Adsorptive Removal of Dichloromethane Vapor on FAU and MFI

(10,11,15,16,19−22) However, it has been recognized that activated carbon ..... desorption of water, in situ DRIFTS, and DFT calculation are availab...
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Adsorptive Removal of Dichloromethane Vapor on FAU and MFI Zeolites: Si/Al Ratio Effect and Mechanism Shunyu Kang,†,‡ Jinzhu Ma,†,‡,§ Qinming Wu,∥ and Hua Deng*,† †

Center for Excellence in Regional Atmospheric Environment, Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China ‡ University of Chinese Academy of Sciences, Beijing 100049, China § Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China ∥ Key Lab of Applied Chemistry of Zhejiang Province and Department of Chemistry, Zhejiang University, Hangzhou 310007, China S Supporting Information *

ABSTRACT: MFI zeolites (ZSM-5) with different Si/Al ratios were synthesized to assess their adsorptive removal of dichloromethane vapor, compared with FAU zeolites (NaX and NaY). All adsorbents were characterized by means of N2 adsorption, X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The adsorption and desorption performance, water vapor tolerance, and regeneration ability were fully examined. FAU zeolites exhibited better equilibrium capacity than MFI zeolites, while MFI zeolites had superior dynamic capacity. The kinetic uptake of FAU zeolites was significantly depressed by low humidity levels in the mixture. Regardless of the type of zeolite, high Si content was not only beneficial to equilibrium adsorption but also helpful for water vapor resistance. ZSM-5 (200) (SiO2/Al2O3 = 200) with the highest Si/Al ratio was the best candidate in this study for removal of dichloromethane. In addition, it could be reused without a significant decrease in uptake after several regeneration cycles. With the aid of in situ diffuse reflectance Fourier transform infrared spectroscopy and density functional theory simulation, adsorbed dichloromethane was found to be in intimate contact with the pore window of FAU zeolites but was surrounded by the pore walls of MFI zeolites. Experimental and theoretical results were consistent with each other and indicated that MFI zeolites show better adsorptive selectivity of dichloromethane (DCM) over water than FAU. VOCs.10,11,15,16,19−22 However, it has been recognized that activated carbon frequently encounters problems such as combustion, pore blocking, and hygroscopicity. As a result, alternative adsorbents have drawn more and more interest. Metal−organic frameworks (MOFs),13,23−25 hyper-cross-linked polymers,26,27 and zeolites8,28−30 are also being considered for adsorptive removal of DCM. Zeolites have proven to be advantageous for the control of chlorinated VOCs due to their nonflammable nature, thermal stability, and hydrophobic characteristics.28−30 Schaaf et al.8 have used a 3 Å molecular sieve to separate DCM from water by the steric effect. Mesoporous silicate MCM-48 has been applied to adsorb DCM in order to design adsorption-based or catalytic processes for the disposal of wastes containing chlorinated VOCs.28 Clausse et al.29 have reported that dealuminated FAU zeolites appear to be very good adsorbents for chlorinated VOCs, including DCM. This zeolite has the great advantage of being regenerable at low temperature without destroying the material.

1. INTRODUCTION The emission of volatile organic compounds (VOCs) from anthropogenic sources poses direct and indirect hazards to both human beings and the atmospheric environment.1−6 It has been reported that VOC emissions in China are projected to continuously increase from 19.4 Tg in 2005 to 25.9 Tg in 2020 and that solvent utilization would become the largest contributor, rising from 22% to 37%.7 Thus, reduction of vapor discharge from solvent sources is quite urgent. Dichloromethane (DCM) is extensively used as a solvent in many chemical processes. The annual world production of DCM is more than 500 000 tons,8 of which about 77% is emitted into the atmosphere.9 Due to its high toxicity and carcinogenic character, combined with its contribution to global warming, depletion of the ozone layer, and the formation of photochemical smog, the removal of DCM is a major environmental concern.8−12 Among the available removal technologies for chlorinated VOCs such as DCM that are emitted into air, adsorption is a wellestablished and effective technique for their removal and recovery from exhaust.12−18 Activated carbon adsorption is widely used in industry due to ease of operation, low operating cost, and efficient recovery for most chlorinated © XXXX American Chemical Society

Received: March 5, 2018 Accepted: May 9, 2018

A

DOI: 10.1021/acs.jced.8b00174 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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where q is the adsorbed amount per unit weight of adsorbent (mmol g−1); p is the adsorbate gas pressure at equilibrium (kPa); qm and b are common parameters for the Langmuir and Toth isotherm equations; and t is an additional parameter for the Toth model. 2.3. Breakthrough Measurements. A gaseous mixture of CH2Cl2 (5000 ppm) in N2 balance at a mass flow of 100 mL min−1 was fed into a self-made fixed bed reactor. The adsorption capacity was measured in the instrument, where 0.3 g of adsorbent was packed in the bed. Prior to all adsorption measurements, samples were pretreated at 200 °C overnight. In order to investigate the effect of water vapor on the adsorption behavior, the relative humidity (RH) of the feed gas was adjusted to 30%, 50%, and 90% and passed through the adsorption bed, respectively. The concentrations of CH2Cl2 were analyzed online by an Ametek LC-D200 M PRO mass spectrometer at m/z ratios of 49 and 84, respectively. To quantitatively elucidate the adsorption kinetics, the breakthrough curves were fitted using the Yoon and Nelson model (Y−N model), expressed as the following equation

