Controlling the product selectivity in the conversion of methanol to the feedstock for phenol production

Article abstract of DOI:10.1039/c9ra03723c

This work investigated a novel nonpetroleum-based catalytic process of methanol to phenol. The idea was to convert methanol to produce a main product stream having a molar ratio of propylene to benzene/toluene of unity along with relatively higher-value products including para-xylene and alkenes. Such a product mix would be ideal for the manufacturing of phenol. This was achieved using a catalyst of 1.5 wt% zinc impregnated on a silica-deposited HZSM-5 zeolite at 0.1 MPa, 430 °C and 1.2 h^-1 weight hourly space velocity. HZSM-5, with its acidic sites predominately being Br?nsted acid, produced mainly alkanes and aromatics, of which a good fraction was undesirable nine- or more-nine-carbon higher aromatics. Silica deposition on HZSM-5 passivated the catalytic activity outside the HZSM-5 pores, resulting in an increase of alkenes selectivity, a sharp decrease of nine- or more-nine-carbon higher aromatics selectivity, and a shift of the xylene product from an equilibrium mixture of meta-xylene, para-xylene, and ortho-xylene to mostly para-xylene. Impregnation of 1.5 wt% zinc on silica-deposited HZSM-5 generated more Lewis acid sites and further increased alkene selectivity, which, with the proper selection of process conditions, led to the production of the target stream. A detailed analysis of the effects of silica deposition, zinc impregnation, acidic sites, and process conditions on the catalyst performance was presented.

Full text of DOI:10.1039/c9ra03723c

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Controlling the product selectivity in the
conversion of methanol to the feedstock for
Cite this: RSC Adv., 2019, 9, 23864
phenol production†
Abhay Suresh Zambare,
John Ou, David Shan Hill Wong, Ching-Wen Yao
*
and Shi-Shang Jang
This work investigated a novel nonpetroleum-based catalytic process of methanol to phenol. The idea was to
convert methanol to produce a main product stream having a molar ratio of propylene to benzene/toluene of
unity along with relatively higher-value products including para-xylene and alkenes. Such a product mix
would be ideal for the manufacturing of phenol. This was achieved using a catalyst of 1.5 wt% zinc
impregnated on a silica-deposited HZSM-5 zeolite at 0.1 MPa, 430 ꢀC and 1.2 hꢁ1 weight hourly space
velocity. HZSM-5, with its acidic sites predominately being Brønsted acid, produced mainly alkanes and
aromatics, of which a good fraction was undesirable nine- or more-nine-carbon higher aromatics. Silica
deposition on HZSM-5 passivated the catalytic activity outside the HZSM-5 pores, resulting in an increase
of alkenes selectivity, a sharp decrease of nine- or more-nine-carbon higher aromatics selectivity, and
a shift of the xylene product from an equilibrium mixture of meta-xylene, para-xylene, and ortho-xylene to
mostly para-xylene. Impregnation of 1.5 wt% zinc on silica-deposited HZSM-5 generated more Lewis acid
sites and further increased alkene selectivity, which, with the proper selection of process conditions, led to
Received 17th May 2019
Accepted 16th July 2019
DOI: 10.1039/c9ra03723c
the production of the target stream.
A detailed analysis of the effects of silica deposition, zinc
rsc.li/rsc-advances
impregnation, acidic sites, and process conditions on the catalyst performance was presented.
HZSM-5), silica-deposited HZSM-5 (Si/HZSM-5), and zinc-
impregnated silica deposited HZSM-5 (Zn/Si/HZSM-5) found
1. Introduction
in the literatures. The impregnation of Zn on HZSM-5 in general
increased aromatics selectivity and decreased alkanes
(methane, ethane, propane, butanes) selectivity. However, the
effects of adding Zn on alkenes and P selectivities were much
less certain and were different in different studies. For example,
Zhang et al.9 and Xu et al.10 observed an increase in alkenes
selectivity. Conte et al.11 observed a signicant decrease in
alkenes selectivity while Li et al.13 saw a small reduction in
alkenes selectivity. With regard to the p-X byproduct, on all Zn-
modied HZSM-5 catalysts, the purity of p-X in xylenes (p-X/X)
was around 24.0% except for the 72.4% by Xu et al.10
Silica deposition on HZSM-5 would shi the undesirable m-X,
o-X, and nine- or more-nine-carbon higher aromatics (A9+) to the
more desirable p-X, as shown in the appendix, Table 7. However,
changes in the selectivities for alkanes, alkenes, and P were quite
different in these studies.13,16 The alkenes selectivity was very high
on Li et al. catalyst.16 The discrepancy could be due to the differ-
ences in catalysts (e.g. SiO2/Al2O3 of 30 (ref. 13) vs. 50, 200 (ref. 16))
and/or reaction temperatures (460 (ref. 13) vs. 400 ꢀC (ref. 16)).
There were only a few published results on Zn/Si/HZSM-
5.12–14 Only Li et al.13 reported the selectivities of alkenes and
The objective of this work was to demonstrate a novel nonpe-
troleum route for methanol to phenol. Phenol is an important
chemical feedstock for the production of phenolic resins,
synthesis of adipic acid, bisphenol, chloro- and nitrophenols,
caprolactam phenol sulfonic acids, etc. Cumene production,
which is the rst step of phenol production requires a propylene
(P) to benzene (B) molar ratio of approximately one.1 The idea
was to convert methanol to a product having a molar ratio of P
to B and toluene (T) of unity, along with such valuable
byproducts as para-xylene (p-X) and alkenes (ethylene, P, and
butenes). As the chemical industry oen converts T to B, such
a product would be ideal for the manufacturing of phenol.
Many studies have been carried out for the conversion for
methanol to aromatics (MTA) by adding metal species such as
zinc,2,3 silver,4 gallium,5 nickel,6,7 etc. on HZSM-5. Among all the
metal species, zinc has received considerable attention due to
its good selectivity toward aromatics, relatively low cost, and
being less toxic.8–15 In the appendix, Table 7 lists the catalytic
performances of HZSM-5, zinc-impregnated HZSM-5 (Zn/
Department of Chemical Engineering, National Tsing Hua University, Hsinchu
Taiwan, Republic of China. E-mail: ssjang@mx.nthu.edu.tw; Tel: +886-3-573-5294
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c9ra03723c
aromatics. They observed
a substantial increase in the
combined selectivity for B, T, and p-X. However, alkenes selec-
tivity decreased marginally.
