The production of furfural from sunflower husks using the s-suprayield process.

Abstract

Since the early 1920s, when furfural was first produced, several other processing routes have been developed but none have been able to produce yields comparable to those obtained in the standard TAPPI procedure for xylan which almost completely converts xylan to furfural.

Karl Zeitsch, a German chemist, believed that the key feature of a process which could achieve high yields was rapid removal of the furfural on formation. Zeitsch suggested using gas phase HCl catalysis to produce gaseous furfural from xylan containing material, the process was titled s-Suprayield.

The experimental apparatus heated a water and HCl solution to a superheated vapour phase and then allowed for contact of the vapour and a bed of pentosan-containing material (in this case sunflower husks). The raw material was analysed by the TAPPI procedure for xylose while the product solutions were analysed for HCl, acetic acid and furfural by titration and refractive index.

Tests were performed at four acid concentrations of 0.5, 1.1, 2.2, 4.3% wt and three different temperatures viz. 163ºC, 152 ºC and 144 ºC. The best yields of over 80% were achieved when an acid concentration of 4.3% was used. Temperature did not appear to be as significant a factor as acid concentration in affecting the furfural yield. At an acid concentration of 0.5% the yield was low ranging from 33% to 42%.

The reactor modelling was used to verify the results.

The s-Suprayield process has been demonstrated to be successful at mini-pilot plant scale indicating that a process using gaseous catalysis to produce furfural at moderate temperatures and low acid concentrations can work and that further exploration of this process should be undertaken for potential industrial use. Acid concentration was observed to have a significant effect on the reaction yield while the effect of temperature was not clear from the experimental results.

Further work should focus on understanding the reaction kinetic and the development of a laboratory scale test method for which parameters such as gas flow rate and temperature can be properly controlled. Product analysis should be more rigorous with the use of an HPLC.