An apparatus for alkyl oxygenate (e.g., methanol) manufacture via partial oxidation of alkane (methane) has an injectively-mixed backmixing reaction chamber in fluid communication with a tubular-flow reactor. The injectively-mixed backmixing reaction chamber induces alkyl free radicals prior to input to the tubular-flow reactor. Injective intermixing of feed streams agitates the backmixing reaction chamber. In one embodiment, a variable position bulkhead axially moves to commensurately modify the backmixing reaction chamber and tubular-flow reactor volumes. In another embodiment, the tubular-flow reactor has a variable position quenching input. Both “hairbrush” and conical input inserts facilitate turbulent injective admixing of the input feed streams in the injectively-mixed backmixing reaction chamber. A condensing scrubber is also used for treating the output stream from the reaction system.