On-column precipitation and re-dissolution of asphaltenes in petroleum residua

A new automated separation technique was developed for measuring the distribution profiles of the most polar, or asphaltenic components of an oil, using a continuous flow system to precipitate and re-dissolve asphaltenes. Methods of analysis based on this new technique were explored. One method based on the new technique involves precipitation of a portion of residua sample in heptane on a polytetrafluoroethylene-packed (PTFE) column. The precipitated material is re-dissolved in three steps using solvents of increasing polarity: cyclohexane, toluene, and methylene chloride. The amount of asphaltenes that dissolve in cyclohexane is a useful diagnostic of the thermal history of an oil, and its proximity to coke formation. For example, about 40% (w/w) of the heptane asphaltenes from unpyrolyzed residua dissolves in cyclohexane. As pyrolysis progresses, this number decrease to below 15% as coke and toluene-insoluble pre-coke materials appear. Currently, the procedure for the isolation of heptane asphaltenes and the determination of the amount of asphaltenes soluble in cyclohexane spans three days. The automated procedure takes one hour. Another method uses a single solvent, methylene chloride, to re-dissolve the material that precipitates in heptane on the PTFE-packed column. The area of this second peak can be used to calculate a value which correlates with gravimetric asphaltene content. Currently the gravimetric procedure to determine asphaltenes takes about 24 h. The automated procedure takes 30 min. Results for four series of original and pyrolyzed residua were compared with data from the gravimetric methods. Methods based on the new on-column precipitation and re-dissolution technique provide significantly more detail about the polar constituents oils than the gravimetric determination of asphaltenes.     

Devolatilization in the temperature range 300-600 K of liquids derived from wood pyrolysis and gasification

A thermogravimetric system, previously developed for solid fuel degradation, has been modified to examine liquids obtained from conventional pyrolysis and updraft gasification of beech wood. Thermogravimetric curves in air show two main reaction stages. The first (temperatures ≤600 K) concerns evaporation, formation and release of gases and formation of secondary char (coke). Then, at higher temperatures, heterogeneous combustion of secondary char takes place. A reliable procedure has been developed to carry out the first stage under assigned temperature using a PID controller and the applied heat flux as the manipulated variable. It has been found that the pyrolysis temperature does not affect significantly weight loss dynamics and amount of secondary char (approximately equal to 20% of the liquid on a dry basis). The thermogravimetric curves are well predicted by a global mechanism consisting of three parallel first-order reactions (activation energies of 66, 32 and 36 kJ/mol, respectively). Due to strong physico-chemical transformations (sample swelling and solidification) associated with secondary char formation, it is not possible to avoid ignition during heterogeneous combustion. Therefore, this reaction stage should be investigated separately after collection and adequate re-preparation of the charred sample.     

Free volume behavior in spincast thin film of polystyrene by energy variable positron annihilation lifetime spectroscopy

Free volume behavior in polystyrene thin films with thickness ranging from 22 to 1200 nm on silicon substrates was studied by energy variable positron annihilation lifetime spectroscopy (EVPALS). The films were prepared by spincasting from toluene solutions of 0.5-5.0 wt% polystyrene with M_w = 1?090?000 g/mol. Distinct deviations from bulk polystyrene in thermal expansion of the free volume holes and the glass transition temperature associated with free volume behavior were observed for the thinnest film with 22 nm thickness, indicating its exclusively high chain mobility. Comparison of the polystyrene concentration in the precursor solution around the overlap concentration suggests that the high chain mobility is due to less entangled chains caused by rapid removal of the solvent from the diluted solution in order to prepare very thin film.     

Steam gasification reactivity of char from rapid pyrolysis of bio-oil/char slurry

A slurry of bio-oil and char originating from wood pyrolysis is a promising gasifier feed-stock because of its high energy density. When such a slurry is injected into a high temperature gasifier it undergoes a rapid pyrolysis yielding a char which then reacts with steam. The char produced by pyrolysis of an 80 wt% bio-oil/20 wt% char mixture at heating rates of 100-10,000 °C/s was subjected to steam gasification in a thermogravimetric analyzer. The original wood char from the bio-oil production was also tested. Gasification was conducted with 10-50 mol% steam at temperatures from 800 to 1200 °C. Reactivity of the slurry chars increased with pyrolysis heating rate, but was lower than that of the original chars. Kinetic parameters were established for a power-law rate model of the steam-char reaction, and compared to values from the literature. At temperatures over 1000 °C, the gasification rates appeared to be affected by diffusional resistance.     

