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Cite This: J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Comparative Study of Ag+‑Based Adsorbents Performance in Ethylene/Ethane Separation Chao Wu,# Jiajie Wang,# Yan Fang, Zhi Wang, Dejun Fei, Xue Han, and Yagu Dang* School of Chemical Engineering, Sichuan University, Chengdu 610065, China

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S Supporting Information *

ABSTRACT: Four kinds of π-complexation adsorbents are synthesized via ion exchange method or incipient wetness impregnation method with Amberlyst 35, SBA-15, TUD-1, and KIT-6 as supports, and AgNO3 as active ingredient. The samples are characterized by N2 adsorption/desorption. Fourier transformed infrared spectroscopies, transmission electron microscopy, X-ray diffraction spectrum analysis, and coupled plasma optical emission spectrometry are also used as adsorbents for ethylene/ethane adsorptive separation. The results show that the specific surface area and the dispersion of silver ions affect the separation performance of the adsorbent. Ag−Amberlyst 35 has the highest ethylene/ethane selectivity among these adorbents while the adsorbed amounts of ethylene of the three mesoporous silica complexation adsorbents are higher. Adsorption thermodynamics analysis suggests that the interaction of ethylene with adsorbent is a mild chemical adsorption. An adsorption kinetics study indicates that the adsorption of ethylene on silver-supported mesoporous materials is not a simple diffusion-control process. The adsorption behavior of ethylene on the π-complexation adsorbent has an energy barrier in the range of 24−33 kJ/mol. Among the adsorbents in this work, the KIT-6-based adsorbent has the best mass kinetic performance due to its three-dimensional regular interconnected mesoporous structure.

1. INTRODUCTION Ethylene/ethane separation is one of the most important separation processes in the petrochemical industry.1−5 πComplexation adsorptive separation technology utilizes the πcomplexation reaction6,7 of ethylene and transition-metal ions of Cu+ or Ag+ with the advantages of low energy consumption, low investment, and high degree of automation, to which reseachers have paid great attention.8,9 The π-complexation adsorbent is the core of π-complexation adsorptive separation technology.10−21 Recent studies have focused on how to achieve highly dispersed silver ions on the support. Yang loaded silver nitrate on silica, MCM-41, and SBA-15 via the impregnation method.8 He found that the large specific area of mesoporous material resulted in highly dispersed silver ions and thus a good ethylene capacity and selectivity. Wu synthesized a silver ion exchanged resin and studied its ethylene/ethane adsorption performances.22 His results showed that this material had extremely high ethylene selectivity but a relatively low adsorption amount. In recent years, Yu compared three kinds of Ag−based adsorbents using © XXXX American Chemical Society

commercial silica, SBA-15, and KIT-6 as support materials, respectively.23 They found similar results with Yang’s work: ordered mesoporous silica, especially the 2D-ordered mesoporous SBA-15, can improve silver dispersion. Besides silver dispersion, the ethylene/ethane PSA process also needs a good adsorption mass transfer rate, which leads to a fast equilibrium and helps to shorten the duration of each adsorption−desorption cycle. However, researchers have paid little attention to the structure−performance relationship between pore structures and kinetic performances of πcomplexation adsorbents. On the point of this view, we chose TUD-1, SBA-15, and KIT-6 as support, as microporous materials, amorphous mesoporous materials, 2D-ordered mesoporous materials, and 3D-connected ordered materials, respectively. Compared with Cu(I), Ag(I) was relatively stable and chosen as an adsorption center. The purpose of this paper Received: September 9, 2018 Accepted: January 4, 2019

A

DOI: 10.1021/acs.jced.8b00806 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

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Figure 1. Schematic diagram of the volumetric apparatus.

