Synthesis of industrially important aromatic and heterocyclic ketones using hierarchical ZSM-5 and Beta zeolites

Accepted Manuscript

Title: Synthesis of industrially important aromatic and

heterocyclic ketones using hierarchical ZSM-5 and Beta

zeolites

Author: Rajkumar Kore Rajendra Srivastava Biswarup Satpati

PII:

S0926-860X(15)00004-6

DOI:

Reference:

http://dx.doi.org/doi:10.1016/j.apcata.2015.01.002

APCATA 15193

To appear in:

Applied Catalysis A: General

Received date:

17-8-2014

Please cite this article as: R. Kore, R. Srivastava, B. Satpati, Synthesis

of industrially important aromatic and heterocyclic ketones using

hierarchical ZSM-5 and Beta zeolites, Applied Catalysis A, General (2015),

http://dx.doi.org/10.1016/j.apcata.2015.01.002

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Graphical Abstract

Hier-ZSM-5(A)

SEM

Hier-ZSM-5(A)

TEM

OCH

3

OCH

3

OCH

3

OCH

3

COCH₃

OCH₃

OCH

3

COCH

3

OCH

3

OCH

COCH

3

H COC

COCH

3

COCH

3

OCH

3

COCH

3

COCH

3

COCH

3

COCH

3

Hier-Beta

SEM

Hier-Beta

TEM

X

1

0 nm

N

H

COCH

3

COCH

3

Where X = N, O, S

OH

OCH

3

CH

3

COPh

OCOPh

COPh

OH

2

µm

20 nm

OCOPh COPh COPh

COPh

1

Page 1 of 40

Research Highlights

Hierarchical ZSM-5 and Beta catalysts were investigated.

Catalysts were investigated in acylation and benzoylation reactions.

Industrially important aromatic/heterocyclic ketones were synthesized.

Hierarchical Beta exhibited the highest activity in these reactions.

Structure activity relationship is explained.

2

Page 2 of 40

Synthesis of industrially important aromatic and heterocyclic ketones using

hierarchical ZSM-5 and Beta zeolites

a

*a

b

Rajkumar Kore, Rajendra Srivastava , and Biswarup Satpati

a

Department of Chemistry, Indian Institute of Technology Ropar, Rupnagar-140001, India

b

Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700 064, India

_________________________________________________________________

Abstract

Hierarchical ZSM-5 and Beta zeolites were investigated in the synthesis of wide range of

industrially important aromatic/heterocyclic ketones by Friedel–Crafts acylation and

benzoylation reactions. For comparative study, conventional ZSM-5 & Beta, and amorphous

mesoporous Al-MCM-41 were investigated. Hierarchical zeolites were prepared by multi-

ammonium structure directing agents whereas conventional zeolites were prepared by mono-

ammonium structure directing agents. Among the catalysts investigated in this study,

hierarchical Beta exhibited the highest reactant conversion in the acylation and benzoylation

reactions. In this study, the systematic assessment of the catalytic activity of acid catalysts for

wide range of aromatic and heterocyclic compounds is shown under one umbrella. To the best of

our knowledge, these reactions over hierarchical zeolites (ZSM-5 and Beta) are reported here for

the first time. Structure activity relationship is explained based on the physico-chemical

properties, molecular size, reactivity of reactants, and reaction mechanism. Catalysts can be

easily recovered and reused with negligible loss in the catalytic activity.

Keywords: Hierarchical zeolites, solid acid catalyst, acylation, benzoylation, aromatic

ketones, heterocyclic ketones.

__________________________________________________________________

^∗Corresponding authors. Tel.: +91-1881-242175; Fax: +91-1881-223395.

E-mail addresses: rajendra@iitrpr.ac.in (R. Srivastava)

3

Page 3 of 40

1. Introduction

Aromatic ketones are synthetic intermediates for the production of fine chemicals,

pharmaceuticals, agrochemicals, fragrances, flavors, dyes etc [1]. In general, aromatic ketones

are synthesized by the Friedel–Crafts acylation reaction using acid catalysts. Friedel–Crafts

acylation is considered to be one of the fundamental reactions in chemistry and applied in the

preparation of several synthetic intermediates of industrial importance. One such interesting

example is the synthesis of the antirheumatic Naproxen, which is produced by the Friedel–Crafts

acylation of 2-methoxynaphthalene into 2-acetyl-6-methoxynaphthalene and subsequent

Willgerodt–Kindler reaction [1-3]. Acid catalyzed Friedel–Crafts acylation based research

articles have been published in wide range of chemistry and chemical engineering journals [4-

1

6]. Initially, conventional homogeneous Lewis acids (AlCl , FeCl , BF , ZnCl , TiCl etc.) and

3 3 3 2 4

Brönsted acids (HF, H SO etc.) were used [7, 8]. These reagents have several disadvantages

2

4

such as use of excess amount (more than the stoichiometric amount) and corrosiveness. This led

to produce a large amount of corrosive waste streams or inorganic salt as a by-product.

Moreover, the catalyst was not recyclable. Further, efforts have been made to prepare substances

(lanthanide trifluoromethanesulfonates alone, micro-encapsulated on polyacrylonitrile and

graphite) that can be used in catalytic amount for this reaction [9-11]. Emphasis was made to

develop solid acid based heterogeneous catalysts due to their easy separation and recyclability,

which makes the process economical and eco-friendly. A wide range of heterogeneous solid acid

catalysts such as zeolites, mesoporous molecular sieves, clays, heteropoly acids, zirconia,

Nafion, metal oxides etc. are known [12, 13]. Among these materials, zeolites have shown

promising activity in the Friedel–Crafts acylation reactions due to their strong acidity [14-17].

Zeolite catalyzed chemical processes solved several obstacles associated with petroleum

refinery industry due to the strong acid strength and shape selectivity. For example, in industrial

practice, zeolites are used in fluid catalytic cracking [18-20]. However, role of the conventional

microporous zeolites is restricted in the reactions requiring large organic molecules due to

diffusion constraints. In petroleum/fine chemical industry, deactivation of the catalyst is a serious

concern [21-26]. In the recent past, efforts have been made to improve the diffusion in the

4

Page 4 of 40

zeolites by inserting mesoporosity or reducing the zeolite thickness to unit cell dimension [27,

8]. Top down and bottom up approaches were made to prepare zeolites with inter/intra-

2

crystalline mesopores [29, 30]. Soft and hard templates both were used to prepare mesoporous

zeolite [31, 32]. When organosilanes were added in the synthesis composition of conventional

zeolites, hierarchical/nanocrystalline zeolites were obtained [27,28,33-35]. Zeolite with structural

feature as small as the size of unit cell (≈10 nm) can be prepared with multi-quaternary

ammonium based soft-templates [36]. Our research group also developed soft template based

synthesis strategies for the preparation of disordered mesoporous zeolites of different framework

structures [37-39]. We recently reported the synthesis of ordered zeolite nanosheets using 1,4-

diazabicyclo[2.2.2]octane (DABCO) based multi-quaternary structure directing agents (SDA)

[40].

