Butyl Levulinate Research Articles

Silica‐Mediated Incorporation of Lipase Into The Bulk of a Deep Eutectic Solvent: An Efficient Biocatalytic Phase for Esters Synthesis

Aiming at sustainable solutions suitable for industrial‐scale catalysis catalytic phase containing lipase and Deep Eutectic Solvent (DES) was designed. To achieve this, both physical and chemical immobilizations of lipases were performed on the surface of silica and carbon materials. The catalytic activity of developed biosystem was tested in biotransformation of α‐angelica lactone into butyl levulinate at 60°C. The best results were achieved for Candida antarctica lipase B adsorbed on fumed silica suspended in choline chloride: glycerol (1:2) with the addition of 20 wt% of water. Under these conditions 99.9% conversion of α‐angelica lactone and 100% selectivity to butyl levulinate were obtained after 45 min. The biocatalytic system maintained its activity for up to five consecutive reaction cycles with full conversion of lactone to ester. The heterogenization of the enzyme allowed the biocatalyst to be integrated into the bulk of the DES, which includes essential water. This combination resulted in the formation of a stable and easy‐to‐operate catalytic phase where reagents formed a second organic phase. The integration of cost‐effective biocatalyst with process efficiency provides a greener alternative with significant potential for industrial use.

Metal-Nitrate-Catalyzed Levulinic Acid Esterification with Alkyl Alcohols: A Simple Route to Produce Bioadditives

This work developed an efficient route to produce fuel bioadditive alkyl levulinates. Special attention was paid to butyl levulinate, which is a bioadditive with an adequate carbon chain size to be blended with liquid fuels such as diesel or gasoline. In this process, levulinic acid was esterified with butyl alcohol using cheap and commercially affordable metal nitrates as catalysts, producing bioadditives at more competitive costs. Iron (III) nitrate was the most active and selective catalyst toward butyl levulinate among the salts evaluated. In solvent-free conditions, with a low molar ratio and catalyst load (1:6 acid to alcohol, 3 mol% of Fe (NO3)3), conversion and selectivity greater than 90% after an 8 h reaction was achieved. A comparison of the iron (III) nitrate with other metal salts demonstrated that its superior performance can be assigned to the highest Lewis acidity of Fe3+ cations. Measurements of pH allow the conclusion that a cation with high Lewis acidity led to a greater H+ release, which results in a higher conversion. Butyl levulinate and pseudobuty levulinate were always the primary and secondary products, respectively. The consecutive character of reactions between butyl alcohol and levulinic acid (formation of the pseudobutyl levulinate and its conversion to butyl levulinate) was verified by assessing the reactions at different temperatures and conversion rates. A variation in Fe(NO3)3 catalyst load impacted the conversion much more than reaction selectivity. The same effect was verified when the reactions were carried out at different temperatures. The reactivity of alcohols with different structures depended more on steric hindrance on the hydroxyl group than the size of the carbon chain. A positive aspect of this work is the use of a commercial iron nitrate salt as the catalyst, which has advantages over traditional mineral acids such as sulfuric and hydrochloric acids. This solid catalyst is not corrosive and avoids neutralization steps after reactions, minimizing the generation of residues and effluents.

Ketalization mechanism of glycerol to biobased glycerol levulinate ketal over HZSM-5: A combined experimental and theoretical study

Methyl levulinate ketal (MLK) is a novel biobased chemical derived from glycerol via ketalization, and exploring its synthesis mechanism is of great significance for the high-value utilization of biomass resources. In this study, the ketalization reaction of glycerol was evaluated using the MLK yield calculated by the GC internal standard method. The acidity of HZSM-5 was determined by NH3-TPD. The catalyst screening experiments demonstrated that HZSM-5 in zeolites and AlCl3 in metal salts exhibited high catalytic activity in the synthesis of MLK. Furthermore, the kinetic results indicated that the HZSM-5 zeolite catalyst exhibited a lower apparent activation energy in catalyzing the synthesis of MLK compared to the metal salt catalyst AlCl3. The ketalization reactions of levulinate and glycerol catalyzed by different types of acidic sites in HZSM-5 were then investigated using the density functional theory method. A comprehensive catalytic path, free energy changes, intermediates, and transition state structures were proposed. Furthermore, the free energy barriers of ethyl levulinate ketal and butyl levulinate ketal catalyzed by HZSM-5 were calculated, and the difference between the steric hindrance effect and the electronic effect of alkyl in levulinate was compared. This study enhances the understanding of ketalization reactions and will be useful in future catalyst design studies.

