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Kinetics, Catalysis, and Reaction Engineering
Dissolution equilibrium and in-situ growth of HMCM-49 in aqueous phase reaction Xinde Sun, Yingli Wang, Yanli He, Yue Yang, Shutao Xu, Shukui Zhu, Miao Yang, and Zhongmin Liu Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.9b01417 • Publication Date (Web): 10 May 2019 Downloaded from http://pubs.acs.org on May 10, 2019
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Industrial & Engineering Chemistry Research
Dissolution equilibrium and in-situ growth of HMCM-49 in aqueous phase reaction Xinde Sun*, Yingli Wang, Yanli He, Yue Yang, Shutao Xu, Shukui Zhu, Miao Yang, Zhongmin Liu* National Engineering Laboratory for Methanol to Olefins, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, PR China Corresponding Author
[email protected] (X. Sun),
[email protected] (Z. Liu).
Supporting Information Placeholder ABSTRACT: Insufficient stability of zeolite is one of the key challenges for application of zeolites in aqueous phase reactions. In long term catalytic tests on hydrolysis of ethylene glycol monomethyl ether to ethylene glycol, we found that dissolution of HMCM-49 catalysts could lead to complete transformation to kaolinite. Existence of dissolution equilibriums of Si and Al was demonstrated. In-situ growth of HMCM-49 occurred where Si concentration in bulk phase surpass equilibrium value. This almost completely prevented dissolution and phase transformation of HMCM-49. Dissolution of HZSM-5 catalyst was different. A method by dissolving Si and Al in feed is proposed to solve the problem of zeolite stability in aqueous phase reactions.
Zeolites are important and widely used catalytic materials. Recently, increasing attentions have been paid to zeolite catalyzed aqueous phase transformation of biomass which is one of current focuses.1-4 One of the key challenges is insufficient stability of zeolites in hot liquid water and aqueous phase reactions.1-21 The structural collapse was caused by desilication due to hydrolysis of terminal Si−OH groups2,5-10 with density of silanol defects as crucial factor7,11,12. Silylation treatment could improve stability of zeolite in hot liquid water 24,7,11,12 and aqueous phase reactions2,4,12. Both framework and extra-framework Al were found able to inhibit desilication.5-10,13,14 Presence of organic reactants showed protective effect against water.3 Bell et al. reported a new effective method to synthesize methyl methoxyacetate by vapor phase carbonylation of dimethoxymethane over zeolite catalyst.22 This promoted a new route of ethylene glycol (EG) synthesis from syngas for dimethoxymethane can be easily synthesized from methanol and formaldehyde and methyl methoxyacetate can be reduced directly to ethylene glycol monomethyl ether (EGME)22 which can convert to EG via hydrolysis over HMCM-4923 or HZSM-524. This paper found that dissolution of HMCM-49 catalyst was an equilibrium process and observed in-situ growth of HMCM-49 in 2342 hrs long term test on hydrolysis of EGME with a fixed bed reactor. The temperature profile of catalyst bed was a parabolic shape (Figure 1) in the long term test. Figure 2 shows conversion of EGME (X) and selectivity of EG (SEG). After 680 hr, TM (maximum of T profile) was raised to compensate loss of catalyst activity and accelerated deactivation was observed. SEG kept between 42% - 45%. Selectivity of products other than EG was as follows: ethylene glycol dimethyl ether ~32%, di-, tri- ethylene glycol and their mono-, di-methyl ethers ~4.3%, dioxane ~1.5%, methanol ~12.5%, dimethyl ether ~3.5%, ethylene epoxide ~0.3% and others ~1%.
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Industrial & Engineering Chemistry Research
220 200 180
O
T ( C)
160 140
o
Last stage (TM: 212 C)
120
o
Initial stage (TM: 190 C)
100 80 60
0
5
10
15
20
25
30
35
Height (cm, from inlet)
Figure 1. Temperature profiles at initial (TM 190 oC) and final (TM 212 oC) stage of long term catalytic test on EGME hydrolysis. A 48
194.5
o
X (%)
191 192.5
TM ( C): 190
44
200 196
208 204
212
40 36 32 0
400
800
1200
1600
2000
2400
2000
2400
Time on stream (hr)
B
48 46
SEG (%)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
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44 42 40
0
400
800
1200
1600
Time on stream (hr)
Figure 2. X (A) and SEG (B) of EGME hydrolysis. H2O/EGME 4 (mol/mol), LHSV 0.37 ml/gcat•h, P 2.0 MPa. Si and Al contents in effluent obtained by ICP analysis are listed in Table 1. Si content increased with temperature. Al content was hundreds times lower than Si and showed no evident relation with temperature. Total amount of Si and Al in the whole effluent was calculated showing that 32% Si and only 0.17% Al dissolved away from the HMCM-49 catalyst. This prevailing dissolution of Si over Al was consistent with reports that both framework and extra-framework Al were able to inhibit desilication in hot liquid water5-10,13,14. The total dissolved Al was only ~1% of the framework Al in HMCM-49. So, contribution of Al dissolution to deactivation was negligible even if it came from framework Al solely.
Table 1. Si and Al contents in effluents Time on stream (hr)
TM
Toutlet
(℃)
(℃)
Si* (mg/l)
Al* (mg/l)
48 - 56
190
170
93
0.35
277 - 349
190
170
105
0.38
613 - 685
190
170
105
0.35
960 - 1039
192.5
172
107
0.36
1416 - 1495
194.5
174
112
0.30
1663 - 1759
200
179
119
0.38
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204
183
127
0.41
2073 - 2145
208
186
124
0.37
2337 - 2342
212
190
124
0.32
*
: Relative error, ±10%
The catalyst after test was separated into 8 samples (denoted as A - H, from inlet to outlet). Table 2 shows their results of characterization and catalytic test.
Table 2. Characterization results of HMCM-49 catalyst after test Sample
Tinitial (oC)
Si/Al (mol)
Si Loss (%)
Cryl. (%)
X* (%)
kr**/ Cryl.
Fresh
/
1.68
/
100
21.9
100
A
64-150
0.57
66
34
1.7
21
B
150-176
0.57
66
20
0.9
18
C
176-185
0.94
44
