Mechanism of the Fe-Assisted Hydrothermal Liquefaction of Lignocellulosic Biomass

A comprehensive review on unleashing the power of hydrogen: revolutionizing energy systems for a sustainable future

Population growth and environmental degradation are major concerns for sustainable development worldwide. Hydrogen is a clean and eco-friendly alternative to fossil fuels, with a heating value almost three times higher than other fossil fuels. It also has a clean production process, which helps to reduce the emission of hazardous pollutants and save the environment. Among the various production methodologies described in this review, biochemical production of hydrogen is considered more suitable as it uses waste organic matter instead of fossil fuels. This technology not only produces clean energy but also helps to manage waste more efficiently. However, the production of hydrogen obtained from this method is currently more expensive due to its early stage of development. Nevertheless, various research projects are underway to develop this method on a commercial scale.

Hydrothermal liquefaction of lignocellulosic biomass with potassium phosphate and iron and their binary mixture: A comprehensive investigation on the yields and compositions of biocrude and solid residue

Hydrothermal liquefaction of corn, soybean, rice and wheat straws with K3PO4, Fe and Fe + K3PO4 at 320 °C for 30 min was examined. The addition of K3PO4 led to the highest biocrude yields from hydrothermal liquefaction of rice straws (39.20 wt%). Particularly, the biocrude yields from K3PO4-catalyzed hydrothermal liquefaction of corn and rice straws were ∼ 10 wt% higher than those from non-catalytic run (19.4 and 27.8 wt%). Catalytic hydrothermal liquefaction with K3PO4 had minimal impact on the elemental compositions of biocrudes and solid residue. Furthermore, K3PO4 promoted the enrichment of low-boiling components in biocrudes by 2.02 wt%. for hydrothermal liquefaction of wheat straw. Moreover, the incorporation of K3PO4 induces the occurrence of dense porous structure on the surface of solid residue, making it highly suitable as an adsorbent or catalyst carrier. Finally, potential reaction network and mechanisms of catalytic hydrothermal liquefaction of straw have been proposed and discussed detailly.

Hydrothermal Liquefaction of Lignocellulosic and Protein-Containing Biomass: A Comprehensive Review

Hydrothermal liquefaction (HTL) is a thermochemical depolymerization technology, also known as hydrous pyrolysis, that transforms wet biomass into biocrude and valuable chemicals at a moderate temperature (usually 200–400 °C) and high pressure (typically 10–25 MPa). In HTL, water acts as a key reactant in HTL activities. Several properties of water are substantially altered as the reaction state gets closer to the critical point of water, which can result in quick, uniform, and effective reactions. The current review covers the HTL of various feedstocks, especially lignocellulosic and high protein-containing feeds with their in-depth information of the chemical reaction mechanisms involved in the HTL. Further, this review gives insight and knowledge about the influencing factors such as biomass pretreatment, process mode, process conditions, etc., which could affect the efficiency of the hydrothermal process and biocrude productivity. In addition, the latest trends, and emerging challenges to HTL are discussed with suitable recommendations.

A Review of Hydrothermal Liquefaction of Biomass for Biofuels Production with a Special Focus on the Effect of Process Parameters, Co-Solvents, and Extraction Solvents

Hydrothermal liquefaction is one of the common thermochemical conversion methods adapted to convert high-water content biomass feedstocks to biofuels and many other valuable industrial chemicals. The hydrothermal process is broadly classified into carbonization, liquefaction, and gasification with hydrothermal liquefaction conducted in the intermediate temperature range of 250–374 °C and pressure of 4–25 MPa. Due to the ease of adaptability, there has been considerable research into the process on using various types of biomass feedstocks. Over the years, various solvents and co-solvents have been used as mediums of conversion, to promote easy decomposition of the lignocellulosic components in biomass. The product separation process, to obtain the final products, typically involves multiple extraction and evaporation steps, which greatly depend on the type of extractive solvents and process parameters. In general, the main aim of the hydrothermal process is to produce a primary product, such as bio-oil, biochar, gases, or industrial chemicals, such as adhesives, benzene, toluene, and xylene. All of the secondary products become part of the side streams. The optimum process parameters are obtained to improve the yield and quality of the primary products. A great deal of the process depends on understanding the underlined reaction chemistry during the process. Therefore, this article reviews the major works conducted in the field of hydrothermal liquefaction in order to understand the mechanism of lignocellulosic conversion, describing the concept of a batch and a continuous process with the most recent state-of-art technologies in the field. Further, the article provides detailed insight into the effects of various process parameters, co-solvents, and extraction solvents, and their effects on the products’ yield and quality. It also provides information about possible applications of products obtained through liquefaction. Lastly, it addresses gaps in research and provides suggestions for future studies.

Hydrothermal liquefaction of Fe-impregnated water hyacinth for generation of liquid bio-fuels and nano Fe carbon hybrids

In this work, hydrothermal liquefaction experiments of iron impregnated water hyacinth were performed with a motive to enhance bio-oil yields along with generation of nanometal carbon hybrids. Iron nanoparticles were impregnated and its metal loading was determined by ICP-MS. The impact of operating parameters like temperature, biomass to water ratio and reaction time on bio-oil yields was studied. During hydrothermal liquefaction a maximum total bio-oil yield of 38.1% was obtained at 280 °C along with formation of nanometal carbon hybrids. The light oil and heavy oil fractions were characterized by GCMS and NMR for determining the key components. The light oil mainly comprises of alkanes, alcohols and esters whereas heavy oil contains esters, ethers, carboxylic acids and phenols. XRD and XPS of Fe-impregnated water hyacinth and residues confirmed the transition of Fe^+3/+2 to Fe⁰. TEM analysis resulted an average particle size of Fe nanoparticles around 19.6 nm.

Overview of the recent advances in lignocellulose liquefaction for producing biofuels, bio-based materials and chemicals

The concerns over the increasing energy demand and cost as well as environmental problems derived from fossil fuel use are the main driving forces of research into renewable energy. Lignocellulosic biomass comprised of cellulose, hemicellulose, and lignin is an abundant, carbon neutral, and alternative resource for replacing fossil fuels in the future. Solvent liquefaction of lignocellulosic biomass is a promising route to obtain biofuels, bio-based materials, and chemicals using a range of solvents as reaction media under moderate reaction conditions. Recently, several researchers have considered novel approaches for enhancing the process efficiency and economics. This review article reports the state-of-the-art knowledge of lignocellulose liquefaction in the recent three years with the main focus on the feedstock, liquefaction technology, target products, and degradation mechanism of each biomass component. This review is expected to provide an important reference for research into the solvent liquefaction of lignocellulose in the near future.