Role of Oxophilic Metal Ions (Mo, Zr, Ti) Impregnated Ni/γ-Al2O3 Catalysts for Hydrothermal Liquefaction of Kraft Lignin

Jul 9, 2026

Upload by Rowan

The study investigates how oxophilic metal ions (Mo, Zr, Ti) loaded on Ni/γ-Al2O3 catalysts influence hydrothermal liquefaction of kraft lignin using IPA at 280 °C for 30 min. Lignin liquefaction reaches 65.4 wt% with 10 wt% Ni/Al and 81.3% total conversion, while promoters markedly enhance Lewis acidity on the catalyst surface. Maximum bio-oil yield is 72 wt% with 91.5% conversion using 3 wt% Ti–10Ni/Al. Solvent screening shows IPA superior to methanol and ethanol; IPA-water (50:50) further improves liquefaction to 74.8 wt%. The best catalyst (10Ni–3Ti/Al) is tested over four cycles, showing slight activity loss from char blocking. GC-MS, 1H NMR, FT-IR, and catalyst characterization (XRD, BET, XPS) link product selectivity and lignin 3D structure fragmentation to catalytic promotion.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages9

Reading Time23 min

Introduction

Background and motivation

Oxophilic metal ion–promoted catalytic hydrothermal liquefaction

Catalyst preparation and promoter role

Solvent effects and co-solvent optimization

Catalyst recyclability and deactivation

Product analysis and characterization

Journal of the Energy Institute 114 (2024) 101603 Contents lists available at ScienceDirect Journal of the Energy Institute journal [homepage: www.elsevier.com/locate/joei](homepage: www.elsevier.com/locate/joei) | Role of oxophilic metal ions (Mo, Zr, Ti) impregnated Ni/γ -Al2O3 catalysts for hydrothermal liquefaction of kraft lignin Yanfang Zhu a, Yuzhen Zhao a, Qingbo Lib, Xinli Shi b, Xiaorui Lic, Guiyang Xud, * a Technological Institute of Materials & Energy Science (TIMES), Xi’an Key Laboratory of Advanced Photo-Electronics Materials and Energy Conversion Device, School of Electronic Information, Xijing University, Xi’an, 710123, PR China b ShanDong Lanbeisite Educational Equipment Group Co., Ltd, PR China c School of Environmental and Chemical Engineering, Jiangsu University of Science and Technology, Zhenjiang, 212114, PR China d Xi’an Modern Chemistry Research Institute, Xi’an, 710065, PR China | | | | --- | --- | --- | | A R T I C L E I N F O | | A B S T R A C T | | Handling Editor: Dr. Paul Williams | | In this study, the effect of oxophilic metal ions (Mo, Zr, and Ti) loaded Ni/γ-Al2O3 (Al) catalysts was explored for the first time for the hydrothermal liquefaction of kraft lignin using IPA for 30 min/280 ◦ C. The liquefaction of lignin was noticed to be 65.4 wt% with 10 wt% loaded Ni/Al with an 81.3% total conversion. The performance of Ni/Al was enhanced remarkably by using the oxophilic metal ions as promoters owing to an increase in the Lewis character of the catalyst’s surface. The bio-oil yield was a maximum of 72 wt% with a 91.5% conversion using 3 wt% loaded Ti–10Ni/Al. The different alcoholic solvents such as methanol, ethanol, and IPA were also examined for the same. However, the best liquefaction was noticed with IPA owing to better H-donor tendency. Additionally, a series of IPA-water co-solvent examinations attributed to a significant improvement in the liquefaction to 74.8 wt%(50:50) IPA-water system. The optimum catalyst 10Ni–3Ti/Al was tested for four catalytic cycles, which indicated a slight loss in the catalytic activity because of blockage of the catalytic active site by char deposition. The GC-MS investigation of optimum catalytic bio-oil showed the highest selectivity of acetosyringone (68.5%) and 2-methoxy-phenol (22.8%), which was observed to be only 30.1 and 5.1% for non-catalytic bio-oil. The 1H NMR and FT-IR investigation of raw lignin and bio-oil proved the breakage of lignin’s 3D structure into respective G-and S-type monomeric compounds. Additionally, catalysts were characterized using the XRD, BET, and XPS analysis. | | Keywords: Hydrothermal liquefaction Kraft lignin γ-Al2O3 Oxophilic metal ions Acetosyringone | | | 1. Introduction Restriction on the emission of carbon dioxide, depletion in reserved fossil fuel, population explosion, increased energy demand have forced researchers around the globe to find sustainable, low cost alternating sources of energy [1,2]. Renewable energy can be a boon to achieve cleaner, greener and sustainable energy goal (1–3). Biomass is considered as most selective sustainable, renewable source for future energy due to its diverse functionality and plentiful availability [3]. In order to achieve this goal lignin has been explored by various researchers as a source of chemical and bio-fuel. Lignin, one of the most dominant biopolymer in nature, is generated as waste in pulp and paper industries and was simply discarded or it is estimated that by 2030 the production of lignin might augment by 225 millions of tons annually [4]. Lignin is three dimensional from three monomer units ie coniferyl alcohol, sinapyl alcohol (dimethoxy-4-hydroxycinnamyl), and p-coumaryl alcohol (4-hydroxycinnamyl). It has been considered that these monomeric lignols are attached by C–C bond or by C–O (55–65%) [5–7]. Besides its diverse functionality, capability to produce numerous aromatics, its heterogeneous, highly complex structure hinde

FAQs

How do oxophilic metal ions (Mo, Zr, Ti) improve Ni/γ-Al2O3 performance in lignin liquefaction?

Oxophilic metal ions enhance the Lewis character of the catalyst surface, promoting lignin liquefaction and increasing overall conversion and bio-oil yield.

Why does IPA outperform methanol and ethanol as the solvent for hydrothermal liquefaction?

IPA provides a stronger H-donor tendency, leading to the best liquefaction performance among the tested alcoholic solvents.

What causes the slight loss of catalytic activity after repeated cycles of the optimum catalyst?

Activity declines due to blockage of catalytic active sites by char deposition during recycling.

Jul 9, 2026

Upload by Rowan