Patent ID: 7662991

Claim:
A method for the manufacture of amino alkylene phosphonic acid, comprising reacting in presence of not more than 0.4% by weight, expressed in relation to the level of the phosphorous acid component (100%), of hydrohalogenic acid: (a): phosphorous acid; (b): an amine; and (c): a formaldehyde; in reactant ratios as follows: (a):(b) of from 0.05:1 to 2:1; (c):(b) of from 0.05:1 to 5:1; and (c):(a) of from 5:1 to 0.25:1; wherein (a) and (c) stand for the number of moles to be used and (b) represents the number of moles multiplied by the number of N—H functions in the amine, in the presence of a heterogeneous, with respect to the reaction medium, Broensted acid catalyst selected from the group of: (1) solid acidic metal oxide combinations or supported onto a carrier material; (2) cation exchange resins selected from the group comprising copolymers of styrene, ethylvinyl benzene and divinyl benzene, functionalized so as to graft SO 3 H moieties onto the aromatic group and perfluorinated resins carrying carboxylic and/or sulfonic acid groups; (3) organic sulfonic and carboxylic Broensted acids which are substantially immiscible in the reaction medium at the reaction temperature; (4) an acid catalyst derived from: (i) the interaction of a solid support having a lone pair of electrons onto which is deposited an organic Broensted acid; or (ii) the interaction of a solid support having a lone pair of electrons onto which is deposited a compound having a Lewis acid site; (iii) heterogeneous solids functionalized by chemical grafting with a Broensted acid group or a precursor therefore, and (5) heterogeneous heteropolyacids of the general formula H x PM y O z wherein P is selected from phosphorus and silicon and M is selected from W and Mo and combinations thereof followed by recovering the amino alkylene phosphonic, whereby all the available N—H functions in 50% or more of the amine raw material are converted to the corresponding alkylene phosphonic acids.