One-step synthesis of zinc-encapsulated MCM-41 as H

adsorbent and optimization of adsorption parameters

Nastaran Hazrati

, Ali Akbar Miran Beigi

*,b

, Majid Abdouss

and Amir Vahid

Department of Chemistry, Amirkabir University of Technology, Tehran, Iran.

Oil Reﬁning Research Division, Research Institute of Petroleum Industry, Tehran, Iran.

ABSTRACT

The nano-sized structure of well-ordered Zn@MCM-41 adsorbent

was synthesized through a direct hydrothermal method using CTAB

as a structure-directing agent in an ammonia aqueous solution with

different amounts of zinc acetylacetonate which were inserted into

the structure-directing agent’s loop during the synthesis. The XRD,

HRTEM, and N

adsorption-desorption isotherms were used to

characterize the prepared ZnO functionalized mesoporous silica

samples. As a result, the presence of ZnO in highly-ordered MCM-

41’s pore was proved as well as maintenance of the ordered meso-

structure of MCM-41. The materials were possessed with a high

speciﬁc surface area (1114-509 m

-1

) and a large pore diameter

(4.03-3.27 nm). Based on the obtained results from the adsorption of

S gas in a lab-made setup, the Znx@MCM-41 showed the superior

ability to increase of ZnO amount up to 7 hours as a breakthrough

point. A two factor (zinc percent and temperature) experimental

design with three levels was accomplished to optimize the adsorption

parameters. The inﬂuence of parameters and the interactions on

the adsorption of H

S were studied and optimized. Also, the H

breakpoint curves carried on by UOP163 method.

Keywords:

Zinc encapsulated MCM-41,

S gas,

Adsorption,

Extraction,

UOP163 method

Anal. Method Environ. Chem. J. 3 (2) (2020) 74-81

ARTICLE INFO:

Received 20 Feb 2020

Revised form 19 Apr 2020

Accepted 10 May 2020

Available online 29 Jun 2020

Corresponding Author: Ali Akbar Miran Beigi

Email: miranbeigiaa@ripi.ir

https://doi.org

Research Article, Issue 2

Analytical Methods in Environmental Chemistry Journal

Journal home page: www.amecj.com/ir

AMECJ

------------------------

1. Introduction

In recent years, the preparation and application

of nano-sized materials due to their large surface

areas have received by increasing attention in

various areas of research

[1-5]. Nano-ordered

MCM-41 is a mesoporous well-ordered structure

with a narrow pore size between 1.5 and 10 nm and

a high surface area up to 1500 m

[6-8]. MCM-

41 is a net silica network possessing, the slight

acidity and low-capacity ion-exchange

[9] which

has great uses in many ﬁelds such as catalysis

[10,

11]

, separation [12], medicine [13], and hydrogen

sulﬁde removal

[5, 14-16]. Giving in hand

that pure siliceous MCM-41 may have limited

applications

[17], setting chemical-bonded

functional groups in the MCM-41 channels

[18], make it as a well-heterogeneous reusable

catalyst in most of the reactions. Therefore,

much of the research has been done to prepare

the active substance through the modiﬁcation of

the silicate framework of MCM-41 by inorganic

elements or organic functional groups

[19].

Different methods for inorganic functionalization

of mesoporous silica have been considered like

the addition of inorganic compounds to the

sol-gel mixture

[20], template ion-exchange

S adsorbent by Zn@MCM-41 adsorbent Nastaran Hazrati et al

method [21], impregnation of calcined silica

[22, 23, 5], chemical vapor decomposition [24,

19]

, and using metal-containing templates [25].

Desulfurization process, as one of the main

applications of metal-containing mesoporous

silica, is the most interesting area of research

for lowering the sulfur-containing material,

especially in oil industry

[16, 26]. Hydrogen

sulﬁde (H

S) is a naturally occurring toxic and

malodorous gas contained in most of the world’s

crude oils. Not only it may harm product value,

but also it compromises environmental and safety

compliance, such as infrastructure damages from

corrosion attack, producing odors, and more.

The environmental impacts on the sulfur content

have forced on reﬁners to produce the clean

petrochemical products. That is why managing

hydrogen sulﬁde content is one of the every-stage

challenges hydrocarbon processing, reﬁning,

and transportation

[27]. In different industries,

the H

S can be removed using a variety of the

physical-chemical and the biological methods.