An acid catalyst is believed to be a good catalyst if it exhibits good activity in acylation

and benzoylation reactions. Several reports are available in the literature, which deals with the

acylation of aromatic substrates such as anisole and 2-methoxy naphthalene [14, 15, 41].

However, to the best of our knowledge, there is no report in the literature, which covers a wide

range of substrates investigated under identical reaction conditions. In this study, applications of

the hierarchical zeolites (Beta and ZSM-5) were investigated in the acylation and benzoylation

reactions for the synthesis of industrially important aromatic and heterocyclic compounds.

Catalytic activities of hierarchical zeolites were compared with conventional microporous

zeolites (ZSM-5 and Beta) and amorphous mesoporous aluminosilicate (Al-MCM-41). In this

study, catalytic activities of hierarchical zeolites are shown for a wide range of aromatic and

heterocyclic compounds under one umbrella.

2. Experimental Section

2

.1. Material preparation

Three different ZSM-5 materials with Si/Al = 50 were prepared. DABCO based multi-

quaternary SDA (represented as SDA-1, Fig. 2) was used to synthesize nanosheet hierarchical

ZSM-5 (hereafter represented as Hier-ZSM-5 (A)) by following our reported procedure [40].

Another type of hierarchical ZSM-5 (hereafter represented as Hier-ZSM-5 (B)) was prepared

using tetrapropyl ammonium hydroxide (TPAOH) as a SDA but in the presence of

propyltriethoxy silane as an additive by following the reported procedure [28]. Conventional

5

Page 5 of 40

ZSM-5 (hereafter represented as ZSM-5) was prepared by following the reported procedure

using tetrapropyl ammonium bromide (TPABr) [42]. Two different Beta materials, hierarchical

Beta and conventional Beta with Si/Al = 20 were prepared. Hierarchical Beta (hereafter

represented as Hier-Beta) was prepared using piperidine based di-quaternary SDA (represented

as SDA-2, Fig. 2) by following our reported procedure [37]. For comparative catalytic activity,

conventional Beta (represented as Beta) was prepared using tetraethylammonium bromide

(TEABr) [43].

For comparative catalytic investigations, amorphous mesoporous aluminosilicate, Al-

MCM-41 with Si/Al = 50 was prepared by following the reported procedure using

cetyltrimethylammonium bromide as SDA [44].

For catalytic investigations, calcined Na-form of material (2 g) was ion-exchanged

(

thrice) into the NH -form by using 1 M aqueous NH NO solution (100 mL) at 353 K for 4 h.

4 4 3

H-form of material was obtained by the calcination of NH -form of material at 823 K for 6 h.

4

2

.2. Material characterization

X-ray diffraction (XRD) patterns were recorded in the 2θ range of 5–50° (0.5°/min for

ZSM-5 samples and 2°/min for other samples) for wide angle and 0.5–5° for low angle (scan

speed=1°/min) on a PANalytical X’PERT PRO diffractometer using Cu Kα radiation (λ=0.1542

nm, 40 kV, 40 mA) and a proportional counter detector. N -adsorption measurements were

2

performed at 77 K by Quantachrome Instruments Autosorb-IQ volumetric adsorption analyzer.

The specific surface area of zeolites was calculated from the adsorption data points obtained at

P/P between 0.05–0.3 using the Brunauer-Emmett-Teller (BET) equation. The pore diameter

0

was estimated using the Barret–Joyner–Halenda (BJH) method. Scanning electron microscopy

(SEM) measurements were carried out on a JEOL JSM-6610LV to investigate the morphology

of the zeolites. The detailed TEM structural analysis of the developed morphologies were carried

2

out using FEI, Tecnai G F30, S-Twin microscope operating at 300 kV equipped with a GATAN

Orius CCD camera. The sample was dispersed in ethanol using ultrasonic bath, mounted on a

carbon coated Cu grid, dried, and used for TEM measurements. Acidity was examined by

temperature-programmed desorption (TPD) with ammonia. Before TPD experiments, catalyst

was pre-treated in He (50 mL/min) at 873 K for 1 h. After cooling down to 343 K, a mixture of

NH in He (10:90) was passed (75 mL/min) at 343 K for 1 h. Then, the sample was subsequently

3

6

Page 6 of 40

3

flushed by He stream (50 cm /min) at 373 K for 1 h to remove physisorbed ammonia. The TPD

experiments were carried out in the range of 373-973 K at a heating rate of 10 K/min. The

ammonia concentration in the effluent was monitored with a gold-plated, filament thermal

conductivity detector.

2

.3. Procedure for catalytic reactions

2

.3.1. Acylation reaction

In a typical acylation reaction, substrate, acetic anhydride and catalyst (activated at 473

K) were mixed in a 25 mL round bottom flask. Reactions were conducted at a desired

temperature for a stipulated time period. The reaction mixture was analyzed using gas

chromatography (GC) (Yonglin 6100; BP-5; 30 m × 0.25 mm × 0.25 µm). Reactant conversion

and product selectivity were obtained using GC. Products were confirmed using GC–MS

(Schimadzu GCMS-QP 2010 Ultra; Rtx-5 Sil Ms; 30 m × 0.25 mm × 0.25 µm). In most of the

cases, products were also confirmed by the authentic samples obtained from Aldrich (based on

the retention time of the authentic sample in the GC analysis). In the case of indole acylation,

products were also confirmed using NMR.

2

.3.2. Benzoylation reaction

In a typical benzoylation reaction, substrate, benzoylating agent (benzoic acid or benzoyl

chloride) and catalyst (activated at 473 K) were mixed in a 25 mL round bottom flask. Reactions

were conducted at a desired temperature for a stipulated time period in solvent/neat condition.

The reaction mixture was analyzed using GC. Reactant conversion and product selectivity were

obtained using GC. Products were confirmed using GC–MS. In most of the cases, products were

also confirmed by the authentic samples obtained from Aldrich (based on the retention time of

the authentic sample in the GC analysis).

