In accordance with one or more embodiments, a tubular catalyst-containing reactor system is provided. The system includes a housing and a vaporizer unit in the housing comprising a helically wound tubular assembly for receiving and at least partially vaporizing a liquid chemical reactant stream. A reformer unit in the housing receives a vaporized chemical reactant stream from the vaporizer unit. The reformer unit comprises a helically wound tubular assembly connected to and positioned coaxially relative to the helically wound tubular assembly of the vaporizer unit. The helically wound tubular assembly of the reformer unit contains a catalyst for catalyzing formation of gas product stream from the vaporized chemical reactant stream. A burner unit heats the vaporizer unit and the reformer unit. The burner unit receives a fuel stream and an air stream and produces a flame generally inside the helically wound tubular assemblies of the vaporizer unit and the reformer unit.

The invention relates to a method which comprises emitting ultrasound into a liquid mixture containing first and second reagents in separate phases initially separated by a liquid precursor-gas barrier, the ultrasound having a high enough energy level to vaporize the precursor gas, such as to contact the reagents and thus to activate a chemical reaction therebetween.

A fluidized catalytic reactor connected to a start-up heater is provided. The start-up heater provides sufficient heat to a catalyst containing stream to gradually increase the feed temperature. This allows for a critical volumetric flow rate to be achieved so that catalyst can be recovered from product instead of being entrained in product.