Patent ID: 9353040
Filing Date: 2016-05-31
CPC Classification: B01D,C07C

Claim Text:
1. A method for preparing a product mixture from an isobutene-containing hydrocarbon stream and for separating the resulting product mixture, said method comprising: a) hydroformylating an isobutene-containing hydrocarbon stream in a hydroformylation reactor in the presence of a transition metal complex catalyst, thereby obtaining a product mixture comprising 3-methylbutanal, conversion products in the form of high boilers, 3-methylbutanoic acid, the transition metal complex catalyst, and the free ligands thereof, b) separating the product mixture with a nanofiltration device comprising one or more membrane separation stages, such that the transition metal complex catalyst and the free ligands thereof are enriched in the resulting retentate of the nanofiltration device with respect to 3-methylbutanal and 3-methylbutanoic acid, and such that 3-methylbutanal and 3-methylbutanoic acid are each enriched in the resulting permeate of the nanofiltration device with respect to the transition metal complex catalyst, the concentration of the 3-methylbutanoic acid being lower in the resulting retentate than in the permeate, c) separating the resulting permeate of the nanofiltration device with a thermal separating device comprising one or more separation stages into at least one first fraction and a second fraction, wherein the first fraction has a higher concentration of 3-methylbutanal than the second fraction and a lower concentration of conversion products in the form of high boilers and 3-methylbutanoic acid than the second fraction, and d) recycling at least a substream of the resulting retentate of the nanofiltration device into the hydroformylation reactor, wherein: one or more nanofiltration membranes are used in the nanofiltration device; and the one or more membranes has a retention for 3-methylbutanoic acid of −1 or less.