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Throughout the literatures on methanol conversion, none of mixture for 0.5 hour (h) at ambient temperature. Aer 0.5 h, n-
the authors reported P/BT molar ratio. We have calculated their hexane was rota-evaporated under vacuum to obtain PPMS-
molar ratios based on available data shown in Table 7. The modied NH4-ZSM-5 which was further calcined at 120 ꢀC
values range from 0.2 to 4.4. Xu et al.10 and Conte et al.11 reported rst in N2 (350 ml minꢁ1, 1.5 h) and then in the air (350
P/BT molar ratio of 0.9 and 1.4 respectively, which are closest to ml minꢁ1, 6 h) at 550 ꢀC to obtain silica deposited HZSM-5. The
our objective. However, the selectivities of P, B, and T were very procedure was repeated three times to obtain the nal external
low in Xu et al.'s10 work. In both studies, a substantial amount of surface passivated catalyst denoted as Si/HZSM-5.
undesirable aromatics (m-X, m-X, and A9+) were reported.
The NH4-ZSM-5 powder was calcined at 550 ꢀC for 5 h under
In the literatures, the HZSM-5 used for methanol to N2 atmosphere to obtained HZSM-5 powder. The HZSM-5
aromatics contained high amount of Brønsted acid sites (BAS) powder (15 g) was wet impregnated with a solution of zinc
compared to that of Lewis acid sites (LAS).3,9,10,13 Zn impregna- nitrate hexahydrate (0.69 g in 12 ml water) and aged for 2 h to
tion on such HZSM-5 decreased BAS and increased LAS signif- attend equilibrium. Aer 2 h, the mixture was directly calcined
icantly.3,9,10,13 This resulted in an increase in the aromatics under N2 atmosphere (350 ml minꢁ1) for 3 h at 120 ꢀC and then
selectivity and a decrease in alkanes selectivity.3,9,10,13 The at 550 ꢀC for 5 h to obtain theoretically 1 wt% Zn impregnated
increase in the aromatic selectivity was attributed to Zn-LAS HZSM-5, which was pressed (10 tons cmꢁ2 for 1 min), crushed,
(ZnOH+) that could accelerate aromatization and dehydroge- and sieved to obtain catalyst pellets of 30–50 mesh denoted as
nation reactions. The selectivity of alkenes varied in different 1.0 wt% Zn/HZSM-5. The Zn was impregnated on Si/HZSM-5
studies, however. For example, Zhang et al.9 and Xu et al.10 re- pellets using the similar procedure used for 1.0 wt% Zn/
ported an increase in alkenes selectivity while Li et al.13 reported HZSM-5. The Si/HZSM-5 (15 g) were wet impregnated with
a small decrease in alkenes selectivity.
a solution of zinc nitrate hexahydrate (0.69 g in 12 ml water) and
Si deposition on HZSM-5 decreased BAS and LAS respec- aged for 2 h to attend equilibrium. Aer 2 h, the mixture was
tively.13,16 The deposition appeared to decrease the aromatics directly calcined under N2 atmosphere (350 ml minꢁ1) for 3 h at
selectivity.13,16 Most of the reduction was probably due to the 120 ꢀC and then at 550 ꢀC for 5 h to obtain theoretically 1 wt%
absence of acid sites outside the zeolitic pores. The effects of Si Zn impregnated Si/HZSM-5 denoted as 1.0 wt% Zn/Si/HZSM-5.
deposition on alkenes and alkanes selectivities were very different Similarly, 1.5 wt% Zn was impregnated on Si/HZSM-5 to
in the literatures, however. Li et al.13 reported that although obtain theoretically 1.5 wt% Zn impregnated Si/HZSM-5 deno-
alkenes selectivity had increased to 8.9%, alkanes was still the ted as 1.5 wt% Zn/Si/HZSM-5.
main product with its selectivity increased to 49.7%. On the other
hand, Li et al.16 showed that alkanes selectivity had dropped
sharply and that alkenes had become the most abundant product.
2.2 Catalysts characterization
Zn impregnation on Si/HZSM-5 signicantly decreased BAS
2.2.1 X-rays diffraction (XRD) measurements. X-ray
and increased LAS inside the zeolitic pores of Si/HZSM-5.13 This diffraction data were obtained at a Cu-Ka radiation (a ¼
resulted in an increase in aromatics selectivity and a signicant 1.5418 A0) operated at 40 kV and 20 mA. The samples were
decrease in alkanes selectivity with a minor increase in alkenes scanned between a 2q range of 5ꢀ–60ꢀ at 5ꢀ minꢁ1 (Ultima IV,
selectivity. The increase in aromatics selectivity was attributed Rigaku, 9407F701).
to the increased Zn-LAS inside the zeolitic pores of Si/HZSM-5
that promoted aromatization and dehydrogenation reactions.
2.2.2 BET measurements. The specic surface area and pore
volume of the catalysts were measured by N2 adsorption–
From the aforementioned results, we can see that the desorption at 77 K (Micromeritcs ASAP 2020). Before the
product selectivities of methanol conversion could be manipu- measurement, the zeolite samples were degassed at 400 ꢀC for 8 h.
lated with Zn impregnation and Si passivation. In this work, the
technical feasibility of methanol to phenol was evaluated using TPD). NH3-TPD was performed on a Micromeritics AutoChem II
HZSM-5, Zn/HZSM-5, Si/HZSM-5, and Zn/Si/HZSM-5 as cata- chemisorption analyzer equipped with
TCD detector.
2.2.3 Temperature programmed desorption of NH3 (NH3-
a
lysts. The effects of Zn impregnation, Si passivation, acidic sites, Approximately 100 mg of sample was heated to 550 ꢀC at the rate
and process conditions on catalyst performance were analyzed. of 10 ꢀC minꢁ1 under He ow of 50 ml minꢁ1. The temperature
was maintained at 550 ꢀC for 1 h to remove adsorbed water and
other gases. Aer cooling down to 150 ꢀC, the He ow was
2. Experimental section
2.1 Catalyst preparation
switched with a ow of 10 mole% NH3 in He at 25 ml minꢁ1 for
1.5 h to facilitate the adsorption of NH3 on the sample. Aer
NH4-ZSM-5 with a SiO2/Al2O3 molar ratio of 30 with approxi- adsorption of NH3, the sample was purged with a He ow at 25
mately 0.3 to 0.5 mm crystal size17 (obtained from Zeolyst ml minꢁ1 for 1 h at 150 ꢀC to remove physisorbed NH3. Then the
International) was pressed (10 tons cmꢁ2 for 1 min), crushed sample temperature was programmed to 650 C at the rate of
ꢀ
and sieved to get NH4-ZSM-5 pellets of 30–50 mesh. Silica 10 ꢀC minꢁ1 and the signal was measured using a TCD.
