Luận Án tiến sĩ synthesis of catalysts based on ptsba15 modified with al and or b and their applicability on n heptane hydroisomerization tetralin hydrogenation and paracetamol detection

PAHs are undesired compounds which generate emissions of undesired particles in exhaust gases and decrease the cetane number of diesel ‘The hydroisomerization of n-alkanes and the hydro

MINISTRY OF EDUCATION AND TRANING HANOI UNIVERSITY OF SCHEENCE AND TECHNOLOGY

NGO TIII THANH IHEN

Synthesis of catalysts based on PU/SBA-15 modified with Al and/or B and

their applicability on n-heptane hydroisomerization, tetralin hydrogenation

and paracetamol detection

CIULEMICAL ENGINEERING DOCTORAL DISSERTATION

HaNoi 2020

MINISTRY OF EDUCATION AND TRANING HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY

NGO TIII THANH IHEN

Synthesis of catalysts based on Pt/SBA-15 modified with Al and/or B and

their applicability on n-heptane hydroisomerization, tetralin hydrogenation

and paracetamol deteotion

Major: Chemical Engineering

Code No: 9520301

CHEMICAL ENGINEERING DOCTORAL DISSERTATION

ADVISORS:

1 Assoc Prof Pham [hanh Huyen

2 Prof Graziella Liana ‘furdean

Tla Noi — 2020

1 Assoc Prof Pham Thanh Huyen

2 Prof Graziella Liana Turdean

ACKNOWLEDGEME!

First of all, 1 would like lo thank my advisors Assoc Prof Dr Phara Thanh Huyer

and Prof Dr Graziella Liana Turdean for all support and encouragement which

really helped me and motivated me during my research

T would like to thank Prof Vasile 1 Parvulescu al Deparment of Orgaric Chemistry,

Biochemistry and Catalysis, University of Bucharest, Romania for the support in

hydroisomerization experiments

I would like to thank my friends at HaNoi University of Scionce and Technology

(UST) and at “Iabes- Bolyai” University (UBL) for all assistances and for the

enjoyable time, friendly everts we shared togelher

I would like to acknowledge the Hramus+ Program with partner countries for the financial support of my stages at “Babes- Dolyai” University, Cluj —Napoca,

Finally, I would like to express my deep thanks to my family for all their love,

encouragement and unconditional support throughout my PhD studying,

CONTENTS STATUTORY DECLARATION

CHAPTER 1 LITERATURE REVIEW -

1.1 Mesoporous material and ordered mesoporous silica SBA-15-—

1.2 The modified SBA-15 materials and applications

1.3 The hydroisomerization of n-alkane over bifunctional catalysts

1.3.1 Metal finetion of bifunctional catalyst:

1.3.2 Acid function of bifunctional catalysts—

1.4, Hydrogenation of polymuclear aromatic hydrocarbon (PAHs) ~

1.4.1, Hydrogenation of polynuclear aromatic hydrocarbou (PAHs) —-—-——- 1

1.4.2, Catalysts for PAHs hydrogenation

1.5, Overview of paracetamol detection

2.1.2 Indireet_ synthesis of B/SBA-15 —

2.1.3 Synthesis of P/M-SBA-15 (where M

2.3.2 Transmision electron microscopy (TEM)—~

2.3.3 Fourier lransformed Infrared Spectroscopy (P'I-1R) —

3.1, Léfect of preparation methods of support —-

3.2 Characterizations of modified SBA-15 supports

— 3.2.3 Trangition eleetrơn microscopy (TEM)~

3.2.4, Fourier-transform infrared spectroscopy (I"1R) -

3.2.6 "B MAS-NMR spectroscopy -—

3.2.7 Ammonia Temperature- Programmed Desorption (NIb1PD) ——

3.2.8 FTIR spectra of chemisorbed pyridine

3.3 Characterizations of Pt‘modified SBA-15 catalysts

3.3.1 Nitrogen physisorption isotherms —

3.4.1 Effect of the acidic supports on hydroisomerization activity of catalysts 68

3.4.2 Effect of temperature and reaction time in the hydroisomerization of n-

heplano—

3.4.3 Cracked product yield and coke formation -

3.5 Performance of platinum supported on modified SBA-15 catalysts for

3.5.1 The results of GC-MS analysis of hydrogenation of tetralin

3.5.2 Hifect of reaction temperature and pressure on catalytic activity —

3.5.3 Effect of the acidity of modified supports on catalytic activity — -~

3.6, Application of Plimodified SRA-15 material (or preparing clectrode material

to detect paracetamol _

3.6.1 Characterization of 1%Pt/AIL-SBA-15 catalyst —- — 88

3.6.2 Eleclrochemical characterzaion o[ PƯAISBA-I5-GPBE sleelrode

_ — B5

material —

Differential thermal analysis

Electrochemical impedance spectroscopy Fluid vatalytic cracking

Fourier transformed infrared spectroscopy

Full width at half maximum

Glassy carbon electrode

Graphite paste electrode Inductively coupled plasma method

Light cycle oi]

Limit of detection

Amorphous silica-alumina

Ammonia Temperaiure- Programmed Desorption

Paracetamol

Polynuclear aromatic hydrocarbons

Phosphate buffer solution

WTR spectra of chemisorbed pyridine

Reference cleclrode Silicoaluminaphosphate

Santa Barbara Amorphous No 15

Square wave voltammetry

‘Transmision electron microscopy

LIST OF FIGURES

Fig 1.1, Formation mechanism of MCM-41 suggested by Beck et al " - Fig 1.2 Co-condensalion approach for the ñmetionalization o[ mesoporous

Fig 1.3 Functionalization of SBA-15 through post-grafting - 7

Fig 1.4 Formation of Bronsted acidic site in mesoporous materials - 8

Fig 1.5 Two different tetrahedral structures of boron in B-SBA-15 tramework 8 Fig 1.6 Scheme of n-alkane hydroisomerization over bifunctional catalysts 10 Fig 1.7 Stepwise hydrogenation of an adsorbed tetralin molecule to cis- and trans-

Vig 1.8, Reaction network of tetralin hydrocracking 18 Fig 1.9 Cetane number (CN) of some possible products of naphthalene hydrogenation (CN values according to Santana et aÌ)

Fig 1.10 Reaction scheme for the selective hydrocracking of totralin into BTX .19

Fig 1.11 Chemical structure of PA - - 24 Fig 1.12, Ulectrochemical oxidation of PA co 24 Fig 1.13 Cyclic potential sweup (a) and resulting cyclic vollammogram (b) 27

Fig 1.14 Cyclic voltammogram of a reversible reaction system (a), quasi-reversibl system (b) and irreversible reaction system (c) .2T š Fig 1.15 (a) Scheme of application of potentials of square wave voltammetry method (b) The response contains a forward (anodic, I(1)), backward (cathodic, 1(2)) and net euurent ẢL "¬ soe 28

