Fuel Processing Technology (v.95, #C)

Removal of copper from aqueous solutions by low cost adsorbent-Kolubara lignite by Sonja Milicevic; Tamara Boljanac; Sanja Martinovic; Milica Vlahovic; Vladan Milosevic; Biljana Babic (1-7).
Serbian lignite from “Kolubara” deposit was used as a low cost adsorbent for removal of copper ions (Cu2 +) from aqueous solutions. Lignite was subjected to the elementary and technical analysis as well as BET and FTIR analysis due to complete characterization. Basic comparison between lignite and activated carbon was also done. As a method, batch adsorption procedure was applied. Adsorption efficiency was studied as a function of the initial metal concentration, pH of the solution, contact time, and amount of the adsorbent. Optimum removal of copper ions was achieved at pH values of 5.0. About 90% of copper cations were removed in 5 min of contact time from the solution with the lowest copper concentration (50 mg Cu2 +/l) regardless adsorbent amount, while the same effect of adsorption was achieved in 60 min in case of solutions with higher concentrations of copper. It was concluded that the effect of adsorbent amount on adsorption kinetics is evident but not crucial. It was proved that the experimental results of copper adsorption fit well to a Langmuirian type isotherm which was used to describe monitored adsorption phenomena. The calculated adsorption capacities of lignite for copper adsorption decrease with increasing adsorbent amount. The study proved that tested lignite is very efficient adsorbent material, especially in case of low copper concentration in aqueous solution where the usual methods are either economically unrewarding or technically complicated. This behavior can be explained by FTIR spectrum despite a small specific surface area of lignite. Namely, many bands (peaks) are attributed to the functional groups that they are involved in chemisorption and ionic exchange, basic mechanisms of copper adsorption.► Serbian lignite was used as adsorbent for copper removal from aqueous solutions. ► Influence of concentration, pH, contact time and adsorbent amount was studied. ► Tested lignite is very efficient adsorbent material. ► Copper adsorption results fit well to Langmuirian type isotherm.
Keywords: Adsorption; Lignite; Copper; Kinetics;

Effect of space velocity on the hydrocracking of Light Cycle Oil over a Pt–Pd/HY zeolite catalyst by Alazne Gutiérrez; José M. Arandes; Pedro Castaño; Martin Olazar; Astrid Barona; Javier Bilbao (8-15).
The effect of space velocity (WHSV) has been studied in the single-step hydrocracking of the LCO (Light Cycle Oil) obtained as byproduct in catalytic cracking (FCC) units, over a bifunctional catalyst of Pt–Pd supported on a high acidity HY zeolite. Accordingly, the hydrocracking and hydrodesulphurization conversions and yields of product fractions (medium distillates, naphtha, LPG and dry gas) have been determined. The reaction conditions have been 350 °C, 45 bar, H2/LCO molar ratio of 10. The catalyst reaches a pseudoestable state subsequent to a rapid initial deactivation and maintains a significant activity in this state for the production of medium distillates and naphtha. Studies have been carried on the composition of these streams and their interest for adding to the pools of diesel and gasoline. The results are encouraging for the upgrading of LCO by its hydrocracking over noble metal catalysts, given that they are of high activity.Display Omitted► Pt–Pd catalyst, supported on a very acid HY zeolite is active and stable in the LCO hydrocracking. ► The space velocity is a key factor controlling the selectivity of middle distillates and naphtha. ► To achieve a remarkable diminution of aromatic content of the reaction products a space velocity lower than 1 h− 1 is required.
Keywords: Hydrocracking; LCO; Deactivation; Catalyst; Acidity; Coke; Diesel; Gasoline;