deposition on these NH4-ZSM-5 pellets was carried out using
2.2.4 Acidity measurement by pyridine and 2,4,6-trime-
chemical liquid deposition of polyphenylmethylsiloxane thylpyridine FTIR. Pyridine adsorption infrared spectra (Py-IR)
(PPMS). Typically, NH4-ZSM-5 pellets (60.0 g) were added to were measured on a PerkinElmer Spectrum One FT-IR Spec-
a mixture of n-hexane (200.0 g) and PPMS (17.17 g, 4 wt% SiO2 trometer equipped with TGS detector. First, the self-supporting
with respect to the zeolite) followed by rotating the solid–liquid sample pellet (approximately 70 mg, 13 mm in diameter) was
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ꢀ
heated to 400 C for 1 h under high vacuum in a Harrik high- was loaded in the center of the reactor and the catalyst bed was
ꢀ
temperature cell to remove moisture and other adsorbed gases heated in N2 stream from ambient temperature to 430 C. The
from the sample. The spectrum of the self-supporting sample temperature of the catalyst bed was monitored using three K-
pellet was recorded at 150 ꢀC and used as a background for the type thermocouples (TC) placed on the external surface of the
adsorbed pyridine test. Aer recording the background, the self- reactor wall as shown in Fig. 1. Aer reaching the desired
supporting pellet was cooled to room temperature and soaked in temperature of 430 ꢀC, the N2 ow was shut-off and a methanol
the pyridine for 30 min. Aer soaking, the self-supporting pellet ow (0.1 ml minꢁ1) was cut in using a calibrated syringe pump.
was heated at 150 ꢀC for 1 h in N2 owrate (15 ml minꢁ1) to The methanol passed through a preheater at 235 C, then into
ꢀ
remove physisorbed pyridine and then Py-IR spectra was recor- the reactor over the catalyst bed.
ded. Aerward, the catalyst sample was respectively heated to
The gaseous product mixture at the reactor outlet was passed
250, and 350 C. At each temperature, the catalyst sample was through the condenser maintained at ꢁ5 ꢀC to separate the gas
heated for 1 h respectively in N2 owrate (15 ml minꢁ1) and a Py- and liquid products. The gaseous hydrocarbons were analyzed
IR spectrum was recorded at the respective temperature. The by a GC (Agilent 7890B) equipped with a capillary column (DB-1)
same procedure was used to determine total external acid sites on FID mode and non-hydrocarbons (CO, CO2, and H2) were
using a probe molecule 2,4,6-trimethylpyridine (kinetic diam- analyzed using capillary column (ShinCarbon ST 120) on TCD
eter 0.74 nm). The concentration of acid sites on the catalysts mode. The volume of gas was measured by a wet test gas meter.
ꢀ
was calculated by the following equation.18
CL ¼ (p/IMECL) ꢂ (r2/w) ꢂ A1450
CB ¼ (p/IMECB) ꢂ (r2/w) ꢂ A1540
The gas was sampled and analyzed online two times to obtain
the two data points for gas composition. The rst sample was
taken at 5 minutes aer cutting in methanol and the second
sample at 60 minutes. For the test of 1.5 wt% Zn/Si/HZSM-5,
however, only the 60 min sample was taken. Then the weight
of gas component i was obtained by combining the two gas
readings from the experimental data of gas products.
The liquid products were sampled and analyzed offline at
60 min aer cutting in methanol. The liquid hydrocarbons were
separated from the water and analyzed on a GC (Agilent 7890B)
equipped with a capillary column (DB-1) on FID mode. A second
GC (Agilent 7820A) equipped with a capillary column (HP-
INNOWAX) on FID mode was used to determine the composi-
tion of xylene (X) isomers. The water was also analyzed on a GC
Where CL and CB are the concentration of Lewis (L) and
Brønsted (B) acid sites in mmol gꢁ1; A1450 and A1540 are inte-
grated areas of bands at 1450, and 1540 cmꢁ1; IMECL, and
IMECB are molar extinction coefficients of 2.22 and 1.67 cm
mmolꢁ1, respectively. r is the pellet radius in cm and w is the
pellet weight in mg.
2.3 Catalyst activity measurement
The conversion of methanol was performed in a continuous x (Agilent 7890B) equipped with a capillary column (DB-1) in FID
bed stainless steel reactor (54 cm in length and 1.27 cm inner mode to analyze DME, methanol or hydrocarbon if present.
ꢀ
diameter) at 430 C and 0.1 MPa. A schematic view of the lab Then the weight of component i in liquid hydrocarbons was
calculated from the experimental data of liquid hydrocarbon
scale setup is shown in Fig. 1. The desired amount of catalyst
Fig. 1 A schematic view of the lab scale setup.
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products. The conversion of methanol, the selectivity of
component i and the carbon balance were calculated by the
following equations.
MeOHin ꢁ MeOHout
Conversion of methanol ð%Þ ¼
ꢂ 100
MeOHin
Selectivity of component i ðwt%Þ
Weight of component i
¼
ꢂ 100
Weight of hydrocarbons and nonhydrocarbons
WCout
Carbon balance ð%Þ ¼
ꢂ 100
WCin
Where WCout is the weight of the outlet C element and WCin is
the weight of the inlet C element.
The C4-hydrogen transfer index (C4-HTI), which is a param-
eter to measure the activity for hydrogen transfer19,20 was calcu-
lated as the combined selectivity of n-butane and iso-butane
divided by the total C4 selectivity. The selectivity of hydrogen (H2)
from aromatization was separated from the selectivity of H2 from
methanol decomposition using the following equation.
Fig. 2 XRD patterns of the parent HZSM-5, and the modified HZSM-5
catalysts.
(2q ¼ 31.6ꢀ, 36.1ꢀ) were observed on Zn modied catalysts,
suggesting that Zn species were highly dispersed8,12 on HZSM-5
and Zn/Si/HZSM-5 catalysts.
3.1.2 Surface areas and pore volumes. The results of N2
adsorption of the catalysts are listed in Table 1, from Table 1 it
can be seen that the specic surface area and the pore volume
decreased on Si/HZSM-5 catalyst. The silica deposition occurred
preferentially on the external surface of the HZSM-5 catalyst
because PPMS is too large in molecular size to enter the zeolite
channels.13
The decrease in the pore volume on the Si/HZSM-5 catalyst was
probably due to channel blocking by the silica deposition. The Zn
impregnation on HZSM-5 did not seem to affect the specic
surface area and the pore volume to a greater extent compared to
that of HZSM-5 catalyst. The impregnation of Zn on Si/HZSM-5
catalyst further decreased moderately the specic surface area
and the pore volume compared to that of the Si/HZSM-5 catalyst.
