Abstract: Compared with ethanol, higher alcohols have the advantages of high cetane number, high energy density, non corrosiveness to engine parts, immiscibility with water, good stability, and other advantages as fuel or fuel additive directly. The conversion of fermentation bioethanol into more valuable higher alcohols has attracted widespread attention. This paper reviewed the research progress of bioethanol to higher alcohols at home and abroad in recent years, including the research and development of metal oxides, hydroxyapatite (HAP) and supported metal catalysts. Finally, the current challenges and future research trends of bioethanol to higher alcohols are summarized and prospected, pointing out that the development of multifunctional catalysts is the focus of future research, and Aldol condensation is an effective strategy to further improve the conversion and selectivity of bioethanol to higher alcohols.
Abstract: Aromatic hydrocarbons, especially monocyclic aromatic hydrocarbons such as benzene, toluene, and xylene (BTX), are important basic raw materials in the chemical industry, which are mainly derived from the catalytic reforming and thermal cracking of fossil fuels. The co-catalytic pyrolysis of biomass and plastic to produce aromatics has the advantages of high efficiency, environmental protection, low cost, and high selectivity. It can solve the problems of pyrolysis products such as high oxygen content, low aromatics yield, and low selectivity, which are caused by the characteristics of biomass rich in oxygen and poor in hydrogen. This article reviewed the research progress of co-catalytic pyrolysis of biomass and plastics to prepare aromatic compounds. Firstly, the types of raw materials for co-catalytic pyrolysis were introduced, and then the co-catalytic pyrolysis catalysts were emphasized. The reaction mechanisms of co-catalytic pyrolysis of biomass and plastics, such as the synthesis of dienes and hydrocarbon pool synergy were summarized. Finally, the future research focus and development direction of co-catalytic pyrolysis of biomass and plastics were proposed, which is developing the highly active and stable modified molecular sieve catalysts in order to improve the aromatics yield.
Abstract: Chemical conversion of greenhouse gas CO2 into value-added oxygenates such as ethanol, acetic acid, propanal, propionic acid, butanol, etc. is challenging due to the complexity of C−C coupling and the uncontrollable bonding. In this review, recent research progresses on the synthesis of multi-carbon oxygenates from CO2 in fixed bed reactor are provided. Firstly, the reaction mechanisms of CO2 hydrogenation are summarized. Then, the potential catalysts applied in one-step or tandem CO2 hydrogenation, dry reforming with light hydrocarbons and hydroformylation were introduced over metal carbides, alkali metal modified single or binary metal catalysts such as Cu, Fe, Co, Rh, etc. The reaction mechanism over different catalysts were further elaborated. Finally, the problems and outlook are discussed.
Abstract: Ammonia is not only the main raw material of nitrogen fertilizer production, but also one of the energy carriers for the storage and conversion process of renewable energy. Therefore, the development of a mild ammonia synthesis technology has become an important research topic in recent years. The chemical looping ammonia synthesis technology decouples the ammonia synthesis reaction into several steps, including the nitrogen fixation and the ammonia release, which has the advantages of easy operation, mild reaction, and low energy consumption. As the key to the chemical looping ammonia synthesis, nitrogen carriers play the role of transferring energy and nitrogen species. However, the current low nitrogen fixation efficiency of nitrogen carriers severely limits the development of the chemical looping ammonia synthesis technology. Therefore, this article reviews the research on the design, preparation and application of nitrogen carriers for the chemical looping ammonia synthesis. Firstly, the design theory of nitrogen carrier is summarized; secondly, the current research status of nitrogen carrier is introduced, with a focus on how to improve the ammonia production rate of nitrogen carrier and the utilization rate of lattice nitrogen; finally, the opportunities and challenges of chemical looping ammonia synthesis technology are discussed, which provide a reference for the design and development of nitrogen carrier in the future.
Abstract: Coal and residuum are first co-pyrolyzed, and then hydrogenated into small molecule products during co-liquefaction. Therefore, clarifying influence of residuum on coal pyrolysis performance is an important thermochemical basis for regulating the process. The co-pyrolysis behavior of atmospheric residuum (AR) and Naomaohu coal (NMH) were investigated by TG, TG-FTIR and distributed activation energy model. The results showed that the peak temperature of the maximum rate of weight loss for the co-pyrolysis process was reduced by 7 °C compared with the theoretical value calculated by weighted average of AR and NMH pyrolysis alone, while the weight loss increased by 3%, the average activation energy decreased by 23.6 kJ/mol. In addition, the peak area of alkyl O-containing functional groups such as alcohols and ethers increased, whereas those of CO and CO2 decreased, suggesting that AR had a positive effect on NMH pyrolysis. Meanwhile, alkyl radicals from AR decomposition would combine with O-containing radicals generated from coal pyrolysis, thus resulting in a decrease of CO and CO2 by inhibiting breakage of carboxyl groups. This work will provide a scientific evaluation basis for revealing the influence of residuum on composition of coal liquefaction product during co-liquefaction.