These methods include the Claus process, the

chemical oxidants, the caustic scrubbers, H

scavengers, the liquid amine absorption, the

liquid-phase oxidation, the physical solvents,

as membrane-based processes, biological

procedure, and the adsorptive methods

[27, 19].

After the studies of Westmoreland et al., the H

adsorbents were applied based on zinc, copper,

iron, and calcium oxides as proper elements due to

their thermal stabilities as well as sulfur removal

efﬁciencies. However, based on thermodynamic

point of view, it can be indicated that the ZnO is

an outstanding adsorbent with high efﬁciency for

sulfur removal because of the high equilibrium

constant. Furthermore, the ZnO is considered as

a proﬁtable stable sorbent as compared to many

other metal oxides

[28]. Herein, we described

the characterization and the synthesis of zinc-

incorporated MCM-41 through in-situ insertion

of zinc complexes into the hydrophobic loops of

micelles of structure directing agent. Therefore,

the H

S was efﬁciently adsorbed on zinc-

incorporated MCM-41.

2. Experimental

2.1.

Reagents and Materials

Tetraethylorthosilicate (TEOS),

cetyltrimethylammonium bromide (CTAB), sodium

acetate, zinc acetylacetonate (Zn(acac)

), ethanol,

ammonia and acetone were purchased from Merck

company and used as received without any further

puriﬁcation. All of reagents were purchased from

Merck. Germany.

2.2. Preparation of Zinc-incorporated MCM-41

A mixture of TEOS, cetyltrimethylammonium

bromide CTAB, sodium acetate, ethanol, ammonia,

deionized water (DW) and Zn(acac)

with the

following molar composition (1+5x), 0.3, 1.5, 1,

14, 20 and x was used for the synthesis of Zinc-

incorporated MCM-41. To start the synthesis, the

proper amount of CTAB and sodium acetate was

dissolved in water. Next, the dissolved Zn(acac)

(in ethanol and ammonia) were added to the

solution. While stirring, TEOS was added, and after

70 minutes of stirring in 35°C, the suspension was

poured into the stainless steel autoclave and heated

at 70 °C for 24 hours. The obtained precipitate

was ﬁltered and then, washed with the applicable

amount of acetone and DW, respectively. The

prepared samples were calcined in 550 °C for 5

hours (1 °C min

-1

). The prepared sample of Znx@

MCM, where x indicates the percent of zinc (%)

in the product were characterized by angle X-ray

diffraction, nitrogen physisorption and high-

resolution transmission electron microscopy. Also,

the ability of Znx@MCM for H

S adsorption was

investigated.

2.3. Characterization

X-ray diffraction patterns were recorded on a

Philips 1840 diffractometer with a Nickel-ﬁltered

Cu Kα anode (1.5418˚ A). Textural analyses were

carried out on a Micromeritics Tristar 3020 system

by determining the nitrogen adsorption–desorption

isotherms at -196 °C. Before the analysis, the

samples were degassed in vacuum for 5 hours

at 300 °C until a stable vacuum of 0.1 Pa was

reached. The Brunauer–Emmett–Teller (BET)

Anal. Method Environ. Chem. J. 3 (2) (2020) 74-81

speciﬁc surface area and the total pore volume was

calculated for all of the samples. The mean pore

diameter was determined by applying the Barrett–

Joyner–Halenda (BJH) model. The wall thickness

was calculated as the difference between the

lattice parameter (a0) and the pore diameter.

Transmission electron microscopy (TEM)

images were obtained by a 200 kV Schottky

ﬁeld emitter high resolution transmission

electron microscopy equipped with TEM.

2.4. Desulfurization process

S of Naftshahr crude oil of Iran was extracted

by cold stripping and collecting in a cylinder. The

concentration of hydrogen sulﬁde in LPG was

5000 ppm (mg L

-1

) as the ﬁnal criterion for the

S breakthrough. Adsorption measurements

for H

S were accomplished using a lab-made

setup

(Fig. 1). The reactor efﬂuent stream was

analyzed by UOP163 method which gave the

S breakpoint curves.

3. Results and Discussion

3.1. X-ray diffraction

All of the samples were characterized by

X-ray diffraction (XRD) to get structural

conﬁrmations about the porosity and structure of

the materials. XRD patterns of the synthesized

samples are given in

Figure 2. The low angle

patterns of prepared samples illustrated an

intense peak at about 2.10 ° 2θ assigned to d100

reﬂection which is the typical sign of hexagonal

mesoporous arrangement. The

more amounts of zinc, the lower

intensity of all reﬂections,

especially in d100 plan can be

observed. Consequently, the

distinct decrease of structural

order is caused by high metal

loading and pore fouling.

