Cycling and Regeneration of Adsorbed Natural Gas in Microporous

Subscriber access provided by READING UNIV

Article

Cycling and Regeneration of Adsorbed Natural Gas in Microporous Materials Jimmy Romanos, Tyler Rash, Sara Abou Dargham, Matthew Prosniewski, Fatima Barakat, and Peter Pfeifer Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.7b03119 • Publication Date (Web): 04 Dec 2017 Downloaded from http://pubs.acs.org on December 9, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Energy & Fuels is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 22 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Cycling and Regeneration of Adsorbed Natural Gas in Microporous Materials Jimmy Romanos,∗,† Tyler Rash,‡ Sara Abou Dargham,† Matthew Prosniewski,‡ Fatima Barakat,† and Peter Pfeifer‡ Department of Natural Sciences, Lebanese American University, Byblos, Lebanon, and Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211, USA E-mail: [email protected]

Abstract Adsorbed natural gas (ANG) technology is an energy efficient method for storing natural gas at room temperature and low pressure. The search for high storageperformance natural gas sorbents for gaseous fuels is currently pursued by numerous research groups worldwide. While research in this field is mainly devoted to optimize the gravimetric and volumetric storage capacity of methane, this work investigates the long-term effect of large alkanes on natural gas storage. This article investigates the evolution of storage capacity and gas composition during adsorption/desorption cycles at room temperature (charge/discharge of an ANG tank) and at various elevated temperatures (regeneration of tank) on a commercial, high-surface-area activated carbon (Maxsorb MSC-30, Kansai Coke and Chemical Co. Ltd). Cycling and regeneration study of sorbent for hundreds of cycles has been investigated. The evolution of storage capacity is measured after successive cycling using a custom-built Sievert apparatus. ∗

To whom correspondence should be addressed Department of Natural Sciences, Lebanese American University, Byblos, Lebanon ‡ Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211, USA †

1

ACS Paragon Plus Environment

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

For natural gas, gravimetric excess adsorption drops to 33% in the first 100 cycles and continues to decrease slowly until it reaches 25% by the 1000th cycle. Volumetric storage capacity shows a deterioration of 50% after 100 cycles and remains approximately constant after that. The contaminant gas composition is measured as a function of successive cycling using gas chromatography. Finally, efficient regeneration techniques have been tested to allow a continuous operation for thousands of cycles.

Introduction Compressed natural gas (CNG) and liquefied natural gas (LNG) are the conventional technologies for the storage and transport of natural gas (NG). Both technologies, however, have drawbacks including the high costs associated with compression or liquefaction as well as the large containers necessary to store CNG or LNG. Adsorbed natural gas (ANG) is a promising technology and an energy efficient method for storing NG at room temperature and low pressure. ANG technology offers several advantages over existing technologies in several aspects of the upstream and the downstream sector of the NG industry. 1,2 The usage of an adsorbent material increases the natural gas density at a given pressure and decreases the pressure at a given density. Despite the advantages of ANG, its commercialization is hindered by several technological barriers. 4,5 The United States Department of Energy (DOE) under the Advanced Research Projects Agency-Energy (ARPA-E) has initiated a research program known as Methane Opportunities for Vehicular Energy (MOVE). This program is aimed to develop sorbent materials for low pressure natural gas storage. The US DOE has set targets for natural gas storage in sorbent materials; the target for volumetric energy density is 12.5 M J/L (0.22 kg CH4 /L sorbent) and that for gravimetric energy density is 0.50 g/g. 6 Metal-Organic Frameworks (MOFs), Covalent Organic Frameworks (COFs), and Activated Carbon (AC) are currently the leading sorbent materials for natural gas storage; reaching 75 % of the volumetric target and 50 % of the gravimetric target. 7–17 Storing methane at lower temperatures improves the 2


