Methanol to olefins conversion over silicoaluminophosphates with AEI structure: Effect of the active site type

Article abstract of DOI:10.1134/S0965544116030051

Effect of the type of active site on the catalytic properties of microporous crystalline silicoaluminophosphates with AEI structure synthesized at 150, 170, and 190°C has been investigated. The state of the active site was changed by varying the catalyst synthesis conditions. It has been established that during the synthesis of silicoaluminophosphates with the AEI structure from the reaction mixture of the same composition, an increase in the temperature and crystallization time leads to an increase of the silicon content and crystal size growth. The observed changes in the physicochemical properties are accompanied by the change of the silicon state in the structure of silicoaluminophosphates with the predominant formation of silicon “islands” via the SM3 mechanism. According to ²⁹Si NMR data, the formation of active sites of silicoaluminophosphates via the SM2 mechanism in the form of isolated silicon atoms in the structure is also observed for these materials. The presence of such sites, along with the morphological features of the crystals, determines the unusual catalytic properties of silicoaluminophosphate with AEI structure in MTO process, which are a high ethylene yield up to 41 wt % at an ethylene: propylene molar ratio of 1: 6.

Full text of DOI:10.1134/S0965544116030051

ISSN 0965ꢀ5441, Petroleum Chemistry, 2016, Vol. 56, No. 3, pp. 217–223. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © V.I. Kasnerik, S.V. Konnov, I.V. Dobryakova, A.O. Ivanov, E.E. Knyazeva, I.I. Ivanova, 2016, published in Neftekhimiya, 2016, Vol. 56, No. 3, pp. 234–240.
Methanol to Olefins Conversion over Silicoaluminophosphates
with AEI Structure: Effect of the Active Site Type
a
b
a
b
a, b
a, b
V. I. Kasnerik , S. V. Konnov , I. V. Dobryakova , A. O. Ivanov , E. E. Knyazeva , and I. I. Ivanova
a
Faculty of Chemistry, Moscow State University, Moscow, Russia
b
Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow, Russia
eꢀmail: eknyazeva62@mail.ru
Received November 16, 2015
Abstract—Effect of the type of active site on the catalytic properties of microporous crystalline silicoalumiꢀ
nophosphates with AEI structure synthesized at 150, 170, and 190°C has been investigated. The state of the
active site was changed by varying the catalyst synthesis conditions. It has been established that during the
synthesis of silicoaluminophosphates with the AEI structure from the reaction mixture of the same composiꢀ
tion, an increase in the temperature and crystallization time leads to an increase of the silicon content and
crystal size growth. The observed changes in the physicochemical properties are accompanied by the change
of the silicon state in the structure of silicoaluminophosphates with the predominant formation of silicon
29
“
islands” via the SM3 mechanism. According to Si NMR data, the formation of active sites of silicoalumiꢀ
nophosphates via the SM2 mechanism in the form of isolated silicon atoms in the structure is also observed
for these materials. The presence of such sites, along with the morphological features of the crystals, deterꢀ
mines the unusual catalytic properties of silicoaluminophosphate with AEI structure in MTO process, which
are a high ethylene yield up to 41 wt % at an ethylene : propylene molar ratio of 1 : 6.
Keywords: silicoaluminophosphates, morphological features, acid properties, type of active site, conversion
of methanol into olefins
DOI: 10.1134/S0965544116030051
Like crystalline silicoaluminophosphate with the structure of silicoaluminophosphates, which deterꢀ
CHA structure (SAPOꢀ34), silicoaluminophosphate mines the acidic properties of these materials. Known
with the AEI structure (SAPOꢀ18) is a well known catꢀ mechanisms of isomorphous substitution in the strucꢀ
alyst for the production of lower olefins from methanol ture of silicoaluminophosphates, which are discussed
(
MTO process) [1]. This material was prepared for the in detail in [7], show that there are only two likely variꢀ
first time in 1993 [2] and characterized later [3]. The ants of incorporation of silicon into the structure
similarity of the catalytic properties of SAPOꢀ34 and for these materials due to the impossibility of the forꢀ
SAPOꢀ18 is determined by the features of the crystal mation of the Si–O–P bond (Fig. 1). The
structure of these materials, which are microporous first variant (SM2 mechanism) involves the incorpoꢀ
molecular sieves with a window size of 0.38 nm. The ration of silicon in the form of isolated tetrahedra by
+5
+4
+
structure of silicoaluminophosphates is formed by the
alternating layers of hexagonal prisms. The differences mation of a bridging OH group and generation of
in their structure are associated with translation symꢀ an acid
site. According to the second
P
→
Si + H substitution resulting in the forꢀ
metry (parallel layer packing) in SAPOꢀ34 and transꢀ variant, silicon forms the soꢀcalled silicon islands in
lation–reflection symmetry in SAPOꢀ18 (layers are the silicoaluminophosphate structure via the substituꢀ
+
5
+3
+4
arranged in reflection symmetry to each other) [3]. As tion P + Al
a result of these differences, the CHA unit cell has a sites being formed only at the islet boundaries and,
prismatic shape with dimensions of 0.94 1.27 nm and hence, the concentration of these sites being noticeꢀ
the AEI unit cell has a pearꢀlike shape with a size of ably lower. According to the existing concepts, both of
→
2Si (SM3 mechanism), with acid
×
1.16
×
1.27 nm [4].
