Bio-oil production from Glycyrrhiza glabra through supercritical fluid extraction

Glycyrrhiza glabra was liquefied by ethanol and acetone in an autoclave under high pressure using potassium hydroxide or sodium carbonate as the catalyst, as well as without catalyst at various temperatures (250, 270 and 290 °C) for producing bio-oil. The experimental results show that the yield of the main liquefaction product (bio-oil) was influenced significantly by liquefaction parameters such as solvent type, and catalyst type and temperature. The results showed that the maximum bio-oil yield was obtained in acetone (79%) at 290 °C without catalyst. The products of liquefaction (bio-oil) were analysed and characterized using various methods including elemental analysis, Fourier transform infrared spectroscopy and gas chromatography–mass spectrometry. GC–MS identified 131 and 147 different compounds in the bio-oils obtained at 270 and 290 °C, respectively.     

Deterpenation of mandarin (Citrus reticulata) peel oils by means of countercurrent multistage extraction and adsorption/desorption with supercritical CO2

The mandarin (Citrus reticulata) peel oil consists of more than 98 wt.% terpenes and a small fraction of oxygenated components responsible for its distinct smell. The terpene fraction is composed mostly of limonene and the oxygenated aroma fractions are composed mainly of linalool and decanal. The removal of terpenes must be performed in order to increase the storage time of citrus oils. In this work, the deterpenation of two different cold-pressed mandarin peel oils employing countercurrent extraction and ad-/desorption with supercritical CO₂ and a combination of these processes were investigated. Countercurrent experiments were carried out at pressures ranging from 8.5 to 10.0 MPa and at 50 and 60 °C. At 10.0 MPa and 60 °C, a maximum selectivity of 12.8 between terpenes and aromas could be obtained at a folding ratio of 5.0, showing that the fractionation by means of countercurrent gas extraction could be employed. To investigate the complete removal of terpenes, ad-/desorption experiments were also performed and both the raffinate samples obtained through the countercurrent fractionation and the crude cold-pressed peel oils were used as feed material. The components evaluated were desorbed from silica-gel and the best fractionation results were obtained at 40 °C, 25 wt.% oil loading in two sequential pressure steps. Initially, terpenes were completely desorbed at 8.0 MPa. The second desorption step was carried out at 20.0 MPa and a selective fractionation of important aroma components was observed. Additionally, scale-up experiments were performed.     

Bio-oil production from oil palm biomass via subcritical and supercritical hydrothermal liquefaction

This paper presents the studies on the liquefaction of three types of oil palm biomass; empty fruit bunch (EFB), palm mesocarp fiber (PMF) and palm kernel shell (PKS) using water at subcritical and supercritical conditions. The effect of temperature (330, 360, 390 °C) and pressure (25, 30, 35 MPa) on bio-oil yields were investigated in the liquefaction process using a Inconel batch reactor. The optimum liquefaction condition of the three types of biomass was found to be at supercritical condition of water i.e. at 390 °C and 25 MPa, with PKS yielding the maximum bio-oil yield of 38.53 wt%, followed by EFB and PMF, with optimum yields of 37.39 wt% and 34.32 wt%, respectively. The chemical compositions of the bio-oils produced at optimum condition were analyzed using GC–MS and phenolic compounds constituted the major portion of the bio-oils, with other minor compounds present such as alcohols, ketones, aromatic hydrocarbons and esters.     

Liquefaction of giant fennel (Ferula orientalis L.) in supercritical organic solvents: Effects of liquefaction parameters on product yields and character

Ferula orientalis L. stalks were liquefied in an autoclave in supercritical organic solvents (methanol, ethanol, 2-propanol, acetone and 2-butanol) with (NaOH, Na₂CO₃, ZnCl₂) and without catalyst at five different temperatures ranging from 240 °C to 320 °C. The amounts of solid (unconverted raw material), liquid (bio-oil) and gas produced, as well as the composition of the resulting liquid phase, were determined. The effects of various parameters such as temperature, solvent, catalyst and ratio of catalyst on product yields were investigated. The results showed that conversion highly depends on the temperature and catalyst. The highest bio-oil yield (53.97%) was obtained using acetone with 10% zinc chloride at 300 °C. The liquid products were extracted with benzene and diethyl ether. Some of selected liquid products (bio-oils) were analyzed by elemental, FT-IR and GC–MS. 126 different compounds were identified by GC–MS in the liquid products obtained in ethanol at 300 °C.     

