SEPARATION OF 2,6 - DMN AND 2,7 - DMN EUTECTIC VIA TRANS 2,6-DIMETHYLDECALIN CRYSTALLIZATION

摘要

1,229,099. Dimethyl decalins; dimethyl naphthalenes. SUN OIL CO. 3 Nov., 1969 [29 Nov., 1968], No. 53733/69. Heading C5E. The 2,6-isomer is recovered from a feed comprising trans-syn-2-syn-6-dimethyl decalin (i.e. 2,6-DMD) and trans-syn-2-syn-7-dimethyl decalin (i.e. 2,7-DMD) by crystallization at a temperature in the range - 50‹ to 0‹ C., said temperature being the lowest at which the 2,6- DMD/2,7-DMD eutectic mixture is soluble in the liquid present, as determined from Fig. 3 (not shown). 2,6-Dimethyl naphthalene (i.e. 2,6-DMN) is recovered from a eutectic mixture of 2,6-DMN and 2,7-DMN, e.g. one produced from a 2,6- DMN crystallization mother liquor, by the following process sequence:- (a) Hydrogenating the 2,6-DMN/2,7-DMN eutectic mixture to form a 2,6-DMD/2,7-DMD mixture; (b) Crystallizing 2,6-DMD as described above; and (c) Dehydrogenating the 2,6-DMD to 2,6- DMN. This process may also include the further steps of:- (d) Recovering a 2,6-DMD/2,7-DMD eutectic mixture from the mother liquor in step (b); (e) Dehydrogenating this mixture to form a 2,6-DMN/2,7-DMN mixture; (f) Crystallizing 2,7-DMN from this mixture at a temperature in the range - 20‹ to + 70‹ C., said temperature being the lowest at which the 2,6-DMN/2,7-DMN eutectic mixture is soluble in the liquid present as determined from Fig. 1 (not shown); (g) Recovering a 2,6-DMN/2,7-DMN eutectic mixture from the mother liquor of (f); and (h) Recycling this eutectic mixture to step (a).