Pyrolysis of Napier grass to bio-oil and catalytic upgrading to high grade bio-fuel

Biomass is one of the renewable energy resources that has carbon in its building blocks that can be processed into liquid fuel. Napier grass biomass is a herbaceous lignocellulosic material with potentials of high biomass yield. Utilization of Napier grass for bio-oil production via pyrolysis is very limited. Bio-oil generally has poor physicochemical properties such as low pH value, high water content, poor chemical and thermal stabilities which makes it unsuitable for direct use as fuel and therefore requires further processing. Upgrading of bio-oil to liquid fuel is still at early stage of research. Several studies are being carried out to upgrade bio-oil to transportation fuel. However, issues regarding reaction mechanisms and catalyst deactivation amongst others remain a challenge. This thesis gives insights and understanding of conversion of Napier grass biomass to liquid biofuel. The material was assessed as received and characterized using standard techniques. Pyrolysis was conducted in a fixed bed reactor and effect of pyrolysis temperature, nitrogen flow rate and heating rate on product distribution and characteristics were investigated collectively and pyrolysis products characterized. Effects of different aqueous pre-treatments on the pyrolysis product distribution and characteristics was evaluated. Subsequently, in-situ catalytic and non-catalytic, and ex-situ catalytic upgrading of bio-oil derived from Napier grass using Zeolite based catalysts (microporous and mesoporous) were investigated. Upgraded bio-oil was further fractionated in a micro-laboratory distillation apparatus. The experimental results showed that high bio-oil yield up to 51 wt% can be obtained from intermediate pyrolysis of Napier grass at 600 oC, 50 oC/min and 5 L/min nitrogen flow in a fixed bed reactor. The bio-oil collected was a two-phase liquid, organic (16 wt%) and aqueous (35 wt%) phase. The organic phase consists mainly of various benzene derivatives and hydrocarbons while the aqueous phase was predominantly water, acids, ketones, aldehydes and some phenolics and other water-soluble organics. Non-condensable gas (29 wt%) was made-up of methane, hydrogen, carbon monoxide and carbon dioxide with high hydrogen/carbon monoxide ratio. Bio-char (20 wt%) was a porous carbonaceous material, rich in mineral elements. Aqueous pre-treatment of Napier grass with deionized water at severity factor of 0.9 reduced ash content by 64 wt% and produced bio-oil with 71 % reduction in acid and ketones. Performance of mesoporous zeolites during both in-situ and ex-situ upgrading outweighed that of microporous zeolite, producing less solid and highly deoxygenated organic bio-oil rich in alkanes and monoaromatic hydrocarbons. The Upgraded bio-oil produced 38 wt% light fraction, 48 wt% middle distillate and 7.0wt% bottom product. This study demonstrated that bio-oil derived from Napier grass can be transformed to that high-grade bio-oil via catalytic upgrading over hierarchical mesoporous zeolite

Pyrolysis of Napier grass to bio-oil and catalytic upgrading to high grade bio-fuel

