Synthesis and modification of zr sba 16 as catalyst for alkylation reaction

3.2 Catalytic activity of Zr-SBA-16 and their derivatives on alkylation 55 3.2.1 Effect of ratio Zr/Si on reaction conversion 55 3.2.2 Effect of temperature on reaction conversion 59 3.2

VIETNAM NATIONAL UNIVERSITY HOCHIMINH CITY

HOCHIMINH CITY UNIVERSITY OF TECHNOLOGY



TRAN BA LUAN

SYNTHESIS AND MODIFICATION OF Zr-SBA-16

AS CATALYST FOR ALKYLATION REACTION

( TỔNG HỢP VÀ BIẾN TÍNH Zr-SBA-16 LÀM XÚC TÁC PHẢN ỨNG ALKYL HÓA )

Major : Chemical Engineering Code : 605275

MASTER’S THESIS

HO CHI MINH CITY JULY 2013

CÔNG TRÌNH ĐƯỢC HOÀN THÀNH TẠI TRƯỜNG ĐẠI HỌC BÁCH KHOA –ĐHQG -HCM Cán bộ hướng dẫn khoa học : P.Giáo sư – Tiến Sĩ Nguyễn Ngọc Hạnh

Thành phần Hội đồng đánh giá luận văn thạc sĩ gồm:

1 Tiến sĩ Huỳnh Kỳ Phương Hạ

2 P.GS TS Nguyễn Ngọc Hạnh

3 Tiến sĩ Nguyễn Quang Long

4 Tiến sĩ Lý Cẩm Hùng

5 Tiến sĩ Hồ Quốc Phong

Xác nhận của Chủ tịch Hội đồng đánh giá LV và Trưởng Khoa quản lý

chuyên ngành sau khi luận văn đã được sửa chữa (nếu có)

OF TECHNOLOGY

MISSION MASTER’S THESIS

Full name: Tran Ba Luan Student number: 11880184

Date of birth : 07/08/1978 Place of birth: Vinh Long

Major : Chemical Engineering Code : 605275

- Modification of Zr-SBA-16 by chloride compound

- Characterization of as-prepared materials

- Study of their catalytic activity on the Friedel-Crafts alkylation of toluene

III START DATE : 21/01/2013

IV COMPLETION DATE: 21/06/2013

V SUPERVISOR : Prof.Dr Nguyen Ngoc Hanh

Ho Chi Minh City- 31 st , July, 2013

ACKNOWLEDMENT

First and foremost I offer my sincerest gratithude to my supervisor, Prof Nguyen Ngoc Hanh, who has supported me thoughout my thesis with her patience, motivation, enthusiasm and immense knowledge Her guidance helped me in all the time of research and writing of this thesis

Besides my advisor, I would like to thank teachers in Faculty of Chemical Engineering, HoChiminh City University of Technology for helping

me in encouragement, insightful comments

Last but not the least; I would like to thank my family supporting me spiritual throughtout my life

Tran Ba Luan

ABSTRACT

Chloride-promoted zirconium was supported on mesoporous pure silica

SBA-16 (abbreviated Cl-Zr/SBA-SBA-16) It was prepared by direct wet impregnation and reflux methods, followed by thermal decomposition The as-prepared materials were characterised by TDP-NH3, XRD, FT-IR spectroscopy, TEM and SEM images, ICP analysis and nitrogen adsorption-desorption measurements The results showed that the 3D cubic arrangement of mesopores corresponding to the Im3hm space group of SBA-16 was retained with the presence of zirconium extra framework about 2% and a change in pore size distribution as well as pore thickness It could be assumed of restructuration of active sites on internal surface for a potential strong acid catalyst For application, liquid - phase alkylation of toluene and benzyl chloride to form 1- methyl –4 (phenylmethyl) benzene and 1-methyl –2 (phenylmethyl) benzene using Zr-SBA-16 and Cl-Zr-SBA-16 as catalyst were investigated The influence of reaction parameters such as reactant ratio, temperature, time was studied In this work, the optimum conditions for the alkylation reaction were found to be 0.2g catalyst and volume ratio of toluene and benzyl chloride of 1:1

at 110 oC After 6 hrs, this reaction reached approximately 71% of conversion with a selectivity of 54 % of the main product This catalyst could be reused for several cycles with minimal loss of catalyst activity

DECLARATION OF ORGINALITY

I hereby declare that this is my own research study The research results and conclusions in this dissertation are true, and are not copied from any other resources The literature references have been quoted with clear citation as requested

