Abstract: Two Chinese coals, Liuzhi (LZ) and Zunyi (ZY), were pyrolyzed in a fixed bed reactor under N2 and H2 atmospheres from 400℃ to 700℃. X-ray Photoelectron Spectroscopy (XPS) was used to study the changes of carbon-containing groups and sulfur transformation on the surface of coals and their chars. Under N2 atmosphere, on the ZY chars surface, the contents of O=C－O, C－H or C－C groups have a decreasing trend and the one of C=O or O－C－O, C－O is increasing compared with that of raw coal at all temperatures. For LZ coal, the changes of O=C－O, C=O or O－C－O, C－O contents are similar to ZY coal, however the one of C－H and C－C content is contrary to that of ZY coal. Under H2 atmosphere, for ZY coal, not only O=C－O content, but also C=O and O－C－O, C－O contents have a decreasing trend, while C－H and C－C contents increase compared with raw coal; for LZ coal, except for C=O and O－C－O content has a decreasing trend, and other carbonyl groups have the same trend as that under N2 atmosphere. And for these coals, with the temperature increasing, the S/C ratio on the char surface increases under N2 atmosphere, however the one decreases at the temperatures from 400℃ to 600℃ and increases much at 700℃ under H2 atmosphere. This indicates that under both atmospheres, sulfur can transfer from inner to the surface during pyrolysis, but hydrogen can react with sulfur-containing radicals, so the S/C is lower than that under nitrogen.
Abstract: Pyrolysis of Huolinhe lignite with solid heat carrier was carried out in a moving bed reactor with the capacity of 10kg/h. The solid heat carrier used in the experiment was the circulating ash from a 75t/h CFB boiler. The effects of pyrolysis temperature, residence time and coal particle size on the yields and composition of products were studied. It is found that the gas yield increases with the increasing pyrolysis temperature. The yield of tar reaches a maximum of 4.94% at 520℃. The heating value of pyrolysis gas is from 19.80MJ/m3 to 23.20MJ/m3. Some useful compounds, such as BTX and PCX, could be obtained from pyrolysis tar and the contents of them are much higher than those from a bituminous pyrolysis tar. Moreover, the pyrolysis char exhibits good combustion characteristic. The sulfur content of pyrolysis char is notably lower than that in raw coal, which benefits to reduce the desulphurization burden of the CFB boiler.
Abstract: Coal catalytic gasification is a very complex process, which was affected by a lot of factors. A prediction model would be helpful for the understanding, design and optimization of such processing. Therefore, a prediction model for the weight loss, the initial temperature of gasification and the temperature of maximum gasification rate during coal catalytic gasification was established by using a three-layer improved Back Propagation (BP) neural network. The model prediction results indicate that the improved BP neural network has a high accuracy. Moreover, the maximum errors between the experimental and the predicted values are 5.18%, 5.65% and 2.33%, respectively, which are much smaller than those predicted by regression equation.
Abstract: The CO2 permeability of Yangquan coal matrix-plug (φ 6×13mm) saturated by CH4 was studied by carrying out CO2 breakthrough tests at 40℃. The similar tests were performed with inert gas He for comparison. The breakthrough tests were performed in a self-confining flow cell equipped with an online thermal conductivity detector for continually monitoring the signal of CO2 or He. The imbibition of gas by coal and the influence of the pore gas pressure were investigated. It shows that unlike He there is significant residual CO2 left in the coal matrix even after CO2 was flushed by CH4 for 36h. It reveals that coal has stronger imbibition ability for CO2, which leads to the difference in its breakthrough time for different CH4 flushing time. No notable residual He is found during the breakthrough tests. He permeability is significantly higher than that of CO2. The obtained permeability coefficients of the coal plug with CO2 or He at the steady state are closely the same for the repeat tests. It implies that no significant structure change involved during the tests. The permeability coefficients varied with the pore gas pressure due to the existence of the influences of the pore wall, the swelling of coal and the adsorption boundary layer.
Abstract: Rice straw (DC), wheat straw (MG) and sawdust (JM) were pyrolyzed in a fixed-bed reactor under argon atmosphere at 10℃/min. The nitrogenous components in the product gases were analyzed by Fourier transform infrared spectrometer (FT-IR). The results show that the releasing temperature of NH3, HCN and NO of JM is apparently higher than that of DC and MG, which is due to the higher content of lignin in JM. DC releases more NH3, HCN and NO than MG and JM during pyrolysis. The NH3 formed at lower temperature is at least partly related to the thermal decomposition of the amino structures. The formation of HCN may occur at a higher temperature. The nitrogen release during the biomass pyrolysis depends on the macromolecular structure, ash content, nitrogen content, and nitrogen distribution among char, tar and gas.
