摘要:
A process for starting-up a heterogeneously catalyzed partial gas phase oxidation of acrolein to acrylic acid or of methacrolein to methacrylic acid over a fixed catalyst bed disposed in a tube bundle reactor cooled by a heat exchange medium, wherein the temperature of the heat exchange medium is ≧290° C. and the temperature of that reactor plate surface which faces the reaction gas entry mixture and the temperature of the reaction gas entry mixture itself are ≦285° C.
摘要:
A process for starting-up a heterogeneously catalyzed partial gas phase oxidation of acrolein to acrylic acid or of methacrolein to methacrylic acid over a fixed catalyst bed disposed in a tube bundle reactor cooled by a heat exchange medium, wherein the temperature of the heat exchange medium is ≧290° C. and the temperature of that reactor plate surface which faces the reaction gas entry mixture and the temperature of the reaction gas entry mixture itself are ≦285° C.
摘要:
A process for separating acrylic acid present as a main product and glyoxal present as a by-product in a product gas mixture of a partial gas phase oxidation of a C3 precursor compound, in which a liquid phase P is obtained, which consists of acrylic acid to an extent of at least 70% of its weight and, based on the molar amount of acrylic acid present therein, comprises at least 200 molar ppm of glyoxal, in which the glyoxal is separated from the acrylic acid in the liquid phase P by crystallization.
摘要:
A process for redissociating Michael adducts which are present in a liquid F with a proportion by weight of ≧10% by weight and have been formed in the preparation of acrylic acid or esters thereof in a redissociating apparatus which comprises a pump P, a separating column K with separating internals and a circulation heat exchanger UW, wherein, for the purpose of supplying the cleavage energy, the pump P sucks in bottoms liquid from the bottom space of the separating column K and, via the circulation heat exchanger UW, continually recycles it into the bottom space above the level of the bottoms liquid, and wherein the pump P is a radial circulation pump with an open impeller.
摘要:
A process for separating acrylic acid present as a main product and glyoxal present as a by-product in a product gas mixture of a partial gas phase oxidation of a C3 precursor compound, in which a liquid phase P is obtained, which consists of acrylic acid to an extent of at least 70% of its weight and, based on the molar amount of acrylic acid present therein, comprises at least 200 molar ppm of glyoxal, in which the glyoxal is separated from the acrylic acid in the liquid phase P by crystallization.
摘要:
A process for removal of a crude acrylic acid from a product gas mixture which comprises glyoxal as a by-product from a heterogeneously catalyzed partial gas phase oxidation of at least one C3 precursor compound, which comprises the absorption of the acrylic acid in a high-boiling absorbent and the rectificative workup of the resulting adsorbate, and in which absorbent present in the bottoms liquid withdrawn from the bottom space of the absorption column is distilled off in a distillation unit and recycled into the absorption, before high boilers which remain are discharged, and in which the glyoxal content of the crude acrylic acid is reduced by restricting the high boiler residence time in the distillation unit.
摘要:
Processes are disclosed comprising: (a) reacting an aqueous formaldehyde solution in a reactor in the presence of a suitable catalyst to obtain a reaction product mixture comprising trioxane, formaldehyde and water; (b) distilling the reaction product mixture to form a top stream comprising crude trioxane; and (c) treating the top stream in one or more additional stages to form pure trioxane; wherein an aqueous sidestream is drawn off during the distilling of the reaction mixture.
摘要:
A process for preparing trioxane by trimerization of formaldehyde in aqueous acidic solution and subsequently removing trioxane from a mixture substantially comprising trioxane, water and formaldehyde (crude trioxane product), which comprises a) distilling the crude trioxane product from the trimerization, b) crystallizing the trioxane out and c) removing it from the mother liquor and d) subsequently melting it and e) distilling off further by-products.
摘要:
A process for redissociating Michael adducts which are present in a liquid F with a proportion by weight of ≧10% by weight and have been formed in the preparation of acrylic acid or esters thereof in a redissociating apparatus which comprises a pump P, a separating column K with separating internals and a circulation heat exchanger UW, wherein, for the purpose of supplying the cleavage energy, the pump P sucks in bottoms liquid from the bottom space of the separating column K and, via the circulation heat exchanger UW, continually recycles it into the bottom space above the level of the bottoms liquid, and wherein the pump P is a radial circulation pump with an open impeller.
摘要:
The present invention relates to a process for distillatively removing pure trioxane from a feedstream (I) comprising trioxane in a proportion of at least 50% by weight, based on the total weight of the feedstream (I), and additionally formaldehyde and water, which comprises feeding the feedstream I and a further aqueous stream (II) which does not contain any components extraneous to the feedstream to a dividing wall column (TWK1) having a dividing wall TW which is arranged substantially perpendicularly and divides the column interior into a feed region (A1), a withdrawal reaction (B1), an upper combined column region (C1) and a lower combined column region (D1), and drawing off from the first dividing wall column (TWK1) a bottom stream (III) comprising pure trioxane and a sidestream (IV) at the withdrawal region (B1), comprising pure water.