Fig 1.16 The relation of a real part (7) and am imaginary part (2") in the complex

Fig 1.17 Tho Randles equivalent cirouil- frequenlly used to represent an electrochemical cell [9S] Where: Ca: capacitance of the double layer charging; Ral: the solution resistance; Zr the impedance of the faradic process 30

Fig 2.1 Direet-synthesis of M-SBA-15 (M — Al and/or B)

Fig 2.2 Synthetic procedure of Pi supported on modified supports (ALSBA-1

B-SBA-15, B-SBA-15) HH rereiee

Fig 2.3 Schematic illustration of điữaction aeoording to Brapg”s law 40 Fig 2.4 (a) The high pressure autoclave batch reactor and (b) schematic batch

reaction sysiem used for the r-heptanc hydrowemerization and the tetralin

Fig 2.5 Cyclic voltammogram for a reversible system 47

Fig, 3.1 Low angle XRD patterns of SBA-15, B/SBA-15 and B-SBA-15 AS

Fig 3.2 TEM images of SBA-15 (A), B-SBA-15 (B) and B/S8BA-15(C) 50

Fig 33 Ninogen ađsompliom-desoptien isotherm (A) and BIA pore size distribution (B) of SBA-15, B-SBA-15 and B/SBA-15 àccecoeooeeeoo Ổ]

Fig 3.4 NH:-TTD curves of SBA-I 5; B-SBA-] 5 and B/SBA-1 5

ALSBA-15, ALB-SBA-15; B-SBA-15 (B) - 35

Fig 3.7 TEM images of SBA-I5 (A); ALSBA-IS (B); AL-B-SBA-15 (C) and B-

+ìg 3.8 FTIR spectra of SBA-15 and modifled 8BA-L5 samples S8 Fig 3.9 EDX spectras of ALSBA-15 (A); Al-B-SBA-15 (B); B-SBA-15 (C) 59 Tỉg 3.10 11B MAS-NMR for B-SBA-IS sample occ ses sesnsessieenentnsensinee 60 +ïg 3.11 NHạ-TPD curves of ALSBA-15; ALB-SBA-15; 8-SBA-15 samples 61

Fig 3.12 The Py-FTIR spectras of Al-SBA-1S (A), Al-B-SRA-15 (B), B-SBA-15

Fig 3.13 Nitrogen adsorption-desorplion isotherms and pore sive distribution of

Fig 3.14 Tow angle XRD pallens 0.5%P1/Al-SRA-15 (A), 0.5%PI/AI-B-SBA-15

Fig 3.15 TEM images of 0.5%PVAI-SBA-15, 0.5%PVAI-B-SRA-15 and

O.SYPUB-SBA-LS « oecccecceesecsssstseseessssiessnesssseersvsninenssssseesonssnieersssanenessnvisarsovanen 66

Fig 3.16 NH3-TPD curves of 0.5% PIAI-SRA-15;, 0.5% PIAL-R-SBA-15 and 0.5% PUB-SHA-15 catalysi icon reưưưn, 66

Fig 3.17 Conversion of n-heptane over the three catalysis of 05%PUL/AI-SBA-I 5;

0.59%Pt/AI-SBA-L5 and 0.5%0P13-SIA-15 "—

Fig 3.18 The selcetivily of branched heptamas over the investigated calalysts 70

Fig 3.19 The heptane conversion versus reaction time and temperature over the

Fig 3.20 The variation of the selectivity to branched heptanes versus reaction time

and temperature over the investigated catalysts (PAI-SRA-15 (a), PUAI-B-SBA-15

Fig 3.23 Effect of reaction lemperalure on the conversion of tetralm over

imvestigaled calalysts((A): PVAI-SBA-15, (B): PVAI-B-SBA-15, (C): PL’B-SBA- 15) ‘The reaction condition: liquid phase; reaction time: 3 hours LTT

Fig 3.24 Effect of hydrogen pressure on the conversion of tetralin over invesligaled catalysts ( (A): PUALSBA-L5; (Bì: PYALE-SBA-IS5, (C): PUB-SUA-I5) ‘The reaction condition: liquid phase; reaction time; 3 hows see BB

Fig 3.25 The conversion of tetralin and cis/trans ratio over the investigated catalyst cccesssesstnesnssee SH HH HH H0 are 1 Fig 3.26A IG curves of Pt) B-SBA-15 (A) after reaction eerie BO

Fig 3.268 TG curves of Pt! Al-SRA-15 (B) and PL/Al-B-SBA-15 (C) calalysis afer

Fig 3.27 Square wave voltammograms of 10°M PA at the 19⁄4PƯM-SBA-15-GPE (where M_ Al and/or R) clectrodes in 0.1M phosphate buller (pH 7) - 82

Fig 3.28 Low angle XRD pattem of 1%Pt/AL-SBA-15 catalyst - 83

Fig 3.29 Nitogen adsorption-desorption isotherms at 77K (A) and pore size distribution (B) applying BIH method in the desorplion branch of 1%PUALSBA-15 catalySL con se SE HH nh 2011 are, Xeseeseoo.BỂ

Fig, 3.30 TEM image of 1% PU/ALSBA-15 catalyst - - 85

xi

Tig 3.31 Cyclic voltamrnograrns aL PƯA]-SBA-15-GPE in absence (dot ling) and in presence of 7 x 10' M of PA (solid line) Inset: CV at unmodified GPL in presence

Fig, 3.32 Cyclic voltamopramms of 7 x 10-5 M PA at Pt/Al-SBA-15-GTE recorded

at different scan rate tnsel influence of scar rale on anodic peak currents intensities

at P/AI-SBA-15-GPE (LÐ and GPE (A) cleetrodos (A) 8ƒ

Vigure 3.33 Nyquist plots recorded at PUALSBA-I5-GPL modified electrode (A) and GPE unmodificd electrode (0) (inset) into a solution containing 1 mM K4IFc(CN)61/K3|Fe(CN)6| + 0.1 M phoaphatc baffer (pH ?) 88

Tïg 3.34 Square wave voliamograntns [or đilTerenL cơneenlralion o[ ĐÀ al PUAL SBA-15-GPE modiBed graphite paste electrode (A) and calibrgiơn curve oŸ PWAI- SBA-15-GPE modified graphite paste eleotrode (1) and GPE (A) for PA (B) 90

Fig, 3.35 Square wave voltamogramms recorded at PUAL-SBA-15-GPE modified electrode in a presence of a mixture of 7 x 10-6 M paracetamol, 9x 10-3 M ascarbic acid and 10-6 M uric acid - - 1 Vig 3.36 SWVs (A) and calibration curve (83) for detection of PA from tablets using PYAI -SBA-15-GPE modified electrode - - 92

