Abstract: The effects of oxygen on changes in char structure and reactivity during steam gasification of Shengli brown coal were examined. A stainless steel simulated entrained-flow reactor was employed to carry out gasification at 800 and 900 ℃ in 8 atmospheres: pure N2, 15% H2O, 25%H2O and 35%H2O balanced with N2; and 1%O2, 15%H2O+1%O2, 25%H2O+1%O2 and 35%H2O+1% O2 balanced with N2. The structure of chars was measured by Raman spectrum, and the intrinsic reactivity of chars with air was measured using a thermogravimetric analyzer (TGA) at low temperature (300 ℃). The results show that the effects of oxygen on char structure are different at high temperature (900 ℃) and low temperature (800 ℃) in brown coal steam gasification. The volatilization of alkali and alkaline earth metallic (AAEM) is strongly influenced by char structure. The presence of O2 during steam gasification has a similar effect on the volatilization of Na to the evolution of structure at different temperatures. Experimental data provided evidence that a mixed H2O/O2 atmosphere could promote a decrease in subsequent char reactivity in air at 300 ℃, and that char reactivity could correlate well with the band area ratio, I(GR+VL+VR)/ID.
Abstract: The entrained-flow coal gasification is an important and attractive technology in large scale coal-based synthetic natural gas (SNG) process. In this study, an integrated entrained-flow coal gasification and pyrolysis system is proposed and investigated. The gasifier is divided into two stages in this system: one is mainly for the gasification of char and the other is mainly for the coal pyrolysis. The integrated system is studied by using a process simulation model and compared with a coal gasification system with the radiant and convective coolers. The effects of the operating conditions on the gasification performance are studied and the optimized operating conditions are obtained. It is found that the optimized steam coal ratio of the integrated system is about 250~300 kg(steam)/t (dry coal) while the gasification temperature is 1 400 ℃. The cold gas efficiency of 88.18% of the integrated system is higher than that of 84.14% of the gasification and radiant+conductive cooler system. The coal and O2 consumptions are relative low in the integrated system. The performance of the integrated system is highly related to the yield of tar and CH4 in the pyrolysis stage. The overall energy conversion efficiency of the integrated system (92.26%) is slightly lower than that of the gasification and radiant+conductive cooler system (93.39%). However, the exergy efficiency is enhanced by more than 2.2% in the integrated system. The integration of the gasification and pyrolysis can effectively recover and promote energy grade of the sensitive heat in the hot syngas.
Abstract: The experiment on co-combustion of pickling sludge and coal was carried out under different temperatures in a high-temperature tubular furnace. The distribution of ten heavy metals (HMs) including As, Cr, Ni, Cd, Cu, Mn, Pb, Zn, Sb and Se in flue gas, fly ash and bottom slag was analyzed. The results indicate that Cd, Se, and Zn are volatile HMs, which predominate in gas phase and fly ash. As to Cd, the maximum proportion in gas phase reaches 61%, while the proportion of Se in flue gas ranges from 38.58% to 94.612%. When the temperature increases, a large amount of Zn is transferred from flue gas to fly ash. As, Cu, Pb, and Sb are semi-volatile HMs. The distribution rate of Pb in bottom slag changes slightly. However, its percentage in flue gas and fly ash swings from 14.176% to 45.79% and from 9.78% to 32.55%, respectively. The peak distribution rate of Sb in flue gas is 37.64%. On the contrary, the temperature increment inhibits the volatilization of As and Cu. This phenomenon is closely relevant to the reaction between As or Cu and some mineral matter. Ni, Cr, and Mn are anti-volatile HMs. The majority of them enrich in bottom slag; in addition, their distributions are insensitive to the temperature change. The enrichment of Cr and Ni in bottom slag is more than 95% and 97%, respectively. The percentage of Mn in bottom slag is boosted from 71.46% to 96.89% as the temperature rises.
