Pyrolysis of cellulose, xylan and lignin with the K2CO3 and ZnCl2 addition for bio-oil production

The chemical structure of liquid products of the wood biopolymers, i.e. cellulose, xylan and lignin pyrolysis at 450 °C with and without the 10 wt.% addition of potassium carbonate or zinc chloride was investigated. The yield of liquid products of pyrolysis was in the range of 24-44 wt.% and their form was depending on the chemical structure of pyrolyzed material. The potassium carbonate and zinc chloride addition to biopolymers has also influenced the temperature range of samples decomposition as well as the structure of resulted bio-oils. All bio-oils from biopolymer were dark-brown water-oil emulsions. Contrarily, bio-oils obtained from biopolymer with K₂CO₃ or ZnCl₂ addition were orange liquids with well-separated water and oil phases. All analyses proved that the composition and the quality of bio-oil strongly depends on both the nature of the starting sample and the presence of the additive. The FT-IR analyses of oils showed that oxygen functionalities and hydrocarbons contents highly depend on the type of biopolymer. Results confirmed the significant removal and/or transformation of oxygen containing organic compounds due to the zinc chloride and potassium carbonate presence during pyrolysis process.     

Thermochemical liquefaction characteristics of microalgae in sub- and supercritical ethanol

Thermochemical liquefaction characteristics of Spirulina, a kind of high-protein microalgae, were investigated with the sub- and supercritical ethanol as solvent in a 1000 mL autoclave. The influences of various liquefaction parameters on the yields of products (bio-oil and residue) from the liquefaction of Spirulina were studied, such as the reaction temperature (T), the S/L ratio (R₁, solid: Spirulina, liquid: ethanol), the solvent filling ratio (R₂) and the type and dosage of catalyst. Without catalyst, the bio-oil yields were in the range of 35.4 wt.% and 45.3 wt.% depending on the changes of T, R₁ and R₂. And the bio-oil yields increased generally with increasing T and R₂, while the bio-oil yields reduced with increasing R₁. The FeS catalyst was certified to be an ideal catalyst for the liquefaction of Spirulina microalgae for its advantages on promoting bio-oil production and suppressing the formation of residue. The optimal dosage of catalyst (FeS) was ranging from 5-7 wt.%. The elemental analyses and FT-IR and GC-MS measurements for the bio-oils revealed that the liquid products have much higher heating values than the crude Spirulina sample and fatty acid ethyl ester compounds were dominant in the bio-oils, irrespective of whether catalyst was used.     

Capacitance behaviour of brown coal based active carbon modified through chemical reaction with urea

The capacitive performance of activated carbons with different contents of nitrogen obtained from brown coal has been investigated. Nitrogen enrichments have been made by exposing the samples to urea without overpressure in oxidizing conditions. The effect of different temperatures of carbonization (500 and 700 °C) and the influence of the sequence of nitrogenation and activation processes have been investigated. Electrochemical study has been performed on microporous carbonaceous materials with high surface areas (BET) ranging from 2209 to 3268 m²/g, and chemical structures with different content of nitrogen (0.2-5.6 wt.%) and oxygen heteroatoms (4.5-11.1 wt.%) and different type of species formed.The presence of nitrogen heteroatoms in carbonaceous materials considerably increases their capacitance, particularly if they work as the negative electrode in alkaline capacitor. Capacitance of the same materials used as a positive electrode is characteristically reduced. Such specific influence of nitrogen has been observed even at their low content implied by the chemical composition of natural brown coal giving capacitance of negative and positive electrode of 341 and 264 F/g, respectively. The similar effect of nitrogen in the acidic medium has been much lower; capacitance of the material used for both electrodes has been of about 300 F/g. Carbonaceous materials containing nitrogen reveal different behaviour, mainly in respect of charge exchange dynamics, if they are used as capacitor electrodes of the opposite polarity.     

