Dynamics of carbon formation during the catalytic hydrodeoxygenation of raw bio-oil

Abstract

The formation, growth and transformation of carbon residue (coke) deposited on the catalyst during the raw bio-oil hydrodeoxygenation has been studied.

A Hybrid FCC/HZSM-5 Catalyst for the Catalytic Cracking of a VGO/Bio-Oil Blend in FCC Conditions

“…These results indicate that the formation of carbon products in the volatiles is hindered by higher cracking temperatures, which simultaneously favor the formation of coke deposits on the catalyst. It should be mentioned that despite the issues that arise in bio-oil valorization processes from the rapid repolymerization of phenolics and the formation of the so-called thermal lignin [13], no operational issues derived from coke formation were observed in this study. This can be explained by the elevated cracking temperatures of this study and the fast kinetics of the reactions taking place.…”

“…Despite its low N and S content, direct application of bio-oil as a fuel is limited due to its high oxygen and water content, low calorific power, viscosity (10-100 cP at 40 • C), acidity (pH ≈ 2-4), corrosive nature, and low chemical stability upon storage, among others [8,9]. For these reasons, prior to its valorization, it is also plausible to stabilize the bio-oil by removing some of the more unstable oxygenates through the addition of a solvent [10], thermal aging [11], or some catalytic treatment (i.e., esterification, mild hydrodeoxygenation) [12,13]. Nonetheless, these pre-treatments might be costly and can also potentially decrease the yields of interesting products in subsequent catalytic valorization stages, and hence, the interest for developing large-scale direct bio-oil conversion routes is reinforced.…”

In-Depth Analysis of Raw Bio-Oil and Its Hydrodeoxygenated Products for a Comprehensive Catalyst Performance Evaluation

“…Despite its intermediate coke content of 53.0 wt %, the PtPdHZ catalyst showed the highest CK/TL ratio of 5.5, which is 6–9 times higher than for the other two catalysts. The remarkably high total coke formation observed for the CoMoHZ catalyst can be explained from its lower HDO activity, which facilitates the enhancement of the coke formation mechanism from oxygenates. , In addition, this lower deoxygenation activity also prevents TL from further reacting toward the formation of more condensed CK, which forms in a great proportion in the case of the PtPdHZ catalyst, given its very high HDO activity.…”

“…The remarkably high total coke formation observed for the CoMoHZ catalyst can be explained from its lower HDO activity, which facilitates the enhancement of the coke formation mechanism from oxygenates. 38,53 In addition, this lower deoxygenation activity also prevents TL from further reacting towards the formation of more condensed CK, which forms in a great proportion in the case of the PtPdHZ catalyst, given its very high HDO activity. As previously mentioned, liquid carbon products consist of two different product phases, an organic and an aqueous one, each containing oxygenates and hydrocarbons.…”

“…A noticeable concentration of ketones of 23.7 % was also measured for the NiWHZ catalyst. The highest proportion of heavy oxygenates in the product from the CoMoHZ catalyst would reinforce the premise for a faster coke formation rate due to their repolymerization 53,54. A more detailed chemical composition of the carbon products for all the catalyst combinations is provided in TableS1.…”