalyst composition that is suitable for converting the feedstock to at least one of olefins and aromatic compounds within a reactor having at least one inlet for introducing the feedstock, and the catalyst composition and having at least one outlet for removing reaction products from the reactor that is spaced from the inlet along a reactor flow path having a length (L) between the inlet and the outlet; monitoring the temperature in the reactor at at least one location that is at or adjacent to the at least one inlet at a temperature-monitoring distance that is 0.3 L or less from the inlet; in response to one or more monitored temperatures from the at least one location, modifying one or more parameters; allowing at least a portion of the feedstock to be converted to at least one of olefins and aromatic compounds within the reactor; and removing a product stream containing the olefins and aromatic compounds from the outlet of the reactor.