METHOD FOR SULPHONATING MEDIUM IMPACT POLYSTYRENE AND USING SAME AS A CATALYST IN REACTIONS COMPRISING THE ESTERIFICATION OF FATTY ACIDS

摘要

The invention relates to a process in which, once the medium impact polystyrene (waste or virgin) has been characterised, then the polymer can be sulphonated if brought into contact with fuming sulfuric acid (18-24% of SO₃) between 70°C-78°C for 130-170 minutes using ratios between 10: 1 and 20:1 (volume of acid (mL)/polystyrene mass (g)) with stirring of 240-320 rpm. Certain operating conditions within these ranges allow the degree of sulphonation to be maximised and the consumption of acid to be minimised, conferring on the method a technical effect which is not obvious and is different from sulphonation processes known in the prior art. The product of the sulphonation process of the invention (after being washed and characterised qualitatively and quantitatively) can be used as a catalyst in processes for the production of biodiesel from oils that contain a percentage of free fatty acids above 1%. The process is an acid esterification in which if stirring of 600-800 rpm is performed at a temperature of 60° C for 1 hour using 0.06-0.18 grams of catalyst per gram of free fatty acid in the sample and ratios of 30-50 mole methanol per mole of free fatty acid in the sample then it is possible that the catalyst of the invention can promote (within the established esterification ranges) reaction yields up to 90%, easily removed from the medium following filtration.