Alkaline Conventional and in Situ Transesterification of Cottonseed Oil for the Production of Biodiesel

Abstract

In the present work, the transesterification of cottonseed oil with methanol and ethanol, in the presence of alkali catalyst (NaOH), using low-frequency ultrasonication (24 KHz) and mechanical stirring (600 rpm) for the production of biodiesel fuel was studied. Both conventional and in situ transesterification were investigated. Use of ultrasonication in conventional transesterification with methanol gave high yields of methyl esters (95%) after a short reaction time (20 min) similar to those using mechanical stirring. Higher concentrations of NaOH (2.0%) gave higher ester yields. Use of ultrasonication in conventional transesterification with ethanol gave similar yields to those using mechanical stirring but significantly lower than respective yields using methanol. In the in situ transesterification, the use of ultrasonication and mechanical stirring led to similar high yields (95%) of methyl esters after approximately 20 min of reaction time. In the presence of ethanol, use of ultrasonication led to high ester yields (98%) in only 40 min of reaction time while use of mechanical stirring gave low yields (78%) even after 4 h of reaction time. In situ transesterification gave similar ester yields to those obtained by conventional transesterification being an efficient and economical process. Reaction rate constants were calculated, using first-order reaction kinetics, to be equal to 3.1 × 10−3 s−1 for conventional transesterification using methanol and 2.0% NaOH, and 7.0 × 10−4 s−1 using ethanol.

Production of methyl and ethyl biodiesel fuel from pequi oil (Caryocar brasiliensis Camb.)

“…Dozens of plant species grow in Brazil which can be used to produce biodiesel, including castor oil plant, palm, sunflower, baru, babassu, peanut, jatropha, soybean [8,11,12,15,[17][18][19]. Pequi grows in the Cerrado region (Brazil), in the transitions between the Amazon forests and the Cattinga, and also in the Cerrado enclaves in the Amazon and Atlantic forests.…”

The biodiesel production from the cotton thistle seed oil (Onopordum acanthium L.)

“…Georgogianni i sar. [17,18] su poredili mogućnost primene modela nepovratne reakcije psedo-prvog i pseudo-drugog reda za modelovanje reakcije metanolize suncokretovog i pamukovog ulja pri mehaničkom mešanju i u ultrazvučnom polju. Iako oba modela daju dobar matematički opis kinetike procesa metanolize, autori preporučuju primenu modela nepovratne reakcije psedo-prvog reda zbog boljeg slaganja sa eksperimentalnim podacima.…”

“…4. Kinetika reakcija metanolize ulja semena O. acanthium L. se može opisati modelima nepovratne reakcije pseudo-prvog reda ili pseudo-drugog reda [17,18]. 5.…”

“…Nakon toga sadržaj MEMK ostaje nepromenjen, što ukazuje na uspostavljanje ravnotežnog sastava reakcione smeše. Do sličnog zaključka došli su i drugi istrazivači metanolize različitih biljnih ulja [14,[16][17][18][19]. Sadržaj TAG u uljno-estarskoj fazi u toku reakcije smanjuje se istovremeno sa povećanjem koncentracije MEMK, dok se sadržaj DAG i MAG povećava na početku reakcije, dostiže maksimum, a zatim opada, nakon čega njihove koncentracije ostaju nepromenjene.…”

“…Za opisivanje kinetike reakcije metanolize ulja semena pamuka [17] i suncokreta [18], izvedene pri mehaničkom mešanju i u ultrazvučnom polju, primenjeni su, takođe, modeli nepovratne reakcije pseudo-prvog i pseudo-drugog reda. Iako su oba kinetička modela bila prihvatljiva za fitovanje eksperimentalnih podataka, bolje slaganje je zabeleženo u slučaju primene modela nepovratne reakcije pseudo-prvog reda, pa je on predložen kao bolji model.…”