Page 2 of 22

Page 3 of 22 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

storage density, reaching gravimetric and volumetric capacities closer to the DOE targets. 18 Figure 1 represents the sorbent performance at room temperature before packing inside a tank using the crystallographic density for MOFs and the granular (intraparticle) density for activated carbon. Various packing configurations have been developed for sorbents. 19–21 It is important to note that some sorbents materials are extremely fragile and typically collapse under the mechanical pressure needed to form monoliths, or give low energy densities inside the tank under normal packing conditions. 23 Collectively, these results suggest that many sorbents have large crystalline storage capacities but improved material packing methods are required to improve the useable storage capacity of these materials. Apart from sorbent packing, thermal management is another problem facing ANG technology. The heat of adsorption (positive) and desorption (negative) decrease the storage capacity and the delivered quantity respectively. 23,24 If a tank is filled/emptied rapidly, the tank gets very hot/cold and adsorbs/desorbs significantly less natural gas than at room temperature. If it is filled/emptied slowly, moderate departures from room temperature cause a moderate drop in storage capacity and amount delivered. Besides methane, NG contains ethane, carbon dioxide, nitrogen, and a small proportion of alkanes ranging from C3 to C7 . These large hydrocarbons can contaminate the sorbent material and reduce gas storage significantly because high molecular-weight hydrocarbons have high binding energy, and are more strongly adsorbed than methane, especially in the low pressure range. Thus, efficient regeneration techniques should be applied to allow a service life of approximately 1000 cycles. Mota and Wu et al. have conducted a theoretical study of the impact of gas composition on natural gas storage. 22,25 While most experimental work has focused on finding a direct solution using a guard bed that acts as a filter for non-methane components of natural gas, 26 very few studies in the literature have quantified the deterioration and analyzed the contaminants during the cycling process in the absence of a guard bed. 27,28 In this study, we aim to quantify the deterioration and study the remaining contaminants after successive cycling. In addition, we explore the efficiency of thermal regeneration methods on sorbents perfor-

3


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 1: Volumetric in (MJ/L) and (g/L) vs. gravimetric energy density (gCH4 /gsorbent ) at 35 bar and room temperature for MOFs (green), COFs (red), and microporous carbon MSC-30 (grey).

4


Page 4 of 22

Page 5 of 22 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

mance. An important reason to investigate performance of an ANG tank in the absence of a guard bed is because a guard bed adds significant resistance to flow (flow through a porous medium) and limits the fuel fill and discharge rate.

Experimental Materials A commercial high-surface area carbon Maxsorb MSC-30, 29–31 produced by Kansai Coke and Chemical Co. Ltd, was selected for this study. Ultra-high purity methane (99.999% purity) and the natural gas mixture described in Table 1 were used for adsorption. Table 1: Natural gas composition in mol % Components mol % CH4 85.454 C2 H6 4.849 C3 H8 0.992 i − C4 H10 (isobutane) 0.300 C4 H10 0.395 i − C5 H12 (isopentane) 0.087 C5 H12 0.079 C6 H14 0.144 N2 7.133 CO2 0.567

Sub-critical nitrogen adsorption Sub-critical nitrogen isotherms at 77 K were measured on an Autosorb Surface Analyzer (Quantachrome), which was periodically calibrated using a surface area reference material SARM 2012 (768 m2/g). The total pore volume (Vtot ) is determined by measuring the amount of nitrogen adsorbed at relative pressure P/P0 = 0.995, at which liquid nitrogen fills the entire pore space by capillary condensation. The porosity (Φ), defined as the volume

5


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 22

fraction occupied by open pores and the apparent density (ρapp ), defined as mass of the sample per volume of solid plus pore space, are calculated from: "

Vtot φ = 1 + ρskel × ms

−1 #−1 ,

(1)

and

ρapp = ρskel (1 − φ),

(2)

where ρskel is the skeletal density of the sample, assumed to be 2.0 g/cm3 . Typical skeletal densities of amorphous carbons are between 1.8 and 2.1 g/cm3 . 32 The result for the adsorbent under investigation, MSC-30, is ρapp = 0.32 g/cm3 .

