Avantium, a 2000 spin-off from Shell with technologies for converting plant sugars into biochemicals and polymers, says it will make an initial public offering of shares on two European stock exchanges by the end of March. The firm hopes to raise a little more than $100 million. It is an unusual move. Biobased chemical companies have shied away from stock offerings in recent years because biomaterial prices have been suppressed by the low price of crude oil. Avantium says it will invest up to $80 million of the money it raises in its Synvina joint venture with BASF. The venture plans a 50,000-metric-ton-per-year plant for 2,5-furandicarboxylic acid, a sugar-derived intermediate for recyclable polyesters such as polyethylene furanoate (PEF). The facility will be located at BASF’s site in Antwerp, Belgium. BASF will put up the rest of the money for the plant, which is expected to cost up to about $300