Article Cite This: J. Chem. Eng. Data XXXX, XXX, XXX−XXX
pubs.acs.org/jced
Adsorption Properties of N2O on Zeolite 5A, 13X, Activated Carbon, ZSM-5, and Silica Gel Tongbo Wu, Yuanhui Shen, Li Feng, Zhongli Tang, and Donghui Zhang* The Research Center of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
Downloaded via BUFFALO STATE on July 30, 2019 at 04:13:50 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.
S Supporting Information *
ABSTRACT: The adsorption isotherms of nitrous oxide (N2O) on zeolite 5A, 13X, activated carbon, ZSM-5, and silica gel were investigated by a static volumetric method. The pressure and temperature by measurement of adsorption isotherms ranged from 0 to 1 MPa and 298 to 358 K, respectively. In terms of the adsorption amount, zeolite 13X has the highest adsorption capacity at high pressure (>0.7 MPa), while activated carbon has the best performance at low pressure (30 vol %) © XXXX American Chemical Society
in adipic acid plants and diluted N2O streams (0.05 to 0.2 vol %) in nitric acid plants.13 The reutilization of N2O can be used as a selective and valuable oxidant in the environmentally benign and sustainable industrial manufacture producing fine and intermediate chemicals, such as phenol (from benzene) or methanol (from methane).5,14 Adsorbents are significant and necessary for the adsorption process applied in the separation and recovery of gases. The adsorption isotherms of N2O on silicalite-1 were measured at temperatures ranging from 273 to 398 K and pressure up to 0.120 MPa using a volumetric method by Groen et al., and the Henry’s law constant and enthalpy were calculated to characterize the interaction between adsorbate and adsorbent.6 Peng et al. reported the adsorption of N2O on three different activated carbons at the temperature range of 195 to 323 K and pressure range from 0.00001 to 0.101 MPa, and the thermodynamic properties such as the adsorption equilibrium constant and enthalpy were also calculated.13 The N2O adsorption capacities on MOF-5, MOF-177, and zeolite 5A were measured gravimetrically by Saha et al.15 In addition, the Henry’s law constant and adsorption kinetics were obtained at 298 K and equilibrium pressure up to 1 MPa. Their results demonstrated that zeolite 5A was a better adsorbent for removing N2O from air and the average diffusivity of N2O in MOF-5 and MOF-177 were both 10−9 m2/s, as compared to 10−11 m2/s in 5A. Furthermore, Saha et Received: March 28, 2019 Accepted: July 3, 2019
A
DOI: 10.1021/acs.jced.9b00272 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
Journal of Chemical & Engineering Data
Article
Figure 1. N2 adsorption and desorption isotherms of (a) 13X, (b) 5A, (c) AC, (d) silica gel, and (e) ZSM-5 at 77 K.
activated carbon (AC), ZSM-5, and silica gel. The adsorption isotherms measured by the volumetric method and the isosteric heat of N2O were investigated in the range of 298 to 358 K and at pressure up to 1 MPa.
al. also measured the adsorption equilibrium, kinetics, and enthalpy of N2O on zeolites 4A and 13X at temperatures of 194, 237, and 298 K and equilibrium pressure up to 0.108 MPa.16 It was found that the adsorption capacity of N2O on 4A was higher than that of 13X, and the adsorption heat of 4A and 13X ranged from 21 to 33 kJ/mol, with adsorption loadings between 0.5 and 3.5 mmol/g. The adsorption isotherm of N2O was scarce, especially at high pressure and temperature in the published literature. Therefore, in this work, the adsorption properties of N2O on five adsorbents were determined, including zeolite 5A, 13X,
2. EXPERIMENTAL SECTION 2.1. Adsorbents. Five adsorbents were used in this work. The molecular sieves 5A (HYGB500A type) and 13X (HYZ10E type) were purchased from Shanghai Hengye Molecular Sieve Company. ZSM-5 was obtained from the B
DOI: 10.1021/acs.jced.9b00272 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
Journal of Chemical & Engineering Data
Article
Figure 2. Pore size distribution of (a) 13X, (b) 5A, (c) AC, (d) silica gel, and (e) ZSM-5.
