Controlling coke deactivation and cracking selectivity of MFI zeolite by H3PO4 or KOH modification

Article abstract of DOI:10.1016/j.apcata.2015.07.022

The effect of the basic (KOH) or acid (H₃PO₄) treatment of the MFI (HZSM-5) zeolite has been studied comparing the structural and acidic features with the catalytic performance and deactivation of a set of unmodified and modified zeolites (SiO₂/Al₂O₃ = 30-280, 0-3 wt% of K or P). The properties of the catalysts have been elucidated using XRD, ²⁷Al and ²⁹Si NMR, N₂ adsorption-desorption, and adsorption-TPD of tert-butylamine. The catalytic performance has been evaluated in the cracking of 1-butene by means of initial, 5 h on-stream activity and coke formation. Our results point to the fact that using zeolites with high SiO₂/Al₂O₃ ratio or neutralizing the strongest acid sites with KOH or H₃PO₄ increases propylene selectivity while decreases 1-butene conversion. The overall pathway of reaction involves propylene and other olefins as primary products that condensate in further steps to aromatics and ultimately to coke. This pathway can be controlled with less severe acidic features and by desilication with KOH or H₃PO₄ (particularly with the former).

Full text of DOI:10.1016/j.apcata.2015.07.022

Accepted Manuscript
Title: Controlling coke deactivation and cracking selectivity of
MFI zeolite by H PO or KOH modification
3
4
Author: Eva Epelde Jos e´ I. Santos Pierre Florian Andr e´ s T.
Aguayo Ana G. Gayubo Javier Bilbao Pedro Casta n˜ o
PII:
S0926-860X(15)30074-0
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.apcata.2015.07.022
APCATA 15472
To appear in:
Applied Catalysis A: General
Received date:
Revised date:
Accepted date:
4-6-2015
14-7-2015
15-7-2015
Please cite this article as: Eva Epelde, Jos e´ I.Santos, Pierre Florian, Andr e´ s T.Aguayo,
Ana G.Gayubo, Javier Bilbao, Pedro Casta n˜ o, Controlling coke deactivation and
cracking selectivity of MFI zeolite by H3PO4 or KOH modification, Applied Catalysis
A, General http://dx.doi.org/10.1016/j.apcata.2015.07.022
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Controlling coke deactivation and cracking selectivity of MFI
zeolite by H PO or KOH modification
3
4
1
,2
3
4
1
1
Eva Epelde , José I. Santos , Pierre Florian , Andrés T. Aguayo , Ana G. Gayubo ,
1
1
Javier Bilbao , Pedro Castaño *
1
Chemical Engineering Department, University of the Basque Country (UPV/EHU), PO Box 644, 48080.
Bilbao, Spain.* Telephone: +3494601-8435, Email: pedro.castano@ehu.es
2
Department of Innovation and School Administration, Faculty of Psychology and Education, University of
Deusto, PO Box 1, Bilbao 48080, Spain.
3
NMR Service, SGIKER, University of the Basque Country (UPV/EHU), "Joxe Mari Korta" Center, Tolosa
Hiribidea, 72, 20018. San Sebastian, Spain.
4
CNRS, UPR3079 CEMHTI, 1D Avenue de la Recherche Scientifique, 45071 Orléans Cedex 2, France, and
Université d’Orléans, Avenue du Parc Floral, BP 6749, 45067 Orléans Cedex 2, France.
-
1 -

Graphical abstract
Highlights
-
2 -

-
-
Effect of ZSM-5 zeolite treatment with H3PO4 or KOH on its acidity and
structure
Catalytic features linked with 1-butene oligomerization-cracking into
propylene
-
-
Diffusion length of precursors controls catalytic deactivation by coke
Acid strength controls propylene selectivity and 1-butene conversion
Abstract
The effect of the basic (KOH) or acid (H
has been studied comparing the structural and acidic features with the catalytic
performance and deactivation of a set of unmodified and modified zeolites (SiO /Al
30-280, 0-3 wt% of K or P). The properties of the catalysts have been elucidated
3
PO ) treatment of the MFI (HZSM-5) zeolite
4
2
2
O
3
=
2
7
29
using XRD, Al and Si NMR, N adsorption-desorption, and adsorption-TPD of tert-
2
butylamine. The catalytic performance has been evaluated in the cracking of 1-butene
by means of initial, 5 h on-stream activity and coke formation. Our results point to the
fact that using zeolites with high SiO
2
/Al
2
3
O ratio or neutralizing the strongest acid sites
with KOH or H PO increases propylene selectivity while decreases 1-butene
3
4
conversion. The overall pathway of reaction involve propylene and other olefins as
primary products that condensate in further steps to aromatics and ultimately to coke.
This pathway can be controlled with less severe acidic features and by desilication with
KOH or H
3
PO (particularly with the former).
4
Keywords: ZSM-5 zeolite, acidity modification, oligomerization cracking, propylene,
coke deactivation
-
3 -

1
. Introduction
Acidic MFI zeolite (H-ZSM-5 or HZSM-5) is widely used for multiple processes
linked with catalysis, adsorption and separation, in both conventional and sustainable
refining concepts. The outstanding performance of MFI zeolite is attributed to its unique
acid and structural features, which enable shape- and acid-selective reactions to occur.
Furthermore, its porous network, of high connectivity, allows a very high surface-to-
mass ratio and enhances mass transfer by favoring the outward diffusion of deactivating
promoters [1-3]. The catalytic processes using MFI zeolite include (i) fluid catalytic
cracking (FCC), (ii) methanol to hydrocarbons (MTH) or to olefins (MTO), (iii)
bioethanol or bio-oil catalytic transformation, (iv) valorization of polyolefinic plastic
wastes, and (v) interconversion of light olefins (ethylene or butene) into propylene.
Indeed, MFI zeolite has very attractive shape selectivity for producing light olefins, and
propylene in particular. Rahimi and Karimzadeh [4] have reviewed the main
modifications of MFI zeolites for obtaining and intensifying light olefin production,
since the structure and acidity of the MFI zeolite could be tuned for each specific
application by properly selecting the SiO
2
/Al
2
3
O ratio [5-7], calcination with different
protocols [8], using vapor at high temperatures namely steaming [9,10], incorporating
+
rare earth or transition metals [4,11,12], protons by cations like Na [13], selecting a
proper matrix of binders and fillers [14], and by treatment with acids or bases [15,16],
among others.
Modification of MFI zeolite with H
3
PO is a very extended method for modifying
4
IV
framework tetrahedral Al (FAl ) of the zeolite, which is associated to the acid sites,
and micropore blockage [17], with the sequential transformation of framework
IV
IV
tetrahedral (FAl ) sites into (1) distorted tetrahedral (DAl ), (2) framework
V
VI
pentahedral (FAl ), and (3) extra framework octahedral (EFAl ) [18,19]. These
2
9
transformations are observed by solid state Al MAS NMR in 1D or 2D [20]. When the
degree of distortion is low, modifications could be restored by washing with hot water
IV
[
17,21,22]. Besides the removal of FAl , H
3
PO neutralizes Brönsted acidic sites with
4
POH groups, particularly the strongest acid sites [23].
Modification of MFI zeolite with KOH implicates two different distortion
pathways: (1) desilication by the alkali media [15] and (2) neutralization of acid sites by
+
ion exchange with K [24]. Despite the relatively scarce literature on this type of
modifier, we have recently shown that this treatment notably reduces total acidity and
homogenizes acid strength [25]. The treatment with alkali generates mesopores and
-
4 -

