Abstract: A profound study on the characteristics of pyrolysis and combustion of biomass and the generation and transfer of alkali metals can provide theoretical basis for the clean and efficient utilization of biomass. Due to the low measurement accuracy and time lag, traditional measurement methods have insufficient understanding of the biomass thermal reaction process. Laser induced fluorescence (LIF) technology has the advantages of non-disturbance, real-time in-situ measurement, strong component selectivity, good sensitivity, and high spatial and temporal resolution, which has been used in more and more studies on the biomass thermal reaction processes. This paper mainly reviews the application of LIF technologies in the research on the characteristics of biomass pyrolysis, combustion, and alkali metal release in recent years, analyzes the release and evolution behavior and formation mechanism of volatile matter during biomass pyrolysis under different reaction conditions, and expounds the flame structure information and alkali metal release, migration, and transformation characteristics during biomass combustion. Finally, some shortcomings in the current research and the future research directions are put forward.
Abstract: As the main greenhouse gas, CO2 has a great impact on the global ecosystem. Biochar is considered to be a cost-effective CO2 adsorbent because of its wide sources of raw materials and low preparation cost. However, the original biochar has poor structural characteristics and surface chemical properties, so its physical and chemical properties need to be adjusted. Based on the physicochemical properties of biochar, the preparation and modification methods of biochar were systematically analyzed in this paper. On the basis of previous studies, the mechanism of CO2 adsorption by biochar was summarized. The influence of the changes of pore structure and surface chemical properties of biochar on its CO2 adsorption performance during modification was emphatically expounded. In addition, the possible problems of biochar as CO2 adsorbent in large-scale CO2 capture and the main research directions in the future were also discussed, aiming at providing theoretical basis for the preparation and application of modified biochar CO2 adsorbent.
Abstract: Reducing CO2 into energy fuel is an effective way to alleviate the energy crisis and greenhouse effect. In recent years, domestic and foreign scholar have carried out extensive research on the photo(electro)catalytic reduction of CO2. However, the photo(electro)catalytic reduction of CO2 still has some problems, such as low visible light response, high recombination rate of photo-generated electrons and holes, small CO2 adsorption and poor selectivity of products, which restrict the rapid development of this field. As a new type of green solvent, ionic liquids (ILs) have high thermal stability and strong CO2 adsorption. They can be used as reaction medium or co-catalyst in the photo(electro)catalytic reduction of CO2 chemical reactions, so they have been widely studied. In this paper, the research status and roles of ionic liquids in photo(electro)catalytic reduction of CO2 in recent years are analyzed and reviewed, and the development prospect of ILs in this field is prospected.
Abstract: Ammonia borane (AB) is a promising chemical hydrogen storage material with high hydrogen storage density (19.6%), which can release three molar equivalents of hydrogen through catalytic hydrolysis at room temperature. However, AB releases hydrogen slowly in water, it is necessary to develop highly active metal nanocatalysts to accelerate the process of hydrolysis. This article provides an overview of the synthesis and characterization methods of ammonia borane, the mechanism of hydrolysis and catalytic hydrogen production using the unique dihydrogen key in the ammonia borane structure, and the various factors that affect the hydrogen release performance of AB.
Abstract: The clean conversion of biomass gasification tar is one of the bottlenecks affecting the large-scale application of biomass gasification. Non-catalytic reforming of raw gas can convert the tar components to CO and H2, eliminating the tar while increasing the syngas yield. This paper investigated the kinetic behavior of high-temperature non-catalytic reforming of biomass raw gas on the basis of thermodynamic calculations. The reforming temperature and O2/crude syngas (O/G) ratio are the key factors affecting the reforming process. C2H2 gradually accumulated at the beginning of the reaction as an intermediate product of the conversion of CH4, C2H4 and C6H6. Subsequently, C2H2 converted to CO, ·CH2, ·CH3, and ·C2H3 under the attack of ·O, ·OH, and HCO·. Increasing the reforming temperature can significantly reduce the time required for complete tar conversion. At a reforming temperature of 1300 ℃, O/G ratio 0.16 and a residence time of 1.5 s, the dry base content of the syngas was 81.07% and the conversion of the tar reached 99.60%.