Biomass is one of the renewable energy resources that has carbon in its building blocks that can be processed into liquid fuel. Napier grass biomass is a herbaceous lignocellulosic material with potentials of high biomass yield. Utilization of Napier grass for bio-oil production via pyrolysis is very limited. Bio-oil generally has poor physicochemical properties such as low pH value, high water content, poor chemical and thermal stabilities which makes it unsuitable for direct use as fuel and therefore requires further processing. Upgrading of bio-oil to liquid fuel is still at early stage of research. Several studies are being carried out to upgrade bio-oil to transportation fuel. However, issues regarding reaction mechanisms and catalyst deactivation amongst others remain a challenge. This thesis gives insights and understanding of conversion of Napier grass biomass to liquid biofuel. The material was assessed as received and characterized using standard techniques. Pyrolysis was conducted in a fixed bed reactor and effect of pyrolysis temperature, nitrogen flow rate and heating rate on product distribution and characteristics were investigated collectively and pyrolysis products characterized. Effects of different aqueous pre-treatments on the pyrolysis product distribution and characteristics was evaluated. Subsequently, in-situ catalytic and non-catalytic, and ex-situ catalytic upgrading of bio-oil derived from Napier grass using Zeolite based catalysts (microporous and mesoporous) were investigated. Upgraded bio-oil was further fractionated in a micro-laboratory distillation apparatus. The experimental results showed that high bio-oil yield up to 51 wt% can be obtained from intermediate pyrolysis of Napier grass at 600 oC, 50 oC/min and 5 L/min nitrogen flow in a fixed bed reactor. The bio-oil collected was a two-phase liquid, organic (16 wt%) and aqueous (35 wt%) phase. The organic phase consists mainly of various benzene derivatives and hydrocarbons while the aqueous phase was predominantly water, acids, ketones, aldehydes and some phenolics and other water-soluble organics. Non-condensable gas (29 wt%) was made-up of methane, hydrogen, carbon monoxide and carbon dioxide with high hydrogen/carbon monoxide ratio. Bio-char (20 wt%) was a porous carbonaceous material, rich in mineral elements. Aqueous pre-treatment of Napier grass with deionized water at severity factor of 0.9 reduced ash content by 64 wt% and produced bio-oil with 71 % reduction in acid and ketones. Performance of mesoporous zeolites during both in-situ and ex-situ upgrading outweighed that of microporous zeolite, producing less solid and highly deoxygenated organic bio-oil rich in alkanes and monoaromatic hydrocarbons. The Upgraded bio-oil produced 38 wt% light fraction, 48 wt% middle distillate and 7.0wt% bottom product. This study demonstrated that bio-oil derived from Napier grass can be transformed to that high-grade bio-oil via catalytic upgrading over hierarchical mesoporous zeolite

Catalytic Intermediate Pyrolysis of Napier Grass in a Fixed Bed Reactor with ZSM-5, HZSM-5 and Zinc-Exchanged Zeolite-A as the Catalyst

The environmental impact from the use of fossil fuel cum depletion of the known fossil oil reserves has led to increasing interest in liquid biofuels made from renewable biomass. This study presents the first experimental report on the catalytic pyrolysis of Napier grass, an underutilized biomass source, using ZSM-5, 0.3HZSM-5 and zinc exchanged zeolite-A catalyst. Pyrolysis was conducted in fixed bed reactor at 600˝C, 30˝C/min and 7 L/min nitrogen flow rate. The effect of catalyst-biomass ratio was evaluated with respect to pyrolysis oil yield and composition. Increasing the catalyst loading from 0.5 to 1.0 wt % showed no significant decrease in the bio-oil yield, particularly, the organic phase and thereafter decreased at catalyst loadings of 2.0 and 3.0 wt %. Standard analytical methods were used to establish the composition of the pyrolysis oil, which was made up of various aliphatic hydrocarbons, aromatics and other valuable chemicals and varied greatly with the surface acidity and pore characteristics of the individual catalysts. This study has demonstrated that pyrolysis oil with high fuel quality and value added chemicals can be produced from pyrolysis of Napier grass over acidic zeolite based catalysts

Valorization of Bambara groundnut shell via intermediate pyrolysis: Products distribution and characterization

This study provides first report on thermochemical conversion of residue from one of the underutilized crops, Bambara groundnut. Shells from two Bambara groundnut landraces KARO and EX-SOKOTO were used. Pyrolysis was conducted in a vertical fixed bed reactor at 500, 550, 600 and 650 o�C; 50 o�C/min heating rate and 5 L/min nitrogen flow rate. The report gives experimental results on characteristic of the feedstock, impact of temperature on the pyrolysis product distribution (bio-oil, bio-char and noncondensable gas). It evaluates the chemical and physicochemical properties of bio-oil, characteristics of bio-char and composition of the non-condensable gas using standard analytical techniques. KARO shell produced more bio-oil and was maximum at 600 o�C (37.21 wt%) compared to EX-SOKOTO with the highest bio-oil yield of 32.79 wt% under the same condition. Two-phase bio-oil (organic and aqueous) was collected and analyzed. The organic phase from both feedstocks was made up of benzene derivatives which can be used as a precursor for quality biofuel production while the aqueous from KARO consisted sugars and other valuable chemicals compared to the aqueous phase from EX-SOKOTO which comprised of acids, ketones, aldehydes and phenols. Characteristics of bio-char and composition of the noncondensable were also determined. The results show that bio-char is rich in carbon and some minerals which can be utilized either as a solid fuel or source of bio-fertilizer. The non-condensable gas was made up of methane, hydrogen, carbon monoxide and carbon dioxide, which can be recycled to the reactor as a carrier gas. This study demonstrated recovery of high quality fuel precursor and other valuable materials from Bambara groundnut shell

