Abstract: With the discovery of super-huge coalfields located in Xinjiang province, the features of large coal reserves, sodium-rich in coal and the problems of boiler fouling during coal thermal utilization are paid more and more widespread attention. Also, more comprehensive investigation on the characteristics of sodium volatilization and its influencing factors in the combustion can provide an important reference for the efficient and clean utilization of high alkali coal. Therefore, a review was made to collect and analyze the relevant data about sodium volatilization characteristics during high alkali coal combustion from published materials. It is found that the sodium species in most of high alkali coal is dominated by water-soluble sodium (WS-Na), excepting few coals with insoluble sodium (HIS-Na) as main sodium species, e.g. Shenhua Kuanggou coal and Houxia coal. The coal ontaining higher HIS-Na has higher hydrochloride-soluble sodium (AS-Na) and ammonium acetate-soluble sodium (HS-Na) contents. Four influence factors including chlorine content, ash composition and combustion temperature, sodium form and content, which affects the sodium migration and transformation, were compared. It is concluded that the temperature has the greatest influence on sodium volatilization. The volatilization of sodium can be significantly increased with the increase of temperature, and the evaporation rate of sodium will be accelerated after 900 ℃. For the sodium content in 2000-4000 μg/g, there is a well positive correlation between the volatilization amount and the total amount of sodium, but it is irrelevant to the soluble sodium content. Chlorine can promote the volatilization of sodium as the molar ratio of Na to Cl is less than 3.5, while it has an inhibition as the molar ratio of Na to Cl exceeds 10. Moreover, a significant negative correlation is observed between the amount of sodium volatilization and the molar ratio of Na to[(Si+Al)-(Ca+Mg)]. According to the existing research results, the migration and transformation behavior of sodium in coal combustion process is summarized into 3 stages consisting of internal conversion, external volatilization and conversion, as well as condensation, and 4 paths.
Abstract: To explore effect of solvent characteristics on reaction behavior of coal hydroliquefaction intermediate products, coal from Naomaohu in Xinjiang as raw material, tetralin, recycle solvent and decalin as hydrogen-donor solvents, hydroliquefaction experiments were performed in a high-pressure stirred reactor, and change of free radical concentration of asphaltene was analyzed by EPR. The results indicate that asphaltene in tetralin is formed in large quantities and transformed at the same time with increasing reaction temperature, the yield is from 12.92% at 290 ℃ to a maximum of 34.13% at 350 ℃ and then to 15.98% at 430 ℃. The asphaltene yield in recycle solvent continues to rise first, with 31.89% at 290 ℃ and a maximum of 47.96% at 400 ℃, and then decreases to 33.90% due to coking reaction. The change of asphaltene yield in decalin is consistent with that in tetralin. The change of free radical concentration of asphaltene is the same in three solvents, reaching the maximum at 350 ℃, which is 1.778×1018, 2.323×1018 and 1.930×1018/g respectively. On the whole, the values of free radical concentration of asphaltene in recycle solvent are higher than those in tetralin, and that in decalin is between the two solvents. But the g value in tetralin and recycle solvent is between 2.00323 and 2.00403, and the change is consistent with that of COx content in gas products.
Abstract: Two coking coals with high organic sulfur were separated into five fractions with different density ranges by heavy medium separation. The occurrences and transformation of sulfur during pyrolysis of different fractions were investigated by X-ray photoelectron spectroscopy (XPS), solid state 13C nuclear magnetic resonance (13C NMR) and pyrolysis mass spectrometry (Py-MS). The results show that different fractions have significant differences in distribution, occurrence, and chemical environment of sulfur. Organic sulfur is mainly distributed in the low density fraction (D1) and exists in the form of thiophene. Inorganic sulfur such as mineral component is mainly distributed in the high density fraction (D5). As the increase of density of coal fraction, the proportion of aliphatic carbon decreases, and aromatic carbon increases, as well as content of mercaptan and thioether in D1 increases greatly. The volatiles are greatly released since decomposition of aliphatic carbon structure during pyrolysis, which promotes the release of sulfur containing gases, and then improves desulfurization efficiency of D1. However, transformation of sulfur is mainly affected by minerals during D5 pyrolysis.
