Abstract: PROBLEM There is provided a melting method of (meth)acrylic acid crystal which is capable of providing a higher quality of (meth)acrylic acid without carrying out an additional purification treatment to (meth)acrylic acid obtained by a crystallization operation accompanied by melting of (meth)acrylic acid. In addition, there is provided a simple method for adjusting a content of polymerization inhibitor in a product (meth)acrylic acid. SOLUTION In the crystallization method melting (meth)acrylic acid crystal while wetting with the crystalline molten liquid, a polymerization inhibitor is added to a molten liquid melted after initiation of melting, and all of crystal is melted while circulating and feeding the molten liquid containing said polymerization inhibitor to the crystal.

Abstract: PROBLEM There is provided a melting method of (meth)acrylic acid crystal which is capable of providing a higher quality of (meth)acrylic acid without carrying out an additional purification treatment to (meth)acrylic acid obtained by a crystallization operation accompanied by melting of (meth)acrylic acid. In addition, there is provided a simple method for adjusting a content of polymerization inhibitor in a product (meth)acrylic acid. SOLUTION In the crystallization method melting (meth)acrylic acid crystal while wetting with the crystalline molten liquid, a polymerization inhibitor is added to a molten liquid melted after initiation of melting, and all of crystal is melted while circulating and feeding the molten liquid containing said polymerization inhibitor to the crystal.

Abstract: A method for producing acrylic acid by absorbing acrylic acid at a high ratio and obtaining an acrylic acid-containing solution of high concentration is provided. This method comprises a step of circulating part of a discharged gas from an absorption step of acrylic acid to the reactor and discarding the remainder to the out side of system while the gas is cooled before circulation to the reactor. By the method, the acrylic acid-containing solution of high concentration is obtained due to decrease of an acrylic acid loss.

Abstract: There are disclosed a catalyst and a process for production of acrylic acid using this catalyst, wherein, even under conditions where hot spots are formed, the catalyst is excellent in activity, selectivity, and catalyst life time and displays stable performances for a long time.

Abstract: A method for producing acrylic acid by absorbing acrylic acid at a high ratio and obtaining an acrylic acid-containing solution of high concentration is provided. This method comprises a step of circulating part of a discharged gas from an absorption step of acrylic acid to the reactor and discarding the remainder to the out side of system while the gas is cooled before circulation to the reactor. By the method, the acrylic acid-containing solution of high concentration is obtained due to decrease of an acrylic acid loss.

Abstract: A method for the production of acrylic acid comprises (i) a step for introducing a polymerization inhibitor to a stage other than a stage for supplying a raw material and a stage for supplying a reflux of said distilling column or (ii) a step for supplying the acrylic acid recovered by thermally decomposing said oligomer to said stage for dehydration. Thus, the present invention enjoys effective utilization of acrylic acid and exalts the efficiency of production.

Abstract: In the reaction of catalytic gas phase oxidation induced by the supply of at least a raw material to be oxidized and a molecular oxygen-containing gas to a reactor for catalytic gas phase oxidation, a method for starting up the reactor for catalytic gas phase oxidation is disclosed which is characterized by causing the raw material and the molecular oxygen-containing gas to pass a range in which the concentration of the raw material is less than the lower explosion limit of the raw material and the concentration of oxygen is not less than the limiting oxygen concentration, but excluding the concentration of the raw material of 0 vol. %. The method enables the reactor to be started up economically and safely by avoiding the explosion range induced by the composition of a raw material and a molecular oxygen-containing gas supplied to the reactor and decreasing the amount of a diluting gas to be supplied.

Abstract: A method for the production of acrylic acid of high concentration by absorbing acrylic acid with high absorption ratio of acrylic acid is provided. In a method for producing acrylic acid by a procedure comprising a step of catalytic gas phase oxidation reaction and a step of absorbing the acrylic acid-containing gas, while a low boiling substance-containing solution is introduced into the absorption column via a portion different from the top of the column.

Abstract: A method for producing acrylic acid by absorbing acrylic acid at a high ratio and obtaining an acrylic acid-containing solution of high concentration is provided. This method comprises a step of circulating part of a discharged gas from an absorption step of acrylic acid to the reactor and discarding the remainder to the out side of system while the gas is cooled before circulation to the reactor. By the method, the acrylic acid-containing solution of high concentration is obtained due to decrease of an acrylic acid loss.

Abstract: This invention is providing a method for efficient treatment of the waste material from a process for production of acrylic acid and an acrylic ester. This is a method for the disposal of waste material, which at least one waste material selected from the group consisting of waste oil, waste water, and waste gas emitted from a process for production of acrylic acid is/are purified with at least one waste material selected from the group consisting of waste oil, waste water, and waste gas emitted from a process for production of an acrylic ester jointly. The efficiency of the treatment is enhanced by simultaneously treating the waste material.

Abstract: A method for producing acrylic acid by using an acrylic acid-containing solution of high concentration without azeotropic distillation is provided. This method of producing acrylic acid comprises introducing an acrylic acid-containing gas obtained by catalytic gas phase oxidation reaction into an absorption column and supplying the acrylic acid-containing solution to crystallization step thereby separating the solution into acrylic acid and residual mother liquid, and distilling at least part of the residual mother liquid and circulating the distillate obtained by the distillation to the absorption column.

