Low viscosity COM (coal oil mixture) using tall-oil as an additive

Tall oil, an inexpensive by-product from pulp manufacturing (about one-tenth of the cost to those of ordinary surfactants), was found as an effective additive for COM (coal oil mixture) to provide good stability and low viscosity. The viscosity of COM (coal concentration: 50%) was as low as 2 Pa at 70 °C after 25 day-storage by addition of only 1% of tall-oil to COM. Tall-oil supported an increase in concentration of coal from 46% to 52.5%, maintaining usable viscosity. Structural viscosity (SV) of COM was proposed by the authors and defined as follows: SV = η(2.2)−η(22); where η(2.2) and η(22) are the viscosities at low shear rate (2.2 s⁻¹) and high shear rate (22 s⁻¹), respectively. The SV was found to be a good parameter for predicting the sedimentation stability and the viscosity of COM after long-term storage in the case of Miike-COM.     

Study of the treatment of subbituminous coals by NaOH solutions

A subbituminous coal from La Union (Chile) has been treated with aqueous NaOH solutions. The quantity of coal solubilized and the elimination of ash was found to increase with increase in hydrolysis time, temperature and NaOH concentration and with decrease in particle size. Coal solubilization reached a maximum with respect to NaOH concentration in the range studied. The largest yield of solubilized products was 28 wt%, this occurred after 8 h of hydrolysis at 80 °C using an NaOH concentration of 10 g dm⁻³ and coal having a particle size between 125 and 177 μm. In the range of conditions studied, the greatest decrease in the ash yield of the undissolved coal was ≈ 29 wt%. Under the same conditions, the total sulphur content of the coal decreased by 30 wt%.     

Coprecipitated iron-containing catalysts (Fe-Al2O3, Fe-Co-Al2O3, Fe-Ni-Al2O3) for methane decomposition at moderate temperatures: Part II. Evolution of the catalysts in reaction

Coprecipitated Fe-Al₂O₃, Fe-Co-Al₂O₃ and Fe-Ni-Al₂O₃ catalysts is shown to be very efficient in carbon deposition during methane decomposition at moderate temperatures (600–650 °C). The carbon capacity of the most efficient bimetallic catalysts containing 50–65 wt.% Fe, 5–10 wt.% Co (or Ni) and 25–40 wt.% Al₂O₃ is found to reach 145 g/g_cat. Most likely, their high efficiency is due to specific crystal structures of the metal particles and formation of optimum particle size distribution. According to the TEM data, catalytic filamentous carbon (CFC) is formed on them as multiwall carbon nanotubes (MWNTs). The phase composition of the catalysts during methane decomposition is studied using a complex of physicochemical methods (XRD, REDD, Mössbauer spectroscopy and EXAFS). Possible mechanisms of the catalyst deactivation are discussed.     

Oil production from algal cells of Dunaliella tertiolecta by direct thermochemical liquefaction

Algal cells of Dunaliella tertiolecta with a moisture content of 78.4 wt% were converted directly into oil by thermochemical liquefaction at around 300°C and 10 MPa. The oil yield was about 37% on an organic basis. The oil obtained at a reaction temperature of 340°C and holding time of 60 min had a viscosity of 150–330 mPas and a calorific value of 36 kJ g⁻¹, comparable to those of fuel oil.     

Chlorination kinetics of pyrite mineral in two Turkish lignites

The kinetics of the chlorination of pyrite in two Turkish lignites in water and water-carbon tetrachloride media at ambient pressure ( 610 mm Hg) are investigated. The effects of speed of stirring (5–20 s⁻¹), particle size (74–88, 150–180 and 250–425 μm), temperature (13–70°C) and reaction time (0–18 000 s) were studied. The experimental data were analyzed on the basis of the unreacted shrinking core model. The fine pyrite particles are assumed to be embedded inside the coal particles. The rate-controlling step was found to be diffusion of chlorine through the ash (the coal matrix). The activation energies were calculated as 25.1 kJ mol⁻¹ for Dada i coal in water medium and 25.0 kJ mol⁻¹ for Mengen coal in water-carbon tetrachloride medium.     

