Multifunctional Amphiphobic Coating toward Ultralow Interfacial Adhesion of Hydrates.

Hydrate adhesion is a challenging issue in some practical applications. However, most current anti-hydrate coatings fail to maintain their properties when subject to crude oil and corrosive contaminants. In addition, the effect of surface properties on the nucleation of hydrates is still unexplored from a microscopic perspective. In this study, a multifunctional amphiphobic PF/ZSM-5 coating consisting of 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane modified ZSM-5 zeolite (F/ZSM-5) and adhesive polyethersulfone was fabricated by the spraying method. The interfacial nucleation and adhesion of hydrates on substrates were studied from a microscopic perspective. The coating exhibited excellent repellencies to various liquids, including water, edible oil, liquid paraffin, vacuum pump oil, n-hexadecane, and crude oil. The tetrabutylammonium bromide (TBAB) hydrate is readily nucleated on the bare Cu surface. In contrast, the coated substrate effectively inhibited the hydrate nucleation on the surface and even reduced the adhesion force to 0 mN/m. Furthermore, this coating was fouling- and corrosion-resistant and can maintain an ultralow hydrate adhesion force even after immersion in crude oil or TBAB solution for 20 and 300 d, respectively. The durable anti-hydrate performance of the coating was attributed mainly to the unique architecture and excellent amphiphobic properties enabling stable air cushions between the solid-liquid interface.

Interfacial Adhesion Forces of Hydrate Particles in the Presence of Hydrate Inhibitors.

Hydrate inhibitors are traditionally utilized to prevent hydrate plugging. In this study, the adhesion forces of cyclopentane (CP) hydrates with thermodynamic inhibitors (ethanol, urea, and NaCl) and anti-agglomerant inhibitors [sorbitan monooleate (Span 80) and lecithin] were measured to understand the effects of hydrate inhibitors on the adhesion forces of hydrates. It was found that the thermodynamic inhibitors increased the early hydrate interparticle adhesion force due to the enhanced liquid bridge force. However, the liquid bridge acted as a lubricant layer to prevent the irreversible agglomeration of hydrate after long-term contact. The hydrate adhesion forces decreased by 90.5-93.0% and 76.6-92.7% with an increase in the concentration of Span 80 and lecithin, respectively, from 0.1 to 1 wt %. Both rough morphology and low interfacial tension contributed to the adhesion force decrease of hydrate after the addition of anti-agglomerant inhibitors. The results may be helpful for understanding the mechanism of influence and quantifying the impact of hydrate inhibitors on hydrate interparticle adhesion force.

A Method for Seawater Desalination via Squeezing Ionic Hydrogels.

In this study, mechanical force applied to squeeze poly(sodium acrylate-co-2-hydroxyethyl methacrylate) hydrogels that contained seawater in order to obtain fresh water. By incorporating ionic monomer sodium acrylate (SA) into hydrogels, the salt rejection was significantly enhanced from 27.62% to 64.57% (feed concentration 35.00g/L NaCl solution). As SA's concentration continuously increased, salt rejection declined due to the change in hydrogel's matrix structure. Therefore, water recovery raised as the current swelling degree increased. We also measured pore size distribution by applying mercury intrusion porosimetry on each hydrogel sample in the interest of finding out whether the sample SA5/HEMA15 owned multi pore structure, since the result could be good for the desalination performance. After 4 times reused, the hydrogel remained good desalination performance. Although compared to reverse osmosis (RO) and multistage flash distillation (MSF) & multiple effect distillation (MED) the salt rejection of this hydrogel (roughly 64%) seemed low, the hydrogels can be used for forward osmosis and reverse osmosis, as pretreatment of seawater to reduce the energy consumption for the downstream.

Analysis of flow field characteristics of sand removal hydrocyclone applicable to solid fluidization exploitation of natural gas hydrate.

