Liquefação direta do bagaço de cana com formiato de sodio em meio aquoso

AUTOR(ES)
DATA DE PUBLICAÇÃO

1984

RESUMO

The direct liquefaction of sugar cane bagasse was studied in water with formate/argon(A) and, for comparative purposes, with Ca(OH)2/CO(B) and Ca(OH)2/argon(C). Conversion of sugar cane bagasse and yield for extracted oil in the three systems increase with temperature and are higher with reaction systems A and B. The experiments show that the direct application of sodium formate results in maximum reductive efficiency for the conversion at temperatures of about 240°C. With system A, the extracted oil presents a higher H/C ratio than with the other two systems. For system A, various parameters of the reaction, such as pressure, reaction time, water/bagasse ratio and quantity of formate added, were studied to elucidate the appropriate conditions for future studies of conversion of the sugar cane bagasse in a semi-continuous tubular reactor. The conversion and yields of oil extracted with chloroform are markedly pressure dependent. The reaction time is relatively short. With system A the conversion is almost complete after 15 min at 180°C, and an increase in reaction time is less effective than an increase in temperature. For the system formate/argon, the ratios that favour the conversion of the bagasse are situated between 2,5:1 and 10:1 and the higher yield of extracted oil is obtained with a 2,5:1 ratio. As expected, the conversion increases with the amount of formate added. The yield of extracted oil reaches a maximum at 70 wt% for 30 wt% of formate added. Studies of the catalytic effect in the transfer of hydrogen from the formate ion to the bagasse at 180°C during 15 minutes demonstrate that the formate ion is very effective in the bagasse reduction, independent whether the cation is a metal or a non metal, when compared with the system Ca(OH)2/argon. Among the salts studied. KI, Sn(II), Fe(II), Ni(II), Cu(II), Zn(II), Mo(II), Rh(II), Pd(II), Pt(II) and Ce(III) did not influence the reaction. The only ones that enhance the yield of extracted oil are Ni(II), Pd(II) and Pt(II). The tranfer of hydrogen from formate ion to the bagasse is not significantly enhanced through homogeneous catalysis. The only gaseous product of the liquefaction of the sugar cane bagasse was identified by gas chromatography as being carbon dioxide. Hydrocarbons, alcohols, phenols and carboxylics acid are detected in the oils using infrared H-NMR and NMR spectroscopy. The identification of these products is in progresso In the residue water carboxylic acids such as acetic acid, oxalic acid and protocatechuic acid were identified, in addition to unreacted sodium formate. The gradual substitution of water by ethanol demonstrated that, although pure ethanol solubilizes the derivative products of lignin more easily it is not a good system for the reaction. On the other hand, water/ethanol mixtures increase the yield of extracted oil. The addition of hydroquinone to the formate/argon reaction system has no effect on the conversion of the bagasse or the yield of extracted oil, indicating that direct liquefaction with formate ion as reducing agent does not occur via radicals. Because the individual components of the oil were not identified, it is difficult to discuss the mechanism of formation of the products. However, there is evidence that hydrolysis, hydrogenolysis and Cannizzaro type disproportionation reactions occur during the direct liquefaction of the sugar cane bagasse and the hydrogen necessary for the hydrogenolysis reaction comes from the formate ion. Due to the large range of molecular weight these oils are chemically rather complex. The separation of the phenols resulted in decomposition of part of these oils.

ASSUNTO(S)

bagaço de cana

ACESSO AO ARTIGO

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