‘Fable 3.5 Acidic properties of AI-SBA-15, Al-L-SBA-15, B-SBA-15 samples

according te NLIs-PD ¬ ÒÒÒỒÔ 61

‘Table 3.6 Surface area and pore size of catalysts and the corresponding supports

HH HH Hee 61

Table 3.7 Results in NH3-TPD of catalysts

‘on of n-heptane over the PisM-SBA- 5(M Al andéor BY

Table, 3.9 Coke content determined from the thermogravimetry analysis af the

Table 3.10 Tetratin conversion and selectivity of products - - 79

‘Table 3.11 Surface area and pore size of Al-8I3A-15 support and 1%PUAI-SBA-1S

‘Fable 3.12 ‘rhe electrochemical parameters of the Pt/AI-SLA-15-GPLi electrode

Table 3.13 Slope of log I versus log v depenrdenee see BB

Table 3.14 RIS filling parameters for Pt/ALSBA-15-GPE modified electrodes 89

Table 3.15 Determination of PA from pharmaceutical tablets using Pt/Al-SBA-15-

xiii

INTRODUCTION

During the last two decades, the synthesis of mesoparons materials is one of the

most aliractive and success(ul achievements in material science and catalysis In many

publications of mesoporous material, SBA-15 (Santa Barbara Amorphous) material is

the most frequently studied due to its interesting properties, such as high surface area,

large pore size, thick wall and high thermal stability However, the lack of acidily hinders applications of SBA-15 material as catalyst ‘Ihe ordered mesoporous material

SRA-15 was first synthesized im 1998, since then the funclionalivalion and

modification of this material has attracted much attention and opened many now applications not only in optics, sensing, adsorption, drug delivery but also in catalysis

In general, most studies focus on the substituting of the Si atoms or grafting new

functional groups towards its application as photocatalyst, acidic catalyst or catalyst for

oxidation, enzyme immobilization,

Recently, the growing energy crisis, living standard anc population led to the

increasing demand for the petroleum fuels It is essential to produce fuels with

enhanced quality to increase combustion efficiency and reduce the generation of

pollutants, such as particulate matter (PM 2.5) and photochemical smog For this purpose, the hydroisomerization of n-alkanes to branched isomers with high octane

number has received much atierition The incroase of oclanc number of produced

gasoline by hydroisomerization is very different from that of the conventional fluid catalytic cracking (FCC) because FCC’s gasoline is rich of olefins and aromatics which gonorate big amounl of PM 2.5 and photochemical smog duc to thoir incomplete combustion ‘Io meet the demand for high quality diesel fuels, the hydrogenation of polynuclear aromatic hydrocarbons (PAHs) is also an important process to produce good performance diesel fuel with low aromatic content PAHs are undesired compounds which generate emissions of undesired particles in exhaust gases and

decrease the cetane number of diesel

‘The hydroisomerization of n-alkanes and the hydrogenation of PALIs have often been investigated over bifunctional catalysts which have metal sites for

hydrogenation/dchydrogenaliơn and acid sites [or isomerizalion Cmlalylic selivily, stability and selectivity, of these catalysts depend on the characteristics of the acid

sites and metal sites, on the metal-acid functions balance The previous researches

showed that noble metal (such as Pt, Pd) are the most used metals for supplying metal sites due to their strong hydrogenation activity and high stability In many reported researches, lo improve [he vatalytic performance of the hydroisomerization and the hydrogenation, various supports as metal oxides, zeolite (Y, beta, mordenite, ZSM-5), silicoahminophosphate, carbides of transition metal, pillared clays or mesoporous materials (MCM-41) have been investigated However, the high conversion usually

leads to low selectivity to branched isomers ‘lhe Bronsted acid sites increased cracked products and micropores limited the diffusion of isomers to the bulk phase prior to

consecutive undesired cracking reactions In Viet Nam, isomerization of n-alkane has

been studied over many catalysts such as MoOQs/Zr02-SOx, PtAVOs-ZrO2/SBA-15,

Pt'yALOs, Pa/HZSMS catalysts promoted by Co, Ni, Fe, Re, However, most of

studies were performed at the mild condition without hydrogen pressure

For SBA-15 material, the incsopores structure exhibits the good mass transfer

and allows the diffusion of large reactamts to the surface ‘he substitution of Si by AI,

B generates the acid sites Moveover, the previous studies showed that boron promoter

could decrease the coke formation and improve the catalyst stability

L'rom above mention, in order to exploit the attractive structure properties of

mesoporous SBA-15 material, the bifunctional catalysts based on Pt‘SBA-15 modified

with Al and B were chosen for the disserlation The efTcet of heteroatom nature on the

acidic properties of modified M-SBA-15 supports and bifunctional 0.5% Pi/M-SBA-15

catalysts (where M = Al-, R- or Al-R-) were studied The catalytic activity of the

investigated catalysts in n-heptane hydroisomerization and tetvalin hydrogenation were

discussed

Tn electrochemistry, the SBA-15-based malerials recently have been aliraclive

compounds used for the chemical modification of electrode surfaces ‘'he mesoporous

structure is likely to impart high diffusion rate of target species The uniform

mesosiuclure, high surface area of SBA-15 could improve the cloctroactivily of

modified electrode

On the other hand, platinum is a noble metal which has good activity, high

clectrical conductivity, roproducibility at clectrochemical conditions Platinum nanoparticles have also been widely employed as modifiers for electrochemical deleclion of organic molecules Therefore, platinum mmoparticles supported em modified mesoporous material can be considered as electrochemical catalysts to improve the performance of sensoring processes

Paracctamel is an analgesic and antipyretic agent extensively recommended for treating pain and fever In the case of overdose, the accumulation of its toxic

metabolites may cause kidney and liver damage Therefore, the determination of

paracetamol has received much attention In this dissertation, the 1% Pt/M-SBA-15

catalysts (where M = Al-, B- and AIB-) were synthesized and their applicability in the

electrochemical delection of paracetamol were also studied

The objective of the study

The purpose of the thesis is to synthesize the effective catalysts based on

PYSRA-I5 modifed wilh Al andor Bo and ther applicability im mrheplane hydroisomerization, tetralin hydrogenation and paracetamol detection

The scope of the research is to:

- Synthesize M-SBA-15 materials and the corresponding (0.5%; 1%) Pt M-SBA-

15 catalysts (where M = AL, B- or AL-B-)

- Tnvestigate the offecl of beloroalom nature on the sơidie properties of

modified M-SBA-15 supports and bifunctional 0.5% Pt/M-SBA-15 catalysts (where M

= AL, B- or AL-B-)

- Investigate the applicability of these catalysts in n-heptane hydroisomerization, tetralin hydrogenation

