Propane remains the preferred feedstock for petrochemical users in Northwest Europe, due to lower prices compared with butane, sources said this week.

"We are buying propane -- it makes sense right now," said a trader.

Large propane cargoes were assessed at $794/mt by Platts on Thursday, compared with $901/mt for butane.

"At this level, petchems are more interested," said another trader.

Butane prices have been surging, pushed by the seasonal uptick in demand for gasoline blending and tightening supply. Meanwhile, propane supply is ample, with healthy cargo inflows from outside the NWE region and good coaster supply from the Tees terminal in the UK.

"Propane is $100/mt cheaper than butane and nobody really wants crude C4 so the choice is quite obvious," said one petrochemical trader.

The yield percentage for crude c4 is higher from butane than propane.

According to Platts data, the spot price crude c4 CIF NWE was assessed at $824.50/mt last Friday. Crude c4 prices collapsed earlier this year amid slack synthetic rubber demand, after touching a two-month high in early May of $1,149/mt. Prices have recovered since July, but the market is still characterized as sluggish.

Crude c4 and propylene are co-products from a cracker whose primary output is ethylene.