Abstract: Slow co-pyrolysis and fast co-pyrolysis of cellulose (CE) with high density polyethylene (HDPE) were investigated in a tube furnace reactor. The effects of heating rate and mixing ratio on the co-pyrolysis of CE and HDPE were investigated. The results show that slow co-pyrolysis of CE and HDPE can boost liquid yields while lowering gas and char yields. When the ratio of CE to HDPE is 1∶3, the slow co-pyrolysis interaction is strongest. At this ratio, the liquid yield was 95.4%. Compared with the calculated yield, the liquid yield is increased by 9.8%. Rapid co-pyrolysis reduce the liquid yield, but increase the gas yield. When the ratio of CE to HDPE is 3∶1, the rapid co-pyrolysis interaction is strongest. The liquid and gas yields were 49.3% and 42.8%, respectively. Compared with the calculated yields, the liquid yield is reduced by 14.5% but the gas yield is increased by 14.1%. These results verified that the synergistic effect existed during co-pyrolysis of CE and HDPE under the experimental conditions. Co-pyrolysis of CE and HDPE favors reducing the oxygen content of the liquid product and improving the quality of the liquid product.
Abstract: To elucidate the pyrolysis characteristics and Cl release law of domestic dry waste, these organics are divided into polyvinyl chloride (PVC), polymorphic waste, and lignocellulose. The interaction mechanism and chloride release characteristics of PVC with llulose, xylan, and lignin, the three components of lignocellulose, were examined in the co-pyrolysis process. The results show that the PVC and the three components synergize positively in the de-hydrogen chloride stage. The PVC can accelerate the pyrolysis of the three components. Cl is mainly released as HCl, CH3Cl, and chlorobenzene during the co-pyrolysis process. In the co-pyrolysis process of PVC and cellulose, HCl acts as an acidic catalyst to promote the formation of more aromatic hydrocarbons. During the co-pyrolysis of PVC and xylan the acetic acid produced by xylan reduces the starting temperature of HCl release by about 25–30 ℃. Compared with cellulose and xylan, lignin has the greatest inhibitory effect on HCl release. Lignin enhances the chemical bond C–Cl breakage in PVC, reducing HCl but promoting the release of CH3Cl. In short, the three-component promotes the thermal cracking reaction of PVC, reduces the activation energy of the response in the de-hydrogen chloride stage, and produces more chloride. The average activation energies of pyrolysis of PVC with the mixture of three-component are reduced by 25.88%–48.73%, 36.46%–43.73%, and 44.88%–72.83%, respectively.
Abstract: The pyrolysis experiments of penicillin residues at different temperatures (300–700 ℃) were carried out in a fixed bed to study the yield of three-phase products and the morphology and distribution of nitrogen at different pyrolysis temperatures. The mechanism of the pyrolysis reaction of amino acids (aspartic acid, histidine and glutamic acid) contained in the bacterial residues and 2, 5-piperazinedione (DKP) was investigated by ReaxFF molecular dynamics simulations. The results show that the yield of gas increases with the increase of temperature, while the char shows a declining trend. The yield of oil increases to a maximum of 42.3% at 500 ℃ and then decreases as temperature increase. The pattern of nitrogen content in the product with temperature is consistent with the trend of yield. Compared with H2 and hydrocarbon gases, CO2 and CO aere more easily produced at low temperatures. Amides are the main nitrogenous compounds in oil, and the proportion of amides gradually decreases as the pyrolysis temperature increases. The deamination reaction of amino acids is the main source of NH3, and dehydration cyclization occurs between amino acid molecules to produce DKP-like compounds. Gases such as NH3, HCN, HNCO and R-NH, R-NH-R radicals are generated during the pyrolysis of DKP. Nitrogen-containing radicals combine with other radicals or undergo cyclization to form amides, ketones and other compounds present in oil and char.
Abstract: A series of CuxCo3–xAl hydrotalcite-like catalysts with different Cu/Co molar ratios were synthesized by the urea homogeneous precipitation method and used for the direct hydrogenation–hydrogenolysis of furfural to 1,5-pentanediol. The results showed that the Cu/Co molar ratio of the catalyst had a significant effect on its textural properties and catalytic performance. The catalyst exhibited excellent catalytic performance when the molar ratio of Cu/Co was 1∶29 (Cu0.1Co2.9Al), and the conversion of furfural was 100% together with 51.1% yield of pentanediol among which the yield of 1,5-pentanediol was 41.1%, under the reaction condition of 140oC, 4 MPa H2 for 6 h. Extensive characterization techniques, including temperature-programmed reduction (H2-TPR), temperature-programmed desorption (H2-TPD), X-Ray photoelectron spectroscopy (XPS) and Raman confirmed that the excellent catalytic activity of Cu0.1Co2.9Al catalyst was attributed to the highest content of Cu0 and CoOx on its surface, and a synergistic catalytic effect was present between them. Typically, Cu0 was used to adsorb and activate H2, and CoOxwith much oxygen vacancies promoted the adsorption and activation of C=O groups in furfural molecules, leading to the quick conversion of furfural to furfuryl alcohol. In addition, the oxygen vacancies anchored the –OH in the intermediate furfuryl alcohol to produce a C2-terminal oblique adsorption on the catalyst surface. Then it promoted the hydrogenation of C2=C3 with the weakening and cleavage of C2–O1 bond, and enhanced the selectivity of 1,5-pentanediol.