- Investigate the applicability of 1% PtM-SBA-15 catalysts in electrochemical

detection of paracetamol using chemically modified elcerodes

THE NEW CONTRIBUTION OF THE DESSERTATION

The effect of Al and B incorporated SBA-15 support on the acidic properties

and catalytic activity of the supported PUM-SBA-15 (where M — Al-, B- and Al-R-)

catalysts have been investigated The obtained results contributed to knewledge about

the influence of acidic support on the performance of bifunctional catalysts

The investigaled bifunctional catalysts have been applied in the hydroisomerization of n-heptane and the hydrogenation of tetralin at the reaction

condilion of liquid phase, hydrogen high pressure These resulls showed their potential

application in industrial catalytic processes

Chemically modified electrodes based on an ordered mesoporous structure

incorporating Tt nanoparticles (Pt/Al-SBA-15-GPE electrode) were prepared, characterized and applied for the detection of PA The well-obtained values for the

analytical parameters (sensibility, limit of detection, linear range, no interference)

could recommend the potential application of this composite electrode materials [or

identifying PA in real samples

CHAPTER 1 LITERATURE REVIEW

1.1 Mesoporous material and ordered mesoporous silica SBA-15

According to TUPAC nomenclature, mesoporous matenals are materials which have pore sizes between 2 and 50 nm The researchers of Mobil Oil Corporation

introduced the first family of mesoporous silica materials M41S in 1992 These materials have received much attention due to their high surface area and uniform pore

size 2-10nm [1] Types of different structures were obtained depend on the different

used synthesis conditions such as hexagonal MCM-41, cubic MCM-48, laminar phases

MCM-SO The interaction between templates and inorganic species affects the structure

of obtained materials

The ‘liquid crystal mechanism’ of MCM-41 which was suggested by J.S Beck

et al [2] was illustrated in Fig 1.1

structure serverite Micellar

Sohtical mi mice

_

Silica cesar gp Fcalctnation

Fig 1.1 Formation mechanism of MCM-41 suggested by Beck et al [2]

Spherical micelles assemble in hexagonally ordered cylindrical micelle when the silica precursor is added Silica condensation around ordered micelles makes the

silica walls The templates are removed in caleinations to give the porous ordered materials,

In 1998, Stucky and coworkers reported a new mesoporous silica material SBA-

15 (Santa Barbara Amorphous) through using nonionic copolymers as organic structure

directing agents SBA-15 has the hexagonal structure with ordered mesopores up to SOnm, high surface area (600-1000 m?/g) and thick pore wall (3-6nm) [3] These

characters enhance SBA-15 thermal and hydrothermal stability compared with

MCM-41 Beside the uniform mesopore, SBA-15 has micropores in the mesopore walks These micropores interconnect hexagonally ordered mesopores in SBA-15 structure

The formation mechanism of SBA-15 is similar to the formation of MCM-41 Silica precursor, types of template, pH of solution, are the important factors that influence the characterization of obtained SBA-15

Some pure silica sources used for synthesis of SBA-15 are alkoxides such as tetramethylosthosilieate (IMOS) or tetraethyl orthosilicate (LHOS), ]4] By using amphiphilic tiblock copolymer as template, the ordered hexagonal SBA-15 was synthesized in strong acidic conditions (pH-1) When pH is over the isoclectrie of silica (i.e, at plI=2-6) precipitation or formation of silica gel couldn’t occur At neutral

pH of 7, the formation of disordered or amorphous silica may occur

1.2 The modified SBA-15 materials and applications

Although SBA-15 has many good propertics such as high surface area, hydrothermal stability, its applicability in catalysis is limited due to the lack of

acidily Many efforts which include funclionalivalion of surface and deposition of

active metal on the materials to active the surface and create acid sites have been carried out The functional mesoporous materials of SBA-15 have opened many

opportunities for its application in catalysis

Various methods have been used to modify SI3A-15, which includes

functionslization of surface and deposition of active melal on the materials

i, The functionalization can be proceeded directly (direct synthesis) or post-

grafting [5][6]

- Dircet synthesis: Silica sources (TEOS, TMOS, ) were co-condensed

with organotrialkoxysilane in the presence of different templating agents, as shown in

Fig 1.2 In this way, obtained materials often applied for the adsorption of heavy metals such as mereury, lead,

silanol group occurred using solvent under reflux condition, After that, covalent

attachment of functional groups was formed on surface of material

Fig 1.3 Functionalization of SBA-15 through post-grafting [5][6]

ii, Deposition of active metal to SBA-15 includes metal incorporation, ion

exchange, incipient wetness impregnation

- Metal incorporation method: the metal precursors are added during

synthesis process Metal atoms are incorporated into the framework or dispersed on the

surface The direct- introduction of heteroatoms into framework of SBA-15 is difficult

because metal ions are created easily under strong acidic hydrothermal condition

- Incipient wetness impregnation: a metal salt solution is added to the

support corresponding to the pore volume of the support The obtained material is dried

and calcined

Due to the attractive structure properties, after functionalization with active

species on the surface of material, SBA-15 has been the subject of numerous

investigations, ie., oxidative transformation of hydrocarbons [7,8], reduction processes

[9], Knoevenagel reactions [10], waste water treatments [11,12] and carrier

applications in drugs-delivery [13]

Heteroatoms with valence lower than silicon, auch as Al, Fe, Cr, B,

introduced into framework of SBA-15 creates negative charges [14-17] Acidity of

modified SBA-15 was generated due to compensating negative charges by protons

[14,15] The mcorporation of Al and B m the framework of SBA-15 to modify its

acidity has been reported Alminum incorporation in the SBA-15 framework creates a

large mamber of Bronsled and Lewis acid sites on the surface of mesoporous malcrial

Bronsted acid sites of mesoporous materials containing aluminum are created by

bridging hydroxyl groups, as illustrated in Fig 1

Fig 1.4, Formation of Bronsted acidic site in mesoporous materials {14/

According to Chen et al [15,18] boron remains at tetrahedral boron sites in B- SBA-15 framework Ths sile can Mexibilily iransform between trigonal and tetrahedral

Fig 1.5 Two different tetrahedral structures of boron in B-SBA-15 framework [15,18]

The studies of Gricken [17] and Szczodrowski |19|showed a significant enbance

of acidity of AI-SBA-15 compared to parent SBA-15 support or B-SBA-15 The

modified SBA-15 provided 2 belter dispersion of active species 2s compared to the pure SBA-I5 and ahunina supported catalyst [20] The bifunctional catalysts containing noble metal nanoparticle and acidie ordered mesoporous M-SBA-15 showed good catalytic activities for the hydroisomerization of n-dodecane [21], the hydrogenation of anthracene [21], the hydrocracking/hydroisomerization of alkanes

[22]