Abstract: A series of char samples were derived from pyrolysis of Shenmu coal at low (3 and 5 ℃/min), medium (10 and 15 ℃/min) and fast (50, 100, 225, 350 and 750 ℃/min) heating rates, respectively, and at the same pyrolysis temperature of 750 ℃. Then these chars were characterized by means of X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FT-IR) and thermogravimetric analysis (TGA) with the aim to investigate the influence of heating rate in pyrolysis process on the microcrystallite structure, surface chemistry and gasification reactivity of the derived chars. The results show that with the increase of pyrolysis heating rate, the amount of oxygen-containing functional groups on the surface of the chars decreases, the dimension of microcrystallite lamella La and the graphitizing degree of the char increase obviously, the distance between lamella d002 and mean height of lamella Lc decrease slightly, and the gasification reactivity RT of chars reduces from 0.178 2 to 0.103 6. It can be concluded that the higher heating rate in the process of pyrolysis at 750 ℃ will result in higher graphitization of char with nonpolar surface and low gasification reactivity for Shenmu coal.
Abstract: With toluene as the model compound of tar from biomass gasification, the catalytic properties of olivine and nickel catalysts supported on the olivine were analyzed for its performance on the reactions of toluene cracking and toluene/steam reforming in a fixed bed reactor. The catalysts were characterized by SEM, BET, XRD, and H2-TPR. The results show that calcination changes the physical and chemical characteristics of the raw ore. The olivine catalysts show a catalytic activity on the reactions of catalytic cracking and steam reforming of toluene. However, with the addition of Ni the catalytic activity for toluene cracking reaction decreases, the toluene conversion rate reduces by 2.2%~9.8%; while the catalytic activity for toluene/steam reforming reaction rise obviously, the toluene conversion rate reaches up to 97.0%, and nickel catalyst supported on olivine shows great stability in steam reforming of toluene.
Abstract: The synthesis of methyl formate (MF), dimethoxymethane (DMM) and polyoxymethylene dimethyl ethers (PODEn) from methanol can not only extend the methanol industry chain and digest the large surplus production capacity of methanol, but also bring on enormous benefits in respects of economic development and environmental protection. As a result, it has attracted extensive attention in recent years and great progresses have also been made in the research and development of efficient catalysts and production processes. This paper attempts to make a review on the recent research progresses in the catalytic synthesis of MF, DMM and PODEn from methanol, in the aspects of developing efficient catalysts and exploring the catalytic reaction mechanism. Especially, the review focuses on the selective oxidation of methanol to MF over noble metal catalysts, the selective oxidation of methanol to DMM over vanadium-based catalysts, and the synthesis of PODEn from trioxymethylene (TOM) with methanol or DMM over acidic zeolite catalysts. Lastly, an outlook is given on the possible trends in the development of new efficient catalysts and processes to acquire methanol-down-stream products with high value.
Abstract: The promoting effects of Cu, Ni, Ru and Pt on Fe-based catalysts in Fischer-Tropsch Synthesis were investigated. XRD results indicated that both Cu and Ni can enhance the dispersion of fresh catalysts. XPS results showed that all these metal promoters are enriched on the catalyst surface, whereas four promoters are different in their electronic interaction strength with Fe. H2-TPR results suggested that Cu, Ru and Pt can be reduced at first to corresponding metal species, which can then promote the reduction of Fe2O3 to Fe3O4 significantly; however, the influence of Ni on catalyst reduction is of less significance. CO-TPD results illustrated that the addition of the Cu, Pt and Ni can improve the adsorption of CO on the catalysts. The performances of these catalysts in Fischer-Tropsch synthesis was evaluated in a fixed-bed reactor, which indicated that the activity of CO hydrogenation is enhanced through the addition of these metal promoters; the activity of related catalysts follows the order of Fe3Cu > Fe3Pt > Fe3Ni > Fe3Ru > Fe, whereas the selectivity to CH4 increases in the order of Fe3Ni > Fe3Ru > Fe3Cu > Fe3Pt > Fe.
Abstract: Two shape-defined nano-structured Fe3O4 catalysts such as Nano-Microsphere (FNM) and Nano-Flake (FNF) were prepared by a simple solvothermal method. The effects of precursor type on Fe3O4 crystal morphology was studied. It is found that the rate of nucleation and crystal growth have a crucial influence on the particle morphology. Compared to the traditional Fe catalyst, the shape-defined nano Fe3O4 catalysts could be easily reduced and transferred into active phases, resulting in higher Fischer-Tropsch synthesis (F-T) activity and C5+ selectivity. Especially, the FNM catalyst displayed higher catalytic activity and stability than the FNF catalyst. It was found that the FNF catalyst was more favorable to agglomeration because of shape change of the flakes. In addition, the results indicate that the hydrocarbon selectivity is strongly affected by the particle morphology.