3. Results and discussion

3

.1. Catalyst characterization

Wide angle XRD patterns of Hier-ZSM-5 (A), Hier-ZSM-5 (B), and ZSM-5 show

diffraction patterns corresponding to the MFI framework structure (Fig. 1a). XRD diffraction

7

Page 7 of 40

peaks were broad for Hier-ZSM-5 (A) and Hier-ZSM-5 (B) when compared to ZSM-5, which

confirms that the materials are nanocrystalline in nature [40, 42, 43]. One could clearly observe

the doublet at approx 45º (2) in the ZSM-5 and Hier-ZSM-5 materials. Furthermore, three well

resolved peaks in the range of 22-25º (2) confirmed that hierarchical zeolites are ZSM-5 based

materials. These observations ruled out the possibility of inter-growth of ZSM-5 and ZSM-11

phases [45]. Among the ZSM-5 materials investigated in this study, only Hier-ZSM-5 (A) show

low-angle diffraction pattern (inset of Fig. 1a), which confirms that this material exhibited

ordered structure both in micropore and mesopore length scale. Wide angle XRD patterns of

Hier-Beta and Beta show diffraction peaks corresponding to the Beta framework structure (Fig.

1

b). Hier-Beta exhibited broad diffraction peaks when compared to Beta, which confirms that

Hier-Beta is nanocrystalline in nature.

Oval shape crystal morphology was obtained for Hier-ZSM-5 (A), which was built with

nanosheets like morphology (Fig. 2). Nanosheet architecture was further confirmed by TEM

investigations. HR-TEM image show that each nanosheet was built with several small

nanocrystals grown in one direction to form nanosheet like morphology (Fig. 2). Globular

morphology was obtained for Hier-ZSM-5 (B), which was built with small nanocrystals. HR-

TEM further confirmed that each large globular particle was made up of small nanoparticles of

1

0-20 nm size (Fig. 2). TEM investigations show that 15-20 nm size Hier-Beta was obtained

when it was prepared using di-quaternary ammonium salt (Fig. 2).

Insert Fig. 1, Fig. 2 and Fig. 3

Insert Table 1

Textural properties of the materials were investigated by nitrogen adsorption–desorption

measurements. Hierarchical ZSM-5/Beta exhibited type-IV isotherm similar to the mesoporous

material (Fig. 3a). The major difference in the isotherm of hierarchical ZSM-5/Beta when

compared to ZSM-5/Beta is a distinct increase of N adsorption in the region 0.4<P/Po<0.95,

2

which is interpreted as capillary condensation in the intra-crystalline mesopore void spaces in the

8

Page 8 of 40

hierarchical ZSM-5/Beta materials. The insets of Fig. 3 show a pore size distribution. Textural

properties obtained from the N -adsorption are summarized in Table 1. N -adsorption data

2

clearly show that SDA and additive involve in the synthesis influence the nucleation and growth

process, which resulted in difference in the textural properties. Hier-ZSM-5 (A) prepared with

multi-quaternary ammonium SDA exhibited more surface area and pore volume when compared

to ZSM-5. Hier-ZSM-5 (B) prepared in the presence of propyltriethoxy silane exhibited more

surface area and pore volume when compared to ZSM-5. Similarly, Hier-Beta prepared with di-

quaternary ammonium SDA exhibited more surface area and pore volume compared to Beta

prepared with TEABr. Highly ordered and large surface area Hier-ZSM-5 (A) can be prepared

only with Si/Al = 50 [40], therefore, for uniformity, all ZSM-5 materials and Al-MCM-41 were

prepared with Si/Al = 50. It may be noted that it is difficult to prepare conventional Beta with

Si/Al = 50. Good quality conventional Beta can be prepared with Si/Al = 20, therefore for

uniformity, both Beta samples were prepared with Si/Al = 20. Furthermore, It may be noted that

Hier-Beta prepared with Si/Al = 20 using SDA-2 exhibited almost similar surface area when

compared with Hier-ZSM-5 (A), which is good for the comparative catalytic activity, especially

where the mesopore surface area plays an important role. The order of total acidity of various

catalysts investigated in this study were found to be Beta > Hier-Beta > ZSM-5 > Hier-ZSM-5

(B) > Hier-ZSM-5 (A) > Al-MCM-41 (Table 1). Beta and Hier-Beta (Si/Al = 20) exhibited more

acidity than Hier-ZSM-5 (Si/Al = 50) samples. However, it may be noted that the maximum

desorption temperature of NH from ZSM-5 materials were found to be 683 K, whereas it was

3

6

23 K for zeolite Beta samples (Table 1).

It is easy to imagine ultrathin zeolites, but their actual synthesis is extremely difficult.

This is because zeolite crystallization, like other crystallization processes, is accompanied by

Ostwald ripening. Ostwald ripening is a naturally and spontaneously occurring process that

minimizes the surface free energy of crystals, resulting in dissolution of smaller crystals and

further growth of larger crystals. This thermodynamic controlled phenomenon becomes more

significant as the crystal size decreases and therefore renders the synthesis of ultrathin zeolites

extremely challenging. It is reported that organic molecules that have a strong interaction with

the growing crystal surface can effectively modulate the crystallization process of inorganic

materials [46, 47]. SDA and additive plays very important role in producing zeolite materials

9

Page 9 of 40

with small sized with different morphology. Based on our study, we can conclude that multi-

ammonium groups are required for the formation of the crystalline mesoporous ZSM-5 zeolitic

framework. The ammonium group directly bonded to the C -alkyl tail looks like a hinge joining

1

8

other ammonium groups to promote the zeolite structure-directing function. Here, the multi-

ammonium head acts as a zeolite SDA while the surfactant tails inter-molecularly self-assemble

into the mutilamellar-type mesostructure because of the hydrophobic interaction. With the

surfactant, an ultrathin zeolite framework was formed at the hydrophilic part of the micelles

while the hydrophobic tail restricted the excessive growth of zeolites. Based on the TEM, it can

be concluded that the crystal ripening process is preferred along a-c plane area. The crystal

ripening process along the b-axis is prevented by the hydrophobic alkyl chain. The synthesis of

Hier-Beta using di-cationic SDA indicates that the presence of two ammonium groups in the

same molecule is the most important factor for the generation of nanocrystalline morphologies

and mesoporosity. It is highly possible that the diammonium type SDA is able to generate a large

number of zeolite seeds when compared with their monoammonium analogues TEABr. This was

confirmed from the XRD analysis of the product obtained using SDA-2, which show that a pre-

organized zeolite-like assembly was formed during gelation (0 h, before crystallization). This

process reduced the nucleation time and further crystal growth took place rapidly to form

hierarchical zeolite Beta.

