Journal of Natural Gas Chemistry Vol. 21 No. 4 2012

CONTENTS

367 Hydrogen production by catalytic decomposition ofmethane using a Fe-based catalyst in a fluidized bedreactor

D. Torres, S. de Llobet, J. L. Pinilla, M. J. Lazaro,I. Suelves, R. Moliner

374 Experimental studies of biomass gasification with air

Huili Liu, Jianhang Hu, Hua Wang, Chao Wang, Juan-qin Li

381 Numerical studies of hydrate dissociation and gas pro-duction behavior in porous media during depressur-ization process

Xuke Ruan, Mingjun Yang, Yongchen Song,Haifeng Liang, Yanghui Li

393 Pd catalysts supported on modified Zr0.5Al0.5O1.75

used for lean-burn natural gas vehicles exhaust pu-rification

Hongyan Shang, Yun Wang, Maochu Gong, Yao-qiang Chen

400 Particle/metal-based monolithic catalysts dual-bed re-actor with beds-interspace supplementary oxygen:Construction and performance for oxidative couplingof methane

Wenhua Wang, Zhao Zhang, Shengfu Ji

407 Dynamic modeling of a H2O-permselective mem-brane reactor to enhance methanol synthesis fromsyngas considering catalyst deactivation

M. Farsi, A. Jahanmiri

415 Optimization of preparation conditions of Fe-Conanoparticles in low-temperature CO oxidation reac-tion by taguchi design method

Abolfazl Biabani, Mehran Rezaei, Zohreh Fattah

421 Effects of toluene on thiophene adsorption over NaYand Ce(IV)Y zeolites

Yanchun Shi, Xiaojian Yang, Fuping Tian, Cuiying Jia,Yongying Chen

426 Effect of preparation method on halloysite supportedcobalt catalysts for Fischer-Tropsch synthesis

Sufang Chen, Jinlin Li, Yuhua Zhang, Daohong Zhang,Junjiang Zhu

431 An effective route to improve the catalytic perfor-mance of SAPO-34 in the methanol-to-olefin reaction

Guangyu Liu, Peng Tian, Qinhua Xia, Zhongmin Liu

435 Conversion enhancement of tubular fixed-bed reactorfor Fischer-Tropsch synthesis using static mixer

Phavanee Narataruksa, Sabaithip Tungkamani,Karn Pana-Suppamassadu, Phongsak Keeratiwin-takorn, Siriluck Nivitchanyong, Piyapong Hunpinyo,Hussanai Sukkathanyawat, Prayut Jiamrittiwong,Visarut Nopparat

445 CO selective methanation in hydrogen-rich gas mix-tures over carbon nanotube supported Ru-based cat-alysts

Jun Xiong, Xinfa Dong, Lingling Li

452 Styrene epoxidation with hydrogen peroxide over cal-cium oxide catalysts prepared from various precur-sors

Qingming Gu, Dan Han, Lei Shi, Qi Sun

459 Modeling phase equilibria of semiclathrate hydratesof CH4, CO2 and N2 in aqueous solution of tetra-n-butyl ammonium bromide

Abhishek Joshi, Prathyusha Mekala, Jitendra S. Sangwai

466 Comparison of dry reforming of methane in low tem-perature hybrid plasma-catalytic corona with thermalcatalytic reactor over Ni/γγγ-Al2O3

Amin Aziznia, Hamid Reza Bozorgzadeh, Naser Seyed-Matin, Morteza Baghalha, Ali Mohamadalizadeh

476 Ionic liquid mediated CO2 activation for DMC syn-thesis

Jun Du, Jing Shi, Zhengfei Li, Zuohua Liu, Xing Fan,Changyuan Tao

2011 SCI Impact Factor being 1.348 forJournal of Natural GasChemistry (380)

www.jngc.orgwww.elsevier.com/locate/jngc

CONTENTS

Articles

367Hydrogen production by catalytic decomposition ofmethane using a Fe-based catalyst in a fluidized bedreactor

