| 摘要 |
A METHOD AND APPARATUS FOR PURIFYING CRUDE TEREPHTHALIC ACID FROM A LIQUID DISPERSION THEREOF ALSO CONTAINING IMPURITIES SELECTED FROM UNREACTED STARTING MATERIALS, SOLVENTS, PRODUCTS OF SIDE REACTIONS AND/OR OTHER UNDERSIRED MATERIALS IS PROVIDED. THE METHOD COMPRISES THE STEPS OF FILTERING THE DISPERSION TO FORM A CRUDE TEREPHTHALIC ACID FILTER CAKE, DISSOLVING THE FILTER CAKE IN A SELECTIVE CRYSTALLIZATION SOLVENT AT AN ELEVATED TEMPERATURE TO FORM SOLUTION, CRYSTALLIZING PURIFIED TEREPHTHALIC ACID FROM THE SOLUTION IN THE CRYSTALLIZATION SOLVENT BY REDUCING THE PRESSURE AND TEMPERATURE OF THE SOLUTION, AND SEPARATING THE CRYSTALLIZED PURIFIED TEREPHTHALIC ACID FROM THE SOLUTION. ACCORDING TO THE INVENTION, THE SELECTION CRYSTALLIZATION SOLVENT IS NON-AQUEOUS, NON-CORROSIVE AND ESSENTIALLY NON-REACTIVE WITH TEREPHALIC ACID. PREFERABLY, THE SELECTIVE CTRYSTALLIZATION SOLVENT IS N-METHYL PYRROLIDONE OR DIMETHYL ACETAMIDE. THE METHOD AND APPPARATUS PRODUCES PURIFIED TEREPHTHALIC ACID HAVING A PURITY DESIRED FOR USE IN FORMING POLYESTER RESIN AND OTHER PRODUCTS AT AN ECONOMICALLY ATTRACTIVE RATE AND AT OPERATING CONDITIONS OF REDUCED SEVERITY WHICH REQUIRE A LOWER CAPITAL INVESTMENT AND SIMPLIFIED PROCESSING. (FIG 10).
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