Abstract: A series of MnOx modified TiO2 based sorbents were synthesized using wet impregnation method and its performance on elemental mercury (Hg0) removal was studied. The effects of loading amount, calcination temperature, reaction temperature, and flue gas compositions on mercury removal efficiency were investigated. The sorbents were characterized by TGA, N2 adsorption-desorption, XRD, FT-IR, XPS and Hg-TPD. It was shown that the optimum MnOx loading value was 12%, and the optimal calcination and reaction temperature were 450 and 300 ℃, respectively. The highest mercury removal efficiency of MnOx-TiO2 sorbent was 98.46%. O2 and HCl in flue gas played a positive role in mercury removal. SO2 had a strong inhibitory effect on mercury removal, which may be due to the competition adsorption between SO2 and Hg0. At the same time, the manganese sulfate produced during the reaction covered the surface of the active site, resulting in the decrease in mercury removal efficiency. CO2 and NO in flue gas also slightly inhibited mercury removal. Mn4+ participated in oxidizing Hg0 to Hg2+, accompanied with its reduction to Mn3+. The adsorption and oxidation process of Hg0 over MnOx-TiO2 basically conformed to the Mars-Maessen mechanism and Langmuir-Hinshelwood mechanism.
Abstract: The adsorption characteristics of Hg0, HgCl and HgCl2 on the Mo-doped Fe3O4 (111) Fetet surface were investigated by density functional theory (DFT) calculation with the CASTEP software package. The results indicate that both HgCl and HgCl2 are chemically adsorbed on the Mo-doped Fe3O4 (111) Fetet surface, whereas Hg0 is bound to the surface by physisorption. The binding energies of HgCl on the Mo-doped Fe3O4 (111) Fetet surface is about 40%-66% higher than that on the pure Fe3O4 (111) Fetet surface. For the adsorption of HgCl2 molecule on the pure Fe3O4 (111) Fetet surface, two Cl atoms interact with one Mo atom and one Fe atom, forming the "M" structure; in contrast, on the Mo-doped Fe3O4 (111) Fetet surface, the stronger interaction between Cl atom and Mo atom allows a complete dissociation of HgCl2 and release of Hg. The adsorption mechanism of mercury species on the Mo-doped Fe3O4 (111) Fetet surface revealed in this work may be helpful for the practical removal of mercury from coal-fired flue gases.
Abstract: The effects of six factors involving incineration temperature (tc), sludge blending ratio (Xs), O2 concentration(φO2), initial moisture content (φH2O), incineration time (τ) and chlorine content (φCl) on the release properties of semi-volatile heavy metals (SVHMs) (such as Zn, Pb, Cd, Cu, Ni and Cr) in co-incineration of sewage sludge and coal under O2/CO2 atmosphere were investigated in a fixed-bed incinerator based on orthogonal experiment. The results indicate that the influence of six factors on the release fraction of SVHMs is ordered as tc >> Xs > φH2O > φO2 ≈ τ > φCl. The release fraction of Zn is the largest, followed by Pb and Cd, and the release fractions of Cu, Ni and Cr are the least at the same co-incineration condition. Increasing temperature is helpful for SVHMs release, and the promotion at high temperatures of 1000-1100 ℃ on SVHMs release is significantly stronger than that at the low temperature of 700-900 ℃. The release fractions of Zn and Pb increase remarkably from 36.1% and 12.2% to 70.9% and 63.5% with increasing tc from 700 to 1100 ℃, respectively, and the release fraction of Cd achieves the maximum of 40.0% at tc=900 ℃, however, the release fractions of Cu, Ni and Cr mostly keep below 20.0%. The influence of incineration temperature on the heavy metal release fraction is ordered as Pb > Zn > Cd > Cu > Cr > Ni. The release fractions of SVHMs decrease with increasing sludge blending ratio, but present a wave-like trend with increasing initial moisture content. The lower release fraction of SVHMs is achieved at φH2O=0 or 40%. O2 concentration has a certain influence on SVHMs release, and the lowest release fraction of SVHMs is achieved at φO2=30%. The influence of incineration time and chlorin content on the release of Pb is significantly stronger than that of other five SVHMs. The suggested optimal conditions of co-incineration of sludge and coal in O2/CO2 atmosphere are: the incineration temperature is 900-1000 ℃, the sludge blending ratio is about 25%, the O2 concentration is 30%, the initial moisture content is less than 10%, and the incineration time is reduced as far as possible.
