(718d) Simulation Study of Ozone Pretreatment of Wheat Straw with Experimental Validations

Authors: 
Bhattarai, S. - Presenter, Washington State University
Gao, A., Washington State University
Chen, S., Washington State University
Ivory, C. F., Washington State University

The pretreatment is essential prior to enzymatic hydrolysis to alter the structure of the lignocellulosic biomass and to facilitate the access of the enzymes. Ozonation has been considered as an pretreatment option because of its ability in reacting with lignin.  Ozone pretreatment has a number of advantages over other pretreatment techniques. Ozonation can be performed in room temperature under ambient pressure conditions. Proper ozone treatment not only can selectively remove lignin without cellulose degradation but also produces no toxic compounds to the downstream processes.  Development of numerical models can help detailed studies of ozone lignin interaction. This paper presents novel mathematical models for simulating transient process of pretreatment of wheat straw with ozone. The models are based on mass conservation of the ozone in the reactor, ozone dissipated inside the solid, soluble lignin content and insoluble lignin content. The models were all ordinary differential equations, which can be solved easily in the Matlab computer program using ode solvers. For the purpose of validation of the proposed models, experiments were performed. Insoluble and soluble lignin content was measured experimentally at a pretreatment time of 0, 1, 2, 3, 5, 10, 15, 20, 30 and 60 min. The extractives content in the ozone treated wheat straw was experimentally determined by the use of Soxlet extraction. The test results showed that insoluble lignin content decreased significantly with increasing ozone pretreatment and stabilized after 30 min. However, soluble lignin content increased for the first 10 min, and thereafter gradually decreased and stabilized after 30 minutes. Extractive contents also increased significantly in the pretreated samples. Good agreement was found between the measured and the predicted data (R2>0.9). In conclusion, the developed model can be used for the study of ozonolysis process for the pretreatment of lignocellulosic materials when using fixed bed reactor.