Kinetic study of mullite growth in sanitary-ware production by in situ HT-XRPD. The influence of the filler/flux ratio

The mullitisation kinetics in a sanitary-ware-like precursor system is here investigated by means of high-temperature X-ray powder diffraction, as a function of the filler/flux ratio. We used a blend based on kaolinite (50 wt%), quartz (10-28 wt%) and Na-feldspar (22-40 wt%). The results show that the content of feldspar boosts the formation of mullite as proven by the apparent activation energy values determined, ranging from 394 to 1111 kJ/mol, and giving a dE_a/dx_feldspar ∼ −23 kJ/mol/wt (x_feldspar = feldspar weight fraction). The mullitisation temperature has also been observed to depend on the Na-feldspar content, inasmuch as the sample bearing the smallest amount of feldspar flux exhibits a mullite growth onset between 1100 and 1150 °C, that is at a temperature about 50 °C higher than the one observed in the richer blends. The mullitisation kinetic process is in this work described as a one-mechanism transformation, satisfactorily formalised by Avrami-Erofeyev equation.     

Upgrading of bitumen with formic acid in supercritical water

Upgrading of bitumen was examined with formic acid in supercritical water (SCW) from 673 to 753 K and at a water/oil ratio from 0 to 3. Decomposition of bitumen in SCW + HCOOH gave higher conversions of asphaltene and lower coke yields than those of pyrolysis or with only SCW. Decomposition of bitumen was also conducted in SCW + H₂, SCW + CO, toluene and tetralin, which revealed that decomposition of asphaltene was promoted and coke formation was suppressed when using SCW + HCOOH. In SCW + HCOOH, an increase in the water/oil ratio promoted both decomposition of asphaltene and suppression of coke formation. Formic acid in SCW seemed to enhance the conversion of bitumen to lower molecular weight compounds because formic acid seems to produce active species in SCW. The low temperature region (ca. 723 K) was suitable for upgrading bitumen with formic acid in SCW since coke formation was strongly promoted at high temperature (>753 K). A reaction model was proposed and the model predicted that hydrogenation of the asphaltene core was important for the suppression of coke formation.     

Pyrolysis of scrap printed circuit board plastic particles in a fluidized bed

Pyrolysis behavior and corresponding pyrolysis products of printed circuit board plastic particles (PCBP particles) were investigated in a fluidized bed using TG-FTIR analysis system. PCBP particles were separated from crashed printed circuit boards using fluidized beds, 354 μm crashed plastic particles were pyrolyzed at the temperature ranging from 20 to 900 °C by a thermogravimetric analyzer. Two stages of decomposition were identified for PCBP particles under nitrogen conditions. The activation energy was 90.49 kJ/mol for the first-stage reaction and 137.80 kJ/mol for the second-stage reaction. Further, gas products, liquid products, and solid residues yielded in the fluidized bed were analyzed using an elemental analyzer and FTIR. It has been found that the liquid yields increased with an increase in pyrolysis temperature, and with an increase in superficial gas velocity. The main compositions of liquid products were aromatic compounds including substituted benzenes. Whereas, the solid products mainly contained char and fiberglass.     

Simulated delayed coking characteristics of petroleum residues and fractions by thermogravimetry

Simulated delayed coking characteristics of five petroleum residues from various sources in China and four fractions from one of the residues were investigated by thermogravimetry (TG), and interactions among the fractions were thus revealed. Results showed that properties of these petroleum residues and fractions varied over a broad range. The coke yields from residues were closely related to their carbon residues and those from the fractions varied much. Apparent thermal-cracking activity was in the order saturates > aromatics > resins > asphaltenes, while actual overall cracking intensity appeared in reverse order when measured by the heat effect derived from differential thermal analysis (DTA). The apparent cracking reactions of the fractions and their parent residue could be described in first order kinetics in two coking temperature zones with activation energies being 75–120 kJ mol^− 1 and 130–210 kJ mol^− 1. Saturates promoted coke formation from other fractions, while aromatics inhibited coke formation from both resins and asphaltenes; the coke yield from a residue was smaller than that by physical summation based on residue's compositional fractions. It is thus possible to inhibit coke formation and enhance liquid distillate production by delayed coking of certain mixed petroleum residues.     

