Effects of pretreatment using H₂SO₄and torrefaction temperature of oil palm empty fruit bunches and corn cobs on their thermogravimetric characteristics

Biomass waste of oil palm empty fruit bunches (OPEFB) and corn cobs is very abundant due to vast oil palm plantation and corn planting in Indonesia. OPEFB and corn cobs are good sources of cellulose because it composes about one third of their mass. Cellulose can be converted to levoglucosan as a platform chemical. High yield of levoglucosan obtained from fast pyrolysis may be achieved if the feed to the fast pyrolysis has been undergone pretreatment to reduce alkaline and alkaline-earth minerals (AAEM) content and to improve cellulose composition. In the present work, two successive pretreatment methods were applied to OPEFB and corn cobs, namely pretreatment with H2SO4 and torrefaction, to study their effect on the derivative thermogravimetric (DTG) curves of the biomass to estimate optimum conditions for the fast pyrolysis leading to the highest levoglucosan yield. The parameters in the present study are the percentage of weight ratio of H2SO4 to biomass varied 1, 3, 5, 7 wt.% for demineralization processes, and the torrefaction temperature varied 120, 160, 200, 240 °C to maximize cellulose content. The results show that 3 wt.% H2SO4 is the lowest required to remove most of AAEM in the biomass. Data of DTG of OPEFB pretreated with 1 and 7 wt% H2SO4 that to obtain highest yields of levoglucosan, torrefaction stage should be operated at 200oC and 120oC, respectively. Additionally, data of DTG of corn cobs pretreated with 1 wt % H2SO4 to achieved highest yield of levoglucosan, torrefaction should be run at 120oC. On the other hands, data of DTG of corn cobs pretreated with 7 wt % H2SO4 indicates the excessive use of the acid resulting in the absence of crystalline cellulose and therefore it is unlikely to produce high yield of levoglucosan.