Methyl Lactate Research Articles

Chemical Degradation of End-of-Life Poly(lactic acid) into Methyl Lactate by a Zn(II) Complex.

The catalyzed methanolysis of end-of-life poly(lactic acid) (PLA) products by an ethylenediamine Zn(II) complex to form biodegradable methyl lactate was studied experimentally at 70, 90, and 110 °C. The PLA samples consisted of typical consumer waste materials, including a cup, a toy, and a three-dimensional (3D) printing material. High selectivities and yields (>94%) were possible depending on temperature and reaction time. Additionally, and to develop a predictive kinetic model, kinetic parameters (pre-exponential factor and activation energies) of the PLA transesterification reaction were first obtained from virgin PLA. These parameters were subsequently used to estimate the conversion of PLA, selectivity, and yield of methyl lactate after 1 and 4 h of the reaction, and the results were compared with the experimental values of the end-of-life PLA. Despite the presence of unknown additives in the PLA waste material and uncontrolled particle size, the model was able to predict the overall conversion, selectivity, and yield to an average deviation of 5, 7, and 12%, respectively. A greater agreement between the model and experimental values is observed for the higher temperatures and the longer reaction time. Larger deviations were observed for the PLA toy, which we attribute to the presence of additives, since despite its lower molecular weight, it possessed a higher structural strength.

Conversion of sugars to methyl lactate with exfoliated layered stannosilicate UZAR-S4

Biomass has been shown as an alternative to fossil fuels for obtaining chemicals. In this work, the transformation of sugars into methyl lactate (ML) at 160 °C was carried out using the layered stannosilicate UZAR-S3 (University of Zaragoza-solid number 3) and the delaminated material UZAR-S4 (University of Zaragoza-solid number 4) obtained from its exfoliation. The exfoliation of UZAR-S3 to UZAR-S4 increased the accessibility of the compounds to the catalytic sites and the medium-strength acidity. Thus, the yield to ML for sucrose transformation increased from 8% for UZAR-S3 to 49.9 % for UZAR-S4. In the reusability tests, the UZAR-S4 catalyst was characterized before and after reaction by several techniques such as X-ray diffraction, thermogravimetry analysis, scanning electronic microscopy, energy dispersive X-ray spectroscopy and nitrogen adsorption. A deactivation of the catalyst was observed, which was related to carbonaceous deposits that decreased the specific surface area and the pore volume of the catalyst.

Kinetics of Methyl Lactate Formation from the Transesterification of Polylactic Acid Catalyzed by Zn(II) Complexes.

The kinetics of the transesterification of polylactic acid (PLA) with methanol to form methyl lactate catalyzed by Zn(II) complexes was studied experimentally and numerically. The complexes, Zn(1Et)2 and Zn(2Pr)2, were synthesized from ethylenediamine and propylenediamine Schiff bases, respectively. The temperature range covered was 313.2–383.2 K. An increase in the reaction rate with the increase in temperature was observed for the Zn(1Et)2-catalyzed reaction. The temperature relationship of the rate coefficients can be explained by a linear Arrhenius dependency with constant activation energy. The kinetics of Zn(2Pr)2, on the other hand, is only explained by non-Arrhenius kinetics with convex variable activation energy, resulting in faster methyl lactate production rates at 323.2 and 343.2 K. The formation of a new catalyst species, likely through reaction with protic reagents, appears to promote the formation of intermediate complexes, resulting in the nonlinear behavior. Stirring speed induced the stability of the intermediate complexes. Contrary to Zn(1Et)2, Zn(2Pr)2 was susceptible to the presence of air/moisture in solution. The kinetic parameters were obtained by fitting the experimental data to the mass and energy balance of a consecutive second step reversible reaction taking place in a jacketed stirred batch reactor. For the case of Zn(2Pr)2, the activation energy was fitted to a four-parameter equation. The kinetic parameters presented in this work are valuable for the design of processes involving the chemical recycling of PLA into green solvents.