Dissertation Author

Tran Ba Luan

1.3.2 Friedel-Craft alkylation using solid acids 21

2.3 Catalytic studies – The Friedel-Craft alkylation reaction 36

3.2 Catalytic activity of Zr-SBA-16 and their derivatives on alkylation 55

3.2.1 Effect of ratio Zr/Si on reaction conversion 55 3.2.2 Effect of temperature on reaction conversion 59 3.2.3 Effect of catalytic contents on reaction conversion 61

Figure 1.1 Structures of SBA-15 and SBA-16 01

Na2SiO3.9H2O with surfactants 04

Figure 1.7 Mechanism of MPV reduction and B–V oxidation of carbonyl compounds over

Fig 1.9 Effect of reaction temperature (X4) and catalyst loading (X5) on the yield to FAME

Figure 3.16 Reaction conversion on difference of ratio Zr/Si 56

Table 1.1 Activity of solid acid catalysts for acylation 17

Table 1.3 Activities [total conversion (XT, mol%)] and selectivities of the

Table 1.4 Reusability experiments of Ga-20-A in the alkylation of toluene

Table 1.5 Activity of Zr-SBA-16 (conversion, mol%) in the Friedel-Crafts

Table 1.6 Conversion (mol%) in the Friedel-Crafts alkylation of toluene

Table 3.4 Reaction conversion of difference ratio of Zr/Si ( impregnated chloride) 56

LIST OF ABBREVIATIONS

ICP Inductively coupled Plasma

FR-IR Fourier transform infrared spectroscopy

SEM Scanning electron microscopy

SBA Mesoporous SBA-type silica materials

TEM Transmission electron microscopy

TDP-NH3 Temperature-programmed desorption of ammonia XRD X-ray powder diffraction

XPS X-ray Photoelectron Spectroscopy

Zr-X Zr-SBA-16 with a theoretical Zr/Si, ratio of X%

CHAPTER 1 – LITERATURE REVIEWS

1.1 INTRODUCTION OF SBA MATERIALS

1.1.1 SBA materials

In recent years, there have been many studies about mesoporous silica (MCM-41, MCM-48, SBA-15, SBA-16 ) as catalytic support because of their unique properties such as high specific surface area, well-ordered, evenly pore structure for facile dispersion of active component and for diffusion of great size molecules In addition, they have high activity and selectivity, appropriate acidity and optimal metal support interaction Zhao et al reported the synthesis of a variety of mesoporous SBA-type silica materials (SBA = Santa Barbara Amorph), using non-ionic triblock copolymers as template This surfactant is very interesting, because it is easily separable, nontoxic, biodegradable, and inexpensive Typification of the SBA-n-type mesoporous silica materials are SBA-15 and SBA-16

Figure 1.1 Structures of SBA-15 (left) and SBA-16 (right) [26]

SBA-15 materials are prepared under acidic conditions with the

mesopores are ordered in hexagonal arrays providing the same long range space group as for MCM-41 materials (P6mm) However, due to the properties of the pluronic type surfactant, SBA-15 materials show up important differences in porosity and adsorption properties compared to MCM-41 materials In a regular synthesis, SBA-15 materials have much thicker but still amorphous walls and primary mesopore diameters between 5

nm to 15 nm The BET surface area of SBA-15 is generally lower than the one

of MCM-41 Due to thicker pore walls, it is hydrothermally stable Also due to the pluronic surfactant type, SBA-15 materials generally have a second intrawall porosity consisting of micropores or smaller mesopores These unordered pores interconnect the primary mesopore channels It is possible to tailor the micro/mesopore ratio to the needs of the application, still conserving the rather thick pore walls The intrawall microporosity is caused by the penetration of the hydrophobic PO groups of the block copolymer chain into the silica matrix The thick wall is caused by the length of these polymer chains [4,5]

Among the reported 3-D cubic mesoporous silica materials, SBA-16 appears to be one of the best candidates for catalytic support or absorbent because of the good thermal stability due to thick wall, economical synthesis

with inexpensive silica sources, and large pore [4,5,26] SBA-16 is a porous

silica with large pores (5-15 nm) cage-like mesopores arranged in a three dimensional cubic body-centered Im3m symmetry It is synthesized in acidic conditions, using a nonionic pluronic surfactant (Figure 2.2) and is therefore providing an intrawall complementary porosity [26] The mesophase can be

or in a ternary water, butanol and pluronic F127 system Caused by the longer

PO chains in pluronic F127 compared with pluronic P123, SBA-16 generally has thicker pore walls than SBA-15

