Process for the production of a fertilizer

A process for producing an aqueous solution comprising potassium phosphite chosen from K2HPO3, KH2PO3, and combinations thereof, said method comprising the steps of:

• a. reacting a carboxylic acid of the formula R—(C(═O)OH)n with phosphorous trichloride (PCl3) to make a mixture comprising phosphorous acid (H3PO3) and an acid chloride of the formula R—(C(═O)Cl)n;
• wherein R is a linear or branched alkyl or alkanediyl group with 1-20 carbon atoms and n is 1 or 2 or R is a cyclohexyl group and n is 1,
• b. subjecting the mixture to a separation step, thereby obtaining (i) a fraction comprising crude phosphorous acid (H3PO3) and (ii) a fraction comprising the acid chloride, and
• c. combining water, a potassium compound selected from KOH, KHCO3 and K2CO3, and the fraction comprising the crude phosphorous acid, thereby forming an aqueous solution comprising the potassium phosphite and having a pH below 5, and
• d. removing organic compounds.

A process for producing an aqueous solution comprising KH2PO3, the method comprising the steps of:

• a. reacting dodecanoic acid with phosphorous trichloride (PCl3) to make a mixture of phosphorous acid (H3PO3) and dodecanoyl chloride,
• b. subjecting the mixture to a separation step, thereby obtaining (i) a fraction of crude phosphorous acid (H3PO3) and (ii) a fraction of dodecanoyl chloride, and
• c. combining water, KOH, and the fraction of the crude phosphorous acid (H3PO3), thereby forming an aqueous solution of KH2PO3 and having a pH below 5, and
• d. removing organic compounds.