Synthesis of Value-Added Chemicals via Oxidative Coupling of Methanes over Na2WO4-TiO2-MnO x /SiO2 Catalysts with Alkali or Alkali Earth Oxide Additives

Phattaradit Kidamorn; Worapinit Tiyatha; Thanaphat Chukeaw; Chalida Niamnuy; Metta Chareonpanich; Hiesang Sohn; Anusorn Seubsai

doi:10.1021/acsomega.0c00537

Synthesis of Value-Added Chemicals via Oxidative Coupling of Methanes over Na₂WO₄-TiO₂-MnO _x /SiO₂ Catalysts with Alkali or Alkali Earth Oxide Additives

ACS Omega. 2020 Jun 5;5(23):13612-13620. doi: 10.1021/acsomega.0c00537. eCollection 2020 Jun 16.

Authors

Phattaradit Kidamorn¹, Worapinit Tiyatha¹, Thanaphat Chukeaw^{1

2}, Chalida Niamnuy^{1

3}, Metta Chareonpanich^{1

2

3}, Hiesang Sohn⁴, Anusorn Seubsai^{1

2

3}

Affiliations

¹ Department of Chemical Engineering, Faculty of Engineering, Kasetsart University, Bangkok 10900, Thailand.
² Center of Excellence on Petrochemical and Materials Technology, Kasetsart University, Bangkok 10900, Thailand.
³ Research Network of NANOTEC-KU on NanoCatalysts and NanoMaterials for Sustainable Energy and Environment, Kasetsart University, Bangkok 10900, Thailand.
⁴ Department of Chemical Engineering, Kwangwoon University, 20 Kwangwoon-Ro, Nowon-Gu, Seoul 01897, Korea.

Abstract

Na₂WO₄-TiO₂-MnO _x /SiO₂ (SM) catalysts with alkali (Li, K, Rb, Cs) or alkali earth (Mg, Ca, Sr, Ba) oxide additives, which were prepared using incipient wetness impregnation, were investigated for oxidative coupling of methane (OCM) to value-added hydrocarbons (C₂₊). A screening test that was performed on the catalysts revealed that SM with Sr (SM-Sr) had the highest yield of C₂₊. X-ray photoelectron spectroscopy analyses indicated that the catalysts with a relatively low binding energy of W 4f_7/2 facilitated a high CH₄ conversion. A combination of crystalline MnTiO₃, Mn₂O₃, α-cristobalite, Na₂WO₄, and TiO₂ phases was identified as an essential component for a remarkable improvement in the activity of the catalysts in the OCM reaction. In attempts to optimize the C₂₊ yield, 0.25 wt % Sr onto SM-Sr achieved the highest C₂₊ yield at 22.9% with a 62.5% C₂₊ selectivity and a 36.6% CH₄ conversion. A stability test of the optimal catalyst showed that after 24 h of testing, its activity decreased by 18.7%.