With the development of economy and society, the consumption of fossil energy is gradually increasing. In order to solve the current energy dilemma, Natural gas hydrate (NGH) is considered as an ideal alternative energy. At the same time, solid fluidization exploitation is an ideal method. However, in the process of that, sand and hydrate ore bodies enter the closed pipeline together, which will block the pipeline and increase the difficulty of exploitation. Therefore, the pre-separation of sand by hydrocyclone plays an important role in solid fluidization exploitation. In this study, the numerical simulation method was used to study the internal flow field characteristics of the hydrocyclone, and the effects of different flow rate, different flow ratio, different sand content and different particle diameter on the phase distribution were investigated. The results show that: at the same axial position, the increase of flow rate and sand content makes the sand phase more distributed at the edge of the flow field. Under the same working conditions, the sand gradually migrates to the center of the flow field with the increase of the axial distance. By calculation, it is obtained that under the optimum working condition of the flow rate is 4.83m3/h, the flow ratio is 20%, the sand content is 20%, and sand diameter is 80µm, the maximum Es is 22.1% and the minimum is 86.1%. Finally, a comprehensive analysis of the hydrocyclone in this study shows that this hydrocyclone is only applicable to rough pre-separation of sand in the process of solid fluidization exploitation. Through the study of the internal flow field characteristics and phase distribution law of the hydrocyclone, this study provides a reference for the practical engineering application of sand phase pre-separation in the solid fluidization exploitation of NGH.

Simultaneous Production of Aromatics and COx-Free Hydrogen via Methane Dehydroaromatization in Membrane Reactors: A Simulation Study.

As an alternative route for aromatics and hydrogen production, methane dehydroaromatization (MDA) is of significant academic and industrial interest due to the abundance of natural gas resources and the intensive demand for aromatics and COx-free hydrogen. In the present work, a simulation study on MDA in membrane reactors (MRs) was performed with the aim of co-producing aromatics and COx-free hydrogen with a highly improved efficiency. The effects of various parameters, including catalytic activity, membrane flux and selectivity, as well as the operating conditions on the MR performance were discussed with respect to methane conversion, hydrogen yield, and hydrogen purity. The results show that catalytic activity and membrane flux and selectivity have significant impacts on CH4 conversion and H2 yield, whereas H2 purity is mainly dominated by membrane selectivity. A highly improved MDA is confirmed to be feasible at a relatively low temperature and a high feed pressure because of the hydrogen extraction effect. To further improve MDA in MRs by intensifying H2 extraction, a simple configuration combining a fixed-bed reactor (FBR) and an MR together is proposed for MDA, which demonstrates good potential for the high-efficiency co-production of aromatics and COx-free hydrogen.

CH/CH2 Group Clusters Doping Methane Hydrate Cages.

Methane hydrate is a crystalline compound with methane molecules as guest species trapped in host water cages. In this study, we detected methane hydrate with water cages doped by (Caromatic-H)5 clusters, (Caromatic-H)6 clusters, and (3Caliphatic-H2 + 2H2O) clusters using current spectroscopic techniques and differential scanning calorimetry (DSC). Methane molecules are trapped in the doped cages with type sI forming in nanoscale silica gel pores. The relative quantity ratio of host carbon to guest carbon in the doped hydrate sample reaches approximately 3.58. Methane hydrate doped by CH/CH2 group clusters greatly improves the ability of the hydrate unit cell to store methane and increases the stability of methane hydrate. Fast proton diffusion in the doped methane hydrate was confirmed. The results of this study will provide efficient and energy saving technical support for disruptive changes in hydrate storage and transportation of methane gas technology with a doped and dense solid phase.

Author Correction: Pectin as an Extraordinary Natural Kinetic Hydrate Inhibitor.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Novel crude glycerol pretreatment for selective saccharification of sugarcane bagasse via fast pyrolysis.

Pretreatment is a vital process for efficient saccharification and utilization of lignocellulose. In this study, crude glycerol derived from biodiesel production was used for pretreatment to facilitate selective saccharification via fast pyrolysis. Due to the efficient removal of alkali and alkaline earth metals (>95.0%) and lignin (79.4%) by crude glycerol pretreatment, the yield of levoglucosan was evaluated to 25.2% as compared to those from pure glycerol pretreated (14.4%) and untreated sugarcane bagasse (8.4%). Meanwhile, the production of inhibitors (e.g. acetic acid, phenol) to biocatalysts was also obviously inhibited from crude glycerol pretreated biomass. Consequently, this work provided a cost-effective and eco-friendly pretreatment mode, which could not only make full utilization of crude glycerol, but also improve the fermentability of lignocellulosic pyrolysate.