Fluidized bed gasification of coal–oil and coal–water–oil slurries by oxygen–steam and oxygen–CO2 mixtures by Karel Svoboda; Michael Pohořelý; Michal Jeremiáš; Petra Kameníková; Miloslav Hartman; Siarhei Skoblja; Michal Šyc (16-26).
Polish bituminous coal, German brown (subbituminous) coal and rapeseed oil were selected for preparation of coal–oil slurry (COS) and coal–oil in water slurry (COWS) with content of coal about 50 mass%. Laboratory, electrically heated gasifier with fluidized bed (FB) of sand particles was used for the coal slurries gasification with steam–O2 and CO2–O2 mixtures (ER = 0.19–0.23) at temperatures between 800 and 925 °C. FB gasification with mixtures of O2/CO2 (CO2/dry fuel mass ratio 1–2.4) can generate producer gas with LHV values about 8–10 MJ/m3. The heating value of the dry, N2-free producer gas from CO2–O2 gasification is lower in comparison with gasification by steam–O2 mixtures at comparable conditions. The heating value of the producer gas is influenced by a relatively high content of methane, ethylene and BTX compounds. The yield of heavier tar compounds (excluding BTX) is high, exceeding 20 g tar/kg of dry German coal based COS and exceeding 36 g/kg of fuel for Polish coal based COS. Cold gas efficiency is higher for fuel gas from gasification of COS based on the German, subbituminous coal. FB gasification (ER ≈ 0.2) of the COWS prepared from the Polish coal (contents of coal, water and oil 47, 40 and 12 mass% respectively) reduces tar yield approximately to an half (related to gasification of the corresponding COS slurry), but simultaneously moderately reduces the heating value (LHV) of the dry, nitrogen free producer gas.► Study of fluidized bed gasification of coal–oil and coal–water–oil slurries by steam–O2 and CO2–O2 mixtures. ► ER = 0.19–0.23, H2O/dry fuel and CO2/dry fuel mass ratio are in a range 0.4–1 and 0.8–2.4 kg/kg respectively. ► Measurements of producer gas composition, heating value (LHV), gas yield, BTX and tar contents. ► Gasification of coal–water–oil slurries leads to producer gas with lower tar content and lower LHV.
Keywords: Fluidized bed; Gasification; Coal; Slurry; Oil;

Enhanced conversion of tetralin dehydrogenation under microwave heating: Effects of temperature variation by Yindee Suttisawat; Satoshi Horikoshi; Hideki Sakai; Pramoch Rangsunvigit; Masahiko Abe (27-32).
Effects of temperature variation in microwave-induced system of tetralin dehydrogenation on the enhancement of reactivity were investigated. The enhancement of heating ability of Pt-supported activated carbon catalyst (Pt/AC) particle and decreasing of an existing temperature gradient (non-uniformed heat distribution) in tetralin solution under microwave heating and boiling-reflux condition were examined by three methodologies: an employment of Dewar-like insulation reactor (DIR), addition of an ionic liquid as an optional microwave absorber in the system, and optimization of the catalyst to the reactant in the reaction system. The Dewar-like insulation reactor was used to prevent heat loss in the heterogeneous solution. Under microwave heating with DIR, the reaction can be heated approximately 3 °C above the normal boiling point of tetralin. In comparison to the reaction carried out in a conventional reactor, tetralin conversion increased from 31% to 56% under 190 W microwave irradiation. Addition of an ionic liquid to the system to function as a heating promoter remarkably enhanced the heating rate of tetralin. However, the ionic liquid deactivated the activity of the catalyst in the reaction. Optimization of tetralin to Pt/AC catalyst in the reaction system improved heat distribution and showed an interesting result. It was found that the reaction performed under the liquid film state showed the highest tetralin conversion, 69% with the microwave irradiation for 60 min.► Microwave–induced dehydrogenation of tetralin under catalysis of Pt/AC. ► Effect of heat distribution in a microwave-heated heterogeneous reaction. ► Dewar-like insulation reactor is used to preserve heat in microwave heating system. ► Optimization of catalyst/tetralin ratio improves the heat distribution.
Keywords: Microwave; Hydrogen; Tetralin dehydrogenation; Pt catalysis; Ionic liquid;