hierarchical structures by desilication [26,27], which facilitate the diffusion of the
compounds of the reaction medium and decrease the amount of strong acid sites [28].
Moreover, alkali can also reacts with Al sites [29]. Katikaneni et al. [24] modified MFI
+
zeolite using aqueous solutions of KCO
3
finding that K decreased not only the acid site
strength but also the total acidity of the catalyst. In the case of the catalyst containing 2
wt% of K, there was a complete neutralization of the strong acid sites.
IV
IV
As KOH and H
3
PO react with FAl and FSi , the acidity and crystal size of the
4
zeolite may decrease. In fact, the reduction of crystal size decreases the residence time
of olefins within the interior of the zeolite micropores [30] as well as the proportion of
bimolecular reactions, particularly hydrogen transfer. As a result, the catalytic
deactivation by coke is decreased. In addition, KOH and H
3
PO reacts preferentially
4
with the strongest acid sites, inhibiting the participation of these sites in the
condensation of coke precursors and attenuating deactivation [25,31]. It is also well
established in the literature the increase in hydrothermal stability of MFI zeolite after P
modification [16,32]. Other methods for controlling coke deactivation include
agglomeration with different binders and fillers [33], or incorporating the zeolite in a
composite [14]. These methods target the minimization of coke deposition in the
entrance or within the micropores of the zeolite by adding mesopores that “arrest” coke
outside the zeolite.
The interconversion of light olefins (ethylene or butenes) into propylene is a
suitable process for using K- and P-modified zeolites. Propylene demand is increasing
5
.7 % every year, whereas this product is used for producing polypropylene, propylene
oxide and acrylonytrile, among others [34]. According to the forecasted increase in
ethylene production by steam cracking [35], propylene will be produced only in other
catalytic processes, in which its selectivity is low. Within this scenario, light olefin
interconversion is attractive for adjusting its production to market prices and demands.
The demand for butene stream is lower than that for ethylene and propylene, especially
due to the decrease in the production of methyl tert-buthyl ether (MtBE) as additive for
gasoline. In addition, the transformation of 1-butene into other more interesting light
olefins is an alternative to the oligomerization for the production of middle distillates
[
(
36]. The literature reports the complexity of the 1-butene cracking reaction scheme
including oligomerization-cracking, dehydrogenation-aromatization and hydrogen
transfer reactions) [37,38] and the significant effect of MFI zeolite properties on product
distribution and stability [5,31,39]. Lin et al. [40] proposed several reaction pathways
-
5 -

for the catalytic cracking of 1-butene on MFI zeolites and established an optimum
-1
amount of acid sites (0.181 mmol g ) in order to achieve high propylene selectivity.
Koyama et al. [41] investigated the role of the pore volume of zeolites with 8-, 10- and
1
2-membered rings for the selective production of propylene from other olefins, by
3
determining the optimum zeolite cavity volume (152-223 Å ) for the formation of the
octylcarbenium ion which produces propylene. Furthermore, the local Al distribution in
the MFI framework affects the product composition during olefin cracking [39].
Determining the strength of the correlation between the catalytic features and its
intrinsic performance (activity, conversion, yields, selectivity and deactivation among
others) is a crucial step to rationally design catalysts or evaluate kinetic parameters.
This is done by a sensitivity analysis, which is a preliminary step before the regression
analysis of the data with a model [42]. This protocol has been successfully applied to
evaluate kinetic parameters during the cracking of hydrocarbons [43] and could be
useful for understanding the effect of acidity in the cracking and deactivation
mechanisms [44]. The present work investigates the relationship between the structure,
acidity and performance of the MFI zeolite (SiO
modified with KOH or H PO ) in the transformation of 1-butene. We have synthesized
zeolites, characterized them by XRD, Al and Si NMR, N
2
/Al
2
3
O = 30-280, unmodified and
3
4
2
7
29
9
2
adsorption-desorption,
adsorption-TPD of tert-butylamine, and then agglomerated with bentonite and alumina
to be used in a fixed-bed reactor. A preliminary performance-testing revealed the
suitability of less acidic zeolite (SiO
2
/Al
2
3
O = 280), which strikes a suitable balance
between 1-butene conversion, propylene selectivity and catalyst stability, and hence, we
performed a sensitivity and regression analysis correlating the key futures of the zeolite
that govern selectivity and deactivation.
2
. Experimental
2
.1. Catalyst Preparation
Catalysts were prepared based on commercial MFI zeolites of different SiO
ratio, supplied in ammonium form by Zeolyst International: 30 (CBV 3024E), 80 (CBV
014) and 280 (CBV 28014). The zeolite acid forms (named HZ) were obtained by
2
/Al
2
O
3
8
calcination at 570 ºC for 2 h, whereas the modified ones (1 and 3 wt% of K or P) were
prepared by incipient wetness impregnation at 70 ºC under vacuum in a BÜCHI R-114
rotovapor using known amounts of KOH (85 % purity, Panreac) or H
3
PO
4
(85 % purity,
Merck) solutions, respectively. Modified zeolites are named according to the nominal
-
6 -

content of the modifier (1K, 3K, 1P or 3P) followed by the corresponding SiO
2
/Al
2
O
3
ratio, so the catalysts are: HZ30, 1K30, HZ80, 1K80, HZ280, 1K280, 3K280, 1P280
and 3P280.
The catalysts were obtained by agglomerating each zeolite (25 wt%) with bentonite
(
Exaloid, 30 wt%) as binder and alumina (Martinswek, calcined at 1000 ºC, 45 wt%) as
inert charge. The catalyst particles were obtained by wet extrusion, then sieved to a
particle diameter between 0.3 and 0.15 mm, dried in an oven at 110 ºC for 24 h and
calcined at 570 ºC for 2 h. After agglomeration a matrix with a meso and macroporous
structure embedding the zeolite crystals is generated, so as to [45,46]: (i) provide the
catalyst with a high mechanical resistance for its use in a fixed or fluidized bed reactor;
(
ii) improve accessibility of the reaction medium compounds to the zeolite crystals; (iii)
facilitate the deposition of coke in the meso and macroporous matrix, and; (iv) favor
heat dissipation in the particle during the regeneration step by coke combustion, thus
increasing hydrothermal stability.
2
.2. Catalyst Characterization
The content of K or P was determined by ICP-AES in a Jobin Yvon (ACTIVA)
spectrometer. X-ray diffraction (XRD) patterns at room temperature were obtained in a
PAN alytical Xpert PRO difractometer equipped with CuK radiation of 1.5418 Å. The
α
patterns were recorded using a 2θ step of 0.026° in the 6-60° range. The FULLPROF
program was used to perform the profile refinement of the diffractogram without
structural model (pattern matching routine). This procedure was carried out using the
peak-fit option of the WinPLOTR program without structural model. The simulated
profiles were then used to recalculate the starting unit cell parameters from the 2θ peak
positions. The coherent diffraction crystal size (d ) was determined by using Scherrer
c
equation referred to the deconvolution of the diffraction peaks observed between 7-10º.
An example of the full-profile refinement is shown in Fig. S1 of the Supplementary
Material.
2
9
27
Solid-state Si and Al NMR spectra were recorded on a Bruker 400 AVANCE III
WB spectrometer (9.40 T) under magic angle spinning (MAS) at the resonance
2
9
frequency of 79.49 and 104.27 MHz respectively. Solid-state Si NMR spectra
recorded with a spinning rate 10kHz. Cross-polarization measurements were done using
a 90º pulse for protons of 3.40 μs, 2.0 ms of contact time, and 5 s of recycle delay.
27
Solid-state Al NMR spectra recorded with a spinning rate 10 kHz and a pulse length
of 14 μs with a 1.0 s repetition time. The zeolites were packed into a cylindrical zirconia
-
7 -

2
9
27
rotor (4mm external diameter). The Si and Al chemical shifts are given relative to
2
9
27
tetramethylsilane and Al(NO)
3
respectively. Examples of Si and Al NMR
deconvolution are given in Fig. S2 of the Supplementary Material. It is important to
29
indicate that Si NMR spectra have been obtained using CP-MAS methodology, in
2
9
which protons transfer polarization to Si. Thus, the values of Si NMR spectral
deconvolution cannot be used quantitatively as they depend upon the proximity and
number of protons located nearby Si. For a given catalyst it is to be expected that Q
4
is
being underestimated with respect to Q . However, as all the catalysts have been
3
analyzed in the same experimental setup, the trend of the Q
3
/Q ratio among them is
4
true.
The physical properties were measured by N
2
adsorption-desorption (Micromeritics
ASAP 2010). The experimental procedure for determining physical properties consists
−
3
of degasifying the zeolite at 150 °C and under vacuum (10 mmHg) for 8 h, in order to
remove possible impurities, followed by N adsorption–desorption in multiple
2
equilibrium steps until zeolite saturation at the -196 ºC temperature.
The total acidity and acid strength distribution of the catalysts have been
determined by monitoring the adsorption-desorption of tert-butylamine (t-BA), by
combining the techniques of thermo-gravimetric analysis and differential scanning
calorimetry during the adsorption of the base at 150 ºC. The total acidity is quantified as
-1
the amount of the base chemisorbed at 150 ºC [25,45], in mmolt-BA (gzeolite) , whereas
the acid strength is defined as the heat released during the adsorption of the base, kJ
-1
(
molt-BA) . A very comprehensive review of the characterization of the number of acids
sites and acid strength can be found elsewhere [47].
Catalyst saturation at 150 ºC is followed by temperature programmed desorption
-1
(
TPD) (at 5 ºC min up to 550 ºC) using a Setaram TG–DSC calorimeter connected on-
line with a Thermostar mass spectrometer from Balzers Instruments [45]. The TPD of
amines is based on the formation of alkyl ammonium ions (from adsorbed alkyl amines
protonated by Brönsted sites), which undergo cracking to give ammonia and olefins in a
well-defined temperature range via a reaction similar to the Hofmann-elimination
reaction [48]. Above 150 °C t-BA is cracked on the acid sites releasing butene, whose
signal (m/z = 56) is monitored by mass spectrometer, thereby identifying sites of enough
acidity for cracking. The temperature of maximum desorption-cracking of t-BA (TTBA
)
is linked to the acid strength of the catalyst, as stronger acid sites are active for the
cracking of t-BA at lower temperatures. Considering this, the lower the temperature of
-
8 -