D. Torres, S. de Llobet, J. L. Pinilla, M. J. Lazaro,I. Suelves, R. Moliner

374Experimental studies of biomass gasification with air

Huili Liu, Jianhang Hu, Hua Wang, Chao Wang, Juan-qin Li

381Numerical studies of hydrate dissociation and gasproduction behavior in porous media during depres-surization process

Xuke Ruan, Mingjun Yang, Yongchen Song,Haifeng Liang, Yanghui Li

393Pd catalysts supported on modified Zr0.5Al0.5O1.75

used for lean-burn natural gas vehicles exhaust pu-rification

Hongyan Shang, Yun Wang, Maochu Gong, Yao-qiang Chen

400Particle/metal-based monolithic catalysts dual-bedreactor with beds-interspace supplementary oxygen:Construction and performance for oxidative couplingof methane

Wenhua Wang, Zhao Zhang, Shengfu Ji

407Dynamic modeling of a H2O-permselective mem-brane reactor to enhance methanol synthesis fromsyngas considering catalyst deactivation

M. Farsi, A. Jahanmiri

415Optimization of preparation conditions of Fe-Conanoparticles in low-temperature CO oxidation reac-tion by taguchi design method

Abolfazl Biabani, Mehran Rezaei, Zohreh Fattah

421Effects of toluene on thiophene adsorption over NaYand Ce(IV)Y zeolites

Yanchun Shi, Xiaojian Yang, Fuping Tian, Cuiying Jia,Yongying Chen

426Effect of preparation method on halloysite supportedcobalt catalysts for Fischer-Tropsch synthesis

Sufang Chen, Jinlin Li, Yuhua Zhang, Daohong Zhang,Junjiang Zhu

431An effective route to improve the catalytic perfor-mance of SAPO-34 in the methanol-to-olefin reaction

Guangyu Liu, Peng Tian, Qinhua Xia, Zhongmin Liu

435Conversion enhancement of tubular fixed-bed reactorfor Fischer-Tropsch synthesis using static mixer

Phavanee Narataruksa, Sabaithip Tungkamani,Karn Pana-Suppamassadu, Phongsak Keeratiwin-takorn, Siriluck Nivitchanyong, Piyapong Hunpinyo,Hussanai Sukkathanyawat, Prayut Jiamrittiwong,Visarut Nopparat

445CO selective methanation in hydrogen-rich gas mix-tures over carbon nanotube supported Ru-based cat-alysts

Jun Xiong, Xinfa Dong, Lingling Li

452Styrene epoxidation with hydrogen peroxide over cal-cium oxide catalysts prepared from various precur-sors

Qingming Gu, Dan Han, Lei Shi, Qi Sun

459Modeling phase equilibria of semiclathrate hydratesof CH4, CO2 and N2 in aqueous solution of tetra-n-butyl ammonium bromide

Abhishek Joshi, Prathyusha Mekala, Jitendra S. Sangwai

466Comparison of dry reforming of methane in low tem-perature hybrid plasma-catalytic corona with ther-mal catalytic reactor over Ni/γγγ-Al2O3

Amin Aziznia, Hamid Reza Bozorgzadeh, Naser Seyed-Matin, Morteza Baghalha, Ali Mohamadalizadeh

476Ionic liquid mediated CO2 activation for DMC syn-thesis

Jun Du, Jing Shi, Zhengfei Li, Zuohua Liu, Xing Fan,Changyuan Tao

Journal of Natural Gas Chemistry 21(2012)421–425

Effects of toluene on thiophene adsorptionover NaY and Ce(IV)Y zeolites

Yanchun Shi, Xiaojian Yang, Fuping Tian∗, Cuiying Jia, Yongying ChenSchool of Chemistry & State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024, Liaoning, China

[ Manuscript received November 7, 2011; revised January 4, 2012 ]