Not only multi-quaternary ammonium SDA but additives involve in the zeolite synthesis

also play important role in reducing the size of zeolite particles. Additive, propyltriethoxy silane

contains three hydrolysable moieties with one hydrophobic propyl group that is unfavourable for

the formation of extended tetrahedral SiO linkages. Therefore, the zeolite growth is retarded at

2

the organic and inorganic interfaces, resulting in the formation of hierarchical zeolites.

Mesopores in Hier-ZSM-5 (B) are formed due to the crystal packing of these nanosized zeolite

particles.

3

.2. Catalytic activity

In this study, a systematic catalytic investigation was made for a broad range of organic

compounds to produce aromatic and heterocyclic ketones of commercial importance. For

systematic study, several –OCH bearing aromatic substrates such as anisole, all three isomers of

3

dimethoxy benzene, and 2-methoxy naphthalene were chosen. Since zeolite Beta is a well known

1

0

Page 10 of 40

heterogeneous catalyst for acylation reaction, therefore Hier-Beta was chosen as a catalyst to

optimize the reaction parameters [14-16, 41, 48-50]. Initially, reaction parameters were

optimized by taking anisole as a reactant, acetic anhydride as an acylating agent in neat

condition. Several reports are available in the literature, which have shown the influence of

solvent on catalytic activity in the acylation reaction [14, 15]. But the objective of the present

study was to provide environmental friendly and economical catalytic solution; therefore

reactions were performed in the neat condition. Acylation of anisole produced 4-methoxy

acetophenone as a selective product (>99%). Only a negligible amount of 2-methoxy

acetophenone (<1%) was obtained as a side product. Influence of reaction parameters such as

temperature, anisole/acetic anhydride ratio, amount of catalyst, and reaction time was

investigated and results are summarized in Fig. 4. Influence of acetic anhydride/anisole ratio

clearly showed that with increase in the acetic anhydride/anisole ratio, anisole conversion was

increased. However, economical consideration lead us to choose acetic anhydride/anisole = 1 for

detailed study. A significant increase in the anisole conversion was obtained when amount of the

catalyst was increased from 25 mg to 50 mg. With further increase in the catalyst amount, no

significant increase in the anisole conversion was observed. Therefore, to achieve high

conversion, 50 mg was chosen as a catalyst amount for further study. As anticipated, with an

increase in the reaction temperature, catalytic activity was increased. To achieve the highest

activity, 393 K was chosen for further study. When the reaction was monitored with reaction

time at 0.5 h, 1 h, 2h, 3h, 4h, and 5h, then anisole conversion was 40, 61, 73, 82, 90, and 91 %,

respectively. This observation is consistent with the literature reports which cite that the reaction

rate was very high in the beginning of the reaction and progressive decrease in the reaction rate

was observed with the increase in the reaction time [16, 48]. Our analysis and literature reports

suggest that this decrease in the activity is due to the deactivation of catalyst by the adsorption of

product molecules, which block the active sites and do not allow the reactant to reach the active

site [16, 48, 49]. To confirm this observation, some control experiments were designed. In the

first control experiment, equimolar amount of anisole and 4-methoxy acetophenone were added

to a reaction mixture containing catalyst and acetic anhydride. Initial reactant conversion

(Anisole conversion at 0.5 h = 23 %) was less than the conversion observed in the reaction with

the only anisole (Anisole conversion at 0.5 h = 40 %). In the second control experiment, first

catalyst and 4-methoxy acetophenone were taken and stirred for 0.5 h. After that, anisole and

1

Page 11 of 40

acetic anhydride were added in the reaction mixture. The initial reactant conversion (Anisole

conversion at 0.5 h = 8 %) was even low when compared to anisole conversion observed in first

control experiment mentioned above. This is due to the fact that during first 0.5 h, when

reactants were not available, most of the catalytic sites were blocked by the adsorption of 4-

methoxy acetophenone. Based on the above mentioned control experiments and literature

reports, it can be concluded that the adsorption of 4-methoxy acetophenone on the active site was

definitely one major reason for progressive decrease in the activity with increase in the time [48].

It may also be noted that acetic acid was formed as a by-product in the reaction. To elucidate

whether acetic acid is playing a role in the deactivation of the catalyst, one more control

experiment was performed. In this control experiment, equimolar amount of anisole and acetic

acid were added to reaction mixture containing catalyst and acetic anhydride. Initial reactant

conversion (Anisole conversion at 0.5 h = 39 %) was almost similar to the conversion obtained

in the reaction with only anisole (Anisole conversion at 0.5 h = 40 %). Based on the above

mentioned controlled experiments, one can conclude that acetic acid is not responsible for the

deactivation of the catalyst, but 4-methoxy acetophenone deactivates the catalyst active sites.

Insert Fig. 4 and Fig. 5

Having understood the cause of catalyst deactivation, it was very important to regenerate

the catalyst by simple method. To explore the method for catalyst regeneration, a set of the

experiments were designed. In the first set of experiments, Hier-Beta and Beta were chosen as

catalyst. First these two catalysts were investigated in several recycling experiments without any

treatment. A progressive decrease in the anisole conversion was observed in the successive runs

over both catalysts as shown in Fig. 5. In the second set of experiments, recovered catalyst was

washed thoroughly with dichloromethane several times, dried at 373 K and then used in the

subsequent cycle. In this case, although the progressive decrease in the anisole conversion was

observed, but this decrease in the activity was much less than the first set of experiments. The

color of the catalyst, which was dark brown before the solvent extraction, was almost restored to

its original white color. This observation confirms that products deposited on the catalyst surface

were removed up to a large extent, which regenerates the catalyst. Investigations show that in

1

2

Page 12 of 40

this case also, even after solvent extraction, a progressive decrease in the anisole conversion was

observed. This observation confirms that during the solvent extraction process, it was not

possible to remove entire adsorbed species from the catalyst. That is the reason for the

progressive decrease in the anisole conversion. In the third set of experiments, the catalyst was

recovered and calcined in air at 773 K for 2 h and then used in the next cycle. Recycling

experiments show that when the catalyst was regenerated by the calcination, then only a

th

negligible decrease in the anisole conversion was observed even after 5 recycles. It is difficult

to rule out the formation of coke species, because some of the acylated products could be

entrapped in the micropores of zeolite materials, which lead to form the coke like species. It is

also reported that acylated product was retained in the zeolite catalyst and the large molecules

formed by the polyacetylation of anisole were responsible for pore blockage and progressive

catalyst deactivation [48]. Through our control experiments, we have shown here that insoluble

form of coke could not be removed during the solvent extraction process using dichloromethane,

therefore catalytic activity was decreased. However, after calcinations, all form of cokes can be

th

removed. Therefore, catalytic activity was retained even after 5 recycles. This observation is

consistent with the literature report [16, 51].