The structure of SBA-16 can be described by a triply periodic minimal surface of I-WP (body centered, wrapped package) as represented in Figure 1.1 The mesophase might also be a triply periodic minimal surface As suggested by electron crystallography studies [26], each mesopore is connected to eight neighboring mesopores for SBA-16 Thereby the pore entrance size from one mesopore to another is usually significantly smaller than the primary mesopore size, making this size the limitary factor for applications involving intraparticle mass transfer The desorption out of this kind of structure is dominated by so called pore blocking and networking effects The primary mesopore size can relatively easy be obtained by diffraction or physisorption measurements in combination with an adapted geometric model like the model of spherical cavities or the triply periodic I-

WP surface In contrast, the pore entrance size is more difficult to obtain Analyzing the desorption physisorption isotherm a first guess of a maximal diameter is possible If the desorption occurs spinodal at a pressure of about

will cause a shift of the desorption isotherm towards higher pressures Pore entrance sizes greater than 4 nm can thus relatively straight forward be characterized by physisorption measurements Using probe molecules of large kinetic diameters and analyzing their sorption properties it is also possible to characterize entrance sizes below 4 nm [14]

In the report of V T Le et al [4,5], the synthesis of SBA -16 included two steps: hydrolysis and condensation of silica source TEOS has been preferred because of its advantages: easy to use (liquid with low viscosity), nontoxic, and the most important is their feasibility to control hydrolysis and condensation process They have sometimes modified the properties of the product by partly replacing the non-ionic template pluronic F127 by CTAB or TTAB, or adding n-butanol to have a spherical form with various sizes

However, one of the problems limitted the application of these materials has been their high price in synthesis from precursor TEOS In their work, they synthesized the SBA-16-type mesoporous silica by using sodium metasilicate

as silica source and a two-step process In fact, the process in second step was rather complex The condensation rate of metasilicate was much more different from TEOS and affected by many factors (surfactants, stirring, temperature…)

Figure 1.2 Powder X-Ray diffraction of as synthesized SBA-16

prepared from Na2SiO3.9H2O with surfactants[4]

Beside of using sodium metasilicate as silica source, Q K Dinh et al

synthesized successfully SBA-16 from husk as silica source replacing TEOS

[29]

1.1.2 Synthetic mechanism of SBA-16[14]

1.1.2.1 The Sol-Gel Process

The sol–gel method constitutes nowadays an important route to synthesize porous silica without involving the deployment of excessively high temperatures: additionally, this experimental technique allows one to control,

to a certain extent, the sizes of the solid particles constituting the silica aerogel

or xerogel The pathways leading to porous ordered materials are very similar

to the sol-gel process where the polymerization is carried out in an aqueous solution by adding a catalyst and a source of silica The silica source is an important factor for the reaction conditions Common molecular sources are alkoxysilanes like tetramethyl- and tetraethyl-orthosilicate or sodium silicate Non-molecular silica source are, for example, already polymerized sol-gel materials which lead to non-homogeneous solutions The first step of polymerization is the formation of silanol groups by hydrolysis of the alkoxide precursors, the gel, in aqueous solution:

The polymerization occurs through water (oxolations) or alcohol (alcoxolations)-producing condensations:

- Si-OH + HO-Si-  -Si-O-Si- + H2O

1.1.2.2 The Template Pathway

The main way to obtain a well defined and structured SBA-16 material is

to use a surfactant templated polymerization instead of an uncontrolled reaction (Figure 1.2) The organic-inorganic self-assembly is driven by noncovalent weak bonds such as hydrogen bonds, van der Waals forces, and electrovalent bonds between the triblock copolymer surfactant and inorganic species Instead of a simple superposition of the weak interaction, an

integrated and complex synergistic reaction facilitates the process Cooperative assembly between poly (ethylene oxide)-poly (propylene oxide)-

and inorganic precursors is generally involved, forming inorganic/organic mesostructured composites In general, the amphiphilic surfactant molecules form a liquid crystal by aggregation in aqueous solution The formation of the liquid crystal matrix strongly depends on the conditions in the solution The structure of the liquid crystal is called mesostructure Important parameters for the mesophase formation are for instance the temperature, concentration or the pH-value of the solution

