Abstract: A method for distilling (meth)acrylic acid and/or the ester thereof by withdrawing vapor generated in a distillation column by distillation from the top of the column, condensing the vapor to give a condensate, and circulating part of the condensate as reflux liquid into the distillation column from the top thereof, comprising the step of adding a polymerization inhibitor to said condensate and said reflux liquid. This method enables maintaining the purity and quality of (meth)acrylic acid and/or the ester thereof at a certain level or higher, suppressing generation of polymers in the rectification column and suppressing polymerization of the condensate obtained by distillation in the incident facilities of the column such as condenser, condensate tank, and the like. In addition, the method enables reduction in the amount of polymerization inhibitor used while suppressing polymerization in the intermediate distillation columns (except the final rectification column).

Abstract: Polymerizable compounds are prepared and/or worked up using at least one liquid ring pump by a process in which a working liquid which contains a material stream from the preparation and/or working-up of the polymerizable compound is used in a liquid ring pump.

Abstract: In a distillation apparatus, a production process and a purification method of readily polymerizable compounds, a problem of the invention is to solve a serious plugging problem in a large-sized distillation column as in the commercial equipment and to provide an apparatus and a method for distilling and purifying a readily polymerizable compound stably over a long period of time.

Abstract: Clogging of a distillation column by polymerization caused by a change of the production rate of (meth)acrylic acid, is prevented to carry out a stabilized operation over a long period. A process for producing (meth)acrylic acid, which includes a purification step wherein a (meth)acrylic acid-containing material to be purified is supplied to and distilled by a distillation column, wherein during a cut operation in which the production rate of (meth)acrylic acid is reduced by &agr;% relative to the production rate of (meth)acrylic acid during the ordinary operation, the liquid/gas flow rate in the distillation column is adjusted to be at least (100−&agr;/2)% of the liquid/gas flow rate during the ordinary operation.

Abstract: In a process for producing (meth)acrylic acid comprising contacting a reaction gas containing (meth)acrylic acid obtained by gas-phase catalytic oxidation with an absorbent solvent to prepare a (meth)acrylic acid solution; and introducing the (meth)acrylic acid solution into a distillation column to purify (meth)acrylic acid, after a dissolved oxygen concentration in the (meth)acrylic acid solution to be introduced into the distillation column is adjusted to not less than 12 ppm by weight, the (meth)acrylic acid solution is fed to the distillation column. In addition, upon an azeotropic dehydration distillation step, a phenol-based polymerization inhibitor is fed to an azeotropic dehydration distillation column from a position not lower than a raw material feed stage thereof, and a copper-based polymerization inhibitor is fed to the azeotropic dehydration distillation column from a position lower than the raw material feed stage.

Abstract: An object of the invention is to provide a process in which Michael addition reaction products generated as by-products in a (meth)acrylic acid production step are pyrolyzed to enable high-purity (meth)acrylic acid to be recovered at a high recovery and troubles such as clogging in production steps are prevented.

Abstract: In an acrylic acid production process which comprises the step of producing acrylic acid by catalytic vapor-phase oxidation of propane, propylene, and/or acrolein; and purifying the acrylic acid produced in the step of producing with distillation in the presence of the polymerization inhibitor for preventing polymerization of the acrylic acid, a viscosity at 20° C. of the bottoms which comprises the polymerization inhibitor, discharged in the step of purifying, is adjusted to 2 Pa.s (2,000 cP) or less and the polymerization inhibitor is extracted using an aqueous medium.

Abstract: Thermal separating process between at least one gaseous and at least one liquid stream, of which at least one comprises (meth)acrylic monomers, in a separating column whose separating internals are mass transfer trays, in which the liquid stream is polymerization-inhibited and used for spraying the surface of the separating column, and internal surfaces which are in the shadow region of the spraying are removed from the shadow region by covering.

Abstract: In a process for rectificative isolation of (meth)acrylic acid from a mixture containing, as main components, (meth)acrylic acid and an organic liquid having a higher boiling point than (meth)acrylic acid, the rectification is carried out with the addition of a surfactant.

