Adding nickel formate in alkali lignin to increase contents of alkylphenols and aromatics during fast pyrolysis

Lignin and spent bleaching clay into mono-aromatic hydrocarbons by a cascade dual catalytic pyrolysis system: Critical role of spent bleaching clay

In the present study, a cascade dual catalytic system was used for the co-pyrolysis of lignin with spent bleaching clay (SBC) to efficiently produce mono-aromatic hydrocarbon (MAHs). The cascade dual catalytic system is composed of calcined SBC (CSBC) and HZSM-5. In this system, SBC not only acts as a hydrogen donor and catalyst in the co-pyrolysis process, but is also used as a primary catalyst in the cascade dual catalytic system after recycling the pyrolysis residues. The effects of different influencing factors (i.e., temperature, CSBC-to-HZSM-5 ratio, and raw materials-to-catalyst ratio) on the system were explored. It was observed that, when the temperature was 550 °C, the CSBC-to-HZSM-5 ratio was 1:1, and when the raw materials-to-catalyst ratio was 1:2, the highest bio-oil yield was 21.35 wt%. The relative MAHs content in bio-oil was 73.34 %, whereas the relative polycyclic aromatic hydrocarbons (PAHs) content was 23.01 %. Meanwhile, the introduction of CSBC inhibited the generation of graphite-like coke as indicated by HZSM-5. This study realizes the full resource utilization of spent bleaching clay and reveals the environmental hazards caused by spent bleaching clay and lignin waste.

Features and Commercial Performance of a System of Biomass Gasification for Simultaneous Clean Heating and Activated Carbon Production

Biomass is a renewable and clean energy. Moreover, clean heating plays a vital role in solving issues related to the heating source structures in northern China. This paper reports on our novel technology: a system of biomass (mainly fruitwood waste, referred to in short as FWW) gasification for simultaneous clean heating and fruitwood activated carbon (FAC) production. In particular, we will discuss the features of our gasification system and product characteristics, as well as energy efficiency, environmental benefits, and economic benefits. The results showed that the energy conversion from FWW gasification was as follows: 48.10% hot gas, 49.08% fruitwood gasified carbon (FGC), and 2.82% energy loss. The NO _x emissions of this system were about 126 mg/Nm³. The iodine adsorption values of the derived FGC and FAC were about 550 and 1000 mg/g, respectively. The system of gasification consumed 36 t of FWW per day, obtained 10 t of FGC, and produced 5 t of FAC. The emissions of CO₂ were neutral during the operation, and the clean heating area was 4100 m²/d in Chengde, Hebei, China, with the payback period under one heating season. These results show that the system is practical, economical, energy-saving, and environmentally friendly.

Catalytic Fast Pyrolysis of Poly (Ethylene Terephthalate) (PET) with Zeolite and Nickel Chloride

The pyrolysis of poly (ethylene terephthalate) (PET) in the presence of ZSM-5 zeolite and NiCl₂ as a catalyst was studied at different temperatures under N₂ atmosphere. Quantitative ¹³C nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FT-IR) were applied to characterize the waxy and solid residue. The carboxyl and aliphatic hydroxyl groups in the waxy residue have been greatly depleted after the use of zeolite during pyrolysis on the basis of the results of ¹³C NMR and FT-IR analysis. The proportion of aromatic hydroxyl groups increased by 21.82% when the mass ratio of zeolite to PET was set to 2.0/1.0. The results indicate that ZSM-5 is able to facilitate the decomposition of carboxyl, aliphatic groups, and ether bonds in the primary products produced from the pyrolysis of PET. In addition, the deoxygenation effects on the waxy products have been significantly enhanced with the addition of zeolite based on the results of NMR.

Product-oriented decomposition of lignocellulose catalyzed by novel polyoxometalates-ionic liquid mixture

Lignocellulose was oxidatively decomposed in a newly developed polyoxometalates-imidazolium ionic liquid mixture. Aromatic compounds covering acids, esters, ketones, aldehydes, and phenols were selectively produced under various conditions. 4-Hydroxylbenzoic acid was dominatingly yielded under low temperature and high oxidant concentration. Phenolic compounds were mainly generated at high temperature with a selectivity of 45.1% and a yield of 4.3%, higher than those generated in similar polyoxometalates-ionic liquids system. The products distributions and residues of lignocellulose decomposition under various conditions were characterized; the influences of the ionic liquids anions on the polyoxometalates-ionic liquids complex formation, the acidic and redox properties of the catalyst, and the final products were profoundly investigated; and a tentative reacting process was proposed. The ionic liquid could be recycled for five times. This work not only provided a new lignocellulose decomposition strategy to produce aromatic products, but also offered a guidance for product-oriented lignocellulose decomposition.