Thermal oxidative degradation kinetics of agricultural residues using distributed activation energy model and global kinetic model.

The study concerned the thermal oxidative degradation kinetics of agricultural residues, peanut shell (PS) and sunflower shell (SS). The thermal behaviors were evaluated via thermogravimetric analysis and the kinetic parameters were determined by using distributed activation energy model (DAEM) and global kinetic model (GKM). Results showed that thermal oxidative decomposition of two samples processed in three zones; the ignition, burnout, and comprehensive combustibility between two agricultural residues were of great difference; and the combustion performance could be improved by boosting heating rate. The activation energy ranges calculated by the DAEM for the thermal oxidative degradation of PS and SS were 88.94-145.30 kJ mol-1 and 94.86-169.18 kJ mol-1, respectively. The activation energy obtained by the GKM for the oxidative decomposition of hemicellulose and cellulose was obviously lower than that for the lignin oxidation at identical heating rate. To some degree, the determined kinetic parameters could acceptably simulate experimental data.

Investigation into THF hydrate slurry flow behaviour and inhibition by an anti-agglomerant.

Hydrate plugs are one of the highest risks for gas and oil transportation in pipelines, especially in deep sea environments. In a newly built-up loop, pilot-scale experiments were carried out to study typical hydrate plug phenomena and to explore the specific reasons behind these. A tetrahydrofuran (THF) hydrate slurry was formed and investigated in this loop fluid at two liquid loadings (50 vol% and 100 vol%) with/without a typical anti-agglomerant, KL-1. Morphology and temperature variations revealed that THF hydrate slurry evolution had four stages: (a) flowable fluid; (b) particle formation; (c) agglomeration; and (d) plug. The effect of liquid loading (LL) and an anti-agglomerant (AA) on morphology and temperature in three cases were studied. The morphologies in each stage were compared for the three cases. Hydrate conversion was calculated according to the liquid and solid volume proportion in these morphologies. From these morphologies, heterogeneous hydrate deposition was found to be more likely to happen in 50 vol% than in the 100 vol% LL system. The hydrate plug was also found to be induced by hydrate deposition rather than the bed at the bottom of the pipeline. By dispersing hydrate particle agglomeration, AA compressed hydrate deposition and the plug.

Evaluation of agricultural residues pyrolysis under non-isothermal conditions: Thermal behaviors, kinetics, and thermodynamics.

The thermal conversion characteristics, kinetics, and thermodynamics of agricultural residues, rape straw (RS) and wheat bran (WB), were investigated under non-isothermal conditions. TGA experiments showed that the pyrolysis characteristics of RS were quite different from those of WB. As reflected by the comprehensive devolatilization index, when the heating rate increased from 10 to 30Kmin-1, the pyrolysis performance of RS and WB were improved 5.27 and 5.96 times, respectively. The kinetic triplets of the main pyrolysis process of agricultural residues were calculated by the Starink method and the integral master-plots method. Kinetic analysis results indicated that the most potential kinetic models for the pyrolysis of RS and WB were D2 and F2.7, respectively. The thermodynamic parameters (ΔH, ΔG, and ΔS) were determined by the activated complex theory. The positive ΔH, positive ΔG, and negative ΔS at characteristic temperatures validated that the pyrolysis of agricultural residues was endothermic and non-spontaneous.

Comparative evaluation of thermal oxidative decomposition for oil-plant residues via thermogravimetric analysis: Thermal conversion characteristics, kinetics, and thermodynamics.

Thermal oxidative decomposition characteristics, kinetics, and thermodynamics of rape straw (RS), rapeseed meal (RM), camellia seed shell (CS), and camellia seed meal (CM) were evaluated via thermogravimetric analysis (TGA). TG-DTG-DSC curves demonstrated that the combustion of oil-plant residues proceeded in three stages, including dehydration, release and combustion of organic volatiles, and chars oxidation. As revealed by combustion characteristic parameters, the ignition, burnout, and comprehensive combustion performance of residues were quite distinct from each other, and were improved by increasing heating rate. The kinetic parameters were determined by Coats-Redfern approach. The results showed that the most possible combustion mechanisms were order reaction models. The existence of kinetic compensation effect was clearly observed. The thermodynamic parameters (ΔH, ΔG, ΔS) at peak temperatures were calculated through the activated complex theory. With the combustion proceeding, the variation trends of ΔH, ΔG, and ΔS for RS (RM) similar to those for CS (CM).

