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US 4,191,695 AGranted
Process for obtaining maleic acid anhydride
AssigneeLonza Ltd.
InventorsAmleto Neri, Sergio Sanchioni, Carlo Nava
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Abstract
A process for obtaining maleic acid anhydride from an aqueous maleic acid solution obtained from the gas phase oxidation of at least one organic compound having at least 4 carbon atoms by washing out the reaction gases with water, characterized in that a H.sub.2 O exchange is carried out between maleic acid and an organic carboxylic acid anhydride.
Claims33
A process for preparing maleic acid anhydride which comprises:
- (1) obtaining an aqueous maleic acid solution by washing the reaction gases from the gas phase oxidation of at least one organic compound having at least 4 carbon atoms with water;
- (ii) removing the water from the aqueous maleic acid solution, maleic acid resulting;
- (iii) the step which consists of dehydrating the maleic acid to maleic acid anhydride in the presence of an organic carboxylic acid anhydride, there being a H.sub.2 O exchange between the maleic acid and the organic carboxylic acid anhydride according to the following formula:
- ##STR2## wherein A is two monovalent organic radicals or one divalent organic radical, the dehydration reaction taking place at a temperature between 100.degree. and 130.degree. C., and there being present from one mole to 3 moles of organic carboxylic acid anhydride per mole of maleic acid, and (iv) isolating the maleic acid anhydride, said isolation being achieved by centrifugation or filtration when the organic carboxylic acid anhydride or step (iii) is an organic dicarboxylic acid anhydride and said isolation being achieved by fractional distillation when the organic carboxylic acid anhydride of step (iii) is an organic monocarboxylic acid anhydride.
1 more element
A process for preparing maleic acid anhydride which comprises:
- (i) obtaining an aqueous maleic acid solution by washing the reaction gases from the gas phase oxidation of at least one organic compound having at least 4 carbon atoms with water;
- (ii) removing the water from the aqueous maleic acid solution, maleic acid resulting;
- (iii) the step which consists of dehydrating the maleic acid to maleic acid anhydride in the presence of an organic carboxylic acid anhydride and an inert solvent, there being a H.sub.2 O exchange between the maleic acid and the organic carboxylic acid anhydride according to the following formula:
- ##STR4## wherein A is two monovalent organic radicals or one divalent organic radical, the dehydration reaction taking place at a temperature between 100.degree. and 130.degree. C., and there being present from one mole to 3 moles of organic carboxylic acid anhydride per mole of maleic acid;
- and (iv) isolating the maleic acid anhydride, said isolation being achieved by centrifugation or filtration when the organic carboxylic acid anhydride of step (iii) is an organic dicarboxylic acid anhydride and said isolation being achieved by fractional distillation when the organic carboxylic acid anhydride of step (iii) is an organic monocarboxylic acid anhydride.
2 more elements
A process for preparing maleic acid anhydride which comprises:
- (i) obtaining an aqueous maleic acid solution by washing the reaction gases from the gas phase oxidation of at least one organic compound having at least 4 carbon atoms with water;
- (ii) removing the water from the aqueous maleic acid solution, maleic acid resulting;
- (iii) the step which consists of dehydrating the maleic acid to maleic acid anhydride, there being a H.sub.2 O exchange between the maleic acid and the organic carboxylic acid anhydride according to the following formula:
- ##STR6## wherein A is:
- (a) two monovalent --CH.sub.3 groups, whereby the anhydride is acetic acid anhydride;
- (b) two monovalent --C.sub.6 H.sub.5 groups, whereby the anhydride is benzoic acid anhydride;
- (c) the --CH.sub.2 CH.sub.2 --group of succinic acid anhydride;
- (d) the --C.sub.6 H.sub.8 -- group of 4-cyclohexene-1,2-dicarboxylic acid anhydride or one of its isomers;
- (e) the --C.sub.7 H.sub.10 -- group of 4-methyl-cyclohexene-1,2-dicarboxylic acid anhydride or one of its isomers;
- (f) the --C.sub.6 H.sub.10 -- group of hexahydrophthalic acid anhydride;
- (g) the --C.sub.7 H.sub.12 -- group of 4-methyl-hexahydrophthalic acid anhydride;
- or
- (h) a --CH.sub.3 group and a --C.sub.2 H.sub.5 group whereby the anhydride is acetic propionic acid anhydride,
- the dehydration reaction taking place at a temperature between 100.degree. and 130.degree. C., and there being present from one mole to 3 moles of organic carboxylic acid anhydride per mole of maleic acid;
- and (iv) isolating the maleic acid anhydride, said isolation being achieved by centrifugation or filtration when the organic carboxylic acid anhydride of step (iii) is an organic dicarboxylic acid anhydride and said isolation being achieved by fractional distillation when the organic carboxylic acid anhydride of step (iii) is an organic monocarboxylic acid anhydride.
12 more elements
A process for preparing maleic acid anhydride which comprises:
- (i) obtaining an aqueous maleic acid solution by washing the reaction gases from the gas phase oxidation of at least one organic compound having at least 4 carbon atoms with water;
- (ii) removing the water from the aqueous maleic acid solution, maleic acid resulting;
- (iii) the step which consists of dehydrating the maleic acid to maleic acid anhydride in the presence of an organic carboxylic acid anydride and an inert solvent, there being an H.sub.2 O exchange between the maleic acid and the organic carboxylic acid anhydride according to the following formula:
- ##STR7## wherein A is:
- (a) two monovalent --CH.sub.3 groups, whereby the anhydride is acetic acid anhydride;
- (b) two monovalent --C.sub.6 H.sub.5 groups, whereby the anhydride is benzoic acid anhydride;
- (c) the --CH.sub.2 CH.sub.2 -- group of succinic acid anhydride;
- (d) the --C.sub.6 H.sub.8 -- group of 4-cyclohexene-1,2-dicarboxylic acid or one of its isomers;
- (e) the --C.sub.7 H.sub.10 -- group of 4-methyl-cyclohexene-1,2-dicarboxylic acid anhydride or one of its isomers;
- (f) the --C.sub.6 H.sub.10 -- group of hexahydrophthalic acid anhydride;
- (g) the --C.sub.7 H.sub.12 -- group of 4-methyl-hexahydrophthalic acid anhydride;
- or
- (h) a --CH.sub.3 group and a --C.sub.2 H.sub.5 group, whereby the anhydride is acetic propionic acid anhydride,
- the dehydration reaction taking place at a temperature between 100.degree. and 130.degree. C., and there being present from one mole to 3 moles or organic carboxylic acid anhydride per mole of maleic acid;
- and (iv) isolating the maleic acid anhydride, said isolation being achieved by centrifugation or filtration when the organic carboxylic acid anhydride of step (iii) is an organic dicarboxylic acid anhydride and said solution being achieved by fractional distillation when the organic carboxylic acid anydride of step (iii) is an organic monocarboxylic acid anhydride.
12 more elements
Dependencies are inferred from the claim text.