the mechanisms exist for the CHA and AEI structures,
but the SM3 mechanism is considered to be predomiꢀ
nant for AEI.
Chen et al. [5] found that the differences in the acid
properties of CHA and AEI are due to the absence of
1
strong acid sites in AEI. According to H NMR data
The aboveꢀspecified features of the structure, active
[
6], the concentration of bridging hydroxyl groups in site types and acid properties of silicoaluminophosꢀ
AEI is threefold lower than that in CHA. These differꢀ phates determine the differences in their catalytic
ences are attributed to the state of silicon atoms in the properties in MTO reaction. According to Marcus
217

218
KASNERIK et al.
Al
O
Al
[
SM1]
P
P
[SM3]
O
O
P O
O
O
Al
Al
O
O
P
[
SM2]
Al3+
Si4+
P5+
Si4+ + H+
P5+ + Al3+
Al
2Si4+
Al
O
Al
O
O
H
Al
Al
Al
P
P
+
P
P
P
O P O
O
O
Si
O
O Si O
Si
O
O
O
O
O
Si
Al
O
Al
Al
Al
O
O
O
O
O
O
P
O
O
P
P
P
Fig. 1. Types of isomorphous substitution in the silicoaluminophosphates structure.
et al. [8], the pearlike shape of the AEI unit cell and samples synthesized from the reaction mixture of the
possible forms of orientation of coke deposits in it same composition was achieved by varying the catalyst
contributes to stable catalytic activity of this silicoaluꢀ synthesis conditions, such as crystallization temperaꢀ
minophosphate, whereas CHA fast deactivated. The ture (150, 170, and 190
low acidity of AEI leads to the predominant formation ment time (6–72 h).
of propylene: according to published data [9], the ethꢀ
°С) and hydrothermal treatꢀ
ylene : propylene ratio in the reaction products does
EXPERIMENTAL
not exceed 0.54. This fact has caused that the interest
of researchers in the AEI structure silicoaluminophosꢀ
phate has decreased.
Silicoaluminophosphates with the AEI structure
were synthesized by hydrothermal crystallization
It is to be noted that unlike SAPOꢀ34, SAPOꢀ18 is from a reaction mixture with the composition
characterized by a minimal number of synthesis variaꢀ Al 2P 0.6SiO 4(C NOH 140H . The
O
⋅
O
⋅
⋅
H
)
⋅
O
2
2
3
2
5
2
2
5
4
tions. It is prepared according to two main procedures reactants were aluminum isopropoxide, aqueous silica
using N,Nꢀdiisopropylethylamine [3] and tetraethyꢀ sol (40 wt %), orthophosphoric acid (85 wt %), and
lammonium hydroxide [10] as a structureꢀdirecting aqueous tetraethylammonium hydroxide solution (35
agent (template). The procedure involving N,Nꢀdiisoꢀ wt %). After mixing the initial components, the reacꢀ
propylethylamine does not provide high selectivity of tion mixture was homogenized for 1 h, brought to pH
crystallization, and the crystallization products conꢀ 7 by adding concentrated HCl, and homogenized for 1
tain an admixture of SAPOꢀ5 [3]. In the presence of h again. The crystallization times were 24 and 72 h at
tetraethylammonium hydroxide, phaseꢀpure SAPOꢀ 150
8 crystallizes with a high yield in the form of flat ellipꢀ After completion of crystallization, the solid products
soid crystals. However, the procedure suggests hard were separated from the liquid phase by centrifugaꢀ
hydrothermal treatment of the reaction mixture at tion, washed, dried at 100 for 12 h, and calcined at
15
for 5 days, whereas SAPOꢀ34 crystallizes at a 500 for 2 h in an air flow (heating rate, 2°C/min).
