Patent GB-754110-A (GB)
Title: Recovery of phenol from catalytic decomposition mixtures by distillation
Inventor: ARMSTRONG GODFREY PAUL
IPC: C07C37/74
Filed: 1952-07-05
Abstract: <PICT:0754110/IV(a)/1> In the recovery of pure phenol from mixtures derived from the catalytic decomposition of isopropylbenzene hydroperoxide by fractional distillation, the decomposition of phenyldimethyl carbinol also present in the mixture is prevented by retaining in the still-residue a proportion of phenol to phenyldimethyl carbinol which depends on the pressure at which the distillation is carried out and which would be not less than 5:1 when the pressure is about atmospheric and not less than 0.7:1 when the pressure is about 10 mm. mercury.  The presence of a -methylstyrene (i.e. the dehydration product of phenyldimethyl carbinol) in the phenol-distillate is thereby avoided.  The synthetic phenol mixture from which the catalyst and acetone have previously been removed is introduced into fractionating column 1 in which methylstyrene and any isopropylbenzene initially present in the mixture are distilled off whilst phenol together with higher boiling substances are withdrawn as residue and introduced into column 2.  The temperature and/or pressure in column 2 are adjusted so that phenol distils over; but enough phenol is retained in the still-residue (together with the higher boiling products) to prevent decomposition of the phenyldimethylcarbinol. The still-residue is taken to cracking zone 3, where it is subjected to a temperature of about 350 DEG  C.  The gaseous and liquid products from zone 3 are led into column 4 from the base of which tar is removed, while vapours containing isopropylbenzene, methylstyrene, phenol and acetophenone are passed on to column 5. Acetophenone containing some phenol is removed from the base of column 5.  The overhead vapours from column 5 are passed, together with those from column 2, into column 6, where isopropylbenzene and methylstyrene are removed overhead.  A side-stream from column 6, comprising phenol vapour containing traces of phenol-methylstyrene condensation products as well as polymerized methylstyrene, is taken to a small column 7 from which pure phenol is withdrawn as an overhead fraction.  The liquid residue from column 7 is united with that from column 6; and the mixture is returned to cracking zone 3.  Specifications 724,190 and 745,343 are referred to.ALSO:In the recovery of pure phenol from mixtures derived from the catalytic decomposition of isopropylbenzene hydroperoxide by fractional distillation the decomposition of phenyl dimethyl carbinol also present in the mixture is prevented by retaining in the still-residue a proportion of phenol to phenyl dimethyl carbinol which depends on the pressure at which the distillation is carried out and which would be not less than 5:1 when the pressure is about atmospheric and at not less than 0.7:1 when the pressure is about 10 m.m. mercury.  The presence of a -methylstyrene (i.e. the dehydration product of phenyldimethyl carbinol) in the phenol-distillate is thereby avoided.  The synthetic phenol mixture from which the catalyst and acetone have previously been removed is introduced into fractionating column 1 in which methylstyrene and any isopropylbenzene initially present in the mixture are distilled off whilst phenol together with higher boiling substances are withdrawn as residue and introduced into column 2.  The temperature and/or pressure in column 2 are adjusted so that phenol distils over; but enough phenol is retained in the still-residue (together with higher boiling products) to prevent decomposition of the phenyldimethyl carbinol.  The still-residue is taken to cracking zone 3, where it is subjected to a temperature of about 350 DEG C.  The gaseous and liquid products from zone 3 are led into column 4 from the base of which tar is removed, while vapours containing isopropylbenzene, methylstyrene, phenol and acetophenone are passed on to column 5. Acetophenone containing some phenol is removed from the base of column 5.  The overhead vapours from column 5 are passed, together with those from column 2, into column 6, where isopropylbenzene and methylstyrene are removed overhead.  A side-stream from column 6, comprising phenol vapour containing traces of phenolmethylstyrene condensation products as well as polymerized methylstyrene, is taken to a small column 7 from which pure phenol is withdrawn as an overhead fraction.  The liquid residue from column 7 is united with that from column 6; and the mixture is returned to cracking zone 3. Specifications 724,190 and 745,343 are referred to.