Optimization and characterization studies on bio-oil production from palm shell by pyrolysis using response surface methodology

In this work palm shell waste was pyrolyzed to produces bio-oil. The effects of several parameters on the pyrolysis efficiency were tested to identify the optimal bio-oil production conditions. The tested parameters include temperature, N₂ flow rate, feed-stock particle size, and reaction time. The experiments were conducted using a fix-bed reactor. The efficient response surface methodology (RSM), with a central composite design (CCD), were used for modeling and optimization the process parameters. The results showed that the second-order polynomial equation explains adequately the non-linear nature of the modeled response. An R² value of 0.9337 indicates a sufficient adjustment of the model with the experimental data. The optimal conditions found to be at the temperature of 500 °C, N₂ flow rate of 2 L/min, particle size of 2 mm and reaction time of 60 min and yield of bio-oil was approximately obtained 46.4 wt %. In addition, Fourier Transform infra-red (FT-IR) spectroscopy and gas chromatography/mass spectrometry (GC-MS) were used to characterize the gained bio-oil under the optimum condition.     

Production and detailed characterization of bio-oil from fast pyrolysis of palm kernel shell

Bio-oil has been produced from palm kernel shell in a fluidized bed reactor. The process conditions were optimized and the detailed characteristics of bio-oil were carried out. The higher feeding rate and higher gas flow rate attributed to higher bio-oil yield. The maximum mass fraction of biomass (57%) converted to bio-oil at 550 °C when 2 L min⁻¹ of gas and 10 g min⁻¹ of biomass were fed. The bio-oil produced up to 500 °C existed in two distinct phases, while it formed one homogeneous phase when it was produced above 500 °C. The higher heating value of bio-oil produced at 550 °C was found to be 23.48 MJ kg⁻¹. As GC–MS data shows, the area ratio of phenol is the maximum among the area ratio of identified compounds in 550 °C bio-oil. The UV–Fluorescence absorption, which is the indication of aromatic content, is also the highest in 550 °C bio-oil.     

Pyrolysis of black cumin seed cake in a fixed-bed reactor

The black cumin seed cake (BCSC) is a by-product obtained from the black cumin seeds with cold pressing. This by-product can be utilized as a biomass feedstock for conversion to bio-oil with pyrolysis process. The BCSC samples were initially pyrolyzed on a lab-scale pyrolysis system at different values in the ranges of 300-800 °C and 0.050-0.300 L min⁻¹ to determine the effects of operation temperature and N₂ flow rate on the yields on products, respectively. Then, the bio-oil in the highest yield (wB = 44.37%) which was obtained at pyrolysis final temperature (450 °C) temperature, heating rate (35 °C min⁻¹), particle size (dp > 850 ??m), and sweeping flow rate of 0.200 L min⁻¹ was characterized by Fourier Transform infra-red (FT-IR) spectroscopy, gas chromatography/mass spectrometry (GC-MS) and column chromatography. Consequently, it was shown that the operating temperature and N₂ gas flow rate parameters were effective on the product yields. Also, the important some physico-chemical properties of the pyrolytic oil obtained in high yield were determined as the calorific value of 38.48 MJ kg⁻¹, the empirical formula of CH_1.651O_0.105N_0.042S_0.001, the rich chemical content containing many different chemical groups, and the density of 970.25 kg m⁻³, and the viscosity of 63.42 mm² s⁻¹. Based on the determined properties of the pyrolytic oil, it was decided that the use of pyrolytic oil derived from the BCSC may possible be for the production of the alternative liquid fuels and finely chemicals after the necessary improvements.     

Hydrogen production via catalytic steam reforming of the aqueous fraction of bio-oil using nickel-based coprecipitated catalysts

