Isolation of KH2PO4 from crude glycerol purified using Acromonia aculleata charcoal as adsorbent and its application in the synthesis of methyl salicylate.

Abstract Activated charcoal was prepared from Acrocomia aculeata (macaúba) endocarp by ZnCl₂ activation. The charcoal was used for the adsorptive purification of pretreated crude glycerol (CG) and potassium dihydrogen phosphate (KH₂PO₄ or KDP) was formed by the addition of H₃PO₄ to the crude glycerol containing KOH, which was used as catalyst in the production of biodiesel and glycerol. The KH₂PO₄ was isolated and purified by recrystallization from aqueous solution. The KH₂PO₄ was characterized by X-Ray diffraction (XRD), thermal analysis (TGA/DTA) and spectrophotometry in the infrared region – FTIR. From 216.0 g of crude glycerol, 20.1038 g of purified KH₂PO₄ was obtained. The KH₂PO₄ was used in a simple, regioselective, green method as a selective base for the methylation of the salicylic acid (SA) carboxylate group using DMS as the methylating agent in the production of MS at reflux temperature (90 oC). The present method has a short reaction time, and it is simple with excellent yields of MS. In this process, DMS was used in excess because it has been shown to be an excellent eco-friendly, aprotic solvent for the SN2 mechanism. The reuse of organic waste was accompanied by the transformation of DMS into the K₂SO₄ drying agent and H₃PO4 into KH₂PO₄, a source of potassium and phosphate in fertilizers. This reaction is the first example of the use of KH₂PO₄ as a useful selective base for methylation, and the present method obeys the reduce-reuse-recycle (RRR) principle for the development of a green protocol. Microbial susceptibility tests were accomplished by adding suspensions of microorganisms and spreading them on the surfaces of the Mueller Hinton and YPMD agar culture media, in which there were central wells containing 60 µL of pure MS, which inhibited the growth of Escherichia coli, Proteus mirabilis, Sporothrix sp, Rhodotorula mucilaginosa, Galactomyces geotrichum, Candida orthopsilosis and Candida akabanensis.