the peak (lower TTBA), the higher the acid strength of the sites, which is the opposite
effect to that observed in the TPD analysis of commonly used NH [6]. Besides, a small
3
fraction of t-BA (signal at m/z = 58) is desorbed without cracking, corresponding to the
base physisorbed on weak acid sites, which are inactive for the cracking of t-BA, and
consequently also for the reactions involved in the transformation of 1-butene [25,45].
Moreover, the interest of using this base is noteworthy since t-BA allows a greater
sensitivity in the thermo-gravimetric measurement of the base (due to its higher
molecular weight) than NH . This sensitivity is required for determining rigorously the
3
differential adsorption heat of the base, especially for catalysts of moderate acid
strength as some of the samples studied in this work.
The coke content deposited on the catalyst was determined by temperature-
programmed oxidation (TPO) in a SDT 2960 thermobalance (TA Instruments). After
stabilization of the zeolite at 250 °C for 30 min in a He stream, the oxidant mixture (25
vol % O in He) was introduced and the combustion took place by following a heating
2
−
1
ramp of 8 ºC min up to 600 ºC, and this temperature was maintained for 1 h to
complete coke combustion.
2
.3. Reaction Equipment and Product Analysis
The runs have been carried out under atmospheric pressure in an automated
reaction device (Microactivity of PID Eng&Tech, Madrid, Spain) equipped with an
isothermal fixed-bed reactor (of 316 stainless steel with an internal diameter of 9 mm
and 10 cm of effective length) and a micro-GC Agilent 3000A for online analysis of the
reaction products, which has been described in detail in a previous work [25]. The
micro-GC, with Soprane software, is provided with 4 analytical modules and the
following columns: a molecular sieve (MS-5A, 10 m) for analysis of CH
PPQ, 8 m), for C -C light olefins; Alumina (10 m), for C -C light paraffins and
olefins, and; OV-1, for C -C10 fraction and aromatics BTX. Product stream is analyzed
4
; Porapak Q
(
2
3
2
5
5
every 4 min. The quantification and identification of the compounds is carried out based
on calibration standards of known concentration. The balance of atoms (C and H) is
higher than 98 wt% in all runs. For this balance we have included the formation of
products that are negligible in terms of overall yields, but important in terms of H
(
hydrogen and methane) and C (coke) atomic proportion.
Experiments have been carried out under the following operating conditions: total
pressure, 1.5 bar (small overpressure to account for the pressure drop in the fixed bed
reactor and the device for continuous sampling); 500 ºC; space time, 1.6 (gcatalyst h)
-
9 -

-
1
-1
(
mol
.35 bar; time on stream, 5 h. Blank runs (without catalyst) were carried out to confirm
that thermal cracking is insignificant below 550 ºC. The reaction indices studied have
been: (i) butene conversion, and, (ii) selectivity of each lump of products (C , C
-C paraffins, C5+ aliphatics and aromatics BTX). It should be mentioned that
C
) ; WHSV, 8.75 h ; 1-butene (99 vol %, Air Liquide) partial pressure in the feed,
1
2
H
4
3
6
H ,
C
2
4
methane, hydrogen and coke selectivities are lower than 1 % under the operating
conditions studied, thus their corresponding lumps of products have been omitted for
further discussion.
Conversion has been defined as follows:
F0  F
X 
(1)
F
where F
0
is the molar flow rate of 1-butene in the feed and F is the flow rate of butenes
(
in thermodynamic equilibrium) in the outlet stream, with both terms being expressed in
C atoms contained.
The selectivity is:
Fi
Si 
100
(2)
F0  F
where F
i
is the molar flow-rate of the i lump in the product stream expressed in C-atom
content.
3
. Results
3
.1. Catalyst properties
The results of the elemental analysis shown in Table 1 ratify that the contents of K
and P are approximately 1 or 3 wt% for the modified zeolites. XRD patterns for the
unmodified and K or P modified zeolites are displayed in Fig. 1. These patterns show
the characteristic peaks of MFI zeolite (Pnma, N° 62). The coherent diffraction crystal
size (d
limitation for zeolites with different crystal shapes [49]. Nevertheless the reported
values of d in Table 1 correspond to unmodified and modified zeolites of the same
parent one (HZ280) so that the shape of the crystal will not vary significantly. Indeed,
some authors have found a correlation of the values of d calculated using the Scherrer
equation and transmission electron microscopy (TEM) [50]. The reported errors of d on
Table 1 have been calculated assuming different shapes of the zeolite crystals.
Attending to the results of d for catalyst with initial SiO /Al = 280, it can be
c
, Table 1) has been calculated using the Scherrer equation, which could have
c
c
c
c
2
2
O
3
-
10 -

deduced that modifying with 1 wt% of K or P decrease the size of the crystals from 140
down to ~70-75 nm, and higher modification with K or P leads to further decrease of
crystal size. Xue et al. [23] have found relatively similar results upon the modification
with H
3
PO of MFI zeolite.
4
2
7
Fig. 2 shows the Al MAS NMR spectra of the modified and unmodified catalysts.
The spectrum of unmodified zeolites HZ30, HZ80 and HZ280 consists of an intense
IV
signal at ca. 55 ppm corresponding to framework tetrahedral Al (FAl ) comprising the
zeolite structure, and another weaker signal at 0 ppm associated to extra-framework
VI
octahedral Al (EFAl ) [17], formed during calcination [51]. HZ30 and 1K30 show a
higher value of the base line at 38 ppm corresponding to framework penta-coordinated
V
FAl sites, typically found in zeolites with high concentration of Al [52]. Nonetheless,
V
these types of FAl sites do not correspond to highly acidic ones, which are normally
IV
VI
associated with FAl and EFAl sites. As previously reported, the modification
VI
procedure with water (in this case present with KOH and H
3
PO ) removes EFAl sites
4
along the zeolite [16,53]. P-modified MFI zeolites show another peak at -11 ppm
VI
corresponding to P-coordinated extra-framework octahedral Al (P-EFAl ) [54]. This
VI
band is very broad, indicating a low symmetry and poor crystallinity of P-EFAl
IV
VI
species [53]. Our results of P-modified zeolites show only Al and Al coordination,
V
which are poles of a transition through Al [18,55].
IV
IV-57
The FAl has been deconvoluted in two tetrahedral sub-bands: FAl
at 57 ± 0.5
IV-54
ppm and FAl
at 54 ± 0.5 ppm. These chemical shift (δAl) corresponds to bond angles
IV-57
IV-54
(
α) of the tetrahedral T-O-T of 150º (FAl
) y 157º (FAl
) according to the
following equation [9]:
Al 132 0.5
(3)
Interestingly, Kučera and Nachtigall [56] have proved that this correlation does no
27
hold for high-siliceous zeolites. Based on these assumptions, the Al MAS NMR
spectra of the catalyst have been deconvoluted in 5 lorentzian peaks with fixed
postitions: -11, 0, 38, 54 and 57 ppm. The results of the deconvolution are summarized
VI
in Table 2. The amount of EFAl sites decrease with the increase of SiO
2
/Al
2
3
O while
V
FAl are only observed for HZ30 and 1K30, as previously explained.
-
11 -