The influence of zeolite acidity for the coupled hydrogenation and ring opening of 1-methylnaphthalene on Pt/USY catalysts

The influence of framework and extraframework composition of USY zeolite on the catalytic performance of bifunctional Pt/USY (1 wt.% Pt) catalysts for the coupled hydrogenation and ring opening of 1-methylnaphthalene (1-MN) has been studied on a continuous fixed bed high pressure reactor. All Pt/USY catalysts showed very high methylnaphthalene (MN) conversions under the reaction conditions studied (T=300–375 °C, P=4.0 MPa, WHSV=2 h⁻¹, H₂/1-MN=30 mol/mol). Product yields and selectivities were mainly determined by the zeolite composition (i.e. acidity). Selectivity to products with the same number of carbon atoms than the feed (C11) increased, at constant temperature, with decreasing the Brönsted acidity of the USY zeolite, that is, with decreasing the concentration of framework Al (FAL) and increasing extraframework Al (EFAL). Selectivity to high cetane ring opening products (ROP=C11-alkylbenzenes (C11AB) and C11-alkylcycloalkanes) within the C11 fraction was higher for the less acidic catalysts. A maximum yield of ROP of ca. 15 wt.% at a C11 yield of ca. 73 wt.% was obtained at 350 °C (P=4.0 MPa, WHSV=2 h⁻¹, H₂/1-MN=30 mol/mol) for a USY zeolite with an intermediate degree of dealumination (a₀=24.33 Å) and containing all the EFAL (bulk Si/Al ratio of 2.6). For this catalyst, a slight increase in ROP yield (ca. 17 wt.%) at similar C11 yield (ca. 74 wt.%) was obtained by working at lower temperature (300 °C) and lower space velocity. Increasing the reaction pressure above 4.0 MPa had only a marginal influence on product yields and selectivities.     

Study on the washability of the Kaitai coal, Guizhou Province China

Tonnage of coal samples were collected from Kaitai Coal field, Puan County, Guizhou Province and sieved into different particle size catalogs. The analysis of the overall coal suggested that the coal has low ash but high sulfur content of 3.17 wt.% with medium to high volatile content. The heating value of the coal is 31.668 mJ/kg.The coal sample with different particle size ranges were tested for float-sink using gravity separation method, in which ZnCl₂ solutions with different density are used. It is showed that decreasing sulfur to 2.12 wt.% can give coal yield of 94.55%, suggesting that the coal's floatability is good with sulfur. The coal yield is only 85.4% when reducing sulfur to 1.5 wt.%, and 76.7% when sulfur is decreased to 1.2% through the ZnCl₂ float-sink process. The δ ± 0.1 is 20.55, which is in the 20.1-30 range, suggest that Kaitai coal is difficult to float-sink for depyritisation.Characterization of the floated coal at different sizes showed that the organic sulfur may mainly be present in the small size, the pyrite sulfur is mainly present in the coal with bigger particle size, which can be easily removed through float-sink process. The ash in the small particle sized coal is mainly from kaolinite and quartz, while the pyrite is the main ash contributor to the coal with big size.     

Gold catalysts supported on mesoporous titania for low-temperature water–gas shift reaction

Mesoporous titania with high surface area and uniform pore size distribution was synthesized using surfactant templating method through a neutral [C₁₃(EO)₆–Ti(OC₃H₇)₄] assembly pathway. The different gold content (1–5 wt.%) was supported on the mesoporous titania by deposition–precipitation (DP) method. The catalysts were characterized by X-ray diffraction, TEM, SEM, N₂ adsorption analysis and TPR. The catalytic activity of gold supported mesoporous titania was evaluated for the first time in water–gas shift reaction (WGSR). The influence of gold content and particle size on the catalytic performance was investigated. The catalytic activity was tested at a wide temperature range (140–300 °C) and at different space velocities and H₂O/CO ratios. It is clearly revealed that the mesoporous titania is of much interest as potential support for gold-based catalyst. The gold/mesoporous titania catalytic system is found to be effective catalyst for WGSR.     

Effect of ammonium polyacrylate on rheology of anatase TiO2 nanoparticles dispersed in silicon alkoxide sols