Abstract: A method for purifying a crude (meth)acrylic acid obtained by a vapor phase catalytic oxidation method, characterized in that the crude (meth)acrylic acid having most parts of water and acetic acid removed therefrom, is fed to and distilled in a first distillation column of a purification system comprising first to third three distillation columns, the top fraction from the first distillation column is fed to and distilled in the second distillation column, the resulting top fraction is recovered as a high purity (meth)acrylic acid product, the bottoms from the first and second distillation columns are fed to and distilled in the third distillation column, and the resulting top fraction is fed to the first distillation column.

Abstract: A method for collecting acrylic acid comprising the step of collecting acrylic acid using an aqueous medium from a reaction gas comprising acrylic acid obtained by catalytic vapor-phase oxidation of propane, propylene, and/or acrolein, the step being conducted so as to satisfy the following formula (1) wherein A represents a weight fraction of acrylic acid to all condensable ingredients in the reaction gas before collecting acrylic acid and B represents a weight fraction of acrylic acid in bottoms of a collection device used in the step of collecting. According to the method, acrylic acid can be efficiently collected from the reaction gas comprising acrylic acid obtained by catalytic vapor-phase oxidation.

Abstract: There are disclosed an apparatus and a process for purification of an acrylic acid family.

Abstract: A method for distilling a raw material liquid containing (meth)acrylic acid substantially free from azeotropic solvents, collected with a collection agent from a mixed gas obtained by gas phase catalytic oxidation reactions which includes feeding to a distillation column the raw material liquid which temperature is substantially equal to that of the entrance place in the column.

Abstract: Basic (meth)acrylates IV are prepared by transesterification of alkyl (meth)acrylates I in the presence of a catalyst and working-up of the reaction mixture by distillation, by a process in which a gas or gas mixture which is inert under the reaction conditions is passed through the reaction zone and/or heat exchanger.

Abstract: A process is provided which can effectively inhibit occurrence of hot spots in reaction zones or heat accumulation at the hot spots, in the occasion of producing acrolein and acrylic acid through vapor phase oxidation of propylene in the presence of a catalyst using a fixed bed shell-and-tube reactor, said catalyst having a composition represented by a general formula (1): MoaWbBicFedAeBfCgDhEiOx (wherein A is at least an element selected from Co and Ni; B is at least an element selected from P, Te, As, B, Sb, Sn, Ce, Nb, Pb, Cr, Mn and Zn; C is alkali metal element; D is alkaline earth metal element; E is at least an element selected from Si, Al, Ti and Zr; and O is oxygen; a, b, c, d, e, f, g, h, i and x denote the atomic numbers of Mo, W, Bi, Fe, A, B, C, D, E and O, respectively, and where a is 12, b is 0-5, c is 0.1-10, d is 0.1-10, e is 1-20, fis 0-5, g is 0.001-3, h is 0-3, i is 0-30, and x is a numerical value which is determined depending on the extent of oxidation of each of the elements).

Abstract: An antifoulant composition comprising (meth)acrylic acid and one or more (meth)acrylate or (meth)acrylamide antifoulant polymers and a method of preventing fouling in (meth)acrylic acid processes comprising adding the (meth)acrylate or (meth)acrylamide antifoulant polymers to the (meth)acrylic acid process stream.

Abstract: The invention relates to a method for the production of a purified melt of a monomer melt obtained by condensation, absorption or extraction in a crystallizer, wherein the inlet to the crystallizer is subjected to a mechanical solid/liquid separation operation.

Abstract: In a thermal separating process between at least one gaseous and at least one liquid stream, of which at least one comprises (meth)acrylic monomers, in a separating column containing sieve trays as separating internals, at least some of the sieve trays are operated above an entrainment fraction of 10% by weight.

Abstract: The invention relates to a method for purifying a raw melt of at least one monomer by crystallization, wherein suspension crystallization is initially used and the resulting remaining melt or the suspension crystals that have been molten once again and separated are subjected to a mechanical separation operation before undergoing subsequent purification by crystallization.

