Issue 12, 2020

Boric acid treated HZSM-5 for improved catalyst activity in non-oxidative methane dehydroaromatization

Abstract

The dehydroaromatization (DHA) reaction of methane under non-oxidative conditions is carried out over a molybdenum catalyst supported on HZSM-5 and boric acid (BA) treated HZSM-5 at 700 °C and atmospheric pressure. As compared to the conventional Mo/HZSM-5 catalyst, wherein a maximum of 100 nmol gcat−1 s−1 of benzene is measured, BA treated Mo/HZSM-5 exhibited a significantly high benzene formation rate (∼420 nmol gcat−1 s−1) at around 90 minutes time on stream. In addition, a boron treated catalyst was measured to have an 8 wt% reduction in coke formation as compared to the untreated catalyst. One prevailing thought for improved activity is ascribed to the desired moderation of Brønsted acid sites on BA treatment. This is probed by temperature programmed desorption (TPD) experiments which indicated an overall reduction in Brønsted acidity on BA treatment of the catalyst. Quantum mechanical density functional theory (DFT) calculations further estimated a high deprotonation energy (DPE) of the Brønsted acidic proton anchored on the boron substituted site (DPE = 1145.4 kJ mol−1) as compared to the Al site (DPE = 1100.6 kJ mol−1) of the zeolite framework, suggesting a reduction in Brønsted acidity. FTIR and 11B MAS NMR spectra confirmed the presence of trigonal boron species substituted in the zeolite framework. In addition, the molybdenum oxide (Mo6+) species, which is known to act as the precursor for active sites in methane DHA, is observed to form in a relatively greater quantity on the boron treated catalyst in the temperature program reduction (TPR) study of the calcined catalysts. Thus, BA treatment moderates the acidity of the Mo/HZSM-5 catalyst to provide the desired active sites for high reactivity.

Graphical abstract: Boric acid treated HZSM-5 for improved catalyst activity in non-oxidative methane dehydroaromatization

Supplementary files

Article information

Article type
Paper
Submitted
13 Feb 2020
Accepted
12 Mar 2020
First published
13 Mar 2020

Catal. Sci. Technol., 2020,10, 3857-3867

Boric acid treated HZSM-5 for improved catalyst activity in non-oxidative methane dehydroaromatization

S. Balyan, M. A. Haider, T. S. Khan and K. K. Pant, Catal. Sci. Technol., 2020, 10, 3857 DOI: 10.1039/D0CY00286K

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements