Improvements in or relating to the production of acrolein

Acrolein is produced by reacting propylene and oxygen at elevated temperature in the presence of an oxidation catalyst, e.g. bismuth molybdate or phosphomolybdate, or comprising tin and antimony oxides as in Specification 864,666 or cobalt molybdate as in Specification 878,803, within a multi-tubular fixed bed reactor containing parallel tubes terminating in an end box or header space, the process being characterised in that the gases leaving the catalyst are immediately cooled, within the end box or header space of the reactor, either by direct or indirect heat exchange, to between 400 and 150 DEG C., preferably 250 and 180 DEG C. and maintained within this range until the gases enter the recovery system for isolation or are passed to a further reaction system, especially for conversion over an oxidation catalyst with molecular oxygen to acrylic acid. Steam or inert gases may be utilized as direct contact heat exchange media. In the examples, which contain comparative data of operation without cooling, propylene, air, steam mixtures are allowed to react over tin antimony catalysts.