AbstractZeolites NaY and Ce(IV)Y were employed as adsorbents to remove organic sulfur compounds from model gasoline (MG) solutions with andwithout toluene in static adsorption experiments at room temperature (RT) and atmospheric pressure. The adsorbents were characterized byXRD, XRF and pyridine infrared spectrum (IR). The adsorption experiments show that the desulfurization performance ofCe(IV)Y is muchbetter than that of NaY. The sulfur removal over both NaY and Ce(IV)Y decreases with the increase of toluene concentration in MG, however,the decline tendency on Ce(IV)Y is smooth, and it is steep on NaY. FT-IR spectra of thiophene adsorption indicate that thiophene moleculesare mainly adsorbed on NaY viaπ electron interaction, but on Ce(IV)Y, in addition to theπ electron interaction, both Ce4+-S direct interactionand protonation of thiophene also play important roles. Toluene molecules are adsorbed on NaY also viaπ electron interaction. Although theamount of Bronsted acid sites is increased due to the introduction of Ce4+ ions into NaY zeolite, it is not found to influence the adsorptionmode of toluene over Ce(IV)Y. Compared with NaY zeolite, theimproved desulfurization performance over Ce(IV)Y for removing organicsulfur compounds from MG solution, especially those containing large amount of aromatics, may be ascribed to the directCe(IV)-S interaction,which is much resistant to the influence resulted from toluene adsorption.

Key wordstoluene; Ce(IV)Y; adsorption desulfurization; thiophene; Ce4+-S interaction

1. Introduction

Deep desulfurization of transportation fuels has becomevery urgent for the petroleum refining industry due to the in-creasing stringent environmental regulations and the potentialapplications of transportation fuels in fuel cells in the future[1,2]. The Environmental Protection Agency of the UnitedStates and the European Commission have recently issuedregulations that require the refineries to reduce the sulfur con-tent in gasoline less than 10 ppm by weight in 2011 [3,4].Therefore, desulfurization of transportation fuels has becomean important issue worldwide.

Conventional hydrodesulfurization (HDS) is effectivein removing sulfur-containing compounds in gasoline fuel.However, to decrease the sulfur content in gasoline distilla-tion at a deeper level, the HDS process may require substan-tial hydrogen consumption and lead to a significant loss inoctane number due to the transformation of olefin to alkane

[5]. Alternative methods such as oxidative desulfurization [6],extractive desulfurization [7], biodesulfurization [8] and ad-sorptive desulfurization [9−21] are being developed in recentyears to produce fuels with ultra low sulfur. Among these,adsorptive desulfurization is regarded as a promising methodfor the removal of thiophenic sulfur compounds to produceultra-clean fuels under moderate conditions.

So far, a variety of adsorbents such as metal oxides[10], active carbon [11], clays [12], mesoporous materials[13] and zeolites [14−21] have already been studied for deepdesulfurization. Zeolites, especially FAU zeolites, havebeenwidely investigated, owing to the high specific surface areaand large amount of exchangeable cation sites. For ex-ample, Cu(I)Y and AgY zeolites [17,18] were reported toeffectively remove the sulfur compounds in transportationfu-els by π-complexation interaction between the heterocyclicring of sulfur compound and the transition metal cation in thezeolite. However, Song and his co-workers [19,20] thought

∗ Corresponding author. Tel: +86-411-84708901; Fax: +86-411-84706313; E-mail: fptian@dlut.edu.cnThis work was financially supported by the Fundamental Research Funds for the Key Universities (Grant No. DUT10LK25) and the National Natural

Science Foundation of China (Grant No. 21106014).