The adsorption characteristics of chloroform (CHCl3) vapor on FAU with different Si/A1 ratio were also measured by Kawai et al.31 The adsorption capability decreased with increasing Si/Al ratio. FAU and MFI zeolites are the most common zeolites in application for adsorption and catalysis. To the best of our knowledge, there have been few studies on the effect of their structures and Si to Al ratios in the adsorptive removal of DCM. In addition, the influence of water vapor on DCM adsorptive removal has not been addressed either. In this study, FAU and MFI zeolites with different Si/Al ratios were compared in the adsorptive removal of DCM. The effects of water vapor and space velocity together with the stability of the zeolites were examined. With the aid of in situ diffuse reflectance Fourier transform infrared spectroscopy and density functional theory simulation, the relationship between the zeolite structure and adsorption performance was revealed.

2. MATERIALS AND METHODS 2.1. Materials Preparation. FAU zeolite: NaX (SiO2/Al2O3 = 2) and NaY (SiO2/Al2O3 = 5) zeolites were purchased from the catalyst plant of Nankai University, Tianjin, China. MFI zeolite: Na-ZSM-5 zeolite with different SiO2/Al2O3 ratios (25, 80, 200) was synthesized according to Prof. Xiao’s routine.32−34 The details are listed as follows: a certain amount of NaAlO2 was dissolved in 6.675 mL of water, followed by the addition of 2.77 g of TPAOH. After stirring at room temperature for 15 min, 2.355 g of TEOS was added into the mixture. After stirring at room temperature for 5−6 h, the mixture was transferred to an autoclave and heated at 180 °C for 4 days for crystallization. The product was collected by centrifugation, washed with water, dried in air, and calcined at 550 °C for 5 h to remove the organic templates. The SiO2/Al2O3 ratio was controlled by the amount of NaAlO2:

Ci 1 = C0 1 + exp[k(τ0 − t )]

where Ci and C0 are the outlet and inlet initial concentrations of the stream through the fixed bed column (ppm); τ0 is the time required for 50% adsorbate breakthrough (min); and k is a rate constant that depends on the diffusion characteristics of the mass transfer zone (min−1). It is a simple model that can simulate breakthrough curves well and has been previously used for modeling the adsorption of volatile organic compounds.10,38,39 In order to investigate the desorption process, temperatureprogrammed desorption of DCM (DCM-TPD) measurements was carried out. The samples were saturated by DCM adsorption at 30 °C. Then the flow gas was changed to pure nitrogen for 0.5 h, followed by temperature ramping to 250 °C at a linear rate of 10 °C min−1. 2.4. Characterization. X-ray powder diffraction patterns of the various adsorbents were collected on a wide-angle X’Pert Pro XRD diffractometer (Panalytical B.V., Netherlands). The patterns were run with Cu Kα radiation (λ = 1.5406 Å) at 40 kV and 40 mA with a scanning speed of 5°/min. The patterns were taken over the 2θ range from 5° to 50°. Nitrogen adsorption−desorption isotherms were measured using a Quantachrome QuadraSorb evo system at 77 K. The specific surface area of the samples was calculated by the Brunauer−Emmett−Teller (BET) method. The volume of pores was determined by the Barrett−Joyner−Halenda (BJH) method from the desorption branches of the isotherms. X-ray photoelectron spectroscopy (XPS) measurements were carried out with an ESCALAB250 spectrometer using a monochromated Al Kα X-ray source (1486.6 eV). The binding energy was calibrated using the adventitious C 1s peak at 284.6 eV. The morphology of catalysts was imaged using a Hitachi S4800 scanning electron microscope (Hitachi, Japan). The samples for FE-SEM measurements were prepared by depositing the powder on a conductive tape using N2 vertical purging. The voltage employed for lower amplification was 3 kV, while that for higher amplification was 1 kV. The catalyst samples were coated by sputtering with platinum prior to imaging. In situ DRIFTS spectra were recorded on a Thermo Fisher is50 FT-IR, equipped with an in situ diffuse reflection chamber

For SiO2 /Al 2O3 ratio = 25, 0.104 g of NaAlO2 For SiO2 /Al 2O3 ratio = 80, 0.033 g of NaAlO2 For SiO2 /Al 2O3 ratio = 200, 0.013 g of NaAlO2

2.2. Adsorption Measurements. The vapor-phase adsorption of DCM was performed using a 3H-2000PW Gravimetry Vapor Sorption Analyzer.35,36 In the 3H-2000PW, an ultrasensitive microbalance of resolution 0.1 μg is mounted in a thermostatic heat sink with high-precision temperature control. Each sample (100−110 mg/run) was degassed at 200 °C for 8 h. The measurements were carried out at 30 °C for vapor adsorption isotherm curves. It is convenient to represent experimental equilibrium isotherms by analytical expressions. Many models have been proposed to describe the isotherms, such as the Langmuir, Sips, and Toth models. In this study, the Langmuir and Toth equations were used to correlate the experimental data due to their adjustable parameters and good simulation behavior.37 The Langmuir model can be presented as follows: q=

qmbp (1 + bp)

