Products and Functional Group Distributions in Pyrolysis Oil of Chromated Copper Arsenate (CCA)-Treated Wood, as Elucidated by Gas Chromatography and a Novel ³¹P NMR-Based Method

Abstract

Low-temperature pyrolysis offers a feasible option for wood waste management and the recovery of a variety of useful chemicals. In this study, the effect of chromated copper arsenate (CCA) wood preservatives on the yield and composition of various pyrolysis products was investigated over the temperature range of 275-350 °C. For this preliminary work, we examined the feasibility of using gas chromatography coupled with either flame ionization detection or mass spectroscopic detection and a novel 31 P nuclear magnetic resonance (NMR) spectroscopic method. Both methods worked well, with the gas chromatographic method being compoundspecific and the 31 P NMR method being specific to the functional group (e.g., aliphatic alcohols, total phenols, and carboxylic acids). The present experiments showed that the CCA treatment on wood had a significant effect on the amount of main carbohydrate degradation products of tar. The yield of levoglucosan (LG) from CCA-treated wood increased, while the yields of hydroxyacetaldehyde and hydroxyacetone decreased.

Understanding the pyrolysis of CCA-treated wood

“…Wood powder pre-treated with 0.05 M CuSO 4 solution contained 0.21% Cu ions, which was similar to the Cu concentration (0.27%) in the commercially prepared CCA-treated wood [20]. Thus, in our study, 0.05 M metal compound solutions were selected to pre-treat southern pine wood powder and the pyrolysis results were compared with those from commercially prepared CCA-treated wood.…”

“…The pyrolysis of pre-treated wood samples was carried out under heat in a Kugelrohr short-path distillation apparatus [20]. The sample weight was 3 g for each trial.…”

“…Detailed signal assignments of the emerging gas chromatograms of the obtained pyrolysis tars can be located in Ref. [20].…”

“…Finally, the solution was transferred to an NMR tube for analysis. The yield of LGO in the tar was determined by 31 P NMR and the signals were assigned as per our earlier effort [20].…”

“…In our earlier effort we have demonstrated that the chromated copper arsenate (CCA) treatment of wood has a significant effect on the amount of main carbohydrate degradation products [20]. Thus, it is necessary to understand how CCA preservatives influence the distribution and yields of the pyrolysis products.…”