Intensification of valorization of cooked rice water through energy-efficient synthesis of drop-in biofuel (butyl levulinate): engine performance, emission profile, and environmental impact assessments.

For the first time, an energy-efficient and eco-friendly technology for the conversion of abundantly available kitchen waste, specifically waste cooked rice water (WCRW) to drop-in- biofuels, namely, butyl levulinate (BL), has been explored. The synthesis of BL was accomplished employing butyl alcohol (BA) and WCRW in an energy-efficient UV (5W each UVA and UVB)-near-infrared (100W) irradiation assisted spinning (120rpm) batch reactor (UVNIRSR) in the presence of TiO2-Amberlyst 15 (TA15) photo-acidic catalyst system (PACS). The optimal 95.81% yield of BL (YBL) could be achieved at 10 wt% catalyst concentration, 60°C reaction temperature, 80min time, and 1:10 WCRW: BA concentration as per Taguchi statistical design. Moreover, additional combination of different PACS such as TiO2-Amberlyst 16, TiO2-Amberlyst 36, and TiO2-Amberlite IRC120 H rendered 86.72% YBL, 90.04% YBL, and 93.47% YBL, respectively, proving superior efficacy compared to individual activity of the acidic catalysts and photocatalysts. The heterogeneous reaction kinetics study for TA15 PACS suggested Langmuir-Hinshelwood model to be the best fitted model. A significant 63.33% energy could be saved by UVNIRSR as compared to conventional heated reactor at the optimized experimental condition using PACS TA15. An overall alleviation in environmental pollution with 59.259% reduction in GWP, 15.254% decline in terrestrial ecotoxicity, 18.238% diminution in marine ecotoxicity, 17.25% decrease in ozone formation affecting human health, 5.865% reduction in human non-carcinogenic toxicity, 18.65% diminution in ozone formation affecting terrestrial ecosystem, 55.17% significant decrease in terrestrial acidification, and 25.619% mitigation in fresh water ecotoxicity could be observed. Furthermore, BL-biodiesel-diesel blends (3% BL, 7% biodiesel, and 90% diesel) exhibited significant reduction (25.45% and 36%, respectively, for CO and HC) in harmful engine exhaust emissions demonstrating environmental sustainability of the overall process.

Production of alkyl levulinates as a versatile precursor by phosphomolybdate-impregnated g-C3N4 catalysts

Alkyl levulinates are a class of compounds that have diverse applications and show great promise as environmentally friendly fuel additives. These compounds are renewable, have a high energy density, and can easily be used with existing infrastructure. Therefore, they can play a significant role in contributing to the ongoing endeavors toward more sustainable and efficient energy solutions. In this study, alkyl levulinates (ALs) as fuel additives were synthesized using phosphomolybdate g-C3N4 (PMox/g-C3N4) as an efficient catalyst for the esterification reaction of levulinic acid (LA) with three diverse alcohols, namely ethanol, 1-butanol, and 1-hexanol. An experimental investigation assessed the impact of several key factors, such as temperature, the volumetric proportion of LA to alcohol, reaction time, catalyst loading, and catalyst amount, on the chemical process under study. For ethyl levulinate (EL) a 76 % yield was obtained at 130 °C, 8 h reaction time, LA: ethanol 1:12, and 20 mg catalyst. Also, a > 99 % yield was obtained for the butyl levulinate (BL) production at 130 °C, 8 h reaction time, LA: alcohol proportion of 1:12, and 10 mg catalyst. Hexyl levulinate (HL) was achieved with 71 % yield under the optimal condition of 230 °C, 8 h reaction time, LA: hexanol 1:20, and 10 mg catalyst.

