Influence of coalification on methane diffusion dynamics in middle-high rank coals

Understanding the effect of coalification on the diffusion of methane in middle-high rank coals (MHRC) is fundamental for optimizing the coalbed methane (CBM) drainage strategies. Safe coal mining relies critically on this approach. Hence, CH4 adsorption/desorption experiments and a new methane diffusion model were used to study methane diffusion behavior in five different metamorphic degree coals from China. The results indicate that, as the vitrinite reflectance (Ro) increase, the Langmuir volume (VL) shows a downward trend at first, then increases. Coalification especially for the third coalification jump (Ro = 1.26%) shows a turning effect on diffusion dynamics of MHRC. The desorption volume and initial diffusion coefficient (D0) both show a slight decreasing, then rapid increasing trend. The D0 of five coals jumps at Ro = 1.26%. VL increases alongside that of the micropores volume. With the decrease of the Raman parameter ID1/IG, the VL, methane desorption volume within 7200 s and D0 all increase. Results show that coalification changes the microporous structure and the macromolecular structure of the coal, which finally affects the diffusion capacity of coal. Coalification has a positive effect for the gas extraction and the development of CBM for the semianthracites

Impact of non-minimum-phase zeros on the weak-grid-tied VSC

Right-half-plain (RHP) zeros can significantly deteriorate a control system’s dynamic performances as it exhibits non-minimum-phase behaviors. In this paper, we investigate the occurrence mechanism of RHP zeros in weak-grid-tied VSCs as well as provide guidance for minimizing their effects. A reduced order multi-input multi-output (MIMO) transfer function of the weak-grid-tied VSC is firstly obtained. Then, the single-input single-output (SISO) transfer function to study the impact of the RHP zeros on the power response is further derived. The existence of RHP zeros is examined by applying the Routh criterion on the numerator of the SISO open-loop transfer function. We find that RHP zeros can exist either when the VSC works as an inverter or a rectifier. Furthermore, large grid impedance values as well as operation points with high active power values can result in a non-minimum-phase system. It is also shown that RHP zeros limit the minimum PLL bandwidth. Simulation results and RTDS experiments validate the correctness of the analysis and the conclusions obtained

Aperçu de la valorisation des composés à base de biomasse en batch versus flux continu

Furfural (FF) and 5-hydroxymethylfurfural (HMF) have been identified as important bio-based versatile chemicals, their oxidation, reduction, hydrolysis and polymerization products attracted more interests for the high value and Wide applications. The aim of this PhD work is to realize the conversion of FF and HMF into high value downstream products in both conventional and intensification processes. Therefore, the comparation between conventional heating and microwave heating method, batch With continuous flow regime was explored regarding FF derivatives and HMF valorization reaction in my work. The development of greener, durable and efficient catalysts to realize the conversion of bio-based compounds has been employed. Target compounds such as methyl levulinate (ML), gamma-valerolactone (GVL), 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), 2,5-furandicarboxylic acid (FDCA) were investigated. At the same time, the application of FDCA was also performed, the production of three differen kinds of furan-based polyesters: polyethylene-2,5-furandicarboxylate (PEF), polyhydropropyl-2,5furandicarboxylate (PHPF) and polydiglycerol-2,5-furandicarboxylate (PDGF) were realized through polytransesterification between diethyl furan-2,5-dicarboxylate (DEFDC) and a defined diol furan-based prepolyme or pure diglycerol. Several important issues were identified in order to design processes greener than the current ones. For instance, the experiments for HMF oxidation were performed in water. Microwave irradiation has been chosen as the heating method to accelerate the reaction. Continuous flow reactors, such as Pheonix, H-cube Pro as well as microwave continuous flow were identified as interesting alternatives to improve the productivities of target compounds. As a result, some promising results were obtained in the viewpoint of industry.Le furfural (FF) et le 5-hydroxyméthylfurfural (HMF) ont été identifiés comme d'importants produits chimiques polyvalents d'origine biologique. Leurs produits d'oxydation, de réduction, d'hydrolyse et de polymérisation ont suscité un grand intérêt pour leur haute valeur ajoutée et leurs vastes applications. L'objectif de ce travail de doctorat est de réaliser la conversion du FF et du HMF en produits de haute valeur en aval dans des procédés conventionnels et d'intensification. La comparaison entre le chauffage conventionnel et la méthode de chauffage par micro-ondes, par lots avec un régime d'écoulement continu a été explorée en ce qui concerne les dérivés des FF et la réaction de valorisation du HMF. Le développement de catalyseurs plus écologiques, durables et efficaces pour réaliser la conversion des composés d'origine biologique a été étudié. Des composés cibles tels que le lévulinate de méthyle (ML), la gamma-valérolactone (GVL), l'acide 5-hydroxyméthyl-2-furancarboxylique (HMFCA), l'acide 2,5-furandicarboxylique (FDCA) ont été étudiés. En même temps, l'application du FDCA a également été effectuée, la production de trois différents types de polyesters à base de furanne : le polyéthylène-2,5-furandicarboxylate (PEF), le polyhydropropyl-2,5-furandicarboxylate (PHPF) et le polydiglycérol-2,5-furandicarboxylate (PDGF) ont été réalisés par polytransestérification entre le diéthyl furane-2,5-dicarboxylate (DEFDC) et un prépolymère défini à base de diol-furanne ou de diglycérol pur. Plusieurs questions importantes ont été soulevées afin de concevoir des processus plus écologiques que les processus actuels. Par exemple, les expériences pour l'oxydation du HMF ont été réalisées dans l'eau. L'irradiation par micro-ondes a été choisie comme méthode de chauffage pour accélérer la réaction. Les réacteurs à flux continu, tels que Pheonix, H-cube Pro ainsi que les micro-ondes à flux continu ont été identifiés comme des alternatives intéressantes pour améliorer la productivité des composés cibles. En conséquence, des résultats prometteurs ont été obtenus du point de vue de l'industrie

