γ-Valerolactone (GVL) orgamma-valerolactone is anorganic compound with theformula C5H8O2. This colourless liquid is one of the more commonlactones. GVL ischiral but is usually used as theracemate. It is readily obtained from cellulosic biomass and is a potential fuel andgreen solvent.
GVL behaves as aprodrug toγ-hydroxyvaleric acid (GHV), adrug with similar effects to those ofγ-hydroxybutyric acid (GHB), albeit with less potency in comparison.[4] Because GHB is controlled in many parts of the world, while GVL is not, GVL has gained popularity as a legal substitute for GHB.[4][5]
GVL has been identified as a potential green solvent. Because of its herbal odor, it is used in the perfume and flavor industries.[7] It is a structural isomer ofδ-valerolactone.
Since it is readily obtained from glucose, GVL has long been identified as a potential "green fuel."[8] GVL retains 97% of the energy of glucose and can be blended by itself in gasoline where it performs comparably toethanol/gasoline mixtures.[9][10] However, due to blending limits for use in conventional combustion engines, it may be more efficient to convert GVL into liquidalkenes (oralkanes). The first step in this process is the ring-opening of GVL to yield a mixture ofpentenoic acids. These acids can then bedecarboxylated to producebutene and CO2. These conversions can be performed withzeolite catalysts.[11] After this stream is dehydrated, the products can beoligomerized at elevated pressures in the presence of a common acid-catalyst to yield alkenes with highermolecular weights, targeted for gasoline and other fuel applications.[12]
One of the main advantages that allows GVL to be a practicalbiofuel is that it is relatively inexpensive to produce. Using a cheapfeedstock, this biofuel can be produced at prices between 2-3 US$/gallon.[9] The conversion of GVL to transportation fuel capable alkenes only requires a system containing two flow reactors, two phase separators, and a simple pumping arrangement for the delivery of an aqueous GVL feed. Since the use ofprecious metal catalysts is not required, this also decreases the total price of fuel production.[11]
Apart from its value as a potential fuel in its own right, gamma-valerolactone has shown promise in laboratory-scale thermocatalytic production of soluble carbohydrates from cornstover and wood at high yields. The biomass reacts in a solvent mixture of water, dilute sulfuric acid, and gamma-valerolactone, itself derived from biomass. The gamma-valerolactone promotes thermocatalytic hydrolysis into monosaccharides by complete solubilization of the raw material, including lignins. The saccharide products can be recovered from the lactone into water solution by antisolvent addition of salt or liquid carbon dioxide. The product can be used as feedstock for producing furans or ethanol at high yield, while the gamma-valerolactone is returned to the catalytic cycle.[13]
Gamma-valerolactone has been studied and shown the potential to prepare dope solutions for the fabrication of polymeric membranes. Due to the toxicity of the traditional solvents, green solvents were investigated in recent years.[14] Due to its environmentally friendly profile, gamma-valerolactone showed the potential to fabricatepolysulfone membranes as a co-solvent.[15]
^Horváth, I. T.; Mehdi, H.; Fábos, V.; Boda, L.; Mika, L. T. (2008). "γ-Valerolactone—a sustainable liquid for energy and carbon-based chemicals".Green Chemistry.10 (2):238–242.doi:10.1039/b712863k.
^Mantilla, A.; et al. (2005). "Oligomerization of isobutene on sulfated titania: Effect of reaction conditions on selectivity".Catalysis Today.107–108:707–712.doi:10.1016/j.cattod.2005.07.153.
^Figoli, A.; Marino, T.; Simone, S.; Di Nicolò, E.; Li, X.-M.; He, T.; Tornaghi, S.; Drioli, E. (2014-07-03). "Towards non-toxic solvents for membrane preparation: a review".Green Chemistry.16 (9): 4034.doi:10.1039/c4gc00613e.ISSN1463-9262.
^Dong, Xiaobo; Shannon, Halle D.; Escobar, Isabel C. (January 2018), "Investigation of PolarClean and Gamma-Valerolactone as Solvents for Polysulfone Membrane Fabrication",Green Polymer Chemistry: New Products, Processes, and Applications, American Chemical Society, pp. 385–403,doi:10.1021/bk-2018-1310.ch024,ISBN978-0841233898