Figure 1.3 Schematic representation synthetic method of SBA-16

In order to act as a structure directing agent, the mesophase has to interact in some ways with the silica precursors There have been many different attempts to develop pathways to influence the interactions between mesophase and polycondensation reaction of the silica source Stucky and co-

-I+ and S-X+I-, (S+ ) surfactant cations, (S- ) surfactant ations, (I+) inorganic

oligomers from tetraethyl orthosilicate (TEOS) As mentioned before, the nonionic routes templated with amphiphilic triblock copolymers are used to synthesize the SBA-16 material These routes are relatively new and have shown a high flexibility in tailoring the synthesis conditions and the

mesostructure of the liquid crystal template

1.1.2.3 Removal of template

The porosity can only be obtained after the removal of template from the as-synthesized inorganic-organic composite Different removal methods certainly influence the characteristics of SBA-16 mesoporous materials The most common method to remove the template is calcination due to the easy operation and complete elimination Organic surfactants can be totally decomposed or oxidized under oxygen or air atmospheres The temperature programming rate should be low enough to prevent the structural collapse caused by local overheating A two-step calcinations was adopted by Mobil scientists—the first 1 h under nitrogen to decompose surfactants and the following 5 h in air or oxygen to burn them out This complicated procedure was then simplified; the first calcination step under nitrogen can be substituted

by low rate heating in air Heating the as-synthesized SBA-16 material with a rate of 1–2°C/min to 550°C and keeping this temperature for 4–6 h can completely remove triblock copolymer templates The calcination temperature should be lower than the stable temperature of the mesoporous materials and higher than 350 °C to totally remove PEO-PPO-PEO type surfactants

Nicolet 6700 FT-IR Spectrometer

Number of background scans:128 Number of sample scans: 128 Resolution: 2 cm-1

Figure 1.4 Typical IR spectra of SBA-16 [26]

Higher calcination temperatures would lead to lower surface areas, pore volumes, surface hydroxyl groups and higher cross-linking degrees of mesoporous materials The drawbacks of calcination are the non-recovery of surfactants and the sacrifice of surface hydroxyl groups Extraction is a mild and efficient method to remove surfactants and to get porosities without distinct effects on frameworks Ethanol or terahydrofuran can be used as an organic extracting agent A small amount of hydrochloric acid is added in the extracting agent to improve the cross-linkage of frameworks and to minimize the effects on mesostructures With the aid of sulfuric acid, triblock copolymers in SBA-16 mesostructure can be removed, and tailored pore channels and structures can then be achieved In addition, new procedures including microwave digestion photo-calcination as well as supercritical fluid extraction were also applied and turned out to be beneficial for some ordered mesoporous materials Figure 1.5 corresponds to a typical HRTEM image of

SBA-16 in which both the structural order as well as the cubic symmetry of this material can be observed

Figure 1.5 Typical HRTEM image of SBA-16 [26]

1.2 MODIFICATION OF SBA MATERIALS

1.2.1 Zirconum and its oxide

Zirconium is a transitional metal with the symbol Zr, atomic number of

40 and atomic mass of 91.224 The name of zirconium is taken from the mineral zircon, the most important source of zirconium It is a lustrous, grey-white, strong transition metal that resembles titanium Zirconium forms a

dioxide and zirconocene dichloride, respectively Five isotopes occur naturally, three of which are stable In Viet Nam, mineral zircon concentrates at the beach of Quang Ninh, and some center provides as Ha Tinh, Quang Binh, Thua Thien Hue

Zirconium is element of IVB group, with electron structure:

confused with zircon), is a white crystalline oxide of zirconium Its most naturally occurring form, with amonoclinic crystalline structure, is the mineral baddeleyite

in Fig 1.6, this requires that zirconium should be considered within an coordinated active structure Such a structure requires four positive ions (protons) for electrostatic neutrality However, it would seem that the structure

suitable for high-temperature reactions A six-coordinated structure with a net negative charge of two appears more likely A structure similar to that of

Figure 1.6 Eight-coordinated structure of SiO 2 -ZrO 2 [22]