Thermogravimetric study and evolved gas analysis of new microalga using TGA-GC-MS

The growing concerns over the environmental challenges emanating from the use of fossil fuels continue to generate interest in finding competitive and sustainable alternatives. This study presents physicochemical characteristics, thermal decomposition profile and kinetics of a new Botryococcus sp. of microalga isolated from Endau-Rompin, Malaysia. The proximate and ultimate analyses were carried out using standard analytical techniques. Thermogravimetric study was conducted in nitrogen atmosphere using a thermogravimetric analyser coupled with gas chromatography-mass spectrometer. The result revealed that the feedstock has high volatile matter (86.74 wt%) and calorific value of 17.18 MJ/kg. The thermal decomposition of the alga sample proceeded via dehydration, decomposition of extractives, hemicellulose, other carbohydrates and lipid evaporation. The kinetics of the alga sample evaluated using a distributed activation energy model showed that the model sufficiently described the pyrolysis of the feedstock with activation energy of 52.72–159.16 kJ/mol. The chemical composition of the evolved gas revealed high content of hydrocarbons, products of carbohydrate and protein decomposition. This suggests that the alga sample is a good candidate for production of valuable precursors for biofuel processing and production of biochemicals

Novel input-output prediction approach for biomass pyrolysis

Biomass pyrolysis to bio-oil is one of the promising sustainable fuels. In this work, relation between biomass feedstock element characteristic and pyrolysis process outputs was explored. The element characteristics considered in this study include moisture, ash, fix carbon, volatile matter, carbon, hydrogen, nitrogen, oxygen, and sulphur. A semi-batch fixed bed reactor was used for biomass pyrolysis with heating rate of 30 °C/min from room temperature to 600 °C and the reactor was held at 600 °C for 1 h before cooling down. Constant nitrogen flow rate of 5 L/min was provided for anaerobic condition. Rice husk, Sago biomass and Napier grass were used in the study to form different element characteristic of feedstock by altering mixing ratio. Comparison between each element characteristic to total produced bio-oil yield, aqueous phase bio-oil yield, organic phase bio-oil yield, higher heating value of organic phase bio-oil, and organic bio-oil compounds was conducted. The results demonstrate that process performance is associated with feedstock properties, which can be used as a platform to access the process feedstock element acceptance range to estimate the process outputs. Ultimately, this work evaluated the element acceptance range for proposed biomass pyrolysis technology to integrate alternative biomass species feedstock based on element characteristic to enhance the flexibility of feedstock selection

Element characteristic tolerance for semi-batch fixed bed biomass pyrolysis

Biomass pyrolysis to bio-oil is one of the promising sustainable fuels. In this work, relation between biomass feedstock element characteristic and crude bio-oil production yield and lower heating value was explored. The element characteristics considered in this study include moisture, ash, fix carbon, volatile matter, C, H, N, O, S, cellulose, hemicellulose, and lignin content. A semi-batch fixed bed reactor was used for biomass pyrolysis with heating rate of 30 °C/min from room temperature to 600 °C and the reactor was held at 600 °C for 1 h before cooling down. Constant nitrogen flow (1bar) was provided for anaerobic condition. Sago and Napier glass were used in the study to create different element characteristic of feedstock by altering mixing ratio. Comparison between each element characteristic to crude bio-oil yield and low heating value was conducted. The result suggested potential key element characteristic for pyrolysis and provide a platform to access the feedstock element acceptance range

Upgrading of Napier grass pyrolytic oil using microporous and hierarchical mesoporous zeolites: products distribution, composition and reaction pathways