Catalytic effects of ferric chloride and sodium hydroxide on supercritical liquefaction of thistle (Cirsium yildizianum)

Cirsium yildizianum stalks were liquefied in organic solvents under supercritical conditions with and without catalyst in a cylindrical reactor at temperatures of 260, 280 and 300 °C. The effects of liquefaction temperature, catalyst type and solvent on product yields were investigated. The liquid products (bio-oils) were extracted with diethyl ether and benzene using an extraction procedure. The liquid yields in supercritical methanol, ethanol and acetone were found to as 45.66%, 49.34% and 60.05% in the non-catalytical runs at 300 °C, respectively. The highest conversion (liquid + gaseous products) was obtained in acetone with 10% ferric chloride at 300 °C in the catalytic runs. The produced liquids at 300 °C were analyzed and characterized by elemental, GC–MS and FT-IR. 85, 79 and 60 different types of compounds were identified by GC–MS obtained in methanol, ethanol and acetone, respectively. The liquid products were composed of various organics including aromatics, nitrogenated and oxygenated compounds.     

Intensification of biodiesel production from vegetable oils using ultrasonic-assisted process: Optimization and kinetic

Intensification of biodiesel production process using low frequency ultrasonic irradiation (20 kHz, 200 W) is elucidated in this study. Effects of five process variables in an ultrasonic-assisted reactor catalyzed by SrO through transesterification of vegetable oils are investigated. RSM was employed and the optimum conditions were at an ultrasonic pulse on of 9 s followed by 2 s of pulse off within a reaction time of 30.7 min. The optimum ultrasonic power was found to be 130 W using an oil amount of 52 g (R² = 0.97). The model was applicable to different types of oil with errors less than 10%. FFA content was responsible for the different yields obtained with different oils. Three steps of the transesterification process were measured to obtain the kinetic study. The results revealed that the reaction followed a second-order kinetic. The activation energies varied between 70.63 kJ/mol and 136.93 kJ/mol showing relatively high coefficient of determinations.     

Pyrolysis of two different biomass samples in a fixed-bed reactor combined with two different catalysts

Pyrolysis of Euphorbia rigida and sesame stalk biomass samples with two selected commercial catalyst, namely DHC-32 and HC-K 1.3Q, have been conducted in a fixed-bed reactor. The effect of different catalysts and their ratio (5, 10 and 20% w/w) and pyrolysis temperature (500 and 750 °C) on the pyrolysis product yields were investigated and the obtained results were compared with similar experiments without catalyst. Bio-oil yield was increased comparing with non-catalytic experiments, at final pyrolysis temperature of 500 °C for both biomass samples and catalysts. In the catalytic experiments; when the temperature reached to 750 °C, although bio-oil product yield was reduced, the gas product yield was increased comparing with non-catalytic experiments.The pyrolysis oils were examined using spectroscopic and chromatographic analyses and then fractioned by column chromatography. Although the aliphatic and aromatic fractions were decreased and polar fraction was increased with catalytic pyrolysis of E. rigida; an opposite trend was observed in the sesame stalk pyrolysis oil, comparing with non-catalytic results.Obtained results were compared with petroleum fractions and determined the possibility of being a potential source of renewable fuels.     

Experimental measurements and modeling of CO2 solubility in sunflower,castor and rapeseed oils

In this work solubility measurements of CO₂ in three vegetable oils, a high oleic sunflower oil (HOSO), a castor oil and a rapeseed oil, for mole fractions ranging from 0.32 to 0.93 in the temperature range 298–363 K and up to 75 MPa were performed. Moreover, the densities and viscosities of these oils are reported from 278.15 to 373.15 K at atmospheric pressure. These data were used to evaluate the predictive ability of the fragment based approach. Solubility data were modeled by means of the SRK EoS and predicted employing the Carvalho and Coutinho correlation. Global average deviations inferior to 6% in CO₂ mole fraction composition were achieved with the SRK EoS and maximum percentage absolute average deviations of 13% in pressure were obtained using the Carvalho and Coutinho correlation.     