Abstract: To explore the De-NOx potential of the semi-coke preheating combustion technique at higher preheating temperatures(>1000 ℃), the effects of preheating temperature(600-1400 ℃), combustion temperature(1200-1400 ℃) and excess air coefficient(α=0.6-1.4) on the NO emission and burnout of semi-coke combustion were studied on a two-stage drop-tube furnace. The results show that higher preheating temperature can reduce both NO emissions and carbon content in fly ash. Besides, under the fuel-rich conditions, the reduction of NO caused by increasing preheating temperature is larger than that under the fuel-lean conditions. When the preheating temperature increases from 800 to 1400 ℃, there is a maximum NO reduction of 74%(α=0.6), which is much higher than that of 20.6%(α=1.4) under fuel-lean conditions. On the contrast, under fuel-rich conditions, the decrease of carbon content in fly ash caused by increasing preheating temperature is smaller than that under fuel-lean conditions. Under fuel-lean conditions, the maximum decrease of fly ash carbon content is 26.8% (α=1.4), which is higher than that of 15.95% (α=0.6) under fuel-rich conditions. About the effect of combustion temperature on the NO emission, it is found that there is a critical excess air coefficient. When the excess air coefficient is higher than the critical value, the NO emissions increase as the combustion temperature increases. However, when the excess air coefficient is lower than the critical value, the trend is opposite.
Abstract: Taking the high moisture-containing sewage sludge (SS), herbal tea waste (HTW) and diatom (DT) as the feedstock, the characteristics of NOx precursors during pyrolysis with or without hydrothermal pretreatment in a horizontal tubular reactor were compared. The formation mechanism of NOx precursors in pyrolysis coupled with hydrothermal pretreatment was also investigated by means of TGA and XPS techniques. The results show that the hydrothermal pretreatment can affect the formation pathways related to NOx precursors at different pyrolysis stages and reduce the release amount of NOx precursor on the whole level. For example, when the pyrolysis temperature is 900 ℃, the NOx precursor yield derived from the hydrothermal treated coke is 55.0% for SS240, 48.1% for HTW240 and 51.2% for DT240, which is 9.5%, 6.0% and 15.4% less than that for SS, HTW and DT untreated sample, respectively. But if calculating based on the amount of N content in feedstock, the released NOx precursor from the hydrothermal treated coke is 90.1%, 41.9% and 59.8% less than that for SS, HTW and DT untreated sample, respectively. The inhibition effect on NH3 formation is higher than that on HCN formation. Meanwhile, two influencing pathways caused by hydrothermal pretreatment were further elaborated, i.e., the removal of N functionalities that leads to a decrease in NH3 on the primary reaction and the stabilization of N functionalities that leads to a decrease in HCN on the secondary reaction.
Abstract: A gilsonite from Qingchuan (Sichuan province, China) was separated into several fractions and characterized by various techniques. The vanadyl porphyrins were determined by inductively coupled plasma optical emission spectrometer, ultraviolet-visible, high-temperature gas chromatography atomic emission detection, and positive-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. The results show that the gilsonite contains a large amount of metal elements, especially the vanadium content is as high as 3888 μg/g. A large number of vanadyl porphyrins are detected, in which the deoxophylloerythroetio porphyrins are the most abundant, indicating high molecular condensation but low thermal maturity. The huge reserves and high metal content imply important utilization value for this natural source.
Abstract: The stability, rheological properties and oil/water interfacial tension of Nano-SiO2/HPAM/NaCl systems at 60 ℃ were studied by Zetasizer, rheometer and spin-drop method, respectively. The results indicated that the zeta potential value of nano-SiO2 became more negative and the particle size was significantly increased with addition of HPAM. Meanwhile, there was no obvious turbidity phenomenon after 10 d. The nano-SiO2/HPAM suspensions had higher viscosity and the viscosity retention was improved in the presence of salt at high temperature and shear rate as compared to HPAM solution. In this work, the nano-SiO2 threshold for 0.18%(mass ratio) HPAM solution was 0.5% (mass ratio). When the mass ratio of nano-SiO2 was less than 0.5%, the viscosity, storage modulus, loss modulus and creeping recovery properties were enhanced as well as the critical strain was decreased with the increase of nano-SiO2 mass fraction. However, the opposite phenomenon was investigated when the mass ratio of nano-SiO2 was more than 0.5%. The reason for this result was that the polymer amounts, polymer conformation onto the nano-SiO2 surface and the network structure between nano-SiO2 and HPAM were different when the nano-SiO2 mass fraction was different. Oil/water interfacial tension values of nano-SiO2/HPAM suspensions were lower than that of HPAM solution, and thus with addition of 0.2% and 0.5% (mass ratio) nano-SiO2, the nano-SiO2/HPAM suspensions had ultimate oil recoveries of 4.5% and 6.0% higher than polymer flooding.