Impact of aleatory and epistemic uncertainties on thermal risk and production assessment: Application to the hydrogenation of levulinic acid and butyl levulinate

The hydrogenation of levulinates, derivatives from cellulose hydrolysis, leads to the platform molecule γ-valerolactone (GVL). While prior investigations indicate the propensity for thermal runaways in this reaction, a comprehensive sensitivity analysis has been conspicuously absent in the existing literature. This study endeavors to scrutinize the influence of input parameters on both thermal risks and the production rate during GVL synthesis. Distinguished by its dual focus on sensitivity analyses, this manuscript also contrasts the implications of aleatory and epistemic uncertainties on thermal risk and production metrics. Aleatory uncertainties arise from the inherent variability of initial conditions, while epistemic uncertainties emanate from incomplete knowledge of the kinetic model. Employing Sobol global sensitivity analysis on the kinetic model, we delineate the hierarchical importance of various parameters. This analysis incorporates a quantification of uncertainty, and algorithmic approaches are proffered. The findings reveal that the initial temperature, the initial mass of the Ru/C catalyst, and hydrogen pressure are pivotal factors that are directly proportional to thermal risk and production efficiency. The implications of uncertainty on these variables are also discussed.

Anchored silicotungstic acid: Study of the synthesis of biofuel additive from levulinic acid & effect of supports

The present article reports the synthesis of butyl levulinate, a potential biofuel additive via the esterification of levulinic acid and n-butanol. A sustainable catalytic approach using heterogeneous catalysts based on 12-tungstosilicic acid (SiW12) and supports, nMCM-48 and MCM-22 was developed via a detailed optimization study to achieve maximum selectivity of butyl levulinate (≥95%) at mild reaction conditions and reused the catalysts for multiple runs. Importantly, the effect of nature as well as the structure of the supports on activity was studied via kinetic experiments and comparative studies. Based on this, the best catalyst was proposed and wide range of alkyl levulinates, possessing fuel-blending properties were synthesized using best catalyst, showcasing its versatile nature.

Customizing reformulated gasoline using biofuel-additives to replace aromatics

Understanding the thermophysical and dynamic characteristics of hydrocarbon blends is crucial for optimizing engine performance and emissions control. By investigating the properties of blends with diverse biomass-derived oxygenates (BDO) as green fuel additives, we aim to mitigate toxic aromatic compounds in both conventional and reformulated gasoline. Experimental verification of prior molecular dynamics (MD) simulation results on gasoline+alkyl levulinate blends establishes the validity of our gasoline model, establishing MD simulations as a powerful tool for investigating blend properties. Subsequent MD simulations estimate the density, viscosity, and compressibility of three gasoline formulations blended with four BDOs (butanol, dimethyl ether, methyl ethyl ketone, and methyl pentanoate). At the molecular level, these BDOs exhibit similar solvation environments in blends, except for butanol, which influences their dynamic properties. Methyl pentanoate and butanol emerge as potent candidates for green fuel integration in conventional gasoline, albeit with limited effectiveness in low-aromatic content fuel corresponding to aromatic mole fraction of 0-0.16. Introducing butyl levulinate significantly enhances valid compositions from 18% in binary blends to 70% in ternary blends, with 100% success in one of the reformulated gasoline formulations.

Predicting the autoignition behaviour of tailorable advanced biofuel blends using automatically generated mechanisms

Emerging processes such as biomass alcoholysis have the potential to provide tailorable, advanced biofuels to replace conventional fossil fuels. Knowledge of the engine-relevant behaviour for such fuels is evolving but is currently limited. Simulation tools may assist in the exploration of this behaviour but are reliant on the availability of robust, detailed kinetic mechanisms to produce accurate predictions. Automatic mechanism generation (AMG) techniques may be applied to facilitate the production of such mechanisms, as long as the utilised databases contain high-quality kinetic and thermochemical information of relevance to the functional groups of interest. To model the combustion characteristics of complex fuel blends, Reaction Mechanism Generator (RMG) is applied in this work to produce detailed ethyl (ethyl levulinate, diethyl ether, ethanol) and butyl (n‑butyl levulinate, di-n‑butyl ether, n-butanol) kinetic mechanisms. The predictive capabilities of these mechanisms are evaluated against a combination of literature data for individual components and new experimental measurements of ethyl and butyl blends. Stoichiometric blend ignition delay times are measured in a rapid compression machine at a compressed pressure of 20 bar and compressed temperatures of 645–960 K. The investigated blends are formulated to achieve a desired research octane number (blends ELV1 and BLV1) or to match physical property limits of diesel fuels (blends ELV2 and BLV2). Ethyl blend measurements show clear examples of complex low temperature oxidation behaviour, but this is not observable in the butyl cases, as the high boiling point of butyl levulinate necessitates the use of significant dilution in ignition delay experiments. The generated models show a high degree of accuracy when compared to measurements at thermodynamic conditions of relevance to engine technologies. The blending behaviour shown by the experimental measurements is also well predicted. This work highlights the importance of database additions/modifications based on low uncertainty, high quality, literature data when using AMG methods.

