A process for producing (meth)acrolein or (meth)acrylic acid by vapor phase catalytic oxidation of propylene, propane or isobutylene in an oxidation reactor, characterized in that the raw material mixed gas introduced to the oxidation reactor is adjusted to have a temperature higher than the dew point of the mixed gas. The process allows the prevention of the variation in the composition of the raw material mixed gas, the abnormal temperature elevation of the oxidation reactor, and the reduction of catalyst activity and catalyst life, which leads to the production of (meth)acrylic acid and a derivative thereof with stability and with good efficiency.

Process for producing (meth)acrylic acid

A method for producing a polyacrylic acid (salt)-based water absorbent resin, sequentially including the steps of: storing or producing acrylic acid; mixing acrylic acid containing a polymerization inhibitor with water, a crosslinking agent, and optionally, a basic composition, and/or neutralizing them, to prepare an aqueous monomer solution; polymerizing the aqueous monomer solution; drying an obtained water-containing gel-like crosslinked polymer; and optionally carrying out surface crosslinking, wherein the acrylic acid containing the polymerization inhibitor has a water content of not higher than 1,000 ppm (by mass; the same applies hereinafter), and/or the aqueous monomer solution has a formic acid content of 1 to 700 ppm, relative to the monomer.

Polyacrylic acid salt-based water absorbent resin and method for producing same

This invention relates to a process for preparing a low-odor hydrogel-forming acrylic acid polymer, which comprises the steps of: a) preparing a polymeric hydrogel by free-radically polymerizing a monomer composition comprising at least 50% by weight of acrylic acid in an aqueous polymerization medium and converting said hydrogel into a particulate hydrogel or into hydrogel-forming powder; and optionally b) treating said particulate hydrogel or said hydrogel-forming powder with a crosslinking substance which, actually or latently, contain at least two functional groups capable of reacting with the carboxyl groups on the addition polymer; characterized by the acrylic acid used in step a) containing less than 400 ppm of acetic acid and propionic acid. It further relates to the hydrogel-forming addition polymers obtainable by the process and to their use.

Method for producing low-odor hydrogel-forming polymers

It is an object of the present invention to provide a process for producing aliphatic carboxylic acid, which can stabilize operation of a distillation column upon production of aliphatic carboxylic acid by reducing a water content in an aqueous aliphatic carboxylic acid solution by a distillation column, and can shorten a time during the non-steady state such as at starting up of distillation column operation. The present invention is directed to a process for producing aliphatic carboxylic acid, which comprises an azeotropic distillation step of supplying an aqueous aliphatic carboxylic acid solution and an azeotropic solvent to an azeotropic distillation column to perform distillation, separating an azeotrope containing the azeotropic solvent and water as a distillate, and recovering aliphatic carboxylic acid with a reduced water content as bottom liquid, characterized in that a target value of an amount of the azeotropic solvent to be supplied is set depending on an amount of water in the aqueous aliphatic carboxylic acid solution supplied to the azeotropic distillation column, and the amount of the azeotropic solvent to be supplied is controlled at the target value.

Process for producing aliphatic carboxylic acid

The present invention provides a method for effectively preventing the precipitation related to manganese acetate in the pipe for sending a polymerization inhibitor and the like, and the polymerization of (meth)acrylic acid. A first method of the present invention for producing (meth)acrylic acid, characterized in comprising steps of: producing a (meth)acrylic acid-containing gas by catalytic vapor phase oxidation reaction; and obtaining a (meth)acrylic acid-containing fluid by providing the (meth)acrylic acid-containing gas into a condensation column or an absorption column; wherein manganese acetate is used as a polymerization inhibitor; manganese acetate is dissolved into a (meth)acrylic acid aqueous solution containing not more than 10% by mass of (meth)acrylic acid, and the like, to obtain a manganese acetate aqueous solution; and the manganese acetate aqueous solution is provided into the condensation column or the absorption column.

Method for producing (meth)acrylic acid

PURPOSE:To recover acrylic acid free of water and by-products, from crude acrylic acid aqueous solution obtained by the vapor phase catalytic oxidation of propylene, in high recovery, preventing polymerization of acrylic acid, by using a dehydration column and an acetic acid separation column, and distillating in the presence of a specific azeotropic agent. CONSTITUTION:An aqueous solution of crude acrylic acid obtained by the vapor phase catalytic oxidation of propylene and/or acrolein is introduced into a dehydration column E through a line 12, and distilled together with an azeotropic agent introduced to the column through the line 16. The azeotropic agent is a compound which forms azeotropic mixtures with both water and acetic acid, is hardly soluble in water, and does not form an azeotropic mixture with acrylic acid. Whole water and formic acid and a part of acetic acid in the aqueous solution is distilled out from the top of the column E, and acrylic acid containing residual acetic acid is extracted from the bottom of the column, introduced into an acetic acid separation column F through a line 14, and distilled together with the above azeotropic agent to distil off the whole acetic acid and a small amount of acrylic acid through the top of the column F. A part of the acrylic acid is recycled to the column F through the line 18, and the remainder is returned to the dehydration column E through the line 16. The purified acrylic acid is recovered from the bottom of the column F.

Purification of acrylic acid

PROBLEM TO BE SOLVED: To distill and purify crude (meth)acrylic acid while excellently inhibiting polymerization by adding a specific polymerization inhibitor and using acetic acid as a by product and an inexpensive copper compound when the crude (meth)acrylic acid obtained by vapor-phase catalytic oxidation of propylene, etc., is distilled and purified. SOLUTION: When crude (meth)acrylic acid containing water and acetic acid obtained by vapor-phase catalytic reaction of propylene or isobutene is distilled and purified, a mixture as a polymerization inhibitor of (A) an aqueous solution of acetic acid obtained by the distillation and purification process, (B) a copper compound which is copper carbonate or hydroxide and optionally (C) a polymerization inhibitor which is a phenol, an organometallic compound, an N-oxyl compound or an amine compound is added to the purification process.

Yada Shuhei

Papers

Purification of acrylic acid

Purification of (meth)acrylic acid