Then, the less intense reﬂection

caused to the more zinc loading.

On the other hand, the high

angle XRD patterns of zinc

incorporated MCM-41 samples

(Fig. 3) indicate a peak on 36.0° 2θ assigned to

d101 reﬂection which identiﬁes hexagonal zinc

oxide crystals is indeed present inside the pores of

the MCM-41.

Fig. 1. Schematic plan of experimental set-up

Fig. 2. X-ray diffraction patterns of a) MCM-41 b) Zn3@

MCM-41 c) Zn6@MCM-41 d)Zn9@MCM-41

Fig. 3. High angle X-ray diffraction patterns of a) Zn3@

MCM-41 b) Zn6@MCM-41 c) Zn9@MCM-41.

S adsorbent by Zn@MCM-41 adsorbent Nastaran Hazrati et al

3.2. N

Adsorption.

The well-known, nitrogen physisorption

technique was used for determination of the

textural properties of prepared porous materials.

The N

adsorption isotherms of all of the

samples are shown in

Figure 4. MCM-41

(Fig. 4a) shows a type-IV isotherm, which is

a sign to have mesopores. At lower relative

pressure (0.2 to 0.3), the adsorption branch

of isotherm is expected to be the ﬁlling

of mesopores stage with liquid nitrogen

through capillary condensation. In this stage

the sharpness is a sign of size uniformity and

structural order of mesopores.

Desorption branch of isotherms accords with

the adsorption which is an additional sign

of high uniformity of mesopores. Textural

properties of Znx@MCM-41 samples

obtained from XRD and N

adsorption

isotherms are tabulated in

Table 1. From

the table it is observed that the pore volume

of the MCM-41 sample is decreased after

loading inside the pores and the pores are not

completely blocked. Decreasing of speciﬁc

surface area by more loading indicates

insertion of ZnO inside of the mesopores.

3.3. High Resolution TEM (HRTEM)

HRTEM images of Znx@MCM-41 (x=3, 6

and 9) are shown in

Figure 5. Based on the

obtained results, the high ordered array of

the sample shows that the hexagonal structure of

mesopores didn’t damage in the in-situ loading

of zinc.

Fig. 4. Nitrogen adsorption isotherms of a) MCM-41 b) Zn3@

MCM-41 c) Zn6@MCM-41

Table 1. Textural properties of Znx@MCM-41 zinc-containing

samples (x = 0, 3, 6 and 9). a) Volume of mesopores b) d-spacing

from XRD (nm) c) Unit cell parameter (nm) d) Pore diameter

(nm) e) wall thickness from [a - (Wd/1.050)] equation (nm).

Sample name

BET

-1

)

(cm

-1

)

(nm)

MCM-41 1114 0.85 4.01 4.63 3.93 0.89

Zn3@MCM-41 891 0.72 4.24 4.89 4.03 1.06

Zn6@MCM-41 571 0.55 4.05 4.67 3.63 1.21

Zn9@MCM-41 509 0.34 4.12 4.76 3.27 1.65

Fig. 5. HR-TEM images of zinc containing MCM-41. a) Zn3@MCM-41 b) Zn6@MCM-41 c) Zn9@MCM-41.

Anal. Method Environ. Chem. J. 3 (2) (2020) 74-81

3.4. H

S Adsorption

Synthesized samples showed great ability to

remove H

S at standard temperatures. As presented

Table 2, the changes of operating conditions

were resulted by variation in practical temperature

(50, 175 and 300°C), while space velocity in all the

experiments was ﬁxed on 3000 h

-1

. Nine different

experiments, designed based on two factors (A:

zinc percentage and B: temperature), are shown in

Table 2, which also contains the responses in the

last column (tbp). The responses deﬁne hydrogen

sulﬁde breakpoint in the carrier gas, the minute

that H

S concentration in the outlet gas becomes

5000 ppm.

3.5. Effect of ZnO content and temperature

In this work, different amounts of zinc oxide were

incorporated into the pores of MCM-41 by an in

situ approach. It is clear that increasing zinc content

at same operating condition (T: 175°C and space

velocity: 3000 h

-1

) caused noticeable increasing of

adsorption

(Fig. 6). This is attributed to increase in

the active sites by rising zinc oxide loading which

improves the chemical adsorption of hydrogen

sulﬁde on the materials.