TEM characterization was performed on a Tecnai G2F20 transmission electron microscope manufactured by FEI Company at a working voltage of 220 V. N2 adsorption/ desorption isotherms at 77 K was evaluated by the United States Micromeritics Instruments Tristar II 3020 automatic adsorption instrument. The specific surface area was calculated using the Brunauer−Emmett−Teller (BET) method, the total pore volume was calculated from the amount of adsorption at a relative pressure (P/P0) near to 1, the nonlocalized Density Functional Theory (NLDFT) method was used to calculate the micropore and mesopore volume, the pore diameter and pore diameter distribution were calculated by BJH method from the desorption isotherm. 2.3. Adsorption Measurements of Ethylene and Ethane. The apparatus for the adsorption isotherms of ethylene and ethane at three temperatures (303.15 K, 323.15 K, 343.15 K) was shown in Figure 1. The test principle of this apparatus was the static volumetric method. The adsorption cell was initially in a vacuum state, and the adsorption equilibrium data can be obtained as the gas enters the adsorption cell. The volumes of adsorption cell and reference cell are 9.76 and 89.56 mL, respectively. The adsorption kinetics curve was obtained by using a static volumetric method: each time a certain pressure of ethylene gas was charged and then the adsorption cell was opened, the decrease of the adsorption pressure at a set time interval can be systematically recorded, and through calculation, changes in pressure over time can be translated into adsorbed amount changes with time curve, that is, ethylene adsorption kinetics curve. The temperature difference between the adsorption cell and the reference cell was controlled within ±0.5 K. 2.4. Adsorption Isotherm Model. According to the reported literature,26−28 the Langmuir−Fruendlich method was used to describe ethane and ethylene adsorption behaviors; the form is as follows:

is to discuss the differences between the adsorbents through the experimental data results, analyze the structure-performances, and establish the adsorption kinetics model. The obtained results are of great significance to the further development of π-complexation adsorbents.

2. EXPERIMENT 2.1. Preparation of Adsorbents. Preparation of Ag− Amberlyst 35 adsorbent: Amberlyst 35 resin was purchased from Changzhou Teva Trading Co., Ltd. The Amberlyst 35 resin was washed with deionized water and methanol for several times, then filtered, placed in an oven, and dried at 105 °C for 12 h. A 0.4 g portion of AgNO3 was dissolved in 30 mL of water, and the dried resin was placed in the solution. The mixture was then stirred at 25 °C for 3 h. After modification, the sample was washed by deionized water and methanol until the supernatant was clarified, and then dried at 105 °C for 12 h. The obtained adsorbent was labeled as Ag−Amberlyst 35. Preparation of Ag−SBA-15, Ag−TUD-1, Ag−KIT-6 and adsorbents: The mesporous SBA-15, TUD-1, KIT-6 was prepared according to the procedure reported by refs 24 and 25. The π-complexation adsorbents were prepared by the incipient wetness impregnation method. First, 0.4 g of AgNO3 was dissolved in about 2 to 5 mL of water, and then the solution of AgNO3 was dropwise added into 1 g of the carriers. After the addition was completed, the mixture was thoroughly stirred for 30 min, and then the products were dried at 50 °C for 3 h under reduced pressure (about 30 kPa), and finally heated in microwave (400 W) for 10 min. The obtained adsorbents were labeled as Ag−SBA-15, Ag−TUD-1, and Ag− KIT-6. 2.2. Characterizations. The samples were characterized by N2 adsorption/desorption, scanning electron microscopy (SEM), Fourier transform infrared spectrosopy (FTIR), inductively coupled plasma-optical emission spectrometry (ICP-OES), and transmission electron microscopy (TEM). Fourier transform infrared spectrosopy was performed by Spectrum TwoL1600300 to analyze Amberlyst 35 before and after modification. SEM analysis was performed by a JEOL model JSM-7500F field emission scanning electron microscope from Japan to scan Ag−Amberlyst 35. ICP-OES characterization was performed by the full-spectrum direct-reading ICAP6000 spectrometer from the United Kingdom to determine the Ag+ content of four π-complexation adsorbents.

q=

qmbp1/ n 1 + bp1/ n

(1)

where q (mL·g−1) is the adorbed amount at equilibrium pressure p (MPa), qm (mL·g−1) is the saturated adsorbed amount, b (MPa−1) is the adsorption equilibrium constant, and n is a dimensionless isotherm parameter characterizing the system heterogeneity. B



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Figure 2. N2 adsorption/desorption isotherms (left) and pore diameter distribution (right) of different samples.

