Process for the preparation of mixtures of methylenedianiline and its higher homologous products
AssigneeDow Global Technologies LLC
InventorsCarlo Perego, Alberto De Angelis, Carlo Perego
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Abstract
Process for the production of methylenedianiline and its higher homologous products which comprises reacting aniline or one of its derivatives, and formaldehyde, or one of its precursors in one or two reactors in the presence of a solid acid catalyst selected from a zeolite or a silico-alumina, distilling the reaction water or the water added with the reagents.
Claims12
A process for the production of compounds having general formula (I) which comprises:
- (a) reacting aniline or one of its derivatives, and formaldehyde, or one of its precursors, in proportions ranging from 2 to 10 moles of aniline per mole of formaldehyde, at a temperature ranging from 10-60° C. and in the absence of an acid catalyst, so as to form an aminal mixture in aniline;
- (b) separating the water from the aminal mixture to a residual concentration of water equal to about 1-2% by weight;
- (c) optionally diluting the solution previously formed in step (b), in aniline;
- (d) isomerizing the aminal mixture by feeding it into one or more fixed bed reactors containing a solid acid catalyst selected from a zeolite or a silico-alumina, at a temperature ranging from 100 to 250° C., and at atmospheric pressure or at a value which is such as to maintain the reagent mixture in the liquid state;
- (e) removing the aniline from the methylenedianiline, or its higher homologous products, by means of distillation.
The process according to any of the previous claims, wherein the solid acid catalyst is selected from zeolites in acid form having a spaciousness index ranging from 2.5 to 19, extremes included.
The process according to any of the claims from 1 to 3, wherein the solid acid catalyst is selected from silico-aluminas amorphous to X-rays,-with a molar ratio SiO2/Al2O3 ranging from 10/1 to 500/1 , a porosity ranging from 0.3 to 0.6 ml/g and a pore diameter ranging from 20 to 500 Å.
The process according to any of the previous claims, wherein the composition of the mixture obtained after isomerization is modified in the distribution of its components by totally or partially recycling the mixture itself to the aminal synthesis zone or to the isomerization reactor.
A process for the production of compounds having general formula (I) which comprises reacting aniline, or one of its derivatives, and formaldehyde, or one of its precursors, in a single reactor with complete mixing in the presence of a solid acid catalyst selected from a zeolite or a silico-alumina, as previously described, continuously distilling the reaction water or the water added with the reagents.
The process according to any of the claims from 7 to 9, wherein the molar ratios between aniline and formaldehyde range from 0.5 to 10.
The process according to any of the claims from 7 to 10, wherein the reaction temperature ranges from 30 to 200° C.
The process according to any of the claims from 7 to 11, wherein the weight ratio charge/catalyst ranges from 1/20 to 1/300.
Dependencies are inferred from the claim text.