Novel Porous Organic Polymer Catalyst with Phosphate and Sulfonic Acid Sites for Facile Esterification of Levulinic Acid.

Biomass-derived value-added materials such as levulinic acid (LA) are favorable natural resources for producing ester-based biolubricants owing to their biodegradability, nontoxicity, and excellent metal-adhering properties. However, highly active catalysts must be developed to carry out efficient esterification of LA with aliphatic alcohols, especially long-chain aliphatic alcohols. In this study, we developed a novel porous covalent organic polymer catalyst (BPOP-SO3H) with dual acid sites, phosphate and sulfonic acid sites, for the esterification of LA. The prepared BPOP-SO3H catalyst was verified using various surface analysis techniques. BPOP-SO3H exhibited 98% LA conversion with n-butanol and 99% selectivity for butyl levulinate ester within 30 min, which is superior to that of most reported catalysts. BPOP-SO3H also showed high LA conversion and ester selectivity when other aliphatic alcohols were used. Moreover, BPOP-SO3H showed good recyclability for five consecutive cycles. We believe that incorporating a high density of acid sites into a porous polymer with a large surface area and hierarchical pores is a promising approach for developing heterogeneous acid catalysts for the production of alkyl levulinate esters from LA.

Assessment of kinetic models for the production of γ-valerolactone developed in isothermal, adiabatic and isoperibolic conditions

The use of lignocellulosic biomass as raw materials for the production of biofuels is increasing. There are several potential processes valorizing these raw materials, but the shift from lab-scale to industrial scale requires the development of reliable and robust kinetic models. Usually, these models are developed in isothermal mode, limiting their use for thermal risk assessment or pinch analysis. We developed and assessed several kinetic models for the hydrogenation of butyl levulinate to γ-valerolactone over Ru/C in different thermal modes, i.e., isothermal, isoperibolic and adiabatic modes. The reaction calorimeter Mettler-Toledo RC1 was used to perform kinetic experiments. Bayesian inference was used during the regression stage to calculate the credible intervals. The validation stage was done by a holdout method. From the regression and validation stage, we found that the non-competitive Langmuir Hinshelwood with hydrogen non-dissociation and dissociation were the most reliable models. These models can predict the kinetics of this reaction system in different thermal modes.

Kinetic modelling: Regression and validation stages, a compulsory tandem for kinetic model assessment

AbstractThe development of robust and reliable kinetic models is vital to build safe, eco‐friendly, and cost‐competitive chemical processes. Establishing kinetic models for complex chemical systems such as biomass valorization is cumbersome because the kinetic modeller must test different models and fit several experimental observables (or concentrations). Usually, in chemical reaction engineering, kinetic model assessment is based solely on the regression stage outputs. The implementation of a validation stage can aid in choosing the most reliable kinetic models, essentially in the case of complex chemical systems. We studied the solvolysis of 5‐hydroxymethylfurfural (5‐HMF) to butyl levulinate (BL) as a model reaction constituting several consecutive and parallel reaction steps. From an existing kinetic model, we created 60 synthetic runs in batch conditions. In the first part, we tested four different models with 5 degrees of noise, and we carried out the modelling on the 60 synthetic runs. In the second part, two types of holdout methods were evaluated. In the last part, cross‐validation, namely the k‐fold method, was used. We found that the 10‐fold method allowed more efficient selection results even when the noise level was high. Besides, k‐fold allows for not scarifying experimental runs and selecting the most reliable model.

