Unique Lewis and Bronsted acidic sites texture in the selective production of tetrahydropyran and oxepanefrom1,5-pentanediol and 1,6-hexanediol over sustainable red brick clay catalyst

Venkata Rao Madduluri; Naresh Kumar Katari; Nagaiah Peddinti; Challa Prathap; David Raju Burri; Seetha Rama Rao Kamaraju; Sreekantha B Jonnalagadda

doi:10.1016/j.heliyon.2019.e01212

Unique Lewis and Bronsted acidic sites texture in the selective production of tetrahydropyran and oxepanefrom1,5-pentanediol and 1,6-hexanediol over sustainable red brick clay catalyst

Heliyon. 2019 Feb 13;5(2):e01212. doi: 10.1016/j.heliyon.2019.e01212. eCollection 2019 Feb.

Authors

Venkata Rao Madduluri¹, Naresh Kumar Katari^{2

3}, Nagaiah Peddinti¹, Challa Prathap¹, David Raju Burri¹, Seetha Rama Rao Kamaraju¹, Sreekantha B Jonnalagadda³

Affiliations

¹ Inorganic and Physical Chemistry Division, CSIR-Indian Institute of Chemical Technology, Hyderabad 500007, India.
² Department of Chemistry, GITAM School of Technology, GITAM Deemed to be University, HTP Campus, Rudraram, Medak, Telangana 502 329, India.
³ School of Chemistry & Physics, University of KwaZulu-Natal, P Bag X 54001, Durban 4000, South Africa.

Abstract

Activated red brick (ARB) clay material proved superb catalyst for selective conversion of 1,5-pentanediol (1,5-PDO) to tetrahydropyran (THP) and 1,6-hexanediol (1,6-HDO) to oxepane (OP) via dehydration under vapor phase conditions in a continuous flow reactor. As per scanning electron microscopy (SEM), SEM-EDX and X-ray fluorescence (XRF) techniques, ARB clay catalyst majorly possessed silica (quartz), and iron oxide (hematite) species, and synergistic texture contributed to the catalytic efficiency for prolonged time-on-stream (TOS). The combination of active Lewis and Bronsted acidic sites with weak to mild acidic nature in the ARB clay obviously facilitates the dehydration reaction with high selectivity, tetrahydropyran (82%) and oxepane (89%). ARB clay displayed superior catalytic properties in the dehydration of alcohols compared with activities of commercial silica and α-Fe₂O₃ as catalysts. Commercial silica and α-Fe₂O₃ catalysts possessing the Lewis acidic sites only did not facilitate synchronous dehydration mechanism.

Keywords: Inorganic chemistry; Materials chemistry; Physical chemistry.