Ultrasound-assisted synthesis of ethyl esters from soybean oil via homogeneous catalysis by Jeane Q.A. Brito; Creuza S. Silva; Jorge S. Almeida; Maria G.A. Korn; Mauro Korn; Leonardo S.G. Teixeira (33-36).
A transesterification reaction of esters from soybean oil with ethanol assisted by low-frequency ultrasound (20 kHz) was performed in the presence of a potassium hydroxide catalyst. The effects of the following variables on the reaction performance were studied simultaneously through a full two-level factorial design 23: the concentration of the catalyst, the oil:ethanol molar ratio and the sonication time. The three investigated factors significantly affected the yield. Further experimentation was performed using a three-step reaction. An ethyl ester yield of approximately 98% was attained in the third step. The physicochemical properties of the products were compared with the technical limits of biodiesel, and the results suggest that the ultrasound-assisted ethanol transesterification reaction could be a viable and efficient method for the production of quality biodiesel from soybean oil.► A transesterification of esters from soybean oil with ethanol assisted by ultrasound was performed. ► Ethanolysis assisted by ultrasound allows for good conversion with a sonication time of 360 s. ► Ultrasonic irradiation can be an efficient method of producing quality biodiesel from soybean oil and ethanol.
Keywords: Ethyl esters; Soybean oil; Biodiesel; Transesterification; Ethanolysis; Ultrasound-assisted reaction;

This study aims at the assessment of a combined heat and power (CHP) biomass bubbling fluidized bed gasification unit coupled with an internal combustion engine (ICE) by using a comprehensive mathematical model based on the Aspen Plus® process simulator. The model is based on a combination of modules that Aspen Plus simulator provides representing the 3 steps of gasification process (drying, pyrolysis, and oxidation), gas cleaning and ICE. The model is based on mass and energy balances and reaction kinetics. The model was validated by using data obtained by operating a pilot atmospheric bubbling fluidized bed gasifier at Aristotle University of Thessaloniki, fed with olive kernel with a capacity of 1 kg/h and an energy output of 5 kWth, and has showed very good agreement. A sensitivity analysis was further conducted for the investigation of the system's behavior under different temperatures and air equivalence ratios. The proposed model is capable of dealing with a wide variety of biomasses (olive kernel, corn cob/stalks, rapeseed and sunflower stalks) using air as the fluidization agent and to predict the system's performance in terms of cold gas and thermal efficiency.► An Aspen Plus model was formulated for a bubbling fluidized bed biomass gasifier. ► The model was validated against experimental data from a pilot unit. ► A good match was achieved with deviations ranging from 2.1% to 8% for gas compositions. ► The system's behavior under different operating conditions was studied. ► The power output for various types of feedstocks and capacities was predicted.
Keywords: Bubbling fluidized bed gasification; Agro-biomass; Simulation; Aspen Plus; ICE; Efficiency;

Combined gasification of coal and biomass in internal circulating fluidized bed by F. Miccio; G. Ruoppolo; S. Kalisz; L. Andersen; T.J. Morgan; D. Baxter (45-54).
The paper addresses the combined gasification of biomass and brown coal in an internal circulating fluidized bed (ICFB) for generating a valuable producer gas.A primary method for tar abatement and gas improving was adopted, consisting in a Ni-based catalyst in the bed together with sand. The hydrogen concentration in the producer gas was high (up to 35% in the best case, > 20% typically) demonstrating the validity of the ICFB process for co-gasification of coal with biomass. Higher H2 and CO contents and lower tar yields were obtained with greater coal loadings. The tar was reduced by up to three times when changing from inert to a partly catalytic bed, under steam gasification conditions. However, this good figure is contrasted by a rather fast decay in catalytic activity, and a rather low carbon conversion even in presence of the catalyst.A mathematical model based on thermodynamic computations predicts the trend and values of the measured gas concentrations at different steam/fuel ratios, providing useful indications for its optimal choice. The findings of the research reinforce the idea that dual bed gasification is suitable even when a relatively low reactivity fuel is used, such as the brown coal in this study.► The dual-bed gasifier exhibited good performance during the co-gasification of coal and biomass. ► The H2 concentration in the producer gas was high (up to 35% in the best case, > 20% typically). ► The dual bed exhibits enhanced tar abatement compared to other gasification schemes. ► Carbon losses with fines were low thanks to the char circulation between gasifier and combustor.
Keywords: Gasification; Coal; Biomass; Fluidized bed; Hydrogen; Tar;

