Hydrolysis Rate of Pentosan of Hardwood in Dilute Sulfuric Acid

Abstract

In order to find the optimum condition of pre-hydrolysis of hardwood, the hydrolysis rates of pentosan of Buna (Fagus crenala Blutne) have been measured in 1, 2, 4, 8 and 16 percent sulfuric acid, their temperatures at 74, 100, 115, 130 and 147°C. The results show that the hy-drolysis of Buna wood pentosan consists of two stages. The first-order reaction constant of pentosan hydrolysis in the first stage is greater than that of the second stage. The equations describing the rates of hydrolysis of Buna wood pentosan in both stages are shown as follows:
kA=2.56×l0¹⁵C^1.15 exp{-30900/(RT)}
kR=5.57×l0¹⁵C^1.15 exp{-30900/(RT)}
where kA and kR are first-order reaction canstants involved in the first and the second stages respectively, C is the percentage concentration of sulfuric acid, R is the molar gas constant, and T is the absolute temperature. The values of activation energy of reactions in both stages are of the same magnitude and the constant values describing the effect of acid concentration are also the same. The liquid-solid ratio over the range tested (8:1_??_16:1) has little effect on the velocity of the reaction. Two samples, the sawdust and the shaving, which differ in size are hydrolyzed at the same rate.