Effect of dodecyl dimethyl benzyl ammonium chloride on CH4 hydrate growth and agglomeration in oil-water systems

Low dosage hydrate inhibitor (LDHI) is an effective choice to prevent hydrate formation and blockage in petroleum and natural gas processing industry. This study investigated the effect of dodecyl dimethyl benzyl ammonium chloride (DDBAC) on CH4 hydrate growth and agglomeration in oil-water systems. Hydrate formation kinetics and torque changes were determined with the isothermal-isochoric method. The kinetic experimental results revealed that 0.35 wt% DDBAC exerted a strong and stable inhibition effect on CH4 hydrate growth, represented by long induction time and low gas uptake amount. The chemical affinity modeling calculation results showed that DDBAC decreased normalized hydrate formation rate and increased the kinetic equilibrium time. The torque changes demonstrated that anti agglomeration effect strengthened with the increase of DDBAC mass fraction. In addition, the mechanism of CH4 hydrate formation in studied system was proposed combining the experimental results, hydrate morphology and DDBAC's properties. It showed that DDBAC could hinder gas dissolution in oil phase, separate hydrate particles from each other and make hydrate surface soft. These results are of fundamental value in developing LDHI and understanding the mechanism of hydrate formation, which are essential in preventing hydrate blockage and ensuring safety production of oil and gas. (c) 2020 Elsevier Ltd. All rights reserved

Stability Conditions for Semiclathrate Hydrates Formed with Tetrabutylammonium Chloride plus Tetrabutylphosphonium Chloride + CH4

Semiclathrate hydrate is a promising method to ease the thermodynamic conditions of gas hydrate formation for hydrate-based gas storage and transportation on the industrial scale. The phase equilibrium conditions of mixed semiclathrate hydrate formed with tetrabutylammonium chloride (TBAC) + tetrabutylphosphonium chloride (TBPC) + CH4 were measured systematically by employing the isochoric pressure-search method. The data revealed that mixed TBAC + TBPC exerted relatively higher stabilization effect on CH4 hydrate than pure TBAC or TBPC, and the strongest stabilization effect showed up in system with 0.0300 total salt mole fraction (x(salt)) and 0.75 TBAC salt ratio (x(TBAC)/x(salt)). In addition, the dissociation enthalpies of mixed (TBAC + TBPC + CH4) hydrate were calculated with the obtained experimental data by using the simplified Clausius-Clapeyron equation and the Peng-Robinson equation of state. It was found that the mean dissociation enthalpies for mixed (TBAC + TBPC + CH4) hydrate with different salt concentration relied on a (153.04 to 203.92 kJ/molCH(4)) scale, which was significantly higher than that of the pure CH4 hydrate. The data generated in this work showed that mixed TBAC + TBPC could enhance CH4 hydrate stability and the stored energy effectively

Molecular and Functional Effects of a Splice Site Mutation in the MYL2 Gene Associated with Cardioskeletal Myopathy and Early Cardiac Death in Infants

The homozygous appearance of the intronic mutation (IVS6-1) in the MYL2 gene encoding for myosin ventricular/slow-twitch skeletal regulatory light chain (RLC) was recently linked to the development of slow skeletal muscle fiber type I hypotrophy and early cardiac death. The IVS6-1 (c403-1G>C) mutation resulted from a cryptic splice site in MYL2 causing a frameshift and replacement of the last 32 codons by 19 different amino acids in the RLC mutant protein. Infants who were IVS6-1(+∕+)-positive died between 4 and 6 months of age due to cardiomyopathy and heart failure. In this report we have investigated the molecular mechanism and functional consequences associated with the IVS6-1 mutation using recombinant human cardiac IVS6-1 and wild-type (WT) RLC proteins. Recombinant proteins were reconstituted into RLC-depleted porcine cardiac muscle preparations and subjected to enzymatic and functional assays. IVS6-1-RLC showed decreased binding to the myosin heavy chain (MHC) compared with WT, and IVS6-1-reconstituted myosin displayed reduced binding to actin in rigor. The IVS6-1 myosin demonstrated a significantly lower Vmax of the actin-activated myosin ATPase activity compared with WT. In stopped-flow experiments, IVS6-1 myosin showed slower kinetics of the ATP induced dissociation of the acto-myosin complex and a significantly reduced slope of the kobs-[MgATP] relationship compared to WT. In skinned porcine cardiac muscles, RLC-depleted and IVS6-1 reconstituted muscle strips displayed a significant decrease in maximal contractile force and a significantly increased Ca(2+) sensitivity, both hallmarks of hypertrophic cardiomyopathy-associated mutations in MYL2. Our results showed that the amino-acid changes in IVS6-1 were sufficient to impose significant conformational alterations in the RLC protein and trigger a series of abnormal protein-protein interactions in the cardiac muscle sarcomere. Notably, the mutation disrupted the RLC-MHC interaction and the steady-state and kinetics of the acto-myosin interaction. Specifically, slower myosin cross-bridge turnover rates and slower second-order MgATP binding rates of acto-myosin interactions were observed in IVS6-1 vs. WT reconstituted cardiac preparations. Our in vitro results suggest that when placed in vivo, IVS6-1 may lead to cardiomyopathy and early death of homozygous infants by severely compromising the ability of myosin to develop contractile force and maintain normal systolic and diastolic cardiac function