into columns with coal tar as a binder. The columnar raw coal was heated at 1073 K for 40 min with a N2 flow of 300 mL/ min and a heating rate of 10 K/min. The black columnar coal was activated using a water vapor flow of 1500 mL/min at 1123 K for 2.5 h. Finally, they were washed with deionized water and then dried at 373 K overnight. In terms of the shape and size, the obtained cylindrical activated carbon had an average diameter of 0.8 mm and an average height of 3.1 mm, and the average pellet size of the silica gel was 1.75 mm according to characterization. The average sphere diameters of 13X, 5A, and ZSM-5 were all 1.70 mm obtained from the manufacturers’ reports. To characterize the five adsorbents, the
NanKai catalyst plant. The silica gel and activated carbon were synthesized in our lab. Silica gel was prepared by a sol−gel method. The sodium silicate solution with Na2O content of 5.2 wt % and a dilute sulfuric acid solution having a concentration of 20 wt % reacted at a certain pH to form a gel, which formed into a spherical silicone gel in hot oil. Then, the spherical silicone gel was immersed in 5 wt % sulfuric acid for 6 h and washed with water, which can result in a silica gel product with an average pore diameter of 2.554 nm. Additionally, all products would be dried first and then activated at 823 K for 20 min. High-quality coal was used as the raw material for preparing activated carbon. The pulverized coal was extruded C
DOI: 10.1021/acs.jced.9b00272 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
Journal of Chemical & Engineering Data
Article
respectively. The adsorption isotherms were measured at four different temperatures of 298, 318, 338, and 358 K, and the pressure was up to 1 MPa.
N2 adsorption and desorption isotherms were measured with a Micromeritics ASAP 2020 instrument, and the results are depicted in Figure 1. The pore size distribution was calculated using N2 adsorption isotherm data at 77 K using BJH (Barrett−Joyner−Halenda) and HK (Horvath−Kawazoe) methods, and the results are displayed in Figure 2. The BET (Brunauer−Emmett−Teller) surface, pore volumes, and average pore sizes are listed in Table 1.
3. RESULTS AND DISCUSSION 3.1. Adsorption Isotherms. Adsorption isotherms of N2O on five adsorbents at 298, 318, 338, and 358 K are shown in Figure 2. It can be found that the adsorption isotherms of N2O on ZSM-5, 5A, and 13X are type I at the investigated temperature and pressure, whereas those of the silica gel is close to linear. Adsorption isotherms of N2O on activated carbon are more likely to be type II rather than type I based on the measured adsorption data according to the BDDT classification17 from Figure 4. Diagrams a−e in Figure 4 show that for all adsorbents, the amount adsorbed increases with the equilibrium pressure increasing and temperature decreasing. The variation of adsorption capacity on 13X and 5A is drastic at low pressure (0.7 MPa) compared to activated carbon, silica gel, and ZSM-5. It can be found that the effect of pressure on N2O adsorption capacity is pronounced on all adsorbents at low pressure. Meanwhile, the impact of temperature on the adsorption capacity is greater than pressure at high pressure, especially for 13X and 5A. Furthermore, the adsorption capacities on 13X and 5A almost reached a plateau at high equilibrium pressure, but the adsorption capacity of other adsorbents, especially on the silica gel, continued to maintain a linear growth trend. The adsorption capacity of N2O on different adsorbents at low pressure ( 13X > activated carbon > ZSM-5 > silica gel under the same conditions at 358, 338, and 318 K. The N2O adsorption capacity on 13X and 5A at all temperatures is much higher than that on other adsorbents when the pressure is lower than 0.1 MPa. However, the amount of N2O on 13X exceeds that on 5A under an equilibrium pressure of 0.1 MPa at 298 K from Figure 5. The adsorption amount at 298 K at 0.1 MPa is 4.01 mmol/g for 13X, as compared to 3.72 mmol/g for 5A, 2.39
Table 1. Textural Properties of the Adsorbents adsorbent
SBET (m2/g)
Vtotal (cm3/g)
average pore size (nm)
5A 13X AC ZSM-5 silica gel
579.7 529.5 904.4 241.3 759.5
0.2573 0.4251 0.5025 0.2586 0.4850
1.776 3.212 2.227 4.286 2.554
2.2. Adsorption. The static volumetric technique was applied to measure adsorption isotherms of N2O on the five adsorbents according to the change of pressure, which was based on the ideal gas law. Schematic representation of the equipment is shown in Figure 3. The experimental apparatus mainly consists of a vacuum pump, a water bath, a pressure transducer, and two containers of known volume. The pressure transmitter with a maximum limit of 2 MPa (uncertainty, 0.7 MPa). All isotherms were fitted by the Langmuir, Langmuir−Freundlich, and Toth models, and the results showed that the Langmuir−Freundlich model was the best in fitting isotherm data. The isosteric heat of adsorption was calculated with varied adsorbed amount on different adsorbents. The isosteric heat first decreases then increases with an increase of adsorbed amount on all adsorbents. The order of the isosteric heat on investigated adsorbents was as follows: 5A > 13X > ZSM-5 > AC ≈ silica gel.
