Abstract:
A process for inhibiting unwanted free-radical polymerization of acrylic acid present in a liquid phase P whose acrylic acid content is at least 10% by weight and which, based on the weight of the acrylic acid present therein, additionally comprises at least 100 ppm by weight of propionic acid and at least 100 ppm by weight of glyoxal, in which at least one chemical compound of the element copper is added to the liquid phase P, and the resulting liquid phases P to which a chemical compound of the element copper has been added.
Abstract:
A method is disclosed for transferring heat to a liquid F containing dissolved monomeric acrylic acid, acrylic acid oligomers obtained by Michael addition, and acrylic acid polymer with the help of an indirect heat exchanger to which the liquid F is fed at a temperature T F ≥ 150°C and a heat transfer fluid W is fed at a temperature T w > T F . In said method, gas bubbles or thin layers of liquid F bordering a gas phase are generated in the liquid F while said liquid F flows through the heat exchanger.
Abstract:
The invention relates to a column for treating substance mixtures by intense contact with a liquid and gaseous phase, wherein on the inside the column has one or more cross-flow bottoms on which heat transfer elements (7) are disposed, through which a heat transfer medium flows, and wherein above one or more of said cross-flow bottoms fluid distributors (4, 5) are disposed, which have outflow openings (6) through which the fluid is evenly distributed via the heat transfer elements (7) beneath the fluid distributors (4, 5), and wherein the fluid distributors (4, 5) are disposed above the heat transfer elements (7) in the column such that they are located in the vicinity of the inflow line or outflow line of the heat transfer medium into the heat transfer elements (7).
Abstract:
The invention relates to a method for starting a heterogeneously catalyzed partial gas phase oxidation of acrolein into acrylic acid or of methacrolein into methacrylic acid at a fixed catalyst bed that is located in a shell-and-tube reactor cooled with a heat exchanger means, wherein the temperature of the heat exchanger means is ≥ 290°C, and wherein the temperature of the reactor bottom surface facing the reactor gas inlet mixture and the temperature of the reaction gas inlet mixture are ≤ 285°C.
Abstract:
The invention relates to an integrated method for producing trioxane from formaldehyde. According to said method, a flow A1 containing water and formaldehyde as well as a recirculation flow B2 substantially composed of water and formaldehyde are delivered to a trioxane synthesis reactor in which the formaldehyde is reacted to trioxane such that a product flow A2 containing trioxane, water, and formaldehyde is obtained. Flow A2 and a recirculation flow D1 containing trioxane, water, and formaldehyde are fed to a first distillation column and are distilled at a pressure ranging from 0.1 to 2.5 bar such that a trioxane-enriched flow B1 and flow B2, which is essentially composed of water and formaldehyde, are obtained. Flow B1 is delivered to a second distillation column and is distilled at a pressure ranging from 0.2 to 17.5 bar such that a product flow substantially comprising trioxane and a flow C1 containing trioxane, water, and formaldehyde are obtained. Flow C1 is fed to a third distillation column and is distilled at a pressure ranging from 1 to 10 bar such that the recirculation flow D1 containing trioxane, water, and formaldehyde as well as a flow D2 that is substantially composed of water are obtained.
Abstract:
The invention relates to an integrated process for preparing trioxane from formaldehyde, comprising the steps of: a) feeding a stream A1 comprising water and formaldehyde and a recycle stream B2 consisting essentially of water and formaldehyde to a trioxane synthesis reactor and allowing them to react to obtain a product stream A2 comprising trioxane, water and formaldehyde; b) feeding stream A2 to a first low-pressure distillation column and distilling it at a pressure of 0.1 to 2.5 bar to obtain a stream B1 which has been enriched in trioxane and additionally comprises water and formaldehyde and the recycle stream B2 which consists essentially of formaldehyde and water; c) feeding stream B1 and a recycle stream D1 which comprises trioxane, water and formaldehyde to a second low-pressure distillation column and distilling them at a pressure of 0.1 to 2.5 bar to obtain a stream C1 comprising predominantly trioxane and additionally formaldehyde and water, and a stream C2 consisting essentially of formaldehyde and water; d) feeding stream C1 to a high-pressure distillation column and distilling it at a pressure of 0.2 to 17.5 bar to obtain the recycle stream D1 and a product stream D2 consisting essentially of trioxane, wherein a removal of the low boilers present in streams B1 and/or C1 can be undertaken between steps b) and c) or c) and d).
Abstract:
The invention relates to a method for stabilising acrylic compounds, wherein a liquid phase, which contains at least one acrylic compound from the group acrylic acid, methacrylic acid and their respective esters, is mixed with at least one metal from the group copper, manganese and cerium and at least one ligand from the group consisting of a) quinoline compounds of formula (I), wherein the symbols have the following meanings: X is OH, NH 2 , O-C 1 -C 4 -alkyl, preferably OCH 3 , O-C(O)-C 1 -C 4 -alkyl, preferably O-C(O)-CH3, O-C(O)-C 2 H 5 or O-C(O)-phenyl; R 1 is H, or (C 1 -C 4 )-alkyl, preferably methyl; R 2 is H, C 1 -C 4 -alkyl, preferably methyl, Cl, Br or SO 3 H and R 3 is H, Cl or Br; and N-oxides of compounds of formula (I), b) 2,2'-bis(2,3-dihydro-3-oxoindolylides) and c) aliphatic y-dentate ligands where y = 2-6, containing at least two nitrogen atoms and y-2 further coordinating aliphatic or aromatic C 1 -C 4 carbon bridges containing nitrogen atoms or heteroatoms.