机械工程学报

Structural evolution of Xianfeng lignite during hydrothermal treatment

LIU Peng, ZHOU Yang, LU Xi-lan, WANG Lan-lan, PAN Tie-ying, ZHANG De-xiang

2016, 44(2): 129-137.

[Abstract](171) [FullText HTML] (204) [PDF 1119KB](0)

Abstract:
Xianfeng lignite (XF) was used as raw material to investigate its structural evolution during hydrothermal treatment in a 500 mL autoclave.The structure was characterized by solid state ¹³C nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FT-IR).The results show that the carbon contents increase and oxygen contents decrease after hydrotnermal treatment.The weak bonds in lignite are broken and the oxygen functional groups decrease gradually during hydrothermal treatment below 240℃.Hydrogen is donated from water to lignite through ionic pathway and transferred into lignite.The methyl carbon increases at 200℃ and then decreases.The methenyl carbon increases from 4.80% in XF to 13.16% in XF-240.The released gas is mainly CO₂ during hydrothermal treatment.The hydrocarbon composition in released gas increases with the treated temperature.The covalent bonds are broken above 240℃.The hydrocarbon composition in released gas increases from 2.13% at 240℃ to 8.59% at 300℃.The aliphatic carbon in lignite deceases from 44.83% in XF-240 to 39.49% in XF-300.The oxygen-linked carbon in lignite decreases from 12.57% in XF-240 to 1.49% in XF-300.Hydrothermal treatment plays a role in deoxygenation and upgrading of raw lignite.The oxygen contents decrease by about 30% and the aromatic carbon increases to 60.50% at 300℃.

Application of FLASHCHAIN model in pyrolysis of Wangqing oil shale

WANG Qing, YANG Qian-kun, XU Xiang-cheng, CUI Da, ZHANG Hong-xi, WANG Yi-fan

2016, 44(2): 138-145.

[Abstract](105) [FullText HTML] (122) [PDF 676KB](0)

Abstract:
The carbon atom chemical structure of three Wangqing oil shales was characterized by ¹³C-NMR techniques, and twelve important parameters of the carbon skeleton structure were obtained.Thermogravimetric-Fourier transform infrared spectroscopy (TG-FTIR) tests were used to obtain the formation of light gases during pyrolysis at 50℃/min and the final temperature of 600℃.The FLASHCHAIN model, which was established based on the structure of fuel, was employed to simulate the evolution of pyrolysis products and compared with the experimental tests.The results show that the model has a good simulation below 520℃, some errors occur above 520℃ due to the influence of secondary pyrolysis reactions and decomposition of minerals in the shale.The errors increase gradually with the increasing pyrolysis temperature.

Mechanism and product characteristics of pyrolysis-activation coupling reaction of Shenfu coal

LIU Yuan, HE Xin-fu, ZHANG Ya-gang, YANG Fu-sheng, REN Xiu-bin, ZHOU An-ning

2016, 44(2): 146-153.

[Abstract](176) [FullText HTML] (102) [PDF 5546KB](0)

Abstract:
The characteristics of products from Shenfu coal pyrolysis-activation coupling reaction were investigated in a two-stage fixed bed reactor.The effect of pyrolysis temperature and activating agents (H₂O (g), CO₂ and H₂O (g)/CO₂) on the characteristics of products was analyzed.The mechanism of pyrolysis-activation coupling reaction was revealed.The results show that the pyrolysis temperature has little effect on the CO₂ chemical reactivity of the chars.The tar yield of Shenfu coal pyrolysis is significantly increased by using pyrolysis-activation coupling process, and the tar yield is up to 17.8%.The effect of different activating agents on the yield of mixed coal gases (MCG) and tar is in the order of H₂O (g)>H₂O (g)/CO₂>CO₂ and the main components of tar are saturates and aromatics.The specific surface area of activated carbon can be effectively improved by using H₂O (g)/CO₂ as the activating agents, and the BET specific surface area reaches to 845.37 m²/g.The mechanism of pyrolysis-activation coupling process is that the synthesis gases (SG) from the activation section can provide hydrogen source for coal hydropyrolysis in pyrolysis section, and the rich hydrogen radicals can promote the reaction and change the product distribution and properties.

