A Study About Pretreatment Of Corncob Using Organic Acids And Utilization Of Its Main Components

China was one of the largest corn producers in the world,with consistently high production and planted area.Corncobs,a major by-product of corn,were a valuable source of biomass energy.However,their primary usage as a low-value fuel for heat energy through direct combustion led to inefficient use of biomass resources and negatively impacted the environment.Therefore,developing new high-value utilization methods for corncobs became a significant area of focus in the field of biomass energy research.This thesis proposed several methods to achieve a full-component integrated utilization of corncobs through pretreatment.The specific details of the study were outlined below:In the first part,the process involved the pretreatment of corncobs using p-Ts OH,which is a fully recoverable organic acid.The solid and liquid phases were separated after pretreatment,and the solid phase was subjected to short ultrasonication(10s)to obtain free fibres,which were then mixed with commercial soft wood pulp.The pretreatment solution,containing mainly organic acids,lignin,and hemicellulose degradation products,was precipitated using an anti-solvent to obtain the lignin fraction.The lignin fraction was then hydrogenated and depolymerised to produce bio-oil.The hemicellulose degradation products were converted to furfural by the direct catalytic action of the acid catalyst.The results of the study revealed that the pretreatment conditions involving an acid concentration(Cx)of 70 wt.%,a pretreatment temperature(Tx)of 70°C,and a pretreatment time(tx)of 30 min achieved hemicellulose and lignin removal rates of 73.90%and 90.25%,respectively.The addition of corncob fiber at a level of 20% increased the ring crush index and tensile index of the handsheets by 2.68% and 10.61%,respectively,when compared to pure soft wood pulp.The lignin obtained was depolymerised by hydrogenation to achieve a 68% yield of phenolic compound monomers.The highest conversion of furfural was achieved at 130°C with 53.65%.In the second part,the process involved the pretreatment of corncobs using Maleic acid.Following solid-liquid separation,the solid phase was exposed to short-time ultrasonication(10s)to generate free fibers that were then mixed with commercial soft wood pulp.The pretreatment solution,predominantly containing organic acids,lignin,and hemicellulose degradation products,was subjected to inverse solvent precipitation to obtain the lignin fraction.This fraction was hydrogenated and depolymerized to create bio-oil.The hemicellulose degradation products were directly converted to furfural,a platform chemical,through the catalytic action of organic acids.The study revealed that under C70T90t60 conditions,the hemicellulose and lignin removal rates achieved 85.84%and 81.51%,respectively.At a 20% corncob pulp addition,the handsheets’ ring crush,tear,and tensile indices increased by 26.35%,66.52%,and 33.48%,respectively,compared to pure soft wood pulp.The lignin obtained was depolymerized by hydrogenation,with a high monomer yield of 81% of phenolic compounds.The extracted acid-soluble lignin was prepared as uniformly sized lignin nanospheres with a particle size distribution concentrated between 100-1000 nm.Moreover,the addition of lignin nanospheres to commercial sunscreens with SPF15 at a concentration of 4 wt.% showed a significant improvement in sun protection by 83.89% and 48.11% compared to commercial sunscreens with SPF30 and SPF50,respectively.The optimal temperature for furfural conversion was 170°C with a maximum conversion rate of 60.28%.In the third section,corncobs were initially subjected to pretreatment using hightemperature liquid water.After solid-liquid separation,the solid phase was converted into pulp using a high consistency mill and was then mixed with commercial soft wood pulp.The hemicellulose degradation products in the pretreatment solution were transformed into furfural using a recoverable solid acid as a catalyst.Under 155°C,a hemicellulose removal rate of 56.11% was achieved.Compared to pure soft wood pulp,the ring crush,tear,and tensile indices of handsheets were increased by 31.9%,31.75%,and 7.56%,respectively,with the addition of 15% corncob pulp.In addition,by grafting the corn cob fibres with sulphonic acid groups to increase their hydrophilicity,the water retention value of the corn cob pulp increased by 49.35% at T80t60.The modified hydrophilic fibers were combined with commercial soft wood pulp using the multilayer web copying technique,and the ring crush,tear,and tensile indices of the handsheets were improved by 42.23%,118%,and 77.34%,respectively.Yield of furfural reaching up to 52.35%.In conclusion,the proposed approach for the pretreatment and utilization of corn cobs has accomplished the comprehensive utilization of all components present in the corn cob biomass.Specifically,the hemicellulose fraction is transformed into furfural,a platform chemical,the lignin fraction is converted into aromatic monomers,and the cellulose fraction is processed into pulp suitable for industrial paper production.Additionally,the utilized organic acid/solid acid catalysts can be fully recovered,thereby offering environmental benefits.This study carries significant implications for the comprehensive utilization of herbaceous agricultural solid waste.