Lignocellulose Liquefaction to Biocrude: A Tutorial Review

Abstract

After 40 years of research and development, liquefaction technologies are now being demonstrated at 200–3000 tons per year scale to convert lignocellulosic biomass to biocrudes for use as heavy fuel or for upgrading to biofuels. This Review attempts to present the various facets of the liquefaction process in a tutorial manner. Emphasis is placed on liquefaction in high‐boiling solvents, with regular reference to liquefaction in subcritical water or other light‐boiling solvents. Reaction chemistry, solvent selection, role of optional catalyst as well as biocrude composition and properties are discussed in depth. Challenges in biomass feeding and options for biocrude–solvent separation are addressed. Process concepts are reviewed and demonstration/commercialization efforts are presented.

Effect of Solvent, Role of Formic Acid and Rh/C Catalyst for the Efficient Liquefaction of Lignin

“…Lignin is a promising sustainable alternative raw material for fossil feedstocks to produce fuels, chemicals, and bio‐materials which are usually provided by the petroleum industry, such as phenolics, aromatics, and hydrocarbons . The valorization of lignin has several applications, such as synthesis of bio‐oil, phenolic resins, adhesives of polyurethane foams, carbon fiber, etc. One of the significant conversion pathways for lignin is liquefaction which generates bio‐oil and phenolic monomers .…”

Catalytic Transfer Hydrogenation of Biomass‐Derived Substrates to Value‐Added Chemicals on Dual‐Function Catalysts: Opportunities and Challenges

“…Due to a high oxygen content in the molecular structures, it is very difficult to convert these materials into commercial transportation fuels through simple processes . Most existing chemical conversion processes involve the use of large amounts of fossil‐derived H 2 under harsh operation conditions to remove significant oxygen contents (up to 50 %) from feedstocks .…”

Fully Recyclable Bio‐Based Thermoplastic Materials from Liquefied Wood

“…Therefore, biobased plastics are typically produced throughac omplex and expensive manufacturing chain that comprises the following steps: [3,4,[10][11][12][13] 1) Biomass fractionation to extract the sugars; 2) complex chemical and/or biotechnological conversion steps to convert them into valuablei ntermediates;3 )expensive recovery and purification steps to bring the intermediates to specification;4 )a polymerization step to produce the desired polymer. [3,[14][15][16][17] However,l iquefaction is preferred here because of the higherl iquid yield ( % 90 C%), the lower oxygen content,a nd the higher homogeneity of the bio-oil. Consequently,r esearch is still neededf or converting lignocellulosic biomass into addedvalue chemicals with high yields and low cost.…”

“…These productionp rocesses lead to expensive materi-als that requireh igh-performance applications to justify the considerable production cost. [17][18][19][20] The materialo btained after liquefaction and subsequent distillation was characterized in terms of physicochemical and mechanical properties and then reinforced with natural fibers.I nc ontrastt oc onventionalc omposites, this biocomposite can be fully recycled by liquefying the spent material, matrix, andf ibers, back into bio-oil. [10] Herein, we propose an alternative and low-costa pproacht o alignocellulosic thermoplastic, namely asingle-step conversion of lignocellulosetoasolid thermoplastic followed by reinforcement with cellulosic fibers to produce al ow-cost thermoplastic composite.…”

“…[3,[14][15][16][17] However,l iquefaction is preferred here because of the higherl iquid yield ( % 90 C%), the lower oxygen content,a nd the higher homogeneity of the bio-oil. [17][18][19][20] The materialo btained after liquefaction and subsequent distillation was characterized in terms of physicochemical and mechanical properties and then reinforced with natural fibers.I nc ontrastt oc onventionalc omposites, this biocomposite can be fully recycled by liquefying the spent material, matrix, andf ibers, back into bio-oil. [21] First, liquefaction of pinewood wasp erformed in six consecutive refill runs using guaiacol as starting solvent (as described in the Supporting Information and reported elsewhere [19] ).…”