Table 1. Textural Properties of Different Samples sample Amberlyst 35 Ag−Amberlyst 35 SBA-15 Ag−SBA-15 TUD-1 Ag−TUD-1 KIT-6 Ag−KIT-6

SBET (m2·g−1) 4.984 4.149 815.2 438.7 528.4 367.8 565.3 372.7

Vtotal (cm3·g−1)

Vmesoporous (cm3·g−1)

−3

1.93 × 10 3.99 × 10−3 0.759 0.525 0.832 0.588 1.048 0.665

5.38 × 10 1.02 × 10−2 1.076 0.662 0.886 0.615 1.158 0.737

(2)

where p, T, and q are the equilibrium pressure (MPa), the experimental temperature (K), the adorbed amount (mL·g−1), respectively, R is the universal gas constant (J·mol−1·K−1), and Q is the isosteric heat of adsorption (kJ·mol−1). The adsorption selectivity is a crucial factor to evaluate the efficiency of ethylene/ethane separation in the actual industrial production. The ideal adsorbed solution theory13,14,29 (IAST) has been extensively used for predicting the selectivity of mixtures. The adsorption isotherm model combined with IAST theory can effectively predict the ethylene/ethane separation selectivity under relatively low pressure. The ethylene/ethane selectivity is defined as follows:30 S1/2 =

qt q∞

dt

= ks(qe − qt )2

10−3 10−2 10−2

6.618 5.620 3.641 3.628 7.760 7.788

=1−

6 π2

∞

∑ n=1

ij Dn2π 2t yz 1 jj− zz exp j z 2 n2 r k {

(5)

3. RESULTS AND DISCUSSION 3.1. Characterization of Adsorbents. 3.1.1. Pore Structure Characterization. The N2 adsorption/desorption isotherms and the pore size distribution of the BJH method at 77 K are shown in Figure 2 and Figure S1 (Supporting Information), respectively. Table 1 summarizes the textural properties of four samples before and after AgNO 3 modification. From Figure 2 and Figure S1, the positions and sizes of the loops of SBA-15, TUD-1, and KIT-6 before and after modification did not change, indicating that the modification of AgNO3 does not change their pore structure. The average pore size of SBA-15 decreases from 6.62 to 5.60 nm while the other two mesoporous adsorbents did not change. This phenomenon was reported in Yu’s work as well and possibly because silver can enter 2D-ordered pores more easily.23 What also can be seen is that the mesoporous structure and uniform mesopore distribution in SBA-15 and TUD1-1 did not change after silver loading. After modification, the specific surface area and pore volume decreases due to AgNO3 molecules in the

(3)

where x1(y1) and x2(y2) are the mole fractions of components 1 and 2 in the adsorbed phase (gas phase), respectively. In this research, component 1 is ethylene and component 2 is ethane. 2.6. Kinetic Model. Adsorption kinetics must be studied to realize the industrial applications of the adsorbent. The pseudo-second-order kinetic model31,32 is mainly used for the coexistence of physical adsorption and chemisorption with limited adsorption sites, such as CO2 adsorption, water treatment, the form is as follows: dqt

Daverage (nm)

10−4 10−4

where qt (mL·g−1) is the adsorbed amount at time t (s), q∞ (mL·g−1) is the adsorbed amount at time ∞, and D/r2 (s−1) is the diffusion time constant.

x1/y1 x 2/y2

8.97 × 5.23 × 0.206 0.078 8.59 × 0 4.81 × 3.32 ×

where qt (mL·g−1) is the adsorbed amount at time t (s), qe (mL·g−1) is the saturated adsorded amount, ks (g·mL·s−1) is the mass transfer coefficient. The diffusion model33 is derived from the diffusion equation of spherical porous particles. As the pressure change is quiet small, the Crank’s model is suitable for the adsorption process of kinetic separation or internal diffusion control.34 The form is as follows:

2.5. Isosteric Heat of Adsorption and Adsorption Selectivity. The isosteric heat of adsorption at a given adsorption amount was calculated by Clausius−Clapeyron equation, and the form is as follows: ij ∂ ln p yz Q jj z j ∂(T ) zz = − RT 2 k {q

Vmicroporous (cm3·g−1)

−3

(4) C



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Figure 3. TEM images of different samples.

Figure 4. Adsorption isotherms of ethylene and ethane on different samples at three temperatures: (a) Ag−Amberlyst 35; (b) Ag−SBA-15; (c) Ag−TUD-1; (d) Ag−KIT-6.