Abstract: The reaction routes for the CO2 hydrogenation to methanol over a series of Cu-Mn-La-Zr catalysts prepared by different methods, viz., CMLZ-CP by co-precipitation, CMLZ-S by sol-gel method and CMLZ-H by hydrothermal method, were comparatively investigated by in-situ DRIFT and H2-TPD characterization. The results indicate that the surface hydroxyl groups on these catalysts contribute to the CO2 hydrogenation to methanol and the reaction may follow the formate (HCOO*) and carboxylate (COOH*) routes. The carboxylate pathway is preferred for the reaction over the CMLZ-CP and CMLZ-H catalysts, whereas the formate pathway dominates in the reaction over the CMLZ-S catalyst. The CMLZ-CP catalyst shows the strongest ability to activate H2 and thus exhibits the highest CO2 conversion and methanol yield. In contrast, the CMLZ-H catalyst has high percentage of medium to strong basic sites and oxygen defects, which favor the hydrogenation of intermediate species to methanol, and thus exhibits the highest selectivity to methanol.
Abstract: In this paper, hydroxyapatite (HAP) with nanorod, nanosheet and nanowire morphologies were synthesized with different surface Ca, O and P distributions. After loading 1.25% of nickel, Ni/HAP-R, Ni/HAP-S and Ni/HAP-W catalysts were obtained and applied for MDR. Among them, the Ni/HAP-R catalyst showed the best performance. The geometric structure, electronic properties and surface basicity of the catalyst were characterized by XRD, N2 sorption, FT-IR, XPS and CO2-TPD. It proved that HAP-R possessed the larges surface area, thus beneficial for Ni dispersion to obtain high MDR activity. Meanwhile, it was rich in Ca-O-P which could accelerate the CO2 activation for coke elimination. TPSR experiments further confirmed that the deep cracking of methane on Ni/HAP-R catalyst was inhibited. However, it could be accelerated in the presence of CO2 to produce CO and H2. In this case, Ni/HAP-R catalyst showed excellent anti-coking performance. This study provides inspiration for the design and synthesis of highly stable heterogeneous catalysts.
Abstract: Compared with traditional combustion, methane catalytic combustion has the advantages of low combustion temperature, clean and high efficiency, and it has good application prospects in natural gas vehicles, solid oxide fuel cell and other fields. In order to reveal the mechanism of dehydrogenation of methane on Pd-Cu clusters with different doping ratios, the density functional theory (DFT) is used to calculate the direct dehydrogenation and O-assisted dehydrogenation of CH4* in different clusters. The calculation results show that the doping of Pd atoms increases the adsorption capacity of Cu(111) surface, and in the process of direct dehydrogenation, the doping of Pd not only reduces the energy barrier from 2.56 to 2.43 eV, but also changes the rate determining step from CH*+*→C* + H* to CH4*+*→CH3* + H*. Pre-adsorbed O can significantly reduce the energy barrier of methane dehydrogenation, and the rate determining steps are CH4* + O*→CH3* + OH*. The highest energy barrier of O-assisted dehydrogenation of CH4* is Cu(111)(1.56 eV)>Pd6Cu(111)(1.44 eV)>Pd2Cu(111)(1.38 eV) on three clusters, which indicates that the addition of Pd has improved the performance of direct dehydrogenation and O-assisted dehydrogenation.
