Fuel Processing Technology (v.135, #C)
Editorial Board (IFC).
Preface by Wen-Ying Li; Ke-Chang Xie; Chun-Zhu Li (1).
Solid phosphoric acid catalyst for propene oligomerization: Effect of silicon phosphate composition by Jichang Zhang; Yaru Yan; Qi Chu; Jie Feng (2-5).
Solid phosphoric acid catalysts have been industrially used for propene oligomerization to improve the gasoline quality. However, solid phosphoric acid catalysts will lose their mechanical strength in the presence of water which is used to hydrolyze silicon phosphates to produce free phosphoric acids for maintaining the catalytic activity. In this case, to harmonize the catalyst lifetime and activity of solid phosphoric acid catalysts, the properties of silicon phosphate were investigated to achieve the maximum catalytic performance. A solid phosphoric acid catalyst was prepared with kieselguhr and concentrated phosphoric acid. Trace water was used to promote the release of active components from silicon phosphates during the reaction. Free phosphoric acid content, as a vital property of a solid phosphoric acid catalyst, was measured by ammonia temperature-programmed desorption. The crystal phase composition of silicon phosphates in a solid phosphoric acid catalyst was analyzed by X-ray diffraction. The catalytic performance was evaluated in a fixed bed under the conditions of 210 °C and 4 MPa. A solid phosphoric acid catalyst with relative content of 51% Si5O(PO4)6 and 49% SiP2O7 showed the best performance in improving catalytic activity and lifetime, and the conversion of propene was above 99% for nearly 70 h.Display Omitted
Keywords: Solid phosphoric acid catalyst; Silicon phosphate composition; Water; Propene oligomerization;
Efficient photocatalytic reduction of CO2 into liquid products over cerium doped titania nanoparticles synthesized by a sol–gel auto-ignited method by Zhuo Xiong; Yongchun Zhao; Junying Zhang; Chuguang Zheng (6-13).
Cerium doped TiO2 nanoparticles were synthesized through a simple sol–gel auto-ignited method. Ce doping inhibited the growth of TiO2 particles and increased the surface area of the catalysts. The catalyst was well characterized and used as photocatalysts to convert CO2 and H2O into hydrocarbons, including CH3OH, HCHO, and CH4, in liquid phase. CH3OH was found to be the primary product with a highest yield of 188 μmol/g obtained by 1% Ce doped TiO2 catalyst after UV irradiation for 8 h, which was much higher than that of pure TiO2 and P25. The selective formation of CH3OH can be ascribed to the compromise between charge transfer and thermodynamics. The introduction of CeO2 can enhance the chemisorbed oxygen on the surface of the catalyst and the existence of Ce3 +/Ce4 + mixture can effectively inhibit the recombination of photogenerated electron–hole pairs, resulting in remarkable activity of cerium doped TiO2 catalyst. Desorption of the reaction products plays an important role on the deactivation of the catalyst.Display Omitted
Keywords: Ce doped TiO2 nanoparticles; Photocatalytic reduction of CO2; Liquid products; Sol–gel auto-ignited synthesis;
Enhanced SOFC cathode performance by infiltrating Ba0.5Sr0.5Co0.8Fe0.2O3 − δ nanoparticles for intermediate temperature solid oxide fuel cells by Xifeng Ding; Wenliang Zhu; Xiaojia Gao; Guixiang Hua; Jianfei Li (14-19).
Solid oxide fuel cells (SOFCs) as alternatives for energy conversion have exhibited some unique advantages such as wide fuel flexibility, high energy efficiency and exhaust heat. An innovative composite cathode for SOFCs consisting of a high conductive La0.7Sr0.3CuO3 − δ (LSCu) electrode backbone infiltrated by nano and Ba0.5Sr0.5Co0.8Fe0.2O3 − δ (BSCF) particles with high electro-catalytic activity has been successfully fabricated by a simple solution infiltration process. The effect of BSCF nano catalyst on the electrochemical activity and stability of LSCu cathode was investigated and the inherent oxygen reduction reaction (ORR) mechanism is discussed. The polarization resistance is 0.043 Ω cm2 for 15 wt.% BSCF infiltrated LSCu cathode, and is reduced ~ 92.6% to that pure LSCu (0.58 Ω cm2) at 700 °C. The short term stability demonstrates that the electrochemical activity can be further improved in the first period about 40 h at 700 °C. After operated for 70 h, the electrochemical performance of the composite cathode became stable. A conductive scaffold (e.g. LSCu) modified with a highly catalytic nano particles (e.g. BSCF) is an attractive approach to fabricate cathodes with high electrochemical performance and stability.Display Omitted
Keywords: Solid oxide fuel cells; Composite cathode; Infiltration; Surface modification;
Sequential extraction and thermal dissolution of Shengli lignite by Man Ding; Yun-Peng Zhao; You-Quan Dou; Xian-Yong Wei; Xing Fan; Jin-Pei Cao; Yue-Lun Wang; Zhi-Min Zong (20-24).
