Crystallized hydroquinone and methods of making
AssigneeEastman Chemical Company
InventorsVenkateswarlu Bhamidi, Kyle Irion, Michael Joseph Stoltz, Richard S. Lott
Life of this patent
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Abstract
Crystallized hydroquinone particles and methods for making the same are provided. Cooling profiles applied during crystallization of the hydroquinone from solution may be optimized to provide crystallized particles having suitable properties and that exhibit reduced agglomeration tendencies, even after long periods of time and/or transportation over long distances.
Claims66
A process for producing crystallized hydroquinone, said process comprising:
- (a) providing a hydroquinone-containing solution having an initial temperature, T1;
- (b) cooling said solution from T1 to a first intermediate temperature, T2, to thereby provide a cooled solution, wherein said cooling is performed at a first average cooling rate, rC1;
- (c) further cooling said cooled solution from T2 to a second intermediate temperature, T3, to thereby provide a further cooled solution, wherein said further cooling is performed at a second average cooling rate, rC2, wherein rC2 is less than rC1;
- and
- (d) subsequent to said further cooling, crystallizing some of the hydroquinone in at least a portion of said further cooled solution to thereby provide crystallized hydroquinone.
A process for producing crystallized hydroquinone, said process comprising:
- (a) cooling a hydroquinone-containing solution in a crystallization zone to form crystallized hydroquinone;
- (b) during at least a portion of said cooling of step (a), measuring the value of at least one direct crystallization parameter in said crystallization zone to thereby provide a measured value;
- (c) comparing said measured value of said crystallization parameter to a threshold value for that crystallization parameter to determine a difference;
- (d) based on said difference, adjusting said cooling of step (a) to thereby cause at least a portion of said hydroquinone to crystallize out of said solution.
A process for producing a plurality of hydroquinone particles, said process comprising:
- (a) crystallizing a hydroquinone-containing solution in a crystallization zone to thereby provide a crystallization fluid and a plurality of crystallized particles;
- (b) separating at least a portion of said crystallization fluid from said crystallized particles in a separation zone to thereby provide separated hydroquinone crystals;
- (c) drying at least a portion of said separated hydroquinone crystals in a drying zone to thereby provide dried crystalline particles;
- (d) cooling at least a portion of said dried crystalline particles in a cooling zone to thereby provide a plurality of cooled particles, wherein at least 50 volume percent of said cooled particles have a temperature of less than 80° C.;
- and
- (e) transporting at least a portion of said cooled particles into a loading zone and loading said cooled particles into at least one storage container.
A process for producing crystallized hydroquinone, said process comprising:
- (a) cooling a hydroquinone-containing slurry from a first crystallization temperature, TC1, to a second crystallization temperature, TC2, in a crystallization zone;
- (b) maintaining the temperature of said hydroquinone-containing slurry within about 5° C. of TC2 for a crystallization hold period, wherein TC2 is less than 60° C.;
- and
- (c) subsequent to said crystallization hold period, further cooling said hydroquinone-containing slurry from a third crystallization temperature, TC3, to a final crystallization temperature, TCF, in said crystallization zone.
A process for producing crystallized hydroquinone, said process comprising:
- (a) cooling a hydroquinone-containing solution from an initial temperature, T1, to a crystallization temperature, TC, in a crystallization zone;
- (b) crystallizing at least a portion of said hydroquinone in said solution to provide a crystallized hydroquinone slurry, wherein at least a portion of said crystallizing includes maintaining the temperature of the crystallization zone within about 5° C. of TC;
- (c) subsequent to said crystallizing, further cooling said crystallized hydroquinone slurry to a final temperature, TCF, over a period of time, Δt, wherein the temperature of said crystallized hydroquinone slurry at a time, t, after initiation of said further cooling of step (c) is within 5° C. of a predicted temperature, Tp, provided by the following equation:
- Tp=TC+λt3,
- wherein the crystallization coefficient, λ, is defined by the following equation:
- λ
- =
- (
- T
- CF
- -
- T
- C
- Δ
-
-
- t
- 3
- )
- .
A composition comprising at least 5 kg of crystallized hydroquinone particles, wherein a representative sample of particles from said composition has a volume-averaged particle size distribution having a Dv50 of at least 285 microns and a span of at least 2.05.
A composition comprising at least 5 kg of crystallized hydroquinone particles, wherein a representative sample of particles from said composition has a volume-averaged particle size distribution having a Dv50 of at least 285 microns, wherein said representative sample has a number-averaged aspect ratio distribution having a median aspect ratio (A50) of at least 3:1 and/or a number-averaged length distribution having a median particle size (L50) of at least 250 microns.
Dependencies are inferred from the claim text.