°C, 12 and 18 h at 170°C, and 6 and 12 h at 190°C.
1
°C
2
°
С
°C
lower temperature during shorter period of time. To Six catalyst samples denoted as
date, neither the synthesis of SAPOꢀ18 under milder synthesis temperature (°C) and
conditions nor the properties of materials of this type synthesis (h).
T
N
ꢀ
N
, where
T is the
is the duration of
have been studied.
In this work, we comprehensively studied the physꢀ performed using diffraction patterns obtained on a
icochemical and catalytic properties of silicoaluminoꢀ Bruker D2PHASER Xꢀray diffractometer (Сu
phosphates with the AEI structure and different states radiation). The diffraction patterns were recorded
The phase analysis of silicoaluminophosphates was
K
α
о
of active sites. The change of an activeꢀsite state in the within the angular range of 5–40 2 with a step size of
θ
PETROLEUM CHEMISTRY Vol. 56
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2016

METHANOL TO OLEFINS CONVERSION
219
(
b)
(а)
1 μm
5
10
15
20
2θ, deg
25
30
35
Fig. 2. (a) Xꢀray diffraction pattern of sample 170ꢀ18 and (b) SEM image of sample 190ꢀ12.
–
1
0
.05°, a slit width of 1 mm, and a count time per step atmospheric pressure, a feedstock WHSV of 2 h , and
of 3 s.
a molar ratio of N2 : methanol = 5 : 1. Chromatoꢀ
Thermogravimetric (TGA) and differential therꢀ graphic analysis of the products was conducted on a
mal (DTA) analyses were performed on an SDT Q600 Chromatec Analytic Kristall 5000 chromatographs
instrument (TA Instruments). The TG–DTA curves equipped with flame ionization (FID) and thermal
were recorded in the linear temperature programming conductivity (TCD) detectors and a PoraBond Q and
mode at a heating rate of 10°C/min in the temperature Porapak Q column.
range of 20–800°C in an air flow (100 mL/min).
The characteristics of the porous structure of siliꢀ
coaluminophosphates were determined using the lowꢀ
temperature nitrogen adsorption–desorption method.
The isotherms were recorded according to the stanꢀ
dard procedure on a Micromeritics ASAP 2010 poroꢀ
simeter.
RESULTS AND DISCUSSION
The synthesized samples of silicoaluminophosꢀ
phates were characterized using a set of instrumental
methods. By XRD data, it was established that the
synthesis conditions chosen ensure the preparation of
Electron microscope images of the samples were highly crystalline samples as a phaseꢀpure material
obtained on a CAMSCAN electron microscope. with the AEI structure. The set of lines in the diffracꢀ
Before examination, the surface of the samples was tion patterns of the samples (e.g., see Fig. 2a) correꢀ
decorated with a gold–iridium alloy applied by vacꢀ sponds to published data. The crystallinity of the samꢀ
uum sputter deposition.
ples was high (90–100%). The yield of the crystalline
The acid properties of the samples were studied phase determined by the ratio of the weight of the
using temperatureꢀprogrammed desorption of ammoꢀ resulting sample to the total weight of the frameworkꢀ
nia (TPD NH3). The experiments were conducted on forming elements in the reaction mixture depended on
the temperature and reached a maximum of 80% in
sample 170ꢀ18 (Table 1). It is noticeably higher than
that in SAPOꢀ34, for which the yields in similar synꢀ
theses did not exceed 25%.
a USGAꢀ101 chemisorption analyzer (Unisit, Rusꢀ
sia). A quartz tube reactor was charged with 0.15–
0
.20 g of the sample; standard automatic pretreatment
included sequential operations of sample calcining at
00 for 1 h in a helium flow, saturation with ammoꢀ
nia at 60
ammonia in a helium flow at 100
experiment was conducted in a helium flow (30 shown that the dimensions of axes
mL/min) at a heating rate of
°C/min; the ammonia and crystal thickness increased with an increase in
released was measured with a thermal conductivity the crystallization time and temperature. The maxiꢀ
detector.
mum crystal size was achieved in the samples obtained
at 190 . The crystal thickness in sample 190ꢀ12 was
5
°C
Crystal morphology of the obtained samples also
°
C
for 15 min, and removal of physisorbed corresponds to published data: the crystals had a shape
. The TPD NH3 of flat ellipses (Fig. 2b). The data presented in Table 1
and of the ellipse
°C
a
b
8
c
°
C
The catalytic properties of the samples in the MTO
0
.3 m, which is two and one and half times that of
µ
process were studied in a flow catalytic unit. A 1ꢀg porꢀ
tion of the catalyst (0.5–1 mm fraction) was placed in
a quartz reactor. The catalyst pretreatment involved
samples 150ꢀ72 and 170ꢀ18, respectively.