1.2.2 Modification of SBA materials by Zr

It was thought about the metals and their oxides (Sn, Zr, Ti, Fe,

could give strong acid sites through the framework substitution of silica matrix Among different hetero atoms and their oxides, zirconium oxides and zirconium containing compounds have got significant attention in using as catalyst even as support They possess high mechanical with high extreme hardness, chemical, thermal stability, high specific mass, especially both acidic-basic and redox properties available for various reactions However pure zirconia has very unpromising textural properties such as low specific

in application as catalyst In order to overcome these limitations and improve catalytic property of zirconia, its combination into the framework of mesoporous silica has been interesting research There are mainly two methods used for this purpose: direct and post synthesis In the direct synthesis, zirconia incorpration is fulfilled during hydrothermal synthesis of mesoporous silica, so better dispersion of active sites and homogeneous distribution of metals would be obtained for a more stable and dispersed framework as well

as no chance for partial pore blockage In post synthesis zirconia is

Figure 1.7 Mechanism of MPV reduction and B–V oxidation of carbonyl compounds

over supported metal species

In their work, Nanzhe Jiang and his co-workers studied the grafting Zr- and Sn to SBA-16 by the microwave synthesis method These Zr (Sn)-SBA-16 mesoporous silica materials were proven to have tetrahedral-positioned Zr and

Sn species Zr- and Sn-incorporated mesoporous silica materials were applied

in activation of ketones by Lewis acid sites to catalyze Meerwein–Ponndorf–Verly reduction of cyclohexanone and Baeyer–Villiger oxidation of adamantanone, respectively Optimum incorporated Zr- and Sn-species gave almost 100% selectivity with high activity into corresponding alcohol and lactone, respectively [6]

The production of biodiesel by methanolysis of highly acidic crude palm oil has been optimized using Zr-SBA-15 as heterogeneous acid catalyst A dual optimization procedure had been carried out by using surface response methodology and selecting the yield towards fatty acid methyl esters (FAMEs)

as main response factor

Figure 1.8 Zr-SBA-15 as an acid catalyst for produring biodiesel

Quadratic equations were obtained for both models and their statistical analysis led to the optimal conditions for Zr-SBA-15 synthesis (0.67 N HCl concentration, ageing temperature of 130 °C, Si/Zr molar ratio of 10), and for the transesterification reaction in autoclave, conditions (209 °C, 12.45 wt% catalyst loading, 45.8 methanol to oil molar ratio) Under these optimized

conditions FAME yield reached 92 mol% after 6 h Additionally, reusability tests revealed that the optimized Zr-SBA-15 catalyst displays an excellent reaction stability, being fully regenerated after calcination at 450 °C [18]

Fig.1.9 Effect of reaction temperature (X4) and catalyst loading (X5) on the yield to

FAME (Y) for the methanolysis of crude palm oil

In the study of Hai-Ou Zhu, SBA-15 was supported 12-phosphotungstic acid catalyst exhibits much higher catalytic activity, selectivity and stability than H-Y zeolite in the alkylation of benzene with 1-dodecene at reaction temperature of 80°C, with the 1-dodecene conversion of nearly 90%, 2- phenyldodecane selectivity of nearly 40%, and monoalkylbenzene selectivity

incorporating zirconium into SBA-15 mesoporous molecular with various loadings of tungsten oxide, followed by calcining at different temperatures

To evaluate the catalytic activities of the prepared materials, the benzoylation of anisole was chosen as the model reaction All the results reveal that the synthesized samples are strong solid acids, even solid superacids under some conditions, with evenly mesoporous structure and high

acidity and catalytic activity of the materials These materials possess both strong Lewis and Brønsted acid sites on the surface, and exhibit considerably high catalytic activity for the benzoylation of anisole The dispersion state of

the catalysts The high acid strength and high acidity were correlated to the

surface of Zr-SBA-15[12]

Figure 1.10 Structure of WO3/Zr-SBA-15[12]

for the acylation of aromatics which has been known to be catalyzed only by

homogeneous catalyst The solid superacids were found to exhibit extremely high activities for the reactions such as dehydration of alcohol), double-bond isomerization of l-butene, isomerization of cyclopropane to propylene, esterification of terephthalic acid, and polymerization of ethers [19,22]

by adsorption or desorption of water molecules as figure 1.11 The acid

H2S04

Figure 1.11 Brønsted and Lewis acid site of SO 42-/ZrO 2

Sulfated zirconia showed the strongest acidity in comparison with other

Table 1.1 Activity of solid acid catalysts for acylation

Zr elements in the bridging bidentated state, as Okazaki et d proposed in the case of titanium oxide with sulfate ion The double-bond nature of the complex is much stronger compared with that of a simple metal sulfate Thus,

effect of S = O in the complex, as illustrated by arrows in the previous scheme

If water molecules are presented, the Lewis acid sites would be converted to Brønsted acid sites [22]