3.1.2. Characterizations of Silver on the Supports. From the XRD patterns of these samples (Supporting Information), slight peaks of silver nitrate can be observed from Ag−TUD-1 and Ag−KIT-6 while no peaks can be found from resin. The results indicate that the silver species on TUD-1 and KIT-6 are AgNO3. The pattern of Ag−SBA-15 suggests that the silver species on the SBA-15 surface reach a monolayer dispersion state according to Xie’s work.39 There is no crystallized silver in Ag−Amberlyst-35 considering its low specific area. The peak

channel. However, the Amberlyst 35 is a typical micropore material and has the smallest specific area before and after the modification. Figure 3 shows the TEM images of Ag−SBA-15, Ag−TUD1, and Ag−KIT-6. Ag−SBA-15 has a two-dimensional hexagonal structure, Ag−TUD-1 has a foam-like structure, Ag−KIT-6 has a regular three-dimensional cubic phase structure pore. These mesoporous structures agree with the nitrogen adsorption/desorption characterization presented. D



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Table 2. Adsorbed Amount and Adsorption Heat of Ethylene and Ethane on Four π-Complexation Adsorbents at 303.15 K and 0.1 MPa sample

adsorbed amount of ethylene (mL/g)

adsorbed amount of ethane (mL/g)

adsorption selectivity

adsorption heat of ethylene (kJ/mol)

adsorption heat of ethane (kJ/mol)

Ag−Amberlyst 35 Ag−SBA-15 Ag−TUD-1 Ag−KIT-6

13.2 24.2 20.3 19.0

0.5 4.8 2.7 3.0

60.8 21.3 14.2 16.4

21.8 22.5 22.8 24.2

17.5 11.8 10.6

Figure 5. Pseudo-second order fitting of ethylene on four π-complexation adsorbents at different temperatures: (a) Ag−Amberlyst 35; (b) Ag− SBA-15; (c) Ag−TUD-1; (d)Ag−KIT-6.

of O−H vibration near 3300 cm−1 in the FTIR pattern of Ag− Amberlyst-35 (Supporting Information) decreased after Ag modification, which suggests that Ag+ ions have replaced H atom of the HO−SO2−R resulting in AgO−SO2−R structure. The SEM and EDS scanning images (Supporting Information) also show that the silver was highly dispersed in the resin frame.22 3.2. Adsorption Isotherms and Isosteric Heat of Adsorption of Ethylene and Ethane. The adsorption isotherms of ethylene and ethane on the four π-complexation adsorbents at three temperatures are shown in Figure 4. On the basis of the single component adsorption isotherm and the IAST theory, the corresponding ethylene/ethane adsorption selectivity for equal molar ethylene/ethane mixtures was predicted. From Figure 4, with the increase of temperature, the adsorbed amount of ethylene and ethane gradually decreases, because the π-complexation adsorption is an exothermic reaction. The increase in temperature rise is not conducive to the adsorption process. Table 2 summarizes ethylene adsorption capacity, ethane adsorption capacity, ethylene/ethane adsorption selectivity, and the corresponding adsorption heat of the four πcomplexation adsorbents at 303.15 K and 0.1 MPa. According to Table 2, the ethylene adsorption capacity of the three mesoporous silica adsorbents is about 20 mL/g, which is higher than the 13.2 mL/g of Ag−Amberlyst 35. However, the

ethylene/ethane adsorption selectivity of Ag−Amberlyst 35 is up to 60.8 at 0.1 MPa, which was significantly higher than that of the other three adsorbents. The adsorbed amount of ethylene consists of physical adsorption and π-complexation adsorption. The ethylene complexation adsorption capacities of the four adsorbents are basically equal due to the same silver loading amount which can be seen from ICP-OES (Supporting Information). The physical adsorption capacity of ethylene of the three mesoporous silica adsorbents is significantly higher than that of Ag−Amberlyst 35, because the specific surface area of Ag− Amberlyst 35 is only about 1/100 of the three mesoporous silica adsorbents. The small specific surface area provides fewer physical adsorption sites, resulting in low physical adsorption capacity, which can be seen from the adsorption isotherms of the four samples before modification in Figure S6. After Amberlyst 35 was modified by AgNO3, the sulfonic acid group of Amberlyst 35 was replaced by Ag+ ions, and the complexed adsorption capacity of ethylene was significantly increased. Therefore, the adsorption selectivity of Ag−Amberlyst 35 is the largest. Besides, Table S1 )lists adsorption selectivity comparison of different adsorbents at 0.1 MPa in this paper and in the literature.34 The properties of the four complexation adsorbents in this paper are at the upper middle level. From Table 2, the adsorption heat of ethylene on the three mesoporous silica complexation adsorbents is obviously higher E



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Table 3. Kinetic Parameters of Pseudo-second-order for Ethylene and the Corresponding Activation Energy sample Ag−Amberlyst 35