Abstract: The development of cost-effective and efficient catalysts plays a critical role in the selective hydrodeoxygenation of lignin derivatives for lignin valorization. Herein, we reported “metal-acid” bifunctional catalysts (Ni/Ti-SBA-15) consist of Ni nanoparticles highly dispersed on Ti doped SBA-15, which achieved 100% vanillin conversion and 96.46% selectivity of 2-methoxy-4-methylphenol (MMP) under mild conditions. Characterizations were employed to reveal the morphology and physicochemical properties of the catalysts. The results indicated that doping of Ti species not only increased the number of acidic sites but also promoted the high dispersion of Ni nanoparticles on the support. This research provides a novel concept for the synthesis of cost-effective and efficient catalysts, which contributes to the environmentally friendly and economical conversion of biomass derivatives.
Abstract: Calcium cerium-based catalysts with different Ca:Ce molar ratio prepared by sol-gel method were characterized by XRD, N2 adsorption-desorption, FT-IR, XPS and CO2-TPD, and evaluated the activity for dimethyl carbonate (DMC) synthesis from propylene carbonate (PC) and methanol. The results indicated that more surface oxygen vacancies and more moderate basic sites are beneficial for methanol activation and thus leading to better catalytic activity. The PC conversion was 91.1% with DMC selectivity of 91.72% over 0.9CaCe under the reaction conditions-reaction time of 2 h, reaction temperature of 40 °C, methanol to propylene carbonate molar ratio of 15:1 and catalyst amount of 4% relative to the amount of PC.
Abstract: The costly separation of 1,2-propanediol (1,2-PDO), an unavoidable byproduct in the hydrogenation of dimethyl oxalate (DMO), significantly hampers the economic viability of coal-to-ethylene glycol (EG) technology. To address this challenge, the formation mechanism of the side product 1,2-PDO on the Cu(111) and Cu2O(111) surfaces during DMO hydrogenation was investigated, which focused on the active sites of copper catalyst and the dominant pathway through density functional theory calculation. The thermodynamics of each elementary step and the adsorption behavior of various species involved in the reaction network along with the local density of states and charge density difference were systematically analyzed. The results indicate that 1,2-PDO is generated more favorably on the Cu2O(111) surface than that on the Cu(111) surface, owing to the Lewis acid-base pairs, i.e. ${\rm{Cu}}_{{\rm{us}}}^{+} $ and ${\rm{O}}_{{\rm{suf}}}^- $ sites, present on the Cu2O(111) surface, which strengthens the binding of reactants, products, and reaction intermediates to the substrate. EG reacts primarily with methanol (MeOH) to form 1,2-PDO through Guerbet alcohol condensation reaction through three consecutive steps: alcohol dehydrogenation, aldol condensation, and unsaturated aldehyde hydrogenation. The ${\rm{O}}_{{\rm{suf}}}^- $ sites promote the dehydrogenation of alcohols into aldehydes, the generation of enolates during aldol condensation and the hydrogenation of unsaturated aldehydes, while the ${\rm{Cu}}_{{\rm{us}}}^{+} $ sites are responsible for the C–C coupling reaction. These findings may shed light on the mechanism of 1,2-PDO formation over Cu catalyst and provide fundamental knowledge for the development of more efficient catalysts and process optimization.
Abstract: The MnCu/Ce catalyst with a lower Cu content was prepared by co-impregnation method, and then was characterized by XRD, BET, H2-TPR, XPS and CO2-TPD. The effects of calcination temperature on the structure and properties of the catalyst and the preferential oxidation of CO in a hydrogen-rich atmosphere containing CO2 were investigated. The results indicated that Cu/Mn-O-Ce solid solution was formed in all MnCu/Ce catalysts. Of theses sample, the one calcined at 600 ℃ had strong interaction among Mn, Cu and Ce, formed more ternary oxide solid solution with more oxygen vacancies/Ce3+, and revealed good CO-Prox activity. In addition, it was found that the addition of different percentage of Ar had little effects on the CO-Prox activity of the catalyst, while the space velocity and oxygen excess coefficient had great effects on the catalytic performance, and the presence of CO2 in the reaction feedstock gas had a negative effect on the CO-Prox reaction. At an oxygen excess coefficient of 1.2 and the space velocity of 20266−30400 mL/(g·h), the highest CO conversion rate reached 94.7%.
