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Title:	Acid hydrolysis of pretreated oil palm empty fruit bunch fibre to produce fine chemicals
Authors:	Chin Siew Xian (P62845 )
Keywords:	Biomass chemicals.
Issue Date:	2015
Description:	Lignocellulosic biomass constitutes a major class of carbon-neutral energy resources, which can be used to produce value-added fine chemicals. Oil palm empty fruit bunch (EFB) is one of the by-products generated during palm oil extraction process. Complex matrix of lignocellulosic biomass has becomes a challenge in the conversion process to produce fine chemicals via acid hydrolysis. Therefore, lignocellulosic raw materials must be pretreated. The goal of this work is to investigate the effect of pretreatment (chemical and physical), on the efficiency of the conversion of the EFB fibres to different fine chemicals. Alkaline and bleaching pretreatments were carried out to obtain cellulose from EFB fibres, followed by acid hydrolysis to produce reducing sugar (RS) at moderate temperature and atmospheric pressure. The preliminary hydrolysis studies on the EFB fibres showed that the presence of lignin has significantly affected the RS yield. Response Surface Methodology (RSM) was used to optimize the parameter for the production of RS. The optimum yield of RS and conditions using H<sub>2</sub>SO<sub>4</sub> was 30.61%, 1.81 g/L (5N H<sub>2</sub>SO<sub>4</sub>, 139.65°C for 4.16h), for HCl was 39.81%, 2.45 g/L (4.63N HCl, 133.7°C for 2.05h). Reactions under atmospheric pressure gave low yield of RS and required long reaction time. Meanwhile, using an autoclave reaction system has proven to be more effective in the hydrolysis process. EFB fibres were also pretreated using a mild alkaline, i.e., sodium carbonate (Na<sub>2</sub>CO<sub>3</sub>) before the acid hydrolysis. The obtained result showed that the 10% total titratable alkaline (TTA) is the optimum concentration to remove lignin while preserving polysaccharides. The highest yield of RS is 62.53%, 22.7 g/L (0.25N H<sub>2</sub>SO<sub>4</sub>, 60 min at 150°C). To reduce the usage of Na<sub>2</sub>CO<sub>3</sub>, EFB fibres were pretreated using gamma ray irradiation and followed by pretreatment using Na<sub>2</sub>CO<sub>3</sub>. A synergistic effect between gamma irradiation (200 kGy) and Na<sub>2</sub>CO<sub>3</sub> (5% TTA) pretreatment was observed, in which the yield of RS is (65.03%, 23.22 g/L) (0.25N H<sub>2</sub>SO<sub>4</sub>, 60 min at 150°C), RS yield increased by 3.8% with the combination of pretreatment as compare with using sodium carbonate pretreatment alone. Ball milling was also conducted on the EFB fibres to investigate its effects on the production of levulinic acid (LA). Different durations of ball milling (0-24hr) were carried out to study its effect on the degree of crystallinity and particles size of the EFB fibres and correlating with the yield of LA. RSM was used to determine the optimum parameters to obtain LA where 0.57N H<sub>2</sub>SO<sub>4</sub> for 195.77 min at 185.98°C, resulted 10.77 g/L (53.93% based on total glucan) of LA. Kinetics of the acid hydrolysis of EFB fibres using a microwave reactor system was studied. The microwave system was chosen due to its fast hydrolysis rate and homogeneous heating; it can avoid energy-intensive pretreatment of biomass. A series of first order reactions model, (M=M<sub>0</sub> exp (-k<sub>2</sub>t) + P<sub>0</sub>(k1/(k1-k2)) (exp (-k<sub>1</sub>t)-exp (-k<sub>2</sub>t)), M<sub>0</sub> and P<sub>0</sub> are the concentration of the monomer and polymer) was developed and used to explain the kinetics and mechanism of the acid hydrolysis process. The hydrolysis kinetics of the main intermediates (potential fine chemicals), such as sugars (xylose, glucose), 5-hydroxymethylfurfural, LA and acetic acid, were found to be highly dependent on temperature and acid concentration with highest yields were 11.21 g/L (82.9% based on total xylan), 10.03 g/L (50.22% based on total glucan), 0.50 g/L, 9.27 g/L (46.42% based on total