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Previous issue date: 2012-05-28 / CAPES / Biochar is composed not only of stable carbon, certain portion of this material is relatively easily degraded and this condition is not only dependent on the characteristics of the feedstock, but also on the pyrolysis conditions, especially the final temperature. Thus, the aim of this study was to evaluate the effects of pyrolysis final temperature on the stability of biochar produced from residues of softwoods (Pinus caribaea and Pinus taeda) and hardwoods (Eucalyptus dunnii and Eucalyptus urophylla). For in natura feedstocks, the content of Klason lignin was quantified, it was proceeded elemental analysis, thermogravimetric analysis (TGA/DTA) and solid-state nuclear magnetic resonance 13C (13C NMR). For biochars, which were produced at a heating rate of 10?C.min-1 for 60 min at 5 different temperatures (350, 400, 450, 500 and 550?C) it was proceeded proximate analysis s and to the materials produced 350, 450 and 550 ? C, elemental analysis, TGA / DTA and 13C NMR. In order to evaluate the stability of biochar, the stable carbon fraction was quantified (Tce) by thermochemical oxidation with a 5% H2O2 solution at 80?C for 48h, the materials produced at 350, 450 and 550 ?C, before and after oxidation, were analyzed by 13C NMR technique. The contents of Klason lignin did not differ statistically by Tukey test at 5%. As higher the pyrolysis final temperature was, lower was the yield of biochar, higher was the content of fixed carbon (Tcf), lower was the O/C and H/C ratios, higher was the thermogravimetric index (ITG) and higher was the Tce, indicating the increase in stability of these materials after pyrolysis, and this effect was more evident as higher was pyrolysis final temperature. The Rcf and Rce varied little in all the treatments, indicating that no significant gain or loss independent of the feedstock and/or pyrolysis final temperature. High Pearson correlation (0.96) between Rcf and Rce suggests that both approaches could be used to estimate the stable fraction of biochar. From 13C NMR spectra it was observed that biochars produced at 350?C, signals relating to lignin were still present. For 450 and 550?C, the spectra were very similar, indicating that there is no need to produce biochar above these temperatures, since the structure of the materials slightly altered, with a predominance of aromatic structures. For biochars produced at 350?C, it was observed that thermochemical oxidation was responsible for removing the labile structures still present as well as aromatic structures less resistant to degradation. For 450 and 550?C, as they already had the predominance of aromatic structures, thermochemical oxidation has been mainly active in these structures, however much milder. The thermochemical oxidation was responsible for the functionalization of biochars, this effect being milder, as higher was pyrolysis final temperature. Thus, biochars produced at pyrolysis final temperatures up to 450?C, were more stable and therefore more resistant to degradation. / O biocarv?o n?o ? composto somente de carbono est?vel. Certa por??o do material ? degradada com certa facilidade, sendo esta condi??o dependente n?o somente das caracter?sticas da mat?ria-prima, mas tamb?m das condi??es de pir?lise, principalmente a temperatura final de produ??o. Dessa forma, o objetivo geral deste estudo foi avaliar os efeitos da temperatura final de pir?lise na estabilidade de biocarv?o produzido a partir de res?duos florestais de esp?cies de (Pinus caribaea e Pinus taeda) e folhosas (Eucalyptus dunnii e Eucalyptus urophylla). Para as mat?rias-primas in natura, quantificou-se o teor de lignina de Klason, procedeu-se a an?lise elementar, an?lise termogravim?trica (TGA/DTA) e resson?ncia magn?tica do 13C no estado s?lido (RMN 13C). Para os biocarv?es, os quais foram produzidos a uma taxa de aquecimento de 10?C.min-1 por 60 min em 5 diferentes temperaturas (350, 400, 450, 500 e 550?C) procedeu-se a an?lise imediata e para os materiais produzidos a 350, 450 e 550?C, a an?lise elementar, TGA/DTA e RMN 13C. A fim de avaliar a estabilidade do biocarv?o, quantificou-se o teor de carbono est?vel (Tce) atrav?s da oxida??o termoqu?mica com solu??o de H2O2 5 %, a 80?C por 48h, sendo os materiais produzidos a 350, 450 e 550?C, antes e ap?s a oxida??o, analisados atrav?s da t?cnica de RMN 13C. Os teores de lignina de Klason n?o diferiram estatisticamente pelo Teste de Tukey a 5%. Quanto maior a temperatura final de pir?lise, menor o rendimento em biocarv?o, maior o teor de carbono fixo (Tcf), menores as raz?es O/C e H/C, maior o ?ndice termogravim?trico (ITG) e maior o Tce, indicando o aumento da estabilidade dos materiais ap?s a pir?lise, sendo este efeito mais evidente, quanto maior a temperatura final de pir?lise. O Rcf e o Rce variaram pouco para todos os tratamentos, indicando que n?o foram observados ganhos ou perdas expressivos, independente da mat?ria-prima e/ou da temperatura final de pir?lise. A alta correla??o de Pearson (0,96) entre Rcf e Rce sugere que ambas as metodologias poderiam ser utilizadas para estimar a fra??o est?vel do biocarv?o. A partir dos espectros de RMN 13C ? poss?vel observar que em biocarv?es produzidos a 350?C, sinais referentes ? lignina ainda est?o presentes. Em 450 e 550?C, os espectros s?o bem semelhantes, evidenciando que n?o h? necessidade de se produzir biocarv?o acima dessas temperaturas, uma vez que a estrutura qu?mica dos materiais pouco se altera, com o predom?nio de estruturas arom?ticas. Para os biocarv?es produzidos a 350?C, observa-se que a oxida??o termoqu?mica foi respons?vel por remover parte das estruturas l?beis ainda presentes, bem como estruturas arom?ticas menos resistentes ? degrada??o. Em 450 e 550?C, como j? havia o predom?nio de estruturas arom?ticas, a oxida??o termoqu?mica atuou principalmente nestas estruturas; no entanto, de uma forma mais branda. A oxida??o termoqu?mica foi respons?vel pela funcionaliza??o dos biocarv?es, sendo este efeito mais brando, quanto maior a temperatura final de pir?lise. Dessa forma, biocarv?es produzidos em temperaturas finais de pir?lise acima de 450?C, mostraram-se mais est?veis, logo, mais resistentes ? degrada??o.
| Identifer | oai:union.ndltd.org:IBICT/oai:localhost:jspui/1808 |
| Date | 28 May 2012 |
| Creators | ALHO, Carlos Francisco Braz?o Vieira |
| Contributors | Lelis, Roberto Carlos Costa, Novotny, Etelvino Henrique, Maia, Claudia Maria Branco de Freitas, Lelis, Roberto Carlos Costa, Abreu, Heber dos Santos, Guiotoku, Marcela |
| Publisher | Universidade Federal Rural do Rio de Janeiro, Programa de P?s-Gradua??o em Ci?ncias Ambientais e Florestais, UFRRJ, Brasil, Instituto de Florestas |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Format | application/pdf |
| Source | reponame:Biblioteca Digital de Teses e Dissertações da UFRRJ, instname:Universidade Federal Rural do Rio de Janeiro, instacron:UFRRJ |
| Rights | info:eu-repo/semantics/openAccess |
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