Shengli lignite (SL) was subjected to sequential extraction (SE) with carbon disulfide, benzene, methanol, acetone, and tetrahydrofuran under ultrasonication to afford extracts 1–5, respectively, and the residue (RSE, i.e., residue from SE). The RSE was subjected to sequential thermal dissolution (STD) in benzene, methanol, and acetone in a batch autoclave from 210 to 330 °C to afford soluble portions (SPs) and the residue (RSTD, i.e., residue from STD). The total yield of extracts 1–5 is only 2.86%, while the yields of SPs from STD in benzene, methanol, and acetone are 5.69%, 10.15%, and 48.41%, respectively. The SPs from STD in benzene and methanol mainly consist of hydrocarbons and phenols, while ketones are the main compounds detected in the SP from STD in acetone and most of nitrogen-containing organic compounds appear in the SP from STD in acetone. During STD in acetone, acetone conversion to phorone, isophorone, and their derivatives was confirmed.Display Omitted
Keywords: Lignite; Sequential extraction; Sequential thermal dissolution; Organic species;
Effect of calcination temperature on the activity and structure of MnO x /TiO2 adsorbent for Hg0 removal by Anchao Zhang; Zhihui Zhang; Junjie Chen; Wei Sheng; Lushi Sun; Jun Xiang (25-33).
The influence of calcination temperature (200–800 °C) on the activity and structure of MnO x /TiO2 adsorbent prepared by a deposition–precipitation method is investigated by using an elemental mercury (Hg0) removal setup and a variety of techniques such as N2 adsorption/desorption, SEM, XRD, H2-TPR, FTIR, TG-DSC, and XPS. The results exhibit that the Hg0 removal activity of MnO x /TiO2 adsorbent is closely related to the calcination temperature. The Hg0 removal activity firstly increases below 400 °C and then decreases with the increase of calcination temperature. Calcination at various temperatures may cause several successive structural changes such as the evaporation of water, decomposition of manganese compounds, enhancement of MnO x crystallization, and the crystal phase transformation of MnO x and TiO2. Some agglomerations of MnO x /TiO2 occur at higher calcination temperature, resulting in the drastic decreases of BET surface area and pore volume. Meanwhile, the particle sizes greatly increase. With an increase in calcination temperature, the oxidation state of manganese would convert from Mn4 + to Mn3 +, and the surface chemisorbed oxygen decreases due to the removal of surface chemisorbed oxygen. Excessively higher calcination temperature would lead to the deactivation of MnO x /TiO2.Display Omitted
Keywords: Calcination temperature; MnO x /TiO2 adsorbent; Mercury; Removal;
VOx promoted Ni catalysts supported on the modified bentonite for CO and CO2 methanation by Xiaopeng Lu; Fangna Gu; Qing Liu; Jiajian Gao; Youjun Liu; Huifang Li; Lihua Jia; Guangwen Xu; Ziyi Zhong; Fabing Su (34-46).
Ni catalysts supported on the raw bentonite (RB) and the acid–alkali treated bentonite (B), which were prepared by the impregnation method, were tested for methanation of CO2 and CO respectively to produce synthetic natural gas (SNG). XRD, nitrogen adsorption, SEM, TEM, TG, H2-TPR, and XPS were employed for the characterization of the samples. The results showed that the Ni catalysts supported on the B support were more active than that supported on the RB support because of the improved Ni particles dispersion on the former that had larger specific surface area. After addition of proper amount of the VOx promoter, the catalytic activity of the B supported catalysts was further improved. This could be attributed to the enhanced H2 uptakes, increased Ni dispersion, reduced Ni nanoparticle size, and the electronic effect of VOx that can promote dissociation of CO in the methanation reaction. In the lifetime test of CO2 and CO methanation under atmospheric pressure, the Ni/B catalysts promoted by the VOx promoter were highly stable as they had superior anti-coking and anti-sintering performance to the catalyst without the promoter. This type of the catalysts is promising for industrial production of SNG.VOx-added Ni catalysts supported on the modified bentonite (B) were prepared by co-impregnation method for methanation reactions to synthesize substitute natural gas. The catalysts showed the enhanced catalytic performance and stability toward anti-sintering and anti-coking.Display Omitted
Keywords: CO methanation; CO2 methanation; SNG; Macro-mesoporous; Bentonite; VOx;
Dissolution of lignite in ionic liquid 1-ethyl-3-methylimidazolium acetate by Zhi-Ping Lei; Lu-Lu Cheng; Su-Fang Zhang; Heng-Fu Shui; Shi-Biao Ren; Shi-Gang Kang; Chun-Xiu Pan; Zhi-Cai Wang (47-51).
The extraction behaviors of three lignites with ionic liquid (IL)-1-ethyl-3-methylimidazolium acetate (EMIA) were studied in this work. The effects of extraction temperature and lignite type on extract yield and product compositions were primarily investigated. Also the relationship between the extract yield of lignites and the quantities of oxygen-containing functional groups in lignites was investigated. It was found that EMIA is a more efficient solvent for the dissolution of lignites compared to the performance of 1-butyl-3-methyl-imidazolium chloride (BMIC). Extraction temperature and lignite type significantly affect extraction behaviors of lignite with EMIA. The extract yield of lignites with EMIA increases with the quantity of carboxylic groups in lignite increases. Only a small amount of aliphatic alkyl structure components are extracted at low temperature. More aromatic structure components are extracted by EMIA at high extraction temperature.Display Omitted
Keywords: Lignite; Extraction; EMIA;
Pyrolysis of Huolinhe lignite extract by in-situ pyrolysis-time of flight mass spectrometry by Liang Zou; Lijun Jin; Xinglong Wang; Haoquan Hu (52-59).
In this paper, tetrahydrofuran extract of Huolinhe lignite was selected as sample and a new in-situ pyrolysis-time of flight mass spectrometry (PY-TOF-MS) was used to study the evolution of initial pyrolysis products of extract. Electron impact mass spectrometry (EI-MS) and vacuum ultraviolet photoionization mass spectrometry (VUV-PI-MS) were used to detect different pyrolysis products. The similarity of DTG curve and ion counts of PY-TOF-MS shows the good performance of the equipment in coal pyrolysis. EI-MS results show that the oxygen containing gases present multiple peaks; however, H2 and CH4 present single evolution peak. More evolution peak numbers of CO2 and H2O in extract pyrolysis than that of coal show that extract has more advantages to investigate the formation mechanisms of CO2 and H2O. VUV-PI-MS is proved to be a useful method to analyze tar components. The aliphatics and aromatics in initial products have relatively larger molecular weight than those of the low boiling point substances in extract. The polycyclic aromatic hydrocarbons have an increasing tendency with ring number. Phenols exhibit different evolution curves, and C7H8O and C8H10O are dominant compounds. These results illustrate that different initial products have different formation mechanisms and oxygen atom plays an important role during pyrolysis.A new in-situ pyrolysis-time of flight mass spectrometry was used to study the pyrolysis behaviors of tetrahydrofuran extract of Huolinhe lignite. Pyrolysis products can be detected by electron impact and vacuum ultraviolet photoionization mass spectrometry.Display Omitted
Keywords: Coal extract; THF; Pyrolysis; TOF-MS; Vacuum ultraviolet photoionization;
Pilot plant results for a precipitating potassium carbonate solvent absorption process promoted with glycine for enhanced CO2 capture by Kathryn Smith; Andrew Lee; Kathryn Mumford; Sheng Li; Indrawan; Navin Thanumurthy; Nick Temple; Clare Anderson; Barry Hooper; Sandra Kentish; Geoff Stevens (60-65).
The absorption performance of a glycine promoted precipitating potassium carbonate (K2CO3) solvent absorption process for carbon dioxide (CO2) capture has been presented using a laboratory scale pilot plant. Glycine has been added as a rate promoter to 40–45 wt.% K2CO3 solutions to examine the enhancement of the CO2 absorption process. The laboratory scale pilot plant has been designed to capture 4–10 kg/hr of CO2 from an air/CO2 mixture at a feed gas rate of 30–55 kg/hr. Performance data of the absorber including pressure drop, holdup and CO2 removal efficiency has been collected from the pilot plant and presented for a range of operating conditions. The addition of glycine was found to improve the CO2 recovery rate by up to 6 times whilst also slightly increasing the pressure drop and holdup measured in the packed absorption column which is likely due to a reduction in the surface tension of the solvent. Additionally, increasing the K2CO3 solvent concentration and operating with a higher CO2 feed gas concentration were found to increase the CO2 recovery results. Finally performance data from the absorber has been used to validate an Aspen Plus simulation of the system.Display Omitted
Keywords: CO2 capture; Potassium carbonate; Glycine; Solvent absorption; Pilot plant;
Ag modified Mn–Ce/γ-Al2O3 catalyst for selective catalytic reduction of NO with NH3 at low-temperature by Fan Cao; Jun Xiang; Sheng Su; Pengying Wang; Song Hu; Lushi Sun (66-72).
Mn–Ce/γ-Al2O3 granular catalyst was modified by adding silver and then developed in the low temperature selective catalytic reduction (SCR) of NO with NH3. It showed outstanding SCR activity in low and middle temperature region and achieved 95% NO conversion at 250 °C. It also performed excellent space velocity tolerance in a wide range. The characterization results showed that silver mainly existed in the form of Ag and Ag2O, which could promote the migration of surface active oxygen and increase the weak Brønsted and strong Lewis acid sites. NO adsorption benefited from the addition of silver and mainly existed as the bridged nitrite and bidentate nitrate species. Introducing O2 could create more oxidized surfaces and promote the NO oxidation, which prompted NO to be adsorbed as unstable monodentate nitrate, bridged nitrite and nitrate species. NH3 could be adsorbed mainly on the Lewis acid sites as coordinated NH3 and − NH2 species, which also could be promoted by the introduction of O2. The mechanism of SCR reactions was also explored. It showed that most NO could be adsorbed as the unstable nitrates or nitrites firstly and then reacted with the adsorbed ammonia species. The most possible reaction pathway followed the Langmuir–Hinshelwood mechanism.Display Omitted
Keywords: SCR; Low temperature; Silver; Mn–Ce/γ-Al2O3; In situ DRIFTS;
Effect of char on co-pyrolysis of biomass and coal in a free fall reactor by Junjie Zhang; Cui Quan; Yujie Qiu; Shaoping Xu (73-79).
Fast pyrolysis and co-pyrolysis of pine sawdust (SD) and sub-bituminous coal (SB) were carried out in a free fall reactor. There is a gas–solid separator at the bottom of the reactor, where a controlled re-contact of the primary volatiles with the nascent char could be achieved. The experiments of the individual fuels with the volatiles–char re-contact resulted in increased tar yield and decreased the light hydrocarbon gas concentrations compared with that without the volatiles–char re-contact. During the co-pyrolysis of SD and SB, synergies were observed to have produced more tar at different biomass blending ratios (BR). Particularly, the re-contact of the volatiles–char effectively enhanced tar generation and suppressed water formation. The volatiles–char interactions promoted the tar generation mainly at the char bed temperature range from 600 °C to 700 °C. At the optimum condition with the BR of 0.50 and char bed temperature of 700 °C, the tar yield increased up to 28.7%. The co-pyrolysis and volatiles–char interactions favored the acidic components generation in the liquid products. Especially, the volatiles–char re-contact during co-pyrolysis improved the quality of tar by decreasing its asphaltene content.Display Omitted
Keywords: Co-pyrolysis; Biomass; Coal; Volatiles–char interactions;
Numerical study of combustion characteristics for pulverized coal under oxy-MILD operation by Yaojie Tu; Hao Liu; Sheng Chen; Zhaohui Liu; Haibo Zhao; Chuguang Zheng (80-90).
MILD (Moderate or Intense Low-oxygen Dilution) combustion is a novel technology to reduce NOX emission from combustion. With the development of this technology, it is expected to combine this technology with oxy-fuel combustion to jointly control the pollutants from fossil fuel combustion. The present paper investigates the combustion characteristics of coal under oxy-MILD operation with the aid of CFD simulations. A seven-step global reaction mechanism is used for modeling coal combustion involving gaseous volumetric reaction and particle surface reaction. The predicted results using the adopted models for the reference case agree well with the experimental results. It is revealed that, the combustion temperature level increases with the enhancement of initial oxygen concentration because of the reduced injection momentum and promoted heat release. The in-furnace CO formation increases but the final CO emission reduces when enhancing the oxygen concentration under oxy-MILD combustion. Moreover, oxy-MILD combustion shows a greater potential on NOX formation reduction than air-MILD combustion, and this potential is promoted at higher initial oxygen concentration.The aim of this study was to investigate the different combustion characteristics of coal MILD combustion under air (O2/N2) and oxy-fuel (O2/CO2) atmospheres. The temperature and species distributions as well as NO formation are numerically compared. Oxy-MILD combustion of coal has shown greater potential on NO reduction than air-MILD combustion, and this advantage is promoted by enhancing the oxygen level in oxidizer due to larger CO release.Display Omitted
Keywords: MILD combustion; Oxy-fuel combustion; Coal combustion; Combustion modeling; NOX conversion;
The structure and reactivity of a low-sulfur lacustrine oil shale (Colorado U.S.A.) compared with those of a high-sulfur marine oil shale (Julia Creek, Queensland, Australia) by Mohammad W. Amer; Marc Marshall; Yi Fei; W. Roy Jackson; Martin L. Gorbaty; Peter J. Cassidy; Alan L. Chaffee (91-98).
Oil shales from two different continents (Australia and North America) of different ages (100 and 40 million years) and origins (one marine, one lacustrine) have been reacted in the range 355–425 °C under H2 or N2 for 1 or 5 h with or without the addition of catalyst. The shales differed in S content, and the nature of the mineral matter, but both had high atomic H/C ratios. The overall reactivity of the two shales was similar and high yields of soluble products could be obtained under relatively mild conditions with only small CO2 yields, but the temperature dependence of reactivity and the effect of potential catalysts differed markedly. Increasing the temperature and time led to increases in conversion but of different extents. Substituting H2 for N2 led to a large increase to conversion for the lower-atomic-H/C ratio marine oil shale. The CH2Cl2 solubles from the marine oil shale showed a larger range of compounds than those from the lacustrine oil shale which resembled the CH2Cl2 solubles from torbanite, a coal-like material derived from lacustrine algae.Comparison of product yields of Colorado and Julia Creek oil shalesDisplay Omitted
Keywords: Marine/lacustrine oil shales; Oil extraction; Oil structure; Thermogravimetric analysis; Gas chromatography–mass spectrometry; 1H NMR;
Separation of toluene from toluene/alkane mixtures with phosphonium salt based deep eutectic solvents by Yucui Hou; Zhongyi Li; Shuhang Ren; Weize Wu (99-104).
In this work, separation of aromatic hydrocarbons from aromatic/aliphatic mixtures by deep eutectic solvents (DESs) at room temperature was developed. It was found that DES formed by levulinic acid as hydrogen bond donor and tetrabutylphosphonium bromide (TBPB) as hydrogen bond acceptor could efficiently separate aromatic hydrocarbons from aromatic/aliphatic mixtures. Levulinic acid/TBPB mole ratio, DES/toluene mole ratio, toluene mole fraction, and extraction temperature had an influence on the selectivity and extraction rate of toluene. The extraction could be performed at optimal conditions of 6:1 mol ratio of levulinic acid to TBPB and 6.4:1 mol ratio of DES to toluene at room temperature. Toluene in DES could be recovered by distillation of toluene at 100 °C under reduced pressure and DES was reused four times without obvious decrease in weight, selectivity and extraction rate. The work may provide an environmentally friendly method to separate aromatic/aliphatic mixtures, which avoids using a large number of toxic organic solvents.The separation of aromatic hydrocarbons from aromatic/aliphatic mixtures by deep eutectic solvents (DESs) at room temperature was developed. The selectivity and extraction rate of aromatics could be tuned by selecting hydrogen bond donor and hydrogen bond acceptor that form DES. It was found that DES formed by levulinic acid (LA) and tetrabutylphosphonium bromide (TBPB) could efficiently separate aromatic hydrocarbons from aromatic/aliphatic mixtures.Display Omitted
Keywords: Separation; Deep eutectic solvent; Aromatic/aliphatic mixture; Tetrabutylphosphonium bromide; Levulinic acid;
Second-order Raman spectroscopy of char during gasification by Shuai Wang; Tingting Li; Liping Wu; Lei Zhang; Li Dong; Xun Hu; Chun-Zhu Li (105-111).
Raman spectroscopy has been widely used in the structural characterization of various carbonaceous materials. Through spectral deconvolution, FT-Raman spectroscopy has been used to gain insights into the transformation of char structure during gasification, providing new evidence to understand the char gasification mechanisms. These studies have mainly focused on the first-order Raman spectra in the range between 800 and 1800 cm− 1. Additional information can be gained from the second-order Raman spectra. This study aims to develop a new spectral deconvolution scheme for the second-order Raman spectra of chars from the gasification of coal and biomass. As our initial attempt, the second-order Raman spectra of chars in the range between 2000 and 3300 cm− 1 were deconvoluted into 7 bands representing the main structural features in the chars. Both total Raman peak area and band area ratios are used to gain information about the structural features of char. Using chars from the gasification of WA Collie sub-bituminous coal in CO2 and H2O as examples, the implication of the first-order and second-order Raman spectral data in terms of gasification mechanisms is discussed.Display Omitted
Keywords: Raman spectroscopy; Second order; Char structure; Gasification; Coal; Biomass;
Effect of acoustic field on minimum fluidization velocity and drying characteristics of lignite in a fluidized bed by Chongdian Si; Jianjun Wu; Yong Wang; Yixin Zhang; Guangjun Liu (112-118).
The fluidization and drying characteristics of Shengli lignite in a sound-assisted fluidized bed are investigated. The effects caused by sound frequency and sound pressure level on the minimum fluidization velocity and drying rate are studied. Experiments indicated that acoustic field can improve the fluidization quality and drying rate of Shengli lignite. The minimum fluidization velocity decreased with an increase in sound pressure level and has a minimum value at a sound frequency of 1.5 kHz. The drying rate of Shengli lignite was especially increased during the initial period of the drying process, while the effect was minor toward the end of process. Based on the determination of TG, FTIR, and BET, the structure changes of Shengli lignite were measured to assess the changes in the quality of dried lignite with the assistance of acoustic field. The weight loss rate of dried lignite decreased with the introduction of acoustic waves. Total pore volume, average pore diameter, and specific surface area were significantly reduced with introducing acoustic waves. Carbonyl decreased progressively with the assistance of acoustic field while carboxyl and hydroxyl increased and decreased thereafter. In addition, the energy consumption of fluidized bed drying system after inducing acoustic field is investigated.The effects caused by sound frequency and sound pressure level on the drying rate in a sound-assisted fluidized bed dryer are studied. The constant rate period becomes shorter and drying takes place mostly at falling rate period. Moisture removal at f = 1.5 kHz and SPL = 150 dB was higher and faster than the other investigated sound wave parameters.Display Omitted
Keywords: Lignite; Minimum fluidization velocity; Drying characteristics; Acoustic field; Fluidized bed;
Catalytic chemical looping combustion of carbon with an iron-based oxygen carrier modified by K2CO3: Catalytic mechanism and multicycle tests by Zhongliang Yu; Chunyu Li; Xuliang Jing; Qian Zhang; Zhiqing Wang; Yitian Fang; Jiejie Huang (119-124).
One of the major obstacles of chemical looping combustion (CLC) with solid fuels is the low reaction rate of solid fuels with an oxygen carrier. Alkali metal catalysts can be used to enhance the reaction rate. In this work, the catalytic reduction mechanism of a K2CO3 modified iron-based oxygen carrier by activated carbon (AC) and the multicycle CLC tests were investigated. The results confirm that the deep reduction of K2CO3 added iron-based oxygen carrier occurred at a high rate. The energy dispersive spectrometer (EDS) analysis shows that the catalytically active species of K2CO3 migrated from the oxygen carrier to the surface of AC during reduction, which could then catalyze the rate-limiting step (C–CO2 reaction) of the reduction process. Besides the catalytic effect of K2CO3, a remarkable autocatalytic effect of iron oxide itself on the reduction was also observed. The active species could also travel back to the oxygen carrier after reduction, which guaranteed the persisting catalytic effect in the multicycle tests. The loss of potassium primarily contributed to the deactivation of the oxygen carrier, but this deactivation can be partly retrieved and improved by the supplement of K2CO3.Display Omitted
Keywords: Chemical looping combustion; Oxygen carrier; Iron oxide; K2CO3; Autocatalysis; Potassium migration;
Effects of pretreatment of Pd/AC sorbents on the removal of Hg0 from coal derived fuel gas by Caixia Yue; Jiancheng Wang; Lina Han; Liping Chang; Yongfeng Hu; Hui Wang (125-132).
