Methane yield Dotaz Zobrazit nápovědu
An asymmetric organocatalytic addition of fluorinated phenylsulfonylnitromethane to isatin-derived ketimines was developed. The reaction was efficiently catalyzed by a chiral tertiary amine, cinchonine. This methodology provides a new type of optically active compound with two adjacent quaternary carbon stereocenters in good yield (up to 96%), with moderate diastereoselectivity (up to 5.7 : 1 dr) and excellent enantioselectivity (up to 98/96% ee).
High-solid anaerobic digestion of the very small particle fraction of mechanically-sorted organic fraction of municipal solid waste (OFMSW) was examined in mesophilic digestion tests in a conventional laboratory (0.013 m3) and a pilot (0.300 m3) reactor. The non-biodegradable and recalcitrant molecules together with the low protein and starch contents of the small-particles of OFMSW limited the methane generation potential of substrate. In the conventional AD system, methane yields remained low at 0.139 m3kgVS-1 due to formation of a non-reacting layer on digestate surface, which restricted utilization of the available in OFMSW digestible organics. The absence of surface solid crust in the pilot unit favoured consumption of a greater proportion of volatile solids of the OFMSW. Dry AD was remarkably stable over the entire period and negligibly effected by the toxic H2S yields. Methane generation (0.167 m3kgVS-1) was increased 1.2-fold compared to the conventional system due to a better mixing of substrate and microorganisms achieved inside the pilot reactor, which led to an increase of the digested volatile organics. Digestate presented low stability and high heavy metal content, both of which restrain its implementation as soil conditioner or fertilizer in agriculture. A secondary co-digestion treatment may be required for the neutralization of digestate.
- MeSH
- anaerobióza MeSH
- bioreaktory MeSH
- laboratoře MeSH
- methan MeSH
- odpadky - odstraňování * MeSH
- tuhý odpad * analýza MeSH
- Publikační typ
- časopisecké články MeSH
The study was focused on the assessment of cup-plant (Silphium perfoliatum L.) as a potential feedstock for biogas production in comparison to reference maize related to the balance needs of nutrients and some microelements for their cultivation, especially with use of digestate for fertilization. Field experiments were carried out in areas of the Czech Republic with less favorable conditions for the cultivation of maize. Obtained results confirmed that cup-plant can be considered a promising novel crop for biogas production due to high yields of biomass (12-18 t/ha DM) and methane (3600-4250 Nm3/ha) competing with reference maize grown under the same soil and climatic conditions. The biochemical analyses characterizing the feed value of phytomass were conclusively better with maize than cup-plant. This corresponds with specific methane yields, which is about 5-10% higher in maize (269-319 Nm3/t VS) than in cup-plant (254-298 Nm3/t VS). On the basis of chemical analyses of tested crops, the uptake of basic nutrients (N, P, K, Ca, Mg and S) and selected trace elements (microelements B, Fe, Mn, Co, Cu, Mo, Ni and Zn) was determined. Then, using the element contents and average yields, it was possible to calculate the annual removal of each element from the field with cup-plant and reference maize as the basis value for the evaluation of compensatory fertilization needs. With respect to the cultivation of tested crops for biogas production, the possibilities of their compensatory fertilization were evaluated using digestate from biogas plants. The uptake of different nutrients and microelements on tested crops was verified. The experiment showed that cup-plant has higher requirements on all tested nutrients, except N, and microelements, except Cu and Zn. In the case of nutrients, the highest uptake differences between cup-plant and maize were at B (about 11× higher), followed by Mg (3.5×) and K (1.8×). In the case of microelements, the highest uptake differences were B at (about 9× higher), followed by Co (5×), Fe, and Mn (2×). Therefore, increasing yields of cup-plant after using these nutrients and microelements for compensative fertilizing can be expected. For the mixture of maize and cup-plant (1:1 of VS weight), the higher specific methane yield was obtained (292 Nm3/t VS). It was more than expected of the average value (286 Nm3/t VS). It cannot be explained by the improvement in the feed value of cup-plant and maize mixture, but a possible explanation could be the positive synergistic effect of cup-plant due to the better supply with biologically active essential nutrients and microelements. In any case, this phenomenon deserves more detailed research in the future.