IV-57
Ong et al. [9] demonstrated that FAl
with angles of 150º corresponds to
IV-54
accessible Al sites whereas FAl
with angles of 157º corresponds to internal and
inaccessible Al sites on MFI zeolites. Maier et al. [57] supported this hypothesis on
IV-57
BEA zeolite. On the other hand, Sarv et al. [58] have correlated FAl
with weak
IV-54
Brönsted acids sites and FAl
with stronger ones of the MFI zeolite. Our results
IV-57
IV-54
(
Table 2) show that the ratio of FAl
/FAl
sites decrease severely upon the
treatment with 1K for the zeolites: 71, 56 and 43 % for HZ30, HZ80 and HZ280
IV-57
IV-54
catalysts, respectively. The decrease of the ratio of FAl
/FAl
sites are comparable
VI
using P as compared with K, however, in the former modification an intense P-EFAl is
observed, accounting for the 51 and 81 % for the 1P280 and 3P280 catalysts,
IV-57
respectively. Thus, our results support the assignment of the FAl
as accessible Al
sites, made by the group of Lercher [9,57]: the treatments of K and P preferentially
modify the more accessible Al sites and the extent of this modification increase for
higher amounts of K and P.
2
7
Fig. 2. Al NMR
2
7
Table 2. Al NMR for fresh zeolites
2
9
Fig. 3 shows the Si CP MAS NMR spectra of the catalysts. The spectra of zeolites
show bands at -119.5, -112.9, -108.6, -104.5 ppm, and small shoulders at -97.7 and -
9
3.6 ppm. The band at -119.5 ppm, can be univocally assigned to Q
Si(OSi) ) sites which is present in almost all the zeolites, but particularly intense for
the HZ280 zeolite. The bands at -112.9, -108.6 and -104.5 ppm cannot be univocally
assigned as several coordination states of Si are present. Typically, Q coordination
Si(OSi) (OAl)) sites appear 10 ppm higher than (Si(OSi) ) [53], so that the -112.9 and -
08.6 ppm bands of HZ30, 1K30, HZ80 and 1K80 can be ascribed to this type of
4
coordination
(
4
4
(
3
4
1
coordination [55]. On the other hand, the bands at -112.9, -108.6 and -104.5 ppm
appearing in the P280 and K280 modified zeolites cannot be correlated with Al
incorporation to the Si environment, as Al is being partially eliminated from the
framework (Fig. 2). The bands at -112.9, -108.6 and -104.5 ppm for the P280 and K280
modified zeolites are assigned to Q
3
coordination (Si(OSi) (OH)) or silanol sites [59]
3
interacting with K or P. The K280 modified zeolites have bands with higher chemical
shifts than that of P280 modified ones, whereas the spectra remains approximately the
same between HZ30-1K30 and HZ80-1K80, as previously reported for zeolites with
-
12 -

+
low SiO
7.7 and -93.6 ppm are assigned to Q
Our results point in the same direction than Zhuang et al. [55], who demonstrated
that the treatment with H PO of MFI zeolites produce simultaneous dealumination and
desilication. H PO seems to attack more efficiently Al sites, as proved in Fig. 2,
2
/Al
2
O
3
ratio [55]. This result is due to a higher interaction of K . The bands at -
9
2
coordination (Si(OSi) (OH) ).
2
2
3
4
3
4
whereas KOH seems to attack much more efficiently Si sites. For the calculation of the
bond angle (α) from the chemical shift (δSi), the following expression has been
proposed:
Si  25.44 0.579
(4)
Whereas for highly siliceous HZSM-5 zeolite other empirical correlations have
been proposed [60]:
2
67.9cos()
cos() 1)
Si  11.90 
(5)
(
2
9
The lorentzian deconvolution of the Si CP MAS NMR spectra has been
summarized in Table 3. The treatment with 1 wt% K transforms Q into Q sites for all
the zeolites, however this effect is more dramatic for the HZ280 catalyst.
4
3
2
9
Fig. 3. Si NMR
2
9
Table 3. Si NMR for fresh zeolites
Fig. 4 shows the N
intercept of volume at P/P
catalysts to the micropore volume [61]. Adsorption branches of HZ30, 1K30, HZ80 and
K80 zeolites correspond to type II materials, whereas the desorption hysteresis of the
2
adsorption-desorption isotherms for the zeolites studied and the
0
= 0.2 that is indirectly associated for the same type of
1
same zeolites corresponds to type H3. This behavior is typical of zeolites with micro
and mesopores with slit shaped pores. The modification of the parent zeolite with 1 wt%
of K, affects more significantly to the adsorption at P/P
the catalysts. The 280 family of unmodified and modified catalysts show two
adsorption/hysteresis steps. The former step at P/P < 0.4 indicates the existence of
uniform pores of about 2 nm according to the model of BJH. Groen and Perez-Ramirez
62] have demonstrated that this is a result of a “phase transition of the adsorbed N
0
< 0.2, thus to the micropores of
0
[
2
from a disordered fluid phase to a more ordered crystalline like phase and consequently
do not indicate real mesoporosity”, and this is due to a high homogeneity of the surface.
Independently and interestingly, we observe a decrease of the fluid-to-crystalline
-
13 -

transition (Fig. 4) upon the modification with increasing amounts of KOH or H
This results point to an increase of heterogeneity and imperfections for the modified
zeolites with initial SiO /Al = 280.
3
PO .
4
2
2
O
3
The main physical properties of fresh zeolites are summarized in Table 1. The
modification with P entails a drop in the BET surface area and pore volume, which is
attributed to the blockage of the micropores by phosphorous [54,63]. Singularly, the
same effects observed for the zeolites modified with K, where the decrease in micropore
surface area is due to micropore blockage by K
micropores by the alkali treatment [27]. This effect is more significant for high
SiO /Al ratios and therefore, the latter explanation is more plausible. Indeed, the N
adsorption-desorption isotherms of the 280 catalyst family, upon the treatment of KOH
and H PO , resemble the desilication and creation of mesopores in the silicalite-1 (all
2
O [24] or the desilication affecting
2
2
O
3
2
3
4
silica version of the HZSM-5 zeolite) [64]. The agglomerated final catalyst containing
zeolite, bentonite and alumina provides with a thee level porosity system with micro,
meso and macropores: zeolites contribute to the micropores whereas the matrix
contribute to the meso and macropores [65].
Fig. 4. Isotherms
TPD of tert-butylamine (t-BA) profiles for unmodified and modified zeolites are
plotted in Fig. 5. The acid properties (total acidity and average acid strength) are also
summarized in Table 1. The unmodified HZ30 zeolite shows a main peak at 196 ºC that
corresponds to strong acid sites able to crack t-BA at this low temperature [25,45]. As
the SiO
2
/Al
2
3
O ratio is increased, the temperature required to crack t-BA increases;
HZ80, 200 ºC; and HZ280, 210 ºC. Additionally, these unmodified zeolites show
another broad band at 260-270 ºC corresponding to weak acid sites that require higher
temperature for cracking t-BA [25,66]. 1K30 and 1K80 modified zeolites display a
unique peak at 222-247 ºC corresponding to medium acid sites, whereas 280 modified
zeolites show this peak and a shoulder of weak acid sites at 260 ºC. The amount of acid
sites (Table 1) notably decreases with increasing SiO
2
/Al
zeolite for HZ30 and HZ280, respectively), and by modification with KOH or
, especially by the former. The acid strength measured during the isothermal
adsorption of t-BA is also decreased by the SiO /Al ratio or the modification extent
Table 1). And this trend correlates with the desorption temperature depicted in Fig. 5
and other observations in literature [13,25,67].
14 -
2
O
3
ratio (from 0.67 to 0.15
-1
mmolt-BA
g
H
3
PO
4
2
2
O
3
(
-