Abstract: Esterification of acetic acid with ethanol under microwave heating was carried out by using three types of solid acid catalysts. The results showed that the activity of these catalysts follows the order of Amberlite resin >SO42-/ZrO2 > HZSM-5. These catalysts are also different in their tolerance to water present in the bio-oil. The catalytic activity of SO42-/ZrO2 decreases obviously with increasing water concentration in the reaction mixture, while Amberlite resin still exhibits a high catalytic activity in the presence of water. After catalytic upgrading of crude bio-oil under microwave heating with the cation exchange resin as the catalyst, most of the organic acids are converted into various esters through esterification with ethanol. Microwave heating is more effective than conventional heating and the components of bio-oil are then better upgraded under microwave heating.
Abstract: Laser Raman spectroscopy (LRS) was used to characterize the NiMoP impregnant with different contents of glycol and citric acid as well as dried Al2O3 impregnated with this NiMoP impregnant. The effect of glycol and citric acid on the structure of active phases in NiMoP impregnant and during the impregnation process was investigated. The results indicated that with glycol as the additive in the NiMoP(0.063) impregnant, the active phases like Hx\[PMo11O39\](7-x)- or Hx\[PMo9O31\](3-x)- and Hx\[PMo12O40\](3-x)- are converted to Hx\[P2Mo5O23\](6-x)- . With citric acid as the additive, Hx\[P2Mo5O23\](6-x)-, Hx\[PMo11O39\](7-x)- or Hx\[PMo9O31\](3-x)- and Hx\[PMo12O40\](3-x)- are present together in the NiMoP(0.063) impregnant; however, citric acid leads a decrease of Hx\[P2Mo5O23\](6-x)- content but an increase of Hx\[PMo12O40\](3-x)-. Compared with glycol, during the impregnation of alumina with the NiMoP impregnant, citric acid is more effective in preventing the active phases from being decomposed in the cavities of alumina.
Abstract: NiAl mixed oxides derived from hydrotalcite-like compounds (HLCs) with Ni/Al atomic ratio of 4.1 were incipiently impregnated by potassium carbonate solution to prepare K-promoted NiAl mixed oxide catalysts with K/Ni atomic ratio in the range of 0.05 to 0.2, and applied in catalytic decomposition of N2O. The catalysts were characterized by ICP-AES, XRD, BET, H2-TPR, XPS techniques, and their catalytic activities for N2O decomposition were tested. The results show that the catalytic activity of NiAl mixed oxide impregnated by K2CO3 solution is much higher than that of NiAl mixed oxide without K species and superior to the catalyst prepared by fresh NiAl-HLC impregnated using K2CO3 solution. The effect of K loadings and calcination temperatures of catalysts on catalytic activity has been investigated. It is found that the catalytic activity of NiAl mixed oxide, especially the one with K/Ni=0.1 and calcinated at 400℃, is largely enhanced by the addition of K species in the presence of oxygen and/or steam. XPS and H2-TPR results show that the electron binding energy of surface active NiO species in K-promoted NiAl mixed oxides shifts to lower value, and the surface Ni－O bond is weakened, thus the reduction peak of surface NiO moves to lower temperature, and the catalytic activity is improved.
Abstract: Cu/HZSM-5 catalysts were prepared by different methods of ion exchange, solid-state dispersion and solid-state microwave irradiation. The obtained Cu/HZSM-5 catalysts were characterized by means of BET, XRD and XPS. Experimental results exhibited that the location of Cu species was strongly dependent on the preparation method. Cu species on the external surface of the zeolite prepared by solid-state microwave irradiation and solid-state dispersion are more than ion exchange. And the crystalline diffraction peaks of CuO species can be found in the samples prepared by solid-state dispersion. In addition, the catalytic performance of the catalyst for NO catalytic decomposition was investigated. Compared with the other two methods, the catalysts prepared by solide-state microwave irradiation showed higher catalytic activity and stability for NO catalytic decomposition. Under anaerobic conditions, the NO conversion was up to 89.2% and could remain at 70%, after 25h. Under the condition of excess oxygen, the deactivation rate of the catalyst was lower than that of the catalysts prepared by ion exchange. Corresponding with the characterization results, we can draw a conclusion that the Cu species, which exist as ion exchange state on the external surface of zeolite, are helpful to the decomposition of NO reaction and its catalytic stability is better.