Ammonium polyacrylate (NH₄PA) was introduced into powdered mixtures consisting of anatase-structured TiO₂ nanoparticles and silicon alkoxide precursors at the sol level, and the rheological behavior of the mixtures was examined under various solid loadings (φ=0.05–0.13 in volumetric ratios), shear rates (  s⁻¹) and NH₄PA concentrations. The alkoxide precursors were mixtures of tetraethyl orthosilicate (TEOS, Si(OC₂H₅)₄), ethyl alcohol (C₂H₅OH), H₂O and HCl in a constant [H₂O]/[TEOS] ratio of 11. The nanoparticle–sol mixtures generally exhibited a pseudoplastic flow behavior over the shear-rate regime examined. The NH₄PA appeared to serve as an effective surfactant which facilitates the suspension flow by reducing the flow resistance at low NH₄PA concentrations. At φ=0.10, a viscosity reduction ca. 85% was found at  s⁻¹ when the NH₄PA concentration was held at 2.5 wt.% of the solids. As the NH₄PA exceeded a critical level, e.g., [NH₄PA]≥3.0 wt.%, the NH₄PA acted as a catalyst which quickly turned the TiO₂–silica sol mixtures (φ=0.10) into a gelled structure, resulted in a pronounced increase of mixture viscosity. The maximum solids concentration (φ_m) of the mixtures was experimentally determined from a derivative of relative viscosity, i.e., (1−η_r^−1/2)–φ dependence. The estimated φ_m increased from 0.127 to 0.165 when NH₄PA of 0.5 wt.% was introduced into the TiO₂–silica sol mixtures.     

Rapid synthesis of silicalite-1 seeds by microwave assisted hydrothermal treatment

The objective of this work was to evaluate the use of microwave (MW) heating for the rapid synthesis of small and homogeneous silicalite-1 seeds. The influence of the chemical composition of the starting sol, the sol stirring time at room temperature and the hydrothermal synthesis conditions on the characteristics of the derived seeds have been studied. The silicalite-1 seeds were characterized by their size, shape, homogeneity, aggregation and yield. The TPAOH template concentration was an important parameter for the reaction yield, as well as particle size and aggregation. Starting from an optimized formulation (SiO₂:0.4TPAOH:19.5H₂O:4C₂H₅OH), we first demonstrated that MW heating drastically shortens the synthesis duration time because long sol ageing (maturation–nucleation) times are not required in this case. On the other hand the hydrothermal synthesis parameters (MW power, temperature, duration, number of synthesis steps) have been optimized in order to control the morphological characteristics and yield of the silicalite-1 crystals. Although an original fibrous morphology was obtained for very short MW assisted hydrothermal synthesis times (10–30 min), very small individual seed (size of ≈50–60 nm) were obtained after only 110–150 min, starting from sols aged for either 1 or 264 h.     

Hydrogen production from catalytic gasification of cellulose in supercritical water

Interests in large-scale use of biomass for energy and in hydrogen are motivated largely by global environmental issues. Cellulose and sawdust were gasified in supercritical water to produce hydrogen-rich gas in this paper, and Ru/C, Pd/C, CeO₂ paticles, nano-CeO₂ and nano-(CeZr)_xO₂ were selected as catalysts. The experimental results showed that the catalytic activities were Ru/C > Pd/C > nano-(CeZr)_xO₂ > nano-CeO₂ > CeO₂ particle in turn. Low-concentration sodium carboxymethylcellulose (CMC) (2–3 wt.%) was mixed with particulate biomass and water to form a uniform and stable viscous paste which can be efficiently gasified. The 10 wt.% cellulose or sawdust with CMC can be gasified near completely with Ru/C catalyst to produce 2–4 g hydrogen yield and 11–15 g potential hydrogen yield per 100 g feedstock at the condition of 500 °C, 27 MPa, 20 min residence time in supercritical water.     

Hydrodesulfurization of model diesel using Pt/Al2O3 catalysts prepared by supercritical deposition

Pt/Al₂O₃ catalysts with Pt loadings ranging from 0.5 to 11 wt.% were synthesized by supercritical carbon dioxide (scCO₂) deposition method. Transmission electron microscopy (TEM) images showed that the synthesized catalysts contained small Pt nanoparticles (1–4 nm in diameter) with a narrow size distribution, no observable agglomeration, and uniformly dispersed on the alumina support. The catalysts were found to be active for hydrodesulfurization of dibenzothiophene (DBT) dissolved in n-hexadecane (n-HD) without sulfiding the metal phase. The reaction proceeded only via the direct hydrogenolysis route in the temperature range 310–400 °C and at atmospheric pressure. The activity increased with increasing the metal loading. Increasing [H₂]₀/[DBT]₀ by either increasing [H₂]₀ or decreasing [DBT]₀, increased the DBT conversion. At a fixed weight hourly space velocity and feed concentration, conversion did not increase with increasing temperature beyond 330 °C. The presence of toluene inhibited the catalyst activity presumably due to competitive adsorption between DBT and toluene. Under the operating conditions, the reaction was far from equilibrium.     