Copyright©2012, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. All rights reserved.doi:10.1016/S1003-9953(11)60385-X

422 Yanchun Shi et al./ Journal of Natural Gas Chemistry Vol. 21 No. 4 2012

that although theπ-complexation interaction, to some ex-tent, was capable of removing sulfur compounds, it was in-evitable that the coexistence of large amounts of aromaticsand olefins in fuels would strongly decrease the adsorptionof sulfur compounds. They reported a higher selectivity forsulfur compounds than for aromatics over Ce-exchanged Yzeolite, which was ascribed to the direct S-M interaction be-tween the sulfur compounds and the metal cations in the ze-olite. Our previous work [21] also confirmed that the ceriumions exchanged into NaY led to an evident enhancement in thesulfur removal from FCC gasoline, which contains 19.3% aro-matic compounds and 30.4% olefins, and Ce (IV) content hada significant effect on the sulfur removal from FCC gasoline.However, no detailed research on the influence of the individ-ual aromatics or olefins on the adsorptive desulfurizationofgasoline fuels was carried out in our previous work [21].

The present work focused on the effect of toluene on thio-phene removal over NaY and Ce(IV)Y zeolites by adsorptionexperiments that were carried out in stirred batch reactor atroom temperature (RT). FT-IR spectroscopy was employed tostudy the adsorption behavior of thiophene and toluene on ad-sorbents. The aim of this paper is to provide spectroscopic in-formation about the adsorption modes of adsorbates by FT-IR,and to interpret the mechanism of competitive adsorption. It iswell known that competitive adsorption between organic sul-fur compounds and the co-existing aromatics in gasoline isone of the crucial factors that affect the adsorption selectivityfor sulfur removal from real fuels.

When investigating the effect of the adsorption mode ofsulfur compounds on desulfurization selectivity, we shouldalso consider the influence of adsorbent acid property on ad-sorptive desulfurization. However, it seems that the interac-tion mode between sulfur compounds and the metal ions in theion-exchanged zeolites has been overemphasized, whereas thechange in the acid property of zeolite has been ignored due tothe introduction of different metal ions onto it in the adsorp-tive desulfurization. In this paper, we will also investigate theeffect of the acid property of Ce(IV)Y zeolite on the selectiv-ity of thiophene adsorption.

2. Experimental

2.1. Adsorbents and model gasoline (MG) preparation

The starting material used in this study was NaY zeolite(SiO2/Al2O3 = 4.84). Ce(IV)Y was prepared by liquid-phaseion exchange method according to literature [21]. The colorofcerium ion-exchanged Y zeolite changed from white to lightyellow after calcination at 550◦C, suggesting the oxidation ofCe3+ to Ce4+. Thiophene, toluene and cyclohexane were cho-sen to be the model components for sulfur compound, aromat-ics and hydrocarbon in gasoline distillation, respectively. Sev-eral model gasoline fuels containing about 100 ngS/µL wereprepared, in which the molar ratio of toluene to thiophene is0 : 1, 1 : 1, 10 : 1, 100 : 1 and 500 : 1, respectively. The de-tailed composition of the model fuels was listed in Table 1.

Table 1. The compositions of model gasolines (MGs)

S content n(toluene)/ Content ofMGs (ng/µL)

Compositionsn(thiophene) toluene (vol%)

MG1 101.1 thiophene/cyclohexane 0 : 1 0MG2 102.4 thiophene+toluene/cyclohexane 1 : 1 0.033MG3 102.1 thiophene+toluene/cyclohexane 10 : 1 0.33MG4 104.9 thiophene+toluene/cyclohexane 100 : 1 3.3MG5 101.0 thiophene+toluene/cyclohexane 500 : 1 16.6

2.2. Adsorbent characterization

XRD patterns of NaY and Ce(IV)Y adsorbents were col-lected in the 2θ range of 5o–40o using a Rigaku. D/Max-RBdiffractometer with CuKα radiation (λ = 1.5418A) operatedat 40 kV and 200 mA. Elemental analysis for the adsorbentswas measured by SRS-3400(BRUKER) XRF. FT-IR, usingpyridine as probe molecule, was used to measure the acidproperty of NaY and Ce(IV)Y. IR spectra were obtained onNicolet Avatar 360 FT-IR spectrometer by scans of 64 with aresolution of 4 cm−1.

