Transesterification by subcritical methanol
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 1, January, 2008
107
Synthesis of biodiesel (general procedure). A mixture of VO
and absolute methanol (6 mL) was heated in an autoclave under
the conditions indicated in Table 3 (the average molecular weight
of VO was accepted as 940). After the end of heating, the reacꢀ
tion mixture was concentrated, diluted with hexane, washed
with water to remove glycerol, dried over magnesium sulfate,
and analyzed by the 1H NMR method for a decrease in the
intensities of the characteristic signals of glycerides (δ 4.2—4.5,
AB part of the ABC system of glycerol) and the appearance of
the signal from the CH3O group of methyl esters (δ 3.7).
the temperature increase to 260 °С or upon the addition
of alumina. The maximum content of methyl esters of
higher acids was achieved with an increase in the VO :
MeOH ratio to 1 : 42 (entry 6).
Thus, we showed that carboxylic acids and their esters
undergo esterification and transesterification by subcritiꢀ
cal methanol already at 220 °С. The results obtained can
provide the development of new, more efficient and ecoꢀ
logical methods for the synthesis of biodiesel from vegetaꢀ
ble oils, fats, and waste cooking oils.
References
Experimental
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All experiments were carried out in a 30ꢀmL stainless steel
autoclave equipped with an P60 tensometric pressure gauge.
1H NMR spectra were recorded on a Bruker DPXꢀ200 specꢀ
trometer with a working frequency of 200 MHz relative to Me4Si
in СDCl3.
4. F. M. Gumerov, F. R. Gabitov, R. A. Gazizov, T. R. Bilaꢀ
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Fluids], 2006, 1, 66 (in Russian).
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yashi, C. Kamizawa, D. Shintani, A. Negishi, C. Tsurumi,
J. Supercrit. Fluids, 2003, 26, 215.
Benzoic acid (Acros), absolute methanol (Merck), ethyl benꢀ
zoate (Acros), and alumina (Engelhard Eꢀ800) were used withꢀ
out additional purification. Solid superacid (NiSO4(5%)/Al2O3
and Fe2(SO4)3(5%)/Al2O3) was prepared according to known
procedures.14,15 Refined sunflower vegetable oil was used for the
synthesis of biodiesel. An authentic sample of biodiesel was preꢀ
pared as described previously.17
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39, 245.
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Phase Equilibria, 2002, 198, 37.
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Intern. Conf. "Sustainable Energy and Environment (SEE
2006)," Bangkok, Thailand, 2006, 21.
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Mishra, M. J. Reaney, Bioresource Technology, 2004, 92, 55.
Esterification of benzoic acid (general procedure). A solution
of benzoic acid in methanol (5 mL) was heated in an autoclave
under the conditions indicated in Table 1, while the pressure did
not exceed 42 atm. After the end of the process, the autoclave
was cooled, and the reaction mixture was concentrated on a
rotary evaporator, removing excess methanol and water. The
reaction mixture was analyzed by the NMR method for the ratio
of intensities of signals from the CH3O groups (δ 3.9) and metaꢀ
and paraꢀprotons of the phenyl group (δ 7.2—7.5). The preparaꢀ
tive experiment involved benzoic acid (6.1 g, 0.05 mol) and
methanol (20 mL) (see Table 1, entry 3), and after the solvent
was evaporated, the residue was distilled in vacuo to give methyl
benzoate (4.2 g, 61%). Its 1H NMR spectrum and properties
coincided with those described in literature.
Transesterification of ethyl benzoate with methanol (general
procedure). A solution of ethyl benzoate in absolute methanol
(5 mL) was heated in an autoclave under the conditions indicatꢀ
ed in Table 2. After the end of the process, the autoclave was
cooled down, the reaction mixture was concentrated, and the
residue was analyzed by the 1H NMR method for the ratio of
intensities of signals from the CH3O (δ 3.9) and CH3—CH2—O
(δ 1.4) groups.
Received June 21, 2007;
in revised form October 22, 2007