Figure 7. Isosteric heat of N2O on AC, 13X, 5A, ZSM-5, and silica gel.
tions. The Clausius−Clapeyron equation was used to calculate the isosteric heat of adsorption. It is given as eq 6. ΔH i ∂ ln P yz zz = −jjj 2 RT k ∂T {q
(6)
Then, the integration of eq 6 is given as follows: ln p =
ΔH +C RT
(7)
and Q st = −ΔH
■
(8)
where T (K) is the temperature, R is the ideal gas constant where its value is 8.314 J/(mol·K), and C is an integral constant. P (MPa) is the equilibrium pressure, ΔH (kJ/mol) is the enthalpy change, and Qst (kJ/mol) is the isosteric heat. The relationship between ln P and 1/T of all adsorbents at different adsorption amount conditions was plotted in Figure 6 according to eq 7, and the fitting data were obtained by the Langmuir−Freundlich equation. It is concluded that there is a clear linear correlation between ln P and 1/T. Based on the fitting results, the slope of linear plots of ln P versus 1/T was brought into eq 7 and used to calculate the isosteric heat. Figure 7 shows the isosteric heats of five adsorbents at different adsorbed amounts in the investigated temperature. As can be seen in Figure 7, the isosteric heats of N2O on five adsorbents decrease first and then increase. It could be speculated that the five adsorbents are heterogeneous by the parameter n in the L-F equation, resulting in characterized adsorption sites with different energies on their surface. At the beginning of adsorption, N2O preferentially adsorbs at sites with higher energy and releases energy in the form of heat due to the interaction between the adsorbent surface and N2O. Then, the sites with lower energy are gradually occupied by N2O with the adsorption amounts increasing, and simultaneously, the heat of adsorption decreases gradually. The adsorbate−adsorbate interaction that has been ignored gradually appears when the adsorption amount reaches a certain level on adsorbents.21 Therefore, the isosteric heat of adsorption increases. The isosteric heat on 5A at low loading sustains a drastic reduced trend from 66.0 to 35.6 kJ/mol. Meanwhile, the isosteric heat magnitude of N2O on 5A is considerably higher than those of other adsorbents at the same
ASSOCIATED CONTENT
* Supporting Information S
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jced.9b00272. Adsorption data, fitting figures of isotherm with three models, and isosteres of adsorption (PDF)
■
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Donghui Zhang: 0000-0002-7378-100X Notes
The authors declare no competing financial interest.
