Polpação de palha de milho, utilizando-se diferentes processos organosolv

AUTOR(ES)
DATA DE PUBLICAÇÃO

1995

RESUMO

Taking into account the availability of corn husks and the increasing interest for alternative raw materiais that can replace wood in the manufacture of paper, we have investigated the possibility of pulping corn husks using different Organosolv processes. Chemical analysis gave the following results: 13% humidity, 1% ash, 7% extractives, 24% Klason lignin, 54% cellulose and 16% polyoses (by difference), with a total of 71% holocellulose. Microanalysis gave 45.5% C, 4.5% H, 0.75% N and 48.9% O (by difference). The Acetosolv, the Formacell, the Acetona and the Acesolv processes were studied. Optimum values for yield and Kappa number of the pulps were determined by varying the cooking time, cooking temperature, solvent/husk ratio and solvent mixture. The Acetosolv process consists of cooking the corn husks with the 93% acetic acid under reflux and HCI as catalyst. The best result ave a 55% yield, a Kappa number of 18 and a viscosity of 14 cP (solvent/husk ratio 14/1 v/w, 120 min and 2% w/w of HCI, with respect to corn husks). The Formacell process consists of cooking the lignincellulosics in an autoclave, with 85% of a mixture of acetic acid and formic acid and 15% water. The best result gave a 43% yield, a Kappa number of 14 and a viscosity of 6 cP (solvent/husk ratio 7/1 v/w, 150°C and 30 min). The Acetona process uses a solvent mixture of acetone and formic acid and needs cooking in an autoclave. The best result gave a 37% yield, a kappa number of 22 and a viscosity of 10 cP (solvent/husk ratio 10/1 v/w, 165°C, 30 min). The Acesolv process uses a solvent mixture of acetic acid, ethyl acetate and water and needs cooking in an autoclave. The best result gave a 43% yield, a Kappa number of 15 and a viscosity of 9 cP (solvent/husk 7/1 v/w, 150°C and 60 min). These results show that the Acetona process is not efficient for corn husk pulping. The Acetosolv process is the best for high pulp ylelds and the Formacell and Acesolv processes give purer pulps. In the study of different pulp washings (different solvents, cold and hot) we observed that the Kappa number and viscosity are strongly affected but the pulp yields do not change. The best results were found for washing the pulp with hot solvent, using the same solvent with the used in the pulping process. In this case, we observed that the kappa number and the viscosity diminish approximately in 45% and 20%, respectively (related to cold washing). The relative crystallinities were determined for the best pulps by x-ray diffraction and were found to be between 35% and 52%. The IR analysis showed that the cellulose is acetylated in the Acetosolv, Formacell and Acesolv pulps. The Acetona pulps showed acetone incorporation. 84% to 98% of the solvents were recycled. The isolated lignins were obtained in 47% to 126% with respect to the initial lignin content of the corn husks and the Klason lignin content was 67% to 97%. The IR analysis showed that the lignin of the corn husks is predominantly guaiacylic. The correlation factors for the Kappa numbers and residual Klason lignin were determined for the Formacell (0.26), Acetona (0.30) and Acesolv (0.23) processes.

ASSUNTO(S)

milho palha - utilização milho - pesquisa

ACESSO AO ARTIGO

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