The pretreatment methods for enhancing biogas production from oat straw under study include hot maceration, steam explosion, and pressure shockwaves. The micropore area (9, 55, and 64 m(2) g(-1)) inhibitor formations (0, 15, and 0 mL L(-1)) as well as the overall methane yields (67, 179, and 255 CH4 VS t(-1)) were robustly analyzed. It was confirmed that the operating conditions of the steam explosion must be precisely tailored to the substrate. Furthermore, it was beneficial to prepend the hot maceration before the steam explosion and the pressure shockwaves. The second alternative may give increased methane yields (246 in comparison to 273 CH4 VS t(-1)); however, the application of pressure shockwaves still faces limitations for deployment on a commercial scale.
Relative importance of anharmonic corrections to molecular vibrational energies, nuclear magnetic resonance (NMR) chemical shifts, and J-coupling constants was assessed for a model set of methane derivatives, differently charged alanine forms, and sugar models. Molecular quartic force fields and NMR parameter derivatives were obtained quantum mechanically by a numerical differentiation. In most cases the harmonic vibrational function combined with the property second derivatives provided the largest correction of the equilibrium values, while anharmonic corrections (third and fourth energy derivatives) were found less important. The most computationally expensive off-diagonal quartic energy derivatives involving four different coordinates provided a negligible contribution. The vibrational corrections of NMR shifts were small and yielded a convincing improvement only for very accurate wave function calculations. For the indirect spin-spin coupling constants the averaging significantly improved already the equilibrium values obtained at the density functional theory level. Both first and complete second shielding derivatives were found important for the shift corrections, while for the J-coupling constants the vibrational parts were dominated by the diagonal second derivatives. The vibrational corrections were also applied to some isotopic effects, where the corrected values reasonably well reproduced the experiment, but only if a full second-order expansion of the NMR parameters was included. Contributions of individual vibrational modes for the averaging are discussed. Similar behavior was found for the methane derivatives, and for the larger and polar molecules. The vibrational averaging thus facilitates interpretation of previous experimental results and suggests that it can make future molecular structural studies more reliable. Because of the lengthy numerical differentiation required to compute the NMR parameter derivatives their analytical implementation in future quantum chemistry packages is desirable.
Anaerobic processes for the treatment of plastic materials waste represent versatile and effective approach in environmental protection and solid waste management. In this work, anaerobic biodegradability of model aliphatic polyesters, poly(L-lactic acid) (PLA), and poly(ɛ-caprolactone) (PCL), in the form of powder and melt-pressed films with varying molar mass, was studied. Biogas production was explored in batch laboratory trials at 55 ± 1°C under a nitrogen atmosphere. The inoculum used was thermophilic digested sludge (total solids concentration of 2.9%) from operating digesters at the Central Waste Water Treatment Plant in Prague, Czech Republic. Methanogenic biodegradation of PCLs typically yielded from 54 to 60% of the theoretical biogas yield. The biodegradability of PLAs achieved from 56 to 84% of the theoretical value. High biogas yield (up to 677 mL/g TS) with high methane content (more than 60%), comparable with conventionally processed materials, confirmed the potential of polyester samples for anaerobic treatment in the case of their exploitation in agriculture or as a packaging material in the food industry.
- MeSH
- anaerobióza MeSH
- biopaliva analýza MeSH
- bioreaktory * MeSH
- chemické látky znečišťující vodu chemie metabolismus MeSH
- dusík MeSH
- kyselina mléčná MeSH
- methan metabolismus MeSH
- odpad tekutý - odstraňování metody MeSH
- odpadní vody MeSH
- polyestery chemie metabolismus MeSH
- teoretické modely MeSH
- tuhý odpad analýza MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The main aim of this study was to investigate the impact of a hybrid disintegration process with the use of alkalization and freezing by dry ice on waste activated sludge (WAS) and on the course of the process of mesophilic methane fermentation. In order to achieve the mentioned goal, various analytical techniques were used for assessment of the sludge disintegration and its influence on the further biogas production. As a result of the investigation, it was found that the chemical-thermal process of destruction of WAS results in an increased concentration of organic compounds in the supernatant (expressed as a change in the value of the soluble chemical oxygen demand - SCOD). The use of disintegrated WAS and feeding of the material into the fermentation digester influences, depending on its proportion by volume, the production of biogas and the biogas yield (higher biogas production by ca. 39% in comparison to blank sample was achieved with the appropriately disintegrated sludge). The hybrid process is simple and easy to implement in the full technical scale and does not influence or change the pH value of the sludge feed into the fermentation chambers (the dry ice neutralizes the high pH of the sludge). Additionally, it was determined that the herein developed process, can improve hygienization of the digested sludge.