One-pot chemo-catalytic conversion of glucose to methyl lactate over In/γ-Al2O3 catalyst

The huge demand of lactic acid in widespread applications has significantly impelled the development of cost-effective strategy for the production of lactic acid, in particular its derivative (methyl lactate, MLA) due to the simpler separation and purification process. Herein, in this work, we developed a series of robust but simple In/γ-Al2O3 catalysts with different In loadings. The results indicated that In doping obviously increased the amount of mid-strong acid on the catalyst, which significantly facilitated the selective cleavage of C3-C4 bond in C6 sugar (rate-controlling step), as well as the next esterification reaction. 12-In/γ-Al2O3 catalyst, with the most mid-strong acid sites, exhibited the best catalytic activity for MLA production from renewable sugars in methanol solvent. The addition of only a small amount of water could accelerate sugar dissolution in methanol solvent, and alkali (K2CO3) addition further promoted C3-C4 cleavage, thus yielding more C3 intermediates. When dihydroxyacetone and pyruvaldehyde intermediates were employed as feedstock, as high as 86.0 % and 98.0 % yields of MLA could be obtained, respectively. Even in the case of glucose and fructose as feedstock, MLA yields were up to 49.0 % and 54.2 %, respectively, under the optimized conditions. This work might provide a potential approach for the synthesis of lactic acid and its derivatives with low production cost.

Fabrication of Hierarchical Sn-Beta Zeolite as Efficient Catalyst for Conversion of Cellulosic Sugar to Methyl Lactate

In this work, BEA-type hierarchically structured stannosilicate zeolite Sn-Beta-H was developed, which involved alkali-induced degradation of all-silica Beta (Si-Beta) and self-assembly of the resu...

Vapour-phase conversion of methyl lactate into lactide over TiO2/SiO2 catalyst at the lowered pressure

Now polylactide (PLA) widely use as biodestructive packing material. Usually monomeric lactide produce from lactic acid. Also, methyl (ethyl) lactate could be used for lactide obtaining via its vapour-phase condensation on TiO2/SiO2 catalyst at 2600C in N2 carrier-gas flow. However, at that it is necessary to heat carrier-gas to the reaction temperature. In this communication the results on methyl lactate vapour condensation into lactide with the lowered pressure of 100-150 mbar, without carrier-gas, are presented. Supported TiO2/SiO2 catalyst with 5 wt.% titania content has been prepared by impregnation of silica with Ti(OC4H9)4. After calcination at 5000C prepared catalyst has amorphous mesoporous structure with 335 m2/g surface area and 0.83 сm3/g pore volume. The catalytic experiments were performed in such way. Liquid methyl lactate was dosed into the evaporator (2500C) and further in the flowing reactor (2600C) under pressure of 100 mbar that produced by vacuum pump. Load on a catalyst was varied from 25 to 55 mmol ML/(gcath). Cooled product was analyzed on Agilent 7820A chromatograph and NMR Bruker Avance-400 spectrometer. It was shown that TiO2/SiO2 catalyst provide 74% selectivity towards lactide at 50-53% methyl lactate conversion with lactide productivity of 7.8 mmol L/(gcath) at 2600C/100 mbar. The catalyst stable work is more 80 h. Main impurities are methyl lactoillactate, 1-methoxyethanol and 1,1-dimethoxyethane.

Conversion of fructose into methyl lactate over SnO2/Al2O3 catalystin flow regime

In recent years, numerous researchers have focused on the development of catalytic methods for processing of biomass-derived sugars into alkyl lactates, which are widely used as non-toxic solvents and are the starting material for obtaining monomeric lactide. In this work, the transformation of fructose into methyl lactate on Sn-containing catalyst in the flow reactor that may be of practical interest was studied. The supported Sn-containing catalyst was ob-tained by a simple impregnation method of granular γ-Al2O3. The catalytic ex-periments were performed in a flow reactor at temperatures of 160-190 °C and pressure of 3.0 MPa. The 1.6-9.5 wt.% fructose solutions in 80% aqueous methanol were used as a reaction mixture. It was found that addition to a reac-tion mixture of 0.03 wt.% potassium carbonate leads to the increase in selec-tivity towards methyl lactate on 15% at 100% conversion of fructose. Prod-ucts of the target reaction С6Н12О6 + 2СН3ОН = 2С4Н8О3 + 2Н2О were ana-lyzed using 13C NMR method. The following process conditions for obtaining of 65 mol% methyl lactate yield at 100% fructose conversion were found: use of 4.8 wt.% fructose solution in 80% methanol, 180 °С, 3.0 МПа and a load on catalyst 1.5 mmol C6H12O6/mlcat/h at contact time of 11 minutes. The cata-lyst productivity is 2.0 mmol C4H8O3/mlcat/h and the by-productі are 1,3-dihydroxyacetone dimethyl acetal (20%) and 5-hydroxymethylfurfural (10%). It should be noted that a racemic mixture of L- and D-methyl lactates has been obtained by conversion of D-fructose on the SnO2/Al2O3 catalyst. The SnO2/Al2O3 catalyst was found to be stable for 6 h while maintaining full fruc-tose conversion at 55–70% methyl lactate selectivity. After regeneration the catalyst completely restores the initial activity.

