Fuel Processing Technology (v.120, #C)

Doping with Ti in the BaFeO3 − x perovskite resulted in the significantly improved NOx adsorbability and the sulfur resistance, as compared with the BaFeO3 − x. The Ti loading and residual carbonate could enhance the NOx storage capacity of these catalysts. However, during the sulfation, the sulfates were readily formed over the undissolved titanium oxides and the carbonates on perovskite. The complete Ti-doping in perovskite would reduce the amount of the residual carbonate, as well as the undissolved titanium, consequently leading to the relatively smaller NOx storage capacity (NSC) but the further improved sulfur resistance. Among these Ti incorporated perovskites, the BaFe0.8Ti0.2O3 − y perovskite prepared by the impregnation method had the most complete Ti-doping degree and the highest sulfur resistance: only 5.1% of the NSC dropped (from 1000 to 949 μmol g  −1) after the sulfation pretreatment at 400 °C. It is a possible NOx trapping material with the advantages of the high NOx storage capacity and sulfur tolerance for lean-burn exhausts.
Keywords: Ti-doping; Perovskite; Lean-burn; NOx storage; Sulfur resistance;

Structural characterization of the thermal extracts of lignite by Zhicai Wang; Hengfu Shui; Chunxiu Pan; Liang Li; Shibiao Ren; Zhiping Lei; Shigang Kang; Cheng Wei; Jingchen Hu (8-15).
Thermal extraction (TE) with nonspecific solvent at high temperature is a potential technology to separate organic materials from coal, especially low-rank coal such as lignite. In this paper, thermal extract (TES) of Xianfeng lignite (XL) in toluene/methanol (3:1, volume) mixed solvent at 300 °C was separated into different sub-fractions by the method of column chromatography combined with Soxhlet extraction in tetrahydrofuran (THF). These sub-fractions were characterized by element analysis, FTIR, 1H NMR and GC/MS. 78 compounds including C12–30 higher aliphatic hydrocarbons (HAHs), aromatic hydrocarbons (AHs), C17–27 fatty acid methyl esters (FAMEs) and other heteroatomic compounds were identified from the TES. As two groups of predominant components, HAHs and FAMEs are the intrinsic components in XL except for small amount of FAMEs produced by esterification and transesterification reactions in the TE process. Further, the mechanism of TE was also speculated by the characterization results of TES. As a result, the TE with nonspecific solvent at high temperature can not only improve the extract yield of organic materials, but also obtain chemicals such as HAHs and FAMEs from lignite.
Keywords: Xianfeng lignite; Thermal extraction; Nonspecific solvent; Extract characterization;

Study on the formation, determination, and removal of elemental sulfur in ultra-low sulfur gas oil by Changlong Yin; He Li; Huan Liu; Leiyan Zhao; Zhenjiang Bai; Yaping Wang; Shaoping Zhang; Chenguang Liu (16-21).
The question as to the formation of elemental sulfur in petroleum has never been definitely settled, although there are many references in the literature to the presence of elemental sulfur in distillates. In connection with studies on sulfur compounds in petroleum distillates, the presence and behavior of elemental sulfur in gas oil, especially in ultra-low sulfur gas oil are important. A rapid and accurate method for the analysis of elemental sulfur by GC–PFPD was developed and a series of experiments was carried out to clarify the formation mechanism of elemental sulfur. The results showed that (NH4)2Sn was found to be easily oxidized to free sulfur when contacted with air and the oxidation of ammonium polysulfide was the main formation mechanism of elemental sulfur in the hydrotreating of gas oil. It was revealed that nitrogen-containing molecules in the oil feed and NH4 + contained in the HDS catalyst can result in the formation of (NH4)2Sn. A method with high efficiency and selectivity to remove elemental sulfur from hydrotreated gas oil by Na2S washing was developed for analysis purpose.
Keywords: Ultra-low sulfur diesel; Elemental sulfur; Formation mechanism; Removal;

This paper presents an experimental and numerical study on co-firing olive waste (0, 10%, 20% on mass basis) with two coals in an entrained flow reactor under three oxy-fuel conditions (21%O2/79%CO2, 30%O2/70%CO2 and 35%O2/65%CO2) and air–fuel condition. Co-firing biomass with coal was found to have favourable synergy effects in all the cases: it significantly improves the burnout and remarkably lowers NOx emissions. The reduced peak temperatures during co-firing can also help to mitigate deposition formation in real furnaces. Co-firing CO2-neutral biomass with coals under oxy-fuel conditions can achieve a below-zero CO2 emission if the released CO2 is captured and sequestered. The model-predicted burnout and gaseous emissions were compared against the experimental results. A very good agreement was observed, the differences in a range of ± 5–10% of the experimental values, which indicates the model can be used to aid in design and optimization of large-scale biomass co-firing under oxy-fuel conditions.
Keywords: Biomass co-firing; Synergy effects; CO2 capture; Oxy-fuel combustion; Below-zero CO2 emissions; CFD;

Sodium zirconate (Na2ZrO3) as a catalyst in a soybean oil transesterification reaction for biodiesel production by Nicolás Santiago-Torres; Issis C. Romero-Ibarra; Heriberto Pfeiffer (34-39).
Sodium zirconate (Na2ZrO3) was tested as a basic catalyst for the production of biodiesel using a soybean oil transesterification reaction. Initially, Na2ZrO3 was synthesized via a solid-state reaction. The structure and microstructure of the catalyst were characterized using X-ray diffraction, scanning electron microscopy and N2 adsorption. Various transesterification reactions were then conducted using soybean oil and methanol under differing reaction conditions. The influence of some parameters, such as the reactant concentrations (molar ratios), catalyst percentage, reaction time, temperature and re-use of the catalyst, on the transesterification process in the presence of Na2ZrO3 was investigated. The maximum FAME conversion efficiency was 98.3% at 3 h of reaction time and 3% of catalyst. Additionally, the produced biodiesel was characterized using infrared spectroscopy, gas chromatography coupled to mass spectrometry and proton nuclear magnetic resonance. The resulting biodiesel showed good purity, composition and degree of unsaturation in comparison to previous reports. According to these results, Na2ZrO3 could become an alternative solid base catalyst for scalable and cost-effective biodiesel production.Display Omitted
Keywords: Basic catalyst; Biodiesel; Sodium zirconate; Soybean oil;

Lactic acid production from glycerol using CaO as solid base catalyst by Lu Chen; Shoujie Ren; X. Philip Ye (40-47).
In the valorization of glycerol as byproduct of biodiesel production, although recent progress in glycerol conversion to lactic acid using homogeneous chemocatalysis showed promising high yield, the used high alkalinity entails high corrosiveness to reactors and problematic downstream separations. In this study, five solid base catalysts were screened for converting glycerol to lactic acid with the aim to ease corrosiveness, focusing on inexpensive CaO as a promising solid base. Process conditions were systematically investigated for optimization. The highest yield of lactic acid achieved was 40.8 mol% with a glycerol conversion of 97.8 mol% at the optimum conditions using refined glycerol. Similar conversion rate and lactic acid yield were also obtained in the conversion of crude glycerol using CaO if the water content in crude glycerol is lower than 10%. CaO exhibited lower activation energy in converting glycerol to lactic acid compared to homogeneous NaOH catalyst. Corrosiveness to reactor using CaO was proven much lower than that using homogeneous NaOH catalyst. CaO as catalyst for both biodiesel production and subsequent crude glycerol conversion to lactic acid was investigated, revealing its potential industrial applications for the production of both biodiesel and lactic acid.Display Omitted
Keywords: Biodiesel; Glycerol; Calcium oxide; Lactic acid; Corrosiveness; Solid base catalysts;

In this study, we identified suitable potassium amino acid salt absorbents for CO2 removal for purposes of recovering CH4 from coal bed methane (CBM). We checked critical concentrations of each blended solvent that did not produce any precipitate during CO2 absorption. From among these, we selected 8 solvents that gave no precipitate. The selected absorbents were assessed in terms of their CO2 loading capacity and absorption/desorption rate in comparison with monoethanolamine (MEA) through a screening test. We regulated a 10% CO2 balance in CH4, because the feed gas was assumed to approximate the CBM. From the results obtained, it seems that 4 M SAR, 1.5 M ALA + 1 M PZ, and 1.5 M SER + 1 M PZ are good CO2 absorbents, because their cyclic CO2 loading (0.223, 0.208, and 0.18 mol, respectively, of CO2/mol of absorbent) is higher than those of other selected solvents (e.g., 4 M GLY + 1 M PZ, which has the lowest cyclic CO2 loading). In addition, we checked that the high concentration of amino acid salts interrupted CO2 absorption, decreasing the solubility. These solvents also have a relatively high surface tension at 25 °C (70.6; 73.3; 68.6 mN/m), when compared with pure water it (72.0 mN/m). We therefore conclude that the suggested absorbent is adequate for use in the CO2 removal process.
Keywords: CO2 absorption; Potassium amino salts; CH4 recovery; Coalbed methane;

Trace metals emission in syngas from biomass gasification by Deepak Pudasainee; Hanns-Rudolf Paur; Sabine Fleck; Helmut Seifert (54-60).
In this paper, trace metals (As, Be, Cd, Cr, Hg Ni, Pb, Se and V) emission from the atmospheric entrained flow gasifier REGA at Karlsruhe Institute of Technology, Germany is presented. Elemental composition and metals concentration in glycol (model fuel) and straw char samples were determined. In order to achieve well defined and reproducible operating conditions, gasification experiments were carried out with glycol and slurry (straw char mixed with glycol) as fuel. Trace metals emission and distribution into particle and gas phase in syngas from gasification were measured according to US EPA method 29. During glycol gasification, metals concentration in syngas ranged from 0.1 μg/Nm3 (V) to 4.6 μg/Nm3 (Cr). In slurry gasification, metals concentration in syngas ranged from 2.4 μg/Nm3 (Hg) to 53.2 μg/Nm3 (Ni). Trace metals tend to volatilize more in reducing gasification environment. Tendency of metals to speciate into particle phase increased in slurry gasification than glycol gasification due to increased in particle concentration and unburned carbon content in syngas. The increase of particle and carbon content in syngas possessed strong influence in distribution behavior of As, Be and Pb, however, such influence was less for other metals studied. Mercury in syngas was speciated predominantly into elemental form followed by oxidized form whereas share of particle bond mercury was the least.
Keywords: Biomass gasification; Mercury; Minamata convention; Renewable energy; Syngas; Trace metals;

Flotation process design based on energy input and distribution by Xiahui Gui; Jiongtian Liu; Yijun Cao; Gan Cheng; Shulei Li; Lun Wu (61-70).
Energy-saving ability and high flotation efficiency are two important factors in the flotation process. In this investigation, a new concept for the flotation process design based on energy input and distribution was proposed, low energy was inputted early to recover easy-to-float materials, whereas high energy was inputted late to recover difficult-to-float materials. The flotation tests were conducted in an XFD 0.75 L laboratory-scale flotation machine. A comparison of flotation performance using constant power input and gradually increased power input was investigated. The flotation results indicated that low ash content, high flotation efficiency index, and energy-saving ability could be obtained by increasing power input step by step in the flotation process. The flotation process design based on different shaft speeds (1500, 1500, 1800, 1800, and 2400 r/min in different flotation periods) and an energy consumption of 1720.8 J is suitable for flotation performance of the coal samples in this study.
Keywords: Coal flotation; Flotation design; Energy consumption; Energy input; Flotation process;

Hydration-induced reactivation of spent sorbents for fluidized bed calcium looping (double looping) by Antonio Coppola; Piero Salatino; Fabio Montagnaro; Fabrizio Scala (71-78).
The aim of this work was to study the hydration-induced reactivation of spent sorbents from a calcium looping process. The changes of the sorbent properties induced by hydration, the regeneration of the CO2 capture capacity and the attrition tendency of the material once reused in the looping cycle were investigated. To this end, a reference limestone was subjected to multiple calcination/carbonation cycles in a lab-scale fluidized bed reactor and then reactivated by water hydration at room temperature for different times. Results suggested that the sorbent under investigation should be hydrated for times as short as possible compatible with complete chemical hydration. In fact, long hydration times bring about cramming (chemical sintering) phenomena, lower enhancement in the active porosity, increased attrition tendency and reduced reactivation. Attrition/fragmentation data referring to as-received and reactivated sorbents were compared. Relationships among CO2 capture capacity, surface properties and attrition tendency were presented and critically discussed, taking into account also the results obtained for a different sorbent.
Keywords: Calcium looping; Fluidized bed; Water reactivation; CO2 capture; Attrition/fragmentation;

Production and characterization of biodiesel from algae by Piyushi Nautiyal; K.A. Subramanian; M.G. Dastidar (79-88).
The feasibility of biodiesel production from microalgae as third generation biodiesel feedstock was studied in the present investigation. The studies were conducted to evaluate the growth patterns of the algae species i.e. Spirulina, Chlorella and pond water algae. The oil was extracted from the algae biomass and then transesterified. Simultaneous extraction and transesterification were also studied using different solvents. Maximum biodiesel yield was obtained using simultaneous extraction and transesterification using hexane as a solvent. The systematic characterization of algae biomass, algae oil and algae biodiesel was carried out to establish the potential of microalgae for biodiesel production.
Keywords: Microalgae; Spirulina; Chlorella; Pond water algae; Transesterification; Biodiesel;

Pyrolysis of polyunsaturated fatty acids by Justice Asomaning; Paolo Mussone; David C. Bressler (89-95).
The primary goal of this work was to study the thermal conversion of polyunsaturated fatty acids to hydrocarbon for use as renewable chemicals and fuels. Linoleic acid (cis,cis-9,12-octadecedienoic acid) was selected as a model polyunsaturated fatty acid. Batch pyrolysis reactions were conducted at temperatures from 350 to 450 °C for 0.5 to 8 h reaction times. Gas chromatography and mass spectrometry were used to analyze and identify products in the gas and liquid product fractions. Analysis of the gas phase showed concurrent production of CO and CO2, indicating that deoxygenation reaction proceeded through both decarbonylation and decarboxylation mechanisms. The gas product encompassed alkanes and alkenes with carbon numbers ranging C1–C5 with ethane and propane as the major products. Analysis of the liquid fraction revealed series of n-alkanes, alkenes, cyclic alkanes and alkenes, and fatty acids. The presence of the unsaturation resulted in cracking at the allylic C―C and predominance of C6 to C10 hydrocarbons and C9 and C10 fatty acids. This work uncovers the dominant reaction pathways in the pyrolysis of free polyunsaturated fatty acids and demonstrates the viability of this pyrolysis to produce renewable hydrocarbons immediately compatible with the existing petrochemical infrastructure.
Keywords: Linoleic acid; Pyrolysis; Double bond; Deoxygenation; Thermal cracking; Renewable hydrocarbons;

This article has been retracted at the request of the Editor-in-Chief.Moreover this article contains incorrect factual statements about the Midrex process. There are also numerous instances in the paper where model results are inconsistent with the results from practical operation. As a result, the integrity of the paper and its results have been brought into question. Whist the authors have provided responses to the concerns raised, the explanations provided have not been found satisfactory by the editors.We regret that these problems were not detected before the article was accepted for publication in the journal.

Steam co-gasification of brown seaweed and land-based biomass by Malinee Kaewpanha; Guoqing Guan; Xiaogang Hao; Zhongde Wang; Yutaka Kasai; Katsuki Kusakabe; Abuliti Abudula (106-112).
Alkali and alkaline earth species in biomass have self-catalytic activity on the steam gasification to produce hydrogen-rich gas. In this study, three types of biomass, i.e., brown seaweed, Japanese cedar, apple branch containing different concentrations of alkali and alkaline earth species, and the mix of both of them were gasified with steam in a fixed-bed reactor under atmospheric pressure. The effects of reaction temperature, steam amount and mixing ratio in co-gasification on gas production yields were investigated. The results showed that higher gas production yields (especially for H2 and CO2) were obtained when the brown seaweed was used than the other two types of biomass since the ash content in brown seaweed was much higher than in land-based biomass and contained a large amount of alkali and alkaline earth species. The yield of hydrogen increased with an increase in the amount of steam, but excessive steam use reduced the hydrogen production yield. From the co-gasification experiments, the gas production yields (especially for H2 and CO2) from the land-based biomass increased with the increase in brown seaweed ratio, suggesting that the alkali and alkaline earth species in brown seaweed acted as the catalysts to enhance the gasification of land-based biomass in co-gasification process.Display Omitted
Keywords: Biomass; Steam gasification; Co-gasification; Seaweed; Alkali metals; Alkaline earth metals;

Palladium–Tin nanocatalysts in high concentration acetylene hydrogenation: A novel deactivation mechanism by Elaheh Esmaeili; Ali Morad Rashidi; Abbas Ali Khodadadi; Yadollah Mortazavi; Mehdi Rashidzadeh (113-122).
In the present study, tin-promoted Pd/MWNTs nanocatalysts were prepared via polyol method for further application in highly concentrated acetylene hydrogenation. Particle sizes decreased drastically with addition of tin, indicating a narrow particle size distribution. The particle sizes and the associated distribution remained constant, even after aging the nanocatalyst upon the reaction for a long time. Addition of tin to Pd catalysts showed good propensity towards the highly-stabilized catalysts, in particular, at the molar ratios of Sn/Pd more than 0.25 up to 1. To characterize the catalysts examined, TEM, XRD, TPR, XPS, SIM DIS, FTIR and TPO were applied. XPS and XRD experiments confirmed the formation of intermetallic compounds and Pd2Sn alloy, respectively. The results showed that the presence of these structures on the catalyst surfaces were responsible for the higher catalytic performance, especially, for the catalysts with higher molar ratios of Sn/Pd. Also, a novel mechanism was proposed based on which the higher values of Sn/Pd were more unaffected in contrast to deactivation. This was attributed to the lower ability of the catalyst to dehydrogenate carbonaceous species, which in turn, decreased the spillovers of carbonaceous species from the catalyst surface to the support, increasing the life time of the catalyst.Display Omitted
Keywords: High-concentrated acetylene; Tin-promoted catalyst; Deactivation; Isolated adsorption site; Green oil; Intermetallic;

Effectiveness of catechin and poly(ethylene glycol) at inhibiting the spontaneous combustion of coal by Guolan Dou; Deming Wang; Xiaoxing Zhong; Botao Qin (123-127).
The effects of various combinations of catechin and poly(ethylene glycol) (PEG) concentrations on the inhibition of coal oxidation were studied. The oxidation behaviors of coal samples both with and without the additives were examined, based on measurements of cross point temperature, oxygen consumption during low temperature oxidation and carbon monoxide emission rates. The results demonstrate that an additive consisting of a combination of both catechin and PEG 200 is capable of inhibiting the oxidation process. In situ monitoring of the surfaces of coal samples during oxidation also indicated that these additives suppress coal oxidation by accelerating the formation of ether bonds. Accordingly, a suppression mechanism is proposed.
Keywords: Coal oxidation; Catechin; Polyethylene glycol (PEG); In situ FTIR; Suppress; Reaction mechanism;

Silicate rock dissolution by ammonium bisulphate for pH swing mineral CO2 sequestration by Aimaro Sanna; Alicja Lacinska; Mike Styles; M. Mercedes Maroto-Valer (128-135).
A wide range of mineral resources and different technical approaches can be employed to permanently sequester the CO2 into stable carbonates through mineral carbonation. The aim of this work was to investigate the dissolution and carbonation of olivine, pyroxene and amphibole-rich rocks using an ammonium salt pH swing mineral carbonation process. The effect of temperature (50, 70 and 100 °C) and time (5, 10, 15, 30, 60, 120, 180 min) and the dissolution kinetics were studied using a batch reactor at ambient pressure. Temperature had a direct effect on the rates of mineral dissolution reactions. The higher dissolution efficiency using olivine with particles 75–150 μm was 77% in 3 h at 100 °C, with a limitation due to product layer diffusion with apparent activation energy of 31 kJ mol− 1. The final CO2 sequestration efficiency using olivine was 70 wt.%. Besides, only about 30% of Mg was extracted from pyroxene and amphibole at 100 °C due to polymerisation of non-dissolved silica and deposition of sulphate minerals on their surface. Therefore, amphibole and pyroxene-rich rocks do not represent a resource for this process. Ammonia-based mineral carbonation could integrate geological storage where the last is not feasible and where CO2 emitters and olivine resources are closely co-located.
Keywords: Mineral carbonation; Carbon capture and storage; Dissolution models; Olivine;