Pectin as an Extraordinary Natural Kinetic Hydrate Inhibitor.

Pectin as a novel natural kinetic hydrate inhibitor, expected to be eco-friendly and sufficiently biodegradable, was studied in this paper. The novel crystal growth inhibition (CGI) and standard induction time methods were used to evaluate its effect as hydrate inhibitor. It could successfully inhibit methane hydrate formation at subcooling temperature up to 12.5 °C and dramatically slowed the hydrate crystal growth. The dosage of pectin decreased by 66% and effective time extended 10 times than typical kinetic inhibitor. Besides, its maximum growth rate was no more than 2.0%/h, which was far less than 5.5%/h of growth rate for PVCap at the same dosage. The most prominent feature was that it totally inhibited methane hydrate crystal rapid growth when hydrate crystalline occurred. Moreover, in terms of typical natural inhibitors, the inhibition activity of pectin increased 10.0-fold in induction time and 2.5-fold in subcooling temperature. The extraordinary inhibition activity is closely related to its hydrogen bonding interaction with water molecules and the hydrophilic structure. Finally, the biodegradability and economical efficiency of pectin were also taken into consideration. The results showed the biodegradability improved 75.0% and the cost reduced by more than 73.3% compared to typical commercial kinetic inhibitors.

A polypyrrole/anthraquinone-2,6-disulphonic disodium salt (PPy/AQDS)-modified anode to improve performance of microbial fuel cells.

This study reports a new approach of improving performance of microbial fuel cells (MFCs) by using a polypyrrole/anthraquinone-2,6-disulphonic disodium salt (PPy/AQDS)-modified anode. The immobilization of AQDS on a carbon felt anode was accomplished by electropolymerization of pyrrole while using AQDS as the dopant. The dual-chamber MFC operated with this modified anode in the presence of Shewanella decolorationis S12 showed the maximum power density of 1303 mW m(-2), which was 13 times larger than that obtained from the MFC equipped with an unmodified anode. Evidence from cyclic voltammerty (CV) and scanning electron microscopy (SEM) results indicated that the increase in power generation was assigned to the increased surface area of anode, the enhanced electron-transfer efficiency from the bacteria to the anode via immobilized AQDS, and an increase in the number of bacteria attached to anode.

The semi-ideal solution theory for mixed ionic solutions at solid-liquid-vapor equilibrium.

The semi-ideal solution theory has been presented to describe the changes in thermodynamic properties accompanying the process of mixing the nonideal electrolyte solutions M(i)X(i)-(NY)sat-H2O (i = 1 and 2) at constant activities of NY and H2O, including concentration, chemical potential, activities of all M(i)X(i), Gibbs free energy, enthalpy, entropy, thermal properties, and volumetric properties. The theory states that, under the conditions of equal activities of NY and H2O, the average hydration numbers characterizing the ion-solvent interactions have the same values in the mixture as in the subsystems and the process of mixing these nonideal electrolyte solutions is as simple as that of mixing the ideal solutions if the contributions from the ion-ion interactions to the solvent activity are assumed to be the same in the mixture as in its subsystems, which has been justified by the calculations of the Pitzer equation. Therefore, a series of novel linear equations are established for the thermodynamic properties accompanying the process of mixing these nonideal solutions as well as mixing the ideal solutions M(i)X(i)-(NY)sat-H2O (i = 1 and 2) of equal mole fractions of NY and H2O. From these equations, the widely applied empirical Zdanovskii's rule is derived theoretically, and the important constant in the McKay-Perring equation under isopiestic equilibrium is determined theoretically, which has been substantiated by comparisons with the experimental results for 18 mixtures reported in the literature. Isopiestic measurements have been made for the systems BaCl2-LaCl3-H2O, NaCl-BaCl2-LaCl3-H2O, and NaCl-LaCl3-BaCl2.2H2O(sat)-H2O at 298.15 K. The results are used to test the novel linear concentration relations, and the agreement is excellent. The novel predictive equation for the activity coefficient of M(i)X(i) in M1X1-M2X2-(NY)sat-H2O has been compared with the calculations of the Pitzer equation, and the agreement is good.