Ag−SBA-15

Ag−TUD-1

Ag−KIT-6

T/K 303.15 323.15 343.15 303.15 323.15 343.15 303.15 323.15 343.15 303.15 323.15 343.15

qe/mL·g−1

ks/g·mL−1·s−1 −4

2.64 × 10 5.40 × 10−4 1.17 × 10−3 1.02 × 10−2 1.64 × 10−2 3.16 × 10−2 7.0 × 10−3 1.39 × 10−2 2.45 × 10−2 1.41 × 10−2 3.26 × 10−2 6.46 × 10−2

17.1 14.6 11.1 27.9 22.8 18.1 20.1 14.4 10.0 21.7 14.7 9.5

than that of ethane because the π-complexation interaction of Ag+ ions with ethylene is stronger than the force of van der Waals between ethane and adsorbents. In addition, the literature35 shows that the physical adsorption heat is generally less than 20 kJ/mol, and the range of chemical adsorption heat is generally between 80 and 200 kJ/mol. The adsorption heat of ethylene and ethane on all four adsorbents consistently shows that ethane can only be adsorbed via physical adsorption while the interaction of ethylene with adsorbents is πcomplexation adsorption between the physisorption and chemisorption. The adsorption heat values of four adsorbents were similar, indicating that the pore structure and texture of the adsorbents did not affect the adsorption heat. At the same time, the adsorption heat of ethylene and ethane of the four adsorbents varied with the change of adsorbed amount, which suggests inhomogeneity of the adsorption energy on the surface of the adsorbents as shown in Figure S5. 3.3. Adsorption Kinetics of Ethylene. In this paper, the ethylene adsorption kinetics on four adsorbents at 1 atm and three temperatures (303.15, 323.15, and 343.15 K) are determined by using the static volumetric method. The adsorption curves are fitted by pseudo-second-order model and the diffusion model. The measured points and the fitted curves are shown in Figure 5 and Figure S7, and the fitted parameters are shown in Table 3 and Table S2). From Figure 5 and Figure 6s, the adsorption process of ethylene on Ag−Amberlyst 35 is relatively slow at 303.15 K, reaching saturated adsorption capacity of 36.8% at 100 s and 100% at 960 s. The adsorption rate of ethylene on Ag−SBA-15 and Ag−KIT-6 was fast from 0 to 10 s, and the saturated adsorption capacity can reach more than 60% instantaneously under this period, which is attributed to the regular pore structure of SBA-15 and KIT-6, so ethylene has low mass transfer resistance. The adsorption process of ethylene on Ag− TUD-1 was slower in the initial time, because Ag−TUD-1 was not order structure. During the adsorption process of ethylene on four adsorbents, Ag−SBA-15 equilibrated at 640 s, Ag− TUD-1 equilibrated at 540 s, and Ag−KIT-6 equilibrated at 480 s. As can be seen from Table 3, the correlation coefficients of the four adsorbents indicate that the pseudo-second-order kinetic model is suitable for describing the adsorption kinetics of ethylene. In terms of the mass transfer coefficient, the order of mass transfer from the pseudo-second-model to the fast-toslow sequence is Ag−KIT-6 > Ag−SBA-15 > Ag−TUD-1 > Ag−Amberlyst 35. Among these adsorbents the three-dimensional ordered pores of Ag−KIT-6 are extremely favorable for

R2

Ea/kJ·mol−1

0.9924 0.9934 0.9948 0.8842 0.8979 0.9084 0.9757 0.9881 0.9803 0.9082 0.9333 0.9074

