Acetic Acid Leaching on the Structure, Acidity and Performance of HMOR Catalyst

doi:10.15541/jim20180220

Abstract

Abstract:

Acid sites located inside the 8-ring side-pockets of mordenite are highly active for DME carbonylation. However, mordenite deactivates very fast during the reaction because of non-selective reactions happening inside the 12-ring main channels of zeolites. In the present study, HMOR was treated by acid leaching using acetic acid of different concentration, with the purpose to selectively remove framework Al which is located inside 12-ring channels. Physicochemical characteristics of the parent and acid-treated mordenites were studied by complementary methods including: XRD, ²⁷Al-NMR, NH₃-TPD, pyridine IR, and N₂ adsorption-desorption. The results show that the acid treatment, if appropriately applied, increases both the Si/Al and micropore volume of the samples, without significantly changing the mesopore size distribution. Most of the framework Al species in the 12-membered ring channels of HMOR were removed, without impacting those located inside the 8-ring channels. The catalytic results show that the initial activity of catalyst decreased slightly from 45.6% to 43.8%. On the other hand, the activity stability improved substantially, with stabilization period prolonged obviously from 18 h to 50 h.

Key words: DME carbonylation, acid treatment, dealumination, pore size distribution

CLC Number:

O643

HAN Hai-Bo, WANG You-He, LI Kang, LEI Jie, LIU Dan-He, YAN Zi-Feng. Acetic Acid Leaching on the Structure, Acidity and Performance of HMOR Catalyst[J]. Journal of Inorganic Materials, 2019, 34(2): 179-185.

Figures/Tables 10

Fig. 1 XRD patterns of HMOR zeolites treated with different concentrations of acetic acid

Table 1 Relative crystallinity and Si/Al of HMOR zeolites treated with different concentrations of acetic acid

Sample	AC00	AC01	AC02	AC03
n(Si)/n(Al)	10.2	12.3	13.6	15.2
Crystallinity/%	100	99	97	95

Fig. 2 27Al-NMR spectra of HMOR zeolites treated with different concentrations of acetic acid

Fig. 3 Acidity properties of HMOR zeolites treated with different concentrations of acetic acid (a) NH3-TPD; (b) FT-IR

Table 2 Properties of B acid sites in different channels of HMOR zeolites treated with different concentrations of acetic acid

Sample	B_framework /(μmol•g^-1)	B_12-MR /(μmol•g^-1)	B_8-MR /(μmol•g^-1)
AC00	898.1	436.3	461.8
AC01	780.2	322.5	457.7
AC02	668.8	225.3	443.5
AC03	591.6	170.4	421.2

Fig. 4 N2 adsorption-desorption isotherms and pore diameter distribution of HMOR zeolites treated with different concentrations of acetic acid

Table 3 Textural and structural properties of HMOR zeolites treated with different concentration of acetic acid

Samples	AC00	AC01	AC02	AC03
S_BET/(m²•g^-1)	477	476	455	449
S_mic/(m²•g^-1)	422	416	386	387
S_ext/(m²•g^-1)	55	60	69	62
V_total/(cm³•g^-1)	0.28	0.28	0.28	0.27
V_micro/(cm³•g^-1)	0.18	0.18	0.19	0.19
Median pore diameter/nm	0.59	0.60	0.61	0.62
Micropore distribution /(cm³•g^-1)
<0.6/nm	0.066	0.071	0.076	0.081
0.6-0.7/nm	0.029	0.027	0.021	0.020
0.7-1.2/nm	0.032	0.037	0.043	0.044

Fig. 5 H-K cumulative pore volume of HMOR zeolites treated with different concentrations of acetic acid

Fig. 6 H-K differential pore volume of HMOR zeolites treated with different concentrations of acetic acid

Fig. 7 Inactivation curves of HMOR zeolites treated with different concentrations of acetic acid

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