Abstract: In order to evaluate influence of different compatibilizers on low-temperature performances of direct coal liquefaction residue modified asphalts (DCLR modified asphalt), 3 compatibilizers including silane coupling agent, benzaldehyde and xylene were used. At first, the optimum dosage and mixing mode of the compatibilizers were determined by orthogonal test. Secondly, resistance to low-temperature cracking of the asphalt after adding compatibilizer was evaluated using the Double-Edge-Notched Tension (DENT) test. Finally, dispersion state of DCLR in asphalt were analyzed by scanning electron microscopy and software of Image Pro Plus diagram to quantitatively analyze low-temperature performances of the asphalts after adding compatibilizer. The test results show that addition of compatibilizer is helpful to improve dispersion of DCLR in asphalt and compatibility between them. Thus, the long-term stability of DCLR modified asphalt after adding compatibilizer can be maintained and its low-temperature performances are enhanced. Additionally, the 3 compatibilizers have different effects on low-temperature performances of the DCLR modified asphalt, silane coupling agent is the best, followed by benzaldehyde and xylene.
Abstract: MoO3-SnO2 composite metal oxide catalyst was synthesized by one-step hydrothermal synthesis method without precipitant. The effect of MoOx dispersion state on the catalytic performance of MoO3-SnO2 catalysts with different Mo/Sn molar ratios was investigated for dimethyl ether (DME) low-temperature oxidation to methyl formate (MF). MF selectivity reaches 77.6% with DME conversation of 22.0% over Mo1Sn2 at 150 ℃. The physiochemical properties of these catalysts were characterized by TEM, XRD, Raman, FT-IR, NH3-TPD and H2-TPR. The results showed that the addition of SnO2 into MoO3 affected the crystal structure of catalysts, forming MoOx species with different degree of dispersion on the surface of SnO2. The special architecture of MoOx-SnO2 plays a major role in modifying the acidity and the oxidizability of MoO3-SnO2 catalysts, leading to the obvious differences on catalytic activity.
Abstract: An ordered mesoporous SiC (SiC-OM) material with high specific surface area (345 m2/g) and narrow pore distribution was prepared by a nanocasting method, and a commercial SiC (49 m2/g, SiC-C) was used as a reference carrier. The Ni/SiC-C and Ni/SiC-OM catalysts were prepared by an incipient wetness impregnation method, and tested in the CO2 reforming of CH4(CRM). The textural properties of fresh and used catalysts were characterized by means of ICP, BET, XRD, H2-TPR, XPS, HRTEM, TG, and Raman. The results suggested the average carbon deposition rate over the Ni/SiC-OM decreased one order of magnitude compared with the Ni/SiC-C during 50 h of CRM reaction, due to the strong interaction between Ni species and SiC-OM support and confinement effect of rigid mesoporous skeleton.
Abstract: A series of layered K-Fe-Zn-Ti catalysts with different Zn/Fe molar ratios were prepared by high-temperature solid state reaction and characterized by SEM, TEM, XRD, H2-TPR, CO2-TPD, XPS, N2 sorption and TG measurements; the performance of K-Fe-Zn-Ti catalysts in the hydrogenation of CO2 to light olefins was investigated. The results indicate that the K-Fe-Zn-Ti catalysts have the typical layered structure with K2.3Fe2.3Ti5.7O16 as the main phase. ZnFe2O4 appears on the Zn promoted K-Fe-Zn-Ti catalysts, which may reduce the crystallinity, enhance the surface basicity, and promote the adsorption of CO2. The K-Fe-Zn-Ti catalysts exhibit high selectivity to olefins in CO2 hydrogenation; the ratio of olefins to paraffins in the products (O/P) is higher than 6.5. The addition of Zn can enhance the formation of C5+ hydrocarbons and especially C4+ linear alpha-olefins (LAOs); the content of LAOs in C4+ hydrocarbons over Zn promoted K-Fe-Zn-Ti reaches 75.2%, in comparison with the value of 54.6% over the Zn-free K-Fe-Ti catalyst. In particular, the 0.8K-1.8Fe-0.6Zn-1.3Ti catalyst displays the highest O/P value (7.8), although the effect of Zn content in the Zn-promoted K-Fe-Zn-Ti catalysts on the yield of heavy hydrocarbons and selectivity to alpha-olefins is less significant. Moreover, the K-Fe-Zn-Ti catalysts display high stability in CO2 hydrogenation and the LMO structure remains almost intact after a long term reaction test of 100 h.
Abstract: ZSM-5 zeolites were modified with tartaric acid, oxalic acid and nitric acid. The physicochemical properties of ZSM-5 zeolites, such as crystal structure, acid content, surface area and pore volume, were characterized by XRD, SEM, NH3-TPD, XRF, 27Al MAS NMR, pyridine adsorption infrared spectroscopy and N2 adsorption-desorption isotherms. The catalytic activity of ZSM-5 zeolites were investigated under the condition of reaction temperature 422 ℃ and methanol mass space velocity of 4.74 h-1. The specific surface area, acidity, pore volume and catalytic performance of the catalyst are affected by acid modification. The acid-modified zeolites show good catalytic activity in methanol aromatization (MTA) reaction, and oxalic acid modified catalyst shows higher catalytic activity and selectivity. The yield of aromatic hydrocarbons and BTX reaches 57.40% and 39.40% for reaction time at 8 h, respectively.