Synthesis of phenolic resol resins using cornstalk-derived bio-oil produced by direct liquefaction in hot-compressed phenol–water

For the synthesis of biomass-based resol resins, cornstalk powders were liquefied in a hot-compressed phenol–water (1:4, wt./wt.) medium at 300–350 °C. It was observed that essentially no phenol was reacted with the cornstalk degradation intermediates during the liquefaction process. The cornstalk-derived bio-oils contained oligomers of phenol and substituted phenols, originated primarily from the lignin component of the cornstalk feedstock. Using the cornstalk-derived bio-oils, resol resins were readily synthesized under the catalysis of sodium hydroxide. The biomass-derived resol resins were brown viscous liquids, possessing broad molecular weight distributions. In comparison with those of a conventional phenol resol resin, the properties of the bio-based resins were characterized by GPC, FTIR, DSC and TGA. The as-synthesized bio-oil resol resin exhibited typical properties of a thermosetting phenol–formaldehyde resin, e.g., exothermic curing temperatures at about 150–160 °C, and an acceptable residual carbon yield of ca 56% at 700 °C for the cured material.     

Relationships derived from physical properties of vegetable oil and biodiesel fuels

The aim of this study was to estimate mathematical relationships between higher heating value (HHV) and viscosity, density or flash point measurements of various biodiesel fuels. The HHV is an important property defining the energy content and thereby efficiency of fuels, such as vegetable oils and biodiesels. The biodiesels were characterized for their physical and main fuel properties including viscosity, density, flash point and higher heating value. The viscosities of biodiesels (2.8–5.1 mm²/s or cSt at 311 K) were much less than those of pure oils (23–53 mm²/s at 311 K), and their HHVs of approximately 41 MJ/kg were 10% less than those of petrodiesel fules (～46 MJ/kg). Compared to No. 2 diesel fuel, all of the vegetable oil methyl esters were slightly viscous. The density and flash point values of vegetable oil methyl esters are highly lower than those of vegetable oils. The HHVs of vegetable oils and their biodiesels were measured and correlated using linear least square regression analysis. There is high regression between viscosity and higher heating value for vegetable oil and biodiesel samples. An increase in density from 848 to 885 g/L for biodiesels increases the viscosity from 2.8 to 5.1 cSt and the increases are highly regular. There is high regression between density and viscosity values vegetable oil methyl esters. The relationships between viscosity and flash point for vegetable oil methyl esters are considerably regular.     

Fast pyrolysis of palm kernel cake using a fluidized bed reactor: Design of experiment and characteristics of bio-oil

In this study, the central composite rotatable design (CCRD) was employed to investigate the effects of the feedstock feed rate, biomass particle size, pyrolysis temperature, and residence time on the fast pyrolysis of palm kernel cake. A mathematical model for the liquid product yield was developed and applied to obtain a maximum yield of 49.5 wt%. The GC–MS analyses of the bio-oils at the two different temperatures of 400 and 500 °C showed that they were a complex mixture composed of mostly oxygenated compounds including β-D-allose, derivatives of furan and phenol, and a considerable amount of fatty acids.     