In this work the microwave-assisted CO2 reforming of CH4 over carbon-based catalysts, carried out in a lab-scale microwave pilot plant, was investigated focusing on the conversions achieved and energy consumption. The activated carbon, FY5, and a heterogeneous mixture of FY5 and an in-lab prepared Ni/Al2O3 were selected as catalysts. Regardless of the catalyst used (FY5 or FY5 + Ni/Al2O3), high and steady CH4 and CO2 conversions were obtained. However, the catalytic activity of the heterogeneous mixture of FY5 and Ni/Al2O3 was found to be better. Energy consumption values of the scale-up microwave-assisted CO2 reforming of CH4 reaction were estimated from the experimental data and a flow rate of 1 m3  h− 1 of introduced CH4 was used as calculation basis. An energy consumption of 44.4 kW·h per m3 of H2 produced, with FY5 as catalyst, and of 4.6 kW·h per m3 of H2 produced, with FY5 + Ni/Al2O3, was estimated. A comparison of these estimations with bibliographic values of energy consumption for steam methane reforming (1.2 kW·h per m3 of H2 produced), showed the microwave-assisted CO2 reforming of CH4 over mixtures of activated carbon and metal-based catalyst to be a promising process able to rival the steam reforming process.► Energy consumption of microwave-assisted CO2 reforming of CH4 was estimated. ► A lab-scale microwave pilot plant was used as the heating device. ► The activated carbon, FY5, and a mixture of FY5 and Ni/Al2O3 were used as catalysts. ► Energy consumption was 4.6 kW·h per m3 of H2 using FY5 + Ni/Al2O3 as catalyst. ► Microwave-assisted CO2 reforming of CH4 over FY5 + Ni/Al2O3 may be able to rival SMR.
Keywords: Dry reforming; Carbon-based catalysts; Microwave heating; Energy consumption;

In this study, using a power law approximation, the reaction orders of dolomite catalyzed transesterification of canola oil and methanol were evaluated. The reaction orders for triglyceride and methanol were determined as 1 and − 1.2 respectively, with a 0.9182 correlation coefficient. The rate constant was calculated as 3.9579 × 10− 3 (lt− 0.2/mol− 1.2). (gr.− 1 cat. min− 1) for this correlation. The reaction order of triglyceride which appeared in nominator of rate equation was considered as driving force of the reaction. The negative reaction order of methanol indicates the adsorption of methanol on the catalyst surface.► Using a power law approximation, the reaction orders were determined. ► Triglyceride concentration acts as driving force for the reaction. ► A good correlation was obtained between experimental and calculated rate values.
Keywords: Biodiesel; Canola oil; Transesterification; Kinetics; Dolomite;