Hydrogen production was studied in the catalytic steam reforming of a synthetic and a real aqueous fraction of bio-oil. Ni/Al coprecipitated catalysts with varying nickel content (23, 28 and 33 relative atomic %) were prepared by an increasing pH technique and tested during 2 h under different experimental conditions in a small bench scale fixed bed setup. The 28% Ni catalyst yielded a more stable performance over time (steam-to-carbon molar ratio, S/C = 5.58) at 650 °C and a catalyst weight/organic flow rate (W/m_org) ratio of 1.7 g catalyst min/g organic. Using the synthetic aqueous fraction as feed, almost complete overall carbon conversion to gas and hydrogen yields close to equilibrium could be obtained with the 28% Ni catalyst throughout. Up to 63% of overall carbon conversion to gas and an overall hydrogen yield of 0.09 g/g organic could be achieved when using the real aqueous fraction of bio-oil, but the catalyst performance showed a decay with time after 20 min of reaction due to severe coke deposition. Increasing the W/m_org ratio up to 5 g catalyst min/g organic yielded a more stable catalyst performance throughout, but overall carbon conversion to gas did not surpass 83% and the overall hydrogen yield was only ca. 77% of the thermodynamic equilibrium. Increasing reaction temperatures (600–800 °C) up to 750 °C enhanced the overall carbon conversion to gas and the overall yield to hydrogen. However, at 800 °C the catalyst performance was slightly worse, as a result of an increase in thermal cracking reactions leading to an increased formation of carbon deposits.     

Pyrolysis of giant mullein (Verbascum thapsus L.) in a fixed-bed reactor: Effects of pyrolysis parameters on product yields and character

Slow pyrolysis of giant mullein (Verbascum thapsus L.) stalks have been carried out in a fixed-bed tubular reactor with (Al₂O₃, ZnO) and without catalyst at four different temperatures between 400 to 550°C with a constant heating rate of 50°C/min and with a constant sweeping gas (N₂) flow rate of 100 cm³/min. The amounts of bio-char, bio-oil, and gas produced were calculated and the compositions of the obtained bio-oils were determined by gas chromatography-mass spectrometry. The effects of pyrolysis parameters, such as temperature and catalyst, on the product yields were investigated. The results show that both temperature and catalyst have significant effects on the conversion of Verbascum thapsus L. into solid, liquid, and gaseous products. The highest liquid yield of 40.43% by weight including the aqeous phase was obtained with 10% zinc oxide catalyst at 500°C temperature. Sixty-seven different products were identified by gas chromatography-mass spectrometry in the bio-oils obtained at 500°C temperature.     

Integrated catalytic adsorption (ICA) steam gasification system for enhanced hydrogen production using palm kernel shell

This paper investigates the integrated catalytic adsorption (ICA) steam gasification of palm kernel shell for hydrogen rich gas production using pilot scale fluidized bed gasifier under atmospheric condition. The effect of temperature (600–750 °C) and steam to biomass ratio (1.5–2.5 wt/wt) on hydrogen (H₂) yield, product gas composition, gas yield, char yield, gasification and carbon conversion efficiency, and lower heating values are studied. The results show that H₂ hydrogen composition of 82.11 vol% is achieved at temperature of 675 °C, and negligible carbon dioxide (CO₂) composition is observed at 600 °C and 675 °C at a constant steam to biomass ratio of 2.0 wt/wt. In addition, maximum H₂ yield of 150 g/kg biomass is observed at 750 °C and at steam to biomass ratio of 2.0 wt/wt. A good heating value of product gas which is 14.37 MJ/Nm³ is obtained at 600 °C and steam to biomass ratio of 2.0 wt/wt. Temperature and steam to biomass ratio both enhanced H₂ yield but temperature is the most influential factor. Utilization of adsorbent and catalyst produced higher H₂ composition, yield and gas heating values as demonstrated by biomass catalytic steam gasification and steam gasification with in situ CO₂ adsorbent.     

Parametric study on the pyrolysis of manure and wood shavings

In this work, a response surface methodology (RSM) was used to study the effects of temperature (A), feed rate (B) and gas flow rate (C) on the liquid yield, char yield and pH of the biocrude oil. Box-Behnken design was chosen and a total number of 15 experimental runs including 3 center runs were generated for the pyrolysis of a mixture of 50 wt.% layer manure and 50 wt.% loblolly pine wood shavings in a 50 mm bubbling fluidized bed reactor. The operational variables were as follows: temperature (400-550 °C), nitrogen gas flow rate (12-24 L/min), and feed rate (160-480 g/h). A second-order regression models were used to predict the responses. The analysis of variance (ANOVA) was performed with Minitab 16 software and the significant effect of the factors and their interaction effects were tested at 95% confidence interval. The biocrude yield was significantly influenced by temperature, feed rate and gas flow rate. Temperature was the only significant factor that influenced the char yield. Maximum biocrude yield (51.1 wt.%) was achieved at 475 °C with a feed rate of 480 g/h and a gas rate of 12 L/min. The lowest char yield (22.6 wt.%) was achieved at 550 °C, 320 g/h and 12 L/min and the biocrude had the highest pH (4.85) at 475 °C, 160 g/h and 24 L/min. The predictive models proposed agreed with the experimental values.     

