Fuel Processing Technology (v.93, #1)

This study covers an investigation of three catalyst candidates namely; calcium carbonate (CaCO3), Perlite and potassium dichromate (K2Cr2O7) on pyrolysis of mixtures of hazelnut shell (HS) with ultra-high molecular weight polyethylene (UHMWPE) and polyethylene oxide (PEO) by measuring percentages of solid, liquid and gas products amounts gravimetrically. Pyrolysis processes were executed in a batch type tubular reactor at 500 and 650 °C for fifteen minutes. Catalysts have behaved differently on compounded mixtures. Especially the obtained liquid products from pyrolysis of mixtures shows smooth distribution compared to anomalous results of pure raw materials. The effect of catalysts on the pyrolysis of HS becomes more obvious in the presence of polymers which produces more gaseous product for K2Cr2O7 case. The other catalysts (CaCO3, Perlite) are more effective without addition of polymers which produce more liquid products. The ratio of HS should not be beyond the 0.5 for production of commercial materials and in their possible recycling process such as pyrolysis for acquisition of combustible liquids. These results may allow some clues for compounding of environmentally safe commercial materials, and easy and efficient recycling technologies.► Co-pyrolysis of biomass and plastics is really an eccentric study. ► It is also compulsory for sustainable development in environmental perspective. ► The diversity of biomass and plastic material, and their permutational probability of co-existence make the situation more troublesome and exciting. ► The retrieving of catalysts in pyrolysis should not only be concentrated on their chemical properties but also physical nature due to incompatible mixture character of plastics with biomass. ► The above considerations provided probable acquisition of valuable substances from these mixtures.
Keywords: Catalysts; Pyrolysis; Biomass; Polymer; Recycling;

Removal of mercury from coal-derived flue gas by injecting powdered sorbents often involves a substantial portion removed within an electrostatic precipitator (ESP). The present investigation uses a lab-scale ESP to assess the potential for injected sorbents to collect preferentially on discharge electrode wires. Such preferential collection would increase the adsorption capacity of the accumulated dust cake on the discharge electrodes, increasing their potential contribution to the total mercury removal performance of the ESP. The lab-scale results involving various fly ashes and both carbon-based and non-carbon mercury sorbents confirm that powdered activated carbon is enriched in the discharge electrode dust cake relative to its concentration in suspension in the gas flow. Other results explore the effects of applied ESP polarity, voltage, and power, percent PAC added to the fly ash, and total particulate matter loading entering the ESP on the collection behavior.
Keywords: Mercury; Electrostatic; Precipitation; Activated carbon; Ash;

Enhanced desulfurizing flotation of high sulfur coal by sonoelectrochemical method by Hong-Xi Zhang; Xiao-Yan Ma; Xian-Shu Dong; Zhi-Zhong Wang; Hong-Jin Bai (13-17).
Enhanced desulfurizing flotation of high sulfur coal was investigated using the sonoelectrochemical method. The supporting electrolyte used in this process was calcium hydroxide and the additive was anhydrous ethanol. The effects of treatment conditions on desulfurization were studied by a single-factor method. The conditions include anhydrous ethanol concentration, sonoelectrolytic time, current density, and ultrasound intensity. For the coal sample with a particle size of − 0.076 mm, the optimal experimental conditions achieved for anhydrous ethanol, sonoelectrolytic time, current density, and ultrasound intensity are 2.1 mol/L, 20 min, 15 × 10− 3  A/cm2, and 1.2 W/cm2, respectively. Optimal conditions cause a sulfur reduction of up to 75.4%. The raw and treated coals were analyzed by infrared spectroscopy and a chemical method. Pyritic sulfur, organic sulfur, and ash are partially removed. Compared with enhanced flotation by ultrasound or electrochemistry, desulfurizing flotation of high sulfur coal by sonoelectrochemistry is an effective technology.► Desulfurizing flotation of high sulfur coal by sonoelectrochemistry. ► The electrolyte was calcium hydroxide and the additlve was anhydrous ethanol. ► The rate of sulfur reduction reaches 75.4%. ► Pyritic sulfur, organic sulfur, and ash are partially removed. ► The combination of high sulfur reduction, high yield, and low sulfur content.
Keywords: Sonoelectrochemistry; Sonocavitation; Enhanced flotation; Desulfurization;

