545787 Effect of Ba Addition on the Catalytic Activity of Ga-Al2O3 for Ethane Dehydrogenation

Monday, June 3, 2019
Texas Ballroom Prefunction Area (Grand Hyatt San Antonio)
Yukiko Hosono1, Hikaru Saito1, Hirofumi Seki1, Shun Maeda2, Shuhei Ogo1, Kunihide Hashimoto2 and Yasushi Sekine1, (1)Applied Chem., Waseda Univ., Tokyo, Japan, (2)Kubota Corp., Hirakata, Japan

Steam cracking of ethane has been an attractive process because ethane got a cheap feedstock. However, this process is non-catalytic and energy-intensive because of high reaction temperatures (> 1073 K) and periodic decoking to remove carbonaceous deposit. Thus, introduction of dehydrogenation catalysts to the reactor is an effective way to lower the reaction temperature and suppress carbon deposition. In our previous study, Ga supported on α-Al2O3, which is a model of cracking tubes (AFTALLOY, Kubota Corp.), exhibited high ethylene yield at 973 K. In this study, we examined addition of second metals to Ga/α-Al2O3 to enhance the catalytic performance.
Ga-xM/α-Al2O3 catalysts were prepared by a co-impregnation method. Note that “M” and “x” denote a second metal and M/Ga molar ratio, respectively. Loading amount of Ga was controlled to be 5wt%. Catalytic activity for ethane dehydrogenation was evaluated in a fixed bed reactor at 973 K and atmospheric pressure. Ethane, water and balanced nitrogen (C2H6 : H2O : N2 = 1.0 : 1.4 : 5.5) were fed at a flow rate of 143 mL min-1.
From the results of activity tests, Ga-0.1Ba/α-Al2O3 exhibited the highest selectivity to ethylene (98%) although the activity of Ga-0.1Ba/α-Al2O3 was comparable to Ga/α-Al2O3. Selectivity to ethylene was improved thanks to the suppression of CO and CO2 formation. Originally, they are formed through oxidation of carbonaceous deposit by H2O. Temperature programmed oxidation revealed that the amount of carbon deposition on Ga-0.1Ba/α-Al2O3 was smaller than that on Ga/α-Al2O3. Then, the electronic state and coordination environment of Ga were measured by Ga K-edge X-ray absorption fine structure spectroscopy. As a result, a part of Ga might form Ga-Ba oxides although Ga mainly existed as β-Ga2O3. Therefore, coke formation would be suppressed because active sites of β-Ga2O3 for coke formation were poisoned by Ba addition.

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