Changes in the extract composition and lignin structure are the main factors that affect color changes in wood during heat treatment. GC–MS analysis revealed that changes in the aromatic and ketone containing compounds in the extractives followed the same trend as changes in the ΔE^* of the wood. 2D-HSQC NMR analysis showed that the lignin structure of heat-treated Chinese fir pretreated with aluminum sulfate changed significantly, and β-O-4 bonds were broken in the side chains. Additionally, condensation reactions occurred on the benzene ring, indicating that sulfate ion obviously affected the heat treatment of wood. Further analysis of lignin with XPS, UV–Vis, and FTIR showed that pretreatment with 0.2 mol/L aluminum sulfate produced more –C=O bonds in heat-treated Chinese fir, more hydroxyl groups at a dosage of 0.4 mol/L, and more ether bonds when the dosage reached 0.6 mol/L. These structural changes are thought to be related to the H⁺ produced by the hydrolysis and absorption-bridge reactions of aluminum ions in wood during heat treatment. At the same impregnation dosage, as the heat treatment temperature increased, the ΔE* gradually increased.

提取物成分和木质素结构的变化是影响木材在热处理过程中颜色变化的主要因素。GC-MS分析表明，萃取物中含芳族和酮类化合物的变化与ΔE ^*的变化趋势相同木头。2D-HSQC NMR分析表明，用硫酸铝预处理的杉木冷杉的木质素结构发生了明显变化，β-O-4键在侧链中断裂。另外，苯环上发生缩合反应，表明硫酸根离子明显影响了木材的热处理。用XPS，UV-Vis和FTIR对木质素进行的进一步分析表明，用0.2 mol / L硫酸铝预处理在热处理过的杉木中产生更多的–C = O键，以0.4 mol / L的用量产生更多的羟基，并且当剂量达到0.6 mol / L时，更多的醚键。这些结构变化被认为与H ^+有关通过热处理过程中木材中铝离子的水解和吸收桥反应生成。在相同的浸渍剂量下，随着热处理温度的升高，ΔE*逐渐增加。