Quantitative ¹³C NMR Characterization of Milled Wood Lignins Isolated by Different Milling Techniques

Abstract

Milled wood lignins (MWL) prepared from finely milled wood flour produced by different milling techniques were compared by quantitative ¹³C NMR. Wood meal produced in a Wiley mill was milled for either six weeks in a porcelain rotary mill with porcelain balls, or by two variations of our standard technique. Specifically the Wiley wood meal was milled for one week in the rotary mill followed by 48 h of vibratory ball‐milling with steel balls either in toluene or under a N₂ atmosphere. Results showed that the vibratory‐milled samples were similar in structure with the exception that the preparation milled under N₂ had higher aliphatic and phenolic hydroxyl contents. The rotary‐milled sample on the other hand had a much lower β‐O‐4′ and hydroxyl content along with a higher degree of condensation and oxidized side chain structures.

Keywords:

• Lignin
• characterization
• quantitative ¹³C NMR
• milled wood lignin (MWL)
• vibratory ball‐milling
• rotary ball‐milling

This article is dedicated to the memory of Professor Josef S. Gratzl.