The effect of temperature was also investigated.

With the increase in the temperature of absorption,

the H

S breakthrough was occurred later. Moreover

increasing the temperature speeds up the adsorption

by strengthening chemisorption of H

S on ZnO

[15], tbp increases as a consequence.

3.6. Effect of metal modiﬁcation method

The selection of a hydrophobic zinc precursor

(Zn(acac)

) is the main reason to lead the zinc

particles inside of the mesopores of MCM-41

by the inﬂuence of solvent-solute interactions in

synthesis process. As comparing to the previous

work based on wet impregnation for synthesis of

ZnO containing MCM-41

[15], the pore volume

and surface area of Zn@MCM-41 by proposed

method was higher than previous work. Besides the

values of H

S breakthrough in the same operational

condition is considerable. This might be because

of the high dispersion and accessibility of zinc

nanoparticles inside of the mesopores. Furthermore

the smaller size of zinc nanoparticles improves

the selectivity and effectiveness of them in the

adsorption of H

3.7. Analysis of variance

The analysis of variance (ANOVA) on tbp is given

Table 3. If the value of F is more than that of the

F-table at a similar probability level, the factor or

Table 2. The experimental data of the breakpoints

for experiments. (A: Zinc mole percentage B:

Temperature tbp: Breakthrough time)

Run

Independent

Variables

ABt

(min)

Blank 0 50 40.0

1 3 50 135.2

2 3 175 163.1

3 3 300 192.0

4 6 50 171.3

5 6 175 250.2

6 6 300 328.1

7 9 50 232.5

8 9 175 363.4

9 9 300 411.0

Fig. 6. Breakthrough curves of H

S adsorption on

Znx@MCM-41. The box at the right side of the ﬁgure

indicates the run number (Table 1).

S adsorbent by Zn@MCM-41 adsorbent Nastaran Hazrati et al

the interaction is statistically signiﬁcant. The factors

A, B and interaction AB veriﬁed to be statistically

effective on tbp. The greater F the more signiﬁcant

effects on the response. The level of adsorption

is given by regression equation of analysis of

variance. It is consist of the linear relationship

among all of the effects, and the response of the

ﬁnal equations in terms of effective variables is

presented in equation 1:

T = +71.14 + 14.43 A+0.036 B+ 0.081 AB (EQ.1)

According to

Figure 7, the interaction between two

factors may be obtainable which inﬂuences on the

response (tbp) with the conﬁdence level of 95%.

Figure 8 also shows the three-dimensional curves

presenting the impact of temperature and zinc

percentage on the breakpoints. The slope increase

in response, observed on each curve, indicates

that the effect of zinc percentage (factor A) on the

response is greater than the effect of absorption

temperature (factor B).

Table 3. Analysis of variance (ANOVA)

Source Sum of Square Degree of freedom Mean Square F-value P-value (Prob>F) Remark

Model 73838.5 3 24612.8 74.33 <0.0001 signiﬁcant

A-Zn % 44376.0 1 44376.0 134.01 <0.0001 signiﬁcant

B-Temp 25741.5 1 25741.5 77.73 0.0003 signiﬁcant

AB 3721.0 1 3721.0 11.24 0.0203 signiﬁcant

R-Error 1655.5 5 331.1 - - -

C-Total 75494.2 8 - - - -

Fig. 8. Three-dimensional curves presenting the impact

of factors on response

Fig. 7. Interaction between factors and their effect on

breakpoint

Anal. Method Environ. Chem. J. 3 (2) (2020) 74-81

4. Conclusions

Herein nanoparticles of zinc were successfully

immobilized into the mesopores of MCM-41. A

signiﬁcant difference between the presented approach

and the typical in-situ pathways is based on the

precursor’s behavior in the solution. In this process,

Zn(acac)

was located inside the hydrophobic

micelles at which they were arranged by surfactant

(before adding silica source) and after that, the zinc

oxide nanopaticles were anchored onto silica walls.

Although the metal precursor was added in the

synthesis medium, the introduced metal in silica’s

walls is less than other in-situ methods. Notably, the

characterization techniques showed considerably

high speciﬁcation for all of the samples as mentioned

above. The results showed the high capacity of

materials to adsorb H

S. H

S removal from LPG cut

of the studied crude oil in the point of Zn= 9 wt. % and

T = 300°C was adsorbed for about 7 hours in space

velocity of 3000 h

-1

. Additionally, the comparison

between this work with the other published method

showed, the more ability and efﬁcienty extraction of

S gas.