In electrochemical applications, chemically modified electrodes based on SBA-

15 derivatives offer attractive features likely to be exploited, such as the increase of mass transport, rapid electron transfer, casy to develop and good analytical parameters

In Viet Nam, the modified and functionalized SBA-15 material has been received much attention by scientists at Institute of Chemistry — Vietnamese Academy

of Science and Technology, VNU University of Science, HaNoi University of Science

and Technok

Ta Noi University of Mining and Geology, University of Science —

Hue University, Quy Nhon Universtiy, Ho Chi Minh cily University of Technology

The available publications of Viotnamese rescarch teams have summerized as follow

-Eunctonalization of SBA-15 with 3-mercaptopropyl trimethoxyxilane for

adsorption of Pb [23]; SchifT-base groups for Suzuk ross-coupling ru tim [24]

- Metal incorporation into SBA-15 framework: Fe-SBA-15 for the oxidation of phenol red reaction [25]; synthesis and characterivalion of A-SBA-15 [26], Ti: SBA-15

II

- Hybrid mesoporous SBA-15 for inmobilization onto SBA-15 of enzyme [28]

- Metal, metal oxide, mixed oxides supported SBA-15 as Ti containing SBA-15 for photocatalytic oxidation of phenylsulfophtalein [29], Cu/SBA-I5 for oxidation of styrene [30] and oxidation of LPG [31]; VO,/SBA-15 for oxidative dehydrogenation of

rebutane, WO3/7102 supporled on SBA-15 for n-heptane isomerization [32]

1.3 The hydroisomerization of n-alkane over bifunctional catalysts

The hydroisomerization of n-alkanes has played an crucial role in the modem petroleum industry to produce green gasoline and diesel with high quality, low content

of olefins and aromatics [35, 36]

w-alkane a noatkowe THO -athylearhentue lon

a fs

monobranched _ manobranched & cracked

|

alkane — alkylcarbendam iaa———* product

Fig 1.6, Scheme of nealkane hydroisomertzation over byfimetional catalysts (35)

‘Typically, the hydroisomerization of n-alkanes takes place over bifunctional calalysis which have metal siles for hydrogenation! dehydrogenation and acid sites [or isomerization The general scheme of n-alkanc hydroisomerization is shown in Figure

16

The classical isomerization mechanism conlains consecutive steps First, the dehydrogenation of n-alkanes is catalysed by platinum sites generating the corresponding n-alkenes After the protonation of n-alkenes on acid sites, the created carbenium ions were rearranged and followed by deprotonation on acid sites and hydrogenation into i-alkanes on metallic sites [36 38] ‘The hydrocracking reaction always takes place during the hydroisamerization of n-alkane because the iso-alkenes intermediates suffer the bond cracking of C-C on acid sites, thus that reduces the yield

of the branched hydrocarbon Accordingly, a metal-acid balance of the bifunctional

10

cølnlyslz is neocasary Lo achieve ä lúph hyđroisomerizatiơn nolivily and a limiisliơn of

the cracking reaction

1.3.4 Metal function of bifunctional catalysts

The transition metals as Pi, Pd, Re, Ir, Ni, Co, have been employed for

providing metal sites of bifunctional catalyst [30] Amơng these metals, catalysis

loaded with Pt or Pd are the most used metal sites in the industrial application of n-

alkane hydroisomerization due to their song hydrogenation activity and high stability

[40] The previous rescarches showed the mictal loading at the range of 0.4 — 0.6% which revealed the good acid metal balance of bifunctional catalysts In many metal

loading methods, precipilalion and impregnation arc main methods used in industry

[#1

The effects of different platinum precursars as Pt(NOs)2, IbPtCh, PiCh,

Pi(NAs Ch and (NH4)PtCla on catalytic behaviors of PUZ.SM-22 calalysts were

investigated by Wang et al ‘Ihe results of Wang [34] showed that the LbPtCle

precursor presented the highest metal dispersion while the Pi(Il) precursors produce

larger Pt particles Therefore, lhe prepared FPiCls calalysis demonstrated Ingher

catalytic behaviors It is also found that in the presence of hydrogen, the Pt sites can

hydregenate coke precursors maintaining the stability of the catalyst [42, 43]

Recently, the use of a second metal in the synthesis of bimetallic bifunctional catalysts has been investigated Yang and Woo [4] studied the hydroisomerization of 1rheptane using the PI-lr/NaHY and PYNaHY catalysts The results showed dhat the higher behavior was realized and the coke formation decreased over Pt-lr/NallY catalyst compared with that of Pt-NaELY catalyst

In the researches of Bauer et al [45], the Pt-Pd/zeolite beta catalysts were prepared and tested for the m-hexadecane hydroisomerization The investigated

catalysts demonstrated a larger dispersion of bimetallic sites due to the imtimate

interactions between two metal components and their similar lattice constants So that

11

the bimetallie bifunctional catalysts revealed the higher calalytic activity compared with monometallic ones

Fswaramoorthi and Lingappan [46, 47] reported the hydroisomerization of n- hexane and n-hoptanc using Pt-N/SAPOs (SAPO-5 and SAPO-11) catalysts The results indicated that introduction of Ni led to the modification of the metal-acid balance due to the increase of the bimelallic sites dispersion and covered acid sites The best yield of isomer products was obtained over the optimum catalyst containing Pt of

0.2% and Ni of 0,4 %

1.3.2 Acid function of bifunctional catalysts

Acid function of bifunctional catalysis for the hydroisomerization process arc provided by supports typically including metal oxides, zeolite (Y, beta, mordenite, ZSM-5) In the recent researches, many materials, such as silicoaluminophosphate,

carbides of transilion metal, pillared clays or mesoporous materials (MCM-41,

modified SIUA-15) have been used as a support In general, the researches aim to adjust

the acid strength or the structure of the catalyst ta get the metal-acid balance although

thal is too hard to be reached [48]

1.3.2.1 Bifunctional catalysts with amorphous inorganic oxides

Alumina or amorphous silica-alumina (MSA) are supports used for the first

commercial catalysts of n-alkane 1somerization Corma et at [49] studied the

hydroisomorization of n-decane, n-hexadevane over the P/MSA catalysts, The results showed that the best selectivity in hydroisomerization of n-hexadecane obtained over the 0.6% PUMSA catalysts Calemma ct al [SO] alsa studied PUMSA catalysts for the

hydroisomerization of n-octacosane, n-hexatricosane, n-tetra-tetracosane All catalysts

presented the isomerization yields lower than 65% and the yield decreases with increasmg the length of the n-alkane chain

1.3.2.2 Bifunctional catalysts with super acid solids

The PSOvZrO2 and PtwOs/4rO2 catalysts were studied in the

hydroisomerization of n-hexadecane by Wen et al and Keogh et al [51] They showed

12

the very high acidily, thus the isomerization selecHvily wus low œven sĩ low conversion In the presence of hydrogen, 80% of n-hexadecane was cracked over