Lignin Valorizations with Ni Catalysts for Renewable Chemicals and Fuels Productions

Energy and fuels derived from biomass pose lesser impact on the environmental carbon footprint than those derived from fossil fuels. In order for the biomass-to-energy and biomass-to-chemicals processes to play their important role in the loop of the circular economy, highly active, selective, and stable catalysts and the related efficient chemical processes are urgently needed. Lignin is the most thermal stable fraction of biomass and a particularly important resource for the production of chemicals and fuels. This mini review mainly focuses on lignin valorizations for renewable chemicals and fuels production and summarizes the recent interest in the lignin valorization over Ni and relevant bimetallic metal catalysts on various supports. Particular attention will be paid to those strategies to convert lignin to chemicals and fuels components, such as pyrolysis, hydrodeoxygenation, and hydrogenolysis. The review is written in a simple and elaborated way in order to draw chemists and engineers’ attention to Ni-based catalysts in lignin valorizations and guide them in designing innovative catalytic materials based on the lignin conversion reaction.

Study on the Product Characteristics of Pyrolysis Lignin with Calcium Salt Additives

This study investigated and compared the product characteristics of pyrolysis lignin under different catalytic effects resulting from various calcium salts. The pyrolysis of lignin was conducted in a fixed-bed reactor with calcium salt additives, which included CaCl₂, Ca(OH)₂, and Ca(HCOO)₂. The compositions of gas and bio-oil were detected using gas chromatography/mass spectrometry (GC/MS). The characterizations of chars were examined using Brunauer–Emmett–Teller (BET) surface area and scanning electron microscopy (SEM). The results indicate that all three types of calcium salts helped to promote bio-oil yield and inhibit gas and char from forming. Regarding the composition of gas products, calcium salt additives increased the concentrations of H₂ and CH₄ while decreasing the concentration of CO. In addition, calcium salt additives facilitated the formation of phenol and alkyl-phenols in bio-oil, but reduced the yields of guaiacol and vanillin, in the order CaCl₂ < Ca(OH)₂ < Ca(HCOO)₂. Furthermore, when compared with the addition of CaCl₂, the chars prepared by the addition of Ca(OH)₂ and Ca(HCOO)₂ had relatively higher BET surface areas. In conclusion, Ca(HCOO)₂ had the greatest positive influence in regard to the product quality of lignin pyrolysis whilst also elevating the yield of value-added chemicals in bio-oils.

Formate-assisted analytical pyrolysis of kraft lignin to phenols

The effect of sodium formate (SF), calcium formate (CF) and nickel formate (NF) as additives on analytical pyrolysis performance of kraft lignin was conducted. The results showed that these formates promoted the releasing of volatiles, leading to the rapid degradation of kraft lignin. High relative content of monophenols (53.77%), especially of guaiacol (23.65%), were achieved from the pyrolysis of pure lignin. The relative content of guaiacol was dramatically decreased after the adding of formates in kraft lignin. The relative content of polyphenols such as 3-methylcatechol and 4-methylcatechol reached to 16.97%, 16.23% and 21.95% with the formates of SF, CF and NF, respectively. The NF showed the highest selectivity of polyphenols and hydrocarbons. The increase of polyphenols and hydrocarbons from NF was the synergetic effect of the hydrogen radical reaction from the formic functional groups under the catalysis of Ni and/or NiO produced from the NF pyrolysis process.

Catalytic pyrolysis of lignin in a cascade dual-catalyst system of modified red mud and HZSM-5 for aromatic hydrocarbon production

Catalytic pyrolysis of lignin over a dual-catalyst system of modified red mud and HZSM-5 was carried out in a bench-scale micro-reactor. Effects of pyrolysis temperature, modified red mud to HZSM-5 ratio, catalysts to lignin ratio on the yield of products and selectivity of aromatic hydrocarbons were investigated. Results indicated that 550 °C was the optimal pyrolysis temperature with the maximal yield of bio-oil (20.16 wt%). At a modified red mud to HZSM-5 ratio of 1:1, the content of monocyclic aromatic hydrocarbons (MAHs) increased to 41.27% whereas that of polycyclic aromatic hydrocarbons (PAHs) decreased to 22.65%. Likewise, at a catalysts to lignin ratio of 2:1, a higher content of MAHs was produced with a decreased content of PAHs. The cascade dual-catalyst system may serve as an efficient approach to disposing lignin and red mud wastes with significant environmental impact. Besides, this study provides a solution for the valorization of lignin-rich resources.

Lignin valorization for the production of renewable chemicals: State-of-the-art review and future prospects

Lignin is an abundant biomass resource in aromatic structure with a low price in market, which can serve as renewable precursors of value-added products. However, valorization rate of annually produced lignin is less than 2%, suggesting the need for technological advancement to capitalize lignin as a versatile feedstock. In recent years, efficient utilization of lignin has attracted wide attention. This paper summarizes the research advances in the utilization of lignin resources (mainly in the last three years), with a particular emphasis on two major approaches of lignin utilization: catalytic degradation into aromatics and thermochemical treatment for carbon material production. Hydrogenolysis, direct pyrolysis, hydrothermal liquefaction, and hydrothermal carbonization of lignin are discussed in detail. Based on this critical review, future research directions and development prospects are proposed for sustainable and cost-effective lignin valorization.