Abstract: The γ-Al2O3 modified with CoAl2O4 by the impregnation method was used as support to prepare cobalt catalysts. The physicochemical properties of the prepared catalysts were characterized with BET, XRD, H2-TPR and XPS techniques and H2-chemisorption experiment. The catalytic properties of the prepared catalysts were investigated for Fischer-Tropsch synthesis. It was shown that CoAl2O4 existed on the surface of γ-Al2O3, and thus, effectively weakening the interaction of Co and Al2O3 and resulting in a great increase in the reduction degree and the catalytic activity. The sample with a CoAl2O4 content of 20% shows the highest catalytic activity. It is worth noting that the CoAl2O4 modification decreased the CH4 selectivity but enhanced the C5+ selectivity and catalytic stability.
Abstract: CuZnAl catalysts were prepared using different sources of copper and zinc through complete liquid-phase technology. The catalytic performances for the ethanol synthesis from syngas were investigated in a slurry phase reactor. The catalysts were characterized by XRD, H2-TPR, NH3-TPD-MS and BET technology. The results suggest that replacing copper nitrate with copper acetate would restrain the reduction of Cu2O in the heat treatment and raise the surface areas of the catalysts. It also provides suitable acid sites and pore sizes for higher ethanol selectivity. The selectivity of total alcohols reaches 45.6% and the ethanol selectivity accounts for 28.7%.
Abstract: The promotional effects of Na+ component in the supported PtSnNa/SUZ-4 catalysts for propane dehydrogenation have been studied by using X-ray diffraction (XRD), H2 chemisorption, NH3 temperature-programmed desorption (NH3-TPD) and H2 temperature-programmed reduction (H2-TPR) combined with microreator tests. It has been shown that Na+ component in the supported PtSnNa/SUZ-4 catalysts can neutralize the strong acidic sites on the surface of SUZ-4 zeolite support, increasing the Pt dispersion and suppressing the cracking of olefin products and the formation of coke, leading to the increases of propene selectivity and catalytic stability. But, excessive Na+ ions in the catalyst decreases the interaction between Sn component and SUZ-4 zeolite support, resulting in the drastic decrease of catalytic activity for propane dehydrogenation.
Abstract: The mechanisms of thiophene conversion over various Y zeolites, viz., HY, Ni-modified NiY and rare earths metal-modified REY, were investigated under catalytic cracking conditions in a fix-bed reactor. The final products of thiophene conversion were analyzed by using a gas chromatography with flame ionization detector (GC-FID), a gas chromatography with sulfur chemiluminescence detector (GC-SCD) and an in situ infrared spectrometer. The results were then correlated with the acidic properties of the zeolites, which indicated that the mechanisms of thiophene interacting with these Y zeolites are dependent on the state and occurrence mode of the modified metallic cation and/or the extraframework aluminum species, which can modulate the Brnsted and Lewis acidities in the zeolites. For the NiY zeolites, the thiophene molecules are mainly adsorbed on the Lewis acidic sites associated with the NiOH+ species; the species of Ni4AlO43+ and those generated from the Ni2+ and the extraframework aluminum can weaken the Brnsted acidity and then reduce the cracking activity of the zeolite. Polymerization and cracking reactions are observed for the conversion of thiophene over the HY and REY zeolites. For the HY zeolites, 2,2',5',2''-terthiophene can be found, which is ascribed to the Brnsted acid sites adjacent to extraframework aluminum species (AlO+ or so on); some subsequent reactions of hydrogen transfer and cracking can also be detected. Over the REY zeolite, hydrogen transfer and cracking reactions of thiophene oligomer species derived on the Brnsted acid sites adjacent to extraframework aluminum species (Al(OH)2+, Al(OH)2+ and so on) can be promoted by the Lewis acid center related to the RE species.
