PRODUCTION OF FURFURAL BY DILUTE-ACID HYDROLYSIS OF WOOD - METHODS FOR CALCULATING FURFURAL YIELD

The production of furfural via dilute-acid hydrolysis of lignocellulosic materials has been unde study for many years. Furfural yield values have been reported to be 40-60% of the theoretical value in closed systems and 50-80% when furfural is rapidly removed from the reaction medium. Furfural yield calculations are simple in batch systems since the mass of wood charged is known. However when continuous units are used, these calculations become difficult because the mass flow of materia that is fed to the reactor is often unknown, or not measurable. To overcome this problem, two estimating methods have been developed: 1) an experimental approach based on output streams mass balance and assuming that input = output, and 2) a mathematical methodology leading to the estimation of feed mass flow. Results obtained by means of these methods have been compared with precise values resulting from complete mass balances. To validate the different computing methods proposed, experiments were carried out in a process development unit. The operating conditions within the tubular reactor were: H2SO4 concentration: 0.6%; slurry consistency: 6.0-6.6%; reaction temperature: 200-230 C; residence time: 95-105 sec. Results have shown that calculations based on output streams are incorrect. However, those obtained by mathematical estimation are relatively accurate and require short periods of experimental manipulations.