Fig. 5. t-BA TPD
3
.2. Catalysts performance
Table 4 shows the kinetic results at zero time on stream for all the catalysts studied.
-butene conversion notably decreases with an increase in the SiO /Al ratio.
1
2
2
O
3
However, an opposite trend is observed in propylene selectivity as zeolites with higher
SiO /Al ratio enhances propylene selectivity from 4.7 % for HZ30 catalyst to 26.6 %
2
2
O
3
for HZ280, as well as ethylene and C5+ fraction selectivity (which is mainly olefinic).
Secondary reactions of aromatization and hydrogen transfer are catalyzed by strong acid
sites and they are suppressed in high silica zeolites to some extent [40]. These reactions
are involved in the formation of aromatics BTX and C
2
-C paraffins [68]. Ethylene
4
selectivity is relatively lower than propylene selectivity, which allows obtaining a
propylene/ethylene ratio of 3.1 in the case of HZ280 catalyst.
Table 4. Kinetic results. TOS = 0 h
The modification with KOH is effective for notably increasing propylene
selectivity, with this effect being more significant on zeolites with high SiO
2
/Al
2
3
O ratio
and high K contents [67], although this is at the expense of a decrease in conversion
which drops down to 55.5 % for 3K280. It should be mentioned that ethylene selectivity
decreases with the K content of the catalyst.
The modification with H
3
PO decreases conversion while enhances propylene
4
selectivity. This observation is similar to that for K, but less dramatic. Propylene
selectivity increases more than 10 % for 3 wt% compared to 1 wt% of P, with a slight
decrease (-3 %) in butene conversion. A more significant effect of P modification is
reported in the literature for MFI zeolites of lower SiO
2
/Al
2
3
O ratio (for values between
2
5-40) [21,63,69]. Dědeček et al. [70] and Sazama et al. [39] have indicated that the
local distribution of Al in the framework has a significant effect on the side reactions.
As FAl sites get closer to each other, bimolecular reactions as hydrogen transfer are
enhanced. This observation indicates that independently of the method employed to
decrease the amount of acid sites, the side reactions are weakened due to the decrease in
the acid site density and their acid strength.
The kinetic results after 5 h on stream are summarized in Table 5. The selectivity of
C
2
-C
ethylene and C5+ fraction (mainly olefinic) selectivity increases in the same period (0-5
15 -
4
paraffins and BTX decreases throughout time on stream, whereas propylene,
-

h). This decrease in C
acidity when increasing TOS. In addition, it is well reported in the literature the role of
-C paraffins and BTX as final products, while olefins (ethylene, propylene and C5+
are intermediates in the reaction scheme of the 1-butene cracking [31,38].
Zeolites with higher SiO /Al ratio keep the activity and selectivity for longer
2
-C
4
paraffin and BTX selectivity is attributed to the drop of
C
2
4
)
2
2
O
3
time on stream, which in another words means that the catalyst is more stable. 1-butene
conversion decreases 11 % for HZ30 catalyst and 6 % for HZ280 catalyst. The observed
trend of catalyst stability is a consequence of the differences in coke deposition. The
coke content determined by TG-TPO is shown in Table 5. Coke deposition is attenuated
when the SiO
2
/Al
2
3
O ratio is increased (3.7 wt% for HZ30 zeolite and only of 1.3 wt%
for HZ280 zeolite) and for the most severely modified zeolites (3K and 3P).
Fig. 6 shows the selectivity of propylene and aromatics (BTX) for the different
catalysts studied at TOS = 0 h (Fig. 6a) and 5 h (Fig. 6b). The latter graph contains also
the coke content of the deactivated catalysts. Interestingly, the evolution of BTX
selectivity increases at higher conversion values of 1-butene and this tendency occurs
for the fresh and deactivated catalyst. This has been observed previously in Tables 4 and
5
, however Fig. 6 reveals that there are unified tendencies among the different catalysts
studied and there is not any significant change in the mechanisms due to the
modification of the HZSM-5 zeolite with KOH or H PO . Coke content in the
3
4
deactivated catalyst (Fig. 6b) follows the same tendency as BTX selectivity. On the
other hand, the evolution of propylene selectivity is reverse to that of BTX so that it
decreases at higher conversion values. These observations indicate that 1-butene
conversion follows a sequential pathway of oligomerization-cracking to form propylene
and ethylene, subsequent aromatization and final condensation of aromatics into coke
(
Fig. 6), as previously demonstrated [38]. In terms of stability, K- and P-modified
zeolites are similar to their corresponding unmodified counterparts, however a lower
deposition by coke is observed (< 2.0 wt%) for the modified zeolites. This effect is
more significant at low SiO
2
/Al
2
3
O ratios. In the case of 3K280 catalysts, a more
significant conversion decay is observed; -31 % compared to -6 % for the HZ280
catalyst, which is attributed to the low amount of acid sites with weak acidity that are
more sensitive to coke deactivation
Table 5. Kinetic results TOS = 5 h
Fig. 6. Selectivity vs. conversion
-
16 -

Fig. 7 shows the TPO profiles corresponding to the combustion of the coke
deposited on the unmodified and modified catalysts after 5 h time on stream. Two types
of coke are identified: (i) coke I, burning off at 500 ºC and; (ii) coke II burning off at
5
70 ºC. In a previous work [66], we have identified the nature of these types of coke by
in-situ FTIR analysis concluding the more aliphatic and disordered nature of coke I and
more condensed and structured aromatic nature of coke II. Besides, coke II has a strong
contribution of coke deposited in the interior of the zeolite crystals and it is formed
firstly, whereas coke I is located more externally in the mesopores of the zeolite or the
matrix [45,66,71]. The amount and the fact that coke I is present demonstrates that
HZ30, HZ80 and HZ280 catalysts are in stage of higher deactivation or coke growth as
compared to the rest of catalysts, that only show coke II. The modification of MFI
zeolite with H
3
PO
4
and KOH decrease the rate of coke formation and growth.
Fig. 7. TPO
The trends of selectivity and deactivation observed here for the unmodified and
modified MFI catalysts (Table 5) have been previously described using zeolites with
lower SiO
2
/Al
2
3
O ratio. Our results point to the outstanding performance of high-silica
MFI zeolite for the cracking of 1-butene pursuing the maximum selectivity of
propylene, so we have decided to focus on this HZ280 zeolite and its modified
counterparts. Historically, the improvement of modified zeolites over unmodified ones
has been rationalized in terms of the neutralization of Brönsted acid sites, particularly
strong ones [46,72]. However, our characterization results show that different features
are interconnected with Brönsted acidity, dealumination and desilication. In view of
these premises, we performed a sensitivity analysis followed by a regression analysis of
the most sensitive features of the MFI zeolite.
3
.3. Correlation between catalytic features and performance
This Section aims correlating the structural, physical and acid properties of the MFI
zeolite with SiO
2
/Al
2
3
O = 280 with their kinetic performance in order to identify the
most controlling features of the catalysts. The 19 catalyst properties (independent or
input variables, I) of this set of 5 catalysts (HZ280, 1K280, 3K280, 1P280 and 3P230)
have already been shown in Tables 1-3, whereas the 19 catalytic performance variables
(
dependent or output variables, O) have been shown in Tables 4-5. A complete list of
the variables is summarized in Tables S1-S2 of the Supplementary Material. We
followed the following method for selecting the most important variables: (1) calculate
-
17 -

the sensitivity factors or elasticity coefficients (Ω) of each pair of i input and j output
73]:
[




O 
Ii
j

k  log10
(6)

O j Ii

where Δ refers to the maximum difference of values. We chose pairs (k) with Ω
k
> 1 as
arbitrary criteria, (2) we excluded variables that do not vary significantly within the
experimental range of this study:
Iimax  I im in
O im ax  Oimin

0.8,
 0.8
(7)
Ii
Oi
max min
where the variables I , I and Ī refer to the maximum, minimum and mean of the
input or output variable. (3) The selected input-output pairs for nonlinear regression
TM
analysis using nlinfit in MATLAB , using potential models. The final selection of the
controlling input-output pair corresponds to the minimal sum of Averaged Sum of
Squared Residuals (ASSR):
n
2