Surface modified mesoporous KIT-5: A catalytic approach to obtain butyl levulinate from starch

Biomass is the only renewable organic material that has high energy content. Due to the significant amount of biomass resources, especially crop residues, the valorization of biomass to fuel or fuel additives have received more attention. In the present paper, biomass-derived butyl levulinate was prepared from starch in the presence of Al-modified mesoporous KIT-5 silica to improve its catalytic activity. Accordingly, the acidity character of KIT-5 was improved by two methods: wetness impregnation and in situ incorporation of aluminum. The essential properties of these catalysts were characterized by different techniques including N2 adsorption-desorption analysis, ICP-OES, FT-IR, and Pyridine-FT-IR analyses, XRD, SEM, TEM. A series of important parameters influencing the reaction yield was thoroughly investigated. Under the optimized conditions (230 °C, 10 h, 30 mg catalyst, and 70 mg starch), 31% n-butyl levulinate yield and 74% starch conversion were obtained, respectively. Finally, the selected catalyst was regenerated and reused in starch valorization reaction for four successive runs.

Production of butyl levulinate from the solvolysis of high-gravity fructose over heterogeneous catalyst: In-depth kinetic modeling

Butyl levulinate (BL) is a promising biofuel and oxygenated fuel additive. Among the various ways of producing this ester, the alcoholysis of simple sugars has more advantages than the traditional esterification of levulinic acid, as it requires fewer processing units in post-treatment operations, making it more sustainable in terms of cost, even on a large industrial scale. Several studies on the nature of the catalyst or process intensification have been addressed in the literature. However, there are no in-depth studies on the development of a kinetic model, particularly with a high gravity approach, i.e. high initial concentration of simple sugars. Condition in which the complexity is due to the fact that the development of a model cannot avoid the inclusion of the kinetics of dissolution of fructose from solid to liquid. In this study, the solvolysis of fructose to butyl levulinate on a solid acid catalyst, Amberlite IR120, was experimentally investigated at high initial concentrations, and different kinetic models were developed, including the dissolution and degradation kinetics of fructose, tested and validated at different initial fructose concentrations, temperatures and catalyst loadings. The Akaike information criterion and hold-out method assessed the most reliable developed model.

The solvent-free hydrogenation of butyl levulinate to γ-valerolactone and 1,4-pentanediol over skeletal Cu-Al-Zn catalyst

γ-valerolactone (GVL) is a sustainable chemical, which can be obtained by hydrogenation of levulinic acid (LA) and levulinate. Herein, we reported a solvent-free hydrogenation of butyl levulinate (BL) to GVL and 1,4-pentanediol (1,4-PDO) over a skeletal Cu-Al-Zn catalyst. The skeletal Cu-Al-Zn catalyst was prepared from Devarda's alloy by alkali leaching and the catalyst was characterized by different analysis methods. The aluminum in the Devarda's alloy was dissolved by sodium hydroxide in the leaching process and many active Cu atoms were generated on the catalyst surface and the skeletal Cu-Al-Zn exhibited many micrometer-scale irregular particles with rough surface. The skeletal Cu-Al-Zn catalyst showed the excellent performance in the solvent-free hydrogenation of BL to GVL under constant hydrogen pressure (5 wt% catalyst loading, 180°C, 6 MPa of H2, 6 h): the LA conversion was 100%, the GVL yield was 74.75% and the 1,4-PDO yield was 25.63%. Moreover, the catalyst showed stable performance and it was reusable up to 5 times without apparent loss of activity. A stable hydrogen pressure with Zn would suppressed the dehydration of 1,4-PDO.

Insights on butyl levulinate bio-blendstock: From model sugars to paper mill waste cellulose as feedstocks for a sustainable catalytic butanolysis process

Butyl levulinate (BL) represents a novel diesel bio-blendstock and a versatile intermediate and solvent. The one-pot acid-catalyzed conversion of C6-feedstocks, employing n-butanol as the solvent/reagent, implies the upgrading of low-cost or, even better, waste biomasses for developing prompt process intensification. In this paper, the one-pot butanolysis process has been studied, moving from model glucose and microcrystalline cellulose to a waste cellulose feedstock deriving from a real papermaking process. The performances obtained with this waste biomass have been optimized, achieving BL yields up to 46 mol %, adopting a high-gravity approach, in the presence of diluted sulfuric acid as the catalyst. The optimization was carried out also in the perspective of minimizing the alcohol etherification to dibutyl ether, and the feedstock carbonization to char by-product, whose characterization was performed to identify its suitable applications. The combined production of both BL as a valuable bio-fuel and char as an exploitable carbonaceous bio-material can pave the way to the development of the one-pot butanolysis of real cellulosic or lignocellulosic biomasses in an environmentally sustainable and integrated perspective, in agreement with the principles of the circular bio-economy.