PYSO4/7s0, catalysts at 150 °C These catalysts also revealed a low stability at high

temperature [52]

1.3.2.3 Bifunctional catalysts with zeolite support

‘Leolite possesses acidic sites on high surface area, large pore volume, high

adsorplion capacity, thus the bifunctional metal supported zeoktes favored for

hydroisomorization The acidity of zeolites is genorally very strong because they usually possess strong Bronsted acid sites Accordingly, the strong cracking activity

red

lhe yield of isomer products especially lor the hydroisoueization of long chain

nealkanes

Park et al [35] studied the hydroisomerization of n-hexadecane over

bifunctional catalysts conlaining zeohte supports as 7SM-5, 7SM-22, Y, Reta al 350°C

and 103 bar It was found that the catalytic activity depended on the acid strength of

catalysts The conversion was in the range of 37 — 45 wt The Pt’Y catalyst showed

the isomer scleclivity of 15.6-75.7%

On the Pt (0.3%)/2SM-22 catalyst, Claude et al [53] investigated the

Tn some recent researches, (he weakening of zeolite avidity hay boon considered

as an effective route to enhance zeolite-based bifunctional catalysts performances ‘fhe changing, of the ion-exchange solutions and the mixing of acid supports with additional chemicals with weaker acidity are the most selected ways to decrease the Bronsted acidity of zeolite, Wang et al, [5] used the NILNOs/(NIL:)2Sil's mixture as the ion- exchange solution instead of NHiNOs to modify 7.SM-22 support When studying the hydroisomorization of n-dodecane, the yicld of i<dodecane increased from 38.8% to 77% Zhang, et al [55] studied the hyđroisomerizatian of n-hexadecane over the Pt/Eu-

13

1~Z8M-4R calalysl The oblained yield of i-hexadceane aver Pi/Fu-1-7,SM-48 catalyal

was higher than that over PU Lw-l or PUZSM-48 catalysts due to the combination of the large Bronsted acid density of Fu-1 and the mild Bronsted acid strength of 7SM-48

1.3.2.4 Bifunctional catalyst with silicoaluminophosphases {SAPOQ-n) acid

supports

Beside zeolite, zeolite like silicoaluminophosphate (SAPO) materials are the

important molecular sieve materials used in hydroisomerization The SAPO-n supports

(n-11, 31 or 41, respectively) generally have weaker acidity than zeolites (54, 56]

Acid Bronsted sites of SAPO-n were formed due to the substitution of Al or/and P

atoms by Si aloms and had strong clfecls on catalytic behaviour The bifunctional catalysts based on Pt/SAPO-n have been reported

The Pt (1%/SAPO-n (an = 11, 31 or 41) catalysts were used for the

hydroisomerizalion of n-oclane al the temperature range of 200-400°C, under

atmospheric pressure [56] ‘The results showed that the hydroisomerization reaction rate

was controlled by the diffusion The activity of investigated catalysts were reduced in

the order SAPO-41 SAPO-11> SAPO-31 because the acid siles and acid strength of SAPO-41 and SAPO-1] were higher than that of SAPO-3E

The ydroisomerization of n-hexane, n-oclane and n-hexadecane over Pt(0.5%\VSAPO-11 and -31 has been studied by Sinha et al |57| The investigated catalysts showed the most reactive only for n-hexadecane while the least reactive was

obtained for n-hexane These resulis demonsirated the P/SAPO-n catalysis were

suitable for long-chain n-alkane hydroisomerization

Kim et al [58] found that the consecutive oracking reactions could be prevented

by reducing the extemal Bronsted acid sites, thus the catalytic performance of

Pt/SAPO-11 would be enhanced A series of hierarchical SAPO-11 were synthesized

by using various templates as methyloctadecyl (ST-SAPO-11) or carbon (C-SAPO-11)

In the case of using methyloctadccy! lomplalc, Bronsted avid siles were mainly located

at the outer surfaces of SAPO-11 crystals In contrary, most of Bronsted acid sites still

locate in the microporous channel wher usitys carbon templates The internal Bronsted

14

acid sites [acllitale (he 1someri⁄ztlon winle he consecntive craocking reacliom 1s

catalysed by the external Bronsted acid sites Accordingly, the results of the n- dodecane hydroisomerization showed higher yield of i-dodecane aver PLC-SAPO-11 than that over PYST-SAPO-11 catalyst,

1.3.2.5 Bifunctional catalysts with mesoporous materials

Mesoporous materials (such as MCM-41 and SBA-15) exhibit very good

properlies for mass transfer due to their mesoporousity These malertals possess the

wide pore diameter, high surface arca and the thermal stability affording a diminution

of the diffusion limitations for branched alkanes isomers [59, 60] ‘the substitution of

Si by Cr, La, Ce, Zn, B, Fe, Ga, Ti, V, Sn or Al, B led an incr:

stability [61, 62] Noble metals (Pt or Pd) dispersed on AIL-MCM-41 [63] or AL-SBA-15

[64, 65] showed a high activity for hydroisomerization By using hydrothermal

procedures, P T Huyen et al synthesized AI-SRA-15 and ZSM-5/SBA-15 (75C)

composite Ihese supports were loaded by 0.5% Pt and investigated in the

the micro/mesoporous Y/MCM-41 composite and studied the influent of the

mesoporous MCM-41 on catalytic activity of the Pt-loaded Y/MCM-41 catalyst in the n-decane hydroisomerization, where YAMCM-/1 support was the composition of mesoporous MCM-4l and zoolite Y The investigated catalysts showed the high n- decane conversion, the good selectivity to mono-branched isomers compared with that

of PUY catalyst The mesoporous MCM-41 presence improved the metal-acid balance and reduced the diffusion limitation to large molecules, thus couresponding positive effects to the performance of Pt-loaded Y/MCM-A1 catalyst

In summary, an ideal bifunctional catalyst for the n-alkanes hydroisomerization should achieve high isomerization selectivity simultaneously with the least formation

of cracked products It was necessary to reach the balance between acidity and

15

hydrogenation avtivily and the proper pore channel for the enhancement of catalytic performance lence, beside metal function, textural properties of support, pore size,

surface area, acidity, are crucial parameters of hifunetional catalysts

In the researches of n-alkanes hydroisomerization over bifunctional catalyst,

SAPO-n and zeolites are the most studied acid supports Catalysts containing these supports showed an improvement of catalytic porformance duc 10 thew agidity and porous structure They also exhibited a very high sensitivity to HạO, 5 in the feedstock

and eliminated the corrosion, that solved the limitation of the chlorinated ALO;

catalysts However, the catalytic conversion over Pt/zcolite catalysts was not sufficiently high simultaneously with high selectivity to branched isomers ‘Ihe

