US 4,378,984 AGranted

Distillative freezing process for separating volatile mixtures

OwnerChen-Yen Cheng, Sing-Wang Chenginventors

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Abstract

The distillative freezing process disclosed is useful in separating a mixture containing at least two volatile components, denoted respectively as A-component and B-component, by simultaneously vaporizing the two components from the mixture under a sufficiently reduced pressure to simultaneously crystallize B-component. The vapor mixture obtained is brought to a condensed state either by a simple condensation operation or a condensation-desublimation operation without being substantially pressurized. The process may be continued to completely eliminate the liquid phase and bring the mixture into the two phase solid-vapor region. Then, the solid phase is no longer contaminated by the adhering liquid phase and gives a high purity B-component on melting. The process is particularly useful in separating mixtures containing close boiling components, such as styrene-ethyl benzene mixtures, p-xylene-m-xylene mixtures and ethylene-ethane mixtures. The process can therefore be used in producing high purity monomers for the plastic industries and high purity chemicals for other industries.

Claims17

Dependent claims

A crystallization separation process for separating a multicomponent mixture that is at least partly in a liquid state and includes at least two key volatile components, denoted respectively as A-component and B-component, into a B-enriched portion and a B-lean portion through formation of a B-enriched solid mass, wherein the two components form a binary system

(a) whose characteristic vapor pressure ratio defined as the ratio of the vapor pressure of A-component to that of B-component both evaluated at the triple point temperature of B-component is in the range of 0.1 to 10 and is less than the ratio of the heat of sublimation to the heat of melting of B-component evaluated at the triple point temperature of B-component, and
(b) whose constant pressure phase diagram that includes a three phase (B-enriched solid, liquid and vapor) state has a two phase (B-enriched solid and vapor) region covering a substantial concentration range above the temperature of the three phase state and a two phase (B-enriched solid and liquid) region below the temperature of the three phase state,
that comprises a first step of forming a first vapor mixture and a first condensed mass that comprises a mother liquor and a solid phase mass enriched in B-component by concurrently vaporizing the two components from the mixture in a first zone under a first temperature and a first pressure that are respectively lower than the triple point temperature and the triple point pressure of the pure B-component.

Dependencies are inferred from the claim text.

Facts

Application: 06/296,130Filed 25 Aug 1981 · continuation in part
Priority: 13 Apr 1976
Granted: 5 Apr 1983
Term ends: Not estimatedThe source records don’t support an estimate.

Classification3 codes

B01D 7/02
Sublimation: crystallisation directly from the vapour phase
B01D 9/04
From solutions: concentrating solutions by removing frozen solvent therefrom
B01D
Separation

Family

Serial676,640Parent of this continuation-in-part · filed 13 Apr 1976
Serial816,852Parent of this continuation-in-part · filed 18 Jul 1977
Serial930,312Parent of this continuation-in-part · filed 2 Aug 1978
Serial181,002Parent of this continuation-in-part · filed 22 Aug 1980
US 4,218,893 AParent of this continuation-in-part
US 4,378,984 AThis patent

From the US filing history. Foreign family members aren’t listed.