Reaction enthalpies for the hydrogenation of alkyl levulinates and levulinic acid on Ru/C– influence of experimental conditions and alkyl chain length

The development of process flow diagrams requires knowledge of reaction enthalpy for pinch analysis and thermal risk assessment. Such information is missing for some biomass processes, such as the production of γ-valerolactone (GVL) from the hydrogenation of levulinic acid or alkyl levulinate. To fill this gap, this manuscript describes a detailed calorimetric study on the hydrogenation of levulinic acid (LA), methyl levulinate (ML), ethyl levulinate (EL), propyl levulinate (PrL), butyl levulinate (BL) and pentyl levulinate (PeL) over Ru/C. This reaction system occurs through a two-step pathway with a domino hydrogenation/cyclization sequence. The cyclization step (lactonization) was found to be endothermic and was evaluated by a Tian-Calvet C80 micro-calorimeter, whereas the hydrogenation step was found to be exothermic and was tracked by a RC1 Mettler Toledo High-Pressure calorimeter. It was verified that reaction enthalpy is independent of reaction temperature (in the operating conditions used in this work), levulinate concentration and solvent (levulinate, corresponding alcohol or GVL). It was also found that reaction enthalpy for both steps did not depend linearly on alkyl chain length.

Thermal Stability for the Continuous Production of γ-Valerolactone from the Hydrogenation of N-Butyl Levulinate in a CSTR

γ-valerolactone can be a game-changer in the chemical industry because it could substitute fossil feedstocks in different fields. Its production is from the hydrogenation of levulinic acid or alkyl levulinates and can present some risk of thermal runaway. To the best of our knowledge, no studies evaluate the thermal stability of this production in a continuous reactor. We simulated the thermal behavior of the hydrogenation of butyl levulinate over Ru/C in a continuous stirred-tank reactor and performed a sensitivity analysis. The kinetic and thermodynamic constants from Wang et al.’s articles were used. We found that the risk of thermal stability is low for this chemical system.

High Dispersion of Platinum Nanoparticles over Functionalized Zirconia for Effective Transformation of Levulinic Acid to Alkyl Levulinate Biofuel Additives in the Vapor Phase

In recent years, functionalized metal oxides have been gaining popularity for biomass conversion to fuels and chemicals due to the global energy crisis. This study reports a novel catalyst based on noble metal immobilization on functionalized zirconia that has been successfully used in the production of biofuel alkyl levulinates (ALs) from lignocellulosic biomass-derived levulinic acid (LA) under vapor-phase. The wet impregnation method was used to immobilize Pt-metal nanoparticles on zirconia-based supports (silicotungstic acid zirconia, STA-ZrO2; sulfated zirconia, S-ZrO2; and tetragonal zirconia, t-ZrO2). A variety of physicochemical techniques were used to characterize the prepared catalysts, and these were tested under atmospheric pressure in continuous flow esterification of LA. The order of catalytic activity followed when ethyl levulinate was produced from levulinic acid via esterification: Pt/STA-ZrO2 ≫ Pt/S-ZrO2 ≫ Pt/t-ZrO2. Moreover, it was found that ALs synthesis from LA with different alcohols utilizing Pt/STA-ZrO2 catalyst followed the order ethyl levulinate ≫ methyl levulinate ≫ propyl levulinate≫ butyl levulinate. This work outlines an excellent approach to designing efficient catalysts for biofuels and value-added compounds made from biomass.

A straightforward preparation of levulinic esters from biorenewable levulinic acid using methanesulfonic acid supported on silica gel (MSA-SG) as an efficient heterogeneous catalyst

The present work reports methanesulfonic acid supported on silica gel (MSA-SG) as an inexpensive heterogeneous solid acid catalyst for the high-yielding production of various alkyl levulinates from biomass-derived levulinic acid. The catalyst was characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX). The reactions were conducted in a batch-type glass pressure reactor under conventional heating. The esterification reaction was optimized on temperature, duration, and catalyst loading. The optimized reaction conditions (120 °C, 8 h, 8 wt% MSA-SG) afforded methyl- to butyl levulinate in excellent isolated yields (≥90 %). The catalyst was filtered, and the products were purified by simply evaporating the excess alcohol reagent.