(1)

The Toth equation can be presented as follows:

q=

qmbp (1 + (bp)t )1/ t

(3)

(2) B

DOI: 10.1021/acs.jced.8b00174 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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performance in industrial technologies such as gas adsorption, separation, ion exchange, and catalysis.40 MFI zeolites also show a three-dimensional pore system with a window size of about 4.7 × 4.46 × 4.46 Å.32 The kinetic diameter for DCM is 3.3 Å,8,23,24 thus the molecular sieve effect can be excluded. In other words, the DCM molecule can readily gain entrance to the micropores of both types of zeolite. The surface areas of FAU zeolites are two times larger than those of MFI, thus we tentatively presume that FAU can provide more capacity to capture pollutants. The chemical states and contents of skeleton Al and Si were characterized by XPS and EDS, respectively, with the results shown in Figure 2 and Table 1. The actual SiO2/Al2O3 ratios were close to the nominal values. The Al 2p binding energy peaks for NaX appeared at 73.3 eV. The peaks move toward higher values when the Si content increases, which indicates that skeleton Al3+ is in an electron-deficient state. On the other hand, the Si 2p binding energy peaks for ZSM-5 (200) with the highest Si content appeared at 102.96 eV. Correspondingly, the peaks for Si 2p move toward lower values when the Al content increases. This suggests that skeleton Si4+ is in an electron-rich state. There is a significant electron redistribution between skeleton elements when the Si/Al ratio changes. As the Al concentration increases, the electrostatic field of a zeolite increases accordingly.41,42 Thus, the Si/Al ratio is very critical in that it decides the properties of the electronic field or the homogeneity of absorbing sites, which finally influence the adsorption process. The SEM images of the samples are shown in Figure 3. The two different kinds of zeolites exhibit totally different morphologies, but samples of the same type of zeolite with different SiO2/Al2O3 ratios show very similar morphologies. For instance, FAU zeolites exhibit regular octahedral crystal morphologies with crystal sizes of ca.1.5−3.0 μm. MFI zeolites demonstrate very uniform and regular hexagonal morphologies with crystal sizes of ca. 2 μm. 3.2. Adsorption and Desorption Measurements. Equilibrium isotherm data for DCM on FAU and MFI zeolite were obtained at 30 °C. The experimental data and fitting curve are presented in Figure 4 and Table 2, respectively. It can be observed that all isotherms have a typical type I isotherm shape according to the IUPAC classification. The Toth equation is better than the Langmuir model at describing all isotherms due to having additional adjustable parameters. The general adsorption amount for five zeolites varies as follows: NaY > NaX > ZSM-5 (200) > ZSM-5 (85) ≈ ZSM-5 (25). This reveals that FAU zeolites have better adsorption capacity for DCM than that of MFI zeolites, which is consistent with the surface areas derived from N2 adsorption. However, the same type of zeolite with higher Si/Al ratio exhibited higher capacity. DCM adsorption does not depend on the electrostatic field since the framework Si/Al ratio is low; i.e., the electrostatic field is high, which is in accordance with adsorption of tetrachloroethylene43 and benzene44 on FAU zeolites. We can tentatively hypothesize that homogeneous adsorption sites derived from the high content of Si are beneficial for the adsorption of DCM. Nevertheless, the effect of Si content diminishes beyond a certain range. Take silicalite-1 (all-silicon ZSM-5), for example, where the adsorption amount was close to the value of ZSM-5 (200) as shown in Figure 4, which meant that the adsorption no longer increased with increasing Si content. A breakthrough measurement is a direct method designed to determine the dynamic performance of VOC removal by adsorption. The breakthrough curves were fitted by the Y−N equation, and the correlation parameters are presented in Table

(Harrick) and a high sensitivity MCT/A detector. All adsorbents were finely ground and placed in ceramic crucibles in the in situ chamber. Prior to recording each DRIFTS spectrum, the sample was heated in situ in N2 flow at 200 °C for 1 h, then cooled to the desired temperature to measure a reference spectrum. All spectra were measured with a resolution of 4 cm−1 with accumulation of 32 scans.

3. RESULTS AND DISCUSSION 3.1. Structural Properties. XRD patterns of all zeolite adsorbents are exhibited in Figure 1. NaX (PDF: 01-089-0770)

Figure 1. XRD patterns of FAU and MFI zeolites.