A very simple preparation process was designed to successfully prepare monolithic Carbon Molecular Sieves (CMS) from very cheap precursors (an activated carbon (AC), obtained from a low rank coal, and coal tar pitch). This process consists of using a slurry of AC, coal tar pitch and toluene, which permits the monoliths to be moulded at room temperature. The AC/coal tar pitch ratio and the final pyrolysis temperature have been the main parameters analysed. The porosity blockage occurring during preparation of monoliths has been studied based on the results obtained by gas adsorption (i.e. N2 at − 196 °C and CO2 at 0 °C) and thermal analysis. An important aspect of this method is that a previous oxidation step of the binder is not necessary before the carbonisation of the monolith. The obtained results show that the proposed method is effective for the CMS preparation from the selected precursors. In this method, the use of coal tar pitch as binder is adequate since it plays a multiple role: (i) it confers an important mechanical stability to the monoliths and; (ii) it modifies the final porosity of the AC leading to the molecular sieving properties.► A very simple preparation process to prepare monolithic Carbon Molecular Sieves. ► Previous oxidation step is not necessary before the carbonization of the monolith. ► Coal tar pitch confers mechanical stability and modifies the porosity.
Keywords: Carbon molecular sieve; Pyrolytic deposition; Adsorption; Thermogravimetric analysis; Porosity;

A novel process for chipping unbarked tree stems into particles with defined sizes was tested in an industrial experiment conducted in a newly-constructed pellet plant. The factors varied were moisture content of the dried wood particles before pelleting (11–14%) and species composition (Norway spruce, Scots pine and birch; 0–100% of each species). On-line instruments were used to acquire near infrared (NIR) reflectance spectra from the stream of raw and dried particles. The response variables examined were pellet bulk density, mechanical durability, moisture content and ash content.The dryness of the wood particles had a significant effect on all responses (except for ash content). The species composition of the blend only affected mechanical durability and ash content. NIR-based models proved to be excellent for predicting particle dryness and useful for predicting the species composition. Optimal pellet quality was achieved using a blend with 45–75% spruce, 0–55% pine and for 0–25% birch at a moisture content of 12.5–14.0%.Overall, the results obtained demonstrate that it is possible to produce high quality pellets by using fresh stem logs in specified blends with specific moisture contents. NIR spectroscopy was found to be useful for the direct and indirect control of critical pellet quality variables.► Pellet of the highest quality class can be produced from of blends of whole-logs. ► Pellet quality is affected by moisture and proportion of species in the blends. ► Moisture content is a critical parameter for most quality parameters. ► Near-infrared (NIR) spectroscopy was shown very useful for on-line predictions. ► NIR technique is a powerful tool to control critical pellet quality parameters.
Keywords: Bioenergy; MLR; PLS regression; Multivariate calibration;

The nickel-impregnated rice straw (RS) was gasified in steam/argon flow to examine the influence of difference in chemical compositions on the hydrogen formation. The weight ratio of cellulose:hemicellulose:lignin is approximately 3:3:2. For the RS without nickel, the hydrogen began to be evolved from around 700 °C and the hydrogen evolution reached a maximum rate at 900 °C. By loading nickel catalyst, a new peak appeared at 700 °C in addition to the original peak at 900 °C. The hydrogen yields increased slightly with the amount of nickel. In order to change the chemical composition of rice straw significantly, the RS was treated hydrothermally at 220 °C for 5 min, resulting in the weight ratio of cellulose:hemicellulose:lignin being approximately 4:2:1. Hydrogen evolution profile of the hydrothermal residue of rice straw (RSR) without nickel was similar to that for the RS without nickel. By loading nickel, however, the hydrogen yields increased considerably. The difference in the behavior of hydrogen evolution between RS and RSR with nickel was discussed on the basis of the difference in their chemical compositions.► The nickel-impregnated rice straw, cellulose, and lignin were gasified in steam. ► All samples without nickel produced hydrogen from about 700 °C in gasification. ► By loading nickel, an additional hydrogen evolution peak appeared at 700 °C. ► The hydrogen yield from the hydrothermal-treated sample increased considerably.
Keywords: Rice straw; Nickel; Steam gasification; Hydrogen; Chemical composition; Hydrothermal treatment;