2.3. IR study on the interaction between adsorbent and adsor-bate

IR spectra of thiophene or toluene adsorbed on NaYand Ce(IV)Y zeolites were obtained on Nicolet Avatar 360FT-IR spectrometer by scans of 64 with a resolution of4 cm−1. The samples were pressed into a self-supportingwafer (10−15 mg) and placed in a quartz IR cell with CaF2

windows. Then it was purged with N2 flow at 350◦C for 1 hand subsequently cooled down to RT for thiophene or tolueneadsorption. After adsorbing for 10 s, the samples were purgedwith N2 flow. Then the IR spectra of thiophene or toluene ad-sorption on samples were recorded at RT. All the spectra givenin this work were difference spectra.

2.4. Adsorptive desulfurization

Prior to desulfurization experiment, the adsorbents weredried in oven at 120◦C overnight in order to remove the phys-ically adsorbed water. The adsorption experiment was car-ried out in a batch system at RT and atmospheric pressure.The dried adsorbents (0.25 g) were mixed rapidly with 5.0 mLMG in flasks. After 3 h, the desulfurized MG was separatedby filtration, and the sulfur content of MG before and afteradsorption was analyzed by microcoulometry. The sulfur re-moval (R%) was calculated according to the following for-mula:

R (%) =(c0− ce)

c0×100

where,c0 andce stand for the sulfur content in MG before andafter desulfurization, respectively.

MG4 before and after desulfurization was analyzed by aAgilent 7890A gas chromatograph with Agilent G6600A sul-fur chemiluminescence detector (GC-SCD) to detect whether

Journal of Natural Gas Chemistry Vol. 21 No. 4 2012 423

new organic sulfur compounds were formed during the desul-furization process. The oven temperature was initially setat70◦C for 1 min, and then heated at 5◦C/min up to 120◦C;once 120◦C was reached, the temperature was raised at10◦C/min up to 280◦C, and was held for 5 min.

3. Results and discussion

3.1. Adsorbent characterization

XRD patterns of NaY and Ce(IV)Y adsorbents (notshown in this paper) give the similar diffraction peaks of NaYand Ce(IV)Y, suggesting that the original zeolite structure wasretained after cerium ions exchange and calcination. Someminor differences in the XRD patterns are ascribed to the de-crease in the crystallinity of Ce(IV)Y due to NaY being ion-exchanged. XRF analysis shows that about 94% Na+ in Y ze-olite was exchanged with Ce3+ by repeating the ion-exchangeprocedure twice, about 10% higher than our previous resultsreported in Ref. [21].

FT-IR spectra of pyridine adsorbed on NaY and Ce(IV)Yare shown in Figure 1. Different from NaY, a kind ofnon-acidic zeolite, Ce(IV)Y possesses both Bronsted andLewis acid sites, characterized by the peaks centered at1541 cm−1and 1451 cm−1, respectively. It can also be seenthat the amount of Bronsted acid sites is much higher thanthat of Lewis acid sites. Meanwhile, most of the Bronstedacid sites are in medium or strong strength.

Figure 1. IR spectra of pyridine desorption from Ce(IV)Y at differenttem-peratures

3.2. FT-IR study on adsorption modes

3.2.1. Adsorption of thiophene over NaY and Ce(IV)Y

IR spectra of thiophene adsorbed on NaY and Ce(IV)Yat RT are shown in Figure 2. To get more information, weobserve peaks in the region of 3800−1350 cm−1 in this work.After thiophene was adsorbed on NaY, two evident peaks cen-tered at 3107 and 1396 cm−1 (shown in Figure 2(1)) could