5. Acknowledgements

The authors wish to thank from Amirkabir University

of Technology, Tehran, Iran, Iranian Research

Institute of Petroleum Industry (RIPI) for supporting

of this work.

6. References

[1] C. Bensing, M. Mojić, S. Gómez-Ruiz, S.

Carralero, B. Dojčinović, D. Maksimović-

Ivanić, S. Mijatović, G.N. Kaluderović,

Evaluation of functionalized mesoporous silica

SBA-15 as a carrier system for Ph3Sn(CH2)3OH

against the A2780 ovarian carcinoma cell line,

Dalton Trans., 45 (2016) 18984-18993.

[2] Y. Wan, D. Zhao, On teh controllable soft-

templating approach to mesoporous silicates,

Chem. Rev., 107 (2007) 2821–2860.

[3] A. Sterczynska, A. Derylo-Marczewska,

M. Zienkiewicz-Strzalka, M. Sliwinska-

Bartkowiak, K. Domin, Surface properties of

Al-functionalized mesoporous MCM-41 and

teh melting behavior of water in Al-MCM-41

nanopores, Langmuir, 33 (2017) 11203–

11216.

[4] F.J. Carmona, I. Jimenez-Amezcua, S. Rojas,

C.C. Romao, J.A. Navarro, C.R. Maldonado, E.

Barea, Aluminum doped MCM-41 nanoparticles

as platforms for the dual encapsulation of a CO-

releasing molecule and cisplatin, Inorg. Chem.,

56 (2017) 10474-10480.

[5] M. Abdouss, N. Hazrati, A.A. Miran-Beigi, A.

Vahid, A. Mohammadalizadeh, Effect of the

structure of the support and the aminosilane

type on the adsorption of H

S from model gas,

RSC Adv., 4 (2014) 6337-6345.

[6] M. Thommes, K. Kaneko, A.V. Neimark, J.P.

Olivier, F. Rodriguez-Reinoso, J. Rouquerol,

K.S. Sing, Physisorption of gases, with special

reference to the evaluation of surface area

and pore size distribution (IUPAC Technical

Report), Pure Appl. Chem., 87 (2015) 1051-

1069.

[7] V.B. Cashin, D.S. Eldridge, A. Yu, D. Zhao,

Surface functionalization and manipulation

of mesoporous silica adsorbents for improved

removal of pollutants: a review, Environ. Sci.

Water Res. Technol., 4 (2018) 110-118.

[8] E. Dündar-Tekkaya, Y. Yürüm, Int. J. Hydrog,

Mesoporous MCM-41 material for hydrogen

storage: A short review, Int. J. Hydrog. Energ.,

41 (2016) 9789-9795.

[9] E. Lovell, Y. Jiang, J. Scott, F. Wang, Y.

Suhardja, M. Chen, J. Huang, R. Amal, CO2

reforming of methane over MCM-41-supported

nickel catalysts: altering support acidity by one-

pot synthesis at room temperature, App. Catal.

A: General, 473 (2014) 51-58.

[10] B.S. Kim, C.S. Jeong, J. M. Kim, S.B. Park,

S.H. Park, J.K. Jeon, S.C. Jung, S.C. Kim, Y.K.

Ex Situ, Catalytic upgrading of lignocellulosic

biomass components over vanadium contained

H-MCM-41 catalysts, Catal. Today, 265 (2016)

184-191.

[11] M. Fadhli, I. Khedher, J.M. Fraile, J. Mol.

Catal, Modiﬁed Ti/MCM-41 catalysts for

enantioselective epoxidation of styrene, J. Mol.

S adsorbent by Zn@MCM-41 adsorbent Nastaran Hazrati et al

Catal. A Chem., 420 ( 2016) 282-289.

[12] WY. Sang, OP. Ching, Tailoring MCM-41

mesoporous silica particles through modiﬁed

sol-gel process for gas separation, AIP Conf.

Proc., 1891 (2017) 020147.

[13] E. Beňová, V. Zeleňák, D. Halamová, M. Almáši,

V. Petrul’ová, M. Psotka, A. Zeleňáková,

M. Bačkor, V. Hornebecq, A drug delivery

system based on switchable photo-controlled

p-coumaric acid derivatives anchored on

mesoporous silica, J. Mater. Chem. B, 5 (2017)

817-825.