Having optimized the reaction condition for the acylation reaction with anisole, it was

aimed to carry out reactions for several –OCH bearing compounds. A systematic study was

3

performed by choosing all three isomers of dimethoxy benzene and 2-methoxy naphthalene.

Scheme 1 shows the various reactants and their possible acylated products. In principle, the

reactivity for these reactants is different. For 1,2-dimethoxy benzene, para position with respect

to the first –OCH group is activated site, but at the same time this position is the deactivated site

3

for the second –OCH group (meta position is deactivated site for –OCH substituted

3

compounds). Therefore, its reactivity should be less than anisole. For 1,3-dimethoxy benzene,

para position with respect to the first –OCH group is activated site and at the same time this

3

position is further activated by the second –OCH group (because this position is ortho position

3

with respect to second –OCH ). Therefore, its reactivity should be more than anisole. However,

3

it may be noted that ortho substitution is not favored due to steric hindrance. For 1,4-dimethoxy

benzene, para position is not available for further substitution reaction, therefore only ortho

substitute product will be formed. For 1,4-dimethoxy benzene, ortho position with respect to first

–

OCH group is activated site but at the same time this position is the deactivated site for second

3

1

3

Page 13 of 40

–

OCH group (meta position is the deactivated site). Therefore, its reactivity should be the

3

lowest among all dimethoxy benzene isomers. The reactivity of 2-methoxy naphthalene should

be less than anisole because additional phenyl ring substitution deactivates the ring (because

phenyl ring is considered to be electron withdrawing when compared to –OCH ). Therefore,

3

theoretically, the order of activity should be 1,3-dimethoxy benzene> anisole> 1,2-dimethoxy

benzene>1,4-dimethoxy benzene and anisole>2-methoxy naphthalene.

Insert Scheme 1 and Table 3

Having optimized the reaction condition, dimethoxy benzene isomers were acylated

using Hier-Beta (Table 2). The catalytic activity follows the order: 1,3-dimethoxy benzene>1,2-

dimethoxy benzene>1,4-dimethoxy benzene, which is consistent with the theoretical order of

activity discussed above. Further, 2-methoxy naphthalene was acylated using Hier-Beta. During

this reaction, 1-acetyl-2-methoxy naphthalene and 2-acetyl-6-methoxy naphthalene were

obtained. However, more selectivity for 1-acetyl 2-methoxy naphthalene was obtained. This

preferential acylation of 2-methoxy naphthalene at position 1 was observed with various

catalysts, such as AlCl and InCl , less acidic chlorides such as MnCl at higher temperatures,

3

2

zeolites, clays and mesoporous aluminosilicates [50]. The greater reactivity at position 1 can be

related to the lower charge density of carbon 1 (-0.21) compared to carbon 6 (-0.14) and carbon 8

(-0.13) [14]. Influence of various reaction parameters for 2-methoxy naphthalene suggests that

this reaction requires longer reaction time than other –OCH substituted aromatic compounds

3

investigated in this study. However, for better comparison, catalyst amount and reaction

temperature were fixed to be similar.

Wide range of ZSM-5 catalysts, Beta catalysts and Al-MCM-41 were investigated in the

acylation reactions of various –OCH substituted aromatic compounds and results are

3

summarized in Table 2. Before discussing these results, it would be better to know the molecular

size of reactants and products. Hence, theoretical studies were performed and the minimum-

energy geometries of reactants and products were determined by performing DFT geometry

optimizations at the B3LYP/6-31G* (d, p) using the Gaussian 09 program [52]. Molecular size

1

4

Page 14 of 40

of reactants and products are summarized in Table S1. Hier-ZSM-5 materials exhibited

significantly higher activity than ZSM-5. It may be noted that ZSM-5 was found to be negligible

active for these molecules, which confirms that these acylation reactions are not feasible because

catalytic active sites are located inside the micropores of ZSM-5. Furthermore, Hier-Beta was

found to more active than Beta. This difference in the activity can be correlated to high surface

area and inter/intra-crystalline mesopores. In the case of Hier-ZSM-5 and Hier-Beta materials,

the acid sites located at the pore-mouth or little bit farther inside the channels (which may be

called subsurface centers) are the real centers of the reaction. Inter-crystalline mesopores present

in the hierarchical zeolites facilitate the diffusion of reactant to the acid sites and diffusion of the

product from the active sites, which is responsible for the high activity. High reactant conversion

in the case of Hier-ZSM-5 (A) can be correlated to large mesopore volume of Hier-ZSM-5 (A)

when compared to Hier-ZSM-5 (B). High reactant conversion in the case of Hier-Beta can be

correlated to high acidity obtained using TPD. Al-MCM-41 exhibited very low activity because

of its low acidic strength as observed in TPD analysis. If Si/Al is taken into the consideration,

then the activity (average TOF) in the case of Hier-ZSM-5 (A) will be more than Hier-Beta.

However, calculation of TOF is bereft of the physical meaning for two reasons: firstly – it is

difficult to know the concentration of actual acid sites, where the reaction is presumed to take

place, secondly - most of the acid centers are unavailable for more bulky molecules. Thus, the

real TOF is difficult to calculate. Therefore, representing activity with TOF may not be

appropriate. Hence, reactant conversion would be ideally suited for representing the catalytic

activity.

Acylation of heterocyclic compounds

In this study, the acylation reaction of pyrrole, furan, thiophene, and indole were

investigated (Scheme 1). Since the acylation reaction of indole is more complex than other

heterocyclic compounds chosen in this study due to the number of possible products, therefore

reaction parameters were optimized by taking indole as substrate, acetic anhydride as acylating

agent, and Hier-Beta as a catalyst (Table 3). 50 mg catalyst and 393 K were found to be the

optimized catalyst amount and reaction temperature. With an increase in the temperature from

3

13 to 393 K, indole conversion was found to increase from 11 to 96 %. Indole to acetic

anhydride ratio, significantly influence the product selectivity. High indole conversion with good

1

5

Page 15 of 40

3

-acetyl indole selectivity was obtained when the reaction was carried out for 1.5 h using 1.25

equivalent of acetic anhydride with respect to indole. With further increase in the acetic

anhydride to indole ratio, 1, 3-diacetyl indole product selectivity was increased.

Insert Table 3, and Table 4

Acylation of pyrrole, furan, and thiophene required mild reaction condition than the

acylation reaction of indole. An additional phenyl ring in the indole when compared to pyrrole

deactivates the five member ring of pyrrole, therefore indole reactivity was lower than pyrrole

(similar explanation is given above for the difference in the activity of anisole and 2-methoxy

naphthalene). For this reaction to occur efficiently, 333 K was found to be the optimum reaction

temperature and 0.5 h was found to be the optimum reaction time (Table 4). Rest all other

reaction parameters were same as it was obtained for the acylation reaction of indole.