Oxidative desulfurization by chromium promoted sulfated zirconia by Sachin Kumar; Vimal Chandra Srivastava; R.P. Badoni (18-25).
Chromium promoted sulfated zirconia (CSZ), prepared by wetness impregnation technique, was characterized by various techniques like Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Electron probe microscopic analysis (EPMA). Bulk density and Brauner–Emmett–Teller (BET) surface area of CSZ were found to be 0.996 kg/m3 and 116.2 m2/g, respectively. CSZ was further used as catalyst for the oxidative removal of sulfur from model oil (dibenzothiophene, DBT, dissolved in iso-octane). Optimum CSZ dose was found to be 5 g/l. The catalytic oxidation of DBT by CSZ was found to be gradual process with optimum reaction time of 6 h. The activation energy for DBT conversion by CSZ was found to be 3.8 kJ/mol.► Preparation of Chromium promoted sulfated zirconia by wetness impregnation method. ► Characterization of catalyst by FTIR, XRD, EPMA and BET surface area. ► Oxidative removal of sulfur from model oil (dibenzothiophene dissolved in iso-octane). ► Optimization of parameters like catalyst dose, reaction time and temperature. ► Calculation of kinetic and thermodynamic parameters.
Keywords: Catalytic oxidation; Dibenzothiophene; Desulfurization; Kinetic study; Thermodynamics;

Process modeling for parametric study on oil palm empty fruit bunch steam gasification for hydrogen production by Abrar Inayat; Murni M. Ahmad; M.I. Abdul Mutalib; Suzana Yusup (26-34).
Biomass steam gasification with in-situ carbon dioxide capture using CaO exhibits good prospects for the production of hydrogen rich gas. The present work focuses on the process modeling for hydrogen production from oil palm empty fruit bunch (EFB) using MATLAB for parametric study. The model incorporates the reaction kinetics calculations of the steam gasification of EFB (C3.4H4.1O3.3) with in-situ CO2 capture, as well as mass and energy balances calculations. The developed model is used to investigate the effect of temperature and steam/biomass ratio on the hydrogen purity, yield and efficiency. Based on the results, hydrogen purity of more than 76.1 vol.% can be achieved. The maximum hydrogen yield predicted at the outlet of the gasifier is 102.6 g/kg of EFB. It is found that increment in temperature and steam/biomass ratio promotes hydrogen production. However, it is also predicted that the efficiency decreases when using more steam. Due to the still on-going empirical work, the results are compared with published literatures on different systems. The comparison shows that the results are in agreement to some extent due to the different basis.► Oil palm empty fruit bunch steam gasification with in-situ CO2 capture. ► Reaction kinetics modeling, mass and energy balances calculations using MATLAB. ► Study on effect of temperature and steam/biomass ratio for hydrogen production. ► Hydrogen purity is 76.1 vol% and yield is 102.6 g per kg of EFB. ► Hydrogen efficiency decreases by increasing steam/biomass ratio.
Keywords: Hydrogen; Steam gasification; CO2 capture; Empty fruit bunch; Process modeling;

Co-liquefaction of microalgae and synthetic polymer mixture in sub- and supercritical ethanol by Xiaokai Pei; Xingzhong Yuan; Guangming Zeng; Huajun Huang; Jingyu Wang; Hui Li; Huina Zhu (35-44).
Co-liquefaction of microalgae (Spirulina) and synthetic polymer (HDPE, high-density polyethylene) in sub- and supercritical ethanol was investigated in a stainless steel autoclave (1000 mL) at different reaction temperatures (T), Spirulina/HDPE ratio (R 1), (Spirulina  + HDPE)/ethanol ratio (R 2) and solvent filling ratio (R 3). Results showed that the addition of Spirulina to HDPE liquefaction could make the conversion conditions of HDPE milder. The yield of bio-oil obtained at 613 K with a 1/10 R 2 and a 2/10 R 3 was increased by 44.81 wt.% when the R 1 was raised from 0/10 to 4/6. Meanwhile, the synergetic effects (SE) between HDPE and Spirulina were increased from 0 to 30.39 wt.%. Further increasing R 1 resulted in a decrease in SE. The yields of bio-oil increased with increasing R 2 firstly and then declined. An opposite trend was observed for the yield of residue. The effect of R 3 to the yields of liquefaction products was similar to that of R 2. The content of C and H in bio-oils reduced with increasing R 1, while the content of O increased. The bio-oil from pure Spirulina liquefaction runs mainly consisted of oxygen-containing compounds, such as carboxylic acids, esters and ketones. But the major components of bio-oil from co-liquefaction of Spirulina and HDPE mixture were similar to those of pure HDPE-derived bio-oil, in which aliphatic hydrocarbons dominated.► Co-liquefaction characteristics of Spirulina and HDPE were investigated. ► The addition of Spirulina could make the conversion conditions of HDPE milder. ► Significant synergetic effects between Spirulina and HDPE increased bio-oil yield. ► The presence of HDPE also improved the quality of Spirulina-derived bio-oil. ► Adhesion between Spirulina and HDPE could impede the heat and mass transfer.
Keywords: Co-liquefaction; Microalgae; Synergetic polymer; Sub- and supercritical ethanol; Synergetic effect; Bio-oil;