One-Pot FDCA Diester Synthesis from Mucic Acid and Their Solvent-Free Regioselective Polytransesterification for Production of Glycerol-Based Furanic Polyesters

International audienceA one pot-two step procedure for the synthesis of diethyl furan-2,5-dicarboxylate (DEFDC) starting from mucic acid without isolation of the intermediate furan dicarboxylic acid (FDCA) was studied. Then, the production of three different kinds of furan-based polyesters-polyethylene-2,5-furan dicarboxylate (PEF), polyhydropropyl-2,5-furan dicarboxylate(PHPF) and polydiglycerol-2,5-furandicarboxylate (PDGF)-was realized through a Co(Ac) 2 ·4H 2 O catalyzed polytransesterification performed at 160 • C between DEFDC and a defined diol furan-based prepolymer or pure diglycerol. In parallel to polymerization process, an unattended regioselective 1-OH acylation of glycerol by direct microwave-heated FDCA diester transesterification led to the formation of a symmetric prepolymer ready for further polymerization and clearly identified by 2D NMR sequences. Furthermore, the synthesis of a more soluble and hydrophilic diglycerol-based furanic polyester was also achieved. The resulting biobased polymers were characterized by NMR, FT-IR spectroscopy, DSC, TGA and XRD. The morphologies of the resulted polymers were observed by FE-SEM and the purity of the material by EDX

Development of a chemical kinetic mechanism for ammonia/macromolecular hydrocarbon combustion

C-free fuel ammonia has a high auto-ignition temperature and low flame speed compared to conventional hydrocarbon fuels, which limits its application in internal combustion engines (ICEs). Blending ammonia (NH3) with a highly reactive fuel can effectively solve this problem, and traditional macromolecular hydrocarbon fuels are a good choice because of their practicality and economy. However, the chemical reaction mechanism for the combustion of NH3/macromolecular hydrocarbons is not yet fully understood. In this study, a detailed kinetic mechanism for NH3 and toluene reference fuel (TRF) is proposed with 250 species and 4272 reactions. The developed NH3/TRF mechanism was validated by a single component (NH3, n-heptane, iso-octane, and toluene) and multiple components (NH3/n-heptane, NH3/iso-octane, NH3/toluene) with ignition delay time, laminar burning velocity, and key intermediate component distribution. The current NH3/TRF mechanism showed good performance compared with previous mechanisms. The co-combustion of NH3/TRF blends was performed with different NH3 energy fractions, and sensitivity and reaction pathway analyses were performed to reveal the effect of TRF addition on NH3 combustion. The results showed that the OH radical is mainly produced through N-containing reactions rather than C-containing reactions under T = 1000 K, P = 40 atm, and ϕ = 1 with more than 30 % NH3 addition. The HO2 radical is the most important radical for NH3 ignition, in addition to OH radicals, and its reactions with N-containing radicals (NH2, H2NO, and NO) contribute to the majority of OH radicals