Pyrolysis of Alternanthera philoxeroides (alligator weed): Effect of pyrolysis parameter on product yield and characterization of liquid product and bio char

In the present work, fast pyrolysis of Alternanthera philoxeroides was evaluated with a focus to study the chemical and physical characteristics of bio-oil produced and to determine its practicability as a transportation fuel. Pyrolysis of A.philoxeroides was conducted inside a semi batch quartz glass reactor to determine the effect of different operating conditions on the pyrolysis product yield. The thermal pyrolysis of A. philoxeroides were performed at a temperature range from 350 to 550 °C at a constant heating rate of 25 °C/min & under nitrogen atmosphere at a flow rate of 0.1 L/min, which yielded a total 40.10 wt.% of bio-oil at 450 °C. Later, some more sets of experiments were also performed to see the effect on pyrolysis product yield with change in operating conditions like varying heating rates (50 °C/min, 75 °C/min & 100 °C/min) and different flow rates of nitrogen (0.2, 0.3, 0.4 & 0.5 L/min). The yield of bio-oil during different heating rate (25, 50, 75 and 100 °C/min) was found to be more (43.15 wt.%) at a constant heating rate of 50 °C/min with 0.2 L/min N₂ gas flow rate and at a fixed pyrolysis temperature of 450 °C. The High Heating Value (HHV) value of bio-oil (8.88 MJ/kg) was very less due to presence of oxygen in the biomass. However, the high heating value of bio-char (20.41 MJ/kg) was more, and has the potential to be used as a solid fuel. The thermal degradation of A. philoxeroides was studied in TGA under inert atmosphere. The characterization of bio-oil was done by elemental analyser (CHNS/O analyser), FT-IR, & GC/MS. The char was characterized by elemental analyser (CHNS/O analysis), SEM, BET and FT-IR techniques. The chemical characterization showed that the bio-oil could be used as a transportation fuel if upgraded or blended with other fuels. The bio-oil can also be used as feedstock for different chemicals. The bio-char obtained from A. philoxeroides can be used for adsorption purposes because of its high surface area.     

Continuous sorption-enhanced steam reforming of glycerol to high-purity hydrogen production

In this study, the continuous sorption-enhanced steam reforming of glycerol to high-purity hydrogen production by a simultaneous flow concept of catalyst and sorbent for reaction and regeneration using two moving-bed reactors has been evaluated experimentally. A Ni-based catalyst (NiO/NiAl₂O₄) and a lime sorbent (CaO) were used for glycerol steam reforming with and without in-situ CO₂ removal at 500 °C and 600 °C. The simultaneous regeneration of catalyst and sorbent was carried out with the mixture gas of N₂ and steam at 900 °C. The product gases were measured by a GC gas analyzer. It is obvious that the amounts of CO₂, CO and CH₄ were reduced in the sorption-enhanced steam reforming of glycerol, and the H₂ concentration is greatly increased in the pre-CO₂ breakthrough periods within 10 min both 500 °C and 600 °C. The extended time of operation for high-purity hydrogen production and CO₂ capture was obtained by the continuous sorption-enhanced steam reforming of glycerol. High-purity H₂ products of 93.9% and 96.1% were produced at 500 °C and 600 °C and very small amounts of CO₂, CH₄ and CO were formed. The decay in activity during the continuous reaction-regeneration of catalyst and sorbent was not observed.     