Co-liquefaction of microalgae and synthetic polymer mixture in sub- and supercritical ethanol

Co-liquefaction of microalgae (Spirulina) and synthetic polymer (HDPE, high-density polyethylene) in sub- and supercritical ethanol was investigated in a stainless steel autoclave (1000 mL) at different reaction temperatures (T), Spirulina/HDPE ratio (R₁), (Spirulina + HDPE)/ethanol ratio (R₂) and solvent filling ratio (R₃). Results showed that the addition of Spirulina to HDPE liquefaction could make the conversion conditions of HDPE milder. The yield of bio-oil obtained at 613 K with a 1/10 R₂ and a 2/10 R₃ was increased by 44.81 wt.% when the R₁ was raised from 0/10 to 4/6. Meanwhile, the synergetic effects (SE) between HDPE and Spirulina were increased from 0 to 30.39 wt.%. Further increasing R₁ resulted in a decrease in SE. The yields of bio-oil increased with increasing R₂ firstly and then declined. An opposite trend was observed for the yield of residue. The effect of R₃ to the yields of liquefaction products was similar to that of R₂. The content of C and H in bio-oils reduced with increasing R₁, while the content of O increased. The bio-oil from pure Spirulina liquefaction runs mainly consisted of oxygen-containing compounds, such as carboxylic acids, esters and ketones. But the major components of bio-oil from co-liquefaction of Spirulina and HDPE mixture were similar to those of pure HDPE-derived bio-oil, in which aliphatic hydrocarbons dominated.     

Wood/plastic copyrolysis in an auger reactor: Chemical and physical analysis of the products

Previous studies observed that slow copyrolysis of wood and plastic in enclosed autoclaves produced an upgraded raw bio-oil with increased hydrogen content. We now demonstrate that fast simultaneous pyrolyses of 50:50, w/w, pine wood/waste plastics in a 2 kg/h lab scale auger-fed reactor at 1 atm, with a short vapor residence time, generates higher heating value upgraded bio-oils. Three plastics: polystyrene (PS), high density polyethylene (HDPE) and polypropylene (PP) were individually copyrolyzed with southern yellow pine wood at 525, 450 and 450 °C, respectively, to generate modified bio-oils upon condensation. These liquids exhibited higher carbon and hydrogen contents, significantly lower oxygen contents, higher heats of combustion and lower water contents, acid values and viscosities than pine bio-oil. The formation of cross-over wood/plastic reaction products was negligible in the oils. Simultaneous pyrolysis process design requires using a temperature at which the plastic’s thermal decomposition kinetics produce vapors rapidly enough to prevent vaporized plastic from condensing on wood chars and exiting the reactor.     

An in situ reduction approach for bio-oil hydroprocessing

An in situ reduction treatment, combination of reduction and esterification, was investigated to refine bio-oil. Over Raney Ni and zeolites-supported noble metal (Pd and Ru) catalysts, the reductant formic acid decomposed into hydrogen and carbon dioxide, and then hydrogen reduced the bio-oil while compressible CO₂ dissolved in methanol to form a CO₂-CH₃OH expanded liquid. The results showed that Raney Ni and zeolites-supported Ru were highly active in this heterogeneous catalytic system. The reactions preformed at 150-230 °C for 5-7 h would give a better upgraded bio-oil with a high yield of 80-90 wt.%. The unsaturated components in bio-oil were reduced substantially without obvious coke formation, and the oxygen content was lowered by ca. 5 wt.%. Organic acids were converted into esters through the esterification with methanol, and the properties of hydrogenated bio-oil were improved: the pH value increased from 2.17 to ca. 4.5; the higher heating value approached to 22 MJ/kg, and the viscosity decreased from 5.31 to ca. 4.0 mm²/s.     