32.1

24.3

27.1

32.9

the diffusion of ethylene molecules. The mass transfer coefficients of the four adsorbents increase with temperature, because as the temperature increases, the molecular motion is accelerated, and so is the mass transfer. In addition, the activation energies of ethylene on four adsorbents are calculated using the Arrhenius eq (Supporting Information). This parameter is not the intrinsic activation energy of πcomplexation reaction, but includes pore diffusion, adsorption, desorption, and surface diffusion. For the apparent activation energies of the processes, the activation energy values of the four adsorbents ranges from 24 to 33 kJ/mol, which is significantly higher than the activation energy of pure chemisorption of CO2 adsorbed on the MCM-41 loaded by amine,32 suggesting that π-complexation adsorption is kinetically favored with higher temperature. . It has been shown in the literature36 that π-complexation adsorption is a process controlled by diffusion and therefore it is fitted with diffusion model. The fitting parameters are shown in Table 1s. From Table S2, the correlation coefficients of Ag− Amberlyst 35 and Ag−TUD-1 are close to 1, and the adsorption process is obviously controlled by diffusion where it is difficult for ethylene to enter the pore of adsorbent and to bind with active sites. The correlation coefficients of Ag−KIT6 and Ag−SBA-15 are relatively small, because Ag−KIT-6 has three-dimensional regular pore and Ag−SBA-15 has twodimensional regular pore. It is easy for ethylene to enter the pores of these two kinds of adsorbents and bind with the active sites. The unsatisfactory fitting results indicate that on the other hand, the diffusion resistance of ethylene molecules in ordered mesopore is small and the whole process is not entirely controlled by diffusion, but rather includes diffusion and chemical adsorption. The compounding process and specific control steps need further study. In addition, from Table 1s, in terms of the diffusion time constants, the diffusion time constants fitted by the diffusion model from the largest to the smallest are Ag−KIT-6 > Ag−TUD-1 > Ag−SBA-15 > Ag−Amberlyst 35, again confirming that the ordered pores favor the mass transfer process. As a comparison, Table S3 lists the diffusion time constants of ethylene on Ag−KIT-6 and several π-complexation adsorbents reported in the literature.22,36,37 From comparison, the D/r2 value of Ag−KIT-6 is much larger than the other adsorbents. On the other hand, the time for Ag−KIT-6 to reach 90% saturation adsorption is only about 2 min, which is much shorter than activated carbon adsorbent and resin adsorbent. This feature of Ag−KIT-6 is conducive to shorten F



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the balance of operation time, improve equipment utilization, and has a certain industrial application prospects.38

ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jced.8b00806.

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REFERENCES

(1) Ferreira, A. F. P.; Santos, J. C.; Plaza, M. G.; Lamia, N.; Loureiro, J. M.; Rodrigues, A. E. Suitability of Cu-BTC extrudates for propane− propylene separation by adsorption processes. Chem. Eng. J. 2011, 167, 1−12. (2) Shi, M.; Lin, C. C. H.; Kuznicki, T. M.; Hashisho, Z.; Kuznicki, S. M. Separation of a binary mixture of ethylene and ethane by adsorption on Na-ETS-10. Chem. Eng. Sci. 2010, 65, 3494−3498. (3) Gücüyener, C.; van den Bergh, J.; Gascon, J.; Kapteijn, F. Ethane/ethene separation turned on its head: selective ethane adsorption on the metal−organic framework ZIF-7 through a gateopening mechanism. J. Am. Chem. Soc. 2010, 132, 17704−17706. (4) Aguado, S.; Bergeret, G. R.; Daniel, C.; Farrusseng, D. Absolute molecular sieve separation of ethylene/ethane mixtures with silver zeolite A. J. Am. Chem. Soc. 2012, 134, 14635−14637. (5) Masoudi-Nejad, M.; Fatemi, S. Application of zeotype SAPO-34 molecular sieve as a selective adsorbent for separation of ethylene from ethane. J. Gas Process 2014, 2, 1−7. (6) Iucolano, F.; Aprea, P.; Caputo, D.; Colella, C.; Eić, M.; Huang, Q. Adsorption and diffusion of propane and propylene in Ag+impregnated MCM-41. Adsorption 2008, 14, 241−246. (7) Chen, J. P.; Yang, R. T. Molecular orbital study of selective adsorption of simple hydrocarbons on Ag+ and Cu+ exchanged resins and halides. Langmuir 1995, 11, 3450−3456. (8) Yang, R. T. Adsorbents: Fundamentals and Applications; Wiley: Hoboken, 2003. (9) Cheng, L. S.; Yang, R. T. Monolayer cuprous chloride dispersed on pillared clays for olefin-paraffin separations by π-complexation. Adsorption 1995, 1, 61−75. (10) Hernández-Maldonado, A. J.; Yang, R. T. Desulfurization of diesel fuels by adsorption via π-complexation with vapor-phase exchanged Cu(I)-Y zeolites. J. Am. Chem. Soc. 2004, 126, 992−993. (11) McKinley, S. G.; Angelici, R. J. Deep desulfurization by selective adsorption of dibenzothiophenes on Ag+/SBA-15 and Ag+/ SiO2. Chem. Commun. 2003, 2620−2621. (12) Su, W.; Zhang, A.; Sun, Y.; Ran, M.; Wang, X. J. Adsorption properties of C2H4 and C3H6 on 11 adsorbents. J. Chem. Eng. Data 2017, 62, 417−421. (13) Gao, F.; Wang, Y. Q.; Wang, X.; Wang, S. H. Ethylene/ethane separation by CuCl/AC adsorbent prepared using CuCl2 as a precursor. Adsorption 2016, 22, 1013−1022. (14) Gao, F.; Wang, Y. Q.; Wang, S. H. Selective adsorption of CO on CuCl/Y adsorbent prepared using CuCl2 as precursor: Equilibrium and thermodynamics. Chem. Eng. J. 2016, 290, 418−427. (15) Jiang, W. J.; Sun, L. B.; Yin, Y.; Song, X. L.; Liu, X. Q. Ordered mesoporous carbon CMK-3 modified with Cu(I) for selective ethylene/ethane adsorption. Sep. Sci. Technol. 2013, 48, 968−976. (16) Hirai, H.; Wada, K.; Komiyama, M. Active carbon-supported copper(I) chloride as solid adsorbent for carbon monoxide. Bull. Bull. Chem. Soc. Jpn. 1986, 59 (7), 2217−2223. (17) Tamon, H.; Kitamura, K.; Okazaki, M. Adsorption of carbon monoxide on activated carbon impregnated with metal halide. AIChE J. 1996, 42 (2), 422−430. (18) Chang, G.; Bao, Z.; Ren, Q.; Deng, S.; Zhang, Z.; Su, B.; Xing, H.; Yang, Y. Fabrication of cuprous nanoparticles in MIL-101: an efficient adsorbent for the separation of olefin-paraffin mixtures. RSC Adv. 2014, 4, 20230−20233. (19) Ma, J.; Li, L.; Ren, J.; Li, R. CO adsorption on activated carbonsupported Cu-based adsorbent prepared by a facile route. Sep. Purif. Technol. 2010, 76, 89−93. (20) Jin, M.; Kim, S. S.; Kim, Y. D.; Park, J.-N.; Kim, J. H.; Ko, C. H.; Kim, J. N.; Kim, J. M. Redox-buffer effect of Fe2+ ions on the selective olefin/paraffin separation and hydrogen tolerance of a Cu+based mesoporous adsorbent. J. Mater. Chem. A 2013, 1, 6653−6657. (21) Rege, S. U.; Padin, J.; Yang, R. T. Olefin/paraffin separations by adsorption: π-complexation vs. kinetic separation. AIChE J. 1998, 44, 799−809.

