Liquid phthalic anhydride recovery process
AssigneeExxon Chemical Patents Inc.
InventorHerbert P. Dengler
Life of this patent
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Abstract
A process for separating phthalic anhydride from a vapor phase oxidation product by mixing and cooling the vapor phase oxidation product with recycled by-products which have freezing points lower than the freezing point of pure phthalic anhydride, thereby condensing and recovering a liquid phase phthalic anhydride product without the formation of an intermediate solid phase.
Claims26
A process for separating phthalic anhydride from a vapor phase oxidation product which comprises the steps of:
- (a) cooling said vapor phase oxidation product to a temperature of about 130.degree. C. to 165.degree. C.;
- (b) mixing and further cooling the vapor phase oxidation product of step (a) with at least one by-product stream having a freezing point which is lower than the freezing point of pure phthalic anhydride, thereby forming a liquid phase phthalic anhydride product having a freezing point lower than the freezing point of pure phthalic anhydride, and a first vapor stream;
- (c) separating said liquid phase phthalic anhydride product from said first vapor stream by means of a flash separator;
- (d) separating said liquid phase phthalic anhydride product into a crude phthalic anhydride stream and a first by-product stream;
- (e) cooling said first by-product stream to a temperature in the range between about 40.degree. C. to 80.degree. C.;
- (f) recycling at least a portion of said first by-product stream to said step (b);
- (g) cooling said first vapor stream to a temperature in the range between about 40.degree. C. to 80.degree. C., thereby forming a second by-product stream and a second vapor stream;
- (h) separating said second by-product stream from said second vapor stream by means of a flash separator;
- and
- (i) recycling at least a portion of said second by-product stream to said step (b).
A process for separating phthalic anhydride from a vapor phase oxidation product which comprises the steps of
- (a) cooling said vapor phase oxidation product to a temperature of about 130.degree. C. to 165.degree. C.;
- (b) mixing and further cooling the vapor phase oxidation product of step (a) with at least one by-product stream having a freezing point which is lower than the freezing point of pure phthalic anhydride, thereby forming a liquid phase phthalic anhydride product having a freezing point lower than the freezing point of pure phthalic anhydride and a first vapor stream;
- (c) separating said liquid phase phthalic anhydride product from said first vapor stream by means of a flash separator;
- (d) separating said liquid phase phthalic anhydride product into a crude phthalic anhydride stream and a first by-product stream;
- (e) cooling said first vapor stream to a temperature in the range between about 40.degree. C. to 80.degree. C., thereby forming a second by-product stream and a second vapor stream;
- (f) separating said second by-product stream and said second vapor stream by means of a flash separator;
- (g) recycling at least a portion of said second by-product stream to said step (b);
- (h) mixing said second vapor stream with an absorbent to form an absorbent containing by-product stream;
- (i) separating said absorbent containing by-product stream into a desorbed by-product stream and a concentrated absorbent stream;
- (j) mixing said desorbed by-product stream with said first by-product stream;
- (k) separating the mixture of step (j) into a fourth by-product stream and a purge stream comprising heavy by-products;
- and
- (l) recycling at least a portion of said fourth by-product stream to said step (b).
A process fix separating phthalic anhydride from a vapor phase oxidation product which comprises mixing said vapor phase oxidation product having a temperature in the range of about 130.degree. C. to 165.degree. C. with a liquid maleic anhydride by-product under flash separation conditions wherein a liquid phase phthalic anhydride product containing between about 80 to 90 mole % phthalic anhydride and having a freezing point lower than the freezing point of pure phthalic anhydride, wherein at least a portion of the maleic anhydride contained with said mixture of said vapor phase oxidation product and said liquid maleic anhydride by-product is recovered as a vapor.
A process for separating phthalic anhydride from a vapor phase oxidation product M-rich comprises:
- (a) mixing said vapor phase oxidation product having a temperature in the range of about 130.degree. C. to 165.degree. C. with a liquid maleic anhydride by-product under flash separation conditions wherein a liquid phase phthalic anhydride product containing between about 80 to 90 mole % phthalic anhydride and having a freezing point lower than the freezing point of pure phthalic anhydride, wherein at least a portion of the maleic anhydride contained within said mixture of said vapor phase oxidation product and said liquid maleic anhydride by-product is recovered as a first vapor phase stream;
- (b) separating at least a portion of said maleic anhydride by-product from said first vapor phase stream to form a maleic anhydride by-product stream and a second vapor phase stream;
- (c) mixing said second vapor phase stream with an absorbent, thereby forming a maleic/absorbent stream;
- and
- (d) desorbing said maleic/absorbent stream to form an enriched maleic anhydride stream and a concentrated absorbent stream.
Dependencies are inferred from the claim text.