Improved process for producing high-purity butyl acrylate

A process for the manufacture of butyl acrylate by direct esterification of acrylic acid with butanol in the presence of sulfuric acid as catalyst and of at least one polymerization inhibitor, resulting in a crude reaction mixture being obtained which contains butyl acrylate, residual acrylic acid, residual butanol, butyl hydrogen sulfate, traces of sulfuric acid and impurities resulting from side reactions, said process comprising steps of neutralization and of washing with water the crude reaction mixture resulting in a reaction mixture being obtained which is devoid of acidic impurities, characterized in that said reaction mixture washed of acidic impurities is subjected to the following steps:

• a) a topping step in a first distillation column, known as a topping column to obtain:
• a top stream from the topping column composed essentially of unreacted reactants;
• and
• a bottom stream from the topping column comprising a desired ester and heavy byproducts;
• b) a step of rectification by tailing said bottom stream from the topping column in a second distillation column, known as a rectification column, to separate:
• a top stream from the rectification column containing a purified desired ester;
• and
• a bottom stream from the rectification column containing heavy byproducts;
• c) a step of concentrating said bottom stream from the rectification column in an evaporator, resulting in a top stream from the evaporator, and further cooling the top stream from the evaporator in two steps, in order to recycle, to the rectification column, light compounds and to concentrate Michael adducts;
• d) a step of cracking said concentrate of Michael adducts in a thermal cracker to obtain:
• as a top stream from the thermal cracker, noble products resulting from the cracking which are recycled to the topping column;
• a bottom stream from the thermal cracker, a final residue,
• e) a step of hydrothermal treatment of said final residue, in the presence of water, carried out in an item of hydrothermal gasification equipment, resulting in gas of methane, hydrogen and CO2 type being obtained at a top of the item of hydrothermal gasification equipment and in solid residues and water being obtained at a bottom of the item of hydrothermal gasification equipment.