Effect of Re loading on the structure, activity and selectivity of Re/C catalysts in hydrodenitrogenation and hydrodesulphurisation of gas oil

A series of Re-containing catalysts supported on activated carbon, with Re loading between 0.74 and 11.44 wt.% Re₂O₇, was prepared by wet impregnation and tested in the simultaneous hydrodesulphurisation (HDS) and hydrodenitrogenation (HDN) of a commercial gas oil. Textural analysis, XRD, X-ray photoelectron spectroscopy (XPS) and surface acidity techniques were used for physicochemical characterisation of the catalysts. Increase in the Re concentration resulted in a rise in the HDS and HDN activity due to the formation of a monolayer structure of Re and the higher surface acidity. At Re concentrations >2.47 wt.% Re₂O₇ (0.076 Re atoms nm⁻²) the reduction in the catalytic activity was related to the loss in specific surface area (BET) due to reduction in the microporosity of the carbon support. The magnitude of the catalytic effect was different for HDS and HDN, and depended strongly on the Re content and reaction temperature. The apparent activation energies were about 116–156 kJ mol⁻¹ for HDS and 24–30 kJ mol⁻¹ for HDN. This led to a marked increase in the HDN/HDS selectivity with decreasing temperature (values >3 at 325 °C), due to the large differences in the apparent activation energies of HDS and HDN found for all catalysts. A gradual increase in the HDN/HDS selectivity with increased Re loading was also found and related to the observed increase of catalyst acidity. The results are compared with those obtained for a series of Re/γ-Al₂O₃ catalysts.     

Differential scanning calorimetry study of linseed oil cured with metal catalysts

Differential scanning calorimetry (DSC) has been used to study the autoxidative curing process of linseed oil catalyzed by conventional metal driers and two metal sol-gel precursors, Ti(Oi-Pr)₂(acac)₂ and Ti(Oi-Pr)₄, at elevated temperatures. Linseed oil resins with a range of 0–5.0 wt.% metal sol-gel precursor and 0–9.0 wt.% zirconium dric have been investigated by both dynamic and isothermal methods. The onset, peak and end temperatures of the reaction exotherms were observed as a function of metal catalyst type and content. The Borchardt and Daniels kinetics method was used to quantify the heat of reaction of the dynamic DSC scans. The indention hardness of the resultant coatings in the DSC sample pans was measured as an indication of crosslink density. The inclusion of small quantities of metal catalyst (0–5.0 wt.% titanium alkoxide, 0–2.0 wt.% zirconium drier) caused the reaction exotherm to broaden and shift to lower temperatures. At higher metal catalyst content (>5.0 wt.% Ti(Oi-Pr)₂(acac)₂ or 5.0 wt.% Ti(Oi-Pr)₄) the reaction exotherms became imperceptible. Overall, as the metal catalyst content was increased, the heat of reaction decreased while indention hardness increased. The effects of the two sol-gel precursors on the reaction exotherms were similar to the effects of conventional driers. Combinations of conventional driers were also studied.     

Pyrolysis of oil sand from the Whiterocks deposit in a rotary kiln

A rotary kiln reactor was evaluated for thermal recovery of oil from Utah oil sands. A series of continuous-flow pyrolysis experiments was conducted. Process variables investigated included temperature (748–848 K), solids retention time (10–27 min) and sweep gas flow rate (1.27–2.83 m_s³ h⁻¹). The results indicated that the pyrolysis temperature and the solids retention time were the two most important variables affecting the liquid and gas yields. The liquid yield (C₅⁺]) decreased and the gas yield (C₁–C₄) increased with increasing temperature. The liquid yield increased with decreasing solids retention time, while the gas yield decreased. No significant effect of the sweep gas flow rate on the product distribution and yields was observed. The quality of the bitumen-derived liquids was significantly better than that of the bitumen. A preliminary process kinetics model which conforms to the observed trends was proposed.     

Hydropyrolysis of Alberta coal and petroleum residue using calcium oxide catalyst and toluene additive

Hydropyrolysis of a mixture of Alberta coal and Athabasca bitumen was carried out in a batch reactor using calcium oxide as an alternate catalyst and the results were compared with those of widely used iron oxide and well-known NiMo/Al₂O₃ catalysts. Most of the reactions were done at temperatures of 500–540°C, residence time of 1 min and hydrogen pressure of 3.4 MPa. Maximum distillable oil (below 523°C) yield of 55 wt% and pitch conversion of 62 wt% were obtained in the presence of CaO or Fe₂O₃ and these values were higher than those without catalyst, although NiMo/Al₂O₃ catalyst gave much higher oil yield and pitch conversion. Catalyst concentration (above 2 wt%) has no consequence upon the distribution of various product fractions.