The data presented in Table 1 also show that all the
calcining at 500
°
C
for 1 h in nitrogen at a flow rate of synthesized samples have a developed porous strucꢀ
ture, as indicated by high values of pore volume and
50 mL/min. The experiment was conducted at 400°C,
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220
KASNERIK et al.
Table 1. Physicochemical properties of silicoaluminophosphates with the AEI structure
Samples
1
50ꢀ24
150ꢀ72
78
170ꢀ12
62
170ꢀ18
80
190ꢀ6
50
190ꢀ12
57
Yield of crystalline product, %
73
Crystal size, µm
a
b
c
1.0
1.0
1.0
1.1
1.3
1.4
0.50
0.15
0.60
0.55
0.65
0.70
0.80
0.17
0.18
0.20
0.20
0.30
3
Pore volume, cm /g
0.358
0.237
0.360
0.248
0.362
0.252
0.350
0.261
0.235
0.155
0.240
0.168
3
Micropore volume, cm /g
Chemical composition, mol/mol Al O :
2
3
P2O5
SiO2
0.97
0.07
1080
850
0.95
0.16
1115
910
0.94
0.10
1070
970
0.95
0.17
1100
1050
0.94
0.18
1070
1040
0.95
0.20
1120
790
+
Amount of (C H ) N ,
µ
mol/g
2
5 4
Concentration of acid sites, a0(NH3),
µ
mol/g
micropore volumes. At the same time, it should be the synthesis temperature, a general tendency toward
noted that samples 190ꢀ6 and 190ꢀ12 are noticeably growth in the number of strong acid sites in the samꢀ
inferior to their analogues in pore volume values. ples with increasing of the crystallization time was
Obviously, crystal formation at elevated temperature observed. This fact was recorded by the appearance of
has its unique features. It may be assumed that the a shoulder (for sample 150ꢀ72, Fig. 3?) or a maximum
observed decrease in the micropore volume is due to (for samples 170ꢀ18 and 190ꢀ12, Figs. 3b and 3c) at a
the presence in the crystal of zones with nonꢀthrough temperature of about 400
°C in the TPD NH curves
3
porosity, which are formed under fast crystal growth
conditions.
(
Fig. 2). Obviously, the increase in the time of syntheꢀ
sis of silicoaluminophosphates led not only to the
Analysis of the chemical constitution of the samꢀ change in the SiO2 concentration in the samples, but
ples (Table 1) shows that an increase in the synthesis also to qualitative changes of their acidic properties.
temperature and the crystallization time has almost no
To identify the nature of forming sites, the local
effect on the concentration of P2O5 and leads to an
increase in the SiO2 content of the samples. The maxꢀ
environment of silicon was studied using 29Si NMR
spectroscopy. As follows from the NMR spectra
Fig. 4) silicon in samples 150ꢀ24 and 170ꢀ12 is
mostly present in the form of isolated tetrahedra. This
is registrated by a single maximum at –91.8 ppm
Figs. 4a, 4b). Probably the SM2 mechanism impleꢀ
mentes under these conditions of silicoaluminophosꢀ
phate synthesis. An increase of the reaction time leads
to the formation of the soꢀcalled silicon islands, which
is recorded by signals at –95.5 and –109.7 ppm in the
imal SiO /Al O ratios of 0.18 and 0.20 was achieved
2
2
3
(
in samples 190ꢀ6 and 190ꢀ12, respectively.