Recent Advances in Catalytic Hydrogenation of Furfural

International audienceFurfural has been considered as one of the most promising platform molecules directly derived from biomass. The hydrogenation of furfural is one of the most versatile reactions to upgrade furanic components to biofuels. For instance, it can lead to plenty of downstream products, such as (tetrahydro)furfuryl alcohol, 2-methyl(tetrahydro)furan, lactones, levulinates, cyclopentanone(l), or diols, etc. The aim of this review is to discuss recent advances in the catalytic hydrogenation of furfural towards (tetrahydro)furfuryl alcohol and 2-methyl(tetrahydro)furan in terms of different non-noble metal and noble metal catalytic systems. Reaction mechanisms that are related to the different catalytic materials and reaction conditions are properly discussed. Selective hydrogenation of furfural could be modified not only by varying the types of catalyst (nature of metal, support, and preparation method) and reaction conditions, but also by altering the reaction regime, namely from batch to continuous flow. In any case, furfural catalytic hydrogenation is an open research line, which represents an attractive option for biomass valorization towards valuable chemicals and fuels

Continuous Flow Conversion of Biomass-Derived Methyl Levulinate into γ-Valerolactone Using Functional Metal Organic Frameworks

Zirconium based metal organic framework, UiO-66 (Zr), was successfully synthesized via solvothermal method, followed by various characterization including XRD, thermal analysis, N2 physisorption and TEM. As-synthesized UiO-66 (Zr) was employed in the transformation of methyl levulinate (ML) to gamma valerolactone (GVL) via catalytic transfer hydrogenation (CTH) under continuous flow and various reaction conditions, which gave superior catalytic performance and efficiency as compared to reported catalysts. The obtained results show great potential of applying UiO-66 (Zr) in upgrading biomass derivatives to useful biofuel/chemical products, paving the way for green energy production from renewable resources

Synthesis of the Marine Bromotyrosine Psammaplin F and Crystal Structure of a Psammaplin A Analogue

Psammaplin F, an unsymmetrical disulfide bromotyrosine, was isolated from the sponge Pseudoceratina purpurea in 2003. We reported here the first total synthesis of psammaplin F in 12% overall yield by employing Cleland’s reagent reduction as key step. The longest linear synthetic sequence starting from 3-bromo-4-hydroxybenzaldehyde and hydantoin was seven steps. In addition, a detailed X-ray crystal structure analysis of psammaplin A analogue 8b is given for the first time

Crop Productivity, Economic Advantage, and Photosynthetic Characteristics in a Corn-Peanut Intercropping System

Corn-peanut intercropping is an important element of China’s agricultural planting model as it confers ecological benefits and increases yield. The aim of this study was to explore the productivity differences between intercropping and monoculture by using the 13C isotope tracer labelling method. Corn hybrid Denghai 618 (DH618) and peanut variety Huayu 22 (HY22) were used as test materials under three planting methods, single corn, SM; single peanut, SP; and corn-peanut intercropping, IM and IP, respectively, during two growing seasons. The results showed that IM increased yield by 59.7% and 62.3% compared with SM, respectively. IP reduced yield by 31.3% and 32.3% compared with SP, respectively. IM significantly increased the photosynthetic rate, leaf area, 13C assimilation distribution, and dry matter accumulation of summer corn, which led to an increase in the kernel number and grain yield. The decrease in intercropped peanut yield was mainly caused by a decrease in the full-pod rate and number of pods per plant. The decrease in peanut yield did not affect the production of intercropping benefit due to the larger intercropping advantage and land equivalence ratio. Corn-peanut intercropping yielded greater economic benefits than monoculture. These results showed the utility of the peanut-corn intercropping model