Production of concentrated natural beta-carotene from buriti (Mauritia vinifera) oil by enzymatic hydrolysis

The present work aimed at the extraction and concentration of β-carotene from crude and refined buriti oils using enzymatic hydrolysis as a process strategy. The performance of two commercial lipolytic preparations (Lipozyme TL IM and CALB L), as well as lipases from Yarrowia lipolytica, was evaluated. The parameters considered in the hydrolysis process were: temperature, enzyme loading and ratio buriti oil/water. Based on a previously conducted statistical design, the experimental conditions were set in order to maximize the free fatty acids (FFA) content in the oil, and simultaneously, minimize the loss of carotenoids. Lipozyme TL IM showed to be the most appropriate enzyme source for the hydrolysis of both oils. The optimized conditions determined for the crude buriti oil processing were 31 °C, 0.0047 g lipase mL^?1 (0.47 g lipase per 100 mL reactional mixture) and 2.33 (ratio oil/water), while for the refined oil, 45 °C, 0.0066 g lipase mL^?1 and 1.80 were the best conditions. At the optimized conditions, the maxima FFA release were 73.0% and 74.8% and the total carotenoids contents were 1578 and 793 mg kg^?1, respectively for the crude and the refined buriti oils, after 4 h of reaction agitated at 300 rpm. Following hydrolysis, oils were deacidified by winterization or phases partition with ethanol.     

Kinetics,aggregation behavior and optimization of the fractionation of whey protein isolate with hydrochloric acid

Concentrated WPI solutions (10%, w/w) containing approximately 50% beta-lactoglobulin (β-LG) and 26% alpha-lactalbumin (α-LA) were fractionated with HCl at acidic pH and moderate temperature to obtain enriched α-LA and β-LG fractions. Aggregation behavior and kinetics of protein precipitation and aggregate formation were analyzed as a function of four process parameters: pH (3.0–5.5), temperature (50–70 °C), reaction time (0–180 min) and protein concentration (10–29%). The precipitation and aggregation of α-LA appeared rate-limited, with a logarithmic dependence of time and possible bimodal nucleation rate, and varied considerably with pH and temperature. Aggregates as large as ～300 μm were noted after 120 min at pH 4, 60 °C. Processing parameters were optimized to obtain both a high aggregate yield and optimal composition of the aggregate fraction. The optimally enriched solid and liquid fractions contained 58% α-LA and 76% β-LG, respectively, with 99% and 74% recovery ratios. Over the pH range studied, β-LG aggregation was found negligible at 60 °C and β-LG recovery in the aggregates attributed to liquid holding. Increasing WPI concentration accelerated α-LA aggregation, demonstrating a concentration-dependent aggregation mechanism, and reduced aggregate purity. Enriched whey protein fractions are valuable health-enhancing food ingredients.     

Hydrothermal liquefaction of wheat straw in hot compressed water and subcritical water–alcohol mixtures

Hydrothermal liquefaction of lignocellulosic biomass (wheat straw) into bio-oil has been investigated under subcritical conditions (temperature up to 350 °C, pressure up to 200 bar) in water and water–alcohol mixtures using ethanol and isopropanol in a continuously operated tubular reactor. The effect of different reaction parameters such as temperature, pressure and water–alcohol ratio on the biomass conversion, cracking products yield and the higher heating value (HHV) of the received bio-oil was studied. The water–ethanol mixture was found to be a very reactive medium showing a complete biomass conversion and >30 wt% yield of high caloric oil (HCO). A maximum HHV of 28 MJ/kg for HCO was achieved. In addition, Ru (5 wt%) on H-Beta support was used as catalyst in a run with hydrogen in the feed showing deeper deoxygenation of reaction intermediates and highest HHV of the product oil (30 MJ/kg). This work demonstrated the usability of water–ethanol mixtures for an effective depolymerization of lignocellulosic biomass to bio-oils under subcritical reaction conditions with more than doubled HHV compared to the feedstock, in particular using a catalyst and the presence of hydrogen for further deoxygenation.     

Three-liquid-phase salting-out extraction of effective components from waste liquor of processing sea cucumber

