In addition to H2O, CO2 can also acts as oxidant to reform ethanol to generate gaseous products. The reaction involved in this process is depicted in Reaction (2).

C2HsOH(l) + CO2 3 H2 + 3 CO (AHr,298K = 338 kJ/mol) (2)

Compared to Reaction (1), although only 3 moles of hydrogen are produced per mole of ethanol by using dry reforming process, it is still a valuable approach to utilize CO2 for hydrogen or syngas production beneficial for reducing greenhouse gas emission. The process feasibility and optimal operation parameters have been investigated by W. Wang, et al. thermodynamically, which is valuable for desirable product yield maximization. According to the calculations performed in [22], higher temperature, lower pressure, addition of inert gas, and lower CO2 to ethanol ratio benefit the improvement of hydrogen yield. Several catalysts such as Ni/ Al2O3 [23] and Rh/ CeO2 [24] have been developed in recent years for hydrogen or syngas production. Generally speaking, CO2 is less active than water in oxidizing ethanol. Therefore, more active catalysts are critical for making ethanol dry reforming more attractive to industrial investors. Similarly to methane dry reforming, coke can be formed with high possbility at certain reaction conditions on the catalyst surface, resulting in catalyst deactivation. Carbon tends to form at low temperature and low CO2/ethanol ratio based on thermodynamic prediction, which should be avoided to prevent catalyst deactivation. However, sometimes as a preferable byproducts, production of various types of carbon nanofilaments is desired by following Reaction (3), which has been found to be effectively catalyzed by stainless steel or carbon steel catalysts [25, 26].

C2H5OH(i) + CO2 2 H2 + 2 CO + 2 C +H2O(i) (AH^98K = 163 kJ/mol) (3)