As it has been shown in [11], the amount of the
template in the silicoaluminophosphate structure after
synthesis can serve as a quantitative characteristic of
high crystallinity of these materials. The data preꢀ
sented in Table 1 indicate that, independently of the
temperature and duration of the synthesis, the
amounts of the template in the samples are very close
and differ by no more than 4%. The concentration of
(
29
Si NMR spectra of samples 150ꢀ72 and 170ꢀ18. The
observed changes of spectra indicates that under longꢀ
term synthesis, the incorporation of silicon into the
silicoaluminophosphate structure proceeds according
to both the SM2 and the SM3 mechanism. The formaꢀ
tion of silicon islands proceeding to a smaller extent in
the case of sample 170ꢀ18 when compared to sample
+
the template cation (C H ) N in the samples is
2
5 4
1070–1120
µ
mol/g. This value confirms, together
with the XRD data, the high crystallinity of the
obtained samples.
The concentration of acid sites а0(NH3) (Table 1)
were determined using TPD of ammonia. Comparison
of the values of а0(NH3) shows that an increase in the
1
50ꢀ72, probably due to the shorter time of its crystalꢀ
lization. Under more hard conditions (synthesis temꢀ
), in the structure of silicoaluminoꢀ
50ꢀ24, 150ꢀ72, 170ꢀ12, and 170ꢀ18. In the case of the phosphates 190ꢀ6 and 190ꢀ12 (Fig. 4c). Obviously, the
samples synthesized at 190 а0(NH3) decreased with observed differences in the state of silicon are due to
an increase in the duration of synthesis. Regardless of the peculiarities of the synthesis of silicoaluminophosꢀ
crystallization time led to an increase in а0 for samples perature of 190
°C
1
°C,
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METHANOL TO OLEFINS CONVERSION
221
(а)
(b)
(c)
1
.2
.8
1.2
0.8
0.4
1.2
0.8
0.4
1
50ꢀ24
50ꢀ72
170ꢀ12
170ꢀ18
190ꢀ6
1
190ꢀ12
0
0.4
0
200
400
600 0
200
400
600 0
200
400
600
T
, °C
T, °C
T, °C
Fig. 3. Curves of TPD ammonia of silicoaluminophosphates with AEI structure.
–91.8
–91.8
–91.5
(b)
(c)
(a)
–109.7
–95.5
–109.7
1
90ꢀ12
1
70ꢀ18
150ꢀ72
1
50ꢀ24
170ꢀ12
190ꢀ6
Fig. 4. 29Si NMR spectra of silicoaluminophosphates with AEI structure.
phates at different temperatures, but this fact requires showed that gaseous С –С4 olefins, liquid С5+ and
2
special investigation.
methane were the main products of methanol converꢀ
sion. Gaseous С –С4 alkanes were formed in insignifꢀ
icant quantities, and their yield did not exceed 0.2 wt
2
The study of the catalytic properties of silicoalumiꢀ
nophosphates with AEI structure in MTO process
showed the following. All the samples had a high initial
conversion of 97–100%. As shown from data, preꢀ
sented in Fig.5, the deactivation of the samples proꢀ
ceeded at different rates. The fastest decrease of activꢀ
%. The amount of СOх and hydrogen in the products
did not exceed 1%.
The data presented in Table 2 show that the total
yield of С –С4 olefins changed from 83.0 to 90.7 wt %;
2
ity was for samples 150ꢀ24 and 170ꢀ12, which had highest yield of olefins obtained over sample 170ꢀ18.
timeꢀonꢀstream of 100 and 130 min, respectively Figure 6 demonstrates the yields of individual MTO
(
Figs. 5a, 5b). The identical patterns of the TPD NH3 products as a function of the reaction time. As follows
29
from these relationships for the yields of individual
olefins, the samples form the following series:
curves and Si NMR spectra for these samples suggest
that the cause of deactivation is associated with the
type of acid sites in these samples. For sample 190ꢀ6,
the deactivation occurred at a lower rate, and timeꢀ
onꢀstream of this sample was 230 min (Fig. 5c).
ethylene 170ꢀ18 > 150ꢀ24 > 190ꢀ12;
propylene 190ꢀ12 > 170ꢀ18 > 150ꢀ24; and
butylenes 190ꢀ12 > 150ꢀ24 > 170ꢀ18.
Samples 150ꢀ72, 170ꢀ18, and 190ꢀ12, for which the
For sample 190ꢀ12, there is a tendency toward the
timeꢀonꢀstream decreased in the order 150ꢀ24 > 170ꢀ formation of heavier products: this sample is superior
8 > 190ꢀ12 and was 430, 330, and 270 min, respecꢀ to the others in the yield of С4= and С5+ hydrocarbons
1
tively (Fig. 5), were chosen for further comparison. (Fig. 6c). It can be assumed that both this feature of
Analysis of the composition of reaction products the sample and its fast deactivation relative to that of
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222
KASNERIK et al.