O j exp  Oj

calc
j1
ASSR 
(8)
n
2





O j


exp
j1
Tables in the Supplementary Material summarize the elasticity coefficients (Table
S1) and ASSR (Table S2). These tables show that the most sensitive correlations and
best fittings correspond to the pairs acid strength-conversion, acid strength-selectivity,
c
d -coke and VP/P0=0.2-coke. Indeed, Fig. 8 shows the most sensitive correlations using
linear regression analysis; coke formation is correlated with the crystal size of the
zeolite and the volume of micropores (VP/P0=0.2) of the catalysts. The absolute values of
crystal size and volume of micropores should be taken with care, considering the way
they have been calculated. Nevertheless, the observed correlation still holds and
indicates that the deactivation by coke is strongly influenced by the outward diffusion of
coke precursors formed within the micropores of the catalyst, which easily evacuates
zeolites that has been desilicated. Xu et al. [13] have found that the deactivation of
unmodified and modified MFI zeolite is not a function of acidity in the cracking of 1-
butene, which could be associated to their absence of desilication. Interestingly, we
could not correlate neither by linear nor nonlinear regression models the coke content
with acidity or the loss of activity. However we observed these kinds of correlations
-
18 -

when comparing unmodified zeolites (HZ30, HZ80 and HZ280). This indicates that
acidity plays a significant role in deactivation when considering sets of catalyst with
very different nature and strength of acid sites, whereas desilication seems to control
deactivation within unmodified and modified high-silica zeolites (HZ280).
Fig. 8. Deactivation vs. structure
Fig. 9 shows the correlation of acid strength (measured by temperature of
maximum t-BA desorption-cracking rate, TTBA) with the product selectivity of the
reaction after 0 h (Fig. 9a) and 5 h o stream (Fig. 9b). An increase in the acid strength
favors light paraffin and BTX formation, whereas propylene and C5+ (mainly olefinic)
selectivity notably decreases. Strongest acid sites (TTBA < 210 ºC) enhance both
hydrogen transfer and aromatization reactions, thus enhancing the formation of
aromatics and paraffins. On the contrary, weakest acid sites (TTBA > 225 ºC) promote
oligomerization reaction yielding mainly propylene. These results are in good
agreement with these published recently by Lin et al. [40]. Fig. S3 of the
Supplementary Material provides additional data of the correlation of selectivity of
products and conversion of 1-butene. It should be mentioned that with an industrial
perspective, the fraction C5+ should be recirculate to the cracking unit for boosting the
entire performance of the process.
On view of our results, a suitable balance between the acid strength is required for
balancing conversion and selectivity of propylene. Moreover, deactivation should be
considered as another decisive factor, and coke deposition is minimized for the KOH
treated zeolites that has suffered desilication, reducing the diffusion length of coke
precursors and helping the outward diffusion these species. A good compromise
between all these factors is obtained for the 1K280 catalyst.
Fig. 9. Acidity vs selectivity.
4
. Discussion
The results obtained here allows correlating the acid strength obtained by (a) the
acid strength -heat dissipated during isothermal adsorption of t-BA at 150 ºC- and (b)
the desorption temperature of t-BA (TTBA). Fig. 10 shows that this correlation has a
linear dependency and enable pointing the limits of strong, medium and weak acidity: >
-1
-1
1
30 kJ (molt-BA) or TTBA < 210 ºC, 100-130 kJ (molt-BA) or 210 < TTBA < 225 ºC, and
-1
<
100 kJ (molt-BA) or TTBA > 225 ºC, respectively. This kind of correlation has been
19 -
-

investigated for NH extensively, however is better correlated using t-BA. As shown in
3
Fig. 10, the number of acid sites is not linearly dependent with the acid strength.
Fig. 10. Acidity
Fig. 11 aims to rationalize the results obtained here; we have modified MFI zeolites
of different SiO
modified zeolites in the following manner.
Al environment: K-modified MFI zeolites show significant drop of accessible
2
/Al
2
O
3
ratios (30, 80 and 280) with H
3
PO
4
and KOH, obtaining
IV-57
IV-54
framework Al, as demonstrated by the NMR band ratio (FAl
the extent of this drop is a function of the initial SiO /Al
/FAl
, Table 3), and
2
2
O
3
ratio. This drop of
IV
accessible FAl derives into neutralization of the most acidic Brönsted acid sites of the
zeolites as proved by TPD of t-BA (Fig. 5). P-modified MFI zeolites show a significant
IV
VI
conversion of FAl sites into P-EFAl sites. Despite this significant conversion of
more than 50 %, we do not observe a proportional drop in the acidity or in the
VI
conversion of the modified catalysts. This result indicates that P-EFAl sites participate
in the acidic adsorption of t-BA and in the reactions involved during the conversion of
1
-butene.
Si environment: both K- and P-modified zeolites show significant desilication
which is greater for the MFI zeolites with the higher SiO /Al ratio and for the K-
2
2
O
3
2
9
modified catalysts, as deduced by the chemical shift of the Si NMR bands. This result
indicates that desilication is favored by increasing the amount of the reactants involved:
FSi and alkali media.
Despite the fact that the values of crystal size and micropore volume are not
completely reliable, our results show that coke content is sensitive to the extent of
desilication with KOH, and therefore to the environment of Si. Our results show that the
Al environment is greatly modified with H
3
PO (Table 2), whereas the number of acid
4
sites and the acid strength is greatly modified with KOH. Nevertheless both
modifications change the environments of Si and Al simultaneously. Thus and
according to the results, H
3
PO treatment expands the lifetime of the MFI zeolite
4
catalyst whereas KOH treatment increases propylene selectivity. A good compromise of
low catalyst deactivation and high propylene production is obtained for the 1K280
catalyst.
Fig. 11. Diagram
-
20 -

5
. Conclusions
We have studied the parameters of the MFI zeolite governing selectivity and
deactivation performance during the cracking of 1-butene. Studied zeolites include
different SiO /Al ratios and modification degree with KOH and H PO
2
2
O
3
3
4
.
We have obtained a linear correlation between the acid strengths obtained by the
heat dissipated during isothermal adsorption of tert-butylamine and the temperature-
programmed desorption (TPD) of the same base, using MFI catalyst with different
SiO
2
/Al
2
3
O ratio or modification procedures. This result enables a fast characterization
of this critical catalytic feature; acid strength.
The catalytic performance, in terms of a high propylene selectivity and slow
deactivation by coke, is strongly improved by using high silica zeolites (SiO
2
/Al
2
O
3
ratio = 280) modified with of K or P. Nevertheless, the conversion of 1-butene is
significantly decreased in the same trend. A good balance of low catalyst deactivation
and high propylene production is obtained for the 1K280 catalyst.
Our work supports the general concern that the acidity plays a significant role in 1-
butene cracking when comparing zeolites of different SiO
2
/Al
2
O
3
ratio: Increasing
/Al
conversion and decreasing propylene selectivity for zeolites with lower SiO
2
2
O
3
ratio. On the other hand, the main contribution of this work deals with the clarification
of the controlling features of the high silica MFI zeolites, which are the most promising
catalysts for propylene production. This has been elucidated using a combination of
sensitivity and regression analysis between the catalytic features and their performance.
In this sense and with the unmodified and modified high silica MFI zeolites
(
SiO
2
/Al
2
3
O = 280), acid strength is the key factor controlling conversion of 1-butene
and selectivity of propylene. Besides, the decrease in the diffusion length of the coke
precursors is the key factor controlling coke deactivation and the lifetime of the catalyst,
as it favors the outward diffusion of coke precursors.
Acknowledgements
The financial support of this work was undertaken by the Ministry of Economy and
Competitiveness (MINECO) of the Spanish Government (CTQ2013-46172-P,
CTQ2010-19623 and CTQ2010-19188 projects) and by the University of the Basque
Country (UFI 11/39). E. Epelde (BFI08.122) is grateful for her Ph.D. grant from the
Department of Education, University and Research of the Basque Country and for the
University of the Basque Country. The technical and human support provided by
-
21 -