Reaction pathways in ex-situ catalytic upgrading of pyrolytic oil towards formation of specific products such as hydrocarbons are still not well established due to the presence of many different organic components in the raw pyrolytic oil. Currently, only a few studies are available in literature particularly with regards to application of hierarchical mesoporous zeolite in the refinement of sample pyrolytic oil. This study provides the first experimental investigation of ex-situ catalytic upgrading of pyrolytic oil derived from Napier grass using microporous and hierarchical mesoporous zeolites. Two hierarchical mesoporous zeolites were synthesized by desilication of microporous zeolite using 0.2 and 0.3 M solution of sodium hydroxide. Upgrading over microporous zeolite produced 16.0 wt% solid, 27.2 wt% organic phase and 23.9 wt% aqueous phase liquid while modified zeolites produced 21e42% less solid and 15e16% higher organic phase liquid. Higher degree of deoxygenation of pyrolytic oil was achieved with the modified zeolites. Analysis of organic phase collected after catalytic upgrading revealed high transformation of oxygenates into valuable products. Bulk zeolite produced cyclic olefins and polyaromatic hydrocarbons while mesoporous zeolites were selective toward cycloalkanes and alkylated monoaromatic production, with significant reduction in the production of polyaromatic hydrocarbon. Result of gas analysis showed that hierarchical mesoporous zeolite favoured decarboxylation and decarbonylation reactions compared to the parent zeolite, which promoted dehydration reaction. Mesoporous zeolite produced with 0.3 M sodium hydroxide solution was found to be the best-performing catalyst and its reusability was tested over four consecutive cycles. This study demonstrated that pyrolytic oil derived from Napier grass can be transformed into high-grade oil over hierarchical mesoporous zeolite

Insight into catalyst deactivation mechanism and suppression techniques in thermocatalytic deoxygenation of bio-oil over zeolites

The economic viability of the thermocatalytic upgrade of biomass-derived oxygenates is facing the challenge of low-quality products. This is because of leaching of active species, coking, and concomitant catalyst deactivation. These cumulate into the loss of catalytic activity with time on stream (TOS), which causes low degree of deoxygenation. Thus, this article reviews recent advances aimed at alleviating these setbacks to make the process viable for industrial scale-up. To understand the concept of catalyst deactivation and to offer solutions, the review scrutinized the deactivation mechanism diligently. The review also analyzes deactivation-suppression techniques such as nanocrystal zeolite cracking, hydrogen spilt-over (HSO) species, and composite catalysts (hybrid, hierarchical mesoporous zeolite, modified zeolites, and catalytic cracking deposition of silane). Interestingly, these deactivation- suppression techniques enhance catalytic properties mostly by reducing the signal strength of strong acid sites and increasing hydrothermal stability. Further, the approaches improve catalytic activity, selectivity, and TOS stability because of the lower formation of coke precursors such as polynuclear aromatics. However, despite these many advances, the need for further investigations to achieve excellent catalytic activity for industrial scaleup persists

Fatty Acids Composition of Microalga Botryococcus Sp. Cultured in Synthetic Medium

In response to the crisis of fossil fuel depletion and global climate change, microalgae cultivation has received significant attention as an alternative to sustainable biodiesel production.  In this study, the total fatty acids content was quantified from Botryococcus sp biomass grown in synthetic medium Bold Basal Medium (BBM) under laboratory conditions. The microalgal biomass was harvested through centrifugation in the late logarithmic growth phase and then it was freeze-dried at -40oC and 0.12 Mbar for 86400 s (24 hrs). The lipids were extracted following Soxhlet method, and the fatty acids were analyzed using GC–MS. From the results obtained, the fatty acid composition is; C16:0 (Palmitic acid) contributing 27.950%, followed by C18:3 (stearic acid 22.758%), followed by C 18:2 (linoleic acid17.046) and the lowest is C 15:1 (pentadecanoic acid) with 0.051%. Most of the fatty acids obtained are both saturated and unsaturated which are similar to the conventional biodiesel and diesel properties making this green microalga Botryococcus sp.  a desirable feedstock for biodiesel production. Thus, this locally isolated Botryococcus sp. has a high potential to be used as a source of biodiesel in the future