4. CONCLUSIONS (1) The adsorption test results of four kinds of Ag+-based adsorbents at different temperatures show that the specific surface area and the loadings of Ag+ ions affect the adsorbed amount and separative performance of π-complexation adsorbents. At 303.15 K and 0.1 MPa, the ethylene/ethane of Ag−Amberlyst 35 reached the maximum of 60.8, but the ethylene adsorption capacity is relatively small, only 13.2 mL/ g. The adsorbed amount of ethylene of the three other mesoporous silica adsorbents was approximately equal, about 20 mL/g. Materials in this work have comparative equilibrium adsorption properties among recent reported results. (2) The thermodynamic analysis of ethylene and ethane on the four π-complexation adsorbents shows that the interaction of ethane with adsorbents is physical adsorption. The interaction of ethylene with the adsorbents is π-complexation adsorption. Meanwhile, the pore structure and texture of the adsorbent do not have much effect on the adsorption heat, and the trend of the adsorption heat value change reflects heterogeneous energy on the surface of the adsorbent. (3) Adsorption kinetics of ethylene on the four complexed adsorbents shows that the pseudo-second-order model has a good fitting result and is suitable for describing the adsorption kinetics of ethylene on π-complexation adsorbents. In addition, the apparent activation energy of the four adsorbents is in the range of 24 to 33 kJ/mol, which is obviously higher than CO2 chemisorption of supported amine adsorbents. The kinetics of ethylene on ordered mesoporous adsorbent is not a simple diffusion control process. Compared with the existing adsorbents, the mass transfer rate of Ag−KIT-6 is faster and the equilibrium time is shorter. This suggests that the mesoporous structure with three-dimensional regularity is conducive to mass transfer in π-complexation adsorption.