In another study, addition of 15% toluene to the feed in the absence of catalyst led to higher distillable oil yield (68 wt%) and pitch conversion (72 wt%) in the hydroconversion of coal and bitumen mixture. Increase in toluene concentration from 15 to 50 wt% had no positive effect on the product yields.     

Preparation and rheology of biochar, lignite char and coal slurry fuels

Slurries of an Oil Mallee biomass char, a low rank coal char and sub-bituminous coals were prepared by mixing the finely milled solids with water and a range of additives including polyacrylic acid, charged copolymers D101 and D102, and sucrose. The resultant slurries were subjected to rheological characterizations including apparent viscosity and yield stress. The effect of the solid type, particle size distribution, and the additives on preparation of highly loaded slurries with the desired rheological behaviour were systematically examined in terms of apparent viscosity and yield stress. The additives D101 and D102 were found to be most effective in producing highly loaded suspensions with a low apparent viscosity and yield stress. Particle size distributions were manipulated to improve the solid loading. Suspensions produced by powder mixture containing equal weight precent of 30 min and 1 min milled powders gave a broad size distribution and is very effective in increasing the solid loading in slurries. The significant improvement in the solid loading was shown to be achieved by (i) increasing particle packing density via size distribution control and (ii) minimising the strength and number of the interactions between colloidal particles. The maximum solid loading of flowable (or relatively low apparent viscosity) slurries achieved with the Oil Mallee char is ∼40 wt.%, with the sub-bituminous coals 56-63 wt.%, and with the lignite char ∼65 wt.%. This study has shown that for low rank coals such as lignite, thermal and densification treatment is essential to achieve the solid loading of slurry fuel.     

Particle characteristics of a stable fluidized bed aerosol generator

An aerosol generator consisting of a vibrating system for feeding dust into a fluidized bed was developed and tested to determine its dust output characteristics. The dust feed unit can produce 0–40 g min⁻¹ of coal dust and shows constant output up to 3 h operation durations. These correspond to mass concentrations of 0–101 g m⁻³ of coal particles for an air flowrate of 395 l min⁻¹ through the aerosol generator. The aerosolized coal particles show constant particle size distribution with time for up to h of testing under varied operation parameters. The normalized particle size distribution remains almost identical for a given feed material for a range of dust loadings. The time required to reach steady state aerosol generation is negligible for the sizes of coal particles used in this investigation.     

Fischer–Tropsch synthesis on monolithic catalysts of different materials

Monolithic structures made of cordierite, γ-Al₂O₃ and steel have been prepared as catalysts and tested for Fischer–Tropsch activity. The monoliths made of cordierite and steel were washcoated with a 20 wt.% Co–1 wt.% Re/γ-Al₂O₃ Fischer–Tropsch catalyst whereas the γ-Al₂O₃ monoliths were made by direct impregnation with an aqueous solution of the Co and Re salts resulting in a loading of 12 wt.% Co and 0.5 wt.% Re. The activity and selectivity of the different monoliths were compared with the corresponding powder catalysts.

Higher washcoat loadings resulted in decreased C₅₊ selectivity and olefin/paraffin ratios due to increased transport limitations. The impregnated γ-Al₂O₃ monoliths also showed similar C₅₊ selectivities as powder catalysts of small particle size (38–53 μm). Lower activities were observed with the steel monoliths probably due to experimental problems.     

Viscosity measurements and empirical predictions for fluxed Australian bituminous coal ashes

Recent interest in the suitability of Australian bituminous coals for use in integrated gasification-combined cycle (IGCC) technologies has provided the opportunity to determine viscosity data for a range of coal ashes slags fluxed with limestone at the tapping temperatures of entrained flow gasifiers. Experimental viscosity measurements have been made over a range of slag compositions covering the anorthite region at the 0–2.5, 2.5–5, 5–7.5 and 7.5–10 wt% FeO levels of the quaternary SiO₂–Al₂O₃–CaO–FeO system. Contour plots of viscosities at 1450°C for the four FeO ranges are presented as an example for predicting slag behaviour in entrained flow gasifiers. The viscosity measurements have also been fitted empirically using a modified Urbain treatment to give separate models for the four FeO levels. Polynomial expressions are given for the evaluation of viscosities covering the temperature range 1400–1550°C for slags within the compositional range used in the derivation.