Electromotive forces of cells without liquid junctions K-ISE | CsCl(m E ) | ISE-Cl and K-ISE | CsCl(m E ), glucose(m S ) | ISE-Cl have been measured at 5 K intervals from T ) 278.15 to 313.15 K, where m E ) (0.001 to 0.1) mol kg -1 and m S ) (0.01 to 3.0) mol kg -1 . The activity coefficients of CsCl in glucose + water solutions can be obtained from these electromotive force data; in the meantime, the interaction parameters of the CsCl + glucose pair in water, g EN , h EN , s EN , and c p,EN , can be evaluated. We show that g EN > 0, h EN > 0, s EN > 0, and c p , EN < 0 at all four temperatures (except for h EN and s EN at T ) 313.15 K), and the values of g EN , s EN , and c p , EN vary slightly with temperature, whereas the values of h EN is very sensitive to the temperatures used. These thermodynamic parameters were discussed in terms of a model of the structural interaction and electrostatic interaction and were analyzed by the group additivity principle.

Shale gas resources provide a new impetus to alleviate the contradiction between China's oil and gas supply and demand. As an important part of shale gas, understanding the occurrence mechanism of adsorbed gas can help shale gas resources to be better developed and used. This time, a series of experiments, such as low-temperature nitrogen adsorption and methane isotherm adsorption, were conducted to discuss the pore structure, adsorption performance, and adsorption mechanism of shale. The results show the following: (1) Shale pores are dominated by nanopores, and pores with a pore width of less than 2 nm have the best relationship with the shale surface area and adsorption capacity. (2) Total organic carbon (TOC) plays an important role in controlling the specific surface area and methane adsorption capacity of shale. This is mainly due to the large number of micropores (pore size of <2 nm) developed in organic matter. Micropores provide the main specific surface area and adsorption sites for methane adsorption. (3) A variety of models were used to fit shale methane isotherm adsorption data. The results show that the SDR model and Langmuir model have the best fit. The methane adsorption performance of shale is controlled by many factors; the adsorption capacity becomes weaker as the temperature rises; and this influence is also affected by TOC. (4) In comparison to the adsorption capacity, the change of the adsorbed phase density is more complicated: overall, there is a weak positive correlation with TOC; as the temperature increases, the adsorbed phase density decreases. However, this law is not stable, and there are different performances in different experiments. (5) The adsorption comparison results show that the shale methane adsorption is mainly multilayer adsorption and micropore filling.

Numerous models have been used to describe the isotherm adsorption of supercritical methane in porous media. Many models assume that the adsorbed phase density does not change with pressure during the adsorption process. However, recent studies show that this assumption is unreasonable, and the resulting error is enormous. Therefore, we propose an improved isotherm adsorption model in shale that assumes that the adsorbed phase density keeps changing and that adsorbed phase volume remains constant during the adsorption process [the variable density adsorption (VD) model]. A logarithmic function is used to describe the change of the adsorbed phase density during the adsorption process. The product of the adsorbed phase density and volume is used to calculate the adsorption capacity. The fitting results for large amounts of methane adsorption data show that this assumption is reasonable. The fitting results are consistent with the molecular simulation, and it will be more convenient to obtain the truly adsorbed phase volume and density. The adsorbed phase volume and density obtained by the VD model show a good positive correlation with the total organic carbon, specific surface area, and micropore volume, which indicates the rationality of adsorption parameters fitted by the model. As a result of the correct calculation of the adsorption phase density, the gas in place (GIP) obtained by the VD model is lower than the supercritical Dubinin–Radushkevich model. The new model proposed this time provides a new tool for the study of shale methane isotherm adsorption and a new model for the calculation of GIP. Using this model, the adsorbed phase density and volume of methane can be obtained more conveniently and accurately. This will be a milestone in the VD model.