Abstract: The CuO-NiO/CeO2 catalyst was prepared by step impregnation method. The catalyst was characterized by XRD, BET, H2-TPR, Raman and XPS, and the effects of the calcination temperature of NiO-CeO2 precursor on the physicochemical properties of the catalyst and the selective oxidation of CO in H2/CO2 rich atmosphere were investigated. The results showed that the precursor calcination temperature mainly affected the reduction performance and oxygen vacancy content of the catalyst. When the calcination temperature is 500 ℃, the content of oxygen vacancy in the catalyst is higher, and the catalytic performance is better. When the reaction temperature is 130 ℃, the oxygen excess coefficient is 1.2, and the air speed is 20266 mL/(g·h), the CO conversion rate is 95.9%, and the CO oxidation selectivity is 86.3%.
Abstract: Density functional theory (DFT) calculations were employed to reveal the CH4 partial oxidation mechanism of LaFeO3 oxygen carrier during chemical looping reforming. The CH4 partial oxidation reaction network was constructed by systematically studying the elementary reaction steps, including CH4 adsorption activation, H2 and CO formation, and oxygen diffusion. It was found that CH4 undergoes a gradual dehydrogenation reaction to form H atoms, and the energy barrier (1.50 eV) of CH3 dehydrogenation is the highest, which is the rate-limiting step. There are two possible paths for H2 formation on the surface of oxygen carrier. It is the main route that the H atom from O-top site to Fe-top site bonds with another H atom on O-top site to form H2 molecule. Due to its relatively low energy barrier (1.27 eV), the CO formation process is easier to occur. Oxygen diffusion needs to overcome an energy barrier of 1.35 eV, indicating that it occurs at high temperatures and the diffusion rate is low. By comparing the energy barrier of each elementary reaction, it was found that the H2 formation is the rate-limiting step of CH4 partial oxidation kinetics for LaFeO3 oxygen carrier. The H migration is the key to limiting H2 formation, and accelerating the H migration is the main approach to improve the performance of LaFeO3 oxygen carrier. Based on DFT calculations, the H migration of A/B site doped LaFeO3 oxygen carriers could be studied, which is expected to achieve the rapid screening of potential A/B site effective dopants and guide the design and development of high-performance LaFeO3 oxygen carriers.
Abstract: Lean methane from abandoned coal mines or drainage gas with methane concentration of 1%−3% is in general directly discharged into the atmosphere due to the lack of appropriate technology, which has caused serious environmental concerns due to its high global warming potential. While direct thermal oxidation of ultra-low methane in a flow reversal reactor offers an attractive solution, it poses challenges such as potential explosions and unstable combustion flames. Elucidating the dynamic behavior of thermal oxidation of ultra-low methane in a flow reversal reactor is the basis for practical application. To this end, autothermal operation boundary of a pilot-scale thermal flow reversal reactor was examined and the effects of hot gas withdrawal on the behavior of flow reversal reactor was deeply studied. It was found that autothermal operation can be achieved with a methane content of over 0.2% and heat can be recovered if methane content is over 0.5%. Withdrawal of hot air has a significant impact on the dynamic behavior of the reactor: maximum bed temperature at the pseudo-steady state without hot gas extraction keeps almost constant with methane concentration varying in 0.5%−3.0%; whereas for heat recovery by hot gas withdrawal, the maximum bed temperature increases with the increase of the amount of hot gas extracted, and the allowable hot gas exported from the reactor increases nearly linearly from 12.5% to 32% as the methane content increases from 0.5% to 3.0%. Furthermore, the appropriate switching time decreases with the increase of the amount of hot gas withdrawn; for most cases, reversing flow direction at a time interval of 30−50 s can ensure complete methane conversion and stable bed temperature. Thus, it may be concluded that lean methane (1%−3%) can be mitigated by thermal oxidation without worrying about the bed temperature runaway or explosion.
Abstract: A stable metal-organic framework (MOF), MIL-101(Fe), was successfully synthesised using a solvothermal method and employed as a novel photocatalyst for degrading crude oil in oilfield wastewater. Through optimisation of reaction conditions, the following optimal parameters were determined: a dark reaction time of 30 min, a light reaction time of 30 min, a pH of 5.5, a catalyst amount of 150 mg/L, and a reaction temperature of 303.15 K. Under these reaction conditions, an impressive removal of 94.73% was achieved. This study represents the first application of Fe-based MOFs in the photocatalytic degradation of oilfield wastewater. MIL-101(Fe) notably demonstrated excellent stability under mild acid conditions and can be efficiently recycled. These findings offer valuable insights into using MIL-101(Fe) as a promising material for industrial applications in removing crude oil from oil-polluted water through photocatalytic degradation.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
