Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2023 Oct 26;16(21):6872.
doi: 10.3390/ma16216872.

Influence of the Mesoporosity of Hierarchical ZSM-5 in Toluene Alkylation by Methanol

Lucie Desmurs  1 , Claudia Cammarano  1 , Olinda Gimello  1 , Anne Galarneau  1 , Vasile Hulea  1
Affiliations

Influence of the Mesoporosity of Hierarchical ZSM-5 in Toluene Alkylation by Methanol

Lucie Desmurs et al. Materials (Basel). .

Abstract

Among the different strategies to design highly shape-selective ZSM-5 to obtain para-xylene through toluene alkylation with methanol, the introduction of mesopores to increase reactant and product diffusion has been proposed but barely studied. In this study, we prepared mesoporous ZSM-5 catalysts, named ZSM5-MT(x), from commercial ZSM-5 (Si/Al = 15), using a two-step micelle-templating procedure with octadecyltrimethylammonium bromide as a surfactant in basic medium (x = NaOH/Si). These materials were used as catalysts for the alkylation of toluene by methanol at a low contact time to avoid thermodynamic equilibrium of the xylene isomers. Compared to the parent ZSM-5, the mesoporous ZSM5-MT(x) catalysts did not improve the para-xylene selectivity, revealing that the strategy of increasing diffusion in the catalyst is not a good strategy to follow. However, ZSM5-MT(0.5) showed less deactivation on stream than the parent ZSM-5. Therefore, introducing mesopores to ZSM-5 could be interesting to explore, combined with another strategy of shape selectivity, such as the passivation of the external surface acidity.

Keywords: alkylation; hierarchical ZSM-5; methanol; para-xylene; toluene.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Scheme 1
Scheme 1
Main reactions involved in the alkylation of toluene by methanol. (1a) Toluene alkylation; (1b) xylene alkylation; (2) toluene disproportionation; (3) methanol to hydrocarbons; (4) xylene isomerization.
Scheme 2
Scheme 2
Stepwise mechanisms for methylation of toluene on zeolites with methanol (CH3OH): (i) adsorption of CH3OH on a Brønsted proton; (ii) dehydration of methanol; (iii) toluene methylation.
Figure 1
Figure 1
TEM images of parent ZSM-5 and ZSM5-MT(x). The red arrow indicates the presence of an Al-MCM-41- like phase.
Figure 2
Figure 2
Evolution of mesoporous volume and number of Brønsted acid sites in mesoporous ZSM5-MT(x) as a function of x = NaOH/Si molar ratio in gel synthesis.
Figure 3
Figure 3
Conversion of toluene and methanol, selectivity in xylenes, and TMB as a function of the number of Brønsted acid sites of the catalysts in the alkylation of toluene by methanol. Conditions: toluene/methanol = 4/1, 10 mg catalyst + 140 mg quartz, contact time = 0.03 s, T = 350 °C, TOS = 15 min. Catalysts: commercial ZSM-5 (Si/Al = 15) and hierarchical ZSM5-MT(x). The value of x is indicated next to the data points.
Figure 4
Figure 4
Turn over frequency (TOF) of toluene in the alkylation of toluene by methanol. Conditions: toluene/methanol = 4/1, 10 mg catalyst + 140 mg quartz, contact time = 0.03 s, T = 350 °C, TOS = 15 min. Catalysts: Commercial ZSM-5 Si/Al = 15 and hierarchical ZSM5-MT(x).
Figure 5
Figure 5
Selectivity in para-, meta-, ortho-xylenes as a function of the number of Brønsted acid sites of the catalysts in the alkylation of toluene by methanol. Conditions: toluene/methanol = 4/1, 10 mg catalyst + 140 mg quartz, contact time = 0.03 s, T = 350 °C, TOS = 15 min. Catalysts: commercial ZSM-5 Si/Al = 15 and hierarchical ZSM5-MT(x). The value of x is indicated under the data options.
Figure 6
Figure 6
Conversion of toluene as a function of time on stream (TOS) in the alkylation of toluene by methanol. Conditions: toluene/methanol = 4/1, 10 mg catalyst + 140 mg quartz, T = 350 °C, TOS = 15 min. Catalysts: commercial ZSM-5 Si/Al = 15 and hierarchical ZSM5-MT(0.5). The results with the other ZSM5-MT(x) are given in Figure S3.
See this image and copyright information in PMC

References

    1. Vermeiren W., Gilson J.P. Impact of Zeolites on the Petroleum and Petrochemical Industry. Top Catal. 2009;52:1131–1161. doi: 10.1007/s11244-009-9271-8. - DOI
    1. Martinez C., Corma A. Inorganic molecular sieves: Preparation, modification and industrial application in catalytic processes. Coord. Chem. Rev. 2011;255:1558–1580. doi: 10.1016/j.ccr.2011.03.014. - DOI
    1. Li Y., Yu J. Emerging applications of zeolites in catalysis, separation and host-guest assembly. Nat. Rev. Mater. 2021;6:1156–1174. doi: 10.1038/s41578-021-00347-3. - DOI
    1. Tanabe K., Holderich W. Industrial application of solid acid–base catalysts. Appl. Catal. A Gen. 1999;181:399–434. doi: 10.1016/S0926-860X(98)00397-4. - DOI
    1. Ahn J.H.J. PhD Thesis. Technische Universitat Munchen; Munich, Germany: 2013. Investigation into the Reaction of Toluene Methylation to P-Xylene over Acidic Zeolites.

LinkOut - more resources