The Pd supported activated carbon (Pd/AC) sorbents were pretreated by 5 vol.% O2 or H2, and the Hg0 removal efficiency of the corresponding sorbents was compared in different atmospheres. X-ray photoelectron spectroscopy, X-ray diffraction and X-ray absorption spectroscopy were employed to analyze the sorbents at different stages. These results indicated that the Hg0 removal efficiency of the untreated 1Pd/AC sorbent was higher than that of the pretreated sorbents. The efficiency of Hg0 removal from coal derived fuel gas is much higher in N2–H2S–Hg–H2 atmospheres than that in N2–H2S–Hg atmospheres and it can be maintained at about 91.4% for 360 min. There exist three types of Pd forms over Pd/AC sorbent, i.e. Pd0, Pd2 + and Pd2H, and among which Pd0 is the active species for Hg0 removal over Pd/AC sorbent. H2 can promote the Hg0 removal due to the in situ reducing of palladium oxide in the process of sorbent evaluation. H2 and O2 in the pretreated atmosphere suppressed the Hg0 removal due to the formation of inactive palladium hydride and easily sulfidized palladium oxide, respectively, and then the decrease of Pd0 content.Display Omitted
Keywords: Hg removal; Pd/AC sorbents; Coal derived fuel gas; Pretreatment;
Modeling of kraft lignin pyrolysis based on bond dissociation and fragments coupling by Xiaojin Guo; Zhenyu Liu; Qingya Liu; Lei Shi (133-149).
It is generally recognized that pyrolysis of biomass involves two steps: dissociation of covalent bonds to generate free radical fragments and coupling of the free radical fragments to form products. Experiments and simulations on biomass pyrolysis in the literature, however, ignored the role of each step and provided only the overall results of the two steps. Based on the two-step mechanism, this work simulates pyrolysis of a structural unit of kraft lignin. The first step is assumed to be governed by Boltzmann distribution of each bond in the unit at a given temperature and time, while the second step is assumed to follow Monte-Carlo algorithm. The Boltzmann–Monte Carlo pyrolysis model built is analyzed with the aid of basic and secondary assumptions. The mode is further validated by simulating pyrolysis of kraft lignin and comparing the results with experimental data in the literature. It is found that the model simulates the pyrolysis behavior reasonably well, in terms of changes in bonds’ population and amounts of radicals formed versus temperature and time.Display Omitted
Keywords: Lignin pyrolysis; Modeling; Boltzmann–Monte Carlo; Covalent bond; Radical mechanism;
Effect of polypropylene on the pyrolysis of flame retarded high impact polystyrene by Chuan Ma; Lushi Sun; Limei Jin; Changsong Zhou; Jun Xiang; Song Hu; Sheng Su (150-156).
Pyrolysis of high impact polystyrene (HIPS), containing decabromodiphenyl oxide as brominated flame retardant (BFR) with Sb2O3 as a synergist (Br–Sb–HIPS), often leads to high concentrations of toxic brominated organic compounds in the pyrolysis oils which would detrimentally impact the reuse of these pyrolysis oils. In this work, the pyrolysis of Br–Sb–HIPS in the presence of polypropylene (PP) at different blending mass ratios using a fixed bed reactor at 410 °C was performed to investigate what the effect of PP has on the pyrolysis of Br–Sb–HIPS. The thermal decomposition characterization of Br–Sb–HIPS and PP was investigated using thermogravimetry analysis (TGA). The pyrolysis oils were analyzed using Fourier transform infrared spectroscopy (FTIR) and gas chromatography–mass spectrometry (GC–MS). TGA revealed that there was a synergistic interaction between Br–Sb–HIPS and PP during co-pyrolysis process. More wax/oil and less gas were produced and the yields of toluene, ethylbenzene, styrene and many other compounds in the pyrolysis oil reversely increased in the presence of PP. Moreover, PP was found to be effective to reduce bromine in the pyrolysis oil. When 30 wt.% PP was blended into Br–Sb–HIPS, it could reduce the amount of bromine in pyrolysis oil to 38% of the original value.This graph shows the effect of PP on debromination (red solid, experimental; blue dash, expected; black solid, debromination rate). It was found that the content of bromine in the pyrolysis oil decreased as PP increases and the most important point was that the trend was below the expected trend without considering the effect of PP.Display Omitted
Keywords: HIPS; Pyrolysis; Debromination; PP; Decabromodiphenyl oxide;
A FeCl3-based ionic liquid for the oxidation of anthracene to anthraquinone by Yu-Gao Wang; Xian-Yong Wei; Sheng-Kang Wang; Rui-Lun Xie; Peng Li; Fang-Jing Liu; Zhi-Min Zong (157-161).
N-butylpyridinium bromide ferric trichloride (NBPBFTC), a FeCl3-based ionic liquid, was prepared by a two-step method. NBPBFTC significantly catalyzed the oxidation of anthracene to anthraquinone (AQ) using aqueous hydrogen peroxide (AHPO) as the oxidant. The optimal conditions were determined to be 50 °C, 45 min, 100 mg NBPBFTC, and 1 mL AHPO for the oxidation of 50 mg anthracene. Under the conditions, AQ was obtained in a yield of 99.5%. NBPBFTC can be reused at least 3 times without substantial decrease in activity. With the intense π–π interaction between anthracene and pyridine-based cation in NBPBFTC, anthracene is soluble in the reaction system. Meanwhile, the iron-based anion and AHPO form a Fenton-like reagent to produce HOO· and HO·, which attack 9-position in anthracene to induce anthracene oxidation to AQ.Display Omitted
Keywords: FeCl3-based ionic liquid; Oxidation; Anthraquinone; Hydrogen peroxide;
Impacts of CO2 leakage into shallow formations on groundwater chemistry by Qianlin Zhu; Xiaochun Li; Zhenbo Jiang; Ning Wei (162-167).