Effect of additive iron ore on pyrolysis characteristics of a low rank coal from Hami

ZHAO Hong-yu, LI Yu-huan, SONG Qiang, LÜ Jun-xin, SHU Yuan-feng, WANG Zi-min, YAN Jie, ZENG Ming, SHU Xin-qian

2016, 44(2): 154-161.

[Abstract](130) [FullText HTML] (108) [PDF 1537KB](0)

Abstract:
The effect of iron ore on pyrolysis characteristics of a low rank coal from Hami was explored.By means of thermogravimetric analyzer (TGA), fixed bed reactor, fourier transform infrared spectroscopy (FT-IR), gas chromatograph (GC) and gas chromatography-mass spectrometer (GC-MS), the changes of pyrolysis reactivity, products distribution, the functional groups in the tar and the composition of tar of three coal samples were investigated and analyzed.The results show that when the pyrolysis temperature increases from room temperature to 150℃, the peak of weight loss rate of HM-CT and HM-JT gradually moves to high temperature.When the pyrolysis temperature is more than 450℃, the catalytic effect of different iron ores on coal pyrolysis is more obvious and in the order of specularite> the inherent minerals in HM> hematite.When the two kinds of iron ores added are up to 20%, there is a higher pyrolysis tar and gas yield.The tar yield is 7.88% for HM-JT coal sample and the yield of H₂, CH₄, CO₂ and CO increases by 4.27%, 3.76%, 4.39% and 3.61%, respectively, compared with HM coal.For HM-CT coal sample, the tar catalytic cracking is influenced by the additive amount of iron ore.As the additive amount of specularite and hematite is increasing to 20%, the yield of tar decreases gradually, while the light tar yield rises to 6.37% and 5.34%, respectively for two iron ores, and the light tar fraction increases to 58.48% and 56.22%, respectively.Besides, the removal of oxygen in tar reaches to 43.16% and 36.89%, respectively.With the addition of iron ore, the relative content of m/p-xylene in tar decreases from 4.32% to 3.78% and 3.93%, respectively for two iron ores, and the relative content of toluene increases from 1.11% to 1.32% and 1.45%, respectively.The methyl substituents of o-cresol and m/p-xylenol molecules in tar are removed to produce phenol or cresol, and the demethylation for benzene series and phenolic compounds in tar on the specularite is stronger than that on the hematite.

Effect of pretreatment methods on the determination of alkali metal content in high alkali metal Zhundong coal

SONG Wei-jian, SONG Guo-liang, QI Xiao-bin, LÜ Qing-gang

2016, 44(2): 162-167.

[Abstract](208) [FullText HTML] (216) [PDF 567KB](0)

Abstract:
High alkali metal coal from four coal mines in Zhundong coalfield and its gasification fly ash were used to investigate the occurrence of alkali metal with five pretreatment methods including low temperature ashing,microwave digestion,national standards,cascade extraction and oxygen bomb combustion.The results show that the sodium in the high alkali metal coal exists mainly in the water soluble form,and the potassium is in the water insoluble form;The method of oxygen bomb combustion is the optimum one to determine the content of Na and K in high alkali coal and gasification fly ash,and the method of cascade extraction is also a better one to determine the content of Na.

Influence of coal tar distillates on coke formation during co-processing of Liaohe heavy crude oil with the distillates

JIA Qian-qian, YANG Jian-li, JIANG Xing-jia, HOU Pei-dong, LI Ying, GUO Qiang, YANG Yong

2016, 44(2): 168-176.