Sievert Apparatus (supercritical adsorption of methane and natural gas) The performance of an adsorbent (activated carbon, MOF, ...) is determined by measuring an excess adsorption isotherm and converting excess adsorption into volumetric storage capacity by knowing the porosity of the adsorbent. The porosity is determined using the theoretical crystal density for MOFs or Equation 1 for activated carbon. Gravimetric excess adsorption is the mass of the adsorbed film minus the mass of an equal volume of gas. Dry sample mass was determined by measuring the sample mass under vacuum after heating it to 400 ◦ C for two hours under vacuum (0.027 bar). Methane gravimetric excess adsorption at 35 bar and ambient temperature (298 K) were measured using a custom-built Sievert apparatus described extensively in literature. 33–35 The gravimetric storage capacity per sample mass (g/g) is determined from the excess adsorption and the porosity (Equation 3). The volumetric storage capacity is obtained by multiplying the gravimetric storage capacity by the apparent density (Equation 4).

6


Page 7 of 22 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

mstored me ρgas = + msample msample ρskel

φ 1−φ

,

(3)

and mstored mstored = × ρapp . Vsample msample

(4)

The porosity measured by sub-critical nitrogen adsorption represents the intragranular porosity, not the porosity of a packed bed of adsorbent particles. Consequently, the gravimetric and volumetric storage capacities in this paper represent activated carbon particle performance, not the complete system performance because the void between particles is not taken into account by this method because the void between particles is not taken into account by Vtot in equation 1.

Cycling and gas chromatography Before the cycling operation, the storage vessel was outgassed for four hours at 400◦ C to remove all moisture from the sorbent. During each charging and discharging process, an equilibration time of 10 min was allowed for temperature and pressure stabilization. For each cycle, the vessel was charged from 1 bar to 35 bar then discharged from 35 bar to 1 bar. The gravimetric excess adsorption and the volumetric storage capacity were measured at 35 bar and 298 K for the 1st , 5th , 20th , 40th , 80th , 100th , 150th , 200th , 300th , 400th , 500th , 600th , 700th , 800th , 900th , and 1000th cycle. For the 100th , 500th , and 1000th cycle, the composition of the gas retained in the carbon was determined by micro-gas chromatography.

Results and discussion First, following the experimental procedure described, a cycling test was performed for pure methane and a natural gas mixture (table 1) separately. In order to examine the effect of

7


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

usage of pure methane versus that of the natural gas mixture, gravimetric excess adsorption is measured, as shown in Figure 2. It is found that, when pure methane is used for 1000 cycles, gravimetric adsorption remains around 200 g/kg, whereas, when a mixture of natural gas is used a sharp decrease from 200 to 60 g/kg, before the 100th cycle, of the gravimetric excess adsorption occurs. After the 100th cycle gravimetric excess adsorption reaches a plateau of about 50 g/kg. The nondecline (methane) and decline (natural gas) of storage

Figure 2: Gravimetric excess adsorption (g/kg) of methane (black squares) and natural gas mixture (blue circles) as function of number of cycles at T = 298 K. capacity in terms of volumetric storage capacity is shown in Figure 3, in units of g/L and 8


Page 8 of 22

Page 9 of 22 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

V/V (volume of gas at 1 bar and 298 K per volume of tank). Again, the volumetric storage capacity for pure methane remains constant, while for natural gas, volumetric storage capacity decreases from 84 g/L in the 1st cycle to 43 g/L after 100 cycles and remains constant up to the 1000th cycle. High molecular-weight hydrocarbons have a higher binding energy

Figure 3: Volumetric storage capacity in (g/L) and (V/V) of pure methane (black squares) and natural gas mixture (blue circles) as function of number of cycles at T = 298 K. than methane and thus are more strongly adsorbed. The accumulation of trace components of large hydrocarbons has a considerable impact on the performance of porous materials for long term cycling, as has been shown. Large alkanes desorption is not reversible when the pressure is reduced back to 1 bar, many pores and surfaces are still occupied by large gas molecules. 9