■
REFERENCES
(1) Rodhe, H. A comparison of the contribution of various gases to the greenhouse effect. Science 1990, 248, 1217−1219. (2) Thiemens, M. H.; Trogler, W. C. Nylon Production: An Unknown Source of Atmospheric Nitrous Oxide. Science 1991, 251, 932−932. (3) Hu, Z; Lee, J. W.; Chandran, K; Kim, S; Khanal, S. K. Nitrous oxide (N2O) emission from aquaculture: a review. Environ. Sci. Technol. 2012, 46, 6470−6470. (4) Ravishankara, A. R.; Daniel, J. S.; Portmann, R. W. Nitrous Oxide (N2O): The Dominant Ozone-Depleting Substance Emitted in the 21st Century. Science 2009, 326, 123−125. (5) Panov, G. I. Advances in oxidation catalysis: oxidation of benzene to phenol by nitrous Oxide. CATTECH 2000, 4, 18−31. (6) Groen, J. C.; Pérez-Ramírez, J.; Zhu, W. Adsorption of Nitrous Oxide on Silicalite-1. J. Chem. Eng. Data 2002, 47, 587−589. I
DOI: 10.1021/acs.jced.9b00272 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
Journal of Chemical & Engineering Data
Article
(7) Suárez, S.; Yates, M.; Petre, A. L. Development of a new Rh/ TiO2−sepiolite monolithic catalyst for N2O decomposition. Appl. Catal., B 2006, 64, 302−311. (8) Li, Y.; Armor, J. N. Catalytic Decomposition of Nitrous Oxide on Metal Exchanged Zeolites. Appl. Catal., B 1992, 1, L21−L29. (9) Kapteijn, F. Kinetic Analysis of the Decomposition of Nitrous Oxide over ZSM-5 Catalysts. J. Catal. 1997, 167, 256−265. (10) Zeng, H. C.; Pang, X. Y. Catalytic decomposition of nitrous oxide on alumina-supported ruthenium catalysts Ru/Al2O3. Appl. Catal., B 1997, 13, 113−122. (11) Yuzaki, K.; Yarimizu, T.; Aoyagi, K. Catalytic decomposition of N2O over supported Rh catalysts: effects of supports and Rh dispersion. Catal. Today 1998, 45, 129−134. (12) Xue, L.; Zhang, C.; He, H. Catalytic decomposition of N2O over CeO2 promoted Co3O4 spinel catalyst. Appl. Catal., B 2007, 75, 167−174. (13) Peng, Y.; Zhang, F.; Xu, C.; Xiao, Q.; Zhong, Y.; Zhu, W. Adsorption of Nitrous Oxide on Activated Carbons. J. Chem. Eng. Data 2009, 54, 3079−3081. (14) Hoelderich, W. F. Environmentally benign manufacturing of fine and intermediate chemicals. Catal. Today 2000, 62, 115−130. (15) Saha, D.; Bao, Z.; Jia, F.; Deng, S. Adsorption of CO2, CH4, N2O and N2 on MOF-5, MOF-177 and zeolite 5A. Environ. Sci. Technol 2010, 44, 1820−1826. (16) Saha, D.; Deng, S. Adsorption Equilibrium, Kinetics, and Enthalpy of N2O on Zeolite 4A and 13X. J. Chem. Eng. Data 2010, 55, 3312−3317. (17) Gregg, S. J.; Sing, K. S. W. Adsorption, Surface Area and Porosity; Academic Press: London, 1982. (18) Do, D. D. Adsorption analysis: equilibria and kinetics; Imperial College Press: London, 1998. (19) Ye, Z. H.; Chen, D.; Pan, Z. J.; Zhang, G. Q.; Xia, Y.; Ding, X. An improved Langmuir model for evaluating methane adsorption capacity in shale under various pressures and temperatures. J. Nat. Gas Sci. Eng. 2016, 31, 658−680. (20) Nam, G.-M.; Jeong, B.-M.; Kang, S.-H.; Lee, B.-K.; Choi, D.-K. Equilibrium isotherms of CH4, C2H6, C2H4, N2, and H2 on zeolite 5A using a static volumetric method. J. Chem. Eng. Data 2005, 50, 72−76. (21) Zheng, Y.; Li, Q.; Yuan, C.; Tao, Q.; Zhao, Y.; Zhang, G.; Liu, J.; Qi, G. Thermodynamic analysis of high-pressure methane adsorption on coal-based activated carbon. Fuel 2018, 230, 172−184.
J
DOI: 10.1021/acs.jced.9b00272 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
