Refinement of the kinetic model for guaiacol hydrodeoxygenation over platinum catalysts

Significance 

Climatic ramifications as a consequence of global fossil fuel over exploitation and related pollution have tilted the scale in favor of renewable energy resources. Additionally, high crude oil demand coupled with its diminishing reserves calls for alternative energy sources. To date various sources have been explored: i.e. biomass, solar, wind and hydrogen. With a focus on biomass; fast pyrolysis has emerged as a promising technology to obtain biofuels from various lignocellulosic materials. The resultant bio-oil contains relatively high oxygen content; however, it cannot be used as transportation fuels owing to poor stability, low heating value, and inferior combustion performance. The quest to circumvent this shortfall has shown that catalytic hydrodeoxygenation (HDO) can be used to upgrade pyrolysis-derived bio-oils. So far, two kinetics have been developed for guaiacol HDO. Further, measurement of catalytic kinetics in the laboratory involves the use of continuous flow fixed-bed reactors which can be operated in either the differential or the integral mode.

Guaiacol previously was used as the model compound of bio-oil with Pt/AC as the catalysts and under integral operating conditions; where the reaction kinetics were evaluated (Ind. Eng. Chem. Res. 2015, 54, 43, 10638–10644). To this end, researchers from the Davidson School of Chemical Engineering at Purdue University proposed to refine the prior kinetic model for the same reaction network over the same catalyst, but under differential operating conditions. Their work is currently published in the research journal, AIChE Journal .

In their approach, the platinum catalysts were prepared by the wet impregnation method similar to their prior work. The kinetic model was then developed where the power-law model was used to describe the relation between reaction rates and partial pressures of reactants. Overall, the reaction kinetic studies were undertaken under differential operating conditions (i.e., using a differential reactor).

The authors showed that among the five reaction steps in the network, the reaction order of one step differed from their prior work, while the orders remained unchanged for the other four steps. The team further reported that the activation energies of two steps differed from their prior values by 10–15 kJ/mol, and for the other three steps remained essentially consistent with their prior work. The team used the kinetic parameters from the present work to predict fixed-bed reactor performance under integral operating conditions as well.

In summary, the study presented the refinement of the kinetic model for the same reaction network (from prior study) over the same catalyst utilizing differential operating conditions. Remarkably, the comparison between experimental and predicted values for both the prior and new sets of data was excellent and even better than for their prior model. In a statement to Advances in Engineering, Dr. Yang Xiao, the corresponding author ([email protected]) emphasized that their study demonstrated that kinetic expressions and parameters obtained from a gradient-less differential reactor are more reliable and can be used to successfully predict integral reactor performance data.

Reference

Yang Xiao, Rexonni Lagare, Lindsey Blanshan, Enrico N. Martinez, Arvind Varma. Refinement of the kinetic model for guaiacol hydrodeoxygenation over platinum catalysts. AIChE Journal 2020; volume 66:e16913.

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