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

High-resolution scanning transmission electron microscopy (STEM) reported in previous work 10 shows that activated carbon grains are formed of randomly oriented stacks of corrugated carbon sheets, and modeling of the three dimensional pore structure as slit-shaped pores has proven to be a good approximation. 36 Zerner calculated the minimum dimension of slit-shaped pores through which molecules can enter. 37 He reported the critical dimensions of gas molecules by rotating the molecule to find an axis which represents the minimum distance through which the molecule can enter the pores. The minimum accessible dimension ranges from 3.0 Å for N2 to 4.0 Å for C6 H14 . The pore-size distribution of MSC-30 measured using quenched solid density functional theory (QSDFT) shows that pores widths vary from 7 Å up to 40 Å. 38 Consequently, large hydrocarbons can access all relevant pores for gas storage, and the deterioration of the storage capacity is independent of the pore-size distribution. The binding energy at zero coverage of hydrocarbons on activated carbon has been reported as 19 kJ/mol for CH4 , 26 kJ/mol for C2 H6 , 30 kJ/mol for C3 H8 , 37 kJ/mol for i-C4 H10 , 44 kJ/mol for C5 H12 , and 46 kJ/mol for C6 H14 . 39 These binding energies of hydrocarbons correlates with the measured experimental deterioration of performance due to non-reversible adsorption/desorption, as reported in Figure 4. Figure 4 shows the mole fraction of gas retained in activated carbon pores at the end of the 100th , 500th , and 1000th cycle. While the mole fraction of CH4 , C2 H6 , C3 H8 , C4 H10 , i-C4 H10 , N2 , and CO2 decreases or stays constant with cycling, the mole fraction of C5 H12 and C6 H14 accumulate with successive cycling. The experimental trends in successive cycling are in agreement with the grand canonical Monte Carlo Simulation (GCMC) simulations performed by Wu et al. 25 considering that the simulation started with a different natural gas composition in mol %: 95 % CH4 , 3.5 % C2 H6 , 0.6 % C3 H8 , 0.09% C4 H10 , 0.064% C5 H12 , 0.045% C6 H14 , 0.001% TBM, and 0.7% CO2 . Zhu et al. reported that the isosteric heat of adsorption of n-butane is larger than iso-butane, 40 this explains why the mole fraction of n-butane retained in the carbon is larger than the amount of iso-butane. Adsorption of methane at T = 298 K takes place above the liquid-gas critical temperature for methane, Tc = 190 K (supercritical adsorption).

10


Page 10 of 22

Page 11 of 22 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Figure 4: The composition of the gas retained in the activated carbon pores (mol %) after desorption to pressure of 1 bar for 100, 500, 1000 cycles in black, red, blue respectively. Under these conditions, the adsorbed film is always a monolayer, no matter how high the gas pressure is. The monolayer has the same structure during adsorption and desorption, which makes the adsorption and desorption branch of the isotherm coincide at all pressures (no hysteresis, fully reversible adsorption). Equilibration is fast, when temperature and pressure have stabilized, because the film and the one-component gas constitute a well-stirred reactor, even in micropores. For the natural gas mixture, however, the gas is no longer well-mixed because preferential adsorption of components with high binding energy creates concentration gradients in micropores that take long to equilibrate. Also, the critical temperature of large alkanes is above 298 K (305 K for C2 H6 , 370 K for C3 H8 , ...) so that multilayers of large hydrocarbons may form (subcritical adsorption) which-depending on the pore structure-may 11