Study on preparation of Ca/Al/Fe3O4 magnetic composite solid catalyst and its application in biodiesel transesterification by Shaokun Tang; Liping Wang; Yi Zhang; Shufen Li; Songjiang Tian; Boyang Wang (84-89).
A magnetic composite solid catalyst was prepared by loading calcium aluminate onto Fe3O4 nanoparticles via a chemical synthesis method. The optimum conditions for the catalyst preparation were investigated. The influences of the molar ratio of Ca to Fe, calcining temperature, calcining time on the catalytic performance were studied. The catalyst with the highest activity was obtained when the molar ratio of Ca to Fe was 5:1; calcining temperature was 600 °C and calcining time was 6 h. The catalyst was characterized by thermogravimetric analyses (TGA), X-ray diffraction (XRD), scanning electronic microscope (SEM), Brunauer–Emmett–Teller method (BET) and vibrating sample magnetometer (VSM). Furthermore, the magnetic composite solid catalyst showed high catalytic activity for transesterification reaction for preparing biodiesel and the biodiesel yield reached 98.71% under the optimum conditions. The activity and recovery rate of this magnetic composite catalyst can be well maintained after 5 cycles of catalysis. This catalyst showed magnetism and can be easily separated magnetically. Both the catalytic activity and the recovery rate of the magnetic composite solid catalyst were much higher than those of pure calcium aluminate catalyst.► Preparation of Ca/Al/Fe3O4 magnetic catalyst via a chemical synthesis method. ► Smaller size and higher specific surface area of Ca/Al/Fe3O4 magnetic catalyst. ► Higher catalytic activity of Ca/Al/Fe3O4 catalyst for biodiesel transesterification. ► Higher recovery rate and easier recycle of Ca/Al/Fe3O4 magnetic catalyst.
Keywords: Magnetic; Fe3O4 nanoparticles; Solid base catalyst; Biodiesel; Transesterification;

A series of montmorillonites with adsorbed nickel ions was prepared through adsorption of nitrates from water solutions; there were four methods adopted. The surface of the sample under modification was investigated with the method of argon adsorption and XPS (X-ray photoelectron spectroscopy). SO2 was investigated on nickel-modified montmorillonites. Nickel cations were adsorbed on the montmorillonite surface as Ni2 + in Ni(OH)2 or NiO. Montmorillonite — after nickel adsorption — adsorbs SO2 physically. An addition of Mont–Ni to hard coal in a ratio 1:500 reduces SO2 emissions in the combustion process by 75–85%. Waste bentonite can be utilized for reducing SO2 emissions after processing.► Ni cations were adsorbed on the montmorillonite surface as Ni2 + in Ni(OH)2 or NiO. ► Montmorillonite — after nickel adsorption — adsorbs SO2 physically. ► Mont–Ni add to hard coal (1:500) decreased SO2 emissions in the combustion by 75–85%. ► Waste bentonite can be utilized for reducing SO2 emissions after processing.
Keywords: Montmorillonite; Adsorption; SO2; Combustion;

A CFD model for thermal conversion of thermally thick biomass particles by Ramin Mehrabian; Selma Zahirovic; Robert Scharler; Ingwald Obernberger; Stefan Kleditzsch; Siegmar Wirtz; Viktor Scherer; Hong Lu; Larry L. Baxter (96-108).
A one-dimensional model for the thermal conversion of thermally thick biomass particles is developed for the simulation of the fuel bed of biomass grate furnaces. The model can be applied for cylindrical and spherical particles. The particle is divided into four layers corresponding to the main stages of biomass thermal conversion. The energy and mass conservation equations are solved for each layer. The reactions are assigned to the boundaries. The model can predict the intra-particle temperature gradient, the particle mass loss rate as well as the time-dependent variations of particle size and density, as the most essential features of particle thermal conversion. When simulating the fuel bed of a biomass grate furnace, the particle model has to be numerically efficient. By reducing the number of variables and considering the lowest possible number of grid points inside the particle, a reasonable calculation time of less than 1 min for each particle is achieved. Comparisons between the results predicted by the model and by the measurements have been performed for different particle sizes, shapes and moisture contents during the pyrolysis and combustion in a single-particle reactor. The results of the model are in good agreement with experimental data which implies that the simplifications do not impair the model accuracy.
Keywords: Biomass; Thermal conversion; Thermally thick; Modelling; CFD;

Evaluation of the distribution of heavy metals and their chemical forms in ESP-fractions of fly ash by Ryszard Świetlik; Marzena Trojanowska; Małgorzata Anna Jóźwiak (109-118).
In this study we have examined the distribution of the chemical forms of Cd, Cu, Fe, Mn, Pb and Zn in the coal and coal + biomass fly ash (FA) collected in a three stage electrostatic precipitator (ESP) of a pulverized fuel fired boiler system. The concentrations of environmentally available volatile metals (Cd, Cu, Pb and Zn) increased towards finer grained ESP fractions, whereas the concentrations of hardly volatile metals (Fe and Mn) underwent a slight reduction. The concentration of Cd in all ESP fractions of FA was very low (< 1.5 mg/kg).We have proposed a new approach to determining the occurrence mode of trace metals in FAs by the modified Tessier scheme. A relatively uniform pattern of chemical fractionation was obtained for metals having various properties. The effect of co-combustion of biomass was observed for Cu and Mn distribution. Cu present in coal + biomass FA exhibits a clearly higher mobility than Cu in coal FA. The behavior of Mn is just the opposite and a difference in mobility is smaller. The characteristic feature of metal occurrence in the fly ash is a large share of the environmentally persistent fraction (40–90%) and a very low proportion of the water leaching fraction (< LOD). This has a large environmental significance, as it can be predicted that the pulverized coal combustion (PCC) FAs, even if found in extremely unfavorable environmental conditions, will not become an effective source of heavy metals.The sequential extraction results made it possible to propose an outline of the mechanism of formation of individual chemical fractions of the investigated metals.► Distribution of Cu, Fe, Mn, Pb and Zn in fly ash collected in multistage ESP of PCC. ► Chemical fractionation pattern of Cu, Fe, Mn, Pb and Zn in ESP fractions of fly ash. ► Role of co-combustion of biomass. ► New approach to evaluating of occurrence of chemical forms of trace metals in fly ash.
Keywords: Fly ash; Chemical fractionation; Sequential extraction; Trace metals; Electrostatic precipitator;

A series of solid base catalysts were synthesized by functionalization of different weight fractions (5, 10, and 15 wt.%) of 3-aminopropyltrimethoxysilane (APTMS) on thermally activated F- type fly ash (SiO2 and Al2O3  > 70%). Catalyst characterization was undertaken using different analytical techniques such as FTIR, XRD, SEM–EDX, TEM, N2 adsorption desorption, BET surface area analysis, TGA and AAS. The results showed that appropriate amount (10 wt.%) of aminopropyl groups results in excellent catalytic performance tested for condensation of ethyl cyanoacetate and cyclohexanone at 120 °C to produce Ethyl (cyclohexylidene) cyanoacetate (92% yield), an important intermediate of gabapentin (Neurontin), widely used in the treatment of epilepsy to relieve neuropathic pain, under solvent free conditions and in low cost route. The catalyst NH2FA-10 was reusable up to three reaction cycles. The work reports an innovative use of solid waste fly ash as an effective solid base catalyst.► A solid base catalyst (NH2FA-10) was synthesized from F-type fly ash. ► 3-Aminopropyltrimethoxysilane was functionalized over thermally activated fly ash. ► The catalyst was used for production of gabapentin through condensation. ► The catalyst was reusable up to 3 reaction cycles.
Keywords: Fly ash; Solid base catalyst; Knoevenagel condensation; Thermo-chemical activation;