Hydrothermal liquefaction of spent coffee grounds in water medium for bio-oil production

Spent coffee grounds (SCG) were liquefied in hot-compressed water to produce crude bio-oil via hydrothermal liquefaction (HTL) in a 100 cm³ stainless-steel autoclave reactor in N₂ atmosphere. We investigated the effects of operating parameters such as retention times (5 min, 10 min, 15 min, 20 min and 25 min), reaction temperatures (200 °C, 225 °C, 250 °C, 275 °C and 300 °C), and water/feedstock mass ratios (5:1, 10:1, 15:1 and 20:1) and initial pressure of process gas (2.0 MPa and 0.5 MPa) on the yield and properties of the resulting crude bio-oil. The highest yield of the crude bio-oil (47.3% mass fraction) was obtained at conditions of 275 °C, 10 min retention time and water/feedstock mass ratio of 20:1 with an initial pressure of 2.0 MPa. The elemental analysis of the produced crude bio-oil revealed that the oil product had a higher heating value (HHV) of 31.0 MJ kg⁻¹, much higher than that of the raw material (20.2 MJ kg⁻¹). GC–MS and FT-IR measurements showed that the main volatile compounds in the crude bio-oil were long chain aliphatic acids and esters.     

Synthesizing hydrogen from ammonia over Ru incorporated SiO2 type nanocomposite catalysts

In this study, Ruthenium incorporated SiO₂ type nanocomposite catalysts were prepared for CO_x free hydrogen production by using one-pot hydrothermal synthesis procedure. Experiments which were carried out under the flow of pure ammonia (300 ml/min) presented that 86% ammonia conversion was obtained at 500 °C over the catalyst having Ru/Si molar ratio of 0.060. Using promoter in the preparation of catalyst enhanced the catalytic activity especially for the ones prepared at low ruthenium loadings. While the catalyst that was prepared at a Ru/Si molar ratio of 0.010 without promoter gave negligible activity at 500 °C, the promoted one gave 33% conversion at 500 °C and 73% at 600 °C. Experiments were also repeated with lower feed flow rate values of ammonia such as 60 ml/min and 5 ml/min. It was seen that catalyst prepared at a Ru/Si molar ratio of 0.010 with promoter gave conversion value over 80% at 400 °C under the feed flow rate of 5 ml/min.     

Production of crude bio-oil via direct liquefaction of spent K-Cups

Spent K-Cups were liquefied into crude bio-oil in a water-ethanol co-solvent mixture and reaction conditions were optimized using response surface methodology (RSM) with a central composite design (CCD). The effects of three independent variables on the yield of crude bio-oil were examined, including the reaction temperature (varied from 255 °C to 350 °C), reaction time (varied from 0 min to 25 min) and solvent/feedstock mass ratio (varied from 2:1 to 12:1). The optimum reaction conditions identified were 276 °C, 3 min, and solvent/feedstock mass ratio of 11:1, giving a mass fraction yield of crude bio-oil of 60.0%. The overall carbon recovery at the optimum conditions was 93% in mass fraction. The effects of catalyst addition (NaOH and H₂SO₄) on the yield of crude bio-oil were also investigated under the optimized reaction conditions. The results revealed that the presence of NaOH promoted the decomposition of feedstock and significantly enhanced the bio-oil production and liquefaction efficiency, whereas the addition of H₂SO₄ resulted in a negative impact on the liquefaction process, decreasing the yield of crude bio-oil.     

Catalysts of Ni/α-Al2O3 and Ni/La2O3-αAl2O3 for hydrogen production by steam reforming of bio-oil aqueous fraction with pyrolytic lignin retention

This paper reports on the steam reforming, in continuous regime, of the aqueous fraction of bio-oil obtained by flash pyrolysis of lignocellulosic biomass (sawdust). The reaction system is provided with two steps in series: i) thermal step at 200 °C, for the pyrolytic lignin retention, and ii) reforming in-line of the treated bio-oil in a fluidized bed reactor, in the range 600–800 °C, with space-time between 0.10 and 0.45 g_catalyst h (g_bio-oil)⁻¹. The benefits of incorporating La₂O₃ to the Ni/α-Al₂O₃ catalyst on the kinetic behavior (bio-oil conversion, yield and selectivity of hydrogen) and deactivation were determined. The significant role of temperature in gasifying coke precursors was also analyzed. Complete conversion of bio-oil is achieved with the Ni/La₂O₃-αAl₂O₃ catalyst, at 700 °C and space-time of 0.22 g_catalyst h (g_bio-oil)⁻¹. The catalyst deactivation is low and the hydrogen yield and selectivity achieved are 96% and 70%, respectively.     

