The liquefaction of powdered rice straw, suspended in an aqueous solution of sodium carbonate or potassium carbonate as a catalyst, was examined at temperatures ranging from 250 to 376°C, and with reaction times 0, 30 and 60 min. by using a convenient small-sized tubing-bomb as a reactor. Separation procedure of the reaction mixtures is demonstrated in Fig. 1.
The effect of reaction temperature on the yield of products, using sodium carbonate, is shown with different reaction times in Fig. 2. The oleaginous substance O-1 and O-2 are the major parts of the liquefaction products. The whole oily products, the sum of O-1, O-2, O-3 and O-4, increase with the rise in temperature until 350°C, ranging from 6% (250°C, 0min.) to 27% (350°C, 60min.) of the original weight of rice straw, while the case at 376°C, a super-critical temperature of water, is exceptional.
Similarly, the temperature-dependence of the yield of products, using potassium carbonate, is shown in Fig. 3, with different reaction times. The yield of main oily product O -1 increases with the rise in reaction temperature. Potassium carbonate is slightly better than sodium carbonate as a catalyst.(Fig. 4)
The effect of addition of organic solvent, e. g. acetone, on the yield of main oily product O-1 is shown in Fig. 5.
The yields, elementary compositions and heating values of oily products O-1 and O -2, which obtained under various reaction conditions, are listed in Table 1.