[Abstract](108) [FullText HTML] (134) [PDF 804KB](0)

Abstract:
The influence of coal tar distillates on coke formation during the processing of Liaohe heavy crude oil with the distillates was studied.The composition of feedstock was characterized by the elemental analysis,the proton nuclear magnetic resonance spectrometry,the synchronous fluorescence spectrometry and the group analysis techniques.It has been found that the coke formation of Liaohe heavy crude oil upon heating can be reduced by co-processing with the coal tar distillates.Under the experimental conditions,the coke yields from the co-processing(0.5%-5.9%) are lower than that from the weighted calculation(3.3%-6.4%);a positive synergetic effect was observed.The extent of the synergetic effect depends on the chemical composition and content of the distillates.Saturates,1-ring aromatics and condensed 4-ring aromatics may retard the coke formation,whereas 2-ring and 3-ring aromatics as well as condensed 2-ring aromatics may retard the coke formation.

Molecular characterization of sulfur-containing compounds in the wide fractions of Saudi Arabia atmospheric residue by supercritical fluid extraction fractionation

LIU Mei, ZHAO Hai-ling, SUN Qi, ZHAO De-zhi

2016, 44(2): 177-183.

[Abstract](126) [FullText HTML] (111) [PDF 1452KB](0)

Abstract:
Saudi Arabia atmospheric residue (SZAR) was subjected to supercritical fluid extraction fractionation (SFEF) and separated into four extractable fractions and an un-extractable end-cut.The SFEF subfractions were subjected to the simulated distillation analysis, gel permeation chromatography (GPC) for their molecular weight distributions, and open column liquid chromatography for their saturates, aromatics, resins, and asphaltenes (SARA) compositions, by high-temperature gas chromatography (GC).The density, carbon residue value, viscosity, and sulfur and nitrogen content along with the extraction pressure were determined.Sulfur compounds in wide fractions were converted to methylsulfonium salts, which were characterized by positive-ion electrospray ionization (ESI) and Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry (MS).The results indicated that the mass range and maximum peak intensity of the SFEF subfraction are increased as the SFEF subfraction becomes heavier.The molecules in various SFEF subfractions are separated by their polarity and molecular weight.The highest level in the various fractions is referred to S₁ class species and meanwhile, benzothiophene turns to be the dominant heteroatom compounds.Compared with the lighter fractions, heavier fractions have higher contents of S₁ and S₂ class species, wider range, higher molecular weight, and more aromatic cores.

Characteristics of Zhundong coal in chemical looping combustion with natural hematite as oxygen carrier

GE Hui-jun, SHEN Lai-hong, GU Hai-ming, SONG Tao, JIANG Shou-xi

2016, 44(2): 184-191.

[Abstract](119) [FullText HTML] (50) [PDF 883KB](0)

Abstract:
The characteristics of high-sodium Zhundong coal in chemical looping combustion (CLC) as well as the migration of sodium upon combustion were investigated in a fluidized-bed reactor with natural hematite as the oxygen carrier, in order to mitigate the severe slagging and fouling problems and enhance the utilization efficiency of Zhundong coal.The results indicated that the carbon conversion and reaction rate for Zhundong coal in CLC were evidently higher than those of other coals at 850-1 000℃; aluminosilicate Na₂O·Al₂O₃·6SiO₂ of high melting point is formed in the CLC process, which is effective to mitigate the severe slagging and fouling problems.During a 10-cycle CLC test, the reactivity of hematite increases with the increase of cycle number, whereas the sodium content in the CLC fly ash is reduced.

Rotating gliding arc plasma assisted hydrogen production from methane decomposition in argon

ZHANG Hao, ZHU Feng-sen, LI Xiao-dong, WU Ang-jian, BO Zheng, CEN Ke-fa

2016, 44(2): 192-200.