- MeSH
- anaerobióza MeSH
- biopaliva analýza MeSH
- bioreaktory mikrobiologie MeSH
- čištění vody metody MeSH
- hydrolýza MeSH
- koncentrace vodíkových iontů MeSH
- měření biologické spotřeby kyslíku MeSH
- methan biosyntéza MeSH
- odpad tekutý - odstraňování metody MeSH
- odpadní vody chemie mikrobiologie MeSH
- sanitace metody MeSH
- Publikační typ
- časopisecké články MeSH
A novel magnetic-functionalized-multi-walled carbon nanotubes@chitosan N-heterocyclic carbene-palladium (M-f-MWCNTs@chitosan-NHC-Pd) nanocatalyst is developed in two steps. The first step entails the fabrication of a three-component cross-linking of chitosan utilizing the Debus-Radziszewski imidazole approach. The second step comprised the covalent grafting of prepared cross-linked chitosan to the outer walls of magnetically functionalized MWCNTs (M-f-MWCNTs) followed by introducing PdCl2 to generate the m-f-MWCNTs@cross-linked chitosan with a novel NHC ligand. The repeated units of the amino group in the chitosan polymer chain provide the synthesis of several imidazole units which also increase the number of Pd linkers thus leading to higher catalyst efficiency. The evaluation of catalytic activity was examined in the expeditious synthesis of biaryl compounds using the Suzuki cross-coupling reaction of various aryl halides and aryl boronic acids; ensuing results show the general applicability of nanocatalyst with superior conversion reaction yields, high turnover frequencies (TOFs) and turnover numbers (TON). Meanwhile, nanocatalyst showed admirable potential in reusability tests, being recycled for five runs without losing significant activities under optimum reaction conditions. The successfully synthesis of catalyst and its characterization was confirmed using the Fourier transform infrared spectrometer (FT-IR), spectrometer transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photo-electron spectroscopy (XPS) and thermogravimetric analysis (TGA).
- MeSH
- chitosan chemie MeSH
- imidazoly chemie farmakologie MeSH
- katalýza MeSH
- magnetické jevy * MeSH
- methan analogy a deriváty chemie MeSH
- nanotrubičky uhlíkové chemie MeSH
- palladium chemie MeSH
- spektroskopie infračervená s Fourierovou transformací MeSH
- termogravimetrie MeSH
- Publikační typ
- časopisecké články MeSH
Hybrid disintegration of waste activated sludge (WAS) before the thermophilic anaerobic stabilization of WAS contributes to the intensification of organic compounds decomposition and increases the effectiveness of the anaerobic stabilization process compared to the fermentation of raw WAS. This article investigates the influence of a chemical-thermal pretreatment procedure with the use of NaOH and freezing by the dry ice on WAS. We found that the hybrid pretreatment of WAS causes higher concentration of released organics in the liquid phase (represented here as a change in soluble chemical oxygen demand - SCOD value) in comparison to these disintegration techniques used separately. The use of disintegrated WAS (WASD) as an additional material in the digester chambers impacts (varying on its proportion added), the generation of biogas and its yield. The recorded amount of the produced biogas and biogas yield after 21 days of fermentation increased by 26.6% and 2.7%, respectively (in comparison to blank sample). In addition, it was observed that the hybrid process before anaerobic stabilization contributes to a higher hygienisation of the digested sludge.
- MeSH
- anaerobióza MeSH
- biopaliva analýza MeSH
- Escherichia coli růst a vývoj MeSH
- fermentace * MeSH
- měření biologické spotřeby kyslíku MeSH
- methan analýza MeSH
- odpad tekutý - odstraňování metody MeSH
- odpadní vody * analýza mikrobiologie MeSH
- Salmonella růst a vývoj MeSH
- vysoká teplota MeSH
- Publikační typ
- časopisecké články MeSH
The oxidation reactions of 5-aminopyrimidine derivatives in dimethyl sulphoxide (DMSO) were studied. The DMSO solutions of the studied compounds became deeply coloured within a few hours or days. The oxidation products can undergo further condensation reactions with the starting pyrimidines to yield bipyrimidines and/or pyrimidopteridines. The reaction mechanism of the oxidation-condensation reaction was also supported by reactions of the 5-aminopyrimidines with alloxan (2,4,5,6-tetraoxopyrimidine). DMSO is often used as the solvent in in vitro tests of biological activities, but it is also an oxidising agent and may react with solute molecules and significantly affect the quality of the generated biochemical data.