and NaY (PDF: 00-026-0896) zeolites exhibited well-resolved characteristic peaks associated with FAU zeolite,29 showing the main diffraction peaks at 6.2, 10.1, 11.7, 15.6, 18.7, 23.6, 26.9, and 31.4 degrees, etc. ZSM-5 with different Si/Al ratios demonstrated the diffraction pattern of MFI zeolite (PDF: 01-0851208),33,34 exhibiting the main diffraction peaks at 7.9, 8.8, 9.1, 11.9, 13.9,15.5, 15.9, 23.0, 23.2, 23.7, 23.9, and 24.4 degrees, etc. It is worth noting that the diffraction intensity of the main peak of FAU zeolite at 6.2 degrees decreased with the increase of the SiO2/Al2O3 ratio. In contrast, the opposite trend was observed for the peaks of MFI zeolite at diffraction angles of 7.9 and 8.8 degrees. This indicates that increasing the SiO2/Al2O3 ratio decreases the crystallinity of FAU zeolites but increases the crystallinity of MFI zeolites. The N2 sorption isotherms of zeolite FAU and MFI samples showed typical Langmuir-type curves (Figure S1), indicating the presence of very uniform micropores. The detailed textual parameters are listed in Table 1. It has been reported that FAU zeolites have a three-dimensional pore system with a window size of 7.35 × 7.35 × 7.35 Å, which gives them the potential for good Table 1. Textural Parameters of FAU and MFI Zeolites Derived from N2 Physisorption Results and XPS Results BET

pore volume

sample

2

XPS

(m /g)

(mL/g)

SiO2/Al2O3

Al 2p

Si 2p

NaX NaY ZSM-5 (25) ZSM-5 (80) ZSM-5 (200)

651.45 656.82 339.12 302.67 356.08

0.32 0.33 0.19 0.21 0.20

2.5 5.5 33.5 85.3 204.5

73.25 73.68 74.27 74.30 74.02

101.29 102.15 102.81 103.01 102.96 C

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Figure 2. XPS spectra of Al 2p (A) and Si 2p (B) for FAU and MFI zeolites.

Figure 4. Adsorption isotherms for DCM on FAU and MFI zeolites.

In order to investigate the desorption of DCM on the different kinds of zeolites, temperature-programmed desorption measurements were also conducted subsequently. The desorption results for DCM are exhibited in Figure 5(B). The amount of DCM desorbed is in accordance with the order of the dynamic adsorption capacities of DCM as shown in Figure 5(A). All desorption reached a peak at around the temperature of 100 °C. The adsorption affinity was in accordance with the dynamic adsorption capacity, exhibiting a higher desorption temperature. On the basis of equilibrium and dynamic results, we can conclude that ZSM-5 (200) is the best adsorbent in this study. The effect of space velocity and humidity on the selected ZSM5 (200) zeolite was also examined, as shown in Figure 6. The space velocity affects the removal efficiency of DCM significantly, and thus selection of suitable adsorption bed parameters appears to be crucial. The regular presence of water vapor in flue gas is one of the most important parameters strongly influencing the effectiveness of the adsorption process.43,45 It can be clearly observed from Figure 6(B) that the presence of water vapor caused only a slight acceleration in the breakthrough of DCM on the ZSM-5 (200) adsorbent when the relative humidity was increased from background 10% to 30%, and no profound difference in the breakthrough curves was found when humidity was increased to 90%. The presence of high humidity in the gas mixture does not lead to significant reduction in the adsorption capacity of DCM on ZSM-5 (200).

Figure 3. SEM images of FAU and MFI zeolites (A) NaX, (B) NaY, (C) ZSM-5 (25), (D) ZSM-5 (80), and (E) ZSM-5 (200).

2. In general, longer breakthrough times are associated with higher dynamic adsorption capacities. As shown in Figure 5(A), the order of dynamic adsorption capacities for five zeolites is ZSM-5 (200) > ZSM-5 (80) > ZSM-5 (25) ≈ NaY > NaX. This is in contradiction with the former equilibrium results. It is widely accepted that water vapor could compete with VOC molecules for limited adsorption sites on an adsorbent, leading to a great decrease in the breakthrough time, and is consequently detrimental to the VOC removal performance.38,39 In breakthrough measurement tests, water vapor with relative humidity of 10% was detected in the background atmosphere. Obvious water desorption can also be observed during ramping of the temperature (Figure S2). The presence of water vapor significantly depressed the DCM adsorption. That is the reason why the hydrophilic FAU zeolites had higher equilibrium capacity but performed worse in dynamic experiments. D

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Table 2. Langmuir and Toth Equation Correlation Parameters and Yoon−Nelson Model Fitting Results for FAU and MFI Zeolite Langmuir model

Toth model

Yoon and Nelson model

adsorbent

qm (mmol/g)

b

R2

qm (mmol/g)

b

t

R2

k (min−1)

τ0 (min)

R2

NaX NaY ZSM-5 (25) ZSM-5 (80) ZSM-5 (200)

2.24 2.55 1.69 1.76 2.11

1.079 0.549 0.674 0.360 0.518

0.994 0.990 0.989 0.971 0.979

3.02 4.67 2.79 5.99 4.33

1498 1500 1499 1996 1500

0.235 0.188 0.200 0.143 0.178

0.996 0.995 0.993 0.987 0.992

0.745 0.195 0.207 0.23 0.175

8.74 18.92 18.74 25.39 32.76

0.998 0.982 0.998 0.997 0.996

Figure 5. Breakthrough curves (A) and temperature-programmed desorption curves (B) for FAU and MFI zeolites.

Figure 6. Breakthrough curves for ZSM-5 (200) under different conditions: (A) space velocity effect, (B) humidity effect, and (C) stability test.