Bronsted acid sites increased cracked products and micropores limited the diffusion of

isomers to the bulk phase prior to conseoutive undesired cracking reactions

Isomerization of n-alkane has been studied by many scientists in Viet Nam

Research Leams of VNU University of Science stuclied isomerization of n-hexane andl n-heptane over MoOs/ZrO2-SO4"] 66], PW O3-Z102/SBA-15 |32| catalysts The teams

of HaNoi University of Science and Technology reported the isomerization of n-

hexane over PUyAbOa catalyst [67] n-hexane hydroisomerization over PdIZSM5 catalysts promoted by Co, Ni, Fe, Re were investigated by scientists at Io Chi Minh

City University of Technology [68] However, most of studies were performed at the

mild condition without hydrogen pressure

From above contents, the mesoporous materials showed potential supports for

bifunctional catalyst of hydroisomerizvalion For SRA-15 talenial, the substitudon of Si

by Al, B generates the acid sites which acted as the acidic sites of bifunctional catalyst The mesopores exhibit the good mass transfer and allow the diffusion of large reactant

to the surface Therefore, in this thesis, the effect of heteroatom nature on the acidic

properties of PYM-SBA-15 (where M = Al, B- and ALL-) and the catalytic activity

em teheplane hydroisomerialion were sludied

16

1.4 Hydrogenation of polynuclear aromatic hydrocarbon {PAHs)

1.4.1 Hydrogenation of potynuclear aromatic hydrocarbon (PAHs)

Ilydrogenation of PATIs has been applied to upgrade quality of heavy fuels and increase celane number (CN) of diesel LCO (light cycle ail) from fluidized catalytic cracker (FCC) contains an appreciable mumber of PAHs They caused negative

ifluences on diesel fuel due to their low CN, high density and the generation of

undesired particles in cmnissions Thorefore, hydrogenation of PAHs has beer studied

up to now

PALs hydrogenation is a complex process taking place in consecutive steps Hydrogenation activity increased with the number of aromatic rings in molecules (69|

‘The hydrogenation of the first rings in PALIs molecule was easier than the

hydrogenation of the last remaining ring In the heavy fuels, tetralin is one of the

tvpical PAHs So it was often selected as a model compound to study in PAHs

‘Tetralin was hydrogenated in sequential steps via A”!° and A!#_octalin to cis- and trans-decalin The pathway which proceeds through Al octalin is the main

reaction way

Sato et al [71] studied reaction mechanisms of tetralin hydrooracking over

NiW/USY zeolite catalysts Reaction network of tetralin hydrocracking is illustrated in

Fig 1.8 The obtained products were classified into 3 groups: (i) eis-deoalin and trans- decalin as hydrogenation products; (ii) isomerization, hydrogenolysis, hydrocracking,

products that include 2- methylindan, u-bulylbenenc, iso-bulylbenzene, and volatile

compounds ., (iii) naphthalene

+00 > CO-O7-0% ~ naphthalene tetratin dcculin — methylperhydr-

Fig 1.8 Reaction network of tetralin hydrocracking [71]

The similar products of tivalin hydrocracking are obtained Bifunctional catalysts presented higher activity than metal-catalysts in PAHs hydrogenation reaction [72-74] Beside the hydrogenation on melal sites, the acid sites of the support also participate in the hydrogenation reaction |75, 76] Composition of products depend on metal activity and acidity of supports

18

+m

Me-c-hexane

CNe38

Ring I Rir + ms tp Opening Là Opening ng

Fig 1.9 Cetane number (CN) of some possible products of naphthalene hydrogenation

(CN values according to Santana et al [79])

= LPG

Naphtha

Fig 1.10 Reaction scheme for the selective hydrocracking of tetralin into BTX [78]

Ferraz et al [77] researched hydrogenation, hydrocracking of tetralin and its reaction intermediates using NiMo catalysts supported on alumina, silica-alumina, and

alumina Y- zeolite Cetane number of some possible products were reported (Fig 1.9)

19

Colane Number (CN) values in Fig 1.9 show thal CN of product enhance significantly if aromatic saturation followed by selective ring opening of naphthenic

strictures

Selective hydrocracking of tetralin for light aromatic hydrocarbons was studied

by Lee et al [78] over Ni/Ni-Sn/CoMOS catalyst supported on H-Beta (Fig 1.10) The rosulls showed thal Ha/telralin molar ralio lower than 4 increases naphthalene and CO+ aromatic in product The high selective hydrocracking of tetralin into BIX was achieved at 1i/tetralin molar ratio higher than 4

To summarize, the available ways to upgrade polynuclear aromatic fractions to fuels are aromatic saturation; mild hydrocracking and aromatic saturation followed by selective ring opening of naphthenic structures Although these routes lead to significant product quality enhancement, they suffer fiom several disadvantages Ilydroeracking leads to significant yields in gasoline-range products, aromatic saluration is characterized by a telalively high consumption of hydrogen with only limited improvement of product quality in torms of density and cotane properties, while the combination of the two approaches leads to higher improvements of product quality bul il requires ä very high hydrogen consumplion which strongly afTects the economics

of the process An alternative upgrading route consists in partial polyaromatic

compound saluralion to produce less condensed structures

1.4.2 Catalysts for PAHs hydrogenation

1.4.2.1 Catalysts for upgrading polynuclear fractions

The hydrogenation of PAHs has boen sludicd extensively using dilTerent catalysts such as solid acidic catalyst; metaV/acidic support catalysts; metal/non-acidic

supports; homogene ous catalysts

- Solid acidic catalysts:

Chareonpanich et al [80] used USY-zeolite for thermal cracking at 600°C, total

yield of benzene, loluene, xylene, and light hydrocarbons (methane, ethane, propanc)

obtained approximately 100% Coke and tar were not detected Mechanism showed

20

that hydrocracking of diphenylmethane, n-butylberwenc, and Iotralin wore [onned by hydrocracking of C-C bond Ilydrogenation of aromatic ring was the first step and

hydrocracking reaction was the subsequent step In the case of 1-methylnaphthalene,

aromatic ydrogenation took place prior to hydrocracking of methyl group Hydrocracking of anthracene and phenanthrene trend to crack at outer rings

Yur ot al [81] studicd new catalysis impregnated on active carbon, included pentachloro antimony, trimethylsilyl trifluoro-methane sulfonate, isometric pentachloro-antimony The results revealed that Car-Caz bond of di(1-naphthyl) methane could be cracked to naphthalene and 1-methylnaphthalone on the catalyst at

300 °C under hydrogen pressure ‘the solid acid had higher activity in hydrocracking

reaction Hz was dissociated to non-active H’ and active H' Step of attaching active H'

to iso site of di{]-naphthyl) methane was the deciding step of hydrocracking process