1
00
100
95
90
85
80
100
95
90
85
80
(
а)
(b)
(c)
90ꢀ12
9
9
8
5
0
5
0
1
190ꢀ6
1
50ꢀ72
170ꢀ12
170ꢀ18
150ꢀ24
8
0
100 200 300 400 500
Time, min
0
100 200 300 400 500
Time, min
0
100 200 300 400 500
Time, min
Fig. 5. Change in the catalytic activity of silicoaluminophosphates with AEI structure in MTO process as a function of the synꢀ
thesis conditions.
the formation of heavy products and fast deactivation Table 2 show that there is a very high ethylene : propyꢀ
of this sample relate to samples 150ꢀ72 and 170ꢀ18 is lene molar ratio of 1.56–1.68 in the products obtained
due to a long transport pathway of the molecules parꢀ on this sample. Note that, ethylene : propylene molar
ticipating in the reaction throughout the volume of the ratios for samples 150ꢀ72 and 190ꢀ12,are also higher
crystal. The values of the crystal volume is 0.26, 0.11 than those described in literature.
3
and 0.26
µ
m for samples 190ꢀ12, 170ꢀ16 and 150ꢀ72,
In summary, conducting the synthesis of silicoaluꢀ
minophosphates with the AEI structure under mild
respectively.
The data on the catalytic activity and composition conditions (150–190°C, 6–72 h) has allow to adjust
of MTO products on sample 170ꢀ18 shows that this the physicochemical properties of the materials,
sample has an optimal combination of morphological including the crystal size, silicon content, varying of
features, acid properties, and the active site structure, structure of active site and acidity. The catalytic propꢀ
which makes it possible to achieve catalytic properties erties of silicoaluminophosphates prepared under
unusual for silicoaluminophosphate with the AEI mild conditions are determined by the combination of
structure. The catalytic properties of sample 170ꢀ18 morphological features, the activeꢀsite state, and the
noticeably differ from those of samples 150ꢀ72 and acid properties. The catalytic properties of the materiꢀ
1
90ꢀ12: it surpasses the analogues in the yield of ethylꢀ als synthesized in this study differ from those reported
ene (Fig. 6b), the value of which reaches 40.6–41.2 wt in literature by high values of the ethylene : propylene
. As a consequence, the total ethylene + propylene molar ratio in MTO products. It has been found that
yield and the yield of total lower olefins are also the silicoaluminophosphate with AEI structure syntheꢀ
%
highest among the test samples. The data presented in sized at 170
°C
for 18 h, on which the yield of total
50
40
30
20
10
50
40
30
20
10
50
(
а)
(b)
(c)
40
30
20
10
0
100 200 300 400 500
Time, min
0
100 200 300 400 500
Time, min
0
100 200 300 400 500
Time, min
Fig. 6. Yields of the products of methanol conversion in the presence of silicoaluminophosphate with AEI structure (a) 150ꢀ72,
(
b) 170ꢀ18, and (c) 190ꢀ12. Notations: (
᭹
) ethylene, (
᭡
) propylene, (
᭿
) butylenes, (*) liquid С5+ hydrocarbons, and (
᭜) meꢀ
thane.
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METHANOL TO OLEFINS CONVERSION
223
Table 2. Catalytic properties of silicoaluminophosphates with AEI structure in MTO process
Reaction time, min
Parameter of process
Sample
150ꢀ72
8
0
180
280
380
480
Total yield of olefins
C –C
85.9
89.0
85.8
87.4
90.7
88.8
88.2
89.5
83.8
87.7
83.0
84.5
2
4
170ꢀ18
90ꢀ12
1
Ethylene : propylene
molar ratio
150ꢀ72
1.22
1.56
1.05
1.34
1.62
1.10
1.39
1.68
1.12
1.40
1.57
1.40
170ꢀ18
90ꢀ12
1
lower olefins reaches 90.7 wt %, ethylene yield of up to
1.2 wt %, ethylene : propylene molar ratio up to 1.68
is the most promising.
5. K. S. Yoo, J.ꢀH. Kim, M.ꢀJ. Park, and S.ꢀJ. Kim, Appl.
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Translated by E. Boltukhina
PETROLEUM CHEMISTRY Vol. 56
No. 3
2016