Moreover, a stability test was conducted as shown in Figure 6(C). The procedure consisted of adsorbing DCM to saturation on ZSM-5 (200) in feed gas with humidity of 50% and then desorbing it at a temperature of 100 °C overnight. The above process was repeated four times. The adsorbent was found to be stable, without substantial reduction in capacity after several

rigorous tests. On the basis of the above test, we can conclude that ZSM-5 (200) should be a promising candidate for lowconcentration DCM removal by adsorption. 3.3. Adsorption Mechanism. In situ DRIFTS is drawing more and more interest nowadays because the molecular structure changes after adsorption can be revealed by spectral E

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Figure 7. In situ DRIFTS spectra of DCM on FAU (A) and MFI zeolites (B) compared with the spectrum of gaseous DCM at temperature of 30 °C.

Figure 8. In situ DRIFTS spectra of DCM on NaX (A) and ZSM-5 (200) (B) at temperature of 30 °C and RH = 50%.

bond in DCM is relatively independent and barely influenced by the surface of the adsorbents. Compared with the peak of gaseous DCM around 3100 cm−1, the peaks for adsorbed DCM in both cases are red-shifted to the value of 3066 cm−1, suggesting that the C−H bond of DCM is weakened or elongated after the molecule is adsorbed on the surface of the solid. In addition, DCM adsorbed on FAU zeolites resulted in the disappearance of the peak around 1267 cm−1, instead showing a peak from 1199 to 1055 cm−1. This indicates that the rocking vibrations of the two H atoms of DCM are constrained by the pore space. Thus, we can suppose that DCM should be in intimate contact with the surface of FAU zeolites via an H atom. By contrast, a different adsorption structure is found for the MFI zeolites since the peak around 1267 cm−1 remains, together with other characteristic peaks of DCM. Thus we can conclude that DCM is relatively free in the middle of the pores in MFI zeolites without strong interaction with the pore walls. That can be ascribed to the relative homogeneity derived from the highest Si/Al ratio, which is consistent with the former XPS results. DCM molecules adsorbed on idealized FAU (formula: Al24Si24O96) and MFI (Si96O192) zeolite models were also compared by DFT calculations. The optimized adsorption

analysis. With this in mind, in situ DRIFTS experiments were performed to take a closer look at the molecular mechanism of adsorption. The spectra for gaseous DCM and its adsorption on the five zeolites are displayed in Figure 7, and the effect of temperature on adsorption is presented in Figure S3. Gaseous DCM shows six peaks (3100, 1276, 1267, 1260, 757, 742 cm−1) within the range of 3200−600 cm−1. According to another report46 and DFT simulation as shown in Figure S4, the peaks at 757 and 742 cm−1 can be, respectively, assigned to the asymmetric and symmetric stretching vibrations of the C−Cl bond. The peaks around 1260−1280 cm−1 were due to the symmetric and asymmetric rocking vibrations of the two H atoms. The small peaks around 3200−3100 cm−1 were ascribed to the symmetric and asymmetric stretching vibrations of C−H bonds. Exposure of the five zeolites, respectively, to gaseous DCM at the steady state resulted in significant changes in the infrared spectra. Two types of adsorption state could be classified according to the type of zeolite, as shown in Figure 7(A) and (B), respectively. The peak around 745 cm−1 is neither red-shifted nor blue-shifted substantially for the adsorbed state on the five zeolites, indicating that the stretching vibration of the C−Cl F

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Notes

structures are presented in Figure S5. Just as stated above, DCM is indeed in intimate contact with the pore windows of FAU via its H atoms. In the case of MFI, the molecule of DCM is closely surrounded by the pore wall. The adsorption energies for DCM on FAU and MFI are −0.29 and −0.25 eV, respectively. FAU zeolite has stronger interaction with DCM compared to MFI zeolite, which is consistent with the equilibrium isotherms. However, the adsorption energies for H2O on FAU and MFI are −0.76 and −0.17 eV, respectively (Figure S6). The selectivities of DCM with respect to H2O onto FAU and MFI zeolites are 0.33 and 1.71, respectively. In addition, in situ DRIFTS for the competitive adsorption between gaseous DCM and water vapor on NaX and ZSM-5 (200) zeolites are displayed in Figure 8(A) and (B), respectively, which demonstrate that the adsorption feature of DCM in the range of 700−1400 cm−1 is dominant on ZSM-5 (200) rather than NaX. This is consistent with DFT simulation results showing that MFI zeolites have better adsorption selectivity of DCM over water than FAU zeolites. Owing to the higher Si/Al ratio and homogeneity of adsorption sites, MFI zeolites exhibit better DCM selectivity over water vapor than FAU zeolites, which makes them promising candidates for DCM pollution control.

The authors declare no competing financial interest.