The adsorption behavior of benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (DMDBT) from n-heptane was investigated onto activated carbon cloth (ACC) and its modified forms at 30 °C in batch condition. ACC was modified by HNO3, (NH4)2S2O8, H2SO4, HCl and NaOH at ambient temperature. The adsorbents were characterized using nitrogen adsorption/desorption. It was found that the adsorbents are mainly microporous but differ in their surface chemistry, which is related to the effect of oxidizing agent. The adsorption process was studied from both equilibrium and kinetics point of view. The equilibrium experimental data were fitted to the Langmuir, Freundlich and Langmuir–Freundlich by non-linear method. Among the tested adsorbents, the modified ACC with HNO3 (ACC-HNO3) had the highest capacity for adsorption of DBT. Kinetic characterization of the adsorption process indicated that the mixed-order and modified pseudo-n-order models can describe the kinetics of adsorption of thiophenic compounds onto ACCs. The ACC and ACC-HNO3 were used to test the removal efficiency of total sulfur contents (BT, DBT and DMDBT, 150 ppmw for each of them), too. The effect of shaking and ultrasound methods and also temperature and time on the regeneration of saturated ACC-HNO3 with DBT was studied.Display Omitted► Organosulfur compounds can be removed from fuel by carbon cloth. ► Modified carbon cloth with HNO3 has the highest adsorption capacity. ► Ultrasonic is an efficient method for regeneration of adsorbents.
Keywords: Adsorption; Activated carbon cloth; Desulfurization; Thiophenic compounds;

Numerical investigation of NO emissions from an entrained flow reactor under oxy-coal conditions by L. Álvarez; M. Gharebaghi; J.M. Jones; M. Pourkashanian; A. Williams; J. Riaza; C. Pevida; J.J. Pis; F. Rubiera (53-64).
The NO emissions of two anthracitic and three high volatile bituminous coals were experimentally and numerically studied under both air and oxy-fuel combustion conditions in an entrained flow reactor (EFR). Thermal decomposition experiments under N2 and CO2 atmospheres were carried out to determine the distribution of fuel-bound nitrogen between the volatile and char and the results compared with those obtained by means of the network pyrolysis model, FG-DVC (Functional Group-Depolymerisation Vaporisation Cross-linking). This code was also used as a pre-processing stage to predict the evolution of HCN and NH3 during devolatilisation of the coals. A Computational Fluid Dynamic (CFD) model was used to predict NO emissions under different O2/CO2 (21–35% O2) conditions in the EFR.Three different models were used. The first assumed that all of the fuel-bound nitrogen had been converted to HCN. The second assumed that all of the volatile nitrogen would evolve as HCN, and the char–N formed NO by an amount determined by a conversion factor. The third approach was similar to the second but it included NH3 as a precursor of NO as well. The NO emissions predicted with the third approach were in good agreement with the experimental results. A decrease in NO emissions was observed when N2 was replaced by CO2 for the same oxygen concentration for both the experimental and computed results. Higher NO emissions under O2/CO2 conditions were observed when the oxygen concentration was 30 or 35%.► Experimental and numerical study of NO formation in oxyfuel combustion was performed. ► Experimental study was made using an entrained flow reactor for five coals at 1273 K. ► NO formation was highly dependent on oxygen enrichment level in oxy cases. ► Oxygen concentration of > 30–35% showed an increase in NO formation in oxy cases. ► One of the numerical approaches for modelling NO formation showed the best agreement.
Keywords: Computational Fluid Dynamics; Oxy-fuel combustion; NO emissions;

