Kinetics of acid hydrolysis of hardwood in a continuous plug flow reactor
This thesis was undertaken to investigate the kinetics of dilute acid catalyzed hydrolysis of hardwood in an isothermally operated continuous plug flow reactor at steady state. Sulphuric acid catalyst concentration ranged from 0.05 to 2.5 wt% and the reaction temperatures were between 160/sup 0/C and 265/sup 0/C. The residence time was limited to between 0.1 and 0.5 minutes while the wood slurry concentration varied from 5 wt% to 10 wt%. Kinetic models, as functions of the reaction conditions, were obtained for the hemicelluloses (xylan) to xylose, xylose to furfural, fufural decomposition, and cellulose (glucan) to glucose reactions. Numerical solutions (Runge-Kutta Methods) to a system of first order differential equations which provided a composite description of the kinetic model for furfural production from xylan were also presented. Furfural yields of up to 87% were verified. Xylose appearance from hardwood xylan could be modelled by a sequence of two irreversible consecutive first-order reactions. The proposed model, however, underestimated xylose yields at the conditions of quantitative yields (1 wt% 2 wt%, 0.25 minutes and 190/sup 0/C to 210/sup 0/C). For the cellulose to glucose reaction, a similar model with different parameters produced yields of up to 56% at 240/sup 0/C to 260/sup 0/C. Two approaches for the carbohydrate recovery and utilization in acid hydrolysis were proposed as follows. 1) Two-stage hydrolysis: in this mode, the first stage is at the conditions for maximum xylose recovery. This is then followed by a second-stage hydrolysis at higher temperatures for glucose recovery. 2) Single-stage hydrolysis: since the conditions for high furfural yields coincide with those for glucose, a single stage hydrolysis for their simultaneous recovery can also be achieved.
- OSTI ID:
- 6378728
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
140504* -- Solar Energy Conversion-- Biomass Production & Conversion-- (-1989)
ACID HYDROLYSIS
ALDEHYDES
CARBOHYDRATES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMICAL REACTORS
DECOMPOSITION
FURANS
FURFURAL
GLUCOSE
HETEROCYCLIC COMPOUNDS
HEXOSES
HIGH TEMPERATURE
HYDROGEN COMPOUNDS
HYDROLYSIS
INORGANIC ACIDS
KINETICS
LYSIS
MATHEMATICAL MODELS
MONOSACCHARIDES
NUMERICAL SOLUTION
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PENTOSES
PRODUCTION
PRODUCTIVITY
QUANTITY RATIO
REACTION KINETICS
SACCHARIDES
SOLVOLYSIS
SULFURIC ACID
WOOD
XYLOSE