Geological storage of CO2 is one option for mitigating atmospheric emissions of carbon dioxide. However, the injected CO2 has the possibility of leakage. The leaked CO2 may move upward into shallow formations and thereby affects shallow groundwater. To investigate this effect, 27 tonnes of gaseous CO2 was injected into an aquifer about 180 m below a surface. Periodic groundwater samples were studied to identify shift of hydro-chemical parameters, including pH, TDS, ORP, Ca, Mg, Na, HCO3, Cl, SO4, Pb, Fe, and F. The results indicated that CO2 dissolution and reaction concurrently reduced aquifer pH levels and increased concentrations of TDS, Ca, Mg, HCO3, and F. ORP level and SO4 concentration remained static. Pb and Fe concentrations were lower than the detection limit 1 mg/L and 0.02 mg/L, respectively. After the CO2 breakthrough, Cl concentration increased to a stable level slightly higher than the background concentration. The shift in groundwater levels of Ca and Mg was attributed to dolomite (or Mg-rich calcite) and calcite-dominant dissolution processes. Results indicated linear approximations between concentrations of F vs. HCO3 (slope 0.0036) and F vs. Ca (slope 0.013). Additionally, the TDS and the total molar concentration of Ca and Mg showed linear correlations with increased levels of HCO3.Display Omitted
Keywords: Geological storage; CO2 leakage; Shallow groundwater; Groundwater contamination; Groundwater chemistry;
Control of NO and Hg0 emissions by SCR catalysts from coal-fired boiler by Jun Xiang; Pengying Wang; Sheng Su; Liqi Zhang; Fan Cao; Zhijun Sun; Xi Xiao; Lushi Sun; Song Hu (168-173).
CuO/γ-Al2O3 and CuO–MnO2–Fe2O3/γ-Al2O3 catalysts were synthesized by impregnation method. Their performances for selective catalytic reduction (SCR) were explored in a 200 MW coal-fired power plant boiler tail flue. The effects of catalyst amounts, NH3/NO molar ratios, abrasion resistance, catalyst regeneration and the catalytic efficiencies for Hg0 oxidation were also discussed here. The optimum temperature range for the SCR of NO over fresh catalysts was 300 ~ 400 °C. In the optimum temperature range, the efficiencies of the two catalysts were over 80%, with a maximum efficiency of nearly 90% obtained at 350 °C. Reducing the catalyst amounts to half did not change the efficiency dramatically. The highest SCR activity was obtained with NH3/NO molar ratios ranging from 1.0 to 1.2. Abrasion resistance test indicates that the mechanical strength of the catalysts can bear the industrial scale and long-term erosion of fly ash. The activities of the catalysts remained constant during a 200 h test. Meanwhile, the catalysts were able to maintain excellent NO reduction efficiency after three times recycling. CuO/γ-Al2O3 and CuO–MnO2–Fe2O3/γ-Al2O3 achieved 40% and 80% Hg0 oxidation efficiency, respectively. The present study provides a promising catalyst for NO and Hg0 removal for coal-fired power plants.Display Omitted
Keywords: Catalytic oxidation; SCR; NO; Hg0;
Effect of steam concentration on char reactivity and structure in the presence/absence of oxygen using Shengli brown coal by Yong-gang Wang; Xu-jun Chen; Sa-sha Yang; Xin He; Zong-ding Chen; Shu Zhang (174-179).
Steam-char reactions play a vital role in the gasification process and the presence of oxygen is inevitable in almost all commercial gasifiers. This study aims to investigate the effects of steam concentration on the behavior of Chinese Shengli brown coal gasification in the presence and absence of low concentration of oxygen in a newly-designed drop-tube quartz reactor. Experimental results indicate that the variation in steam concentration had a significant impact on coal conversion, largely depending on reaction temperatures and availability of oxygen. The coal conversion could somehow decrease with increasing steam concentration in the presence of low concentration of oxygen. Meanwhile, the presence of oxygen in the gas has enhanced the Na retention in char probably due to the formation of O-containing compounds or complexes on the char surface. The char structure measured by Raman spectroscopy suggests that the selective consumption of small aromatic ring systems by steam-char reactions was getting less significant when the steam concentration increased to more than 15% by volume. Furthermore, the isothermal reactivities of chars determined by TGA in air imply that the reaction pathways of char-steam and char-oxygen were likely different as the reactivity curves showed totally different shapes.Display Omitted
Keywords: Gasification; Steam concentration; Brown coal; Reactivity; Char structure;
Tech-economic assessment of a coproduction system integrated with lignite pyrolysis and Fischer–Tropsch synthesis to produce liquid fuels and electricity by Yang Fan; Qun Yi; Fangzhou Li; Lan Yi; Wenying Li (180-186).