3.1.3 Acidity of catalysts. The amount and strength of acid
sites on HZSM-5 and modied catalysts were determined by
NH3-TPD. The NH3-TPD proles of the catalysts are shown in
Fig. 3. The amount of acid sites obtained on different catalysts is
given in Table 2.
Selectivity of H2 ðwt%Þ
Weight of H2 ꢁ Weight of H2 from COx
¼
Weight of hydrocarbons and nonhydrocarbons
In the conversion of methanol, the molecular H2 generated is
attributed to the two aspects. First due to aromatization reac-
tion and second due to methanol decomposition which forms
COx and H2. Hence, the selectivity of H2 calculated using the
above equation can be used to verify aromatization reactions on
the catalysts.
The weight of H2 from methanol decomposition can be
estimated from the amounts of CO and CO2 found in the
reaction products based on the following reaction equations.
CH3OH + H2O / CO2 + 3H2
CH3OH / CO + 2H2
3. Results and discussion
Table 1 Textures of HZSM-5 and modified HZSM-5 catalysts
Specic surface
3.1 Physical and chemical properties of catalysts
3.1.1 X-rays diffraction (XRD) analysis. The Fig. 2 shows the
XRD patterns of the catalysts. From Fig. 2, it can be seen that the
XRD peaks for the modied HZSM-5 catalysts were very similar
to those of HZSM-5. No new diffraction peak was observed
which suggested that the MFI structure of HZSM-5 catalyst was
intact and no new phase was produced aer the modication of
HZSM-5 catalyst.13 No characteristic diffraction peak of SiO2 (2q
¼ 22ꢀ) on Si modied HZSM-5 was observed suggesting silica
species were well dispersed on the external surface outside the
pores of the HZSM-5. No characteristic diffraction peaks of ZnO
area (m2 gꢁ1
)
Pore volume (cm3 gꢁ1
)
c
Catalysts
aSBET bSmicropore Pvol
bVmicro Vmesopore
HZSM-5
1 wt% Zn/HZSM-5
Si/HZSM-5
1 wt% Zn/Si/HZSM-5
1.5 wt% Zn/Si/HZSM-5 235
322
321
258
244
216
199
196
185
178
0.26 0.12
0.25 0.11
0.23 0.11
0.21 0.10
0.20 0.09
0.15
0.15
0.12
0.11
0.10
a
BET method. b t-plot method. c Vmeso ¼ Pvol – Vmicro
.
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The high-temperature peak observed around 425 ꢀC
reduced to a greater extent for all Zn-impregnated catalysts.
From Fig. 3, it can be said that the impregnation of Zn on
HZSM-5 not only shied the peak position from 245 ꢀC to
255 ꢀC but also reduced the total acidity. In particular, the
amount of strong acid sites reduced from 430 mmol gꢁ1 to 225
mmol gꢁ1. However, the amount of medium acid sites
increased slightly from 230 mmol gꢁ1 to 252 mmol gꢁ1 (Table 2).
Silica deposition on HZSM-5 not only changed the peak posi-
ꢀ
ꢀ
tion of acid sites from 425 C on HZSM-5 to 380 C but also
decreased amount of medium acid sites from 230 to 200 mmol
gꢁ1 and amount of strong acid sites from 430 to 167 mmol gꢁ1
.
The impregnation of Zn on Si/HZSM-5 further decreased
amount of both medium and strong acid site compared to that
of HZSM-5. The amount of medium acid sites were 180 mmol
gꢁ1 and 173 mmol gꢁ1 on 1.0 wt% Zn/Si/HZSM-5 and 1.5 wt%
Zn/Si/HZSM-5, respectively. The amount of strong acid sites
were 150 mmol gꢁ1 and 133 mmol gꢁ1 on 1.0 wt% Zn/Si/HZSM-5
and 1.5 wt% Zn/Si/HZSM-5, respectively.
Fig. 3 NH3-TPD profiles of HZSM-5, Zn/HZSM-5, Si/HZSM-5, and Zn/
Si/HZSM-5.
The Py-IR was performed to detect the nature and amount of
acid sites. Fig. 4a shows the pyridine spectra of unmodied and
modied HZSM-5 catalysts. The amount of total acid sites, LAS
and BAS of the catalysts are given in Table 3.
Table 2 Acidity information of catalysts by NH3-TPD
Amount of acid sites (mmol gꢁ1
Total Medium (150–350 ꢀC) Strong (>350 ꢀC)
)
Fig. 4a shows that three characteristic peaks around 1453,
1540, and 1490 cmꢁ1, which can be attributed to LAS, BAS, and
LAS + BAS sites,21 appeared in all of the samples. From Fig. 4a,
for HZSM-5 catalyst, it can be observed that the number of the
BAS are much more compared to that of the LAS indicating that
BAS dominate on the HZSM-5 catalyst. The impregnation of Zn
on HZSM-5 sharply increased LAS and decreased BAS. The
amount of total acid sites on 1.0 wt% Zn/HZSM-5 decreased
from 300 mmol gꢁ1 on HZSM-5 to 231 mmol gꢁ1. Hence, the
nature of acid sites changes with the impregnation of Zn
species. This phenomenon has been reported in may research
papers.21–24 On Si/HZSM-5 catalyst, the amount of both BAS and
LAS decreased, the amount of BAS decreased to a greater extent
Catalyst
HZSM-5
1.0 wt% Zn/HZSM-5
Si/HZSM-5
660 230
477 252
367 200
430
225
167
150
133
1.0 wt% Zn/Si/HZSM-5 330 180
1.5 wt% Zn/Si/HZSM-5 306 173
From Fig. 3, two typical desorption peaks for the HZSM-5
catalyst centering at around 245 ꢀC and 425 ꢀC are observed
and are ascribed to NH3 desorption from medium and strong
acid sites, respectively.
Fig. 4 (a) Py-FTIR of HZSM-5, Zn/HZSM-5, Si/HZSM-5, and Zn/Si/HZSM-5 (solid line for desorption at 250 ꢀC and dashed line for desorption at
350 ꢀC). (b) 2,4,6-trimethylpyridine -FTIR of HZSM-5, Si/HZSM-5, and Zn/Si/HZSM-5 at 250 ꢀC.
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Table 3 The acidity of the catalysts measured from pyridine and 2,4,6-
trimethylpyridine IR
between the intrinsic acid sites and the Zn species due to which
partial BAS are converted into Zn-LAS21 (preferentially ZnOH+
species). As reported in the literature, Zn-LAS (ZnOH+ species)
have the ability to accelerate the process of aromatization.25
The external acid sites determined using 2,4,6-trime-
thylpyridine is illustrated in Fig. 4b. The external acid sites
account for 28%, 25%, 6%, 3% and 5% of the total acidity for
HZSM-5, 1.0 wt% Zn/HZSM-5, Si/HZSM-5, 1.0 wt% Zn/Si/HZSM-
5, and 1.5 wt% Zn/Si/HZSM-5, respectively as shown in Table 3.
