INFLUENCE OF METAL-IONS AND OF SALTS ON PRODUCTS FROM PYROLYSIS OF WOOD - APPLICATIONS TO THERMOCHEMICAL PROCESSING OF NEWSPRINT AND BIOMASS

Several different individual metal ions have been incorporated into cottonwood by ion exchange and the products of vacuum pyrolysis have been investigated. K, Li and Ca induced formation of high char and low tar yields, the latter being very low in levoglucosan (LG, 1). In contrast, all of the other ions investigated (especially the transition metals) gave increased yields of LG, up to 15.8% from wood exchanged with ferrous ions, corresponding to 32% conversion of cellulose to LG. When salts were sorbed into the wood (instead of ion exchanged) smaller, but still major increases in LG yield were again obtained, especially when indigenous salts in the wood were first removed by acid washing. With sorbed salts the effect of the anion was investigated. Wood sorbed with acetate salts behaved similarly to ion-exchanged wood, and chlorides (especially of Cu and Fe) were also beneficial in terms of LG yield. With low levels of sorbed FeSO4 in wood the formation of both LG and levoglucosenone (LGO, 2) was catalyzed. Similar advantageous effects were observed with newsprint sorbed with FeSO4, which yielded 17.2% of LG and 3.7% of LGO as well as other significant products. The possible mechanisms of these effects are discussed. A coordinated approach to the chemical utilization of lignocellulosic biomass is foreshadowed, whereby ions such as Fe or Cu are incorporated into the biomass to catalyze pyrolytic production of LG and/or LGO, while at the same time generating an increased yield of charcoal. The latter also has the added potential benefit that it now contains an efficient gasification catalyst.