Application of the Shvo catalyst in homogeneous hydrogenation of bio-oil obtained from pyrolysis of white poplar: New mild upgrading conditions

Upgrading of bio-oils obtained from the fast pyrolysis of biomasses requires the development of efficient catalysts able to work under mild conditions and to cope with the complex chemical nature of the reactant. The present work focuses on the use of the ruthenium based Shvo homogeneous catalyst for the hydrogenation of model mixtures (vanillin, cinnamaldehyde, methylacetophenone, glycolaldehyde, acetol, acetic acid) and of a real bio-oil. The hydrogenation of model compounds has been investigated both in mono- and biphasic mixtures under a P(H₂) = 10 atm in the temperature range of 90-145 °C varying the substrate to catalyst molar ratio from 2000:1 to 200:1. Employing the most active reaction conditions (substrate/catalyst 200:1, T = 145 °C, P(H₂) = 10 atm) the Shvo catalyst maintains its performances under acidic “bio-oil conditions” leading to the almost quantitative conversion of the polar double bonds within 1 h. The activity of the Shvo catalyst was also investigated for the hydrogenation of a bio-oil from poplar in solvent free conditions. Hydrogenation deeply changed the chemical nature of the pyrolysis oil. Aldehydes, ketones and non-aromatic double bonds were almost totally hydrogenated. The catalytic system also promoted the hydrolysis of sugar oligomers into monomers.     

Comparison of the generation of oil by the extraction and the hydropyrolysis of biomass

This paper discusses the maximisation of the yields of useful bio-oils generated from seeds and nut-shells both by extraction and by hydropyrolysis. The formation and the composition of the bio-oils are also discussed.Powdered (<0.25 mm diameter) Rapeseed, Linseed and Safflower seed and Hazel nut and Walnut shells, that is, fresh precursors of liptinite, have been characterised by their elemental analyses, infra-red and NMR spectra. Bio-oils obtained both by extraction and by slow hydropyrolysis to 520 °C at moderate pressure in the presence of ammonium dioxydithiomolybdate have been compared by the same analyses and by gas chromatography. Consistent with previous work [Hardy JA. A greener future with biodiesel. Green Chem 2001 G56-G57], extraction of the seeds with organic solvents, including Diesel oil, gave yields of up to 40% together with an uninteresting residue. However, subsequent saponification of the residues gave further yields of oil. Hydropyrolysis removed oxygen from the seeds as water and as oxides of carbon to generate bio-oil in yields of up to 75%. Whereas little oil could be extracted from the nut-shells, hydropyrolysis gave oil yields of ∼40%. Some char was also formed, suggesting that optimisation of the hydropyrolysis might give even larger yields of oil.     

Influence of reaction conditions and the char separation system on the production of bio-oil from radiata pine sawdust by fast pyrolysis

Radiata pine sawdust was pyrolyzed in a bubbling fluidized bed equipped with a char separation system. The influence of the reaction conditions on the production of bio-oil was investigated through the establishment of mass balance, and the examination of the products' chemical and physical characteristics. The optimal reaction temperature for the production of bio-oil was between 673 and 723 K, and the yield was above 50 wt.% of the product. An optimal feed size also existed. In a particle with a size that was less than 0.3 mm, the bio-oil yield decreased due to overheating, which led to gas formation. A higher flow rate and feeding rate were found to be more effective for the production of bio-oil, but did not significantly affect it. The main compounds of bio-oil were phenolics, including cresol, guaiacol, eugenol, benzendiol and their derivatives, ketones, and aldehydes. In addition, high-quality bio-oils, which contained less than 0.005 wt.% of solid, no ash and low concentrations of alkali and alkaline earth metals, were produced due to the char removal system.     

