Mild modification of lignin pyrolysis vapors by metal oxide catalysts: A comparative study with molecular sieve catalysts

ABSTRACT

Compared with strongly acidic molecular sieve catalysts, metal oxide catalysts are less prone to deactivation by coking due to their mild acid-base properties. Several metal oxides (Al₂O₃, MgO, CaO, CuO, Fe₂O₃, NiO, ZnO, ZrO₂, TiO₂ and CeO₂) were selected for mild catalytic pyrolysis of lignin and compared with molecular sieve catalysts (MCM-41, HZSM-5, ZSM-5). Among the metal oxide catalysts studied, CuO, Fe₂O₃ and TiO₂ inhibited the formation of acids/alcohols (1–2%) and promoted the production of hydrocarbons (15.31%, 20.17% and 28.83%, respectively). Especially when TiO₂ catalyst was added, the proportion of hydrocarbons reached the highest (28.83%), but it inhibited the production of phenols (3.3%). The presence of CuO promoted the production of phenols (9.70%), showing a good deoxidation performance. Compared with the oxide catalysts, the addition of molecular sieve catalysts only resulted in 2 ~ 3% phenols. Compared with strongly acidic molecular sieve catalysts, metal oxide catalysts showed certain catalytic activity in deoxidation and cracking, and showed some advantages in the formation of phenols.

GRAPHICAL ABSTRACT

KEYWORDS:

• Lignin
• mild catalytic pyrolysis
• bio-oil
• deoxygenation
• metal oxides

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

This research was supported by the National Natural Science Foundation of Shandong Province [grant number ZR2022ME109], the Natural Science Foundation of China [grant numbers 51976112, 52206264, 52130610], the Special project Fund of “ Taishan Scholar”of Shandong Province [grant number tsqn202103066]

Notes on contributors

Xiaoting Xing

Xiaoting Xing is a M.Sc. in agricultural engineering from Shandong University of Technology, China. She is engaged in research on catalytic conversion and utilization of biomass.

Lei Liu

Lei Liu is a B.E. from the College of Agriculture and Food Science, Shandong University of Technology, China. His research interests include biomass utilization and renewable energy.

Yuchun Zhang

Yuchun Zhang is a researcher at Shandong University of Technology, China. She has done lots of research on the theory and method system of biomass directed conversion to fuel, promoted the theoretical and technological progress of biomass energization. Her main research interests are catalytic upgrading of biomass, CFD, multi-phase flow, biomass energy for hydrogen production.

Peng Fu

Peng Fu is a professor in Shandong University of Technology, China. He has published more than 50 research articles in international journals. His research interests are thermal conversion of biomass to produce oil and gas fuels, heat transfer, renewable energy.

Zhiyu Li

Zhiyu Li is a researcher at Shandong University of Technology, China. His research focuses on the efficient conversion of agricultural waste.