The signicant reduction in the acidity on Si/HZSM-5 and Zn/Si/
ZSM-5 validated that the external acid sites were signicantly
reduced aer the catalyst modications.
Amount of acid sites
bExternal
acidity/
total
(mmol gꢁ1
)
aTotal
(LAS + BAS)
Catalyst
aLAS
aBAS
acidity (%)
HZSM-5
1.0 wt% Zn/HZSM-5
Si/HZSM-5
1.0 wt% Zn/Si/HZSM-5
1.5 wt% Zn/Si/HZSM-5
300
231
160
158
147
20
108
16
52
59
280
123
144
106
88
28
25
6
3
5
a
determined by Py-IR. b determined by 2,4,6-trimethylpyridine IR.
3.2 Performance of the catalyst
The conversion of methanol on all the catalysts was above
99.0% for 1 h and no DME was detected under the reaction
conditions used. The higher temperature favors decomposition
of methanol to COx and H2 which can reduce the aromatic
selectivity. Hence, all the experiments were performed at 430 ꢀC
to avoid high methanol decomposition. The carbon balance for
all the runs was above 98%.
3.2.1. Effect of zinc impregnation. The performance of
1.0 wt% Zn/HZSM-5 in terms of product selectivity is shown in
Fig. 5, also shown is that of HZSM-5 for comparison. The C4-HTI
(Fig. 4a). The amount of total acid sites decreased signicantly
from 300 mmol gꢁ1 on HZSM-5 to 160 mmol gꢁ1 on Si/HZSM-5.
The impregnation of Zn on Si/HZSM-5 catalysts increased
the amount of LAS and decreased the amount of BAS (Fig. 4a).
The amount of total acid sites on 1.0 wt% Zn/Si/HZSM-5 and
1.5 wt% Zn/Si/HZSM-5 were 158 mmol gꢁ1 and 147 mmol gꢁ1
,
respectively compared to that of 300 mmol gꢁ1 on HZSM-5. The
change BAS and LAS is attributed to the strong interaction
Fig. 5 (a) Selectivity of aromatics, alkanes, and alkenes on different catalysts. (b) Selectivity of B, T, p-X, P, A9+ and m,o-X on different catalysts.
(c) p-X/X, P purity and P/BT molar ratio. (d) Hydrogen selectivity and C4-HTI; Reaction conditions: 0.1 MPa, 430 ꢀC, WHSV ¼ 1.6 hꢁ1, the data were
obtained at 1 h.
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of the two catalysts is given in Fig. 5d. The HZSM-5 catalyst
As shown in Fig. 5c, the HZSM-5 catalyst demonstrated a P/
produced alkanes (51.4 wt%) and aromatics (35.3 wt%) as the BT molar ratio of 0.2. Impregnating 1.0 wt% Zn had no effect on
main products. Amongst the aromatics, the desired BTp-X the P/BT molar ratio.
accounted for 19.4 wt%, and the rest (16.0 wt%) went to lower-
3.2.2. Effect of external surface passivation. Silica deposi-
valued m-X, o-X, and A9+. The P/BT molar ratio was only at 0.2. tion on HZSM-5 was accomplished using PPMS to selectively
Compared to the performance of HZSM-5, 1.0 wt% Zn/HZSM-5 eliminate the acid sites outside the channels and increase the
shied alkanes (18.4 wt%) to aromatics (48.4 wt%).
shape selectivity of HZSM-5. The changes in product distribution
A good fraction of the shiing, however, was directed toward over Si/HZSM-5 catalyst compared to that of HZSM-5 are shown
m-X, o-X, and A9+ (24.9 wt%), resulting in a combined BTp-X in Fig. 6. The Si/HZSM-5 catalyst showed an aromatics selectivity
selectivity of 23.6 wt%. A small increase in the selectivity of of 31.0 wt%, of which the majority (29.4 wt%) was the desired B,
alkenes (4.9 wt% to 6.1 wt%) was observed (Fig. 5a). The T, and p-X, an alkenes selectivity of 22.0 wt%, and an alkanes
impregnation of 1.0 wt% Zn had no appreciable effect on the P selectivity of 33.8 wt%. Compared to the performance of HZSM-5,
selectivity. However, the purity of P (P/C3) increased due to Si/HZSM-5 raised the combined BTp-X selectivity from 19.4 wt%
a decrease in the selectivity of and C3 alkane (Fig. 5c). The results to 29.4 wt%, increased the P selectivity (from 1.3 wt% to 7.0 wt%)
on aromatics selectivity is consistent with those reported in the and the alkenes selectivity (from 4.9 wt% to 22.0 wt%), and
literature. The small increase in P selectivity (from 1.3 wt% to reduced the alkanes selectivity (from 51.4 wt% to 33.8 wt%).
1.6 wt%) was similar to that of Zhang9 and Xu et al.10 It should be
The benets of silica deposition are clear. It signicantly
noted that the selectivity of H2 on HZSM-5 was less because the reduced the combined selectivities of A9+, m-X, and o-X from
H2 generated from aromatization was most probably consumed 16.0 to 1.6 wt%, shiing these undesired aromatics to the
via hydrogen transfer reaction to form alkanes. On 1.0 wt% Zn/ wanted B, T, and p-X. Furthermore, the catalyst's shape selec-
HZSM-5, hydrogen selectivity increased sharply and hydrogen tivity raised the p-X selectivity from a mere 2.8 wt% to 11.5 wt%,
transfer index decreased (Fig. 5d), indicating that zinc impreg- with the p-X purity in X reaching 98.2%. Equally benecial is the
nation promoted aromatization, reduced hydrogen transfer, and shiing of alkanes (decreasing from 51.4 to 33.8 wt%) to P and
facilitated the formation of hydrogen molecules.
alkenes. Fig. 6d showed a decreased C4-HTI, which was
Fig. 6 (a) Selectivity of aromatics, alkanes, and alkenes on different catalysts. (b) Selectivity of B, T, p-X, P, A9+ and m,o-X on different catalysts.
(c) p-X/X, P purity and P/BT molar ratio. (d) Hydrogen selectivity and C4-HTI; Reaction conditions: 0.1 MPa, 430 ꢀC, WHSV ¼ 1.6 hꢁ1, the data were
obtained at 1 h.
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probably due to the loss of the acid sites on the external surface.
