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pears, and that of the Si(2Al) units diminishes remarkably,
whereas the proportion of the Si(0Al) units dramatically in-
creases. The FSAR of USY prepared by conventional steaming
dealumination is very similar to that of CDY-wash, but it exhib-
its different relative intensities of the Si(nAl) units (Figure 3c).
During the dealumination, the next nearest neighbor alumi-
num atoms in four-membered rings (NNN-Al) are more easily
removed than isolated aluminum atoms with no neighbor alu-
minum atoms (0-NNN-Al).[16] The removal of NNN-Al affirma-
tively results in a decreased amount of Si(nAl) (nꢁ2) units,
whereas removal of 0-NNN-Al has a much lower chance of re-
ducing these Al-rich units.[16c] If different dealumination meth-
ods remove the same amount of FAL, the one with the higher
selectivity for removal of NNN-Al may contain fewer Si(nAl)
(nꢁ2) units.[16c] Here, the proportion of Si(2Al) in CDY-wash is
lower than that in USY, the reason for which may lie in the
more selective removal of NNN-Al by the aluminum sulfate as-
sisted dealumination approach. Lónyi and Evmiridis also inde-
pendently reported that hydrothermal dealumination is less se-
lective in removing NNN-Al in Y zeolite.[17]
To determine if the properties of stabilized Y are adequate
for its practical use as a FCC catalyst, it must be tested after
severe steam treatment.[14,19] After hydrothermally treatment
with 100% steam at 8008C for 17 h, the crystalline structure of
HY completely collapses, but that of two dealuminated Y zeo-
lites are well preserved (Figure S8). After steaming, CDY-wash
and USY possess similar RC of Y zeolite (46–55%), and they
maintain a high external surface area (127 and 48 m2 gÀ1, re-
spectively). This verifies that aluminum sulfate assisted dealu-
mination is highly effective as conventional steaming for stabi-
lizing the framework of Y zeolite.
The two steamed dealuminated Y zeolites demonstrate
Si(0Al) as the only building unit (Figure S9), and the number of
strong and weak acid sites in their structures is extremely low
as a result of the deep dealumination of FAL. As they both
show almost no activity in n-hexane cracking at 4008C, their
catalyst activity was thus tested in the cracking of 1,3,5-triiso-
propylbenzene (TIPB) (Table S4). Steamed CDY-wash shows
a TIPB conversion of 33.4% and a diisopropylbenzene (DIPB)
yield of 16.4 wt%, the values of which are higher than those of
steamed USY (27.0% and 12.0 wt%, respectively). The yields of
benzene and cumene are similar for these two steamed cata-
lysts. TIPB with a kinetic diameter of 9.4 is larger than the
window opening of the microspores of Y zeolite,[20] which first
needs cracking on the external surface of the zeolite crystals
and/or matrix-like alumina. Thus, the slightly higher cracking
ability of steam CDY-wash can probably be attributed to co-ex-
isting g-alumina.[21] According to these results, steamed CDY-
wash is expected to possess higher activity for the conversion
of long-chain hydrocarbons into smaller, more useful
hydrocarbons.
The acid strength of zeolites closely depends on NNN-Al,
and removal of NNN-Al will increase the strong acid sites of
Y zeolite.[16b] The acidic properties of the proton-type samples
(i.e., HCDY-wash, HUSY, and HY) were investigated by the tem-
perature-programmed desorption of ammonia (NH3-TPD) tech-
nique and IR spectroscopy analysis of the pyridine adsorption
band (Figures S6 and S7 and Table S2). The samples possess
both Brønsted acid sites and Lewis acid sites. HCDY-wash and
HUSY have more strong acid sites than HY, probably because
of extensive dealumination and removal of NNN-Al.[16c] On the
other hand, HCDY-wash possesses 22% more strong acid sites
than HUSY, though they have comparable FSARs, and HUSY
has a higher microspore volume. This difference is presumably
ascribed to the greater amount of 0-NNN-Al units contained in
HCDY-wash.
We further investigated the practicality of using CDY as
a FCC catalyst by comparing it to a commercial catalyst under
reaction conditions close to the industrial process. HCDY-wash
and HUSY were dry sprayed by mixing with kaolin clay and
silica sol to prepare microsphere catalysts, which were further
loaded with a poisoning metal (V and Ni) and steam aged at
8008C for 17 h, which allowed the catalysts to experience the
severe conditions in the actual processes. The XRD patterns
and SEM images verify that the microsphere catalysts obtained
are of good quality (Figures S10 and S11). The 20 wt% sprayed
catalyst was blended with a Sinopec ShengLi FCC catalyst. The
catalytic cracking performance was checked with a FCC micro-
activity testing unit (ACE Models R+MM) with Sinopec heavy
vacuum oil as feedstock (Table S5). Detailed heavy oil cracking
activities and product selectivities are shown in Table 2. The
The stronger acid strength is helpful in giving a longer kinet-
ic chain length, faster chain propagation, and higher overall
rates for zeolite-processed reactions. HY, HCDY-wash, and
HUSY were tested for the catalytic cracking of n-hexane at
4008C (Table S3). HCDY-wash exhibits a n-hexane conversion of
14.8% and a hydrogen transfer index (HTI) of 4.3;[18] both
values are higher than the corresponding values of HY (8.6%
conversion and HTI of 3.4) and those of HUSY (12.4% conver-
sion and HTI of 3.7). This difference is in agreement with the
order of strong acid sites for these three catalysts.
Table 2. Heavy oil cracking activity and selectivities.
Catalyst[a]
Conversion[b] Dry gas LPG
[wt%] [wt%] [wt%] [wt%]
Gasoline Diesel Bottoms Coke RON MON (RON+MON)/2
[wt%] [wt%]
[wt%]
ShengLi
77.1
1.8
1.9
1.9
16.5 47.9
16.6 49.2
16.7 48.2
14.2 8.7
13.1 8.1
13.5 8.5
10.9 92.4 83.4 87.9
11.1 92.7 84.0 88.3
11.2 93.1 84.2 88.6
sprayed HCDY-wash[c] 78.8
80% ShengLi+20% sprayed catalyst
sprayed HUSY[c]
78.0
[a] Catalyst performance time: catalyst/oil=8, time on stream: 90 s, reaction temperature: 5008C. [b] Conversion is defined as the sum of dry gas, LPG, gas-
oline, and coke. [c] The sprayed catalyst was loaded 1500 ppmV and 3000 ppm Ni, calcined at 8008C in 100% steam for 17 h.
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