Performance of entrained-flow coal gasifiers is in large part dictated by the burnout behavior of coal particles. In particular, the transition from porous, reactive char to molten, low reactive slag affects overall coal conversion. In this work, the physical phenomena associated with char–slag transition were studied for three coals using a laminar entrained-flow reactor under simulated gasification conditions. Partially oxidized particles with various conversions were prepared at temperatures above the ash fluid temperatures. The physical properties of the char and slag particles were characterized, including the particle density, size, internal surface area and morphology. Results show that at a coal-dependent critical conversion, the particles undergo remarkable physical changes, such as density increase, size reduction and surface area decrease. These phenomena indicate the char–slag transition.► Char-slag transition features changes in particle density, size and surface area. ► Density increases as particle size reduces in the burnout process. ► Size reduction is dominated by shrinkage and fragmentation. ► Surface area decreases due to pore blockage and loss of microporosity. ► Critical conversion of char-slag transition depends on parent coal ash content.
Keywords: Porous char; Molten slag; Ash particle; Entrained-flow reactor; Coal gasification;

A study into the processing of bitumen modified with tire crumb rubber and polymeric additives by V. González; F.J. Martínez-Boza; C. Gallegos; A. Pérez-Lepe; A. Páez (137-143).
This work focuses on the influence that processing variables (such as gap between rotor and stator of the mixer, time and temperature) exert on both mechanical properties and hot storage stability of bitumen modified with crumb tire rubber and polymeric additives, with the aim of optimizing the formulation of bitumen modified with low solubility materials.The experimental results obtained reveal that all the polymeric additives used yield an improvement in both the rheological and technological properties of the binder. Processing time leads to an increase in both the primary aging and rubber digestion, with the latter effect predominant for times of up to 2–3 h. Processing temperature increases the amount of rubber digestion and improves the elasticity of the resulting binder.► Optimized formulation of bitumen modified with low solubility materials is desired. ► Influence of processing conditions on thermomechanical properties is analyzed. ► Elasticity and rubber digestion are improves with temperature and time. ► Gap between rotor and stator hold little influence on the amount of rubber digestion. ► Increase in viscosity due to aging and decrease in mechanical properties above 200 °C.
Keywords: Crumb rubber; Bitumen;

Optimization of adsorptive desulfurization process of jet fuels for application in fuel cell systems by Y. Wang; J. Geder; J.M. Schubert; R. Dahl; J. Pasel; R. Peters (144-153).
In order to remove the sulfur compounds in jet fuels to produce ultra-clean fuels e.g., for fuel cell applications in aircraft (auxiliary power units, APUs), an integrated desulfurization process was developed, which combines a fixed-bed adsorption with a membrane separation. The present study focuses on the optimizing the fixed-bed adsorption with an Al2O3-based adsorbent. A sulfur level of 10 ppmw is required by the fuel cell system. 1 g of the adsorbent is capable of processing 7.43 ml of a 50% (vol.) light fraction of Jet A-1 with 440 ppmw under optimum operating conditions. The maximum sulfur adsorption capacity is approximately 2.51 mg S/g of adsorbent. The sulfur-loaded adsorbent can be regenerated by air rather than by hydrogen-containing gasses at an elevated temperature of 500 °C. However, the regenerated adsorbent only maintains a stable cyclic capacity of 2.01 mg S/g-ads over 70 adsorption–desorption cycles. In addition, the adsorbent bed dimensions with regard to bed length, bed diameter and particle size were optimized to obtain the desired sulfur adsorption capacity without encountering a significant pressure drop across the adsorption column.► Commercial fuels and fractions were desulfurized by adsorption. ► Operating conditions and reactor dimensions of sulfur adsorption was optimized. ► Sulfur capacity reaches 2.51 mg/g for treating a light Jet A-1 from 440 to 10 ppmw. ► Regenerated adsorbent maintains a stable capacity of 2.01 mg/g over 70 cycles.
Keywords: Desulfurization; Jet fuel; Adsorption; Fuel Cells;