A case study on suspended particles in a natural gas urban transmission and distribution network by Mehdi Azadi; Ali Mohebbi; Saeid Soltaninejad; Fabrizio Scala (65-72).
Suspended particles in the natural gas transmission and distribution network of the city of Kerman, Iran were investigated. Particle concentration and size distribution were measured in different locations of the natural gas pipeline network. Particle samplings were carried out in two seasons: summer, when there is the lowest consumption, and winter, when there is the highest consumption of natural gas. Additional particle characterization was carried out by scanning electron microscopy coupled with energy dispersion X-ray (SEM/EDX) and X-ray diffraction(XRD) analyses. Particle concentration was found to be significantly higher in winter as compared to summer. The range of particle concentrations in summer was from 0.12 mg/Nm3 at the end of the pipeline to 4.7 mg/Nm3 at the network entrance, and from 0.30 mg/Nm3 to 22.1 mg/Nm3 in winter. Particle size distribution showed a higher frequency of smaller particles in winter than in summer. Larger particles were more likely to exist at the network entrance as compared to the exit. The average particle size ranged from 181 μm at the network end to 253 μm at the entrance in summer, and from 74 μm to 209 μm in winter. Particle characterization confirmed the presence of corrosion products in the suspended particles.
Keywords: Suspended particles; Natural gas; Kerman; Pipeline; Transmission; Distribution;

Ultrasound cavitation technique for up-gradation of vacuum residue by Priyanka Kaushik; Ajay Kumar; T. Bhaskar; Y.K. Sharma; Deepak Tandon; H.B. Goyal (73-77).
Generally, upgradation of the petroleum residue to valuable product is done through the catalytic and thermal cracking using very high temperature and pressure. The ultrasound assisted cavitation is the novel technique to intensify the cracking of asphaltene present in the vacuum residual feedstock.The up-gradation of residue was carried out with application of low frequency (24 kHz), high intensity ultrasound under atmospheric pressure and ambient temperature in a batch reactor.In the present work, vacuum residue, having high viscosity was subjected to acoustic cavitation for different reaction times (15 min to 90 min) and with different probe diameters at ambient temperature and pressure. The effect of ultrasound on the upgradation of residue (asphaltene degradation) has been studied with surfactant as emulsifier as well as without surfactant. Also, the effect of acoustic cavitation has been studied on the physico-chemical properties of residue.The study revealed that the asphaltene content of the vacuum residue decreased from 13.5 (initial asphaltene present in residue) to 7% (wt.%). It has been also observed that the physico-chemical properties of residue reduced with the influence of ultrasound energy.
Keywords: Vacuum residue; Asphaltene; Cracking; Cavitation; Ultrasound; Surfactant;

CO preferential oxidation over Au/MnOx–CeO2 catalysts prepared with ultrasonic assistance: Effect of calcination temperature by Yunbao Tu; Ming Meng; Zhaosong Sun; Lijie Zhang; Tong Ding; Tianyong Zhang (78-84).
The Au/MnOx–CeO2 catalysts used for CO preferential oxidation were prepared by deposition–precipitation with ultrasonic assistance. The effect of calcination temperature (150–350 °C) on the structures and catalytic performance of the catalysts was systematically investigated. It is found that the catalyst Au/MnOx–CeO2 calcined at 250 °C exhibits the best catalytic performance, giving not only the highest CO conversion of 90.9% but also the highest selectivity of oxygen to CO2 at 120 °C. The results of XRD, TEM and XPS indicate that this catalyst possesses the smallest particle size, the highest dispersion of Au species and the largest amount of surface adsorbed oxygen species, which are favorable to CO oxidation. The H2-TPR results reveal that the selectivity of oxygen to CO2 is mainly determined by the reducibility of Au species in the catalysts. The strong interaction between Au species and the support in Au/MnOx–CeO2-250 decreases its capability for H2 dissociation and oxidation, leading to high selectivity of oxygen to CO2.Display Omitted► Au/MnOx–CeO2 catalysts are prepared by a novel ultrasonic-assisted DP method. ► The sample Au/MnOx–CeO2 calcined at 250 °C shows the highest CO PROX performance. ► The selectivity of O2 to CO2 is mainly determined by the reducibility of Au species. ► Ultrasonic increases Au-support interaction, inhibiting H2 activation and oxidation.
Keywords: Gold catalysts; CO preferential oxidation; Ceria; Manganese oxide; Calcination temperature;

Extraction of dibenzothiophene from dodecane using ionic liquids by Cecilia Devi Wilfred; Chong Fai Kiat; Zakaria Man; M. Azmi Bustam; M. Ibrahim M. Mutalib; Chan Zhe Phak (85-89).
The effect of ionic liquid loading, extraction temperature, and extraction time in the removal of dibenzothiophene from dodecane were investigated. Eighteen (18) ionic liquids were screened for its dibenzothiophene extraction ability. Imidazolium based ionic liquids with thiocyanate, dicyanamide and octylsulfate anions exhibited the highest extraction capabilities with 66.1%, 66.1%, and 63.6% of extraction efficiency respectively. Tributylmethylammonium methylcarbonate ionic liquid gave 61.9% extraction efficiency, which showed that π–π interaction between aromatic rings of sulfur compound and ionic liquid (IL) was not be the main extraction mechanism. A trend between specific volume and desulfurization efficiency of ILs was put forward, enabling researchers to predict ILs' desulfurization efficiency from its specific volume. It was also found that [C4mim][SCN] can be reused in extraction without regeneration with considerable extraction efficiency of 41.9%. Huge saving on energy can be achieved if we make use of this IL behavior in process design, instead of regenerating IL after every time of extraction.
Keywords: Desulfurization; Ionic liquids; Extraction; Dibenzothiophene;