Transesterification of soybean oil with nano-MgO or not in supercritical and subcritical methanol

Nano-MgO can apparently improve the transesterification reaction of soybean oil with supercritical/subcritical methanol. The variables affecting the yield of methyl ester during the transesterification reaction, such as the catalyst content, reaction temperature and the molar ratio of methanol to soybean oil were investigated and compared with those of non-catalyst. When nano-MgO was added from 0.5 wt% to 3 wt%, the transesterification rate increased evidently, while the catalyst content was further enhanced to 5 wt%, little increased in yield. It was observed that increasing the reaction temperature had a favorable influence on methyl ester yield. In addition, for molar ratios of methanol to soybean oil ranging from 6 to 36, the higher molar ratios of methanol to oil was charged, the faster transesterification rate was obtained. When the temperature was increased to 533 K, the transesterification reaction was essentially completed within 10 min with 3 wt% nano-MgO and the methanol/oil molar rate 36:1. Such high reaction rate with nano-MgO was mainly owing to the lower activation energy (75.94 kJ/mol) and the higher stirring.     

Catalytic oxidative desulfurization of diesel utilizing hydrogen peroxide and functionalized-activated carbon in a biphasic diesel-acetonitrile system

This paper presents the development of granular functionalized-activated carbon as catalysts in the catalytic oxidative desulfurization (Cat-ODS) of commercial Malaysian diesel using hydrogen peroxide as oxidant. Granular functionalized-activated carbon was prepared from oil palm shell using phosphoric acid activation method and carbonized at 500 °C and 700 °C for 1 h. The activated carbons were characterized using various analytical techniques to study the chemistry underlying the preparation and calcination treatment. Nitrogen adsorption/desorption isotherms exhibited the characteristic of microporous structure with some contribution of mesopore property. The Fourier Transform Infrared Spectroscopy results showed that higher activation temperature leads to fewer surface functional groups due to thermal decomposition. Micrograph from Field Emission Scanning Electron Microscope showed that activation at 700 °C creates orderly and well developed pores. Furthermore, X-ray Diffraction patterns revealed that pyrolysis has converted crystalline cellulose structure of oil palm shell to amorphous carbon structure. The influence of the reaction temperature, the oxidation duration, the solvent, and the oxidant/sulfur molar ratio were examined. The rates of the catalytic oxidative desulfurization reaction were found to increase with the temperature, and H₂O₂/S molar ratio. Under the best operating condition for the catalytic oxidative desulfurization: temperature 50 °C, atmospheric pressure, 0.5 g activated carbon, 3 mol ratio of hydrogen peroxide to sulfur, 2 mol ratio of acetic acid to sulfur, 3 oxidation cycles with 1 h for each cycle using acetonitrile as extraction solvent, the sulfur content in diesel was reduced from 2189 ppm to 190 ppm with 91.3% of total sulfur removed.     

The effect of SiC addition on the crystallization kinetics of atmospheric plasma–sprayed basalt-based coatings

The crystallisation kinetics of the conversion of a glass coating layer made from a mixture of natural basalt volcanic rock and SiC into glass-ceramic have been investigated. The process depends on the crystallisation temperature, time and amount of the SiC added. Coating powders were prepared from pure basalt and from basalt containing 10–50 wt% SiC. The powders were coated by an atmospheric plasma spray technique on the pre-coated AISI 1040 steel substrate with Ni–Al. The coating layer was vitrified by sudden cooling. The amorphous structure of the coatings was verified by X-ray diffraction (XRD) analysis. To obtain glass-ceramic, coatings were subjected to crystallisation heat treatment in an argon atmosphere. Crystallisation heat treatment temperatures of 800 °C, 900 °C and 1000 °C were chosen by using DTA. After the heat treatment process, augite, ferrian-diopsite, diopside, albite, andesine, and moissonite phases formed in the coating layer and were verified by XRD analysis. The crystallisation activation energies were determined to be between 323.4 kJ/mol and 253.2 kJ/mol, depending on SiC addition. The crystallisation activation energies decreased with increasing amounts of SiC addition. The Avrami parameters of the crystallisation process varied between 1.60 and 3.33, which indicates that internal crystallisation dominated for all of the compositions.     

A kinetic study of the esterification of free fatty acids (FFA) in sunflower oil

The kinetics of the esterification of free fatty acids (FFA) in sunflower oil with methanol in the presence of sulphuric acid at concentrations of 5 and 10 wt% relative to free acids as catalyst and methanol/oleic acid mole ratios from 10:1 to 80:1 was studied. The experimental results were found to fit a first-order kinetic law for the forward reaction and a second-order one for the reverse reaction.The influence of temperature on the kinetic constants was determined by fitting the results to the Arrhenius equation. The energy of activation for the forward reaction decreased with increasing catalyst concentration from 50 745 to 44 559 J/mol.Based on the experimental results, a methanol/oleic acid mole ratio of 60:1, a catalyst (sulphuric acid) concentration of 5 wt% and a temperature of 60 °C provided a final acid value for the oil lower than 1 mg KOH/g oil within 120 min. This is a widely endorsed limit for efficient separation of glycerin and biodiesel during production of the latter.     