SGIker (UPV/EHU, MICINN, GV/EJ, ESF) is gratefully acknowledged, particularly to
Aitor Larrañaga.
References
[
1] M. Ibáñez, M. Artetxe, G. Lopez, G. Elordi, J. Bilbao, M. Olazar, P. Castaño, Appl.
Catal. B: Environ. 148–149 (2014) 436-445.
[
[
2] P. Castaño, G. Elordi, M. Olazar, J. Bilbao, ChemCatChem. 4 (2012) 631-635.
3] P. Castaño, G. Elordi, M. Ibañez, M. Olazar, J. Bilbao, Cat. Sci. Technol. 2 (2012)
5
04-508.
[
[
[
(
[
4] N. Rahimi, R. Karimzadeh, Appl. Catal. A: Gen. 398 (2011) 1-17.
5] X. Zhu, S. Liu, Y. Song, L. Xu, Appl. Catal. A: Gen. 288 (2005) 134-142.
6] A.S. Al-Dughaither, H. de Lasa, Ind. Eng. Chem. Res. doi: 10.1021/ie4039532
2014).
7] G. Elordi, M. Olazar, M. Artetxe, P. Castaño, J. Bilbao, Appl. Catal. A: Gen. 415-
4
16 (2012) 89-95.
[
[
8] G.L. Woolery, G.H. Kuehl, Zeolites. 19 (1997) 288-296.
9] L.H. Ong, M. Dömök, R. Olindo, A.C. van Veen, J.A. Lercher, Microporous
Mesoporous Mater. 164 (2012) 9-20.
[
[
10] M. Niwa, S. Sota, N. Katada, Catal. Today. 185 (2012) 17-24.
11] E.F. Sousa-Aguiar, F.E. Trigueiro, F.M.Z. Zotin, Catal. Today. 218-219 (2013)
1
15-122.
12] J. Liu, C. Zhang, Z. Shen, W. Hua, Y. Tang, W. Shen, Y. Yue, H. Xu, Catal.
Commun. 10 (2009) 1506-1509.
13] R.-f. Xu, J.-x. Liu, C.-c. Liang, W.-h. Jia, F.-f. Li, H.-c. Guo, J. Fuel Chem.
Technol. 39 (2011) 449-454.
[
[
[
(
[
(
[
[
(
[
14] Y. Jiao, C. Jiang, Z. Yang, J. Liu, J. Zhang, Microporous Mesoporous Mater. 181
2013) 201-207.
15] Y. Li, D. Liu, S. Liu, W. Wang, S. Xie, X. Zhu, L. Xu, J. Nat. Gas Chem. 17
2008) 69-74.
16] T. Blasco, A. Corma, J. Martínez-Triguero, J. Catal. 237 (2006) 267-277.
17] M. Göhlich, W. Reschetilowski, S. Paasch, Microporous Mesoporous Mater. 142
2011) 178-183.
18] S.M. Cabral de Menezes, Y.L. Lam, K. Damodaran, M. Pruski, Microporous
Mesoporous Mater. 95 (2006) 286-295.
-
22 -

[
19] K. Damodaran, J.W. Wiench, S.M. Cabral de Menezes, Y.L. Lam, J. Trebosc, J.P.
Amoureux, M. Pruski, Microporous Mesoporous Mater. 95 (2006) 296-305.
20] J.A. Van Bokhoven, D.C. Koningsberger, P. Kunkeler, H. Van Bekkum, A.P.M.
Kentgens, J. Am. Chem. Soc. 122 (2000) 12842-12847.
21] D. Liu, W.C. Choi, C.W. Lee, N.Y. Kang, Y.J. Lee, C.-H. Shin, Y.K. Park, Catal.
Today. 164 (2011) 154-157.
22] M. Derewinski, P. Sarv, X. Sun, S. Müller, A.C. Van Veen, J.A. Lercher, J. Phys.
Chem. C. 118 (2014) 6122-6131.
[
[
[
[
[
(
[
(
[
23] N. Xue, R. Olindo, J.A. Lercher, J. Phys. Chem. C. 114 (2010) 15763-15770.
24] S.P.R. Katikaneni, J.D. Adjaye, R.O. Idem, N.N. Bakhshi, Ind. Eng. Chem. Res. 35
1996) 3332-3346.
25] E. Epelde, A.G. Gayubo, M. Olazar, J. Bilbao, A.T. Aguayo, Chem. Eng. J. 251
2014) 80-91.
26] D. Tzoulaki, A. Jentys, J. Pérez-Ramírez, K. Egeblad, J.A. Lercher, Catal. Today.
1
98 (2012) 3-11.
[
[
[
[
27] L. Zhao, J. Gao, C. Xu, B. Shen, Fuel Process. Technol. 92 (2011) 414-420.
28] J. Kim, M. Choi, R. Ryoo, J. Catal. 269 (2010) 219-228.
29] J.S. Jung, J.W. Park, G. Seo, Appl. Catal. A: Gen. 288 (2005) 149-157.
30] H. Konno, T. Okamura, T. Kawahara, Y. Nakasaka, T. Tago, T. Masuda, Chem.
Eng. J. 207-208 (2012) 490-496.
[
(
[
(
[
31] E. Epelde, A. Gayubo, M. Olazar, J. Bilbao, A. Aguayo, Ind. Eng. Chem. Res. 53
2014) 4614-4622.
32] N. Xue, X. Chen, L. Nie, X. Guo, W. Ding, Y. Chen, M. Gu, Z. Xie, J. Catal. 248
2007) 20-28.
33] P. Castaño, J. Ruiz-Martinez, E. Epelde, A.G. Gayubo, B.M. Weckhuysen,
ChemCatChem. 5 (2013) 2827–2831.
[
[
34] J. Plotkin, Catal. Today. 106 (2005) 10-14.
35] E. Mazoyer, K.C. Szeto, N. Merle, S. Norsic, O. Boyron, J.-M. Basset, M. Taoufik,
C.P. Nicholas, J. Catal. 301 (2013) 1-7.
[
(
[
[
36] A. Coelho, G. Caeiro, M.A.N.D.A. Lemos, F. Lemos, F. Ramôa Ribeiro, Fuel. 111
2013) 449-460.
37] J.S. Buchanan, J.G. Santiesteban, W.O. Haag, J. Catal. 158 (1996) 279-287.
38] E. Epelde, A.T. Aguayo, M. Olazar, J. Bilbao, A.G. Gayubo, Ind. Eng. Chem. Res.
5
3 (2014) 10599-10607.
-
23 -

[
39] P. Sazama, J. Dedecek, V. Gábová, B. Wichterlová, G. Spoto, S. Bordiga, J. Catal.
54 (2008) 180-189.
2
[
(
[
40] L. Lin, C. Qiu, Z. Zhuo, D. Zhang, S. Zhao, H. Wu, Y. Liu, M. He, J. Catal. 309
2014) 136-145.
41] T.R. Koyama, Y. Hayashi, H. Horie, S. Kawauchi, A. Matsumoto, Y. Iwase, Y.
Sakamoto, A. Miyaji, K. Motokura, T. Baba, Phys. Chem. Chem. Phys. 12 (2010) 2541-
554.
42] A. Saltelli, M. Ratto, S. Tarantola, F. Campolongo, Chem. Rev. (Washington, DC,
U. S.). 112 (2012) PR1-PR21.
43] N. Agarwal, M.A. Sanchez-Castillo, R.D. Cortright, R.J. Madon, J.A. Dumesic,
Ind. Eng. Chem. Res. 41 (2002) 4016-4027.
2
[
[
[
(
[
44] A. Gutiérrez, J.M. Arandes, P. Castaño, A.T. Aguayo, J. Bilbao, Energy Fuels. 25
2011) 3389-3399.
45] E. Epelde, A.T. Aguayo, M. Olazar, J. Bilbao, A.G. Gayubo, Appl. Catal. A: Gen.
4
79 (2014) 17-25.
46] A.T. Aguayo, A.G. Gayubo, R. Vivanco, M. Olazar, J. Bilbao, Appl. Catal. A:
Gen. 283 (2005) 197-207.
47] L.E. Sandoval-Díaz, J.A. González-Amaya, C.A. Trujillo, Microporous
Mesoporous Mater. 215 (2015) 229-243.
48] G. Caeiro, P. Magnoux, J.M. Lopes, F. Ramôa Ribeiro, S.M.C. Menezes, A.F.
Costa, H.S. Cerqueira, Appl. Catal. A: Gen. 314 (2006) 160-171.
[
[
[
[
(
[
49] A.W. Burton, K. Ong, T. Rea, I.Y. Chan, Microporous Mesoporous Mater. 117
2009) 75-90.
50] P. Morales-Pacheco, J.M. Domínguez, L. Bucio, F. Alvarez, U. Sedran, M. Falco,
Catal. Today. 166 (2011) 25-38.
[
[
51] M. Hunger, Microporous Mesoporous Mater. 82 (2005) 241-255.
52] J. Kanellopoulos, A. Unger, W. Schwieger, D. Freude, J. Catal. 237 (2006) 416-
4
25.
[
[
53] H. Koller, M. Weiß, 2012, pp. 189-228.
54] G. Zhao, J. Teng, Z. Xie, W. Jin, W. Yang, Q. Chen, Y. Tang, J. Catal. 248 (2007)
2
9-37.
55] J. Zhuang, D. Ma, G. Yang, Z. Yan, X. Liu, X. Han, X. Bao, P. Xie, Z. Liu, J.
Catal. 228 (2004) 234-242.
56] J. Kučera, P. Nachtigall, Microporous Mesoporous Mater. 85 (2005) 279-283.
[
[
-
24 -