Optimization study of sub/supercritical water liquefication of lignite: Fast liquefaction for high bio-oil yield

Sub/supercritical water liquefication (SCWL) is a water-based thermochemical technology as well as an environmentally friendly treatment by converting wet feedstock into bioenergy. In the present study, a systematic investigation of SCWL of lignite was carried out covering a temperature range between 320 and 440 °C when residence time increased from 5 min to 40 min. The highest bio-oil oil yield of 34.3% with solid residue of 52.7% was obtained at 440 °C for 5 min. Phenol derivatives, carboxylic acids, long chain hydrocarbons, ketones, and naphthalene were the main bio-oil composition through FTIR and GC-MS analysis. Gas yields and their exact compositions were also determined and CO₂ was the dominate gas product but the percentage of CH₄ became significant at severe SCWL conditions. A conclusion was drawn that fast liquefaction (e.g. 5 min) at relative higher temperature (e.g. 400 °C) which avoid excessive gasification and repolymerization reactions was an optimization strategy for high yield bio-oil production from SCWL of lignite.     

Catalytic pyrolysis of biomass: Effects of pyrolysis temperature,sweeping gas flow rate and MgO catalyst

Cotton seed, as a biomass source, is pyrolysed in a tubular fixed-bed reactor under various sweeping gas (N₂) flow rates at different pyrolysis temperatures. In the non-catalytic work, the maximum bio-oil yield was attained as 48.30% at 550 °C with a sweeping gas flow rate of 200 mL min⁻¹. At the optimum conditions, catalytic pyrolysis of biomass samples was performed with various amounts of MgO catalyst (5, 10, 15, and 20 wt.% of raw material). Catalyst addition decreased the quantity of bio-oil yet increased the quality of bio-oil in terms of calorific value, hydrocarbon distribution and removal of oxygenated groups. It was observed that increasing the amount of catalyst used, decreased the oil yields while increased the gas and char yields. Bio-oils obtained at the optimum conditions were separated into aliphatic, aromatic and polar sub-fractions. After the application of column chromatography, bio-oils were subjected into elemental, FT-IR and ¹H NMR analyses. Aliphatic sub-fractions of bio-oils were analyzed by GC–MS. It was deduced that the fuel obtained via catalytic pyrolysis mainly consisted of lower weight hydrocarbons in the diesel range. Finally, obtained results were compared with petroleum fractions and evaluated as a potential source for liquid fuels.     

Enhancement of batch biohydrogen production from prehydrolysate of acid treated oil palm empty fruit bunch

Carbohydrates from hydrolyzed biomass has been a potential feedstock for fermentative hydrogen production. In this study, oil palm empty fruit bunch (OPEFB) was treated by sulfuric acid in different concentrations at 120 °C for 15 min in the autoclave. The optimal condition for pretreatment was obtained when OPEFB was hydrolyzing at 6% (w/v) sulfuric acid concentration, which gave the highest total sugar of 26.89 g/L and 78.51% of sugar production yield. However, the best conversion efficiency of OPEFB pretreatment was 39.47 at sulfuric acid concentration of 4%. A series of batch fermentation were performed to determine the effect of pH in fermentation media and the potential of this prehydrolysate was used as a substrate for fermentative hydrogen production under optimum pretreatment conditions. The prehydrolysate of OPEFB was efficiently converted to hydrogen via fermentation by acclimatized mixed consortia. The maximum hydrogen production was 690 mL H₂ L⁻¹ medium, which corresponded to the yield of 1.98 molH₂/mol_xylose achieved at pH 5.5 with initial total sugar concentration of 5 g/L. Therefore, the results implied that OPEFB prehydrolysate is prospective substrate for efficient fermentative hydrogen conducted at low controlled pH. No methane gas was detected throughout the fermentation.     

