| Biodiesel and nontoxic cottonseed meal were co-producted from cottonseed using two-step two-phase solvent extraction （TS-TSE）. Comparing with one-step two-phase solvent extraction of cottonseed, TS-TSE was conducted in two steps on the basis of invariant total dosage of methanol. Methanol from the second-step extraction of TS-TSE could be used as raw material in transesterification, and there was no need for fresh methanol, so methanol dosage and regeneration load of solvent reduced. The optimal transesterification conditions were obtained as follows: methanol dosage in the first-step extraction 60% of total methanol dosage, catalyst dosage 1.1% （based on the mass of cottonseed oil）, reaction temperature 60℃and reaction time 120 min. Under these conditions, the content of fatty acid methyl ester in the biodiesel product reached 98.8%, and the content of free gossypol in cottonseed meal extracted was 0.013%, which was accord with USA National Cottonseed Products Association standard and suitable for being used as animal feed. |
