Beads of a phenolic compound and a method of obtaining same
View Patent ↗The present invention relates to a novel presentation of a phenolic compound in the solid form. More particularly, the invention provides beads of hydroquinone. The invention also pertains to the preparation of said beads. The process of the invention is characterized in that a hot concentrated aqueous solution of a phenolic compound is prepared, then the solution is fragmented into droplets and the droplets obtained are cooled in a gas stream so that they solidify into beads which are then recovered and dried.
1. Beads of a phenolic compound having a high hot solubility of at least 500 g/l at a reference temperature of 90° C., and a difference of solubility which is at least doubled between its hot solubility in a first operational temperature in a fragmentation apparatus and cold solubility in a second operational temperature in a cooling gas stream, said beads being both attrition resistant and porous.
2. The beads according to claim 1 , wherein the phenolic compound has a high hot solubility of at least 1000 g/l at a reference temperature of 90° C.
3. The beads according to claim 2 , wherein the difference of solubility is a multiple of at least 3 to 5 times between said two operational temperatures.
4. The beads according to claim 1 , wherein the phenolic compound has the following formula (I):
wherein:
R 1 represents a hydroxyl group, an amino group, an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms.
5. The beads according to claim 4 , wherein the phenolic compound is selected from hydroquinone, pyrocatechin, resorcin or m-aminophenol.
6. The beads according to claim 1 , having a particle size of between 100 μm and 3000 μm.
7. The beads according to claim 1 , having a size, expressed as the median diameter (d 50 ), of from 300 μm to 2000 μm.
8. The beads according to claim 1 , having an attrition resistance of between 90% and 100.
9. The beads according to claim 1 , having an internal porosity, determined using a mercury porosimeter, of between 0.5 and 0.75, and having a bulk density (loose) of at least 0.3.
10. The beads according to claim 5 , having a degree of compressibility of 5% to 10%.
11. The beads according to claim 5 , having an attrition resistance of more than 98%.
12. The beads according to claim 5 , wherein having an internal porosity, determined using a mercury porosimeter, of between 0.5 and 0.75 cm 3 /g.
13. A process for preparing the beads defined in claim 1 , comprising the steps of:
a) preparing a hot concentrated aqueous solution of a phenolic compound, then,
b) fragmenting the solution into droplets and cooling the droplets obtained in a stream of gas so that they solidify into beads, and, then,
c) the beads obtained in step b) are recovered and dried.
14. The process according to claim 13 , wherein step b) consists of passing the phenolic acid solution through a nozzle to form droplets, solidifying the latter by allowing them to fall in a tower with a counter-current of a cold gas, in order to obtain the beads.
15. The process according to claim 14 , wherein step a) consists of preparing the aqueous solution of a phenolic compound at a concentration of at least 500 g/l.
16. The process according to claim 15 , wherein the aqueous solution of step a) is at a temperature of between 80° C. and 98° C.
17. The process according to claim 14 , wherein in step b), the nozzle is a single-hole nozzle or a multi-hole nozzle having between 1 and 3000 holes.
18. The process according to claim 14 , wherein in step b), the nozzle has perforations whose diameter is between 50 and 2000 μm.
19. The process according to claim 17 , wherein the nozzle is a static nozzle, preferably a nozzle which is subjected to a high frequency electrical vibration system, at 100 to 10000 hertz.
20. The process according to claim 13 , wherein in step b), the gas is nitrogen or oxygen-depleted air whose temperature is between −30° C. and 30° C.
21. The process according to claim 14 , wherein the droplet has a residence time for the nozzle outlet to its arrival of between 1 and 10 seconds.
22. The process according to claim 13 , wherein in step c), the beads are being recovered using a fluidized bed technique.
23. The process according to claim 13 , wherein in step b) the beads are formed in a prilling tower and the beads of phenolic compound at the bottom of the prilling tower is:
10% to 50% by weight of water; and
50% to 90% by weight of phenolic compound.
24. The process according to claim 23 , wherein the phenolic compound is hydroquinone and the composition at the bottom of the prilling tower is:
25% to 50% by weight of water;
50% to 75% by weight of phenolic compound.
25. The process according to claim 13 , wherein in step c), the beads are subjected to a stream of air the temperature of which is in the range 20° C. to 90° C., optionally in the range 60° C. to 90° C.
26. The process according to claim 25 , wherein drying is carried out using a fluidized bed technique.
27. The process according to claim 26 , wherein the beads of phenolic compound after drying is as follows:
0.1% to 1% by weight of water; and
99% to 99.9% by weight of phenolic compound.
28. The process according to claim 27 , in which the composition of the beads of phenolic compound after drying is as follows:
0.1% to 0.6% by weight of water;
99.4% to 99.9% by weight of phenolic compound.
29. The beads according to claim 1 , wherein the phenolic compound has a high hot solubility of less than 15000 g/l.
30. The beads according to claim 6 , having a particle size of between 500 μm and 1500 μm.
31. The beads according to claim 7 , having a size, expressed as the median diameter (d 50 ), of from 500 μm to 1500 μm.
32. The beads according to claim 8 , having an attrition resistance of more than 98%.
33. The beads according to claim 9 , having a bulk density (loose) of between 0.4 and 0.5.
34. The beads according to claim 11 , having an attrition resistance of between 90% and 100%.
35. The process according to claim 15 , wherein step a) consists of preparing the aqueous solution of a phenolic compound at a concentration of at least 1000 g/l.
36. The process according to claim 16 , wherein the aqueous solution of step a) is at a temperature of between 85° C. and 95° C.
37. The process according to claim 17 , wherein in step b), the nozzle is a single-hole nozzle or a multi-hole nozzle having between 1 and 100 holes.
38. The process according to claim 18 , wherein in step b), the nozzle has perforations whose diameter is between 200 and 600 μm.
39. The process according to claim 20 , wherein in step b), the gas is nitrogen or oxygen-depleted air whose temperature is between −10° C. and 10° C.
40. The process according to claim 21 , wherein the droplet has a residence time for the nozzle outlet to its arrival of between 3 and 5 seconds.
41. The beads according to claim 29 , wherein the phenolic compound is hydroquinone.