Abstract: The effects of Na2CO3 addition on the selective non-catalytic reduction (SNCR) using ammonia solution or urea solution were investigated in a quartz tube reactor. The experimental results show that the addition of a little amount of Na2CO3 can improve the NOx reduction efficiency effectively in the low-temperature region, shift the NH3 slip curves to a lower temperature, and reduce the HNCO slip largely in the process of urea-SNCR. Also, the addition of a little amount of Na2CO3 can reduce N2O emission remarkably, especially for the course of urea-SNCR. It is found that the addition of Na2CO3 increases the conversion efficiency of HNCO to NH3 markedly in the thermal decomposition gases of urea, which is the main reason leading to the large reduction of HNCO slip and N2O emission in the process of urea-SNCR. Under the same Na2CO3 addition amount, the promoting effect on NOx reduction efficiency is more evident at lower ammonia-NOx ratio, and the promotion to the width of NOx reduction temperature window is more effective at higher ammonia-NOx ratio, and also the promoting effect on DeNOx efficiency is more obvious at lower oxygen content.
Abstract: Solar photocatalytic water splitting is one of the best ways for solar hydrogen production. In this paper, CdS is chosen as sensitizer to construct a CdS/titanate nanotube composite semiconductor. Both the concentrations and pH conditions of photocatalytic hydrogen production in different organic agents were investigated. The hydrogen production mechanism was analyzed. It was found that formic acid showed highest activity among various organic agents. Various concentrations with 10%, 20%, 30%, 40% and 50% were investigated and the 20% of formic acid showed best activity.
Abstract: ZnO micro particles were prepared by a sol-gel method. Pt-ZnO/C were obtained by electrodepositing Pt. The crystallinity, composition and morphology of the as-prepared powders were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The electrocatalytic activity towards methanol and ethanol oxidation of such micro-composites on a kryptol substrate was investigated in acid electrolyte at room temperature using cyclic voltammetry (CV). The results show that the best catalytic activity of composite catalyst for methanol and ethanol oxidation is obtained when the content of ZnO is 50%.
Abstract: The o-methylation of phenol with DMC to anisole over KBr catalyst was studied by in-situ FT-IR, thermodynamic analysis and reactivity test. FT-IR showed that phenol was activated to generate phenolate over 100℃ while DMC was not activated even at 200℃ by KBr catalyst. Anisole was formed over 150℃ on KBr catalyst as FT-IR and reactivity data revealed. Small amount of carboxymethylation product methyl phenyl carbonate (MPC) was detected and its formation was earlier than that of anisole. Thermodynamic analysis and MPC decomposition experiment showed that the reaction of MPC formation was a parallel and reversible side reaction. Methylation reaction mechanism was thus suggested as phenol was activated by KBr to form phenolate, a strong nucleophilic reagent, which attacked DMC methyl carbon to generate anisole when temperature was higher than 150℃.
Abstract: A series of experiments on the thin-layer drying of paper mill sludge were carried out to investigate the effects of temperature on the drying characteristics of paper mill sludge, and the thin-layer drying model was adopted to simulate the process of sludge drying. The result shows that the higher the temperature of drying and the thinner the layer of drying, the quicker the rate of drying. As the drying temperature rises from 80℃ to 160℃, the maximum drying rate increases from 0.008g/(g·min) to 0.030g/(g·min). Modified page is a model to best describe the drying process of the paper mill sludge in oven. In addition, moisture transfer from paper mill sludge can be described by Fick′s diffusion equation. It is obtained that the effective diffusion coefficient of dried samples of paper mill sludge ranges from 2.2×10-10m2/s to 3.96×10-10m2/s at temperatures from 80℃ to 160℃. By using Arrhenius equation, the activation energy of 9.435kJ/mol for the moisture diffusion is determined.
Abstract: Co-incineration tests of a synthetic house hold waste with sewage sludge were carried out in a lab-scale tubal incinerator and bottom ash and fly ash samples were collected. The sampled ashes were characterized for the concentration and leaching ability of Cu, Pb, Zn, Mn, and Ni. Furthermore, the calculation of thermodynamics equilibrium was conducted to identify the transfer of heavy metal elements into flue gas. The analyses show that the presence of sewage sludge greatly enriches the heavy metal element content in the bottom ash and fly ash in a decreasing order of Zn, Pb, Ni, Mn, and Cu. With the addition of organic Cl, the heavy metals in fly ash are increased, especially for Zn. Meanwhile, the fly ash from the tests with sewage sludge added presents toxicity due to the marked Zn and Pb leaching that exceeds the limit values legislated by National Environmental Law for Hazardous Solid Waste. Discrepancies between model predictions and experimental results are evident, which indicates that considering the kinetics，oxygen content in the incinerator and possible chemical reactions between these heavy metal elements and other elements in the formation of metal chloride gaseous species is needed.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