Thedifferences in performance between 1.0 wt% Zn and
As the change in aromatics selectivity was relatively minor 1.5 wt% Zn were small, with 1.5 wt% Zn making more alkenes
compared to the decrease in alkanes selectivity and increase in and P. Compared to the performance of Si/HZSM-5, 1.5 wt% Zn/
alkenes selectivity, it may be inferred that a substantial amount Si/HZSM-5 further reduced alkanes selectivity (14.7 wt%), raised
of alkenes were converted into alkanes via the hydrogen transfer alkenes selectivity (38.7 wt%) and P selectivity (12.1 wt%), and
route on the surface outside the channels. Fig. 6c shows that kept the combined BTp-X selectivity at 30.5 wt%. The slightly
silica deposition help raise the P/BT molar ratio from 0.2 to 0.8. lower selectivity of H2 (Fig. 7d) on 1.5 wt% Zn/Si/HZSM-5
3.2.3 Effect of zinc impregnation on Si/HZSM-5. The compared to that of 1 wt% Zn/Si/HZSM-5 was most likely due
product distributions for the Zn/Si/HZSM-5 catalysts are shown in to an experimental and/or instrumental error. Fig. 7d shows
Fig. 7. Unlike the shiing of alkanes to aromatics by impregnating that Zn impregnation on Si/HZSM-5 promoted the formation of
Zn on HZSM-5, impregnating Zn on Si/HZSM-5 shied alkanes to molecular hydrogen and suppressed the hydrogen transfer
alkenes and P (Fig. 7a and b). Both 1.0 wt% Zn/Si/HZSM-5 and reaction, leading to an increase of propylene purity from 29.0 to
1.5 wt% Zn/Si/HZSM-5 showed a signicant shiing of alkanes to 65.4% (Fig. 7c). Such a performance led to a P/BT molar ratio of
alkenes and P, without changing much of the combined BTp-X 1.7 as shown in Fig. 7c. The catalyst 1.5 wt% Zn/Si/HZSM-5 was
selectivity. Li et al.13 impregnated 1 wt% zinc on Si/HZSM-5 and considered as better compared to that of other catalysts not only
observed a large increase in aromatics selectivity accompanied by because it led to a high P/BT molar ratio of 1.7 but also showed
a similarly large decrease in alkanes selectivity as well as decreases higher selectivities towards p-X and alkenes simultaneously
in alkenes and P selectivities. The differences observed between under reaction conditions used.
this work and Li et al.13 work may be due to variations in catalyst
preparation methods, high amount of acidity on the catalyst, and
reaction conditions. For instance, On Li et al.13 1 wt% Zn Si/HZSM-
3.3 Effect of acidity on the performance
5, the total acidity determined by NH3-TPD was 1080 mmol gꢁ1
In this study, we were changing the nature of acidic sites, such
while in this work, the total acidity on 1 wt% and 1.5 wt% Zn
as creating LAS and reducing BAS. Our analysis, therefore,
modied Si/HZSM-5 was 330 and 306 mmol gꢁ1 respectively.
focused on pyridine-adsorption data because pyridine
Fig. 7 (a) Selectivity of aromatics, alkanes, and alkenes on different catalysts. (b) Selectivity of B, T, p-X, P, A9+ and m,o-X on different catalysts.
(c) p-X/X, P purity and P/BT molar ratio. (d) Hydrogen selectivity and C4-HTI; Reaction conditions: 0.1 MPa, 430 ꢀC, WHSV ¼ 1.6 hꢁ1, the data were
obtained at 1 h.
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adsorption provided more information on the nature of acidic P was available for hydrogen transfer to propane. Similar
sites than did NH3-TPD.
observations had been reported in other works.2,3,9,13
3.3.1. HZSM-5 vs. Zn/HZSM-5. Our HZSM-5 possessed
3.3.2 HZSM-5 vs. Si/HZSM-5. Si passivation of the HZSM-5
a large quantity of BAS and a few LAS (Table 4). Considering the led to a signicant (48.5%) decrease in BAS, and a smaller
facts that HZSM-5 produced mainly alkanes and aromatics, and (20%) decrease in LAS (Table 5). The majority of the decreases
that the alkanes selectivity was much higher than the aromatics could probably be attributed to the passivation of the acidic sites
selectivity, one could infer that BAS promoted hydrogen transfer outside the zeolitic pores. The decrease in acidity, especially the
more strongly than aromatization as the very high alkanes decrease in Brønsted acid, appeared to be responsible for the
selectivity and the relatively high C4-HTI indicated. Impregna- large decreases of C4-HTI (ꢁ39.5%) and alkanes selectivity(-
tion of Zn on the HZSM-5 reversed the alkanes and the 34.2%) and the corresponding increase of alkenes selectivity. The
aromatics selectivities. Zn/HZSM-5 still produced mainly passivation reduced A9+ selectivity sharply, indicating that most
alkanes and aromatics, but now the aromatics selectivity was of the A9+ were made outside the zeolitic pores. On the other
much higher than the alkanes selectivity. Pyridine data showed hand, the selectivity for BTX was essentially unchanged, implying
that Zn impregnation reduced BAS, but increased LAS, both that most of the BTX were formed inside the zeolitic pores.
