Upgraded production of (1R,5S)-1-hydroxy-3,6-dioxa-bicyclo[3.2.1]octan-2-one from cellulose catalytic pyrolysis and its detection in bio-oils by spectroscopic methods

Abstract

Catalytic pyrolysis of cellulose was carried out focusing on the selective production of the anhydrosugar (1R,5S)-1-hydroxy-3,6-dioxa-bicyclo[3.2.1]octan-2-one (LAC), a promising chiral chemical for application in organic synthesis. The catalyst Sn-MCM-41, montmorillonite K10 or aluminum titanate nanopowder was used by a suitable pyrolysis reactor performing the processes at 500°C and 350°C. After a workup adapted to optimize the production of LAC and to facilitate the following purification, its amount in the produced bio-oil samples was established by 1H NMR spectroscopy using the standard-addition method. A further quantitative analysis was based on FT-IR technique performed using a CaF2 liquid cell and employing the calibration-curve method. Both the methods, which do not require any pre-treatment steps, provided comparable values (±1%) in terms of LAC abundance in bio-oil samples and validation of the FT-IR based method made it a rapid and efficient tool for quantitative LAC detection also without need of carbonyl band deconvolution. The data showed that (i) Sn-MCM-41 promoted the highest LAC production by pyrolysis at 500°C (7.6±0.1wt.% from cellulose), with a lower than 1% decrease in the presence of this catalyst after a regeneration cycle, and (ii) the cheap and eco-friendly montmorillonite K10 emerged as the best alternative, with a yield from cellulose of 4.8±0.1wt.% at 500°C and 4.6±0.1wt.% at 350°C.