The two step process to produce acrylic acid front propylene is the predominant technology practiced commercially. The economics of this process are compared with the direct oxidation of propane to acrylic acid in a fixed bed, turbulent fluidized bed (TFB) and circulating fluidized bed (CFB). Economies of scale are difficult to realize in fixed beds due to the limited heat transfer surface, and therefore, several reactors are required in parallel. A single reactor train is possible due to the excellent heat transfer characteristics of the TFB and CFB. The economics of the TFB are superior to either the CFB or multi-tubular fixed beds. However, both investment and operating costs are sensitive to selectivity. A CFB could become the reactor of choice if lattice oxygen can be shown to improve selectivity and conversion. In order for propane to replace propylene as the preferred feed-stock, selectivity must be at least 65 %, which has yet to be demonstrated in practice.