A carbonylation process for producing acetic acid including: (a) carbonylating methanol or its reactive derivatives in the presence of a Group VIII metal catalyst and methyl iodide promoter to produce a liquid reaction mixture including acetic acid, water, methyl acetate and methyl iodide; (b) feeding the liquid reaction mixture at a feed temperature to a flash vessel which is maintained at a reduced pressure; (c) heating the flash vessel while concurrently flashing the reaction mixture to produce a crude product vapor stream, wherein the reaction mixture is selected and the flow rate of the reaction mixture fed to the flash vessel as well as the amount of heat supplied to the flash vessel is controlled such that the temperature of the crude product vapor stream is maintained at a temperature less than 90 F. cooler than the feed temperature of the liquid reaction mixture to the flasher and the concentration of acetic acid in the crude product vapor stream is greater than 70% by weight of the crude product vapor stream.

There are provided a dividing wall distillation column for producing high-purity acrylic acid, and a fractional distillation method using the same. The dividing wall distillation column includes a condenser, a reboiler and a main column having a dividing wall. Here, the main column is divided into a column-top zone, an upper feed zone, an upper outflow zone, a lower feed zone, a lower outflow zone and a column-bottom zone. Also, a crude acrylic acid raw material (F) flows in a middle inflow plate NR1 in which the upper feed zone and the lower teed zone come in contact with each other, a low boiling point component (D) flows out from the column-top zone, a high boiling point component (B) flows out from the column-bottom zone, and a middle boiling point component (S) flows out through a middle outflow plate NR2 in which the upper outflow zone and the lower outflow zone come in contact with each other. In this case, the middle boiling point component is acrylic acid. Accordingly, since one distillation column can be used to realize the same effect as that obtained from the use of two distillation columns, the dividing wall distillation column can have an effect of reducing the costs of equipment to produce high-purity acrylic acid, as well as an energy-reducing effect, compared to a conventional process system.

A method for preparing (meth)acrylic acid, including: contacting a mixed gas containing (meth)acrylic acid with water in an absorption column to obtain a (meth)acrylic acid aqueous solution; crystallizing the (meth)acrylic acid aqueous solution in a crystallizer to obtain purified (meth)acrylic acid and a mother liquor; supplying a part of the mother liquor to an extraction column; contacting the mother liquor with an extraction solvent in the extraction column to obtain a raffinate and an extract, and then supplying an extract stream including the extract to a water separation column; separating, in the water separation column, into a water separation column upper discharge stream and a water separation column lower discharge stream; and supplying the water separation column lower discharge stream to a high-boiling-point by-product separation column, and supplying an upper discharge stream of the high-boiling-point by-product separation column containing (meth)acrylic acid to the crystallizer.

A method for preparing (meth)acrylic acid, including: bringing a mixed gas including (meth)acrylic acid into contact with water in an absorption column to obtain first and second aqueous (meth)acrylic acid solutions; discharging the first aqueous (meth)acrylic acid solution from a lower portion of the absorption column and supplying the solution to a crystallizer, and discharging the second aqueous (meth)acrylic acid solution from a side portion of the absorption column; supplying the second aqueous (meth)acrylic acid solution to a water separation column to obtain a distillate; supplying the distillate to a high-boiling-point by-product separation column, and supplying an upper discharge stream from the high-boiling-point by-product separation column to the crystallizer; and obtaining purified (meth)acrylic acid in the crystallizer, and circulating a part of mother liquor recovered in the crystallizer to the absorption column and the remainder to the water separation column.

Process for the recovery of carboxylic acid, in particular acetic acid containing carboxylic anhydride in particularacetic anhydride and other impurities, which comprises: (a) treating a fraction, in particular a fraction originating from a wood treatment process, containing carboxylic acid and impurities with a metal salt in the presence of water, (b) treating at least part of the fraction obtained from step (a) to remove metal salt and, (c) treating at least part of the fraction obtained from step (b) by distillation, stripping or membrane separation to recover at least a purified carboxylic acid fraction.

A process for producing acetic acid comprising the steps of carbonylating methanol in a reaction medium to form a crude acetic acid product; conveying the crude acetic acid product to a flash vessel at a flash flow rate; flashing the crude acetic acid product to form a first vapor stream comprising acetic acid and a liquid residue stream comprising metal catalyst and halide salt; separating the flashed vapor stream to form a second vapor stream comprising methyl iodide a sidedraw comprising purified acetic acid and water, and a liquid residue stream. The process further comprises the steps of condensing at least a portion of the second vapor stream to form at least one liquid phase and refluxing to the light ends column at least a portion of the at least one liquid phase at a reflux rate. The reflux rate is adjusted based on changes in the flash flow rate.

Process for the recovery of carboxylic acid, in particular acetic acid containing carboxylic anhydride in particular acetic anhydride and other impurities, which comprises: (a) treating a fraction, in particular a fraction originating from a wood treatment process, containing carboxylic acid and impurities with a metal salt in the presence of water, (b) treating at least part of the fraction obtained from step (a) to remove metal salt and, (c) treating at least part of the fraction obtained from step (b) by distillation, stripping or membrane separation to recover at least a purified carboxylic acid fraction.

The present invention relates to a process for producing a mixture that is insoluble in water of a homologous series of a number of various long-chain (C.sub.8) alkyl dicarboxylic acids, more particularly ,-n-alkyl dicarboxylic acids, by oxidative degradation of polyethylene (PE)-containing mixtures with oxygen, and to the mixtures or compositions obtainable therefrom and to their uses.

Process for producing acetic acid are disclosed in which a vapor sidedraw is withdrawn from the second column in the primary purification train. The vapor sidedraw comprises acetic acid and lithium-containing compounds at a concentration of no more than 100 wppb. A bottoms stream that is enriched in lithium-containing compounds, such as lithium acetate, or lithium acetate dihydrate, is also withdrawn from the second column. Advantageously, the vapor sidedraw, or a condensed portion thereof, is directly fed to a metal-exchanged ion exchange resin having acid cation exchange sites to produce purified acetic acid. This prevents displacement of the metals in the ion exchange resin.

Provided is a process for treatment of at least one wastewater stream from an acrylic acid and/or acrylate production plant. The process for treatment comprises the steps of: (a) introducing the least one wastewater stream from the acrylic acid and/or acrylate production plant into a bioreactor (510), (b) reacting the at least one wastewater stream in the bioreactor (510) under conditions of anaerobic microbiological decomposition of undesired organic components in the presence of at least one microorganism suitable for decomposition of undesired organic components to afford methane and carbon dioxide, (c) discharging from the bioreactor (510) a treated wastewater stream depleted in undesired organic components relative to the at least one wastewater stream introduced into the bioreactor (510), and (d) incinerating a methane-and carbon dioxide-containing product gas stream discharged from the bioreactor (510), in the incineration plant (512) with an incineration air stream and an optional auxiliary fuel stream.