A three-liquid-phase (TLP) salting-out extraction system composed of n-hexane/ethanol/sodium carbonate/water was investigated to extract oils, saponins, proteins and polysaccharides simultaneously from waste liquor of processing sea cucumber. The effects of the ratio of ethanol to sodium carbonate, n-hexane concentration and extraction time were investigated. The results showed that 86.7% of oils were distributed in the top n-hexane phase, 82.9% of saponins in the middle ethanol phase, 93.2% of proteins and 92.9% of polysaccharides in the interface between the middle and the bottom salt phase when the system composed of 28% (w/w) n-hexane/11.52% (w/w) ethanol/8.64% (w/w) sodium carbonate was used at 37 °C for 0.5 h. When the system was progressively enlarged from 30 g to 25 kg, the yield of polysaccharides, proteins, oils and saponins was decreased only by 1.0%, 2.8%, 1.0% and 2.6%, respectively. The recycle of salt and solvents in three-liquid-phase system was also studied, and the results showed that the recovery of n-hexane, ethanol and salt were 81.4%, 80.8% and 72.0%, respectively. Recycling materials for the extraction, the yield for proteins and oils decreased by 2.0% and 5.4%, respectively, comparing with the pure system.     

Determination of rare earth elements in Niger Delta crude oils by inductively coupled plasma-mass spectrometry

A profile for rare earth elements (REE) of crude oils from the offshore – shallow water and onshore fields in the Niger Delta, analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) is reported. The oil samples were prepared for ICP-MS measurement by acid digestion into colourless aqueous solution. The analysis method was validated using standard reference materials SLRS-4 and NIST-1640. Results showed percentage recovery values that ranged from 81.8% to 115.4% for Co, Cu, Fe, Mn, Ni, Sb and U and from 98.8% to 104.7% for Co, Cu, Fe, Mn, Ni and Sb. The magnitude of deviation recorded in SLRS-4 for Co and Fe suggests that it may not be a suitable standard for these elements using the ICP-MS method outlined in this study. The concentrations of the detected REE; La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er and Yb ranged from 0.01 to 1.58 ppb with an average of 0.98 ppb (%RSD < 5) for the oil samples analyzed. Light REEs (LREE) were identified in all the oil samples while heavy rare earth elements (HREE) were identified in offshore oil samples only. LREE patterns constructed from chondrite-normalized values for the oils show some similarities among the oils, which suggest common origin of the oils and that the REE got into the oils from similar source. While those with different chondrite-normalized REE patterns suggest different source input of the REE. This indicates that REE will be a useful tool in oil–oil correlation. Statistical evaluation of these oils by cluster analysis using the REE as variables clearly discriminated according to their geographic sources. Biodegradation has pronounced effect on the concentration of REE in oils. Therefore, REE contents of oils will be useful in oil classification. ICP-MS proved to be a versatile method for the determination of rare earth elements in Niger Delta oils.     

The effect of flux and residence time in the production of biodiesel from various feedstocks using a membrane reactor

Biodiesel produced from lipid sources is a clean-burning, biodegradable, nontoxic fuel that is free of aromatic hydrocarbons. Current biodiesel production processes are tedious and involve two to three reaction steps each followed by separation and purification. Process integration of reaction and separation in a single step within a membrane reactor (MR) offers several advantages over conventional reactors.This investigation is aimed at studying the effect of membrane flux and residence time on the performance of a membrane reactor in treating a variety of raw and used feedstocks. A membrane reactor having three selectable reactor volumes was designed to decouple the effect of residence time in the reactor from membrane flux on the performance of the reactor. Low free fatty acid (FFA) oils (FFA < 1%), i.e. canola, corn, sunflower and un-refined soy oils, and high FFA waste cooking oil (FFA = 5%) were base transesterified and the quality of the biodiesel produced was determined in terms of free glycerine, mono-glyceride, di-glyceride and tri-glyceride content. All oils were base transesterified without pretreatment.Based on the composition of the final product, the MR could be operated at the upper limit of the flux tested (70 L/m²/h) and a residence time of 60 min. The ASTM D6751 and EN 14214 standards for glycerin and glycerides were reached in the washed biodiesel product for all feedstocks and run conditions. The operating pressure in the reactor was exceeded at 70 L/m²/h in treating waste oils and pre-treated corn oil. For these oils, reasonable operating pressures in the reactor were reached at a membrane flux of 30–40 L/m²/h. The quality of the washed biodiesel always met ASTM and EN standards. The FAME produced from WCO at intermediate fluxes and high residence times met the ASTM and EN standards without water washing.     