Hydrogen-rich gas production by steam gasification of char derived from cyanobacterial blooms (CDCB) in a fixed-bed reactor: Influence of particle size and residence time on gas yield and syngas composition

Char derived from cyanobacterial blooms (CDCB), by-product of fast pyrolysis of cyanobacterial blooms from Dianchi Lake (Yunnan Province, China) at a final pyrolysis temperature of 500 °C were used as feedstock material in this study. Steam gasification characteristics of CDCB were investigated in a fixed-bed reactor to evaluate the effect of particle size (below 0.15 mm, 0.15–0.3 mm, 0.3–0.45 mm, 0.45–0.9 mm, 0.9–3 mm) and solid residence time (3, 6, 9, 12, 15 min) on gas yield and composition, and experiments were carried out at bed temperature range of 600–850 °C, steam flow rate of 0.178 g/min. The results showed that solid residence time played an important role on steam gasification process, while particle size presented less effect on gasification process; proper particle size and longer residence time were favorable for dry gas yield and carbon conversion efficiency (CCE). At the same time, higher reaction temperature reduced influence of particle size on gasification process, and smaller particle size required less residence time for reaction completed. Maximum dry gas yield and CCE reached 1.84 Nm³ kg⁻¹ and 98.82%, respectively, achieved at a temperature of 850 °C, flow rate of 0.178 g/min, solid residence time of 15 min and particle size range of 0.45–0.9 mm.     

Studies on catalytic pyrolysis of empty fruit bunch (EFB) using Taguchi's L9 Orthogonal Array

This paper investigates the effects of four reaction parameters that include type of catalyst, catalyst loading, reaction temperature and nitrogen gas flowrate on the liquid (bio-oil) yield from the catalytic pyrolysis of Empty Fruit Bunch (EFB). The experimental design is based on Taguchi's L9 Orthogonal Array in which the reaction parameters are varied at three levels. The maximum liquid yield is predicted based on systematic experimental runs, and is found to be at 5 wt-% of H-Y catalyst, 500 °C and at nitrogen flowrate of 100 ml min⁻¹. The predicted maximum liquid yield is validated with an experimental run at the corresponding predicted conditions. The bio-oil produced at the optimum reaction condition is characterized and compared with known bio-oil standards in the literature.     

Effect of initial pH,nutrients and temperature on hydrogen production from palm oil mill effluent using thermotolerant consortia and corresponding microbial communities

Thermotolerant consortia were obtained by heat-shock treatment on seed sludge from palm oil mill. Effect of the initial pH (4.5–6.5) on fermentative hydrogen production palm oil mill effluent (POME) showed the optimum pH at 6.0, with the maximum hydrogen production potential of 702.52 mL/L-POME, production rate of 74.54 mL/L/h. Nutrients optimization was investigated by response surface methodology with central composite design (CCD). The optimum nutrients contained 0.25 g urea/L, 0.02 g Na₂HPO₄/L and 0.36 g FeSO₄·7H₂O/L, giving the predicted value of hydrogen production of 1075 mL/L-POME. Validation experiment revealed the actual hydrogen production of 968 mL/L-POME. Studies on the effect of temperature (25–55 °C) revealed that the maximum hydrogen production potential (985.3 mL/L-POME), hydrogen production rate (75.99 mL/L/h) and hydrogen yield (27.09 mL/g COD) were achieved at 55, 45 and 37 °C, respectively. Corresponding microbial community determined by the DGGE profile demonstrated that Clostridium spp. was the dominant species. Clostridium paraputrificum was the only dominant bacterium presented in all temperatures tested, indicating that the strain was thermotolerant.     

Hydrogen production by steam reforming of bio-oil/bio-ethanol mixtures in a continuous thermal-catalytic process

The feasibility of the steam reforming of bio-oil aqueous fraction and bio-ethanol mixtures has been studied in a continuous process with two in-line steps: thermal step at 300 °C (for the controlled deposition of pyrolytic lignin during the heating of the bio-oil/bio-ethanol feed) followed by steam reforming in a fluidized bed reactor on a Ni/α-Al₂O₃ catalyst. The effect of bio-ethanol content in the feed has been analyzed in both the thermal and reforming steps, and the suitable range of operating conditions (temperature and space-time) has been determined for obtaining a high and steady hydrogen yield. Higher ethanol content in the mixture feed improves the reaction indices and reduces coke deposition. Operating conditions of 700 °C and space-times higher than 0.23 g_catalyst h (g_bio-oil+EtOH)⁻¹ are suitable for attaining almost fully conversion of oxygenates (bio-oil and ethanol) and hydrogen yields above 93%, with low catalyst deactivation.