Hi Christian, Ken and Ken, Juan and all This is all very interesting. First, Ken from the Phillipines, personally I didn't come up with anything much, except maybe saying "use more" (I usually use 22%). The stoichiometric value for methanol is generally put at 12.5% or 13% by volume, and I guess the 20% comes from that. Some people say you need more excess for full conversion, up to 25% total, others use 30% or even more, for tallow eg, others yet say using more than 20% total is generally a waste. The results from using 20% (and good practices) are generally good. So we should add to that: "... for most feedstocks, in most cases."
Christian says the stoichiometric value for methanol of sunflower oil is lower, 11%. For coconut oil Christian gets a value of 17.44%; using Christian's SG figures Ken's 96g MeOH per 665g oil comes to 16.79% (according to this calculator at least). Anyway, rather more than 13%. What else would this apply to? I guess palm oil, tallow would also need more methanol, any others? - and any idea how much? Hydrogenated stuff too maybe? Could we figure out a table for the most common oils? Say soy, rapeseed/canola, corn, sunflower, cottonseed, peanut, olive, coconut, palm, tallow. That would be really useful. We'd need to know the FA breakdown of each, SG etc. There are some figures here for the main FAs: http://journeytoforever.org/biofuel_library/fatsoils/fatsoils2.html#2-2 Slightly different to Ken's for coconut though, and not for all the most common oils. Is the 3.5g per litre of catalyst, which is also put as low as 3.1 or higher than 4, also specific to oil type? Best wishes Keith >Ken from Phillipines writes: > > > > > > in short there is around 1.74 moles of glycerine for every 1000 grams of > >> refined coconut oil. From here i would need 5.22 moles of >methanol or 210 > >> ml of methanol. The receipe in journey to forever says to use 200 ml of > >> methanol for every 1000 ml of oil and they say that has alot of excess > >> already. So this is my dilema, are my calculations wrong. I wonder how > > > Keith and the rest came up with the prescribed volume for methanol. > > > > >The 200 ml per liter of oil is a little low for good conversion, even for the >oils typically used over here, like soy and canola. It would be very low for >coconut, which has a much lower molecular weight (i.e., one liter of coconut >oil is more moles than one liter of soy oil, and therefore needs more moles >of methanol to transesterify). > >I get a MW of about 665 for coconut oil (the whole molecule, with the >glycerol). >So stoich. for methanol would be 96g MeOH per 665g oil, and I'd recommend >twice that (100% excess) for best conversion. ------------------------ Yahoo! Groups Sponsor ---------------------~--> Buy Stock for $4 and no minimums. FREE Money 2002. http://us.click.yahoo.com/orkH0C/n97DAA/Ey.GAA/FGYolB/TM ---------------------------------------------------------------------~-> Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Biofuels list archives: http://archive.nnytech.net/ Please do NOT send "unsubscribe" messages to the list address. To unsubscribe, send an email to: [EMAIL PROTECTED] Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