Cobalt-based catalysts were prepared by precipitation method. This research investigated the effects of different supports cobalt loading, promoters, loading of promoters and calcination conditions on the catalytic performance of cobalt catalysts for Fisher–Tropsch synthesis (FTS). It was found that the catalyst containing 40 wt.% Co/TiO2 promoted with 6 wt.% Zn was an optimal catalyst for the conversion of synthesis gas to hydrocarbons especially light olefins. The activity and selectivity of optimal catalyst were studied in different operational conditions. The results showed that the best operational conditions were the H2/CO = 2/1 molar feed ratio at 240 °C and GHSV = 1100 h−1 under atmospheric pressure. Characterization of catalysts were carried out by using X-ray diffraction (XRD), thermal gravimetric analysis (TGA), hydrogen temperature program reduction (H2-TPR), N2 physisorption measurements such as Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) methods.The catalyst containing 40 wt.% Co/TiO2 was promoted with 6 wt.% Zn were studied for light olefins production. The effects of preparation variable conditions and different supports with loading of the optimum support were investigated.Display Omitted► We examine Co/TiO2 catalyst promoted with 6 wt.% Zn for light olefins production. ► This catalyst is superior catalyst for C2–C4 olefins. ► The reaction conditions were found 240 °C, 1 bar, H2/CO=2/1 and GHSV=1100 h−1. ► Methane selectivity decreased from 16.6 to 9.3% by using this catalyst.
Keywords: Support; Promoter; Light olefins; Operational condition;

Optimisation of the melt-spinning of anthracene oil-based pitch for isotropic carbon fibre preparation by Noel Díez; Patricia Álvarez; Ricardo Santamaría; Clara Blanco; Rosa Menéndez; Marcos Granda (99-104).
This paper demonstrates the suitability of a new environmentally friendly pitch, obtained from anthracene oil, for the preparation of isotropic carbon fibres. The pitch exhibits an adequate thermal behaviour and it is free of solid particles. Green carbon fibres were prepared by means of a melt-spinning process with no filtering step, and subsequent stabilisation and carbonisation. For the optimisation of the melt-spinning process, the influence of the spinning temperature, extrusion pressure, spinneret hole size, winding speed and the interrelationship of these factors upon the microstructure and diameter of the fibres was studied. High winding speeds (250 cm s−1), in combination with a large spinneret hole size (500 μm) and low extrusion pressures (1 bar), led to high quality isotropic carbon fibres with diameters as low as ~ 15 μm and a tensile strength of > 1100 MPa which fulfil the requirements for their application as standard isotropic carbon fibres.► We prepare isotropic carbon fibres by melt spinning a new anthracene oil based pitch. ► The pitch was spun at a temperature of 30°C above its softening point. ► Effects of winding speed, nitrogen pressure and spinneret hole size were studied. ► Carbon fibres of diameter 15 mm were obtained after stabilization and carbonization.
Keywords: Anthracene oil; Isotropic pitch; Carbon fibre; Melt-spinning;

Supported nickel catalysts with a core/shell structure of Ni/Al2O3 and Ni/MgO–Al2O3 synthesized under multi-bubble sonoluminescence (MBSL) conditions were tested for mixed steam and dry (CO2) reforming and autothermal reforming of methane. In the previous tests, the supported Ni catalysts made of 10% Ni loading on Al2O3 or MgO–Al2O3 had shown good performances in the steam reforming of methane (methane conversion of 97% at 750 °C), in the partial oxidation of methane (methane conversion of 96% at 800 °C) and in dry reforming of methane (methane conversion of 96% at 850 °C) and showed high thermal stability for the first 50–150 h. In this study, the supported Ni catalysts showed good performance in the mixed and autothermal reforming of methane with their excellent thermal stability for the first 50 h. In addition, very interestingly, there was no appreciable carbon deposition on the surface of the tested catalysts after the reforming reaction.
Keywords: Mixed steam and dry reforming; Autothermal reforming; Supported Ni catalysts; Core/shell structure;