Chemical pre-treatment such as alkaline (KOH and NaOH) and acid (H2SO4) pre­treatments are carried out in this study. Further study is done where three differently pretreated OPF samples were subjected to sodium chlorite delignification. Lignin content in these three pretreated OPF samples are compared before and after sodium chloride delignification. Alkali pre-treatment assists in the hydrolysis of lignin. The best performance is indicated by the lowest percentage of total lignin content re­mained in the sample after treatment. Study indicated that NaOH pre-treatment coupled with chlorite delignification gave the best performance on lignin removal among the different pre-treatment methods applied, with the lowest total lignin con­tent remained in the sample which accounted for 19.32 % whereby total lignin content in untreated sample was found to have 30.78 % as shown in Fig. 17.4. Chlorite delig — nification can partially remove lignin from biomass [74]. The chlorite treatment was more effective than the organosolv method, as 2.5 % of lignin was left in chlorite treated barley husks as compared to 3.9 % in organosolv treated barley husks [74].

The treated OPF and untreated OPF is subjected to steam and gasified at tem­perature higher than 500 °C. For all experiments, biomass sample weight was approximately 5 mg. N2 was used as inert carrier gas with a constant flow rate of 100ml/min. The micro vacuum pump (650mmHg was applied throughout the experiments) was attached to the gas chromatography (GC) to facilitate gaseous product from thermogravimetric analysis (TGA). Steam was generated by super heater up to 400 °C prior to injection in TGA. The system was purged with N2 gas (100 ml/min) for about 20 min to remove entrapped gases at temperature of 50 °C. All samples were heated at a constant heating rate of 20 °C/min from 50 to 900 °C where it was kept constant for 10 min. To avoid condensation, steam was introduced when temperature inside the TGA reached to 110 °C. The amount of catalyst used was based on biomass-to-catalyst ratio of 3 (mass basis), while steam-to-biomass was kept constant at 1:1 ratio (mass basis). The apparatus used is shown in Fig. 17.5. The biomass steam gasification experiments were performed in a standard TGA (EXS­TAR TG/DTA 6300, from SII) and GC (Agilent 7890A, Agilent Technologies) under non-isothermal conditions.

Balance beam

Fig. 17.5 Experimental Apparatus

Results from TGA-GC analysis reveal that NaOH coupled with chlorite treated OPF was able to produce higher yield of H2 (56.56 vol%) compared to untreated dried OPF (39.48 vol%) as shown in Fig. 17.6. On the other hand, H2 can be produced at a much lower temperature of 550 °C instead of 850 °C if the OPF is treated with NaOH coupled with chlorite; hence, the chemical pre-treatment has improved the biomass quality.