[
[
57] S.M. Maier, A. Jentys, J.A. Lercher, J. Phys. Chem. C. 115 (2011) 8005-8013.
58] P. Sarv, C. Fernandez, J.P. Amoureux, K. Keskinen, J. Phys. Chem. 100 (1996)
1
9223-19226.
[
[
[
59] J.A. Ke, I. Wang, Mater. Chem. Phys. 68 (2001) 157-165.
60] C.A. Fyfe, Y. Feng, H. Grondey, Microporous Mater. 1 (1993) 401-411.
61] V.L. Barrio, P.L. Arias, J.F. Cambra, M.B. Güemez, B. Pawelec, J.L.G. Fierro,
Appl. Catal. A: Gen. 242 (2003) 17-30.
[
[
62] J.C. Groen, J. Pérez-Ramírez, Appl. Catal. A: Gen. 268 (2004) 121-125.
63] G. Jiang, L. Zhang, Z. Zhao, X. Zhou, A. Duan, C. Xu, J. Gao, Appl. Catal. A:
Gen. 340 (2008) 176-182.
64] M. Ogura, M. Matsukata, in: J. García-Martínez, K. Li, M.E. Davis (Eds.),
Mesoporous Zeolites: Preparation, Characterization and Applications, Wiley-VCH,
015, pp. 259-294.
65] S. Mitchell, N.L. Michels, K. Kunze, J. Pérez-Ramírez, Nature Chem. 4 (2012)
25-831.
66] E. Epelde, M. Ibañez, A.T. Aguayo, A.G. Gayubo, J. Bilbao, P. Castaño,
Microporous Mesoporous Mater. 195 (2014) 284-293.
[
2
[
8
[
[
[
67] X. Zhu, S. Liu, Y. Song, L. Xu, Catal. Lett. 103 (2005) 201-210.
68] P. Castaño, A.G. Gayubo, B. Pawelec, J.L.G. Fierro, J.M. Arandes, Chem. Eng. J.
1
40 (2008) 287-295.
69] G.L. Zhao, J.W. Teng, Z. Xie, W.M. Yang, Q.L. Chen, Y. Tang, Stud. Surf. Sci.
Catal. 170 (2007) 1307-1312.
[
[
70] J. Dědeček, D. Kaucky, B. Wichterlova, Chem. Comm. (2001) 970-971.
[
71] M. Ibañez, B. Valle, J. Bilbao, A.G. Gayubo, P. Castaño, Catal. Today. 195 (2012)
1
06-113.
72] M. Guisnet, L. Costa, F. Ramôa Ribeiro, J. Mol. Catal. A: Chem. 305 (2009) 69-
3.
73] A. Saltelli, M. Ratto, S. Tarantola, F. Campolongo, Chem. Rev. (Washington, DC,
[
8
[
U. S.). 112 (2012) PR1-PR21.
Table 1.
Properties of the fresh zeolites.
-
25 -

b
a
c
K or P
d
c
S
BET
-1
V
P/P0=0.2
-1
acidity
strength
T
TBA
Catalysts
HZ30
2
3
-1
-1
(
wt%)
(nm)
(m g ) (cm g ) (mmol g ) (kJ molt-BA
)
(ºC)
196
222
200
235
210
236
247
222
232
0
0.92
0
0.93
0
0.78
2.75
0.97
3.21
-
-
-
448
434
556
456
512
415
235
322
365
135
130
170
140
144
121
68
0.67
0.59
0.42
0.38
0.15
0.13
0.09
0.15
0.14
150
110
145
85
120
75
57
118
115
1
K30
HZ80
K80
HZ280
1
-
140±13
70±7
35±3
75±7
60±6
1
3
1
3
K280
K280
P280
P280
126
95
a
b
c
Volume of N
2
adsorbed at P/P =0.2.
0
Average crystal particle size according to XRD.
Temperature of maximum t-BA desorption-cracking rate.
Table 2.
2
7
Al NMR peak deconvolution of the fresh zeolites.
V
VI
VI
FAl
(38
ppm)
10.6
14.9
0
IV-54
IV-57
IV-54
P-EFAl
(
EFAl
FAl
FAl
FAl
Catalysts
HZ30
IV-57
-11 ppm)
(0 ppm)
(54 ppm) (57 ppm)
/FAl
0
0
0
0
0
0
0
50.8
81.5
2.3
0
1.8
0
0.8
0
0
52.4
71.2
49.3
69.6
63.4
75.8
88
34.7
13.9
48.9
30.4
35.8
24.2
12
0.663
1
K30
HZ80
K80
HZ280
0.195
0.992
0.437
0.565
0.319
0.136
0.346
0.088
1
0
0
0
0
0
0
1
3
1
3
K280
K280
P280
P280
0
0
36.6
17
12.7
1.5
Table 3.
2
9
Si NMR peak deconvolution of the fresh zeolites.
Q
4
Q
4
or Q or Q
3
Q
4
3
Q
4
or Q
3
Q
3
Q
(-93.6
ppm)
0
3
Catalysts
HZ30
(-119.5
ppm)
26.2
(-112.9
ppm)
27.6
(-108.6
ppm)
32.7
(-104.5
ppm)
12.7
(-97.7
ppm)
0.8
1
K30
40.1
24.6
17.1
13.7
4.4
0
-
26 -

HZ80
K80
HZ280
14.5
12.9
97.1
4.3
12.3
33
0
0
0
7.3
8.2
3.3
0
62.5
76.6
0.3
2.2
8.1
17.2
8.5
0.1
62
55
0.4
5.3
5.8
2
1.3
19.1
12.4
0
0
0
1.1
5.1
4.1
0
1
1
3
1
3
K280
K280
P280
P280
63.3
63.9
28.8
1.2
0.7
Table 4.
Kinetic results at zero time on stream (in wt%).
Catalysts
HZ30
X
S
ethylene
2.5
3.4
6.0
7.2
8.6
7.7
2.3
8.8
8.9
S
propylene
4.7
6.8
S
paraffins
54.8
53.8
43.0
36.1
29.3
16.5
7.3
S
C5+
S
BTX
31.8
25.2
24.5
10.7
10.4
5.6
98.8
96.0
91.6
85.0
82.4
74.5
55.5
80.4
78.1
4.8
1
K30
HZ80
K80
HZ280
10.2
16.4
26.3
24.9
29.5
35
9.5
1
19.4
26.6
40.4
54.7
29.8
32.9
1
3
1
3
K280
K280
P280
P280
0.7
9.6
9.5
24.0
21.8
27.5
26.8
Table 5.
Kinetic results after 5 h on stream (in wt%).
a
Catalysts
HZ30
X
S
ethylene
7.2
S
propylene
17.7
22.1
15.2
32.2
30.9
46.2
53.9
35.7
37.8
S
paraffins
38.5
25.6
37.0
24.7
25.8
11.6
6.0
S
C5+
S
BTX
coke
3.7
2.0
2.5
1.5
1.3
1.1
0.9
1.2
1.0
88.0
87.5
88.8
85.3
77.5
71.1
38.5
78.4
76.7
13.2
22.4
20.7
29.0
25.2
33.4
38.0
28.5
28.8
22.3
17.0
18.3
5.6
9
3.1
0
5.3
4.4
1
K30
HZ-80
K80
HZ280
12.1
8.4
1
8.5
8.9
5.5
1.3
9.3
9.0
1
3
1
3
K280
K280
P280
P280
20.3
19.8
-
27 -

a
Referred to g of catalyst
3P280
1P280
3K280
1K280
HZ280
1
K80
HZ80
1K30
HZ30
60
1
0
20
30
40
50
2 (º)
Fig. 1. XRD patterns of the unmodified and modified MFI zeolites.
-
28 -

-11
56 54
3P280
1P280
3K280
1K280
HZ280
0
0
1K80
HZ80
1K30
0
HZ30
8
0
60
40
0
-20 -40
27Al
(ppm)
2
7
Fig. 2. Al NMR profiles of the unmodified and modified MFI zeolites.
-
29 -