ABSTRACT Background: The wood heat treatment results in the partial degradation of its chemical constituents, mainly cellulose and hemicellulose, reducing the hygroscopicity of the material. This process improves the dimensional stability and resistance to biodeterioration and worsens the mechanical resistance. This work aimed to evaluate the effect of heat treatment on the physical, anatomical, chemical, and mechanical properties of Fraxinus excelsior wood. In untreated and heat-treated wood, the pH, buffering capacity, basic density, equilibrium moisture content, shrinkage, wood anatomy, thermogravimetric behavior, and chemistry by conventional and FTIR methods were determined. Results: Heat treated wood had lower pH (5.50), equilibrium moisture content (6.26%), shrinkage (7,29%), holocellulose contents (55,96%) and higher buffering capacity (0,479 mmol/L), extractives (8,25%), and lignin contents (35,78%). Heat treatment reduced the pH and increased the buffering capacity of the wood, reduced the holocellulose content, and increased the lignin content, leaving the wood less hygroscopic and reducing its volumetric and linear variation. The process did not change the basic density and fiber length, but it reduced their width, lumen diameter, and wall thickness. The FTIR analysis confirmed the degradation of holocellulose and division of aliphatic side chains in lignin. The maximum dredging range of untreated and heat-treated wood occurred at 350 ºC, and the heat-treated wood had a higher residual mass when subjected to 500 ºC. Conclusion: Heat-treated wood can be indicated for products used in external environments, such as floors, fences, coatings, door and window structures.

ABSTRACT Wood from planted forests is the main input in the charcoal production chain. However, the heterogeneity of charcoal, in terms of its physical, chemical and mechanical properties, and the low yield in production processes is among the main problems faced by industries. To select the best clones for the production of charcoal for steelmaking, the objective of this work was to evaluate the properties of wood, in addition to the yield and quality of charcoal from different genotypes of Eucalyptus and Corymbia. Five clones of Eucalyptus spp., 8 years old and one of Corymbia torelliana x Corymbia citriodora, 4 years old were studied. In the wood were determined the basic density, structural chemical composition, thermogravimetric analysis (TG/DTG), crystallinity index and higher heating value. Carbonizations were carried out in a muffle oven, with a total time of 270 minutes, starting at 150°C and ending at 450°C. The gravimetric yield, apparent density, higher heating value and proximate analysis of charcoal were determined. The wood basic density varied between 477 and 652 kg/m3, with the highest value observed for the Eucalyptus cloeziana clone. This clone also had the highest total lignin content (32.6%), the highest charcoal yield (36.3%) and charcoal with the highest apparent density (466 kg/m3). The two clones of Eucalyptus urophylla had the highest heating value for charcoal, whose mean was 7545 kcal/kg. The clone of Corymbia torelliana x Corymbia citriodora, having an apparent density greater than 500 kg/m3 at 4 years of age, stood out in terms of productivity. All evaluated clones have potential for charcoal production, however, the Eucalyptus cloeziana clone stood out positively, being the most suitable for charcoal production.

RESUMO A madeira oriunda de florestas plantadas é o insumo principal na cadeia produtiva do carvão vegetal. No entanto, a heterogeneidade do carvão vegetal, em termos de suas propriedades físicas, químicas e mecânicas e o baixo rendimento nos processos de produção, está entre os principais problemas enfrentados pelas indústrias. Visando selecionar os melhores clones para a produção de carvão vegetal para uso siderúrgico, o objetivo desse trabalho foi avaliar as propriedades da madeira, além do rendimento e qualidade do carvão vegetal provenientes de diferentes genótipos de Eucalyptus e Corymbia. Foram estudados cinco clones de Eucalyptus spp., com idade de 8 anos e um de Corymbia torelliana x Corymbia citriodora, com idade de 4 anos. Na madeira, determinou-se a densidade básica, composição química estrutural, análise termogravimética (TG/DTG), índice de cristalinidade e poder calorífico superior. Foram realizadas carbonizações em forno mufla, com tempo total de 270 minutos, iniciando em 150°C e finalizando em 450°C. Determinou-se o rendimento gravimétrico, a densidade aparente, o poder calorífico superior e a composição química imediata do carvão vegetal. A densidade básica da madeira variou entre 477 e 652 kg/m3, sendo que o maior valor foi observado para o clone de Eucalyptus cloeziana. Este clone também apresentou o maior teor de lignina total (32,6%), maior rendimento em carvão vegetal (36,3%) e carvão vegetal com maior densidade aparente (466 kg/m3). Os dois clones de Eucalyptus urophylla apresentaram maior poder calorífico superior para o carvão vegetal, cuja média foi 7545 kcal/kg. O clone de Corymbia torelliana x Corymbia citriodora, por ter densidade aparente superior a 500 kg/m3, aos 4 anos de idade, foi o destaque em termos de produtividade. Todos os clones avaliados possuem potencial para a produção de carvão vegetal, porém o clone Eucalyptus cloeziana se destacou positivamente, sendo o mais indicado para a produção de carvão vegetal.