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(1) Wei, W.; Wang, S. X.; Hao, J. M.; Cheng, S. Y. Trends of Chemical Speciation Profiles of Anthropogenic Volatile Organic Compounds Emissions in China, 2005−2020. Front. Environ. Sci. Eng. 2014, 8, 27− 41. (2) Yao, M. J.; Ji, Y. M.; Wang, H. H.; Ao, Z. M.; Li, G. Y.; An, T. C. Adsorption Mechanisms of Typical Carbonyl-Containing Volatile Organic Compounds on Anatase Tio2 (001) Surface: A Dft Investigation. J. Phys. Chem. C 2017, 121, 13717−13722. (3) Roso, M.; Boaretti, C.; Pelizzo, M. G.; Lauria, A.; Modesti, M.; Lorenzetti, A. Nanostructured Photocatalysts Based on Different Oxidized Graphenes for Vocs Removal. Ind. Eng. Chem. Res. 2017, 56, 9980−9992. (4) Kamal, M. S.; Razzak, S. A.; Hossain, M. M. Catalytic Oxidation of Volatile Organic Compounds (VOCs) - a Review. Atmos. Environ. 2016, 140, 117−134. (5) Delaunay, F.; Rodriguez-Castillo, A. S.; Couvert, A.; Amrane, A.; Biard, P. F.; Szymczyk, A.; Mafreyt, P.; Ghoufi, A. Interfacial Structure of Toluene at an Ionic Liquid/Vapor Interface: A Molecular Dynamics Simulation Investigation. J. Phys. Chem. C 2015, 119, 9966−9972. (6) Herdes, C.; Valente, A.; Lin, Z.; Rocha, J.; Coutinho, J. A. P.; Medina, F.; Vega, L. F. Selective Adsorption of Volatile Organic Compounds in Micropore Aluminum Methylphosphonate-Alpha: A Combined Molecular Simulation-Experimental Approach. Langmuir 2007, 23, 7299−7305. (7) Wei, W.; Wang, S. X.; Hao, J. M.; Cheng, S. Y. Projection of Anthropogenic Volatile Organic Compounds (Vocs) Emissions in China for the Period 2010−2020. Atmos. Environ. 2011, 45, 6863−6871. (8) Jovic, S.; Laxrninarayan, Y.; Keurentjes, J.; Schouten, J.; van der Schaaf, J. Adsorptive Water Removal from Dichloromethane and VaporPhase Regeneration of a Molecular Sieve 3a Packed Bed. Ind. Eng. Chem. Res. 2017, 56, 5042−5054. (9) Shestakova, M.; Sillanpaa, M. Removal of Dichloromethane from Ground and Wastewater: A Review. Chemosphere 2013, 93, 1258−1267. (10) Lemus, J.; Martin-Martinez, M.; Palomar, J.; Gomez-Sainero, L.; Gilarranz, M. A.; Rodriguez, J. J. Removal of Chlorinated Organic Volatile Compounds by Gas Phase Adsorption with Activated Carbon. Chem. Eng. J. 2012, 211, 246−254. (11) Agueda, V. I.; Crittenden, B. D.; Delgado, J. A.; Tennison, S. R. Effect of Channel Geometry, Degree of Activation, Relative Humidity and Temperature on the Performance of Binderless Activated Carbon Monoliths in the Removal of Dichloromethane from Air. Sep. Purif. Technol. 2011, 78, 154−163. (12) Ragunath, S.; Mitra, S. Carbon Nanotube Immobilized Composite Hollow Fiber Membranes for Extraction of Volatile Organics from Air. J. Phys. Chem. C 2015, 119, 13231−13237. (13) Zhou, L.; Zhang, X. H.; Chen, Y. L. Facile Synthesis of AlFumarate Metal-Organic Framework Nano-Flakes and Their Highly Selective Adsorption of Volatile Organic Compounds. Mater. Lett. 2017, 197, 224−227. (14) Mukaratirwa-Muchanyereyi, N.; Kugara, J.; Zaranyika, M. F. Adsorption of Volatile Polar Organic Solvents on Water Hyacinth (Eichhornia Crassipes) Root Biomass: Thermodynamic Parameters and Mechanism. Int. J. Environ. Sci. Technol. 2016, 13, 1941−1950. (15) Hsu, S. H.; Huang, C. S.; Chung, T. W.; Gao, S. Adsorption of Chlorinated Volatile Organic Compounds Using Activated Carbon Made from Jatropha Curcas Seeds. J. Taiwan Inst. Chem. Eng. 2014, 45, 2526−2530. (16) Pan, H. Y.; Tian, M.; Zhang, H.; Zhang, Y.; Lin, Q. Adsorption and Desorption Performance of Dichloromethane over Activated Carbons Modified by Metal Ions. J. Chem. Eng. Data 2013, 58, 2449−2454. (17) Le Cloirec, P. Adsorption onto Activated Carbon Fiber Cloth and Electrothermal Desorption of Volatile Organic Compound (Vocs): A Specific Review. Chin. J. Chem. Eng. 2012, 20, 461−468.