[Abstract](106) [FullText HTML] (98) [PDF 1519KB](0)

Abstract:
A kind of rotating gliding arc (RGA) argon plasma co-driven by tangential flow and magnetic field was investigated and used for hydrogen production from methane decomposition.In order to obtain insights into the physical characteristics of the RGA plasma, optical emission spectroscopy (OES) analysis was used to determine the electron temperature and electron density.In addition, the effects of feed flow rate and CH₄/Ar ratio on the performance of the methane decomposition process in this RGA plasma were also investigated.Results have shown that, the RGA plasma is a kind of unique plasma between thermal and non-thermal plasma, with electron temperature of 1.0-2.0 eV and electron density of 10¹⁵ cm^-3.In this system, the CH₄ conversion could be 22.1%-70.2% and it increased with the increase of flow rate or CH₄/Ar ratio.The H₂ selectivity varied from 21.2% to 61.2%, and with the augment of flow rate, the H₂ selectivity first varied slightly and then increased.A comparison of different non-thermal plasmas (e.g., microwave, radio frequency, and dielectric barrier discharge) showed that the RGA plasma could provide a relatively high CH₄ conversion and H₂ selectivity, as well as a relatively low energy consumption for H₂ production, while maintaining a high flow rate (i.e., processing capacity) of 6-20 L/min.

Separating phenols from high-temperature fraction of bio-oil by precipitation

ZHAO Xin, LI Kai, LI Ming, MA Shan-wei, ZHU Xi-feng

2016, 44(2): 201-208.

[Abstract](68) [FullText HTML] (101) [PDF 723KB](0)

Abstract:
To improve the utilization of chemicals in bio-oil, recovery of phenolic compounds from high temperature bio-oil fractions by metal ion precipitation was studied.The effects of concentration of sodium hydroxide solution, reaction temperature and reaction time on the recovery of phenolic compounds by magnesium ion were examined using gas chromatography-mass spectrometry (GC-MS).The results demonstrate that the precipitation was formed instead of a salt of magnesium phenols.The optimum reaction conditions are reaction temperature of 25℃, 2.5 mol/L of sodium hydroxide solution, and reaction time of 20 min.In this case, the recovery of 4-ethylphenol from high temperature bio-oil fractions reaches 34.97%.

Preparation of a novel solid acid catalyst SO₄^2-/Nd₂O₃/C and study of its performance for the synthesis of biodiesel from esterification reaction of oleic acid and methanol

SHU Qing, HOU Xiao-peng, ZHU Li-hua, SHEN Bang-po, MA Fei, WANG Jin-fu

2016, 44(2): 209-216.

[Abstract](116) [FullText HTML] (133) [PDF 2256KB](0)

Abstract:
A carbon material was prepared from the high temperature carbonization of waste camellia seed shell in a fluidized bed tubular reactor.The carbon material was applied as the catalyst support to prepare a new catalyst SO₄^2-/Nd₂O₃/C after it was simultaneously modified by Nd³⁺ and sulfonated by concentrated sulfuric acid through impregnation method.The catalyst was characterized by several physical and chemical characterization methods.The catalytic activity and reusability of SO₄^2-/Nd₂O₃/C were evaluated using it to catalyze the esterification of methanol and oleic acid for the synthesis of biodiesel.Results showed that the conversion of oleic acid was 96.70% when the methanol/oleic acid molar ratio was 2:1, reaction temperature was 90℃, and catalyst/reactants was 2% under reflux condensation for 120 min.After recycling of three times, the conversion of oleic acid was still 86.74%.High activity can be explained as follows:the electro-negativity of Nd is 1.14, which is smaller than O (3.44) and S (2.58), so it will provide lone electron pair to the empty 2p orbit of O and S, resulting in the formation of a stable coordination bond between Nd³⁺ and SO₄^2-.In addition, S=O double bond can induce a strong electron withdrawing effect, which can increase the electrostatic field of Nd³⁺ when it was coordinated with SO₄^2-.And finally, it should be noticed that H₂O is a strong ligand.Hence, SO₄^2-/Nd₂O₃/C exhibited a strong Br nsted acidity when H₂O existed in the reaction medium.

Preparation of SiO₂-coated CuFe catalysts for synthesis of higher alcohols from CO hydrogenation

HOU Bin, HAN Xin-you, LIN Ming-gui, FANG Ke-gong

2016, 44(2): 217-224.