[14] JJ. Zhang, WY. Wang, GJ. Wang, C. Kai,

H. Song, L. Wang, Equilibrium, kinetic

and thermodynamic studies on adsorptive

removal of H

S from natural gas by amine

functionalisation of MCM-41. Prog. React.

Kinet. Mec., 42 (2017) 221-234.

[15] N. Hazrati, M. Abdouss, A. Vahid, A. A. Miran

Beigi, A. Mohammadalizadeh, Removal of

H 2 S from crude oil via stripping followed

by adsorption using ZnO/MCM-41 and

optimization of parameters, Environ. Sci.

Technol., (2014) 997-1006.

[16] Y.S. Hong, Z.F. Zhang, Z.P. Cai, X.H. Zhao,B.S.

Liu, Deactivation kinetics model of H

removal over mesoporous LaFeO3/MCM-41

sorbent during hot coal gas desulfurization.

Sustain, Energ. Fuels, 28 (2014) 6012-6018.

[17] X. Feng, Z. Yan, N. Chen, Y. Zhang, X. Liu, Y.

Ma, X. Yang, W. Hou, Synthesis of a graphene/

polyaniline/MCM-41 nanocomposite and its

application as a supercapacitor. New J. Chem.,

37 (2013) 2203-2209.

[18] Y. Bao, X. Yan, W. Du, X. Xie, X. Pan, J. Zhou,

L. Li, Application of amine-functionalized

MCM-41 modiﬁed ultraﬁltration membrane to

remove chromium (VI) and copper (II), Chem.

Eng. J., 281 (2015) 460-4607.

[19] D.P. Sahoo, D. Rath, B. Nanda, K. Parida,

Transition metal/metal oxide modiﬁed MCM-

41 for pollutant degradation and hydrogen

energy production: a review, RSC Adv., 5(2015)

83707-83724.

[20] E.P. Baston, A.B. Franca, A.V. da Silva Neto,

E.A. Urquieta-Gonzalez, Incorporation of the

precursors of Mo and Ni oxides directly into the

reaction mixture of sol–gel prepared γ-Al2O3-

ZrO2 supports evaluation of the sulﬁded

catalysts in the thiophene hydrodesulfurization,

Catal. Today, 246 (2015) 184-190.

[21] A. Kowalczyk, A. Borcuch, M. Michalik, M.

Rutkowska, B. Gil, Z. Sojka, P. Indyka, L.

Chmielarz, MCM-41 modiﬁed with transition

metals by template ion-exchange method as

catalysts for selective catalytic oxidation of

ammonia to dinitrogen, Micropor. Mesopor.

Mater., 240 (2017) 9-21.

[22] KS. Kamarudin, NO. Alias, Adsorption

performance of MCM-41 impregnated with

amine for CO2 removal, Fuel Process. Technol.,

106 (2013) 332-337.

[23] S. Qiu, X. Zhang, Q. Liu, T. Wang, Q. Zhang, L.

Ma, A simple method to prepare highly active

and dispersed Ni/MCM-41 catalysts by co-

impregnation, Catal. Commun., 42 (2013) 73-

78.

[24] R. Atchudan, S. Perumal, TN. Edison, YR. Lee,

Highly graphitic carbon nanosheets synthesized

over tailored mesoporous molecular sieves

using acetylene by chemical vapor deposition

method, RSC adv., 5 (2015) 93364-93373.

[25] AA. Gewirth, JA. Varnell, AM. Di Ascro.

Nonprecious metal catalysts for oxygen

reduction in heterogeneous aqueous systems,

Chem. Rev., 118 (2018) 2313-2339.

[26] B. Elyassi, Y. Al Wahedi, N. Rajabbeigi, P.

Kumar, J.S. Jeong, X. Zhang, P. Kumar, V.V.

Balasubramanian, M.S. Katsiotis, K.A. Mkhoyan,

N. Boukos. A high-performance adsorbent for

hydrogen sulﬁde removal, Micropor. Mesopor.

Mater., 190 (2014) 152-155.

[27] S. Jafarinejad, Control and treatment of sulfur

compounds specially sulfur oxides (SOx)

emissions from the petroleum industry: a

review, Chem. Int., 2 (2016) 242-253.

[28] P.R. Westmoreland, D.P. Harrison, Evaluation

of candidate solids for high-temperature

desulfurization of low-Btu gases, Environ. Sci.

Technol., 10 (1976) 659-661.