InVolkan Degirmenci ’s study, zirconia /SBA-15 becomes a very active

catalyst for the selective hydrolysis of cellobiose to glucose after sulfation Spectroscopic investigations indicate the presence of Brønsted acid sites with similar properties to those present in conventional sulfated zirconia The catalytic activity in cellobiose hydrolysis correlates well with results for temperature-programmed decomposition of i-propylamine for a range of

In addition, T,T.Nguyen synthesized biodiesel by esterification reaction

pores, evenly pores distribution and strong acidity

In most cases the electrophilic agent is the carbocation that is generated when the halide acts as a leaving group The role of acid catalyst is to complex

The aromatic electrophilic substitution reaction takes place in two

regenerate the aromatic ring

The mechanism is concerning to an electrophilic agent substitution

Figure 1.12 Mechanism of the Friedel-Crafts alkylation reaction

Although the most common method for generating the electrophilic for alkylation reaction employs an alkyl halide and aluminum chlorine It can be generated in other ways also For example, the reaction of an alcohol and an acid to produce the carbocation

Alternatively, the carbocation can be generated by protonation of alkens This reaction resembles the addition to alkens

1.3.2 Friedel-Craft alkylation using solid acids

Alkylation of aromatic compounds is an important area of industrial research Benzylated aromatics, a class of alkylated aromatics, are very useful intermediates in petrochemicals, cosmetics, dyes, pharmaceuticals and many other chemical industries They are formed by replacement of a hydrogen atom of an aromatic compound by a benzyl group derived from benzylating

The liquid –phase reactions has been traditionally catalysed by Lewis

homogeneous sytems are the production of significant quantities of hazardous waste (e.g salts, acids ) that needs thourough washing and neutralization as well as the difficulties in catalysts recovery So, the limitations in the homogeneously acid-catalyzed reactions are no possible reuse, trouble some

work-up and also low product selectivity [1]

Heterogeneous acidic catalysts in the liquid-phase have certain advantages over the homogeneous ones They offer easier separation and recovery of the products and catalyst from the reaction mixture They are reusable Thus, shape selective heterogeneous catalysts are very capable of replacing traditional homogeneous Friedel–Crafts catalysts Besides providing

the recovery and reusability advantage, the higher selectivity can have economic advantages also Often separation of the desired product from the reaction mixture is easier, resulting in lower energy costs Because of these advantages, research on the synthesis of Friedel–Crafts type benzylated aromatic compounds using shape selective solid acids as catalyst has increased over the past decade

Various types of strongly acidic zeolite catalysts, such as H-ZSM-5, Hb,

HY and HSY are reported for the liquid-phase Friedel–Crafts type benzylation

by benzyl chloride of benzene and other aromatic compounds Recently, the report that a complete or partial substitution of Al in H-ZSM-5 zeolite by Ga

active in the benzylation process All observations clearly show that, for the Ga- and In-modified zeolite catalysts, although the zeolitic acidity is also important, the concentration of non-framework Ga or In in the zeolite is more important for their high catalytic activity in the benzylation reaction

been reported for the benzylation by benzyl chloride of benzene and other aromatic compounds It is important to note that, among these metal chloride

With the advantages of SBA-15 and SBA-16 materials as in 1.1, there are

a lot of studies for modifying this materials by some metals to use as a catalyst

in Friedel–Crafts alkylation reaction Maria J.Gracia and co-workers had reported activity of Ga- and Al-SBA-15 materials in the Friedel-Crafts alkylation of toluene with benzyl chloride or benzyl alcohol

In their work, Ga-, Al- and AlGa-SBA-15 mesoporous materials were synthesized by a direct sol–gel hydrothermal protocol The incorporation of

Ga and/or Al rendered mesoporous materials that retained the hexagonal array

of pores with a slightly inferior structural order by using X-ray fluorescence

microscopy (TEM) by characterizing

Table 1.2 BET results of Ga-, Al- and AlGa-SBA-15 mesoporous materials

The activity of the Ga- and AlGa-SBA-15 were investigated in the Friedel–Crafts alkylation of toluene with benzyl chloride (promoted by Lewis acidity) and benzyl alcohol (promoted by Brønsted acidity)