Abstract: A new phosphotungstic acid functionalized carbon nitride (g-C3N4/HPW) was prepared with carbon nitride and phosphotungstic acid as raw materials. The structure of g-C3N4/HPW was characterized by XRD, FT-IR and SEM; with g-C3N4/HPW as a catalyst, the oxidative desulfurization of model oil containing dibenzothiophene (DBT) was carried out by using hydrogen peroxide as oxidant and imidazolium tetrafluoroborate ionic liquid as extractant. The influences of reaction temperature, catalyst amount, extractant amount, H2O2 amount, type of thiophene on the desulfurization efficiency were investigated. The results indicate that under the optimal reaction conditions, viz., 5 mL model oil, 0.02 g g-C3N4/HPW, 1.0 mL H2O2, 1.5 mL BF4, 70 ℃ and reaction time of 120 min, the desulfurization efficiency reaches 93%. Moreover, there is no significant decrease in the desulfurization activity after the catalyst system was recycled for 4 cycles.
Abstract: A series of γ-Fe2O3 catalysts doped with Sn and Ti (γ-Fe0.95Ti0.05Oz, γ-Fe0.95Sn0.05Oz, and γ-Fe0.95Sn0.025Ti0.025Oz) were prepared by the microwave assisted co-precipitation method. The crystal phase, pore structure, surface element distribution and microscopic morphology of the doped γ-Fe2O3 catalysts were characterized by X-ray diffraction (XRD), N2 sorption, energy dispersive spectrometer (EDS) and scanning electron microscope (SEM); the influence of Sn and Ti doping on their activity in the selective catalytic reduction (SCR) of NOx was investigated. The results indicated that Sn and Ti are highly dispersed as amorphous species in crystal lattice of γ-Fe2O3, forming sosoloid with Fe. Through doping with Ti, the γ-Fe0.95Ti0.05Oz catalyst exhibits a high de-NOx efficiency of above 90% at 250~400 ℃, with a maximum of 98.3%; the addition of Ti is effective to reduce the crystallization degree of γ-Fe2O3, improve the pore structure of 2~100 nm, and suppress the formation of α-Fe2O3 phase, which are of benefits to get tiny and uniform discrete γ-Fe2O3 particles with high activity in SCR. However, Sn as an additive may aggravate the sintering and derogate pore structure of 2~6 nm for the γ-Fe0.95Sn0.05Oz catalyst, which is detrimental to SCR. The incorporation of both Sn and Ti leads to a decrease of the surface O/Fe atomic ratio from 1.83 to 1.33; the dramatic decrease of surface lattice oxygen content due to the synergistic effect between Sn and Ti may restrain the SCR activity of γ-Fe0.95Sn0.025Ti0.025Oz.
Abstract: CaSO4 oxygen carriers with silica sol were prepared and their reaction performances with CH4, CO and H2 were experimentally investigated. The formation characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in PVC combustion by means of chemical looping combustion (CLC) based on CaSO4 oxygen carrier and air were studied in a tube furnace system. The results show that CaSO4 oxygen carriers with silica sol can be completely reduced by CH4, CO and H2. The reaction time of CH4 and H2 is much shorter than CO. The chemical looping combustion of PVC can effectively inhibit the formation of PCDD/Fs. The yield and International Toxicity Equivalent Quantity (I-TEQ) of PCDD/Fs produced in CLC are 2 270.9 pg/g and 290.2 pg(I-TEQ)/g, much lower than those in air combustion which are 34 172.5 pg/g and 732.8 pg(I-TEQ)/g. It is mainly because fuel doesn't directly contact with O2 in CLC, the oxidative cleavage of large carbon molecule and the conversion from HCl to Cl2 are significantly reduced which will inhibit the low temperature de novo synthesis and precursors reaction of PCDD/Fs.
Abstract: Perovskite-type metal oxides SrCo0.8Fe0.2O3-δ(SCF182) powder was synthesized by combined EDTA-citrate complexing process. The effects of the pH value of precursor solution on the crystal structure and morphology of synthesized SCF182 powder were investigated by X-ray diffraction and environmental scanning electron microscopy. Fixed-bed experiments were conducted to study the oxygen adsorption/desorption performance of SCF182. The results show that the pH values do not affect the forming of main crystal phase of SCF182 but affect the grain size and microstructure. The net-like porous structure is formed in the system when the pH value of the precursor is 8.The fixed-bed experimental results indicate that the pH value of precursor solution has effects on the oxygen adsorption reaction rate of SCF182. Furthermore, the maximum oxygen desorption amount of SCF182, 42.2 mg/g, can be obtained when the pH value is 8.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
