Synthesis and identification of furfural from rice straw

M. Sashikala and H.K. Ong

Abstract

Laboratory-scale extraction of furfural from rice straw was carried out in an attempt to create value-added products from rice straw, which has become a seasonal source of air pollution in granary areas of Malaysia due to open burning. The extraction was based on the conversion of the pentosan fraction in rice straw into pentose, which was then cyclodehydrated to furfural using dilute sulphuric acid. Yield of furfural obtained was 71 g/kg of dry straw. This yield was lower than a reported yield from corn cob (110 g/kg), but higher than that from bagasse (25 g/kg). The yield obtained was only 56.8% of the maximum theoretical yield. Furfural obtained was characterised using infra-red analysis (IR), gas chromatography (GC) and gas chromatography with mass spectrophotometer (GCMS). IR spectrum exhibited a very strong absorption at 1,706.02 cm-1, indicating the presence of the conjugated carbonyl (C=O) group. The presence of the aldehyde was proven by two peaks attained at 3,004.26 cm-1 and 2,811.71 cm-1. Results obtained from GC and GCMS also identified the presence of furfural with a probability of 98.4%. A molecular ion peak at m/z 96.03 was obtained, which correlates to a molecular formula of furfural, namely C5H4O2. The product was colourless but turned yellowish and then dark brown upon exposure to air and light. It had a smell resembling that of bitter almond and its vapour was irritable to skin and eyes.

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