Mono- and dimeric zinc(ii) complexes for PLA production and degradation into methyl lactate – a chemical recycling method

A series of well-defined mono- and dimeric Zn(ii)-complexes were prepared and fully characterised by X-ray crystallography and NMR spectroscopy.

Promotion effect of Mg on a post-synthesized Sn-Beta zeolite for the conversion of glucose to methyl lactate

Mg-Sn-Beta zeolites with different Mg/Sn molar ratios were prepared from the parent deAl-Beta by a coimpregnation method. It shows higher selectivity for the conversion of glucose to methyl lactate than post-synthesized Sn-Beta.

Seed-assisted hydrothermal synthesis of Sn-Beta for conversion of glucose to methyl lactate: effects of the H2O amount in the gel and crystallization time

The crystallization rate, morphology, Sn state and microenvironment and catalytic performance for the conversion of glucose to methyl lactate of Sn-Beta are significantly affected by the water amount in the synthesis gel and the crystallization time.

Methyl lactate production from levoglucosan by using Sn‐Beta and H‐Beta catalysts

AbstractBACKGROUNDFast pyrolysis of lignocellulosics has provided an abundant sugar source for production of value‐added chemicals, and levoglucosan is the most representative sugar in pyrolysis liquid (bio oil). This paper explored the potential for producing methyl lactate from levoglucosan by employing the mixed catalysts of zeolite tin beta (Sn‐Beta) and zeolite hydrogen beta (H‐Beta).RESULTSUnder the optimal conditions (at 200 °C and mixed catalysts with H‐Beta:Sn‐Beta ratio of 1:5), the yield of methyl lactate obtained from levoglucosan conversion was as high as 35%. And the yield was comparable to that of methyl lactate obtained from glucose conversion under the similar conditions (at 200 °C and pure Sn‐Beta). In order to investigate the reason, a contrasting experiment with glucose as substrate also was carried out with the mixed catalysts. The results indicated that during the levoglucosan conversion process, ‘the methanolysis of levoglucosan’ was likely to compete with ‘the dehydration of glucose’ for the Brønsted acid sites of H‐Beta. In addition, the catalytic functions of H‐Beta and Sn‐Beta, and the reaction pathway were deeply investigated through tracking and comparing the conversion of levoglucosan over mixed H‐Beta/Sn‐Beta and over pure Sn‐Beta catalysts, respectively.CONCLUSIONThe appropriately lower ratio of H‐Beta:Sn‐Beta and relatively higher temperature were favorable for the reaction. H‐Beta containing Brønsted acid could remarkably accelerate the conversion of levoglucosan and methyl‐glucosides to glucose. Sn‐Beta containing Lewis acid mainly promoted the retro‐aldol condensation of glucose and formation of methyl lactate. © 2019 Society of Chemical Industry

Conversion of Dihydroxyacetone to Methyl Pyruvate Catalyzed by Hybrid Molecular Sieves at Low Temperature: A Strategy for the Green Utilization of Glycerol

Methyl pyruvate (MPA) was synthesized from dihydroxyacetone (DHA), the oxidation product of glycerol, over Sn-β and TS-1 hybrid molecular sieves at low temperature. Sn-β and TS-1 provide the active sites for conversion of DHA to methyl lactate (MLA) and oxidation of MLA to MPA, respectively. Synergism of Lewis acid sites on Sn-β and TS-1 realize the production of MPA from DHA. After optimization, 71% yield of MPA can be obtained under 50 °C. This is the first report for the synthesis of MPA from DHA directly.

Synthesis of methyl lactate from cellulose catalyzed by mixed Lewis acid systems

Lactic acid (LacA) is a potential building block in biomass refinery based on lignocellulose. Herein, we report three-component Lewis acid catalyst systems comprised of metal triflates, In chloride, and Sn chloride for the direct synthesis of methyl lactate (MeLac) from cellulose in methanol. These three catalyst species cooperatively catalyzed this reaction; the metal triflates depolymerized cellulose to sugars, which was converted to trioses by retro-aldol reaction with In chloride, followed by their isomerization with Sn chloride to give MeLac. Among the metal triflates, Sm triflate was the most effective, with which MeLac was formed in 45% yield. Ball-milling pretreatment of cellulose in the presence of methanol increased the yield of MeLac to 64%.