4. CONCLUSIONS Adsorptive removal of dichloromethane from the vapor phase was conducted on FAU and MFI zeolites with different Si/Al ratios. FAU zeolites exhibited better equilibrium capacity than MFI zeolites, while MFI zeolite had better dynamic capacity than FAU zeolite. ZSM-5 (200), with the highest Si/Al ratio, exhibited the best adsorption working capacity and was barely affected by water vapor. No significant decrease in uptake was observed after adsorption and thermal regeneration around 100 °C over several cycles. The experimental and theoretical results were consistent and showed that MFI zeolites have better selectivity of DCM over water due to the homogeneity of adsorption sites derived from a low content of Al. In situ DRIFTS and DFT simulations suggest that adsorbed DCM is intimately in contact with the pore window of FAU zeolite via its H atoms. In contrast, dichloromethane is captured in the center of MFI’s pores. The insights gained are important to enable more rational selection of adsorbents and design of adsorption processes.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jced.8b00174. N2 sorption isotherms, temperature-programmed desorption of water, in situ DRIFTS, and DFT calculation are available (PDF)

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REFERENCES

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Fax/Tel.: +86-592-6190563. ORCID

Hua Deng: 0000-0002-5258-906X Funding

The work was supported by the National Natural Science Foundation of China (51608504), the Youth Innovation Promotion Association, and Chinese Academy of Sciences (2017064). G

DOI: 10.1021/acs.jced.8b00174 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

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(18) Giraudet, S.; Pre, P.; Le Cloirec, P. Modeling the Temperature Dependence of Adsorption Equilibriums of Voc(S) onto Activated Carbons. J. Environ. Eng. 2010, 136, 103−111. (19) Abdelbassit, M. S. A.; Alhooshani, K. R.; Saleh, T. A. Silica Nanoparticles Loaded on Activated Carbon for Simultaneous Removal of Dichloromethane, Trichloromethane, and Carbon Tetrachloride. Adv. Powder Technol. 2016, 27, 1719−1729. (20) Saleh, T. A.; Alhooshani, K. R.; Abdelbassit, M. S. A. Evaluation of Ac/Zno Composite for Sorption of Dichloromethane, Trichloromethane and Carbon Tetrachloride: Kinetics and Isotherms. J. Taiwan Inst. Chem. Eng. 2015, 55, 159−169. (21) Khan, M. A.; Kim, S. W.; Rao, R. A. K.; Abou-Shanab, R. A. I.; Bhatnagar, A.; Song, H.; Jeon, B. H. Adsorption Studies of Dichloromethane on Some Commercially Available Gacs: Effect of Kinetics, Thermodynamics and Competitive Ions. J. Hazard. Mater. 2010, 178, 963−972. (22) Borkar, C.; Tomar, D.; Gumma, S. Adsorption of Dichloromethane on Activated Carbon. J. Chem. Eng. Data 2010, 55, 1640−1644. (23) Tian, F. M.; Zhang, X. H.; Chen, Y. L. Amino-Functionalized Metal-Organic Framework for Adsorption and Separation of Dichloromethane and Trichloromethane. RSC Adv. 2016, 6, 63895−63904. (24) Tian, F. M.; Zhang, X. H.; Chen, Y. L. Highly Selective Adsorption and Separation of Dichloromethane/Trichloromethane on a CopperBased Metal-Organic Framework. RSC Adv. 2016, 6, 31214−31224. (25) Huang, C. Y.; Song, M.; Gu, Z. Y.; Wang, H. F.; Yan, X. P. Probing the Adsorption Characteristic of Metal-Organic Framework Mil-101 for Volatile Organic Compounds by Quartz Crystal Microbalance. Environ. Sci. Technol. 2011, 45, 4490−4496. (26) Jia, L. J.; Ma, J. K.; Shi, Q. Y.; Long, C. Prediction of Adsorption Equilibrium of Vocs onto Hyper-Cross-Linked Polymeric Resin at Environmentally Relevant Temperatures and Concentrations Using Inverse Gas Chromatography. Environ. Sci. Technol. 2017, 51, 522−530. (27) Wang, S. S.; Zhang, L.; Long, C.; Li, A. M. Enhanced Adsorption and Desorption of Vocs Vapor on Novel Micro-Mesoporous Polymeric Adsorbents. J. Colloid Interface Sci. 2014, 428, 185−190. (28) Lee, J. W.; Lee, J. W.; Shim, W. G.; Suh, S. H.; Moon, H. Adsorption of Chlorinated Volatile Organic Compounds on Mcm-48. J. Chem. Eng. Data 2003, 48, 381−387. (29) Clausse, B. t.; Garrot, B.; Cornier, C.; Paulin, C.; Simonot-Grange, M.-H.; Boutros, F. Adsorption of Chlorinated Volatile Organic Compounds on Hydrophobic Faujasite: Correlation between the Thermodynamic and Kinetic Properties and the Prediction of Air Cleaning. Microporous Mesoporous Mater. 1998, 25, 169−177. (30) Koh, C. A.; Westacott, R. E.; Nooney, R. I.; Boissel, V.; Tahir, S. F.; Tricarico, V. Separation of Dichloromethane-Nitrogen Mixtures by Adsorption: Experimental and Molecular Simulation Studies. Mol. Phys. 2002, 100, 2087−2095. (31) Kawai, T.; Yanagihara, T.; Tsutsumi, K. Adsorption Characteristics of Chloroform on Modified Zeolites from Gaseous-Phase as Well as Its Aqueous-Solution. Colloid Polym. Sci. 1994, 272, 1620−1626. (32) Zhang, C. S.; Wu, Q. M.; Lei, C.; Pan, S. X.; Bian, C. Q.; Wang, L.; Meng, X. J.; Xiao, F. S. Solvent-Free and Mesoporogen-Free Synthesis of Mesoporous Aluminosilicate Zsm-5 Zeolites with Superior Catalytic Properties in the Methanol-to-Olefins Reaction. Ind. Eng. Chem. Res. 2017, 56, 1450−1460. (33) Wang, L.; Zhang, J.; Yi, X. F.; Zheng, A. M.; Deng, F.; Chen, C. Y.; Ji, Y. Y.; Liu, F. J.; Meng, X. J.; Xiao, F. S. Mesoporous Zsm-5 ZeoliteSupported Ru Nanoparticles as Highly Efficient Catalysts for Upgrading Phenolic Biomolecules. ACS Catal. 2015, 5, 2727−2734. (34) Chen, C. Y.; Chen, F.; Zhang, L.; Pan, S. X.; Bian, C. Q.; Zheng, X. M.; Meng, X. J.; Xiao, F. S. Importance of Platinum Particle Size for Complete Oxidation of Toluene over Pt/Zsm-5 Catalysts. Chem. Commun. 2015, 51, 5936−5938. (35) Hu, P.; Liang, X. P.; Yaseen, M.; Sun, X. D.; Tong, Z. F.; Zhao, Z. X.; Zhao, Z. X. Preparation of Highly-Hydrophobic Novel NCoordinated Uio-66(Zr) with Dopamine Via Fast Mechano-Chemical Method for (Cho-/Cl-)-Vocs Competitive Adsorption in Humid Environment. Chem. Eng. J. 2018, 332, 608−618.

