Purification of phenols
Publication Date: 2004-Mar-12
The IP.com Prior Art Database
Callie v Biljon: ATTORNEY [+5]
ZA 2003/2619: PATAPP [+3]
A process for purifying phenols in a feedstock containing phenols, neutral oils and/or tar bases comprising the steps of i) subjecting the feedstock to liquid-liquid extraction using a solvent in the form of a mixture of water and a solvent compound to transfer the phenols into a solvent layer, and using a counter-solvent to transfer the neutral oils and/or tar bases into a counter-solvent layer; ii) separating the solvent and counter-solvent layers, which separated solvent layer contains some counter-solvent; iii) subjecting the separated solvent layer of step (ii) to distillation at or above atmospheric pressure to yield a mixture comprising recovered water and counter-solvent as an overheads product and a mixture comprising the solvent compound and phenols as a bottoms product; and iv) recovering phenols from the bottoms product of step iii) to yield a purified phenols product.
This invention relates to the purification of phenols in a feedstock containing phenols and neutral oils and/or tar bases.
Feedstocks containing mixtures of phenols (such as phenol, cresols, ethylphenols, xylenols and C3 phenols) and neutral oils and/or tar bases are obtained from various sources such as petroleum and coal processing facilities.
The separation of phenols from tar bases and especially, neutral oils have always posed a challenge since certain neutral oils have boiling points close to that of the phenols and due to the fact that azeotropes are formed between the neutral oils and phenols. Normal distillation processes are accordingly not suitable to separate phenols from neutral oils and/or tar bases to the required purity.
Liquid-liquid extraction is a known method of separating phenols from neutral oils and/or tar bases. The prior art discloses that both single solvent and dual solvent processes have been employed to achieve such a separation. Dual solvent processes are preferred. In these processes a solvent is used to extract the phenols and a counter-solvent is used to extract the neutral oils. The solvent and counter-solvent are selected to be immiscible and after extraction the solvent and counter-solvent layers are separated and the phenols are recovered from the solvent layer while the neutral oils are recovered from the counter-solvent layer.
The solvent usually is a polar solvent and the counter-solvent usually is a non-polar solvent. The counter-solvent often comprises paraffins such as hexane, heptane, petroleum ether, octane and diesel. The polar solvent often comprises an aqueous solution of methanol, ammonia, acetamide, acetic acid, ethanol and glycols. In this regard see for example US Patent 2,666,796 where aqueous methanol and hexane were used as solvent and counter-solvent respectively. In the Journal of Applied Chemistry, 21 June 1952, page 314, and the Journal of Applied Chemistry, 3, March, 1953, page 98, aqueous triethylene glycol was used as solvent. In Fuel processing Technology, 28 (1991) page 287 aqueous solutions of ethylene glycol, diethylene glycol and triethylene glycol were used as solvents. In South African patents 98/11312 and 2001/9287 aqueous solutions of glycols were used as solvents and they were used in combination with counter-solvents.
In cases where the solvent comprises a mixture of water and a solvent compound (e.g. glycols) a solvent layer is obtained which contains the water, the solvent compound (e.g. glycols), phenols, some neutral oils and/or tar bases and some counter-solvent. The first step is usually to subject the mixture to a water recovery distillation process to strip the water from this mixture. The bottoms product consists mainly of the solvent compound (e.g. glycols) and phenols, which bottoms product is then subjected to distillation to separate the phenols from the glycols.
In South African patent 2001/9287 the solvent comprised a mixture...