Selective Degradation of End‐of‐Life Poly(lactide) via Alkali‐Metal‐Halide Catalysis

AbstractThe recycling of poly(lactide) (PLA) is studied. Using methanol and alkali‐metal‐halides as catalyst, PLA is degraded to produce methyl lactate, which is a suitable chemical for the regeneration of PLA. An excellent degree of degradation (conversions: >99%, yields: >99%) is achieved in less than 20 min utilizing microwave heating. Remarkably, PLA goods are successfully converted into methyl lactate.

Utilization of One Novel Microbial Esterase WDEst9 in the Kinetic Resolution of (S)-Methyl 2-chloropropionate and (S)-Ethyl 2-chloropropionate

One novel microbial esterase WDEst9 from Dactylosporangium aurantiacum subsp. Hamdenensis NRRL 18085 was functionally characterized and the results demonstrated that the enantio-preference of WDEst9 was oppo-site to that of three other microbial esterases(BSE01701, PHE14 and Bae02030) in the kinetic resolution of racemic methyl lactate. We further investigated the potential of esterase WDEst9 in the kinetic resolution of both (±)-methyl 2-chloropropionate and (±)-ethyl 2-chloropropionate. The enantio-preference of WDEst9 was also interestingly op-posite to that of esterases EST12-7 and EstC10, and generated (S)-methyl 2-chloropropionate and (S)-ethyl 2-chloropropionate with high enantiomeric excess(both e.e. >98%) and high yield after many iterations of process optimization. Through genome mining, microbial esterase WDEst9 was characterized to be a novel esterase which may provide valuable complementary enantio-selectivity and possesses very good potential in the kinetic resolution of high value-added chiral chemicals.

Babao Dan induces gastric cancer cell apoptosis via regulating MAPK and NF-κB signaling pathways.

ObjectiveThe objective was to further investigate apoptosis induction by Babao Dan (BBD), which supports its anti-tumor mechanisms, using two human gastric cancer cell lines (AGS and MGC80-3).MethodsAfter treatment with various BBD concentrations, cell viability and cytotoxic effects were investigated using methyl thiazolyl tetrazolium (MTT) and lactate dehydrogenase (LDH) assays, respectively. The following indicators of cell apoptosis were evaluated: Annexin V-APC staining, caspase-3/-8/-9 activation, and mitochondrial membrane potential loss. Apoptosis-related protein levels (including Bcl-2-associated X protein [Bax], B-cell CLL/lymphoma 2 [Bcl-2], factor associated suicide [Fas], and Fas ligand [FasL]) were determined by western blot. The following multi-pathway factors were also assessed: p-ERK1/2, p-JNK, p-p38, and p-NF-κB.ResultsThe MTT and LDH assays both demonstrated increased BBD cytotoxicity. BBD induced cell apoptosis by stimulating caspase-3/-8/-9 activity and destroying the mitochondrial membrane potential. BBD also regulated key factor expression levels including Bcl-2, Bax, Fas, and FasL and down-regulated protein phosphorylation via the MAPK and NF-κB pathway.ConclusionsThe possible anti-tumor mechanism is that BBD induces apoptosis via the MAPK and NF-κB signaling pathways.

Zn-Acetate-Containing ionic liquid as highly active catalyst for fast and mild methanolysis of Poly(lactic acid)

Zn-acetate-containing ionic liquid (IL), 1-butyl-3-methylimidazolium acetate-promoted zinc acetate (2[Bmim][OAc]-Zn(OAc)2) was synthesized and used to catalyze the methanolysis of poly(lactic acid) (PLA). In this study, it was found that not only the methanolysis condition was milder compared with reported literatures, but also the high conversion of PLA and the yield of product methyl lactate were obtained when this Zn-acetate-containing IL was used as catalyst. The influences of technological parameters on PLA methanolysis were investigated and the optimum reaction conditions were obtained. Under the following conditions of catalyst (n[Bmim][OAc]:nZn(OAc)2 = 2.0:1, 0.04 g), n(CH3OH):n(PLA) = 5.0:1 and PLA (4.0 g) at 110 °C for 2.0 h, the PLA conversion and the methyl lactate yield were over 97% and 92%, respectively. Compared with the conventional ILs and other traditional catalysts, this Zn-acetate-containing IL exhibited excellent catalytic performance and the advantage of small dosage. The IL could be reused for 5 times, both FT-IR and TGA results indicated that the spectra of the reused IL were almost similar to those of the fresh one. Moreover, a possible mechanism of PLA methanolysis catalyzed by [Bmim][OAc]-Zn(OAc)2 was proposed through the experiments. The reaction kinetics was also investigated, and the results showed that it was a pseudo-first order kinetic reaction with an activation energy of 20.96 kJ/mol.