- Catalyst of metal/acidic support

Matsuhashi et al [82] exammed hydrocracking reaction over PƯAlsOk calalysl which was synthesized by impregnation method The influcncos of synthesized

condition on dispersion as well as the influence of dispersion on reaction rate were

considered earelully This research showed thal_reavtivily of calalyst was alTected by PL precursor and the dispersion of Pt impacted well to reaction rate

Fan et al [83] studied anthracene hydrocracking reaction to ethyl bipheny] over

NiFe/HZM-5 catalyst In the presence of water, liquid products yield increased and yield of gas products decreased Without water and CO, nitrogen compound would

poison catalyst, gave bad influences on process [84] Mixture of COz and water could

limit that problem and give higher yield if there was no nitrogen compound in the feedstock Hawever, some of nitrogen compounds such as pyrrole, pyridine and 2-

methylpyraine could also cnhanee the reaction in the presenee of CO2 and water

Calemma et al [85] reported results of PAIs hydrocracking reaction over Ir and

Pt on various supports such as ZSM-12, super durable zeolite Y (SiOz/Al;O;=200

molMmol) and zcolitc HSZ-390HUA, amorphous mesopore $i02-ALOs and ALOs-B

21

The results exhibit that properties of products depend on characterization of supports

and used metals

Tailleur et al [86] applied WNiPd/CeY-AhOs catalyst for the conversion of

heavy paraffin and aromatics into a high-quality diesel fraction This research showed that the presence of two acid strengths that had different affection to paraffin and

aromalies tsomerizalion, ring opening, and cracking reaction The aromatic adsorption

on acid sites reduces the cracking rate and improves the formation of di- and tri- branched paraffin

- Catalyst metal/ non-acidie supports

Llaas et al [87] reported the conversion of cis-decalin at a hydrogen pressure of 5.2 MPa and temperature of 250-110 °C using Ir and Pt/SiO2 Ơn the Ir/SiO; catalysts, this reaction started at 250-300 °C The hydrogenolytic opening of one six-membered ring to form the direct ring —opening products butyleyclohexane, 1-methyl-2-

propyleyclohexane and 1,2-diethyloyclohexane was the first step The lydrogenolysis

of endocyclic C-C band into open chain decanes or exoclyelic C-C bond into methane

and C9 naphthenes C9 naphthenes could be converted ta C9, C10 hydrocarbon by

ondocyclic hydrogenolysis

On the PUSiOs catalysts, the devalin conversion started at higher temperature of 350-400 °C The products have a large content of teiralin, naphthalene, spiro [4,5] decane and butyl cyclohexane

- Tlomogeneous catalyst:

Guan et al [88] studied 2 stages of residue oil hydrocracking The first stage

was the hydrogenation at low temperature and the second one was the thermal cracking

at high temperature Anthracene product was hydrogenated at 416°C using

homogencous catalyst of FeSQ4 and (NH¿j}Mo}Os4H5O, the conversion of anthracene reached 51% Ilowever, the used catalyst couldn't be separated from the

products

22

1.4.2.2 Catalysts for tetralin hydrogenation

Tetralin, one of the typical FAIIs in heavy fraction, has usually been used as model compound to investigate the hydrogenation Tetralin hydrogenation was studied

in liquid phase by Rautanen et al on Ni/AlOs catalyst over a temperature range of 85-

160 °C and a pressure range of 20 - 40 atm Tetralin was diluted by decane solvent with

the ietralim concentration of 5, 10,15 mol% [89]

Wiliams et al [70] reported the hydrogenation of tetralin on Pt/AlnOs, Pt/ASA,

PYSiO2 catalysis al the condition of 50 atm and 180 °C The resulls showed that

Pt/SiO2 has the lowest activity

Valles et al [90] researched experimental design optimization of the tetralin

hydrogenation over Tr-Pt-SBA-I5 at the reaction condition of Sal of hydrogen

pressure, a temperature range from 200 220 °C and at 3h and 5 h of reaction time

The 1%[r-0.8%Pt-SBA-15 catalyst showed the best yield to cis-decalin of 71% at the

temperature of 200 °C

Mouti et al [91] studied the quality improvement of hydrotreated LGO on

PrvAI-SBA-15 and P/HY catalysts The results showed that the secondary cracking

products were observed on PW/ILY catalysts, whereas PVAI-SI3A-15 catalyst was

effective in aromatic saturation without secondary cracking Thus, cetane number of producls increased strongly over P/AI-SBA-15 catalyst while thal couldn’ improve effectively on PUHY catalyst

Tn the large number of reports, mesoporous materials sucl as hexagonal

mesoporous silica have becn received attontion in recent years duc to their high surface

area, large pore volumes Compare with MCM-4] and other supports, SI3A-15 material

shows ils advantages as large pore diameters ranging, thicker pore walls and beltor hydrothermal stability ‘fhe incorporation of Al in the framework of SBA-15 creates the acidity at moderate level which is suitable for the preparation of bifunctional

catalyst

23

Therclore, im this thesis, (ctralin was chosen as mods! reactant and the catalyuc

behaviors of Pt’M-SBA-15 catalysts (where M= Al and/or B) on tetralin hydrogenation

because PA is extensively recommended for treating pain and fever In the case of

overdose, the accumulation may cause kidney and liver damage So, it is very

important to research/develop methods for detecting paracetamol rapidly and

24a

oxidalion was illustraled in Fig 1.12 PA suffers a redox reaction mvelving Lwo electrons and two protons to form N-acetyl-p-quinoneimine [92]

1.5.2 Electroanalytical methods based on using chemically modified electrodes (CMEs) for paracetamol detection

Various methods are available for determination of paracetamol mì

pharmaceutical formulation, such as: optical method, chromatographic methods,

capillary electrophoretic methods [93,94] and electroanalytical raethods

Eloctroanalytical methods based on using chemically modified clectrods have received overwhelming interest because they have more advantages over the other sophisticated metheds such as: relatively low cost, [asl response, simple instrumentation, high

sensitivity, facile miniaturization, and low power requirement

In electroanalytical methods, a redox reaction is studied in an electrochemical

cell conlairong an analyte When an appropriate potential is applied, the reduction or

oxidation of a substance take place at the surface of a working clectrodc The potential

related to the redox process and/or the current intensity related to quantitative

properlics are measure Therefore, substances can bơ seleclively celeoled by electrochemical methods The values of the electrochemical parametres provide strong,

tiformalion tnvolving the concentralion, kineties, and mechamsm of reaction in

solutions

Electrochemistry based on the charge transfer process take place at the interface between electrode and solution A general redox process can be desoribed by the following reaction

whore: Cx is the oxidized species, Red is the reduced species, z is the number of the electrons involved in the redox process

An electrochemical cell needs at least 2 electrodes, but most common

electrochemical cells have a three electrodes system

25