Pyrolysis and combustion kinetics of Fosterton oil using thermogravimetric analysis

Thermogravimetric analysis (TGA) was used to examine the thermal behavior of Fosterton oil mixed with reservoir sand. TGA experiments were performed in nitrogen and air atmospheres at the heating rate of 10 °C/min up to 800 °C. In this study, four sets of TGA runs were performed to examine the thermal behavior of Fosterton whole oil, and the coke sample derived from the whole oil. Similar to previous studies in the literature, we also observed low-temperature oxidation (LTO), fuel deposition (FD), and high-temperature oxidation (HTO) in the non-isothermal combustion experiment. Higher activation energy values were obtained in reaction regions at higher temperatures. The mean activation energy for whole oil in nitrogen and air atmospheres was 33 and 126 kJ/mol, respectively. Fresh coke samples derived from whole oil were subjected to isothermal combustion at different temperatures from 375 to 500 °C. Arrhenius model was used to obtain the kinetic parameters from the TGA data. From the model, the Arrhenius parameters such as activation energy (E = 127 kJ/mol) and the pre-exponential factor (A = 1.6 × 10⁸/min) were determined for the coke combustion. The results showed a close agreement between the kinetic model and experimental data for different combustion temperatures. It was observed that the apparent order of combustion reaction for different temperatures approach unity.     

Preparation of natural gas adsorbents from high-sulfur petroleum coke

HSPC (high-sulfur petroleum coke) has been used as precursor in the preparation of natural gas adsorbents with chemical activation. The effects of activating parameters, such as activating temperature and duration, on the pore-structure of adsorbents and methane uptake were investigated systematically in this study. The results show that the adsorbents derived from HSPC have comparable pore-structural characteristics and methane uptake to that derived from LSPC (low-sulfur petroleum coke). As evidenced by methane adsorption measurements, the highest deliverable capacity of methane, 129.7 v/v at 3.5 MPa and 25 °C, is obtained on HSR4 prepared at activating agent/coke mass ratio of 4:1. Furthermore, sulfur distribution analyses show that the sulfur in HSPC was almost removed by chemical activation and that sulfur content of as-synthesized adsorbent was as low as 0.18 wt% for HSR4. This study shows that HSPC could be used potentially as a good precursor to prepare high quality adsorbents with lower cost.     

Comparison of the thermal reactivities of isolated lignin and holocellulose during pyrolysis

Woody shells of Turkish hazelnuts which are rich in lignin content offer an important potential as a renewable energy source. Hence, this study focuses on the investigation of the thermal reactivities of the real macromolecular ingredients of this biomass species. Hazelnut shells were treated with chemicals to isolate its holocellulose (hemicelluloses + cellulose) and lignin. Scanning Electron Microscopy (SEM) images revealed the significant differences between the physical features of the untreated biomass and its isolated ingredients. Thermal properties of the biomass and these ingredients were examined by Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) techniques under non-isothermal pyrolysis conditions from ambient to 900 °C. It was found that unlike holocellulose, lignin slowly decomposes in a wider temperature range, and its decomposition is associated with exothermic heat flow. It was also concluded that the hemicellulosics in holocellulose have very important effects with respect to the char yield and the exothermicity of the process. Besides, inorganics in biomass play a catalytic role during pyrolysis. The activation energies calculated according to Borchardt-Daniels' kinetic model were 64.8 and 51.8 kJ/mol for the pyrolysis of holocellulose and lignin, respectively, and each of them is higher than that for the untreated biomass.     

Correlation between feedstock SARA components and FCC product yields

Daqing, Shengli, Liaohe, Gudao, Dagang and Huabei vacuum residua were subjected to deep solvent fractionation by using the supercritical fluid extraction and fractionation, a novel separation technology recently developed by the State Key Laboratory of Heavy Oil Processing. Each residuum was fractionated to produce deasphalted oil (DAO) at four yield levels: 30, 40, 50 and 60 wt%. The saturates, aromatics, resins and asphaltenes (SARA) composition of each DAO sample was determined, indicating that the saturates and aromatic contents of DAO decreases with increased DAO yield.The DAO samples were reacted in a laboratory scale confined fluidized bed, fluid catalytic cracking (FCC) reactor. The results show that most of the gasoline yields originates from the saturate fraction of DAO. The aromatics fraction of DAO contributes to gasoline and diesel yields. Most of the coke yield is from resin fraction of DAO.Generalized empirical correlations were developed for predicting the FCC gasoline, diesel, light oil and coke yields as a function of feedstock SARA composition. These yield correlations can be used to set the upper limit of feedstock resins content for commercial FCC operations. The implications of feedstock properties on FCC products were discussed.     

