Patent US3720647A successfully refreshed from Google Patents.
US3720647A
Expired / Lapsed
US
⏱️ 0.0 years remaining
PRODUCING p-XYLENE
Assignee: Fried Krupp AG
•
Filing: 1970-07-08
•
Granted: 1973-03-13
•
Expires: 1990-07-08
Abstract
Abstract P-Xylene having a purity of more than 99 percent, preferably more than 99.5 percent by weight is produced from a liquid hydrocarbon mixture (containing approximately 15 to 25 percent by weight p-xylene and, in addition, at least one further isomeric xylene) by crystallization above the eutectic point, subsequent filtration and subsequent centrifuging.
Inventors
- 👤 H Gelbe
- 👤 K Schmid
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 21:49
CPC Classifications
C; C07; C07C; C07C7/00; C07C7/14; Y; Y10; Y10S; Y10S585/00; Y10S585/919; Y10S585/921
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
116 words
A process for obtaining p-xylene with a purity in excess of 99 percent by weight from a flowable hydrocarbon mixture containing a plurality of xylenes and comprising from about 15 to about 25 percent by weight of p-xylene by a) crystallizing the hydrocarbon mixture above its eutectic point, b) filtering the crystallized product to obtain filter cake, c) passing inert medium through the filter cake while filtering to remove mother liquor from the filter cake and to form enlarged units of p-xylene crystals, d) transmitting the resulting filter cake with the enlarged units of p-xylene crystals to a centrifuge and e) centrifuging said resulting filter cake with said enlarged units of p-xylene crystals in the centrifuge.
Claim 2
Dependent Claim
116 words
A process for obtaining p-xylene with a purity in excess of 99 percent by weight from a flowable hydrocarbon mixture containing a plurality of xylenes and comprising from about 15 to about 25 percent by weight of p-xylene by a) crystallizing the hydrocarbon mixture above its eutectic point, b) filtering the crystallized product to obtain filter cake, c) passing inert medium through the filter cake while filtering to remove mother liquor from the filter cake and to form enlarged units of p-xylene crystals, d) transmitting the resulting filter cake with the enlarged units of p-xylene crystals to a centrifuge and e) centrifuging said resulting filter cake with said enlarged units of p-xylene crystals in the centrifuge.
Claim 3
Dependent Claim
155 words
A process according to claim 1 for obtaining p-xylene with a purity in excess of 99 percent by weight from a liquid hydrocarbon mixture containing a plurality of xylenes and comprising from about 15 to about 25 percent by weight of p-xylenes by a) crystallizing the hydrocarbon mixture above its eutectic point, b) filtering the crystallized product to obtain filter cake, c) passing inert medium through the filter cake while filtering to remove mother liquor from said filter cake and to enhance crystal growth of crystalline p-xyLene in said filter cake and thus increase the size of crystal units formed d) mechanically compressing crystalline p-xylene in the filter cake to agglomerate p-xylene crystals into larger crystal units, e) transmitting the resulting filter cake with the larger crystal units to a centrifuge and f) centrifuging said resulting filter cake with said larger crystal units in the centrifuge without any further intermediate treatment for enhancing crystal growth.
Claim 4
Dependent Claim
32 words
A process according to claim 1 wherein the thus enlarged units of p-xylene crystals in the filter cake are transmitted to the centrifuge without any further intermediate treatment for enhancing crystal growth.
Claim 5
Dependent Claim
24 words
A process according to claim 1 wherein the p-xylene filter cake crystals are transmitted into the centrifuge in the form of a flowable suspension.
Claim 6
Dependent Claim
22 words
A process according to claim 4 wherein the flowable suspension comprises a suspension medium consisting essentially of a mixture of xylene isomers.
Claim 7
Dependent Claim
19 words
A process according to claim 4 wherein mother liquor extracted during centrifuging is suspension medium for the flowable suspension.
Claim 8
Dependent Claim
28 words
A process according to claim 1 wherein the thus-enlarged units of p-xylene crystals in the filter cake are mechanically compressed to enhance the formation of even larger units.
Claim 9
Dependent Claim
14 words
A process according to claim 7 wherein the mechanical compression is effected with rollers.
Claim 10
Dependent Claim
21 words
A process according to claim 1 wherein solids retained in the centrifuge are rinsed during centrifuging with highly concentrated liquid p-xylene.
Claim 11
Dependent Claim
19 words
A process according to claim 2 for obtaining p-xylene with a purity in excess of 99.5 percent by weight.
References Cited (Backward Citations)
US2695323A
Cited
US2614134A
Cited
US2780663A
Cited
US2795635A
Cited
US3038789A
Cited
US3177265A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-03-12 | 1976-09-11 | 1977-03-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-03-12 | 1980-09-11 | 1981-03-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-03-12 | 1984-09-11 | 1985-03-13 | $7700.00 | Window Closed / Lapsed |