The mesoporous acidic materials provided very poor activities in the alkylation of toluene with benzyl alcohol, with the exception of the Al-SBA-

15 The activities of the Ga- and AlGa-SBA-15 were correlated to the higher proportion of Lewis compared with Brønsted acid sites

Table 1.4 Reusability experiments of Ga-20-A in the alkylation

of toluene with benzyl chloride

In other work about Zr-SBA-15, Maria D Gracia and co-workers were proven the high activity of Zr-SBA-15 and Zr-SBA-15 impregnated chloride

in Friedel-Craft alkylation of toluene with benzyl chloride [1]

Table 1.5 Activity of Zr-SBA-15 (conversion ,mol%) in the Friedel-Crafts alkylation of

toluene with benzyl chloride

In this results, Zr-SBA-15 materials needed more than 6 h of reaction to

achieve quantitative conversion at 55%, while Cl-Zr-SBA-15 got 1h to 99%

conversion reaction

Table 1.6 Conversion (mol%) in the Friedel-Crafts alkylation of toluene with benzyl

chloride on Zr-10 and Cl-Zr-SBA-16

1.4 AIM AND OBJECTIVE OF THIS STUDY

Regarding many interesting properties of SBA-16, we expect to study

furthermore on modification of its acidic property, in particular, we are

interested in incorporating Zr into SBA-16 because of theoretically searching a

acidity of the material

A combination of green technologies is therefore needed to improve the

green credentials of the reaction The replacement of the Lewis acids for more

environmentally compatible catalysts can be done through the implementation

of the aforementioned solid acids and heterogeneous catalysis, overcoming problems with catalyst recycling and generation of waste

Thus, this work aims to discuss to examine the characterization such as: highly porousity, evenly pores distribution and highly internal surface areas of Zr-SBA-16 and Cl-Zr-SBA-16 We also want to learn about the effects of impregnating chloride to Zr-SBA-16 in reaction and regeneration The study was scoped in alkylation reaction of toluene and benzyl chloride, using Zr-SBA-6 and Cl-Zr-SBA-16 as catalysts in liquid phase This reaction is catalyzed by Lewis acid, which often requires upwards large amount of catalyst with the attendant difficulties in catalyst separation and product purification, and inert environment is required As inspired by principles of green chemistry, it was decided to study this reaction at mild conditions with Zr-SBA-16 as catalyst

In addition, the study also contributes to the development of applications

of modified SBA-16 as solid acid catalyst for many useful as : alkylation, isomerzation, reforming… This material is studying more in Viet Nam recently, in particular, some studies have been succeeded in using rice husk as silica source or reusing template F127, and brought economic efficiency

In this work, we synthesized Zr-incorporated SBA-16 by direct method then obtain chloride -promoted Zr-SBA-16 by impregnation The presence and effect of zirconium and chloride in the texture and structure of mesoporous silica SBA-16 were studied

CHAPTER 2 – EXPERIMENT

2.1 MATERIALS AND INSTRUMENTATION

All materials were analytical grade and used as receiving without further purification Triblock poly (ethylene oxide) –poly (propylene oxide)-poly

12600 is commercially available from Aldrid, cetyltrimethylammonium

Chemical Reagent, Inc., of Chinnese medicine group

Equipments were used for catalytic synthesist and analyzing reaction conversion, all equipments were calibrated by ISO /EIC 17025:2005 and ASTM standard:

Centrifuges, rate of 1800 round/min

Extract equipments

Flasks

X-ray powder diffraction (XRD) is one of the most powerful technique for qualitative and quantitative analysis of crystalline compounds X-ray diffraction is based on constructive interference of monochromatic X-rays and

a crystalline sample These X-rays are generated by a cathode ray tube, filtered

to produce monochromatic radiation, collimated to concentrate, and directed toward the sample The interaction of the incident rays with the sample produces constructive interference (and a diffracted ray) when conditions

satisfy Bragg's Law (nλ=2d sin θ) This law relates the wave length of

electromagnetic radiation to the diffraction angle and the lattice spacing in a crystalline sample These diffracted X-rays are then detected, processed and counted By scanning the sample through a range of 2θ angles, all possible diffraction directions of the lattice should be attained due to the random orientation of the powdered material Conversion of the diffraction peaks to d-spacings allows identification of the mineral because each mineral has a set of unique d-spacings Typically, this is achieved by comparison of d-spacings with standard reference patterns [14]

Figure 2.1 Architecture of XRD diffractometer