glucan) and 4.36 g/L, respectively. These kinetic parameters provide useful information and basic data for the practical use of the EFB fibres to produce fine chemicals.,Ph.D,Lignocellulosic biomass constitutes a major class of carbon-neutral energy resources, which can be used to produce value-added fine chemicals. Oil palm empty fruit bunch (EFB) is one of the by-products generated during palm oil extraction process. Complex matrix of lignocellulosic biomass has becomes a challenge in the conversion process to produce fine chemicals via acid hydrolysis. Therefore, lignocellulosic raw materials must be pretreated. The goal of this work is to investigate the effect of pretreatment (chemical and physical), on the efficiency of the conversion of the EFB fibres to different fine chemicals. Alkaline and bleaching pretreatments were carried out to obtain cellulose from EFB fibres, followed by acid hydrolysis to produce reducing sugar (RS) at moderate temperature and atmospheric pressure. The preliminary hydrolysis studies on the EFB fibres showed that the presence of lignin has significantly affected the RS yield. Response Surface Methodology (RSM) was used to optimize the parameter for the production of RS. The optimum yield of RS and conditions using H2SO4 was 30.61%, 1.81 g/L (5N H2SO4, 139.65°C for 4.16h), for HCl was 39.81%, 2.45 g/L (4.63N HCl, 133.7°C for 2.05h). Reactions under atmospheric pressure gave low yield of RS and required long reaction time. Meanwhile, using an autoclave reaction system has proven to be more effective in the hydrolysis process. EFB fibres were also pretreated using a mild alkaline, i.e., sodium carbonate (Na2CO3) before the acid hydrolysis. The obtained result showed that the 10% total titratable alkaline (TTA) is the optimum concentration to remove lignin while preserving polysaccharides. The highest yield of RS is 62.53%, 22.7 g/L (0.25N H2SO4, 60 min at 150°C). To reduce the usage of Na2CO3, EFB fibres were pretreated using gamma ray irradiation and followed by pretreatment using Na2CO3. A synergistic effect between gamma irradiation (200 kGy) and Na2CO3 (5% TTA) pretreatment was observed, in which the yield of RS is (65.03%, 23.22 g/L) (0.25N H2SO4, 60 min at 150°C), RS yield increased by 3.8% with the combination of pretreatment as compare with using sodium carbonate pretreatment alone. Ball milling was also conducted on the EFB fibres to investigate its effects on the production of levulinic acid (LA). Different durations of ball milling (0-24hr) were carried out to study its effect on the degree of crystallinity and particles size of the EFB fibres and correlating with the yield of LA. RSM was used to determine the optimum parameters to obtain LA where 0.57N H2SO4 for 195.77 min at 185.98°C, resulted 10.77 g/L (53.93% based on total glucan) of LA. Kinetics of the acid hydrolysis of EFB fibres using a microwave reactor system was studied. The microwave system was chosen due to its fast hydrolysis rate and homogeneous heating; it can avoid energy-intensive pretreatment of biomass. A series of first order reactions model, (M=M0 exp (-k2t) +P0(k1/k1-k2) (exp (-k1t)-exp (-k2t)), M0 and P0 are the concentration of the monomer and polymer) was developed and used to explain the kinetics and mechanism of the acid hydrolysis process. The hydrolysis kinetics of the main intermediates (potential fine chemicals), such as sugars (xylose, glucose), 5-hydroxymethylfurfural, LA and acetic acid, were found to be highly dependent on temperature and acid concentration with highest yields were 11.21 g/L (82.9% based on total xylan), 10.03 g/L (50.22% based on total glucan), 0.50 g/L, 9.27 g/L (46.42% based on total glucan) and 4.36 g/L, respectively. These kinetic parameters provide useful information and basic data for the practical use of the EFB fibres to produce fine chemicals.
Pages:	162
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Science and Technology / Fakulti Sains dan Teknologi

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