Abstract: The PrxZr1−xO2–δ catalyst with different atom ratio of Pr/Zr was prepared by the sol-gel to catalytic oxidation denitration. Results showed that the efficiency of catalytic oxidation denitration increased initially and decreased afterward with the ratio of Pr atom increased. And the optimum denitration activity could achieve 94.62% at 250 °C when the atom ratio of Pr/Zr was 5∶5. The catalysts were characterized by SEM, N2 adsorption-desorption, XRD, XPS, H2-TPR, and FT-IR. The results illustrated that the catalyst (Pr0.5Zr0.5O2−δ) with the best activity has a “layered” morphology, many pores on the surface, and it has a large specific surface area and pore volume of 77.74 m2/g and 0.66 cm3/g, respectively. Furthermore, the crystalline phase transforms from c-ZrO2 to Pr2Zr2O7 with the increasing of Pr atom. XPS and H2-TPR results showed that the surface chemosorption oxygen and surface Pr4 + oxides increased, and the rising of Pr atom ratio was beneficial to produce oxygen vacancy (Vӧ) site which advantageous to improve the efficiency of catalytic oxidation denitration. FT-IR characterization results indicated that Pr0.5Zr0.5O2−δ solid solution had better NO selectivity, which was conducive to the catalytic oxidation of NO. The anti-SO2 and H2O toxicity experiments showed that Pr/Zr atomic ratio at 5∶5 had better anti-toxicity than other ratios. In addition, using IC to analysis absorption products, the result showed that ${\rm{NO}}^-_2 $ and ${\rm{NO}}^-_3 $ were the main products in the absorption solution.
Abstract: The oxidation of alcohols is a significant chemical reaction, and the efficient oxidation of alcohols over heterogeneous catalysts using oxygen as oxidant has attracted much attention in recent years. Among them, Pd/CeO2 exhibits excellent alcohol oxidation performance. However, the structure-activity relationship between the catalyst’s structure and its catalytic performance for alcohol oxidation is still not clearly understood. This study involved the preparation of CeO2 nanosheets with different concentrations of surface oxygen vacancies (Ov) and their subsequent loading with Pd to explore their catalytic performance for alcohol oxidation. The findings obtained through XPS, Raman, and XAS indicated a positive correlation between the surface Ov concentration of CeO2 as well as the ratio of Pd2+ fraction. The alcohol oxidation results and structure-performance relationship studies showed that there was a good linear relationship between the Pd2+ ratio as well as the surface Ce3+ concentration and the TOF of benzyl alcohol oxidation reaction, respectively. And the interfacial site (Pd–O–Ce) formed by Pd and CeO2 was the main catalytic site for this type of alcohol oxidation catalysts. This study contributes to the understanding of the catalytic role of interfacial sites in metal and oxide support for the development of better alcohol oxidation catalysts.
Abstract: In this paper, CeOx was doped into the catalytic system and cerium-doped carbon nanomaterial was prepared by roasting at high temperature in N2 atmosphere as the carrier. Rh/CeOx-C3N4 catalyst was synthesized by loading the active component Rh onto CeOx-C3N4 carrier through impregnation reduction method, and its influence on catalytic performance of hydrazine hydrate dehydrogenation was investigated. The results showed that there was a synergistic effect between the active component Rh and CeOx in Rh/CeOx-C3N4 catalyst, and the doping of CeOx effectively dispersed and stabilized the metal active component, providing more active sites for catalytic reaction. Therefore, the catalyst has good catalytic activity for the dehydrogenation of hydrazine hydrate. The prepared Rh/CeOx-C3N4 catalyst showed the best catalytic activity for hydrazine hydrate, and the initial conversion TOF was up to 1959.24 h−1. After 5 cycles, the catalytic activity remained good, indicating good durability.
Abstract: Ozone in the indoor environment is seriously harmful to human health, and the catalytic decomposition method is one of the most effective ozone purification technologies. The development of ozone decomposition catalyst with superior activity and stability is the bottleneck, especially under high humidity, high space velocity, and ambient temperature. Layered double hydroxide (LDH) has a unique two-dimensional layered structure and excellent water resistance. In the paper, Ni3Fe, Ni3Co, Ni3Mn, and Co3Fe hydrotalcite-structured catalysts were prepared by the coprecipitation method. And their ozone catalytic decomposition performance was tested under 30 ℃, 600000 mL/(g·h), low humidity (RH< 5%), and high humidity (RH > 90%). The results showed that Ni3Co-LDH exhibited excellent ozone decomposition performance, and the ozone conversion was 88% and 77% under low humidity and high humidity, respectively. Combined with XRD, BET, SEM, XPS, Raman, FT-IR, TG and other characterizations, the intrinsic mechanism of the excellent ozone decomposition performance of LDH catalysts was revealed. The paper provided new ideas for developing transition metal ozone decomposition catalysts.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
