Catabolic Pathways Involved in the Anaerobic Degradation of Saturated Hydrocarbons

The nematic twist-bend (NTB) liquid crystal phase possesses a local helical structure with a pitch length of a few nanometres and is the first example of spontaneous symmetry breaking in a fluid system. All known examples of the NTB phase occur in materials whose constituent mesogenic units are aromatic hydrocarbons. It is not clear if this is due to synthetic convenience or a bona fide structural requirement for a material to exhibit this phase of matter. In this work we demonstrate that materials consisting largely of saturated hydrocarbons could also give rise to this mesophase. Furthermore, replacement of 1,4-disubstituted benzene with trans 1,4-cyclohexane or even 1,4-cubane does not especially alter the transition temperatures of the resulting material nor does it appear to impact upon the heliconical tilt angle, suggesting the local structure of the phase is unperturbed. Calculating the probability distribution of bend angles reveals that the choice of isosteric group has little impact on the overall molecular shape, demonstrating the shape-driven nature of the NTB phase.

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Surface charge and extracellular polymer of sludge in the anaerobic degradation process

Water Science & Technology ◽

10.2166/wst.1996.0565 ◽

1996 ◽

Vol 34 (5-6) ◽

pp. 309-316 ◽

Cited By ~ 20

Author(s):

X. S. Jia ◽

Herbert H. P. Fang ◽

H. Furumai

Keyword(s):

Surface Charge ◽

Growth Phase ◽

Anaerobic Degradation ◽

Degradation Process ◽

Anaerobic Sludge ◽

Batch Experiments ◽

High Substrate Concentration ◽

Negative Surface ◽

Negative Surface Charge ◽

Extracellular Polymer

Changes of surface charge and extracellular polymer (ECP) content were investigated in batch experiments for three anaerobic sludges, each of which had been enriched at 35°C and pH 639-7.3 for more than 40 batches using propionate, butyrate and glucose, individually, as the sole substrate. Results showed that both ECP and the negative surface charge were dependent on the growth phase of microorganisms. They increased at the beginning of all batches when the microorganisms were in the prolific-growth phase, having high substrate concentration and food-to-microorganisms ratio. Both later gradually returned to their initial levels when the microorganisms were in the declined-growth phase, as the substrate became depleted. The negative surface charge increased linearly with the total-ECP content in all series with slopes of 0.0187, 0.0212 and 0.0157 meq/mg-total-ECP for sludge degrading propionate, butyrate and glucose, respectively. The change of surface charge for the first two sludges was mainly due to the increase of proteinaceous fraction of ECP; but, for glucose-degrading sludge, that could be due to the increases of both proteinaceous and carbohydrate fractions of ECP. The negative-charged nature of anaerobic sludge implies that cations should be able to promote granulation of anaerobic sludge.

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Production of Fuels and Chemicals from a CO2/H2 Mixture

Reactions ◽

10.3390/reactions1020011 ◽

2020 ◽

Vol 1 (2) ◽

pp. 130-146

Author(s):

Yali Yao ◽

Baraka Celestin Sempuga ◽

Xinying Liu ◽

Diane Hildebrandt

Keyword(s):

Co2 Hydrogenation ◽

Water Gas Shift ◽

Liquid Fuels ◽

Saturated Hydrocarbons ◽

Reverse Water Gas Shift ◽

Cu Catalyst ◽

In Series ◽

Fuels And Chemicals ◽

Water Gas ◽

Aspen Simulation

In order to explore co-production alternatives, a once-through process for CO2 hydrogenation to chemicals and liquid fuels was investigated experimentally. In this approach, two different catalysts were considered; the first was a Cu-based catalyst that hydrogenates CO2 to methanol and CO and the second a Fisher–Tropsch (FT) Co-based catalyst. The two catalysts were loaded into different reactors and were initially operated separately. The experimental results show that: (1) the Cu catalyst was very active in both the methanol synthesis and reverse-water gas shift (R-WGS) reactions and these two reactions were restricted by thermodynamic equilibrium; this was also supported by an Aspen plus simulation of an (equilibrium) Gibbs reactor. The Aspen simulation results also indicated that the reactor can be operated adiabatically under certain conditions, given that the methanol reaction is exothermic and R-WGS is endothermic. (2) the FT catalyst produced mainly CH4 and short chain saturated hydrocarbons when the feed was CO2/H2. When the two reactors were coupled in series and the presence of CO in the tail gas from the first reactor (loaded with Cu catalyst) significantly improves the FT product selectivity toward higher carbon hydrocarbons in the second reactor compared to the standalone FT reactor with only CO2/H2 in the feed.

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