燃料化学学报最新文献

The fluorescence characteristics of coal macerals can be used as one of the indexes to evaluate the properties of coking coal. In this work, a single-wavelength laser with a wavelength of 360 nm was used as the excitation source to excite the surface of particulate block under a polarizing microscope. Effect of excitation time on fluorescence characteristics of the macerals was studied. The relationship between spontaneous fluorescence intensity and the excitation time of each maceral of six kinds of coking coals show that the fluorescence characteristics of coal macerals are related to the type and metamorphism of coal. The excitation time has a certain effect on the fluorescence parameters of the macerals. By comparing the relative fluorescence intensity values under different excitation times, it is found that the mean relative fluorescence intensity within 15 s can be used as an optical parameter to characterize the structure and metamorphic grade of different macerals. The essence of this method is to express movement of electrons in outer layer of nucleus by macroscopic fluorescence spectrum and relative fluorescence intensity of the initial state value and simplify microscopic complexity into macroscopic and numerical form generally accepted.

Highly efficient and environmentally friendly utilization of coal gasification slag is a hot research subject in the coal chemical industry at present. The preparation of activated carbon with a flotation refined carbon from gasification slag, a long flame coal, a high temperature coal tar containing 70% asphalt and an active agent in proper proportion was carried out. The influence of activation temperature and time on the surface properties and compressive strength of the produced activated carbon was investigated in a tube furnace. The oxygen functional group, pore structure and absorption performance of the produced activated carbon were characterized by FT-IR, N₂ adsorption-desorption, SEM and iodine adsorption. The COD removal from biochemical waste water by the produced activated carbon was verified. The results show that the key factors for the effective formation and expansion of pore are the suitable activation temperature and time for the floatation refined carbon from gasification slag as the feedstock. The activated carbon prepared by carbonization at 550 °C for 30 min and steam activation at 950 °C for 2 h exhibits a crisscross morphology of organic carbon components and minerals. The surface area, pore capacity and average pore diameter are 566 m²/g, 0.5611 mL/g and 5.1 nm, respectively, with the characteristics of a concentrated pore distribution and a certain quantity of mesopore. Both iodine value (650 mg/g) and methylene blue value (128 mg/g) meet the requirements of the Chinese standard “Technical Specifications and Test Methods of Activated Carbon for Purification of Industrial Wastewater”. The COD in biochemical waste water treated by the activated carbon for 60 min with a solid-to-liquid ratio of 0.6 g/L can be reduced to lower than 30 mg/L, meeting the B class water quality of the Chinese standard “Integrated Discharge Standard of Water Pollutants” (DB11/307—2013).

In this study, the thermal degradation mechanism of avermectin (AVM) was analyzed via experiments and density functional theory calculations (DFT). The experimental results of AVMD pyrolysis indicated that the removal rate of AVM residues reached peak value of 99.88% above 250 °C. The main product of AVM pyrolysis was alcohols. Based on the C–O bonds breaking, four potential degradation pathways were proposed. The findings of the calculations were in agreement with those of the experiments. These results provide theoretical and empirical guidance for the development of safe antibiotic disposal technology.

An efficient dehydrogenation catalyst is crucial for the application of ammonia borane (NH₃BH₃, AB) as a solid chemical hydrogen storage material. In this work, a kind of nitrogen-doped rice husk activated carbon (N-RHC) was prepared by roasting melamine and rice husk at high temperature under nitrogen atmosphere. With N-RHC as the support, the rice husk-based carbon supported ruthenium catalyst (Ru/N-RHC) was prepared through impregnation with the RuCl₃ solution and its catalytic performance in the hydrolysis of ammonia borane to produce hydrogen was investigated. The results indicate that the Ru/N-RHC catalyst with a Ru loading of 5% performs excellently in the hydrolysis of ammonia borane; the reaction turnover frequency (TOF) reaches 83.71 min⁻¹ and the apparent activation energy decreases from 88.9 to 64.9 kJ/mol under light irradiation. In addition, the hydrogen production rate is positively correlated with the content of ammonia borane and catalyst.

Lignin is a natural and renewable resource with aromatic structure. It can be converted into bio-oil by hydrothermal liquefaction. Due to the complex structure of wood fiber, the structural characteristics and reactivity of different kinds of lignin are different. Therefore, three typical lignin (kraft lignin (KL), enzymatic hydrolysis lignin (EHL) and ethanol lignin (OL)) were selected as raw materials. Firstly, physical and chemical properties of the raw materials were analyzed. Secondly, effects of reaction conditions on characteristics of their hydrothermal liquefaction bio-oil were investigated. Among them, EHL and OL are guaiacyl units. OL has the highest content of carbon and hydrogen elements, and its higher heating value reaches 23.54 MJ/kg. The aromatic characteristics are more obvious, and the phenolic hydroxyl content is relatively high. KL is mainly syringyl unit with less methoxy and phenolic hydroxyl groups. The results of liquefaction experiment show that when the reaction temperature was 300 °C, yield and energy recovery rate of lignin bio-oil were the highest. The bio-oil yield ranked in the order of OL>KL>EHL. H/C ratio of bio-oil was concentrated within 1.0–1.4. Chemical composition of the three bio-oils was different. OL bio-oil contains 9.14% aromatic hydrocarbons, EHL bio-oil contains 41.34% phenolic species, and KL bio-oil has a higher acid content.

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

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

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 °C, 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.

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

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.