Structural and electrochemical characterisation of nitrogen enriched carbons produced by the co-pyrolysis of coal-tar pitch with polyacrylonitrile

Carbonaceous materials ranging from soft carbons of moderate nitrogen content (up to 2.5 wt.%) to typical hard carbons with an excess of nitrogen (up to 6 wt.%) were produced by carbonisation at 1050 °C of coal-tar pitch (CTP)—polyacrylonitrile blends with various ratio of the components. The resultant carbons were characterised by elemental analysis, optical and transmission electron microscopy (TEM), X-ray diffraction, X-ray photoelectron spectroscopy and sorption of nitrogen and carbon dioxide. The electrochemical lithium insertion has been investigated in these carbons by a galvanostatic technique, using carbon/lithium two-electrode cells. Independently of the nitrogen content, the electrochemical performance of the soft carbons is comparable. The nitrogen enriched hard carbons demonstrate a relatively low value of reversible capacity, due to the absence of available nanopores. On the other hand, the irreversible capacity increases with the proportion of nitrogen, especially in the form of pyridinic groups. The lone pair of electrons contribute to the trapping of solvated lithium cations on these groups which act as active sites for the electrolyte decomposition during the first reduction, leading to an enhanced irreversible capacity.     

Influence of temperature and alumina catalyst on pyrolysis of corncob

Corncob has been investigated as an alternative feedstock to obtain fuels and chemicals via pyrolysis in fixed-bed reactor. The influence of pyrolysis temperature in the range 300-800 °C as well as the catalyst effects on the products was investigated in detail and the obtained results were compared. The results indicated that a maximum oil yield of 22.2% was obtained at a moderate temperature of 600 °C. The oil yield was reduced when the temperature was increased from 600 to 800 °C, whereas the gas yield increased.Pyrolysis oils were examined by using instrumental analysis, ¹H NMR spectroscopy and GC/MS. This analysis revealed that the pyrolysis oils were chemically very heterogeneous at all temperatures. It was determined that the most abundant compounds composing the bio-oil were phenolics.It was observed that the catalyst decreased the reaction temperature. Most of the components obtained using a catalyst at moderate temperatures was close to those obtained at high temperatures without using a catalyst. Moreover, the use of a catalyst and the high temperatures of the reactions also decreased the amount of oxygenated compounds produced.According to these results, corncob bio-oils can be used as fuel and constitute a valuable source of chemical raw materials.     

Influence of temperature on pyrolysis of recycled organic matter from municipal solid waste using an activated olivine fluidized bed

Pyrolysis of an organic concentrate from municipal solid waste was carried out using a bench-scale fluidized bed reactor at 350-540 °C comparing Al₂O₃ with activated olivine sand as bed materials. A maximum oil yield of 50 wt.% was obtained using the activated olivine sand at 400 °C while only 45 wt.% was obtained at 500 °C using Al₂O₃. The bio-oils using activated olivine sand at 400 °C had an H/C ratio of 1.50 and O/C ratio of 0.37 and were less aromatic and less nitrogenous compare to the oils obtained using Al₂O₃ at 400 °C where the H/C ratio was 1.32 and the O/C ratio was 0.44. The aromatic compounds were found to be reduced while the aliphatic compounds increased in the oils generated using activated olivine sand. The calorific value of the bio-oil at 500 °C was 29 MJ/kg using activated olivine sand while the bio-oil using Al₂O₃ was 23 MJ/kg. The presence of iron, magnesium and other oxides probably promotes the removal of oxygen, which indicates that the activation energy of C―O bond breakage is reduced compared to the C―C bonds, thus promoting dehydration, decarboxylation and alkalation reactions to produce aliphatic fatty acid at lower temperatures.     

Pyrolysis characteristics of Oriental white oak: Kinetic study and fast pyrolysis in a fluidized bed with an improved reaction system