(36) Li, J. Q.; Lu, S. F.; Xie, L. J.; Zhang, J.; Xue, H. T.; Zhang, P. F.; Tian, S. S. Modeling of Hydrocarbon Adsorption on Continental Oil Shale: A Case Study on N-Alkane. Fuel 2017, 206, 603−613. (37) Deng, H.; Yi, H. H.; Tang, X. L.; Yu, Q. F.; Ning, P.; Yang, L. P. Adsorption Equilibrium for Sulfur Dioxide, Nitric Oxide, Carbon Dioxide, Nitrogen on 13x and 5a Zeolites. Chem. Eng. J. 2012, 188, 77− 85. (38) Wang, J. H.; Wang, W. Q.; Hao, Z. P.; Wang, G.; Li, Y.; Chen, J. G.; Li, M. M.; Cheng, J.; Liu, Z. T. A Superhydrophobic Hyper-CrossLinked Polymer Synthesized at Room Temperature Used as an Efficient Adsorbent for Volatile Organic Compounds. RSC Adv. 2016, 6, 97048− 97054. (39) Wang, J. H.; Wang, G.; Wang, W. Q.; Zhang, Z. S.; Liu, Z. T.; Hao, Z. P. Hydrophobic Conjugated Microporous Polymer as a Novel Adsorbent for Removal of Volatile Organic Compounds. J. Mater. Chem. A 2014, 2, 14028−14037. (40) Zhu, L. F.; Ren, L. M.; Zeng, S. J.; Yang, C. G.; Zhang, H. Y.; Meng, X. J.; Rigutto, M.; van der Made, A.; Xiao, F. S. High Temperature Synthesis of High Silica Zeolite Y with Good Crystallinity in the Presence of N-Methylpyridinium Iodide. Chem. Commun. 2013, 49, 10495−10497. (41) Jhung, S. H.; Yoon, J. W.; Lee, S.; Chang, J. S. Low-Temperature Adsorption/Storage of Hydrogen on Fau, Mfi, and Mor Zeolites with Various Si/Al Ratios: Effect of Electrostatic Fields and Pore Structures. Chem. - Eur. J. 2007, 13, 6502−6507. (42) Preuss, E.; Linden, G.; Peuckert, M. Model-Calculations of Electrostatic Fields and Potentials in Faujasite Type Zeolites. J. Phys. Chem. 1985, 89, 2955−2961. (43) Guillemot, M.; Mijoin, J.; Mignard, S.; Magnoux, P. Adsorption of Tetrachloroethylene (Pce) in Gas Phase on Zeolites of Faujasite Type: Influence of Water Vapour and of Si/Al Ratio. Microporous Mesoporous Mater. 2008, 111, 334−342. (44) Daems, I.; Methivier, A.; Leflaive, P.; Fuchs, A. H.; Baron, G. V.; Denayer, J. F. M. Unexpected Si: Al Effect on the Binary Mixtures Liquid Phase Adsorption Selectivities in Faujasite Zeolites. J. Am. Chem. Soc. 2005, 127, 11600−11601. (45) Liu, S.; Chen, J. J.; Peng, Y.; Hu, F. Y.; Li, K. Z.; Song, H.; Li, X.; Zhang, Y. N.; Li, J. H. Studies on Toluene Adsorption Performance and Hydrophobic Property in Phenyl Functionalized Kit-6. Chem. Eng. J. 2018, 334, 191−197. (46) Maupin, I.; Pinard, L.; Mijoin, J.; Magnoux, P. Bifunctional Mechanism of Dichloromethane Oxidation over Pt/Al2O3: CH2Cl2 Disproportionation over Alumina and Oxidation over Platinum. J. Catal. 2012, 291, 104−109.

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DOI: 10.1021/acs.jced.8b00174 J. Chem. Eng. Data XXXX, XXX, XXX−XXX