Theoretically, the order of reactivity for these five member heterocyclic compounds should

follow the order of aromaticity. The order of aromaticity is as follows: thiophene>pyrrole>furan.

The catalytic activity obtained using Hier-Beta for thiophene is more when compared to furan

and pyrrole and follows the theoretical catalytic activity order. However, the activity in the case

of pyrrole is less than furan, which is reverse the theoretical order. Since pyrrole is a basic

molecule, therefore, it can inhibit the catalytic active acid sites, therefore less activity was

observed.

Catalytic activity data over wide range of acid catalysts investigated in the acylation

reactions of several heterocyclic compounds are summarized in Table 4. ZSM-5 was found to

exhibit negligible activity in the acylation of indole. When products molecular size and

micropore size of ZSM-5 are taken into account, one can easily conclude that the acylation

reaction of indole would not take place because active sites are located in the micropores of

ZSM-5. Hier-ZSM-5 catalysts exhibited good catalytic activity for the acylation of indole. Since

the mesopore volume of Hier-ZSM-5 (A) is more among the ZSM-5 catalysts, therefore, the

highest conversion was observed for Hier-ZSM-5 (A) than other ZSM-5 catalysts investigated in

this study. The comparative activity also confirmed that Hier-Beta exhibited better activity than

1

6

Page 16 of 40

conventional zeolite Beta. This also can be correlated to large mesopore volume of Hier-Beta

when compared to Beta. Based on TPD and catalytic activity data, one can conclude that zeolites

having more acidity would be better for the acyaltion of indole. This catalytic activity data is

consistent with the acylation of –OCH bearing aromatic compounds. Low activity of Al-MCM-

3

4

1 can be correlated to low acidity and acid strength.

Benzoylation reaction

The scope of the catalyst was extended in the benzoylation reaction of di-hydroxy

benzene isomers (Scheme 2). It is industrially important to develop catalytic process for the

synthesis of 2,4-dihydroxybenzophenone, because of its significant role in the production of 4-O-

octyl-2-hydroxybenzophenone, a UV-light absorbent for polymers [53]. In the conventional

practice, 2,4-dihydroxybenzophenone is synthesized by the reaction between resorcinol and

benzyltrichloride, with coproduction of HCl and of spent metal chlorides [53]. It is important to

develop eco-friendly and economical catalytic process, therefore, benzoic acid was chosen as

benzoylating agent. To optimize the reaction condition for benzoylation reaction, resorcinol and

benzoic acid were chosen as model substrates and Hier-Beta as a catalyst. Influence of reaction

parameters such as reaction time, reaction temperature, amount of catalyst, and solvents were

investigated and results are summarized in Fig. 6. Theoretically, C-benzoylated, O-benzoylated,

and di-O-benzoylated products can be obtained in the benzoylation reaction of resorcinol. When

reaction was performed in neat condition, only O-benzoylated products (especially di-O-

benzoylated product) were obtained. To obtain C-benzoylated product, a few organic solvents

were investigated. Among these, mesitylene was found to be the best solvent, which afforded C-

benzoylated product in good selectivity. Two important observations were made; one by

increasing the amount of catalyst and second by increasing the reaction time. In both the cases,

selectivity for the C-benzoylated product was increased. C-benzoylated product is obtained at the

expense of O-benzoylated product. To understand this observation, it is necessary to understand

the mechanism of this reaction (Scheme 3). Resorcinol reacts with benzoic acid and form mono-

O-benzoylated and di-O-benzoylated products. Later, the acid-catalyzed Fries rearrangement of

mono-O-benzoylated product takes place to form C-bezoylated product. If one observes the

catalytic data at lower temperature, it forms more selectivity for mono-O-benzoylated product.

With further increase in the temperature, selectivity for the mono-O-benzoylated product was

1

7

Page 17 of 40

decreased, whereas selectivity of C-benzoylated product was increased. This was due to the acid

catalyzed rearrangement of mono-O-benzoylated to C-benzoylated product, which requires high

temperature. This is the reason, with increase in the temperature and with increase in the amount

of catalyst, more selectivity for C-benzoylated product was obtained. In contrast to resorcinol,

benzoylation of catechol and hydroquinone lead to form only O-benzoylated products (no C-

benzoylated product was formed). In the case of catechol and hydroquinone, Fries rearrangement

of mono O-benzoylated products was not possible. This is due to the fact that the Fries product

(C-benzoylated product) will form at o, p sites with respect to O-benzoylated product, but these

sites are deactivated sites with respect to free –OH of catechol and hydroquinone, therefore, C-

benzoylated product was not observed in the benzoylation of catechol and hydroquinone

(Scheme 2).

Insert Scheme 2, and Fig. 6

Insert Scheme 3

The catalytic activity data for the benzoylation of dihydroxy benzene isomers using

various catalysts are summarized in Table 5. ZSM-5 was found to be inactive, but Hier-ZSM-5

exhibited good activity. It may further be noted that in this case, high selectivity for the O-

benzoylated product was observed in the benzoylation reaction of resorcinol. In the benzoylation

of resorcinol, zeolite Beta was found to exhibit better activity than Hier-ZSM-5 not only with

respect to resorcinol conversion, but also with respect to the selectivity for the desired C-

benzoylated product. Further increase in the resorcinol conversion and selectivity for the desired

C-benzoylated product were observed in the case of Hier-Beta, which can be correlated to the

large mesopore volume when compared to Beta.

Furthermore, benzoylation of anisole/toluene/naphthalene/anthracene with benzoyl

chloride was carried out over various catalysts investigated in this study (Table 6). The order of

catalytic activity obtained in the bezoylation of anisole/toluene/naphthalene/anthracene was the

same as it was obtained in the case of acylation of –OCH compounds.

3

Insert Table 5 and Table 6

1

8

Page 18 of 40

Having analyzed a wide range of aromatic and heterocyclic compounds in the acylation

reactions with various acylating agents over hierarchical ZSM-5 and Beta samples, one can

conclude that textural properties, especially mesoporoisty of these zeolite materials play

significant role in obtaining high catalytic activity. Therefore, it is quite interesting to draw the

conversion versus the mesopore surface area (S_e_x_t_e_r_n_a_l)/mesopore volume (V_m_e_s_o) for the different

samples. For illustration, conversion (of anisole, 2-methoxy naphthalene, indole, and resorcinol)

versus S_e_x_t_e_r_n_a_l/V_m_e_s_oof ZSM-5 and Beta samples is plotted (Fig. 7). These representations clearly

justify the influence of mesoporosity on the catalytic activity.