Abstract: A series of Pt-FeOx/γ-Al2O3 catalysts were prepared by colloid-deposition method and characterized by XRD, TEM, BET, XPS, H2-TPR and FT-IR to investigate the effects of calcination temperature on the surface structure of Pt-FeOx/γ-Al2O3 catalyst and its catalytic performance in catalytic HCHO oxidation. The characterization results showed that the applied calcination temperature greatly influenced the redox properties and chemical states of the Pt species, as well as the amount of surface hydroxyl groups. All resultant Pt-FeOx/γ-Al2O3 catalysts demonstrated activity in HCHO oxidation. The sample with calcination at 200 ℃ exhibited the best performance, which afforded 100% conversion of HCHO into CO2 and H2O at room temperature. The catalysts with lower calcination temperature should be beneficial to have a better valence distribution of Pt species and produce more accessible interface active sites like Pt-O-Fe species, thus endowing Pt-FeOx/γ-Al2O3 catalyst with relatively high activity for the oxidation of formaldehyde under mild conditions.
Abstract: A series of LaCoO3 catalysts were prepared by sol-gel method and characterized by XRD, BET and XPS; the effect of calcination temperature and content of surfactant PEG-6000 and PEG-20000 on the catalytic activity of LaCoO3 in the selective oxidation of H2S to sulfur was investigated. The results illustrated that adding surfactant PEG-6000 and PEG-20000 can significantly improve the catalytic activity of LaCoO3 in H2S oxidation; the LaCoO3 catalyst prepared by adding 0.30 g PEG-20000 in the solution of 0.02 mol La(NO3)3 + 0.02 mol Co(NO3)2 and calcination at 650 ℃ exhibits the highest activity in H2S oxidation. Over this catalyst and under the optimum reaction temperature of 260 ℃, the conversion of H2S reaches 96.10%, with a selectivity of 93.77% to sulfur.
Abstract: The conversion of carbon monoxide in supercritical water was investigated in a continuous reaction system which could dissolve carbon monoxide in water at high pressure. Meanwhile, due to the diversity of potassium salts in biomass supercritical water gasification, the influence of various alkaline potassium salts (KHCO3, K2CO3 and KOH) on the water gas shift reaction were investigated at 450-600 ℃, 23-29 MPa and with a residence time of 3-6 s. The results show that under non-catalytic conditions, the increases in reaction temperature and residence time both lead to higher CO conversion. The effect of pressure on CO conversion is distinct at low pressure (23-25 MPa), but rather minor at higher pressure (25-29 MPa). The rate expression for the non-catalytic water gas shift reaction is k=103.75×exp(-0.66×105/RT)(s-1). The potassium salts can promote the CO conversion significantly and the activity of three salts follows the order of KHCO3 > K2CO3 > KOH; the conversion of CO is enhanced at higher temperature and longer reaction time, whereas the effect of pressure on CO conversion is much complicated. The catalytic effect of alkaline potassium salts in the CO conversion may be explained by the formation of oxalate (HC2O4-) and formate (HCOO-) intermediates.
Abstract: Using ZnO-TiO2 as a carrier support, Ni/ZnO-TiO2 gasoline desulfurization adsorbents with different Ni contents were prepared by equal volume impregnation method and characterized by X-ray diffraction (XRD), Mercury intrusion porosimetry, H2-temperature-programmed desorption(H2-TPD) and H2-temperature-programmed reduction (H2-TPR). Meanwhile, the desulfurization performance of the Ni/ZnO-TiO2 adsorbents were evaluated using FCC light gasoline in a fixed bed reactor. The results show that proper increase of Ni content has little effect on the specific surface area, internal pore distribution and particle strength of the adsorbent, and can increase the Ni0 species with desulfurization activity and promote the desulfurization activity of the adsorbent. When the content of Ni in the adsorbent is too much, the internal pore distribution of the adsorbent changes, and the specific surface area and particle strength of the adsorbent are greatly reduced, which is extremely detrimental to the desulfurization activity of the adsorbent. When the Ni content is 4.45%, having the best desulfurization performance, can reduce the total sulfur content of 3×10-4 in FCC light gasoline to below 5×10-6, and maintain the desulfurization time up to 152 h, and the breakthrough sulfur capacity is 11.24% (112.4 mg S/g adsorbent). And the olefin content of FCC light gasoline after desulfurization changes little.
