INTEGRATED METHOD FOR PRODUCING ACROLEIN AND 3-METHYLMERCAPTO PROPIONALDEHYDE

Producing (P1) 3-methylmercaptopropionaldehyde, comprises: e.g. (a) oxidizing mixture of propylene (3) and inert diluent gases with air (1) over heterogeneous catalyst (7) to obtain gaseous oxidation reaction mixture comprising acrolein and byproducts; (b) quenching the mixture to obtain gas stream comprising acrolein, and quench liquid comprising residual acrolein and byproducts; (c) recovering acrolein by stripping from quench liquid in lower portion of quench (b) and returning stripped acrolein to quench step (b); (d) absorbing first portion of gas stream from the quench (b) in water. Producing (P1) 3-methylmercaptopropionaldehyde, comprises: (a) oxidizing a mixture of propylene (3) and inert diluent gases with air (1) over a heterogeneous catalyst (7) to obtain a gaseous oxidation reaction mixture comprising acrolein and byproducts; (b) quenching the gaseous oxidation reaction mixture to obtain a gas stream comprising acrolein, and a quench liquid comprising residual acrolein and the byproducts; (c) recovering the acrolein by stripping from the quench liquid in a lower portion of the quench (b) and returning the stripped acrolein to the quench step (b); (d) absorbing a first portion of the gas stream comprising acrolein from the quench step (b) in water to obtain an aqueous acrolein solution and an uncondensable gaseous stream comprising inert gases; (e) recycling at least a portion of the uncondensable gaseous stream to the oxidation step (a) to supply the inert diluent gases; (f) distilling the acrolein from the aqueous acrolein solution to obtain an acrolein-free aqueous bottom product; (g) condensing the distilled acrolein; and (h) reacting the distilled acrolein from the step (g) and a second portion of the gas stream comprising acrolein from the step (b) with methyl mercaptan (6) in a mixture comprising at least one of 3-methylmercaptopropionaldehyde or a hemithioacetal of methyl mercaptan and 3-methylmercaptopropionaldehyde to obtain the 3-methylmercaptopropionaldehyde. An independent claim is also included for a process (P2) for producing 3-methylmercaptopropionaldehyde, comprising: (a1) oxidizing a mixture of propylene and inert diluent gases with air over a heterogeneous catalyst in two streams to obtain a first and a second gaseous oxidation reaction mixtures comprising acrolein and byproducts; (b1) quenching the first gaseous oxidation reaction mixture to obtain a gas stream comprising acrolein and a quench liquid comprising residual acrole