The kinetic parameters for the pyrolysis of Oriental white oak were evaluated by thermogravimetric analysis (TGA). The white oak was pyrolyzed in a fluidized bed reactor with a two-staged char separation system under a variety of operating conditions. The influence of the pyrolysis conditions on the chemical and physical characteristics of the bio-oil was also examined. TGA showed that the Oriental white oak decomposed at temperatures ranging from 250 to 400 °C. The apparent activation energy ranged from 160 to 777 kJ mol^− 1. The optimal pyrolysis temperature for the production of bio-oil in the fluidized bed unit was between 400 and 450 °C. A much smaller and larger feed size adversely affected the production of bio-oil. A higher fluidizing gas flow and higher biomass feeding rate were more effective in the production of bio-oil but the above flow rates did not affect the bio-oil yields significantly. Recycling a part of the product gas as a fluidizing medium resulted the highest bio-oil yield of 60 wt.%. In addition, high-quality bio-oil with a low solid content was produced using a hot filter as well as a cyclone. With exception of the pyrolysis temperature, the other pyrolysis conditions did not significantly affect the chemical and physical characteristics of the resulting bio-oil.     

Optimisation of supercapacitors using carbons with controlled nanotexture and nitrogen content

In order to optimize the performance of supercapacitors, the capacitance of the carbon materials used as electrodes was strictly related to their pores size and also to their redox properties. Well-sized carbons have been elaborated through a template technique using mesoporous silica. For a series of template carbons, a perfect linear dependence has been found for the capacitance values versus the micropore volume determined by CO₂ adsorption. The redox properties of carbons were enhanced by substituting nitrogen for carbon up to ca. 7 wt.%. For carbons with similar nanotextural characteristics, the electrochemical measurements showed a proportional increase of the specific capacitance with the nitrogen content in acidic electrolyte. For an activated carbon from polyacrylonitrile with a specific surface area of only 800 m² g⁻¹, but with a nitrogen content of 7 wt.%, the capacitance reaches 160 F g⁻¹, with very little fading during cycling.     

Fast and catalytic pyrolysis of pistacia khinjuk seed in a well-swept fixed bed reactor

The pyrolysis of pistacia khinjuk seed was investigated with the aim to study the product distribution and their chemical compositions and to identify optimum process conditions for maximizing the bio-oil yield. Fast and catalytic pyrolysis of biomass sample with two selected commercial catalyst, namely BP 3189 and Criterion-424 have been conducted in a well-swept resistively heated fixed bed reactor under nitrogen atmosphere. The maximum bio-oil yield of 66.5% with the use of Criterion-424 and 69.2% with the use of BP 3189 were obtained at the catalytic pyrolysis conditions, while it was only 57.6% without catalyst. The bio-oils were investigated, using chromatographic and spectroscopic techniques.     

Effects of temperature,reaction time,atmosphere, and catalyst on hydrothermal liquefaction of Chlorella

Hydrothermal liquefaction (HTL) is the direct conversion of wet biomass into bio-oil at high temperature (200–400°C) and high pressure (10–25 MPa). In this work, we investigated HTL with 4.5 g of Chlorella and 45 ml of water/ethanol (1:1 vol. ratio) in a 100 ml reactor. Bio-oils produced are characterized via elemental analysis, thermogravimetric analysis, and gas chromatography–mass spectrometry (GC–MS). HTL of Chlorella was investigated at 240 and 250°C for 0 and 15 min under an air or H₂ atmosphere and with and without 5% zeolite Y. Temperature increased the bio-oil yield from 38.75% at 240°C to 43.04% at 250°C for 15 min reaction time. Longer reaction time increased the bio-oil yield at 250°C from 39.14% for 0 min to 43.04% for 15 min. The H₂ atmosphere had a significant effect for HTL at 240°C. Zeolite Y increased the bio-oil yield significantly from 32.03% to 43.06% at 250°C for 0 min. The carbon content of bio-oil increased with the temperature while the oxygen content decreased. The boiling point distribution of bio-oils in the range of 110–300°C varies with temperature, and atmosphere. At 240°C for 15 min, the 110–300°C range increased from 31.19% in air (240-15-air) to 39.25% in H₂ (240-15-H₂). The H₂ atmosphere increased the content of hydrocarbons, alcohols, and esters from 69.61% in air (240-0-air) to 82.83% in H₂ (240-0-H₂). Overall, temperature, reaction time, atmosphere, and catalyst all significantly influenced the yield and/or quality of bio-oils from HTL of Chlorella.     