Insert Fig. 7

4. Conclusions

Hierarchical zeolites with ZSM-5 and Beta framework structures with inter/intra-

crystalline mesoporosity show excellent activity and selectivity for the synthesis of wide range of

aromatic and heterocyclic ketones. Organic structure directing agents/additive having a strong

interaction with the growing crystal surface effectively modulates the crystallization process of

zeolite materials. DABCO based multi-cationic structure directing agent produced hierarchical

ZSM-5 whereas piperidine based di-cationnic structure directing agent produced hierarchical

Beta materials with high surface area and mesopore volume. Based on the catalytic results, one

can conclude that the accessibility of reactant molecules to the acid sites located at the pore-

mouth or little bit farther inside the channels and enhanced diffusion of reactant/products through

inter-crystalline mesopores are responsible for the high catalytic activity. Furthermore, these

catalysts were easily separated from the reaction mixture, regenerated by simple calcination

process, and recycled with negligible loss in the activity. Structure activity relationship was

established using textural properties of catalytic materials, molecular size & reactivity of

reactants, and reaction mechanism.

1

9

Page 19 of 40

Acknowledgements

Authors are thankful to DST for financial assistance (DST grant: SB/S1/PC-91/2012).

RK is grateful to CSIR, New Delhi for SRF fellowship. We acknowledge Director, IIT Ropar for

constant encouragements. We are grateful to Dr. T. J. Dhilip Kumar, Chemistry Department, IIT

Ropar for providing Gaussian 09 software for DFT calculation. Authors are thankful to the

reviewers for providing deep insight to improve the quality of manuscript.

2

0

Page 20 of 40

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2

3

Page 23 of 40

Scheme, Figure and Table captions

Schemes

Scheme 1. Acylation of various –OCH

containing aromatic compounds and

3

heterocyclic compounds and their acylated products.

Scheme 2. Benzoylation of dihydroxy benzene isomers and other aromatic

compounds and their benzoylated products.

Scheme 3. Mechanism of the benzoylation of resorcinol with benzoic acid, followed

by the Fries rearrangement.

Tables

Table 1.

Table 2.

Table 3.

Table 4.

Table 5.

Table 6.

Physico-chemical properties of various zeolite materials prepared in this

study.

Comparative catalytic activity for the acylation of –OCH

aromatic compounds over different zeolite catalysts.

containing

3

Catalytic activity data for the acylation of indole with acetic anhydride

over Hier-Beta.

Catalytic activity data for the acylation of heterocyclic compounds over

different solid acid catalysts.

Catalytic activity data for the benzoylation reaction of di-hydroxy benzene

isomers over different solid acid catalysts.

Catalytic activity data for the benzoylation reaction of aromatic

compounds with benzoyl chloride over different solid acid catalysts.

Figures

Fig. 1.

Powder XRD patterns of (a) ZSM-5 materials and (b) Beta materials

investigated in this study. Inset of (a) show small-angle XRD pattern of

Hier-ZSM-5 (A).

2

4

Page 24 of 40

Fig. 2.

Fig. 3.

Fig. 4

SEM and TEM micrographs of various Beta and ZSM-5 zeolites

prepared in this study.

N -adsorption/desorption isotherms of (a) ZSM-5 materials and (b) Beta

2

materials investigated in this study. Insets show pore size distribution.

Influence of reaction parameters in the acylation of anisole over Hier-

Beta: (a) Influence of anisole/acetic anhydride ratio [Catalyst = 50 mg,

temp. (393 K), time (4 h), anisole (5 mmol)], (b) influence of catalyst

amount [Temp. (393 K), time (5 min), anisole (5 mmol), acetic

anhydride (5 mmol)], (c) influence of time [Catalyst = 50 mg, temp. (393

K), anisole (5 mmol), acetic anhydride (5 mmol)] (d) influence of

temperature [Catalyst = 50 mg, time (4 h), anisole (5 mmol), acetic

anhydride (5 mmol)].

Fig. 5.

Fig. 6

Catalytic activity data obtained in the recycling study of anisole

acylation using Hier-Beta and Beta.

Influence of reaction parameters in the benzoylation of resorcinol (1

mmol) with benzoic acid (1 mmol) over Hier-Beta. (a) Influence of

reaction time, (b) catalyst amount, (c) solvent (2 ml), and (d) reaction

temperature.

Fig. 7

Conversion versus Sexternal / Vmeso of ZSM-5 samples (I, II) and Beta

samples (III, IV). S_e_x_t_e_r_n_a_lof ZSM-5, Hier-ZSM-5 (B), Hier-ZSM-5 (A),

2

Beta, and Hier-Beta are 71, 255, 296, 105, and 290 m /g, respectively.

V_m_e_s_oof ZSM-5, Hier-ZSM-5 (B), Hier-ZSM-5 (A), Beta, and Hier-Beta

are 0.08, 0.45, 1.28, 0.21, and 0.48 mL/g, respectively.

2

5

Page 25 of 40

Table 1

a

b

c

Material

Si/M

Time

(

S

BET

2

S

Pore Volume

(mL/g)_d

Temp. at

1 peak

Weak

acidity

(mmol/g)

Temp. at

2 peak

Stro

acidi

(mmo

micro

2

external

2

st

e

nd

days) (m /g) (m /g)

(m /g)

In Out

put put

V_m_i_c_r_o

V_m_e_s_o

maxima

e

(K)

2

0

17.5

16

2

495

685

687

390

395

105

290

292

0.18

0.17

0.21

0.48

≈ 473

0.44

0.28

≈ 623

0.3

0.2

-Beta

20 19.4

20 19.1

-Beta

2

cycled catalyst)

M-5

50 52.4

50 52.8

50 54.2

50 54.1

3

328

535

670

667

257

280

374

371

71

0.13

0.12

0.10

0.08

0.45

1.28

≈ 473

0.22

0.21

0.19

≈ 683

0.1

-

ZSM-5 (B)

ZSM-5 (A)

255

296

297

-

cycled catalyst)

MCM-41

50 55.2

3

970

-

970

Only one broad peak (at ≈ 500 K), Acidity = 0

mmol/g

a

b

Obtained by ICP analysis. S_B_E_Tcalculated from the adsorption data obtained in the region of

.05<P/P ≤0.3 using Brunauer-Emmett-Teller (BET) method. Micropore, external surface area,

c

0

and micropore volume was calculated by t-plot method (S

= S_m_e_s_o_p_o_r_e+ S_m_a_c_r_o_p_o_r_e(if any).

external

d

V_m_e_s_o= Total pore volume – V_m_i_c_r_o, where total pore volumes was calculated at P/P = 0.98.