[Abstract](109) [FullText HTML] (164) [PDF 5176KB](0)

Abstract:
A series of SiO₂-coated CuFe (SiO₂@CuFe) catalysts with different Cu/Fe molar ratios were prepared by co-reduction and in situ coating method.The physicochemical properties of the catalysts were characterized with XRD, TEM, SEM-EDS, XPS and H₂-TPR techniques and N₂ sorption experiment.It was shown that well-dispersed CuFe nanoparticles were completely coated by mesoporous silica in the as-prepared catalysts.The content of Cu-Fe composite oxide in the catalyst and the selectivity of total alcohols and C₂⁺ alcohols both exhibit a volcano trend with the decrease of Cu/Fe molar ratios.When the Cu/Fe molar ratio was 1, the largest amount of CuFe₂O₄ was formed, consequently, causing the strongest interaction between Cu and Fe.In addition, the obtained catalyst possessed higher BET surface area and larger BJH pore volume than the other samples.Thus, alcohol products easily diffuse into/out of its pores, thus avoiding the further hydrogenation to hydrocarbons.As a result, it shows the highest selectivity to total alcohols and C₂⁺ alcohols.

Probing NH₃-SCR catalytic activity and SO₂ resistance over aqueous-phase synthesized Ce-W@TiO₂ catalyst

LIU Xin, NING Ping, LI Hao, SONG Zhong-xian, WANG Yan-cai, ZHANG Jin-hui, TANG Xiao-su, WANG Ming-zhi, ZHANG Qiu-lin

2016, 44(2): 225-231.

[Abstract](112) [FullText HTML] (170) [PDF 721KB](0)

Abstract:
A series of mixed Ce, W and Ti oxides catalysts have been prepared and employed to selective catalytic reduction of NO with ammonia (NH₃-SCR).It was found that Ce-W@TiO₂ exhibited the optimal catalytic activity.Over 90% of NO conversion could be obtained by the surface TiO₂-coated Ce-W@TiO₂ catalyst at 205-515℃.The presence of SO₂ leads to a decrease of low-temperature NO catalytic conversion and an increase of NO conversion above 425℃ over various catalysts, while Ce-W@TiO₂ exhibits the optimal low-temperature SO₂ resistance.It is noted that introducing Ti into Ce-W mixed oxide via the conventional co-precipitation method attributed to the decrease of surface W atomic abundance and acidic sites as well as inferior low-temperature NO conversion and SO₂ resistance.In contrast, the surface TiO₂-coated Ce-W@TiO₂ catalyst prepared via a modified aqueous-phase method exhibit increased surface W atomic abundance and acidic sites as well as the superior low-temperature NO conversion and SO₂ resistance.

Poisoning effect of SO₂ on Mn-Ce/TiO₂ catalysts for NO reduction by NH₃ at low temperature

YAN Dong-jie, YU Ya, HUANG Xue-min, LIU Shu-jun, LIU Ying-hui

2016, 44(2): 232-238.

[Abstract](141) [FullText HTML] (97) [PDF 2675KB](0)

Abstract:
Effects of SO₂ on performance of Mn-Ce/TiO₂ catalysts were investigated in the selective catalytic reduction of NO with NH₃.The catalysts were characterized by BET surface area, X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), respectively.The results show that SO₂ has inhibitory effect on the selective catalytic reduction (SCR), and NO_x conversion decreases from 84% to 42% at 140℃.This is mainly because the presence of SO₂ results in the decrease of the specific surface area of the catalysis and the pore size distribution of 5-10 nm.SO₂ can cause TiO₂ transformation from anatase to rutile phase, the crystallization phenomenon of active components MnO_x, and the decrease of the strong interaction between Mn and Ti.The variations of physical and chemical properties of poisoned Mn-Ce/TiO₂ catalyst block the O₂^-→O^-→O^2- conversion path, which reduces the proportion of higher catalytic activity component MnO₂ in MnO_x, weakens oxygen storage ability of CeO_x, and accumulates absorbed oxygen on the catalyst surface decreasing the adsorption and desorption of NO on active sites.Ammonium sulfate formed on the catalyst surface covers the Lewis acid sites and decreases the adsorption amount of NH₃.