Effect of alumina addition on initial sintering of cubic ZrO2 (8YSZ)

The effect of 0–10 wt% alumina addition on the initial sintering of 8 mol% Y₂O₃ cubic ZrO₂ (8YSZ) was studied. Activation energy and initial stage of sintering mechanism were analyzed in order to understand the effect of the alumina in the sintering process. The analysis was carried out using the analytical method for constant rate heating (CRH). The activation energy decreased from 716 to 599 kJ/mol for undoped 8YSZ to 2.16 wt% of alumina–8YSZ, respectively. The mechanism for the initial stage of sintering for <2.16% Alumina–8YSZ changed from grain boundary diffusion (GBD) to volumetric diffusion (VD). With 10 wt% of alumina, the activation energy increased to 854 kJ/mol which was thought due to the change in the initial stage of sintering mechanism from VD to GBD.     

Graphite crystals in blast furnace coke

Graphite was found at several spots on the porous surface of a sample of blast furnace (BF) coke in association with droplets of Si-bearing iron and other inorganic compounds. It occurred in foliated intergrowths and rose-like aggregates of euhedral to subhedral crystals of various size (10 μm-0.7 mm) and morphologies, the generic forms that can be seen in the crystals being basal pinacoid, hexagonal prism and hexagonal dipyramid. The largest crystals have a flake-like habit and are represented by a combination of a basal pinacoid and a hexagonal prism. Graphite crystals that have an ideal hexagonal prism in their cross-section are rarer than distorted forms. There are twins on the dypiramidal composition planes and twins produced by rotation on [0 0 0 1]. The major deformations in the crystals, i.e. detaching, bending and rolling of (0 0 0 1) planes, may be referred to exfoliation phenomena caused by potassium and sodium from circulating BF gases and enforced by the BF gas flows. The formation of graphite crystals on a surface of BF coke, especially those of flake-like morphology with an undeveloped hexagonal prism, possibly decreases its reactivity and can be accompanied by the generation of fines. The graphitic coating on a surface of BF coke can act as a lubricant to facilitate coke pieces sliding over each other thus affecting the mechanical stability of the coke cone in a BF.     

Activation of coal tar derived needle coke with K2CO3 into an active carbon of low surface area and its performance as unique electrode of electric double-layer capacitor

Raw needle coke from coal tar pitch was activated with K₂CO₃ at a coke:carbonate weight ratio of 1:4, to prepare an electrode for an electric double-layer capacitor (EDLC). Although the surface area of the coke activated at 900 °C for 3 h was as small as 20 m²/g, with a very high yield, the coke achieved capacitances per weight and volume of 20 F/g and 20 F/ml, respectively, in the two-electrode system, by charging at 2.7 V. The surface area of KOH-activated coke with a similar ratio (coke:hydroxide = 1:4, wt:wt) was over 2300 m²/g, and it exhibited capacitance per weight and volume values of 42 F/g and 17 F/ml, respectively. The coke activated by K₂CO₃ was found to be further activated by the charging. This electrochemical activation, which has been reported as activation in an electric field, was investigated by cyclic voltammetry in order to clarify it. The graphitic and pore structures of the coke after the electrochemical activation were analyzed by XRD to confirm retention of the graphene structure. Xe-NMR showed that the formation of small new pores was induced in the cathode material, increasing the surface area from 6 m²/g to 18 m²/g before use, although the pore volume was around 0.015-0.017 m³/g both before and after the charging. This activation with K₂CO₃ and a deeper understanding of the activation on charging suggest future directions for the preparation of electrode carbon for EDLCs.     

Preparation of high solids stable translucent nanolatexes of MMA/BA copolymers and MMA/BA/Veova-10 terpolymers with low MFFT using green industrial surfactants

In this study, high solids (∼40 wt%) stable translucent nanolatexes of MMA/BA copolymers and MMA/BA/Veova-10 terpolymers with MFFT ≤ 0 °C were synthesized by a modified semi-continuous microemulsion copolymerization. Ammonium persulfate was used as initiator and a redox system for post-polymerization to reduce the free monomers and achieve over 99.9% conversion. Methacrylic acid or acrylic acid at 1 wt% (calculated on monomers) and a combination of various “green” industrial anionic and non-ionic surfactants free of alkylphenol ethoxylates (APEO-free) at low concentrations (up to 10 wt% on monomers) were used. The resulting latexes were composed of polymer nanoparticles with average diameter size 50–80 nm and low polydispersity index. These friendly to the environment latexes can be potentially used as impregnation primer instead of classic solvent acrylic primers in architectural coatings.