Abstract: A perforated tray without downcomer in accordance with the present invention satisfies following conditions: (a) The hole has a diameter of 10 mm to 25 mm. (b) Two adjacent holes are spaced by a distance of 1.2 d to 3 d, measured between the two centers. (c) The tray thickness is 2 mm to 8 mm. (d) The opening ratio is 10% to 30%. A perforated tray tower without downcomer fitted with two or more such perforated trays without downcomer in accordance with the present invention satisfies following conditions: (g) Perforated trays are spaced by a distance of 0.1 D to 0.5 D (D denotes the tower diameter). (h) The levelness of each perforated tray is 8 mm or less. (i) If a plurality of perforated trays are used at the same stage, the two most closely located holes that respectively belong to adjacent perforated trays are spaced by a distance of 50 mm to 150 mm, measured between the two centers.

Abstract: A process for the continuous recovery of (meth)acrylic acid from the reaction gas of a catalytic gas-phase oxidation comprising the following process stages is proposed:

Abstract: The invention relates to a process for the purification of (meth)acrylic acid in a process stage that comprises the following process steps: a) (meth)acrylic acid is crystallised out from a mother liquor; b) crystallised (meth)acrylic acid is separated from the mother liquor; c) at least part of the separated (meth)acrylic acid crystals are melted; d) the melted part is at least partially recycled to the step a) or step b). The process according to the invention, the apparatus suitable for implementing the process, and the use of the apparatus according to the invention for the production of (meth)acrylic acid are characterised by a high purity of the thereby obtainable (meth)acrylic acid as well as by a high efficiency with regard to the achievable yield and necessary energy requirement.

Abstract: Separations processes and apparati capable of purifying thermally sensitive materials at high capacity. An apparatus having a rectification section and a stripping section with the stripping section having a stripping tray with 5 to 50% open area, a pressure drop from 0.02 psi to 0.2 psi and a tray efficiency during operation of the column which is equal to or greater than 20%.

Abstract: A hydraulically sealed crossflow mass transfer tray, separating columns which contain the hydraulically sealed crossflow mass transfer tray and the use of such separating columns for thermal separating processes.

Abstract: Economical processes are disclosed for recovery and refining of at least acrylic acid from a gaseous mixture such as is obtainable by gas-phase catalytic oxidation of propylene. Processes of the invention include quenching the gaseous mixture with an aqueous quench liquid to obtain an aqueous solution comprising the acid values; contacting the aqueous solution with an immiscible extraction solvent; and an integrated sequence of distillations and phase separations to recover for recycle organic components of the extraction solvent, and obtain valuable acrylic acid and acetic acid products. Advantageously, the immiscible extraction solvent is substantially free of aromatic compounds such as benzene and toluene.

Abstract: A process for preparing acrylic acid and/or acrylates which comprises the following stage A and, if desired, B and C: A: cooling a gaseous reaction mixture which comprises acrylic acid and is obtained in the gas-phase oxidation to prepare acrylic acid, using oligomeric acrylic acid or a mixture of acrylic acid and oligomeric acrylic acid, to give a gaseous mixture comprising acrylic acid and a quench bottom product which comprises oligomeric acrylic acid; B: separating the gaseous mixture comprising acrylic acid, to give a low-boiling fraction, a crude acrylic acid, and a bottom product, which comprises oligomeric acrylic acid; C: esterifying the crude acrylic acid obtained in stage B by means of one or more alkanols.

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 0.2-4.5 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 and a method for purifying acrylic acid, comprising a step for purifying the acrylic acid-containing organic liquid obtained by the step mentioned above. By this invention, a product of acrylic acid containing a low boiling substance at a low concentration can be produced.

Abstract: (Meth)acrylic acid is worked up in the presence of at least one stabilizer by a process in which a stabilizer-containing mixture originating from the working-up and substantially freed from (meth)acrylic acid is passed into a distillation apparatus and a stabilizer-containing low boiler stream obtained from said apparatus is recycled to the working-up.

Abstract: Acrylic acid or methacrylic acid is purified by crystallization to obtain crystals and a mother liquor, by a process in which the crystals are washed with a wash liquid containing the acid and having a temperature from 15 to 40° C. Furthermore, a process for the preparation of acrylic acid or methacrylic acid comprises the abovementioned purification process.

Abstract: Acrylic acid or methacrylic acid is purified be crystallization to obtain crystals and a mother liquor, by a process in which the crystals are washed with a was liquid containing the acid and having a temperature from 15 to 40° C. Furthermore, a process for the preparation of acrylic acid or methacrylic acid comprises the abovementioned purification process.