Formation of nano SiC whiskers in bauxite-carbon composite materials and their consequences on strength and density

SiC whisker is excellent in characteristics such as specific strength and chemical stability, and is useful as a composite reinforcing material. In this paper, the effect of the formation of in situ nano SiC whiskers on strength and density of bauxite-carbon composites was studied. Samples were prepared composed of 65 wt.% bauxite, 15 wt.% SiC-containing material, 10 wt.% coke, 10 wt.% resole and different values of silicon additives. The pressed samples were cured at 200 °C (2 h) and fired at 1100 °C and 1400 °C (2 h). XRD, SEM, TEM, EDX, FTIR and STA were used to characterize the samples. These characterizations indicated that SiC nano whiskers, 50-90 nm, are single crystalline β-SiC with mechanism of the formation VLS. So, firing temperature is an important factor. As, SiC nano whisker was formed at 1400 °C and improved CCS values up to four times in sample containing 6 wt.% ferrosilicon.     

Optical and mechanical properties of transparent acrylic based polyurethane nano Silica composite coatings

The aim of this work is to investigate the effect of two types of nano Silica (precipitated and fumed) with various concentrations on the optical and mechanical properties of transparent polyurethane acrylic based nano composite coatings. Transparency, gloss, UV absorption, adhesion strength and impact resistance of the samples have been measured. The gloss of the film samples remains unchanged compared to the reference film sample up to 2 wt.% (weight percent) for both types of nanoparticles. The samples containing 4 and 6 wt.% nano Silica show reduction in the gloss property by 4.3% and 5.3%, respectively, for fumed samples and 1.8% and 23% for precipitated samples. The film samples show increase in light absorption in the wavelength region of 250–2000 nm by increasing the content of nano Silica. Also cross cut and pull-off test results show that a good adhesion to steel can be obtained (5B for cross-cut, 7 MPa for pull-off) and no changes in impact strength of the samples with respect to the reference have been observed.     

Production of bio-oil from fixed bed pyrolysis of bagasse

The objective of this work was to produce renewable liquid fuel (bio-oil) from locally produced bagasse by pyrolysis in a batch feeding and fixed bed reactor. The experiments were performed at different temperatures ranging from 300 to 600 °C. The bio-oil was collected from two condensers of different temperatures and defined as oil-1 and oil-2. The maximum total yield of bio-oil was found to be 66.0 wt% based on bagasse. The carbon based non-condensable gases were CO, CO₂, methane, ethane, ethene, propane and propene. The density and viscosity of oil-1 were found to be 1130 kg/m³ and 19.32 centipoise and that were 1050 kg/m³ and 4.25 centipoise for oil-2, respectively. The higher heating values (HHV) of them were 17.25 and 19.91 MJ/kg, respectively. The pH of the bio-oils was found to be around 3.5 and 4.5 for oil-1 and oil-2, respectively. The water, solid and ash contents of oil-1 and oil-2 were determined and found to be around 15, 0.02 and 0.03 wt% and 11, 0.01 and 0.02 wt%, respectively based on bagasse.     

Combustion characteristics and kinetics of bio-oil

The combustion characteristics of bio-oils derived from rice husk and corn were studied by thermogravimetry analysis. According to the thermo-gravimetry (TG), differential thermogravimetry (DTG) and differential thermal analysis (DTA) curves of bio-oils in air and nitrogen atmosphere, we analyzed the combustion characteristics of different kinds of bio-oils in different atmospheres and worked out the combustion kinetics parameters of the bio-oil, providing reliable base data for the burning of bio-oil. The thermogravimetry indicated that the combustion process of bio-oil was divided into three stages. At the same time, the combustion process can be described by different order reaction models, and with the method of Coats-Redfern, the activation energy and frequency factor of different kinds of bio-oils were obtained.