Self-condensation of levulinic acid into bio-jet fuel precursors over acid zeolites: Elucidating the role of nature, strength and density of acid sites

Synthesis of biofuel precursors from benzaldehyde and cyclopentanone via aldehyde–ketone condensation in a deep eutectic solvent system

“…[1][2][3] Sustainable liquid biofuels (SLB) attained from biomass-derived platform compounds (BDPC) have drawn tremendous attention due to the concerns of the energy crisis and the goals of "carbon peaking" and "carbon neutrality". [4][5][6] With the advantages of renewability, low toxicity, low sulfur content, biodegradability and high-octane number, SLB can serve as a promising alternative fuel to fossil fuels to be compatible with existing engines for different applications. 7,8 Normally, BDPC (aldehydes, alcohols, phenols, etc.)…”

“…22 The catalysts usually applied in A-K condensation include solid acid catalysts (TiO 2 , zeolites, etc. ), 6,15 homogeneous and heterogeneous basic catalysts (NaOH, Ca(OH) 2 , CaO, and hydrotalcite, etc. ), 22,23 and bifunctional catalysts (Sn-MFI, MgF 2−x (OH) x , etc.…”

“…based on the differences between HBDs and HBAs. 1,6,[28][29][30] DESs prepared by coupling choline chloride (ChCl) and carboxylic acids have been found to be an exceptional alternative to convert BDPC into biofuel precursors. 3,31 In addition, metal chlorides (NiCl 2 , CrCl 3 , SnCl 4 , etc.)…”

Insights into the Influence of Feed Impurities on Catalytic Performance in the Solvent-Free Dimerization of Renewable Levulinic Acid

“…Although this transformation can be carried out using either base or acid catalysis, the use of solid bases is neither environmentally benign nor economical from an atomic point of view since the presence of the carboxylic group in LA can neutralize/deactivate base catalytic sites, leading to low efficiencies [11]. Therefore, a potential alternative to perform this process in a more sustainable way is the use of solid acid catalysts, such as commercially available acid zeolites [12] or sulfonic mesostructured SBA-15 silicas [13], as we have recently reported [14,15]. Particularly, H-Beta zeolites performed outstandingly owing to a unique combination of microporous structure, excellent textural properties, and an adequate balance of aluminum acid sites in terms of coordination and acid strength.…”

“…The influence of LA impurities on the stability and performance of the catalysts has been described in the literature mainly for the hydrogenation of bio-derived LA to ɣ-valerolactone [18,[21][22][23][24][25]. However, although several catalytic systems have been reported for the self-condensation of LA into bio-jet fuel precursors [11,[14][15][16][26][27][28][29], all the studies used pure LA as feedstock employing reaction conditions that may not be suitable for using in a process operating with contaminated LA streams derived from a real lignocellulosic biorefinery. Therefore, the purpose of the present work is to give one step further in the study of the solvent-free acid-catalyzed dimerization of renewable LA, via aldol condensation, evaluating the influence of the most common impurities from the production of LA on the catalytic performance, such as sulfuric acid, water, formic acid, and furfural.…”