Abstract: A method for producing acrylic acid from an acrylic acid-containing solution of high concentration without performing azeotropic distillation is provided. This method of producing acrylic acid comprises steps of absorbing acrylic acid-containing gas, distilling the acrylic acid-containing solution without using an azeotropic solvent thereby obtaining crude acrylic acid as a column bottom stream and/or a column side stream, and supplying the crude acrylic acid to a crystallizing step and melt crystallizing the crude acrylic acid thereby obtaining purified acrylic acid.

Abstract: A method is disclosed which produces acrylic acid in a high yield as maintaining the conditions for purifying acrylic acid in constant ranges and preventing the acrylic acid from polymerization. By using single a single reactor, propylene concentration adjusting in the range of 7–15 vol. % and water concentration adjusting in the range of 0–10 vol. % are introduced thereinto thereby obtaining an acrylic acid-containing gas. Then the gas is introduced to an acrylic acid absorption column to adjust water concentration in the range of 1–45 wt. %, thereby preventing from polymerization.

Abstract: A method for managing the operation of an apparatus for the reaction of gas phase partial oxidation of an unsaturated hydrocarbon with a molecular oxygen-containing gas for the purpose of omitting wasteful emergency stop of the operation and ensuring execution of necessary emergency measure and a method for producing (meth) acrylic acid by utilizing the method mentioned above are provided. The operation of the apparatus is brought to emergency stop exclusively when thee values of concentrations of various gases obtained by calculation from the flow rates of the gases being introduced at the inlet port of the reactor and the measured values obtained by analysis with gas analyzing instruments both deviate from the ranges of the present values.

Abstract: A method is disclosed which produces acrylic acid in a high yield as maintaining the conditions for purifying acrylic acid in constant ranges and preventing the acrylic acid from polymerization. By using a reactor which has first reaction zone and second reaction zone formed of different reaction tubes, propylene concentration adjusting in the range of 7–15 vol. % and water concentration adjusting in the range of 0–10 vol. % are introduced thereto thereby obtaining an acrylic acid-containing gas. Then the gas is introduced to an acrylic acid absorption column to adjust water concentration in the range of 1–45 wt. %, thereby preventing from polymerization.

Abstract: This invention concerns a method for absorbing acrylic acid, characterized by supplying an acrylic acid-containing reaction gas component obtained by the reaction of catalytic gas phase oxidation to an acrylic acid absorption column and advancing a high boiling inert hydrophobic organic liquid into counter-flow contact with said reaction gas in said acrylic acid absorption column with the mass flow rate of the organic liquid fixed in the range of 0.2-7.0 times the mass flow rate of the acrylic acid in the reaction gas thereby absorbing acrylic acid in said organic liquid and obtaining an acrylic acid-containing solution including a low boiling substance in the range of 0.7-7.5 wt % based on the weight of bottom liquid of absorption column.

Abstract: In an apparatus provided with a plate type heat exchanger as a heater and/or a cooler and operated to treat a gas containing an easily blocking substance, a method for preventing the plate type heat exchanger from being blocked is disclosed which is characterized by i) setting the width of a flow path on a plate of the plate type heat exchanger in the apparatus in a range of 6-25 mm and ii) setting the average flow rate of the gas passing the plate type heat exchanger in the apparatus per unit cross-sectional area of the flow path on the plate in the range of 3-15 m/s. In the exchange of heat of an easily blocking substance by the use of a plate type heat exchanger, a method for preventing the plate type heat exchanger from blockage is disclosed which has the plate type heat exchanger provided in the port for introducing a gas containing an easily blocking substance with a gas dispersion plate.

Abstract: A method for the production of acrylic acid of high concentration by absorbing acrylic acid with high absorption ratio of acrylic acid is provided. In a method for producing acrylic acid by a procedure comprising a step of catalytic gas phase oxidation reaction and a step of absorbing the acrylic acid-containing gas, while a low boiling substance-containing solution is introduced into the absorption column via a portion different from the top of the column.

Abstract: A method for producing acrylic acid by absorbing acrylic acid at a high ratio and obtaining an acrylic acid-containing solution of high concentration is provided. This method comprises a step of circulating part of a discharged gas from an absorption step of acrylic acid to the reactor and discarding the remainder to the out side of system while the gas is cooled before circulation to the reactor. By the method, the acrylic acid-containing solution of high concentration is obtained due to decrease of an acrylic acid loss.

Abstract: A method for producing acrylic acid from an acrylic acid-containing solution of high concentration without performing azeotropic distillation is provided. This method of producing acrylic acid comprises steps of absorbing acrylic acid-containing gas, distilling the acrylic acid-containing solution without using an azeotropic solvent thereby obtaining crude acrylic acid as a column bottom stream and/or a column side stream, and supplying the crude acrylic acid to a crystallizing step and melt crystallizing the crude acrylic acid thereby obtaining purified acrylic acid.