Green preparation process using methyl lactate for cellulose-acetate-based nanofiltration membranes

Cellulose acetate (CA) membranes were prepared via phase inversion using methyl lactate as a green solvent and 2-methyltetrahydrofuran as a green co-solvent with or without evaporation period prior to immersion of the cast polymer solution in the coagulation bath. The membrane morphologies were characterized using scanning electron microscopy and the membrane performance was screened using aqueous rose bengal (RB) or MgSO4 feed solutions. With CA-concentration in the casting solution increasing from 8 to 20 wt%, RB-rejection increased from 31.1% to 99.5%, while permeance decreased from 32.0 to 2.4 L/m2·h·bar. CA-membranes cast from a 10 wt% polymer solution had a RB-rejection higher than 92.0% with good permeance around 3.5 L/m2·h·bar at low co-solvent concentration (10 wt%). However, with increased co-solvent concentration (i.e. 30–50 wt%), both rejection and permeance surprisingly decreased, regardless evaporation time. For membranes cast from a 20 wt% polymer solution, RB-rejection remained around 99% and permeance decreased with increasing co-solvent concentration in the casting solution. MgSO4 rejection was around 93.0% for membranes cast from a 20 wt% polymer solution with 10 wt% co-solvent without evaporation (at a flux of 1.0 L/m2·h·bar) and 96.5% with evaporation at a flux of 1.3 L/m2·h·bar.

Comparison of a Genetic Algorithm Variable Selection and Interval Partial Least Squares for quantitative analysis of lactate in PBS.

Blood lactate is an important biomarker that has been linked to morbidity and mortality of critically ill patients, acute ischemic stroke, septic shock, lung injuries, insulin resistance in diabetic patients, and cancer. Currently, the clinical measurement of blood lactate is done by collecting intermittent blood samples. Therefore, noninvasive, optical measurement of this significant biomarker would lead to a big leap in healthcare. This study, presents a quantitative analysis of the optical properties of lactate. The benefits of wavelength selection for the development of accurate, robust, and interpretable predictive models have been highlighted in the literature. Additionally, there is an obvious, time- and cost-saving benefit to focusing on narrower segments of the electromagnetic spectrum in practical applications. To this end, a dataset consisting of 47 spectra of Na-lactate and Phosphate Buffer Solution (PBS) was produced using a Fourier transform infrared spectrometer, and subsequently, a comparative study of the application of a genetic algorithm-based wavelength selection and two interval selection methods was carried out. The high accuracy of predictions using the developed models underlines the potential for optical measurement of lactate. Moreover, an interesting finding is the emergence of local features in the proposed genetic algorithm, while, unlike the investigated interval selection methods, no explicit constraints on the locality of features was imposed. Finally, the proposed genetic algorithm suggests the formation of α-hydroxy-esters methyl lactate in the solutions while the other investigated methods fail to indicate this.

Facile synthesis of DBU-based protic ionic liquid for efficient alcoholysis of waste poly(lactic acid) to lactate esters

Several DBU-based protic ionic liquids were facilely synthesized, they were successfully used as solvents and catalysts for alcoholysis of poly(lactic acid) (PLA) to yield lactate esters. The structure of ionic liquids and reaction parameters were optimized. Using [HDBU][AA] as the catalytic medium, which was composed by a 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) cation and an acetate anion, the PLA could be completely depolymerized with a 91% methyl lactate yield under the conditions of 100 °C, 5 mol% catalyst loading for 5 h. The effect of alcohol structures on the catalytic behaviors was studied, and good to excellent product yields were obtained. Moreover, the developed [HDBU][AA] showed excellent recyclability and structure stability. A possible reaction mechanism concerning the synergistic effect of the anion-cation ions was proposed. The DBU-based protic ionic liquids presented herein are low-cost and one-step synthesized, exhibiting great potential as green and efficient platform for direct and selective alcoholysis of PLA.