A novel coproduction system of lignite pyrolysis integrated with Fischer–Tropsch synthesis and coal-tar hydrogenation to produce liquid fuels and chemicals is proposed. The moisture content of the lignite, the gasifier adopted and the choice of electricity generation are the critical factors that make a big difference in the assessment of the system. Sensitivity analysis of different moisture contents and gasifier types are investigated and comparisons are done between processes with and without electricity generation. The results showed that the system could benefit a lot from the decrease of moisture content of feedstock, and that although requiring higher financial investment, Shell-gasifier-based process would produce more liquid. Moreover, applying the electricity generation system would enhance the economic performance and make an impact on the energy efficiency. By the energy and economic assessments, nearly 40% of the low heat value and over 15% of the internal rate of return in the best case are obtained at an annual handling scale of 5 million tons of lignite. Meanwhile, over half a million tons of liquid are obtained and the CO2 emission is within the range of 7.5–9.5 t/t-oil.Display Omitted
Keywords: lignite pyrolysis; Fischer–Tropsch synthesis; liquid fuels; electricity generation; assessment;
Ultrasonic-assisted preparation of highly reactive Fe–Zn sorbents supported on activated-char for desulfurization of COG by Jinxiao Dou; Jianglong Yu; Arash Tahmasebi; Fengkui Yin; Sushil Gupta; Xianchun Li; John Lucas; Chuan Na; Terry Wall (187-194).
The desulfurization properties of Fe–Zn sorbent prepared by impregnating Fe and Zn into lignite char via ultrasonic-assisted impregnation (UAI) were investigated in comparison with the mechanical stirring (MS) method. The sulfidation experiments were carried out using a fixed-bed quartz reactor under ambient pressure. The amounts of metals loaded into char were measured by inductively coupled plasma atomic emission spectrometry (ICP-AES). The crystalline phases and chemical structure of sorbents before and after sulfidation were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), respectively. The morphology of sorbents was analyzed by using scanning electron microscope (SEM) with an energy dispersive X-ray (EDX) auxiliary. The experimental results showed that metal oxides as the active components were evenly dispersed on char as nanoparticles. The impregnation of active components was significantly improved by the ultrasonic-assisted impregnation method. When sorbents were prepared by ultrasonic-assisted impregnation, the metal oxide particles became smaller and more evenly dispersed on the char matrix which resulted in higher desulfurization efficiency and sulfur uptake capacity of the sorbents. The BET results showed that the physical properties of sorbents (surface area and pore volume) significantly improved when prepared by UAI method compared to MS method. The sulfidation temperature had a significant effect on desulfurization performance of char supported sorbents. The Fe:Zn molar ratio of 2:1, and impregnation time of 9 h were suggested as the optimal preparation conditions during ultrasonic-assisted impregnation.Display Omitted
Keywords: Coke oven gas; Sulfidation; Char supported Fe–Zn sorbent; Ultrasonic-assisted impregnation; Sulfur capacity;
Study of the microtextural transformation of coal char during supercritical water activation by Xianxian Zhou; Xuan Qu; Rong Zhang; Jicheng Bi (195-202).
Low-rank coal chars with different structures were prepared in a fixed-bed pyrolyzer. These coal chars were activated in a semi-continuous tubular supercritical water (SCW) reactor to produce activated carbon. Raman spectra data showed that the amount of aromatic carbon increased with pyrolysis temperature. After SCW activation, smaller aromatic ring units gradually disappeared in SCW, while large aromatic rings in the carbon matrix evolved into the pore structure. Corresponding to the results of nitrogen adsorption, different structures had different reaction rates as a result of SCW exposure, which led to the production of different pore textures. One of the possible pathways in the SCW activation process is proposed. Although there is a strong association between the ratio of cross-linked structures and BET surface area at higher pyrolysis temperatures, the texture of activated carbon is mainly related to the degree of coal conversion achieved.Display Omitted
Keywords: Lignite; Activated carbon; Supercritical water; Raman spectroscopy; Pore texture;
Effects of oxygen partial pressure on the performance stability of impregnated La0.6Sr0.4Co0.2Fe0.8O3 − δ–Sm0.2Ce0.8O2 cathodes of solid oxide fuel cells by Yihui Liu; Yong Cao; Shengbing Yang; Dong Yan; Bo Chi; Jian Pu; Li Jian (203-206).
The stability and surface composition of La0.6Sr0.4Co0.2Fe0.8O3 − δ (LSCF)–Sm0.2Ce0.8O2 (SDC) cathodes prepared by impregnation are investigated at 750 °C under open circuit and different oxygen partial pressures. The performance degradation during the test at Po2 = 0.21 atm is closely related to the low frequency mass transfer process. Little change of the electrochemical performance of cathodes is observed after 24 h test at Po2 = 0.001 atm. XPS patterns show that the decrease in oxygen partial pressure leads to the suppression of Sr enrichment on the surface of cathodes and retards the performance degradation.Display Omitted
Keywords: Stability; Cathodes; Impregnation; Oxygen partial pressure; Surface composition;
A new technique of carbon capture by ammonia with the reinforced crystallization at low carbonized ratio and initial experimental research by Jianmin Gao; Yu Zhang; Dongdong Feng; Qian Du; Mengmeng Yu; Min Xie; Long Sun; Shaohua Wu (207-211).
A new technique of carbon capture by ammonia with the reinforced crystallization was put forward in this paper in view of existing problems. Through the application of low concentration of ammonia with alcohols added in to reinforce crystallization process, ammonia escapes less, and the load capacity increases and at the same time, low energy consumption of regeneration could be achieved easily. By experiments and theoretical calculation, it was found that the absorbent capacity could reach 1.64 kgCO2/kgNH3, and ammonia escape at the outlet could be neglected. What's more, through rough estimation, thermal energy consumption for regeneration was only about 1/3 as much as that of conventional rich solution regeneration. In conclusion, the new technique is an improvement with great advantages for carbon capture by ammonia.
Keywords: Aqueous ammonia; Mixed absorbent; CO2; Crystallization; Regeneration energy;