Abstract:

Based on adsorption theory of surfactants at solid-liquid interface, promotion effects of three surfactants on formation of methane hydrates were studied in a stainless steel reactor at conditions of 2℃ and 6.6 MPa without stirring. Surfactants were sodium dodecyl sulfate (SDS), sodium alcohol ether sulphate (AES) and dodecyl alcohol ethoxylates (AEO). The results showed a good correlation between macroscopic morphology of hydrates and molecular morphology of adsorbed surfactants. With directional adsorption of SDS and AES on metal surface, interface hydrophobicity was increased and a porous media environment was formed at solid surface, which promoted bulk water to move through the porous media to gas phase driven by capillarity. Thus, both nucleation rate and sites were increased. However, no AEO adsorption on metal surface resulted in decrease of the promotion effect on hydrate formation. With SDS, AES and AEO solutions at concentration of 300 mg·L^-1, hydrate storage capacity were 131.4, 128.3 and 12.3 (volume ratio) and average gas storage rates were 5.8, 7.6 and 0.07 mmol·min^-1, respectively. With concentration increase of SDS (80-1200 mg·L^-1) and AES (60-1350 mg·L^-1), hydrate storage capacity first enhanced and then decreased whereas average gas storage rate kept increasing linearly. Therefore, hydrate formation can be significantly promoted by choosing appropriate types and concentrations of surfactants.

Key words: methane hydrate, surfactant, storage capacity, adsorption, nucleation

摘要：

基于表面活性剂固-液界面吸附理论，在无搅拌条件下研究了十二烷基硫酸钠（SDS（、脂肪醇聚乙烯醚硫酸钠（AES（、脂肪醇聚乙烯醚（AEO（3种表面活性剂在不锈钢反应釜中对甲烷水合物生成的促进效果。结果表明：水合物的生成形态与表面活性剂吸附金属表面形态有良好的对应关系；SDS与AES在金属表面的吸附作用可使水合物成核速率提高，成核位置增多。由于AEO不能在金属壁面发生吸附，导致对水合物生成促进效果降低，在浓度为300 mg·L^-1的SDS、AES和AEO溶液中，水合物储气密度及平均储气速率分别为131.4、128.3、12.3（体积比（和5.8、7.6、0.07 mmol·min^-1；逐步提高SDS溶液浓度（80~1200 mg·L^-1（和AES溶液浓度（60~1350 mg·L^-1（，水合物储气密度首先增大然后减小，储气速率线性增大。因此，合理选择表面活性剂种类及浓度，可显著促进水合物生成。

关键词: 甲烷水合物, 表面活性剂, 储气密度, 吸附, 成核