Abstract: A process for working up mixtures containing (meth)acrylic acid and/or (meth)acrylic ester in a column for distilling, rectifying and/or fractionally condensing in the presence of at least one polymerization inhibitor and an oxygen-containing gas, wherein the partial oxygen pressure p(O2) in the gas phase of the entire column is from 2 to 5 hPa.

Abstract: A process for cleaning apparatus in which (meth)acrylic acid-containing organic solvents have been treated and/or generated and contain fouling and/or polymer and residues of organic solvent, in which the apparatus contents are subjected to a steam distillation in the apparatus.

Abstract: The invention concerns a method for stabilising acrylic monomers in a distillation column, comprising the following steps: adding at least a stabilising agent for acrylic monomers having a total concentration in the liquid phase ranging between 1 ppm and 5000 ppm; injecting oxygen in the distillation column with a O2/organic vapour mol ratio ranging between 0.01% and 1%; adding a metal sequestering agent having a concentration in the liquid phase ranging between 0.1 and 1000 ppm.

Abstract: A method for starting up a distilling column destined to handle an easily polymerizing compound-containing solution characterized by supplying at the start of the operation of the distilling column a polymerization inhibitor to the bottom liquid of the distilling column having a temperature of not higher than 80° C. Further, by supplying a reflux liquid through the top of the distilling column or the middle stage of the column prior to the start of the temperature elevation of the distilling column, thereby preventing the polymerization of the easily polymerizing compound more effectively.

Abstract: A method of manufacturing (meth)acrylic acid includes: a reaction step of carrying out a catalytic gas-phase oxidation reaction; an absorbing step of absorbing (meth)acrylic acid from a (meth)acrylic-acid-containing mixed gas prepared in the reaction step; a refinement step of separating, refining, and recovering (meth)acrylic acid from a (meth)acrylic-acid-containing liquid prepared in the absorbing step; and a recirculation step of recirculating (meth)acrylic acid contained in a vent gas produced in the refinement step to the absorbing step and/or the refinement step.

Abstract: A process for the manufacture of methyl methacrylate includes a process for separating the methyl methacrylate from certain impurities, at least one of which has a freezing point of greater than −50° C., by a fractional crystallisation process.

Abstract: In distillation of a polymerizable compound such as (meth)acrylic acid or a liquid containing such a polymerizable compound with use of a distillation column equipped with a reboiler, (a) a vertical multi-tube reboiler whose outlet nozzle inside diameter (D1) is 0.2 to 1 time its reboiler shell inside diameter (D2) is used as the reboiler, (b) an outlet of an outlet nozzle of the reboiler to a gas-phase section of the distillation column is provided at a position such that a distance L from the top tubesheet of the reboiler to the lower end of the outlet of the outlet nozzle satisfies L=(0.4 to 3)×D1, and (c) a liquid level in the distillation column is maintained in a range such that a height H of the liquid level from the top tubesheet of the reboiler satisfies H=(0.1 to 0.8)×L.

Abstract: A method for the absorption of (meth)acrylic acid and/or (meth)acrolein and an apparatus thereof which, in an absorption column adapted to cause an (meth)acrylic acid and/or (meth)acrolein-containing gas obtained in consequence of catalytic gas phase oxidation to come into countercurrent contact with a solvent, contemplate using a packing of relatively high efficiency in absorption disposed on the upstream side of the flow of a liquid containing the solvent and a packing and/or trays of relatively low performance of forming polymerization disposed on the downstream side thereof, in the column.

Abstract: The invention relates to a method and a device for purifying mixtures of substances by means of optionally fractional crystallization. During the crystallization process, impurities can precipitate in addition to the desired product, since these are present in such high concentrations that the limit of solubility is exceeded. According to the inventive method, a solvent or a mixture of solvents with a strong affinity to an impurity with a tendency to precipitate is added to the mixture of substances or the melt to be purified so that the corresponding impurity is kept in solution. If there are several impurities with a tendency to precipitate, some of the impurities can be kept in solution by adding a suitable solvent and the remainder can be separated by mechanical means, e.g. filtering by suction, centrifugation, etc.