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Adsorbents characterization, adsorption isotherms, selectivity comparsion and adsorption kinetics data (PDF)

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Yagu Dang: 0000-0003-1715-3153 Author Contributions #

C.W. and J.W. contributed to the work equally and should be regarded as cofirst authors. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors are thanks to Zhang Huan, Liu Xing, and Li Shouqiang for discussion and useful advices. G



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(22) Wu, Z. B.; Han, S. S.; Cho, S. H.; Kim, J. N.; Chue, K. T.; Yang, R. T. Modification of resin-type adsorbents for ethane/ethylene separation. Ind. Eng. Chem. Res. 1997, 36, 2749−2756. (23) Yu, L.; Chu, W.; Luo, S. Z.; Xing, J. D.; Jing, F. L. Experimental Study of Silver-Loaded Mesoporous Silica for the Separation of Ethylene and Ethane. J. Chem. Eng. Data 2017, 62 (9), 2562−2569. (24) Jo, C.; Kim, K.; Ryoo, R. Syntheses of high quality KIT-6 and SBA-15 mesoporous silicas using low-cost water glass, through rapid quenching of silicate structure in acidic solution. Microporous Mesoporous Mater. 2009, 124, 45−51. (25) Jansen, J. C.; Shan, Z.; Marchese, L.; Zhou, W.; von der Puil, N.; Maschmeyer, T. A new templating method for three-dimensional mesopore networks. Chem. Commun. 2001, 713−714. (26) Zhou, L.; Zhou, Y.; Li, M.; Chen, P.; Wang, Y. Experimental and modeling study of the adsorption of supercritical methane on a high surface activated carbon. Langmuir 2000, 16, 5955−5959. (27) Wen, J.; Han, X.; Lin, H. F.; Zheng, Y.; Chu, W. A critical study on the adsorption of heterocyclic sulfur and nitrogen compounds by activated carbon: equilibrium, kinetics and thermodynamics. Chem. Eng. J. 2010, 164, 29−36. (28) Campo, M. C.; Ribeiro, A. M.; Ferreira, A.; Santos, J. C.; Lutz, C.; Loureiro, J. M.; Rodrigues, A. E. New 13X zeolite for propylene/ propane separation by vacuum swing adsorption. Sep. Purif. Technol. 2013, 103, 60−70. (29) Myers, A. L.; Prausnitz, J. M. Thermodynamics of mixed-gas adsorption. AIChE J. 1965, 11, 121−127. (30) Bahamon, D.; Vega, L. F. Systematic evaluation of materials for post-combustion CO2 capture in a Temperature swing adsorption process. Chem. Eng. J. 2016, 284, 438−447. (31) Ho, Y. S. Review of second-order models for adsorption systems. J. Hazard. Mater. 2006, 136, 681−689. (32) Serna-Guerrero, R.; Sayari, A. Modeling adsorption of CO2 on amine-functionalized mesoporous silica.2: kinetics and breakthrough curves. Chem. Eng. J. 2010, 161, 182−190. (33) Qiu, H.; Lv, L.; Pan, B. C.; Zhang, Q. J.; Zhang, W. M.; Zhang, Q. X. Critical review in adsorption kinetic models. J. Zhejiang Univ., Sci., A 2009, 10, 716−724. (34) Maghsoudi, H. Comparative study of adsorbents performance in ethylene/ethane separation. Adsorption 2016, 22, 1−8. (35) Gu, B.; Schmitt, J.; Chen, Z.; Liang, L.; McCarthy, J. F. Adsorption and desorption of natural organic matter on iron oxide: mechanisms and models. Environ. Sci. Technol. 1994, 28, 38−46. (36) Yang, R. T.; Kikkinides, E. S. New sorbents for olefin/paraffin separations by adsorption via π-complexation. AIChE J. 1995, 41, 509−517. (37) Mei, H.; Hu, C. G.; Liu, X. Q.; Yao, H. Q. Adsorption kinetics of ethylene on activated carbon loaded with Copper(I). Petrochemical Technology. 2001, 30, 228−230. (38) Lee, J.-W.; Park, J.-H.; Han, S.-S.; Kim, J.-N.; Cho, S.-H.; Lee, Y.-T. Adsorption Equilibrium and Dynamics of C4 Olefin/Paraffin on π-Complexing Adsorbent. Sep. Sci. Technol. 2005, 39, 1365−1384. (39) Xie, Y. C.; Tang, Y. Q. Spontaneous Monolayer Dispersion of Oxides and Salts onto Surfaces of Supports: Applications to Heterogeneous Catalysis. Adv. Catal. 1990, 37, 1−43.

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