Biodiesel production over Ca-based solid catalysts derived from industrial wastes

The solid oxide catalysts derived from the industrial waste shells of egg, golden apple snail, and meretrix venus were used as biodiesel production catalysts. Their catalytic activity in transesterification of palm olein oils and their physicochemical properties (by TG/DTA, EDX, SEM, N₂ sorption, CO₂-TPD, and XRD) were systematically investigated. The waste materials calcined in air with optimum conditions (temperature of 800 °C, time of 2–4 h) transformed calcium species in the shells into active CaO catalysts. The activity of the catalysts was in line with the basic amount of the strong base sites, surface area, and crystalline phase in the catalysts. All catalysts derived from egg and mollusk shells at 800 °C provided high activity (>90% fatty acid methyl ester (FAME) in 2 h). These abundant wastes showed good potential to be used as biodiesel production catalysts.     

Microwave-heated pyrolysis of waste automotive engine oil: Influence of operation parameters on the yield,composition, and fuel properties of pyrolysis oil

The pyrolysis of waste automotive engine oil was investigated using microwave energy as the heat source, and the yield and characteristics of the pyrolysis oils (i.e. elemental analysis, hydrocarbon composition, and potential fuel properties) are presented and discussed. The microwave-heated pyrolysis generated an 88 wt.% yield of condensable pyrolysis oil with fuel properties (e.g. density, calorific value) comparable to traditional liquid transportation fuels derived from fossil fuel. Examination of the composition of the oils showed the formation of light aliphatic and aromatic hydrocarbons that could also be used as a chemical feedstock. The oil product showed significantly high recovery (90%) of the energy present in the waste oil, and is also relatively contaminant free with low levels of sulphur, oxygen, and toxic PAH compounds. The high yield of pyrolysis oil can be attributed to the unique heating mode and chemical environment present during microwave-heated pyrolysis. This study extends existing findings on the effects of pyrolysis process conditions on the overall yield and formation of the recovered oils, by demonstrating that feed injection rate, flow rate of purge-gas, and heating source influence the concentration and the molecular nature of the different hydrocarbons formed in the pyrolysis oils. The microwave-heated pyrolysis can be performed in a continuous operation, and the apparatus described which is fitted with magnetrons capable of delivering 5 kW of microwave power is capable of treating waste oil at a feed rate of 5 kg/h with a positive energy ratio of 8 (energy content of hydrocarbon products/electrical energy supplied for microwave heating) and a net energy output of 179,390 kJ/h. Our results indicate that microwave-heated pyrolysis shows exceptional promise as a means for recycling and treating problematic waste oil.     

Supercritical carbon dioxide fractionation of T. minuta and S. officinalis essential oils: Experiments and process analysis

Essential oils are an important source of compounds with different degree of biocidal activity against microorganisms, insects, weeds and other pathogens. They have potential application in pharmaceutical, cosmetic and food industry, as well as for agriculture and crop protection. Supercritical fluid fractionation is an interesting technology for the selective removal of monoterpenes (MT) and the purification or enrichment of the more bioactive oxygenated terpenes (OT), resulting in more effective, stable and water soluble products. In this work, the fractionation of Tagetes minuta and Salvia officinalis essential oils with carbon dioxide is experimentally studied in a semicontinuous apparatus at 313 K and 80 bar. Successive extracts are collected and the composition determined by gas chromatography. Process behavior is modeled with the group contribution equation of state (GC-EOS), showing a good agreement between model predictions and experimental results. The GC-EOS model is applied to the simulation and analysis of two continuous fractionation schemes: a simple countercurrent column and a countercurrent column with external reflux. The influence of operation variables (temperature, pressure, solvent-to-feed ratio, thermal gradient, reflux ratio) is studied in order to maximize OT concentration and recovery in the raffinate and to minimize carbon dioxide consumption. Experimental and simulation results are discussed in terms of the relative volatilities between MT and OT fractions. Particularly in the case of S. officinalis, the presence of several OT of intermediate volatility and a significant amount of higher molecular weight sesquiterpenes (ST) limits the separation performance, even when external reflux is applied.