substantially. The decrease of BAS was more than the increase of
3.3.3 Si/HZSM-5 vs. Zn/Si/HZSM-5. Table 6 shows that
LAS, however, leading to a net decrease of total acidic sites. It impregnation of Zn on Si/HZSM-5 further decreased BAS, but
seemed apparent that the Zn-LAS promoted aromatization as increased LAS. As BAS decreased more than LAS increased, total
reected by the large increase in aromatics selectivity. It was acid sites decreased with increasing Zn loading. However,
a cross-the-board selectivity increase for all aromatics, including impregnating Zn on Si/HZSM-5 did not show the same effects as
BTX and A9+, however. The C4-HTI was only slightly weakened, impregnating Zn on HZSM-5. As discussed in Section 3.3.1,
implying that the Zn-LAS could also promote hydrogen transfer. impregnating Zn on HZSM-5 raised the aromatics selectivity,
The reversal of the alkanes and the aromatics selectivities sug- reversing the alkanes and the aromatics selectivities. Impreg-
gested that Zn-LAS promoted hydrogen transfer less strongly nating Zn on Si/HZSM-5 neither raise the aromatics selectivity,
than it promoted aromatization. This could also be inferred in fact the aromatics and BTX selectivities remained largely
from the fact that the reduction of alkanes selectivity was mostly unchanged, and nor reverse the alkanes and the aromatics
from the reduction of propane (from 28.9% on HZSM-5 to 14.3% selectivities, but it did raise the alkenes selectivity to the extent
on Zn/HZSM-5). As Zn-LAS promoted more P aromatization, less that it reversed the alkanes and the alkenes selectivities. The
Table 4 Product distribution, acid sites distribution and C4-HTI
Amount of acid
Selectivity (wt%)
Aromatics
sites (mmol gꢁ1
)
External acid
sites (%)
Catalyst
BTX
A9+
Alkanes
Alkenes
LAS
BAS
C4-HTI
HZSM-5
1 wt% Zn/HZSM-5
35.3
48.4
27.8
38.3
7.5
10.1
51.4
33.0
4.9
6.1
20
108
280
123
28
25
0.86
0.81
Table 5 Product distribution, acid sites distribution and C4-HTI
Amount of acid
sites (mmol gꢁ1
Selectivity (wt%)
)
External acid
sites (%)
Catalyst
Aromatics
BTX
A9+
Alkanes
Alkenes
LAS
BAS
C4-HTI
HZSM-5
Si/HZSM-5
35.3
31.0
27.8
29.6
7.5
1.4
51.4
33.8
4.9
22.0
20
16
280
144
28
6
0.86
0.52
Table 6 Product distribution, acid sites distribution and C4-HTI
Amount of
acid sites
Selectivity (wt%)
(mmol gꢁ1
)
External acid
sites (%)
Catalyst
Aromatics
BTX
A9+
Alkanes
Alkenes
LAS
BAS
C4-HTI
Si/HZSM-5
1 wt% Zn/Si/HZSM-5
1.5 wt% Zn/Si/HZSM-5
31.0
30.1
32.5
29.6
28.5
30.7
1.4
1.6
1.8
33.8
21.2
14.7
22.0
35.6
38.7
16
52
59
144
106
88
6
3
5
0.52
0.27
0.18
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of methanol. As can be seen in Fig. 8, lower ow rates in the
range of 0.8 WHSV favored the conversion of alkenes to
aromatics via aromatization reaction and to alkanes via
hydrogen transfer. On the other hand, higher WHSV seemed to
hinder most signicantly the hydrogen transfer reaction and
more modestly the aromatization reaction, leading to a higher
alkenes selectivity. Consequently, the P/BT molar ratio could be
tuned over a range from 0.4 to 1.7 using the 1.5 wt% Zn/Si/
ꢀ
HZSM-5 catalyst at 0.1 MPa and 430 C (Fig. 9). A P/BT molar
ratio of 1.1 was achieved at a WHSV of 1.2 hꢁ1. The combined
selectivity of BTp-X and alkenes was 66.26 wt%. The combined
selectivities of m-X, o-X, A9+ and alkanes were only 16.8 wt%.
4. Conclusion
This work investigated a series of catalysts, including HZSM-5,
Si/HZSM-5, Zn/HZSM-5, and Zn/Si/HZSM-5 for a novel nonpe-
troleum route of methanol to phenol. It was found that the
catalyst of 1.5 wt% Zn/Si/HZSM-5 was capable of converting
methanol to a main product stream having a P/BT molar ratio of
unity, which would be an ideal feedstock for the manufacturing
of phenol. The catalytic conversion also produced such rela-
tively high-value byproducts as p-X and alkenes.
HZSM-5 produced mainly alkanes and aromatics, with the
alkanes selectivity being much higher than the aromatics selec-
tivity. The high alkanes selectivity probably was due to hydrogen
transfer promoted by the large quantity of BAS found on HZSM-5.
Impregnating Zn on HZSM-5 reduced BAS substantially, but
increased LAS also substantially. Alkanes and aromatics were
still the main products, however, the aromatics selectivity had
become much higher than the alkanes selectivity. The newly
created Zn-LAS appeared to be promoting aromatization more
strongly than promoting hydrogen transfer. Although the Zn/
Fig. 8 Effect of WHSV on the product selectivity over 1.5 wt% Zn/Si/
HZSM-5. Reaction conditions: 0.1 MPa, 430 ꢀC, the data were obtained
at 1 h.
increase of alkenes appeared to be due to the reduction of
hydrogen transfer as reected by the corresponding reduction
in alkanes selectivity and C4-HTI, which could all be traced back
to the decrease of the BAS. On the other hand, although the
amount of LAS were increasing, the extent of increasing seemed
to be insufficient to raise the aromatics selectivity. The Zn/Si/
HZSM-5 catalysts had turned the systems into an alkenes-rich
environment, but stopped short of converting these alkenes to
aromatics, implying that the catalysts probably did not have the
needed acidic sites to carry out more aromatization.
3.4 Effect of WHSV on the product distribution
The effect of WHSV on product distribution is shown in Fig. 8. It HZSM-5 catalyst produced more aromatics, a good fraction of
appears that product distribution was sensitive to the owrate the aromatics were the relatively low-valued m-X, o-X, and A9+.
Fig. 9 Effect of WHSV on (a) B, T and P selectivity. (b) P/BT molar ratio. Reaction conditions; 0.1 MPa, 430 ꢀC, the data were obtained at 1 h.
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Silica deposition on HZSM-5 reduced BAS signicantly. The without sacricing the selectivities of B, T, and p-X. The exact
majority of the reduction belonged to the BAS outside the control of selectivity can be achieved by adjusting WHSV. Thus,
zeolitic pores. Such passivation of external BAS appeared to do a P/BT molar ratio of near 1 along with good alkenes selectivity
two shiings, including a shiing of alkanes to alkenes and P, (34.5 wt%), high p-X selectivity (11.1 wt%) and purity (97.8 wt%)
ꢁ1
ꢀ
and a shiing amongst aromatics, in which the unwanted m-X, were achieved simultaneously at 0.1 MPa, 430 C and 1.2 h
o-X, and A9+ were suppressed and the desired p-X and T were WHSV on 1.5 wt% Zn/Si/HZSM-5.
produced.
Silica deposition, zinc impregnation, proper acidity adjust-
Impregnating Zn on Si/HZSM-5 reduced BAS further and ment, and process conditions were all essential for generating
created some LAS, with the net effects of decreasing total acid a product stream having a P/BT molar ratio of unity for the novel
sites with increasing Zn loading. Such levels of catalyst acidity methanol to phenol process along with such high-value
enabled the Zn/Si/HZSM-5 catalysts to increase P selectivity byproducts as p-X and alkenes.
Appendix
Table 7 Catalytic performance of Si/HZSM-5, Zn/HZSM-5, and Zn/Si/HZSM-5 catalysts
P/BT
Aromatics
(wt%)
B
T
X
p-X/X
P
Alkenes Alkanes (Molar Reaction
Sample
time (h) Ref.
