FIELD: chemistry.
SUBSTANCE: invention relates to a method of processing by-products of synthesis of isoprene from isobutylene and formaldehyde or formaldehyde-containing products, particularly 4,4-dimethyl-1,3-dioxane, on an industrial aluminosilicate-containing catalyst K-84 or K-97 at temperature 400-480°C, with possible preliminary heating of the material to temperature 400-480°C, with dilution of the material with water vapour, characterised by that dilution of the material with water vapour is gradually increased with contacting, initially 3-15% lower than the average dilution value and at the end of contacting 3-15% higher than the dilution value, wherein when processing as a by-product a technical fraction of 4-methyl-5,6-dihydro-α-pyran, dilution with water vapour is carried out with weight ratio 4-methyl-5,6-dihydro-α-pyran: water vapour equal to 1:(0.7-2.4), respectively, and when processing high-boiling by-products or mixture thereof with a technical fraction of 4-methyl-5,6-dihydro-α-pyran, dilution with water vapour is carried out with weight ratio material: water vapour equal to 1:(2.5-7.0), respectively.
EFFECT: disclosed method increases selectivity of the process, increases conversion of material and heavy products and reduces coke deposit.
1 cl, 5 ex, 4 tbl