Pd(OAc)₂ and chloranil-catalyzed oxidation of low-concentration coal mine gases to methanol

XU Feng, LICh uang, JIA Shao-yang, WU Yang, ZHU Li-hua

2016, 44(2): 239-243.

[Abstract](108) [FullText HTML] (50) [PDF 694KB](0)

Abstract:
A self-made experimental system was used to study the catalytic oxidation of low-concentration coal mine gases to methanol in acetic acid solution.With Pd(OAc)₂ as catalyst, addition of p-benzoquinone or chloranil in the reaction system provides a beneficial environment for activation of methane, and chloranil shows a more positive effect.Chloranil amount and reaction temperature and pressure are the key factors influencing the catalytic properties.The target product yield has a positive relationship with these three factors.CH₃OH is formed from the reaction of generated H₂O₂ and CH₄.CH₃COOCH₃ is generated via two routes;one is direct oxidation of Pd²⁺ and CH₄, the other is esterification of CH₃OH and CH₃COOH.

Synthesis and characterization of encapsulated Pt/SOD zeolites

LIU Hong-lei, LIU Fan, XUE Da, LI Fu-xiang

2016, 44(2): 244-250.

[Abstract](172) [FullText HTML] (192) [PDF 10243KB](0)

Abstract:
An advanced hydrogenation catalyst was designed based on the good properties of encapsulated noble metal catalysts, which could be applied in the shape selectivity and hydrogen spillover reactions.Pt, sodalite zeolites and Pt (NH₃)₄Cl₂ were selected as the active components, carriers and metal precursors, respectively.Pt/SOD zeolites encapsulated with different amounts of Pt were hydrothermal synthesized.Then benzene hydrogenation reaction was used as probe reaction to test the catalytic activity of the samples.XRD, SEM, TEM and H₂-TPD were used to characterized the catalysts.The results showed that all Pt/SOD samples had good catalytic activity and excellent hydrogen spillover effect with spillover hydrogen acceptor HZSM-5.When the dosage of Pt (NH₃)₄Cl₂ was 0.063 6 g ((Pt (NH₃)₄Cl₂):(Si-Al gel)=0.030 g/g), the Pt/SOD sample obtained showed the highest catalytic activity for benzene hydrogenation and the benzene conversion was 54.38%.

Adsorptive denitrification of NaY molecular sieve modified by Cr³⁺

HONG Xin, TANG Ke

2016, 44(2): 251-256.

[Abstract](182) [FullText HTML] (131) [PDF 643KB](0)

Abstract:
The modification of NaY by chromium ion was systemically studied.The modified CrY molecular sieve was characterized by X-ray diffraction (XRD), Fourier transform infrared spectrum (FT-IR) and nitrogen adsorption.The experimental results show that the optimum condition of modification are two times modification with 0.5 mol/L Cr³⁺at 40℃.The result of FT-IR suggested the peak disappeared at 1 147 cm^-1 and the peak generated a blue shift at 1 024 cm^-1, indicating that Cr³⁺ had exchanged Na⁺ in the framework of NaY molecular sieve.Static adsorption denitrification of a model fuel on CrY molecular sieve had carried out at different adsorption time and temperature.The results showed that the adsorption of quinoline on CrY molecular sieve was chemical adsorption and the adsorption type was coordination adsorption and π complex adsorption.The adsorption effect was better at room temperature for 30 min.The adsorption of quinoline over CrY molecular sieve belongs to Langmuir adsorption and Freundlich adsorption model.

Submit

Search

Search Type

Author FieldMORE+

Download CenterMORE+

2016 No. 2

NewsMORE+

LinksMORE+