Abstract: O2/CaO(001) surface with the lowest energy was built by using the slab model and the first-principles method based on density functional theory. A series of possible adsorption configurations were optimized to get the adsorption geometries with the lowest energy for selenium (Se) and SeO2 on the O2/CaO(001) surface and the conversion of Se to SeO2 on the CaO(001) surface was then investigated. The results indicate that there are two adsorption configurations for Se atom on the O2/CaO(001) surface, viz., O-Se-O and O-O-Se groups; therein the Se terminal in O-O-Se group has a certain chemical activity. The reaction energy barrier for the heterogeneous conversion of Se and O2 to SeO2 is less than that for the homogeneous conversion, which means that CaO can not only act as an adsorbent, but also promote the conversion of Se to SeO2 as a catalyst; certain valence electrons in adsorption substrate are transferred to the orbits of SeO2 molecule when SeO2 molecule was adsorbed on the O2/CaO(001) surface.
Abstract: Chlorine-loaded hierarchical porous bio-char was prepared by co-pyrolysis using nano-CaCO3 as template and rice straw as carbon precursor. The removal of mercury (Hg0) from flue gas by porous materials was studied on a fixed bed test bench with simulated flue gas. The materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption (BET), temperature programmed desorption (Hg-TPD) and X-ray photoelectron spectroscopy (XPS). The results show that HCl impregnation not only removes the products on the template to form porous structures but also effectively loads chlorine onto the surface of the material. The specific surface area and total pore volume of B1C1-Cl2 are 398.1 m2/g and 0.4923 cm3/g, respectively. When the GHSV is 225000 h-1 at 120 ℃, the removal efficiency of Hg0 by chemical adsorption is up to 95%. The porous structure is beneficial to gas diffusion and the high specific surface area can provide more active sites. The covalent groups (C-Cl) participating in the Hg0 removal process are the dominant chemical adsorption sites on the inner micro-mesopore surface.
Abstract: In order to develop a new kind of adsorbent for the storage of natural gas by adsorption, the activated carbon SAC-01 and the layered graphene GS(3D), which have a specific surface area about 2062 m2/g and 1507 m2/g, respectively, were comparatively studied as per adsorption equilibrium data measured at the temperature of 283.15-303.15 K and the pressure of 0-10 MPa. The pore size distribution (PSD) and BET specific surface area of the GS(3D) and the activated carbon were firstly determined by analyzing adsorption isotherms of nitrogen at 77.15 K through Horvath-Kawazoe equation calculation. The Henry law constant was used to calculate the limit isosteric heat of methane adsorption in correspondence with the low surface coverage, the interaction potentials between methane molecule and the surface of two adsorbents were then plotted by employing Virial equation and 10-4-3 potential function. The adsorption data, which were volumetrically measured under high pressures, were correlatively fitted by Langmuirian equations through nonlinear regression. Toth equation with the highest accuracy in predicting adsorption data was then used to calculate the absolute adsorption amount, which was finally employed to calculate the isosteric heat of adsorption via Clausius-Clapeyron equation. The result shows that the limit isosteric heat of methane adsorption on the GS(3D) and the activated carbon is about 23.07 and 20.67 kJ/mol, respectively, and the corresponding interaction potential εsf/k between methane molecule and the GS(3D) or the activated carbon is about 67.19 and 64.23 K at temperature 283.15 K, respectively, which are similar to 64.60 K determined by Lorenz-Berthelot mixing law. The accumulated relative error of the Toth equation for predicting the adsorption equilibrium of methane on the activated carbon and GS(3D) is 0.25% and 2.29%, respectively, and the mean isosteric heat of methane adsorption on the GS(3D) and the activated carbon is about 18.3 and 16.8 kJ/mol, respectively. It suggests that the GS (3D) with a larger specific surface area and micro-pore volume takes more advantages in methane adsorption in comparing with the activated carbon.
Abstract: The ultra-low asphaltene content of Golmud residue (asphaltene content:0.32%) was used as the hydrogenation feedstock. The effect of reaction conditions on the composition properties, colloidal stability parameters (CSP) and coke performance of the hydrogenation reaction samples was investigated. The results show that with the increase in hydrogenation temperature and reaction time, the content of asphaltene and saturated fraction increases, the content of colloid and aromatic fraction as well as the colloid stability parameter decrease, and the coke yield increases continuously. Meanwhile, as the degree of condensation of asphaltenes increases, the aromatic carbon ratio fA increases continuously, the metals and heteroatoms are continuously removed during hydrogenation, V is easier to remove than Ni, and S is easier to remove than N. On the catalyst surface is a carbon-based substance similar to the graphite with ordered structure formed, leading to the continuous reduction in pore structure parameters of the catalyst. When the reaction temperature and time are 420 ℃ and 5 h, respectively, the pore structure damage of the catalyst is the most serious, and a dominant distribution of micropore appears.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