Abstract: A method for inhibiting polymerization during transportation, storage and/or production of (meth)acrylic acid or an ester thereof includes adding an N-oxyl compound and water to a vinyl compound; or dissolving an N-oxyl compound in water and adding the solution to a vinyl compound in a process of recovering, purifying, and/or synthesizing of the vinyl compound. The method can effectively inhibit polymerization of the vinyl compound.

Abstract: A process for recovering carboxylic acids from an aqueous mixture such as a fermentation broth using a solvent containing at least one olefin without the need for first removing the spent microorganism cells is provided. A co-solvent which increases the partition coefficient of the solvent relative to the carboxylic acid may optionally be included.

Abstract: For a heat exchanger using a heating medium for the purpose of heating a fluid to be handled during a steady state, this invention provides a method for using relevant devices which enables the heat exchanger to be operated safely and infallibly without suffering the raw material or the reaction product to polymerize in the reactor or the pipes during an unsteady state, suffering the reactor or the pipes to sustain a fracture owing to a rise in the internal pressure of the vessel, and suffering the apparatus for production to sustain serious damage. This invention pertains, mainly in a heat exchanger admitting a heating medium and using it for the purpose of heating a fluid to be handled, to a method for using relevant devices during the unsteady state, characterized by introducing a cooling medium in the place of the heating medium mentioned above.

Abstract: The present invention provides a column treating method by use of a distillation column and so on, which method enables to effectively remove solid impurities such as precipitates and polymers contained or produced in a treating fluid, and to thereby stably operate the column treatment. Solid impurities in a treating fluid can be removed by carrying out: step (a) of drawing out the treating fluid from a drawing out outlet (16) at the column bottom of the treatment column (10) outside the treatment column (10), step (b) of removing solid impurities from the treating fluid, drawn out in step (a), by a strainer (40), and step (c) of returning the treating fluid, from which the solid impurities are removed in step (b), to a returning inlet (18) of the treatment column, with advancing physical and/or chemical treatment of the treating fluid in the treatment column (10).

Abstract: A process for the fractional condensation of a gas mixture which, in addition to acrylic acid or methacrylic acid, also contains at least one further condensable component and additionally a high proportion of one or more noncondensable components, wherein the gas mixture is passed through a column having separatory internals and the condensable components are condensed by cooling.

Abstract: A process is provided herein for the high yield production of high purity glacial methacrylic acid (“HPMAA”) that is substantially pure, specifically 99% pure or greater with a water content of 0.05% or less.

Abstract: A method for producing (meth)acrylic acid of high purity by repressing formation of a polymer possibly generated during the course of production is disclosed. The production is accomplished by returning the waste liquid generated at the step of the addition of aldehyde treating agents (d) to the step of the absorption (b) and/or the step of separation (c).

Abstract: A purifying apparatus characterized by being equipped with a vapor dispersing device possessing in a vapor inlet part owned by the apparatus on the lateral inside thereof an opening part facing downward from the horizontal direction and a horizontal projected cross section area in the range of 10-40% of the cross section area of said apparatus. In consequence of the incorporation of the vapor dispersing device according to this invention, the drift of the gas is repressed, the efficiency of separation is improved, and the possible polymerization of a compound under treatment in the lower part of the column is prevented.

Abstract: This invention relates to an improved process for preparing acrylic acid from propylene using a tandem reactor and utilizing an increased amount of propylene reactant, thereby providing increased capacity and throughput. An improved process for purifying acrylic acid is also disclosed.

Abstract: A method for refining an easily polymerizable matter while preventing an easily polymerizable matter-containing substance from being polymerized and an apparatus for use in the method are disclosed. The method and apparatus for refining and separating the easily polymerizable matter-containing substance by the use of a distillation column provided with a heat exchanger set the linear velocity of a vapor in a connecting line intervening between the distillation column and the heat exchanger at a level of not less than 5 m per second and the retention time of the vapor at a level of not more than 3 seconds.

Abstract: A distillation apparatus is provided with a distillation tower, a reboiler, a bottom outflow pipe for drawing a liquid from the bottom of the distillation tower, and a pot provided between the bottom of the distillation tower and the bottom outflow pipe. A part of the drawn liquid is discharged to the outside of the distillation apparatus while the rest is flowed to the reboiler. The pot has a cross-sectional area smaller than a cross-sectional area of the distillation tower and larger than a cross-sectional area of the bottom outflow pipe.