Abstract: In order to study the effect of ZSM-5 on the catalytic pyrolysis characteristic and hydrocarbon selectivity of corn stalk catalytic pyrolysis at different pyrolysis temperatures, the thermogravimetric analysis (TGA) was used to obtain the TG and DTG profiles of corn stalk pyrolysis with and without ZSM-5, and the pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) tests were conducted to analyze the products distribution of corn stalk pyrolysis with and without ZSM-5 at 450, 500, 550, and 600 ℃. The results show that ZSM-5 can decrease the pyrolysis temperature at the highest pyrolysis rate by 23 ℃. Without ZSM-5, both the categories of pyrolysis compounds and the hydrocarbon yield increase with the increase of pyrolysis temperature, and the selectivity of hydrocarbon reaches to the highest value of 11.33% at 600 ℃. However, with ZSM-5, the hydrocarbon yield increases at first and then decreases with the increase of pyrolysis temperature, and the selectivity of hydrocarbon is up to the highest value of 29.24% at 550 ℃. Toluene, indene, naphthalene and 2-methyl-naphthalene are evolved as the main compounds with ZSM-5. And the maximum yields of toluene and naphthalene reach to 4.76% and 3.96%, respectively.
Abstract: Fe(OH)3 and Fe2O3 were first prepared by a precipitation method and then sulfated to obtain the SO42--functionalized SO42-/Fe(OH)3 and SO42-/Fe2O3 catalysts for the selective catalytic reduction of NOx with NH3 (NH3-SCR); the promoting effect of SO42- functionalization on the performance of Fe2O3 catalyst in NH3-SCR was then investigated. The results indicate that the SCR activity of the SO42--functionalized Fe2O3 catalysts is significantly improved in comparison with that of unmodified Fe2O3. In particular, the SO42-/Fe(OH)3 catalyst exhibits excellent performance in NH3-SCR, with the NOx conversion of over 80% at 250-450 ℃; besides, it also display high catalytic stability and resistance towards H2O + SO2. A series of characterization results including XRD, Raman spectroscopy, TG analysis, FT-IR spectroscopy, H2-TPR, NH3-TPD and in situ DRIFTS reveal that the functionalization with sulfuric acid can inhibit the growth of Fe2O3 grains; moreover, SO42- combines with Fe3+ to form the sulfate complex, leading to an increase in the number of surface acid sites and the acid strength, which can inhibit the ammonia over-oxidation on Fe2O3 and enhance the deNOx performance of Fe2O3.
Abstract: A series of ZnxCe2-yZryO4 metal oxides were synthesized by sol gel method, hydrothermal method and co-precipitation method respectively and characterized by XRD, BET, HRTEM, CO-TPD, Raman and XPS. The effects of the synthesis method on the morphology, grain size and oxygen vacancy concentration and the catalytic performance in syngas to low-carbon olefin reaction of the ZnxCe2-yZryO4 catalysts were investigated. The results show that the shape, exposed crystal surface, grain size and surface oxygen vacancy concentration of ZnxCe2-yZryO4 solid solution are strongly dependent on the synthesis method. Under the reaction conditions of 300 ℃ and 1.0 MPa, the dual-functional catalysts of ZnxCe2-yZryO4/SAPO-34 prepared by sol-gel method have the highest low-carbon olefin (C2-4=) selectivity (79.5%), while the selectivities of methane and CO2 are only 5.5% and 10.7%, respectively. Here the direct conversion of syngas to low-carbon olefins are realized at low temperature and pressure and the formation of methane and CO2 is greatly reduced.
Abstract: The reaction mechanism of water-gas shift (WGS) on the Fe3O4 (001)-B surface was systematically studied by using the density functional theory (DFT) calculation with spin polarization. The results show that for the WGS on the Fe3O4 (001)-B surface, three reaction routes including redox, association and regeneration ones coexist, though the redox and association routes may be more important with much lower effective energy barriers. The elementary reaction of H2 formation is influenced by the concentrations of surface H and O defects; higher concentrations of H species and O defects on the catalyst surface are beneficial to the formation of H2. These results should be helpful for a better understanding of the WGS reaction mechanism on the iron-oxygen catalyst.