Catalysts
(wt%) (wt%) (wt%) (wt%) (wt%) (wt%)
(wt%)
ratio)
condition
Zn-
5 wt% Zn/HZSM- 56.6 (36.3) 2.0
(2.3)
Al2O3¼ 38)
17.7
24.4
24.2
2.2
5.4 (2.9) 23.3
0.2
(0.2)
420 ꢀC, 0.1 MPa,
weight hourly
space velocity
(WHSV) ¼ 2.1
hꢁ1, N2 ow rate
¼ 30 ml minꢁ1
4
9
modied 5, (HZSM-5 SiO2/
HZSM-5
catalysts
(12.0) (13.9) (23.7) (1.2)
(43.7)
1.5wt% Zn/
HZSM-5, (HZSM-
5 SiO2/Al2O3 ¼
38)
50.9 (27.7) 2.3
(2.8)
9.5
(8.6)
26.9
72.4
4.8
11.5
(7.5)
14.3
(41.0)
0.9
(0.7)
475 ꢀC, 0.1 MPa, 2.25
10
11
(10.0) (69.5) (3.6)
WHSV¼ 1 hꢁ1
,
N2 ow rate ¼
30.8 ml minꢁ1
450 ꢀC, 0.1 MPa, 12
WHSV ¼ not
1 wt% Zn/HZSM- 49.5 (24.8) 4.0
17.8
(6.7)
21.1
(11.7)
n.a.
14.4
(22.1) (39.5)
31.1
10.3
1.4
(5.6)
5, HZSM-5 SiO2/
(1.6)
(27.9)
Al2O3 ¼ 60)
given, N2 ow
rate ¼ 88
ml minꢁ1
1 wt% Zn/HZSM- 65.9 (38.4) 4.9
14.9
(5.6)
25.9
24.1
2.1
4.6 (5.4) 26.0
0.2
(0.6)
460 ꢀC, 0.1 MPa, 0.5
13
13
16
5, (HZSM-5 SiO2/
(2.1)
(14.1) (23.5) (2.3)
(48.8)
WHSV ¼ 1 hꢁ1
,
Al2O3 ¼ 30)
N2 ow rate ¼ 80
ml minꢁ1
Silica
SiO2/HZSM-5
33.8 (38.4) 8.3
(2.1)
10.2
(5.6)
12.8
97.3
4.3
8.9 (5.4) 49.7
0.5
(0.6)
460 ꢀC, 0.1 MPa, 0.5
deposited (HZSM-5 SiO2/
HZSM-5
catalysts
(14.1) (23.5) (2.3)
(48.8)
WHSV ¼ 1 hꢁ1
,
Al2O3 ¼ 30)
N2 ow rate ¼ 80
ml minꢁ1
SiO2/HZSM-5,
(HZSM-5 SiO2/
Al2O3 ¼ 50)
27.4 (37.5) 7.0
(7.9)
8.9
(9.5)
9.5
98.1
14.0
36.3
(2.3)
34.4
(59.5)
1.8
(0.1)
400 ꢀC, 0.1 MPa, 0.5
(12.5) (24.0) (0.7)
WHSV ¼ 1 hꢁ1
,
N2 ow rate ¼ 40
SiO2/HZSM-5,
(HZSM-5 SiO2/
Al2O3 ¼ 200)
0.73 wt% Zn/
23.1 (35.4) 5.9
(8.3)
7.0
(9.8)
8.8
96.3
28.2
55.4
18.3
4.4
(0.7)
ml minꢁ1
(12.3) (24.2) (6.5)
(11.9)
(50.7)
Zn-
36.6 (27.4) 0.8
(1.2)
11.0
(8.1)
18.8
(12.9) (93.2)
94.8
n.a.
n.a.
n.a.
n.a.
450 ꢀC, 0.1 MPa,
2
12
13
14
modied HZSM-5/SiO2,
Si/
HZSM-5
WHSV ¼ 2.3 hꢁ1
(Si/HZSM-5 SiO2/
Al2O3 ¼ 28)
1 wt% Zn/Si/
HZSM-5, (Si/
HZSM-5 SiO2/
Al2O3 ¼ 30)
59.8 (33.8) 14.2
(8.3)
18.6
22.7
97.8
3.4
6.7 (8.9) 27.7
(49.7)
0.2
(0.5)
460 ꢀC, 0.1 MPa, 0.5
(10.2) (12.8) (97.3) (4.3)
WHSV ¼ 1 hꢁ1
,
N2 ow rate ¼ 80
ml minꢁ1
3 wt% ZnO/Si/
HZSM-5 (Si/
HZSM-5 SiO2/
Al2O3 ¼ 25)
28 (n.a.)
n.a.
n.a.
n.a
86.6
(n.a.) (n.a.)
8.8
n.a.
n.a.
n.a.
475 ꢀC, 0.1 MPa, 0.5
WHSV ¼ 0.79
hꢁ1
The methanol conversion is ꢃ100% over all these catalysts.
23874 | RSC Adv., 2019, 9, 23864–23875
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11 M. Conte, J. A. Lopez-Sanchez, Q. He, D. J. Morgan,
Y. Ryabenkova, J. K. Bartley, A. F. Carley, S. H. Taylor,
C. J. Kiely and K. Khalid, Catal. Sci. Technol., 2012, 2, 105–
112.
Conflicts of interest
There are no conicts to declare.
12 D. Pan, X. Song, X. Yang, L. Gao, R. Wei, J. Zhang and
G. Xiao, Appl. Catal., A, 2018, 557, 15–24.
Acknowledgements
13 J. Li, K. Tong, Z. Xi, Y. Yuan, Z. Hu and Z. Zhu, Catal. Sci.
Technol., 2016, 6, 4802–4813.
14 Q. Hu, X. Huang, Y. Cui, T. Luo, X. Tang, T. Wang, W. Qian
and F. Wei, RSC Adv., 2017, 7, 28940–28944.
This work was nancially supported by a ChangChun Group,
Taiwan and the Ministry of Science and Technology (MOST 104-
2622-8-007-001).
15 L. Sun, Y. Wang, H. Chen, C. Sun, F. Meng, F. Gao and
X. Wang, Catal. Today, 2018, 316, 91–98.
16 J. Li, Y. Wang, W. Jia, Z. Xi, H. Chen, Z. Zhu and Z. Hu, J.
Energy Chem., 2014, 23, 771–780.
17 A. F. Silva, A. Fernandes, P. Neves, M. M. Antunes,
S. M. Rocha, M. F. Ribeiro, C. M. Silva and A. A. Valente,
ChemCatChem, 2018, 10, 2741–2754.
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