TY - JOUR
T1 - Ti-doped γ-Al 2 O 3 versus ZSM5 zeolites for methanol to dimethyl ether conversion
T2 - In-situ DRIFTS investigation of surface interactions and reaction mechanism
AU - Khaleel, Abbas
AU - Ahmed, Mo'ath
AU - Sowaid, Salem Ba
N1 - Funding Information:
This work was financially supported by Emirates Center for Energy and Environment Research (ECEER) at UAEU , grant No. ECEER-01/15/02/14 .
Publisher Copyright:
© 2019 Elsevier B.V.
PY - 2019/6/20
Y1 - 2019/6/20
N2 - Solid acids are promising catalytic materials for the dehydration of methanol vapor to dimethyl ether, which has recently been recognized as an ultraclean environmentally friendly fuel. In the present work, methanol conversion to dimethyl ether was studied on the surface of Ti(IV)-doped γ-Al 2 O 3 and over selected ZSM5 zeolites aiming at understanding the possible effect of the Ti ions, and to compare between the possible mechanisms over the studied catalyst surfaces. Doping γ-Al 2 O 3 with Ti resulted in modified textural properties and an enhanced overall surface acidity. In-situ DRIFTS study of adsorption showed that the presence of Ti resulted in the formation of more acidic hydroxyl groups on the surface leading to an enhanced adsorption of methanol and conversion to dimethyl ether. Comparison between the studied alumina-based solids and ZSM5 zeolites showed that the acidic character of their surface OH groups varied and therefore, different routes of methanol reaction were proposed for the two types of materials. Methanol adsorption was proposed to be associative on the surface of ZSM5 zeolites, where Brønsted acid sites played a key role in the adsorption and dehydration reaction. On the other hand, dissociative adsorption on Lewis acid-base pairs dominates the interactions with γ-Al 2 O 3 -based solids.
AB - Solid acids are promising catalytic materials for the dehydration of methanol vapor to dimethyl ether, which has recently been recognized as an ultraclean environmentally friendly fuel. In the present work, methanol conversion to dimethyl ether was studied on the surface of Ti(IV)-doped γ-Al 2 O 3 and over selected ZSM5 zeolites aiming at understanding the possible effect of the Ti ions, and to compare between the possible mechanisms over the studied catalyst surfaces. Doping γ-Al 2 O 3 with Ti resulted in modified textural properties and an enhanced overall surface acidity. In-situ DRIFTS study of adsorption showed that the presence of Ti resulted in the formation of more acidic hydroxyl groups on the surface leading to an enhanced adsorption of methanol and conversion to dimethyl ether. Comparison between the studied alumina-based solids and ZSM5 zeolites showed that the acidic character of their surface OH groups varied and therefore, different routes of methanol reaction were proposed for the two types of materials. Methanol adsorption was proposed to be associative on the surface of ZSM5 zeolites, where Brønsted acid sites played a key role in the adsorption and dehydration reaction. On the other hand, dissociative adsorption on Lewis acid-base pairs dominates the interactions with γ-Al 2 O 3 -based solids.
KW - Catalytic activity
KW - In-situ-DRIFTS
KW - Surface acidity
KW - Surface adsorption
KW - Textural properties
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U2 - 10.1016/j.colsurfa.2019.03.052
DO - 10.1016/j.colsurfa.2019.03.052
M3 - Article
AN - SCOPUS:85064068305
SN - 0927-7757
VL - 571
SP - 174
EP - 181
JO - Colloids and Surfaces A: Physicochemical and Engineering Aspects
JF - Colloids and Surfaces A: Physicochemical and Engineering Aspects
ER -