Abstract: Ni-Co/La2O3 and Ni-Cu/La2O3 bimetallic alloy catalysts were prepared by using LaNi0.9Co0.1O3 and LaNi0.9Cu0.1O3 perovskite-type oxides precursors. The results demonstrate that the components are diluted with each other in the bimetallic alloy catalyst and exhibit strong anti-sintering ability. The carbon deposited on the catalyst surface mainly depends on the adsorption state of CO, the modulated adsorption state and adsorption strength of CO contribute to the strong anti-carbon deposition ability of the Ni-Co bimetallic catalysts. The Ni-Co bimetallic alloy catalysts show remarkable activity, selectivity, and stability in the CO methanation reaction.
Abstract: Cr/Cu-Ce catalyts with different Cr contents were prepared by impregnation method, and their structures, properties and catalytic performance were investigated using N2O titration, H2-TPR and XPS techniques. It is found that the Cr doping changs the specific surface area of copper, the reduction temperature of CuO and oxygen vacancies of the Cu-Ce catalysts. In addition, the catalyst with 3% Cr addition has larger Cu specific surface area, lower CuO reduction temperature and more oxygen vacancies, thus exhibits excellent catalytic performance. The catalytic efficiency reaches 100% and CO volume fraction in outlet gas is 0.15% when the reaction temperature is 533 K, n(water):n(methanol) is 1.2:1 and the feeding rate of methanol and water is 0.072 mL/min. Compared with the un-doped Cr catalyst, the catalytic efficiency increases by 10% and the volume fraction of CO in the outlet gas decreases by 0.34%.
Abstract: A series of mixed TiO2-ZrO2 oxide catalysts used for the dehydration of octadecanol to octadecene were prepared by doping TiO2 in ZrO2 and calcining at 350-500 ℃. With the increase of calcination temperature, the amount of Lewis acid sites on the catalyst surface gradually increases. The amount of Lewis acid sites on the catalyst calcined at 450 ℃ is the most, and when the calcination temperature is over 450 ℃, the amount of Lewis acid sites decreases. No Brønsted acid sites are found on the catalysts. The mixed TiO2-ZrO2 oxides calcined at temperature below 400 ℃ contain Ti-O-Zr bonds and amorphous structure. The mixed TiO2-ZrO2 oxides with calcination temperature above 400 ℃ show monoclinic and tetragonal phases of ZrO2. The crystalline phase of the metal oxides and amount of the acid sites simultaneously affect the performance of the catalysts. The acid sites on the mixed TiO2-ZrO2 oxides with amorphous structure have much higher dehydration activity than those with monoclinic and tetragonal zirconia crystalline phases. The catalyst calcined at 400 ℃ has the highest yield of 1-octadecene.
Abstract: The CuWO4/SBA-15 catalyst was prepared with CuWO4 as the active composite and mesoporous SBA-15 molecular sieve as the support and characterized by XRD, N2 adsorption and desorption, FT-IR, UV-vis, SEM, EDS and TEM; the performance of CuWO4/SBA-15 catalyst in the photocatalytic oxidation desulfurization (PODS) was investigated by using the dodecane solution of dibenzothiophene (DBT) as the model fuel. The results show that the CuWO4/SBA-15 catalyst can maintain the two-dimensional hexagonal mesoporous structure of the support and the active component is evenly distributed on the support; the surface area, pore size and pore volume of the CuWO4/SBA-15 catalyst decrease with an increase in the amount of active component. Compared with CuWO4, the CuWO4/SBA-15 catalyst displays a blue shift in absorption boundary of UV-vis spectra and an increase of the band gap. With a CuWO4/SiO2 mass ratio of 0.07, catalyst mass percentage of 3% in the model fuel, O/S molar ratio of 10:1, and extractant/oil volume ratio of 1:1, the desulfurization rate reaches 81.5% by carrying out the PODS reaction under light for 100 min, which is obviously higher than that over CuWO4; moreover, no obvious decrease of catalytic activity for CuWO4/SBA-15 was observed after 6 runs of PODS. It is proposed that ·OH and h+ are the main reactive intermediates in PODS.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