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 22

have a different structure along the adsorption and desorption branch (hysteresis, capillary condensation). In this microscopic picture, repeated cycling may be thought of as serving to stir the reactor and reach equilibrium by repeated, forced gas-in/gas-out events. The operational hallmark of full equilibrium is that gravimetric excess adsorption no longer varies with the cycle number, which in Figure 3 occurs after the 500th cycle. The data in Figure 4 supports this conclusion: If we discount small differences in composition between the 500th and 1000th cycle, it appears that all concentrations, with the exception of C5 H12 and C6 H14 , remain constant between the 500th and 1000th cycle. In previous work, regeneration techniques such as thermal regeneration, steam regeneration, chemical regeneration and pressure swing regeneration have been employed to recycle spent activated carbon adsorbents. 41 Here we examine regeneration methods that can be used in situ, while the carbon remains in the ANG tank, to remove non-methane components from the carbon.Without adsorbent regeneration, gravimetric excess adsorption decreases from 200 g/kg for the 1st cycle to 66 g/kg for the 100th cycle. This decrease of 134 g/kg in storage capacity reported in Figure 2 could be reversed anywhere from 20% to 100 % by the regeneration methods listed in Table 2. Table 2: Percentage of recovered excess adsorption for several regeneration methods Regeneration methods performed after the 100th cycle

Gravimetric excess adsorp- Percentage of recovered extion after sorbent regenera- cess adsorption tion −7 No heat 2 hours vacuum ( 1.3 × 10 bar) 90 g/kg 18 % ◦ −7 100 C 2 hours vacuum ( 1.3 × 10 bar) 108 g/kg 31 % 200◦ C 2 hours vacuum ( 1.3 × 10−7 bar) 167 g/kg 75 % ◦ −7 300 C 2 hours vacuum ( 1.3 × 10 bar) 193 g/kg 95 % ◦ −7 400 C 2 hours vacuum ( 1.3 × 10 bar) 199 g/kg 99 % 400 ◦ C No vacuum 115 g/kg 37 % 2 hours nitrogen flow 106 g/kg 30% The regeneration techniques combine vacuum, heat, and nitrogen gas flow. Table 2 shows the regenerated percentage of gravimetric excess adsorption for various techniques after 100 cycles. For instance, applying vacuum at 1.3 × 10−7 bar for 2 hours without heat recovers 12


Page 13 of 22 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

18 % of the lost storage capacity. In addition, applying heat at 400 ◦ C for 2 hours without vacuum regenerates 37 % of the storage capacity. Nitrogen flow for 2 hours regenerates 30 % of the lost excess adsorption. Heating the microporous carbon at 400 ◦ C for 2 hours under vacuum of 1.3 × 10−7 bar fully regenerates the carbon and removes all adsorbed gases from the sample. The strong dependence of regeneration on outgassing pressure and temperature seen in Table 2 is in one-to-one correspondence with the strong dependence of the approach to equilibrium on how the adsorbent is charged and discharged in the cycling experiments. Gravimetric excess adsorption of microporous carbon after its periodic regeneration was studied every 100 cycles as shown in Figure 5 (volumetric storage capacity is reported in the supplementary information). This application of temperature and vacuum leads to a complete desorption of impurities accumulated in the sorbent material. The results indicate that the deterioration in storage capacity due to the presence of impurities is reversible and not affecting the structural integrity of activated carbon permanently.

13


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 5: Periodic regeneration of activated carbon for every 100 cycles.

14


Page 14 of 22

Page 15 of 22 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Conclusion In this work we have studied the impact of gas composition on the cyclic behavior of adsorptive natural gas system. Gravimetric excess adsorption and volumetric storage capacity were measured for pure methane and natural gas mixture. While for pure methane, storage capacity did not present any variation, for natural gas, the performance decreased with the number of cycles. Gravimetric excess adsorption decreased to 33% after 100 cycles and continued to decrease slowly until it reached 25% by the 1000th cycle. Volumetric storage capacity decreased to 50% after the first 100 cycles and remained constant after that. The composition of remained gas at the end of the 100th , 500th and 1000th cycle was determined after desorption and showed that heavier gas molecules retained in carbon accumulate with successive cycling. To reduce the accumulation of impurities in ANG systems and extend effective delivery of natural gas to a larger number of cycles, regeneration experiments were performed. Periodic regeneration through outgassing at 400◦ C for 2 hours showed that the adsorption was completely reversed and we were able to reactivate carbon and remove the impurities from the sample.

