Adhesion strength of tetrahydrofuran hydrates is dictated by substrate stiffness

Understanding the hydrate adhesion is important to tackling hydrate accretion in petro-pipelines.Herein,the relationship between the Tetrahydrofuran(THF)hydrate adhesion strength(AS)and surface stiffness on elastic coatings is systemically examined by experimental shear force measurements and theoretical methods.The mechanical factor-elastic modulus of the coatings greatly dictates the hydrate AS,which is explained by the adhesion mechanics theory,beyond the usual factors such as wettability and structural roughness.Moreover,the hydrate AS increases with reducing the thickness of the elastic coatings,resulted from the decrease of the apparent surface elastic modulus.The effect of critical thickness for the elastic materials with variable elastic modulus on the hydrate AS is also revealed.This study provides deep perspectives on the regulation of the hydrate AS by the elastic modulus of elastic materials,which is of significance to design anti-hydrate surfaces for mitigation of hydrate accretion in petro-pipelines.

Tensile properties of structural I clathrate hydrates:Role of guest-host hydrogen bonding ability

Clathrate hydrates(CHs)are one of the most promising molecular structures in applications of gas capture and storage,and gas separations.Fundamental knowledge of mechanical characteristics of CHs is of crucial importance for assessing gas storage and separations at cold conditions,as well as understanding their stability and formation mechanisms.Here,the tensile mechanical properties of structural I CHs encapsulating a variety of guest species(CH_(4),NH_(3),H_(2)S,CH_(2)O,CH_(3)OH,and CH_(3)SH)that have different abilities to form hydrogen(H-)bonds with water molecule are explored by classical molecular dynamics(MD)simulations.All investigated CHs are structurally stable clathrate structures.Basic mechanical properties of CHs including tensile limit and Young’s modulus are dominated by the H-bonding ability of host-guest molecules and the guest molecular polarity.CHs containing small CH_(4),CH_(2)O and H_(2)S guest molecules that possess weak H-bonding ability are mechanically robust clathrate structures and mechanically destabilized via brittle failure on the(101)plane.However,those entrapping CH3SH,CH3OH,and NH3 that have strong H-bonding ability are mechanically weak molecular structures and mechanically destabilized through ductile failure as a result of gradual global dissociation of clathrate cages.