be observed. As discussed in Refs. [16,21], the band at1396 cm−1 can be originated from thiophene molecule ad-sorbed on Na+ ion via π-electronic interaction. At the mean-time, the appearance of a peak with downword direction at3704 cm−1 after thiophene adsorption on NaY, suggesting thatsome thiophene molecules were adsorbed on the non-acidichydroxyl group of NaY as discussed in Ref. [22]. Com-pared with the bands observed on NaY, IR spectra of thio-phene adsorbed on Ce(IV)Y (Figure 2(2)) were more com-plex. Besides the bands observed on NaY, some new bandsat 3523, 2944, 2859, 1450 and 1438 cm−1 were also observedon Ce(IV)Y, implying that many different modes would beproduced when thiophene adsorption on Ce(IV)Y. The bandat 1438 cm−1, which was also observed in the case of thio-phene adsorbed on LaNaY [16], is designated to the shift ofν(C=C) sym from 1409 cm−1 in gaseous thiophene moleculeto higher frequencies, since the electron density within theC = C–C = C fragment increases when thiophene is adsorbedon Ce(IV)Y through S atom [16,23]. This designation in-dicates that there is a direct interaction between S atoms ofthiophene and Ce4+ ions of Ce(IV)Y zeolite. The two minorbands at 2944 and 2859 cm−1 are ascribed toαC−H of sat-urated CH2 groups close to either the double bond (*CH2–CH = CH-) or the sulfur atom (*CH2–S-) as suggested inRefs [24,25], which resulting from the formation of proto-nated thiophene on Bronsted acid sites of Ce(IV)Y. The bandat 3523 cm−1 with downward direction also suggests thatsome thiophene molecules were adsorbed on Bronsted acidsites [24]. The designation of the band at 1450 cm−1 is notclear yet, further study need to be carried out to obtain moreinformation.

Figure 2. IR spectra of thiophene adsorption on NaY (1) and Ce(IV)Y (2)at RT

3.2.2. Adsorption of toluene over NaY and Ce(IV)Y

IR spectra of toluene adsorbed over NaY and Ce(IV)Yat RT are shown in Figure 3. It can be seen that the bandsof toluene adsorbed on Ce(IV)Y (1598 and 1494 cm−1) arethe same as those on NaY, indicating that the adsorptionmodes of toluene on NaY and Ce(IV)Y are identical. This

424 Yanchun Shi et al./ Journal of Natural Gas Chemistry Vol. 21 No. 4 2012

means that the Bronsted acid sites derived from the intro-duction of Ce(IV) in NaY have no effect on the adsorptionmodes of toluene. The vibration bands of ring skeleton oftoluene adsorbed on NaY and Ce(IV)Y appear at 1598 and1494 cm−1, respectively, shifting to lower frequencies com-pared with those of gaseous toluene at 1605 and 1498 cm−1

[26]. This implies that toluene was adsorbed on cation sitesofNaY and Ce(IV)Y zeolites byπ-electronic interaction.

Figure 3. IR spectra of toluene adsorption on NaY (1) and Ce(IV)Y (2) atRT

3.3. Adsorptive desulfurization

The sulfur removal of MG with sulfur concentration ofca. 100 ngS/µL (MG1 to MG5) over NaY and Ce(IV)Y isdisplayed in Figure 4. We can see that the sulfur removal ofMG1 without any toluene was 69.0% over NaY, while it was97.4% over Ce(IV)Y. The result shows that the desulfurizationperformance is evidently improved when NaY is converted toCe(IV)Y. Increasing the content of toluene in MG led to a dra-matic decrease in sulfur removal of NaY, from 50.7% in MG2(the molar ratio of toluene to thiophene is 1 : 1) to only 16.0%in MG5 (the molar ratio of toluene to thiophene is 500 : 1, i.e.,

Figure 4. Sulfur removal (R%) of MGs over NaY and Ce(IV)Y. Conditions:room temperature and atmospheric pressure, adsorption time of 3 h, adsorbentof 0.25 g, MG of 5 mL and sulfur content of 100 ng/µL

with about 16.6 vol% of toluene). Effect of toluene on thio-phene adsorption over Ce(IV)Y, however, is not as evident asthat over NaY. Addition of toluene into MG only resulted ina moderate decline in the sulfur removal over Ce(IV)Y, from85.3% in MG2 to 60.7% in MG5. The sulfur removal of MG5with large amount of toluene over Ce(IV)Y is much higherthan that over NaY. These results show that the cerium ionsintroduced into NaY zeolite by ion exchange play a positiverole in enhancing the selectivity of thiophene adsorption andtherefore, resist the influence of aromatics.

3.4. Mechanism of the inf luence of toluene

The adsorptive desulfurization of MG with and withouttoluene showed that toluene had a negative effect on thio-phene adsorption over both NaY and Ce(IV)Y, but the de-cline tendency of NaY was much steeper than that of Ce(IV)Y(Figure 4). This effect is closely relative to the adsorptionmodes of thiophene and toluene on NaY and Ce(IV)Y. Boththiophene and toluene molecules are adsorbed on Na+ ionsor non-acidic hydroxyl groups of NaY byπ-electronic in-teraction, and their similar adsorption modes are responsiblefor the evident reduction in sulfur removal over NaY (Fig-ure 2(1) and Figure 3(1)). However, there are three adsorp-tion modes of thiophene on Ce(IV)Y:π-electronic interac-tion, direct Ce(IV)-S interaction and protonation of thiopheneon Bronsted acid sites (Figure 2(2)), while onlyπ-electronicinteraction is involved between toluene and Ce(IV)Y (Fig-ure 3(2)). Owing to the higher positive charge and smallerionic radius, the Ce(IV)-S interaction is much stronger thanπ-electronic interaction. This may be the key factor for themuch higher sulfur removal of MG with and without tolueneover Ce(IV)Y than NaY.

Though the Bronsted acid sites lead to the formation ofprotonation of thiophene on Ce(IV)Y, it is not found that theyaffect the adsorption mode of toluene. Moreover, the pro-tonation of thiophene molecules do not result in any reac-tions with toluene, as proved by the GC-SCD results, since nonew thiophenic compounds are detected when MG contain-ing both thiophene and toluene was desulfurized by Ce(IV)Y.Therefore, the Bronsted acid sites of Ce(IV)Y have no obvi-ous effect on desulfurization selectivity when thiophene andtoluene coexist in MG.

4. Conclusions

The introduction of Ce4+ ions into NaY zeolite by aque-ous ion-exchange greatly improves the adsorptive desulfu-rization selectivity to thiophene in MG with and withouttoluene based on static adsorption experiments. The additionof toluene into MG suppresses the desulfurization capacityon NaY steeply, but gently on Ce(IV)Y. Both thiophene andtoluene are adsorbed on NaY byπ-electronic interactions, andthe similar adsorption modes are responsible for the dramaticreduction in sulfur removal over NaY when toluene is added inMG. While there are three adsorption modes of thiophene on

Journal of Natural Gas Chemistry Vol. 21 No. 4 2012 425

Ce(IV)Y, i.e., π-electronic interaction, direct Ce(IV)-S inter-action and protonation of thiophene on Bronsted acid sites, butonly one adsorption mode ofπ-electronic interaction could bedetected between toluene and Ce(IV)Y. Therefore, the directCe(IV)-S interaction plays a crucial role in the adsorptivere-moval of thiophene on Ce(IV)Y, whereas the Bronsted acidsite derived from the introduction of Ce(IV) onto NaY has noinfluence on its desulfurization selectivity from MG contain-ing toluene.

AcknowledgementsThis work was financially supported by the Fundamental Re-

search Funds for the Key Universities (Grant No. DUT10LK25)and the National Natural Science Foundation of China (GrantNo.21106014). The authors are grateful to Mr. BY Zhang of DalianInstitute of Chemical Physics for GC-SCD analysis.

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