Journal of Fluorine Chemistry — www. The title compound was obtained by a Claisen-type double condensation of acetone with trifluoroacetic acid ethyl ester and isolated as a solid monohydrate from the reaction mixture.
How to Cite Abstract Converting biomass into value-added chemicals holds the key to sustainable long-term carbon resource management. In this context, levulinic acid, which is easily obtained from cellulose, is valuable since it can be transformed into a variety of industrially relevant fine chemicals.
Here we present a simple protocol for the selective esterification of levulinic acid using solid acid catalysts. Silica supported sulfonic acid catalysts operate under mild conditions and give good conversion and selectivity with stoichiometric amounts of alcohols.
The sulfonic acid groups are tethered to the support using organic tethers. These tethers may help in preventing the deactivation of the active sites in the presence of water. It is abundantly available, with the potential of replacing fossil-based carbon on a scale sufficient for covering the worldwide demand for non-fuel chemicals .
Currently, the main research thrust is directed at lignocellulose, the most abundant fraction of biomass. All of these polymers are the subject of many studies . Synthesis of levulinic acid from ligno-cellulosic feedstocks and its principal uses to access fine chemicals.
Synthesis of levulinic acid from ligno-cellulosic feedstocks and its principal uses to access fine Jump to Scheme 1 Levulinic acid esters are of particular interest for the chemical industry [12,13].
Their main current market is represented by the formulation of flavours and fragrances although the scale of these preparations did not boosted demand yet. However, the seek to develop more eco-compatible solvents might grant to levulinates a novel route of application.
By tailoring their physicochemical properties they could become complementary to common esters and other solvents, which might be more harmful for both humans and the environment . It should be also noted that ethyl levulinate could shrink the emission of nitrogen oxides from exhausts of diesel engines when used as additive [17,18].
Due to their importance, new strategies have been developed for the production of levulinic esters . Although this route could ensure high chemical yields, it still presents a series of drawbacks. In particular, issues with catalyst recycling and product separation limits the environmental viability of this strategy.
As a result, it remains of high interest to develop alternatives to trigger this reaction, which are more sustainable, for instance through the design of suitable and recyclable solid acid catalysts.
In the literature, methods that use solid heteropolyacids, such as ammonium or mixed ammonium and silver-doped phosphotungstic acid, sulfated metal oxides such as sulfated titania, sulfated zirconiazeolites and hydrotalcites have been reported .
These solid catalysts share several advantages, including high activity and an easy recovery, which might provide a real basis for future application in commercial processes.
Furthermore, they often share another common pitfall, namely the use of large molar excess of alcohol, either for practical convenience  or to minimise ester hydrolysis.
Melero described the synthesis of mesostructured silica frameworks featuring pending organosulfonic arms. Here we present an alternative strategy in which a heterogeneous catalyst triggers the selective esterification of levulinic acid with a stoichiometric amount of alcohol.
In the last years, many methods have been developed for the transformation of homogeneous catalysts into recyclable heterogeneous ones. To prevent leaching, a common strategy is tethering the active species with the support via covalent bonds . Furthermore, the activity of the catalyst can be tuned through adoption of a suitable linker.
Jump to Figure 1 Results and Discussion As part of our interest in acid catalysis we prepared a set of solid materials for the esterification of levulinic acid. Upon preliminary screening, supported sulfonic acids seemed promising candidates. They were prepared following a reported procedure by the tethering method which consists of the immobilisation of a functional moiety on an inorganic support via covalent bonds ensured by a suitable linker .
In preliminary experiments reactions were carried out with a five-fold molar excess of alcohol. We started from this ratio as in the literature we did not retrieve any catalytic method for the esterification of biomass-derived acids that operates with a lower molar excess of alcohol .
Screening of different solid acids in the esterification reaction of levulinic acid with 1-pentanol.for catalyzing the synthesis of ester bonds are also able to catalyze their hydrolysis.
or in solvent-free bulk systems. Enzymatic processes can synthesize aliphatic and, to levulinate esters, valerolactone, and deriva-tives thereof.
WO A Optimized enzymatic synthesis of levulinate ester in solvent-free system_能源/化工_工程科技_专业资料 暂无评价|0人阅读|0次下载 | 举报文档. Synthesis of ethyl levulinate was carried out in solvent-free system using immobilized Candida antarctica lipase B (Novozym ) as the biocatalyst for the reaction.
The levulinate group can survive the synthesis conditions for these prodrugs while it can be easily removed by treating with 2M hydrazine in pyridine-acetic acid buffer for 10 minutes. Normal esters are not cleaved under these conditions.
In addition, the levulinate is less prone to migrate than the benzoate and acetate. Esterification, a solvent-free and no-glycerol-release system for biodiesel production, has been developed, and two-step catalysis of soybean oil, hydrolysis followed by esterification, with Yarrowia lipolytica lipase is reported in this paper.
Starch is an abundant, inexpensive, renewable, and fully biodegradable material. However, native starch has many unfavorable properties related to utilization as biomaterials including its high solubility in water and limited solubility in organic solvents, low tolerance to acidity, and poor processing properties.