0

e

Obtained by NH TPD analysis.

3

Table 2

Acylation of

Catalyst

a

Anisole

1,2-Dimethoxy 1,3-Dimethoxy 1,4-Dimethoxy

2-methoxy _b

naphthalene

Conv. (%) Sel. (%)

a

benzene

Yield (%)

benzene

Yield (%)

benzene

Yield (%)

c

d

e

f

g

Conv. (%) Sel. (%)

Hier-Beta

90

59

2

99

68

94

42

55

30

1

78

76

69

Beta

34

2

60

19

-

ZSM-5

2.5

2

6

Page 26 of 40

Hier-ZSM-5 (B)

Hier-ZSM-5 (A)

Al-MCM-41

28

48

10

86

45

99

98

99

98

47

63

7

50

80

12

-

11

22

5

12

22

8

89

83

79

77

84

h

Hier-Beta

-

50

20

h

Hier-ZSM-5 (A)

-

a

Reaction condition: Acylation of anisole/dimethoxybenzene: Anisole/ dimethoxybenzene (5 mmol), acetic

b

anhydride (5 mmol), Catalyst (50 mg), reaction temperature 393 K, and time (4 h). Acylation of 2-methoxy

naphthalene: 2-methoxy naphthalene (2.5 mmol), acetic anhydride (2.5 mmol), Catalyst (50 mg), reaction

temperature 393 K, and time (12 h).

c

d

e

p-methoxy acetophenone and remaining is o- methoxy acetophenone. 3,4-dimethoxy acetophenone only. 2,4-

f

g

dimethoxy acetophenone only. 2,5-dimethoxy acetophenone only. 1-acetyl 2-methoxynaphthalene product and

h

th

remaining is 2-acetyl 6-methoxynaphthalene. Catalytic activity data after 5 recycle (recovered catalyst was

calcined prior to their reuse in the each step).

Table 3

COCH₃

COCH

3

Acetic

anhydride

Catalyst

N

H

COCH₃

COCH

3-Ac Indole

1-Ac Indole

1,3-diAc Indole

E. Catalyst Temp.

Indole :

Acetic

anhydride

Time Indole

Product Selectivity (%)

N. amount

(K)

(h)

Conv.

(%)

3

-Ac

1-Ac

1,3-diAc

Indole

(mg)

Indole Indole

(

mmol)

10 : 2

4 : 2

1

2

3

4

5

6

7

8

9

50

393

1.5

10

1.5

10

9

46

82

96

100

98

100

90

87

85

84

77

76

74

72

70

69

60

65

10

12

11

10

9

0

1

3

4

11

12

15

18

20

22

31

28

2 : 2

2 : 2.5

2 : 3

2 : 4

2 : 6

2 : 8

1

0

1

2

2 : 10

2 : 20

1

9

7

1.5

2

7

Page 27 of 40

1

3

4

5

6

50

393

373

353

313

2 : 20

2 : 2.5

20

1.5

100

80

61

38

86

88

80

7

55

3

1

11

20

11

0

Table 4

a

b

Indole

Pyrrole

Furan

Thiophene

Acylation of Conv 3-Ac Conv

2-Ac

pyrrole

Sel. (%)

Conv 2-Ac Conv

(%) furan (%)

2-Ac

thiophene

Sel.

(%)

Indole (%)

Sel.

(%)

Catalyst

(%)

Hier-Beta

96

59

4

84

83

32

81

80

79

80

64

41

13

50

66

13

-

78

77

76

78

77

-

79

51

-

92

91

-

93

60

30

71

94

28

-

99

Beta

99

-

ZSM-5

Hier-ZSM-5 (B)

Hier-ZSM-5 (A)

Al-MCM-41

80

95

20

92

60

80

22

-

90

91

-

c

Hier-ZSM-5 (A)

a

Reaction condition: Acylation of indole: Indole (2 mmol), acetic anhydride (2.5 mmol), catalyst (50 mg),

b

temperature (393 K), time (1.5 h). Acylation of pyrrole/thiophene/furan: pyrrole/thiophene/furan (2 mmol),

acetic anhydride (2.5 mmol), catalyst (50 mg), reaction temperature (333 K), time (0.5 h).

c

th

Catalytic activity data after 5 recycle (recovered catalyst was calcined prior to their reuse in the each step).

2

8

Page 28 of 40

Table 5

Acylation of

Resorcinol

Catechol

O-

Hydroquinone

Conv

C-

O-

Conv

O,O-di- Conv

O-

O,O-

(

%) Benzoyl Benzoyl

(%) Benzoyl Benzoyl

Sel. (%) Sel. (%)

(%) Benzoyl Benzoyl

Sel. (%) Sel. (%)

Catalyst

Sel. (%) Sel. (%)

Hier-Beta

74

69

57

19

20

23

21

68

29

41

81

80

77

78

30

95

71

-

90

91

-

10

9

-

97

76

-

80

82

-

20

18

-

Beta

53

1.5

30

42

9

ZSM-5

Hier-ZSM-5 (B)

Hier-ZSM-5 (A)

Al-MCM-41

18

28

8

95

94

92

-

5

6

8

-

20

31

9

93

91

85

-

7

9

15

-

a

Hier-Beta

71

-

Reaction condition: substrate (1 mmol), benzoic acid (1 mmol), mesytylene (2 mL), catalyst (100 mg), temperature

33 K, time (30 h).

4

a

th

Catalytic activity data after 5 recycle (recovered catalyst was calcined prior to their reuse in the each step).

Table 6

a

b

c

d

Acylation of

Catalyst

Anisole

Conv. p-

%)

Toluene

Conv.

Naphthalene

Anthracene

p-

Conv.

(%)

2-

Conv.

(%)

9-

(

Benzoyl (%)

Sel. (%)

Benzoyl

Sel. (%)

>99

Benzoyl

Sel. (%)

98

Benzoyl

Sel. (%)

>99

Hier-Beta

Beta

55

25

8

>99

45

28

6

41

23

3

54

25

1

>99

98

97

98

>99

ZSM-5

Hier-ZSM-5 (B)

17

15

14

32

2

9

Page 29 of 40

Article Doi

Synthesis of industrially important aromatic and heterocyclic ketones using hierarchical ZSM-5 and Beta zeolites

DOI: 10.1016/j.apcata.2015.01.002

Source and publish data:

Authors:

Article abstract of DOI:10.1016/j.apcata.2015.01.002

Full text of DOI:10.1016/j.apcata.2015.01.002

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