Acknowledgement This work is supported in part by the Lebanese National Council for Scientific Research (CNRS-L) and the Lebanese American University (LAU) under LAU fund number SRDCf201423.

Supporting Information Available In the supporting information, we report the pore-size distribution of MSC-30 measured using subcritical nitrogen adsorption at 77 K. Quenched solid-density functional theory (QSDFT) for infinite slit-shaped pores is used for calculating the pore-size distribution. In addition, we report the periodic regeneration in terms of volumetric storage capacity of MSC-30 every

15


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

100 cycles. This material is available free of charge via the Internet at http://pubs.acs.org/.

16


Page 16 of 22

Page 17 of 22 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

References (1) Kumar, K. V.; Preuss, K.; Titirici, M.-M.; Rodríguez-Reinoso, F., Nanoporous Materials for the Onboard Storage of Natural Gas. Chemical reviews 2017, 117 (3), 1796-1825. (2) Vasiliev, L. L.; Kanonchik, L. E.; Mishkinis, D. A.; Rabetsky, M. I., Adsorbed natural gas storage and transportation vessels. International Journal of Thermal Sciences 2000, 39 (9), 1047-1055. (3) Pfeifer, P; Little R.; Rash, T; Romanos,J.; Maland,B , Advanced Natural Gas Fuel Tank Project. California Energy Commission, Energy Research and Development Division, Publication No. CEC-500-2016-038 (Sacramento, CA, 2016). (4) Ybyraiymkul, D. ; Ng, K. C.; Kaltayev, A., Experimental and numerical study of effect of thermal management on storage capacity of the adsorbed natural gas vessel. Applied Thermal Engineering 2017, 125, 523-531. (5) Alhasan, S.; Carriveau, R.; Ting, D.-K., A review of adsorbed natural gas storage technologies. International Journal of Environmental Studies 2016, 73 (3), 343-356. (6) ARPA-E

Methane

Opportunities

for

Vehicular

Energy.

https://arpa-

e.energy.gov/?q=arpa-e-programs/move (7) Peng, Y.; Krungleviciute, V.; Eryazici, I.; Hupp, J. T.; Farha, O. K.; Yildirim, T., Methane Storage in Metal-Organic Frameworks: Current Records, Surprise Findings, and Challenges. Journal of the American Chemical Society 2013, 135 (32), 1188711894. (8) Gándara, F.; Furukawa, H.; Lee, S.; Yaghi, O. M., High Methane Storage Capacity in Aluminum Metal-Organic Frameworks. Journal of the American Chemical Society 2014, 136 (14), 5271-5274.

17


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(9) Jiang, J.; Furukawa, H.; Zhang, Y.-B.; Yaghi, O. M., High Methane Storage Working Capacity in Metal-Organic Frameworks with Acrylate Links. Journal of the American Chemical Society 2016, 138 (32), 10244-10251. (10) Romanos, J.; Sweany, S.; Rash, T.; Firlej, L.; Kuchta, B.; Idrobo, J. C.; Pfeifer, P., Engineered Porous Carbon for High Volumetric Methane Storage. Adsorption Science & Technology 2014, 32 (8), 681-692. (11) He, Y.; Zhou, W.; Qian, G.; Chen, B., Methane storage in metal-organic frameworks. Chemical Society Reviews 2014, 43 (16), 5657-5678. (12) Li, B.; Wen, H.-M.; Wang, H.; Wu, H.; Yildirim, T.; Zhou, W.; Chen, B., Porous metal-organic frameworks with Lewis basic nitrogen sites for high-capacity methane storage. Energy & Environmental Science 2015, 8 (8), 2504-2511. (13) Fu, J.; Tian, Y.; Wu, J., Seeking metal organic frameworks for methane storage in natural gas vehicles. Adsorption 2015, 21 (6-7), 499-507. (14) Mason, J. A.; Oktawiec, J.; Taylor, M. K.; Hudson, M. R.; Rodriguez, J.; Bachman, J. E.; Gonzalez, M. I.; Cervellino, A.; Guagliardi, A.; Brown, C. M.; Llewellyn, P. L.; Masciocchi, N.; Long, J. R., Methane storage in flexible metal-organic frameworks with intrinsic thermal management. Nature 2015, 527 (7578), 357-361. (15) Zhou, W., Methane storage in porous metal-organic frameworks: current records and future perspectives. The Chemical Record 2010, 10 (3), 200-204. (16) Wu, H.; Zhou, W.; Yildirim, T., High-Capacity Methane Storage in Metal-Organic Frameworks M2(dhtp): The Important Role of Open Metal Sites. Journal of the American Chemical Society 2009, 131 (13), 4995-5000. (17) Furukawa, H.; Cordova, K. E.; O’Keeffe, M.; Yaghi, O. M., The Chemistry and Applications of Metal-Organic Frameworks. Science 2013, 341 (6149), 1230444. 18


Page 18 of 22

Page 19 of 22 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

(18) B. Li, H.-M. Wen, W. Zhou , Jeff Q. Xu, and B. Chen, Porous Metal-Organic Frameworks: Promising Materials for Methane Storage, Chem, vol. 1, pp. 557-580 2016. (19) Lozano-Castelló, D.; Cazorla-Amorós, D.; Linares-Solano, A.; Quinn, D. F., Activated carbon monoliths for methane storage: influence of binder. Carbon 2002, 40 (15), 2817-2825. (20) Muto, A.; Bhaskar, T.; Tsuneishi, S.; Sakata, Y.; Ogasa, H., Activated Carbon Monoliths from Phenol Resin and Carbonized Cotton Fiber for Methane Storage. Energy & Fuels 2005, 19 (1), 251-257. (21) Biloé, S.; Goetz, V.; Guillot, A., Optimal design of an activated carbon for an adsorbed natural gas storage system. Carbon 2002, 40 (8), 1295-1308. (22) Mota, J. P. B., Impact of gas composition on natural gas storage by adsorption. AIChE Journal 1999, 45 (5), 986-996. (23) Rash, T. A.; Gillespie, A.; Holbrook, B. P.; Hiltzik, L. H.; Romanos, J.; Soo, Y. C.; Sweany, S.; Pfeifer, P., Microporous carbon monolith synthesis and production for methane storage. Fuel 2017, 200, 371-379. (24) Sáez, A.; Toledo, M., Thermal effect of the adsorption heat on an adsorbed natural gas storage and transportation systems. Applied Thermal Engineering 2009, 29 (13), 2617-2623. (25) Wu, Y.; Tang, D.; Verploegh, R. J.; Xi, H.; Sholl, D. S., Impacts of Gas Impurities from Pipeline Natural Gas on Methane Storage in Metal-Organic Frameworks during Long-Term Cycling. The Journal of Physical Chemistry C 2017, 121 (29), 15735-15745. (26) Esteves, I. A.; Lopes, M. S.; Nunes, P. M.; Mota, J. P., Adsorption of natural gas and biogas components on activated carbon. Separation and Purification Technology 2008, 62 (2), 281-296. 19


Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(27) Pupier, O.; Goetz, V.; Fiscal, R., Effect of cycling operations on an adsorbed natural gas storage. Chemical Engineering and Processing: Process Intensification 2005, 44 (1), 71-79. (28) Cook, T. L.; Komodromos, C.; Quinn, D. F.; Ragan, S., CHAPTER 9 - Adsorbent Storage for Natural Gas Vehicles A2 - Burchell, Timothy D. Carbon Materials for Advanced Technologies, Elsevier Science Ltd: Oxford 1999; pp 269-302. (29) Bénard, P.; Chahine, R., Storage of hydrogen by physisorption on carbon and nanostructured materials. Scripta Materialia 2007, 56 (10), 803-808. (30) Nishihara, H.; Hou, P.-X.; Li, L.-X.; Ito, M.; Uchiyama, M.; Kaburagi, T.; Ikura, A.; Katamura, J.; Kawarada, T.; Mizuuchi, K.; Kyotani, T., High-Pressure Hydrogen Storage in Zeolite-Templated Carbon. Journal of Physical Chemistry C 2009, 113 (8). (31) Otowa, T.; Tanibata, R.; Itoh, M., Production and adsorption characteristics of MAXSORB: High-surface-area active carbon. Gas Separation & Purification 1993, 7 (4), 241-245. (32) CRC Handbook of Chemistry and Physics: A Ready-Reference of Chemical and Physical Data, 85th ed Edited by David R. Lide (National Institute of Standards and Technology). CRC Press LLC:âĂĽ Boca Raton, FL. 2004. ISBN 0-8493-0485-7. Journal of the American Chemical Society 2005, 127 (12), 4542-4542. (33) Nakai, K.; Sonoda, J.; Iegami, H.; Naono, H., High Precision Volumetric Gas Adsorption Apparatus. Adsorption 2005, 11 (1), 227-230. (34) Policicchio, A.; Maccallini, E.; Kalantzopoulos, G.; Cataldi, U.; Abate, S.; Desiderio, G.; Agostino, R., Volumetric apparatus for hydrogen adsorption and diffusion measurements: Sources of systematic error and impact of their experimental resolutions. Review of Scientific Instruments 2013, 84 (10), 103907.

20


Page 20 of 22

Page 21 of 22 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

(35) Beckner, M.; Dailly, A., A pilot study of activated carbon and metal-organic frameworks for methane storage. Applied Energy 2016, 162, 506-514. (36) Jagiello, J.; Olivier, J.P., 2D-NLDFT adsorption model for carbon slit-shaped pores with surface energetical heterogeneity and geometrical corrugation. Carbon 2013, 55,70-80 (37) Webster, C. E.; Drago, R. S.; Zerner, M. C., Molecular Dimensions for Adsorptives. Journal of the American Chemical Society 1998, 120 (22), 5509-5516. (38) Kuchta, B.; Firlej, L.; Mohammadhosseini, A.; Boulet, P.; Beckner, M.; Romanos, J.; Pfeifer, P., Hypothetical high-surface-area carbons with exceptional hydrogen storage capacities: open carbon frameworks. Journal of the American Chemical Society 2012, 134 (36), 15130-15137. (39) Cheripally, G. S.; Mannava, A.; Kumar, G.; Gupta, R.; Saha, P.; Mandal, B.; Uppaluri, R.; Gumma, S.; Ghoshal, A. K., Measurement and Modeling of Adsorption of Lower Hydrocarbons on Activated Carbon. Journal of Chemical &Engineering Data 2013, 58 (6), 1606-1612. (40) Zhu, W.; Groen, J. C.; Kapteijn, F.; Moulijn, J. A., Adsorption of butane isomers and SF6 on Kureha activated carbon: 1. Equilibrium. Langmuir 2004, 20 (13), 5277-5284. (41) Bagreev, A.; Rahman, H.; Bandosz, T. J., Thermal regeneration of a spent activated carbon previously used as hydrogen sulfide adsorbent. Carbon 2001, 39 (9), 1319-1326.

21


Energy & Fuels

Graphical TOC Entry Cycling and Regeneration of Adsorbed Natural Gas in Microporous Materials J. Romanos et al. 400 οC and 2 hours vacuum (up to 10-4 torr)

220

Gravimetric Excess Adsorption (g/Kg)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 22

200 180 160 CO2

140

N2

120

The composition of the gas retained in the pores for the 100th cycles

C 6H 14 C5 H12

100

i-C5 H12

80

C4 H10

60

i-C4 H10

40

C 3H 8 C2 H6

20

CH 4

0 0

100

200

300

400

500

0

5

10

15

20

Mol %

Cycles

22


25

30

35

40

Cycling and Regeneration of Adsorbed Natural Gas in Microporous

Recommend Documents