Fate of Lipophilic Wood Extractives in Oxygen-Based Cellulose Bleaching

Abstract

The impact of totally chlorine-free (TCF) bleaching chemicals on the composition and behavior of detrimental lipophilic wood extractives in a mixed hardwood sulfite pulp was studied to determine their potential for pitch control without the need for additional reagents. Toward this end, the acetone extracts of pulp were analyzed with commonly used gas chromatography (GC) and more sophisticated ultraperformance convergence chromatography (UPC2). During EO­(P)–Z–P bleaching, the highest decrease in the lipophilic extractive content was achieved after ozone bleaching (Z), with a 38% reduction of GC-FID/MS-detectable resins. Oxygen-reinforced alkaline extraction EO­(P) and peroxide bleaching (P) were less effective in terms of resin quality and quantity (−30 and −27%, respectively). Analyzing the acetone extracts after alkaline hydrolysis revealed a different pattern: EO­(P) with −44%, P with −20%, and Z with only −8% less lipophilic extractives. A series of oxidized compounds, such as acyl chain-oxidized sterol esters and acylglycerols, and acidic secosterol analogues, were detected for the first time with UPC2-ESI-QToF-MS after ozone bleaching. These compounds lead to an underestimation of the GC-detectable resin content and may be involved in the formation of deposits during lignocellulosic processing. Reaction pathways for lipophilic extractives during ozone bleaching were established.

Removal of wood extractives as pulp (pre-)treatment: a technological review

“…With subsequent E-O-P bleaching, they removed further 11 wt%, leaving just four wt% of the initial extractives in the bleached pulp, mainly consisting of fatty acids and sterols [133]. España Orozco et al [145] achieved comparable results with oxygen-reinforced alkaline extraction of mixed HW sulfite pulp, followed by Z and P bleaching. They decreased the gravimetric acetone extract of pulp by 68% through the TCF bleaching sequence, with oxygenreinforced alkaline extraction as the most effective stage, leaving mainly just sterols and sterol esters in the pulp.…”

Determination of the Chemical Composition of Eucalyptus spp. for Cellulosic Pulp Production

“…However, different types of extractives hinder the cellulosic pulp production in different intensities. Polar extractives are easier to remove, but non-polar extractives lead to higher removal costs [72][73][74][75]. Therefore, the focus of clone selection for the production of cellulosic pulp must be taken into account for woods that have lower concentrations of extractives.…”

Pressure agglomeration of raw, milled and cut-milled pine and poplar shavings: assessment of the compaction process and agglomerate strength

“…Production of pellets from pine wood, which is harder than poplar wood, can result in pellets with greater strength but requires higher compaction pressure (Nielsen et al 2009a). The fundamental difference between soft-and hardwoods, and between wood species in general, is the type, quantity and composition of the extractives, which include, among others, resin acids, fatty acids, fatty alcohols, sterol esters, waxes and phenols (Orozco et al 2021). Increasing the content of long-chain fatty compounds, resin acids and sterols reduces the material friction coefficient (Nielsen et al 2010) and the wood strength (Svensson et al 2006).…”