Methyl Lactate Yield Research Articles

Catalytic recycling of polylactic acid over zirconium phosphate supported WOx active sites

Chemical upcycling of end-of-life plastics is an economically and environmentally feasible way to tackle plastics crisis. Among them, methanol alcoholysis of polylactic acid (PLA) is a promising approach, which can produce methyl lactate (MLA) that can be further converted to lactide to achieve a sustainable development. In this work, a series of WOx/ZrP catalysts with WOx active sites in low coverage and high surface area were synthesized via anchoring WOx species on the surface of zirconium phosphate (ZrP). Characterizations indicated that the strong interaction between WOx and ZrP promoted the formation of WOx active sites in low coverage. In particular, 10 %WOx/ZrP catalyst was highly active and stable for the alcoholysis of PLA plastics under mild conditions due to the abundant WOx active sites and strong acidity. The yield of MLA over 10 %WOx/ZrP catalyst reached 94.5 % within 4 h at 160 °C, which was superior to the performance of traditional solid acids (α-ZrP, HZSM-5, Hβ and Amberlyst-45). In addition, 10 %WOx/ZrP was versatile for the alcoholysis of discarded PLA-based products and could be recycled at least five times. The prominent performance of 10 %WOx/ZrP catalyst and the possible reaction mechanism were discussed.

Conversion of sugars into methyl lactate over poly (ionic liquid)s functionalized Sn/beta zeolites

Methyl lactate (MLA) is a versatile high value platform chemical prepared from biomass carbohydrates, with widely application in the pharmaceutical, food, pesticide, and cosmetics. The current study presented a one-pot catalytic conversion of sugars to MLA over poly (ionic liquid)s functionalized Sn/Beta zeolites under mild conditions. The Sn/Beta zeolites were prepared by an impregnation method, followed by modification with poly (vinyl imidazole) ([PVIM]) via an in-situ free radical polymerization method. Dosages of polymer and Sn, calcination temperature, reaction temperature, catalyst amount, substrate concentration, and reaction times were optimized. Results showed that an MLA yield of 61.4 % was obtained over 3[PVIM]-Sn/Beta with complete conversion of fructose at 140 °C for 8 h. The physicochemical properties were characterized by XRD, BET, FTIR, CO-DRIFTS, NH3-TPD and pyridine-FTIR analysis, indicating the coexistence of Lewis and Brønsted acid sites. Finally, a possible reaction mechanism was proposed that the weak Lewis acidity of imidazole rings of [PVIM] effectively regulated the local microenvironment of active sites, thus promoting the interaction of the active sites with electronegative oxygens of sugars. This study can provide as a reference for the development of solid acid catalysts for the catalytic conversion of biomass to platform chemicals.

One-pot catalytic conversion of sugars to methyl lactate over acid-base bifunctional Sn/MgO catalysts

Alkyl lactates represent such green added-value chemicals that commonly used as biodegradable green solvents, detergents, pharmaceutical intermediates et al. Catalytic conversion of carbohydrates to methyl lactate (MLA) is a representative way for high-value utilization of biomass and the key lies in the development of highly efficient catalysts. In methanol, strong acid or alkaline catalysts are usually used under high temperature and high pressure, suffering from problems such as low selectivity, high cost or contamination of environment. This study aims to develop an acid-base bifunctional heterogeneous catalyst for the one-pot conversion of sugars to MLA under mild conditions. Sn/Mg composite oxides was synthesized by a coprecipitation method and further modified by poly (vinyl imidazole) ([PVIM]) to tune the hydrophilicity. Effect of polymer and Sn amount, calcination temperature, reaction temperature, catalyst dosage, and substrate concentration were investigated. The acid-base properties were characterized by NH3-TPD, pyridine-FTIR and CO2-TPD analysis. It was found that the presence of medium acid sites and medium base sites played an important role to the cascade reactions of carbohydrates to MLA. An optimum MLA yield of 55.4% was achieved over 10[PVIM]-5Sn/MgO (0.05 g) with complete conversion of glucose (28 mM) at 140 ℃, 2 MPa N2 for 10 h. The reaction conditions are mild and no strong acid or strong base catalyst is required. Furthermore, a possible reaction mechanism was proposed that the introduction of [PVIM] effectively regulated the local microenvironment of active sites and the acid base synergism greatly promoted the retro-aldol condensation, dehydration and hydrogen transfer reactions during the conversion of glucose to MLA.

Glucose conversion process to methyl lactate catalyzed by SnCl4-based homogeneous catalysis

Biomass is a renewable alternative to fossil fuels and a valuable source of chemicals. In this study, a facile and efficient method was established to improve the selectivity of methyl lactate (MLA) for the homogeneous Lewis acid catalyzed chemical conversion of glucose and methanol. The effects of catalyst dosage, reaction temperature, and reaction time were systematically investigated, with an emphasis on the variation trends of MLA and other by-products. Through process optimization, the best catalyst molar ratio was 0.075 to 0.1, the reaction temperature was 170 to 180 °C, and the reaction time was 3 h. Under these conditions, the conversion of glucose in methanol exceeded 98%, and the yield of MLA was greater than 40%.

The role of aluminum in Sn-Al-beta zeolite catalyzing the conversion of glucose to methyl lactate

The preparation of H-Beta zeolites with different Si/Al ratios (Si/Al=14, Si/Al=288) was obtained by desiliconization and dealumination. Subsequently, Sn-Al-Beta catalysts were prepared by tin grafting and used for the conversion of glucose to methyl lactate. The results indicate that the yield of methyl lactate from the catalyst obtained using the parent H-beta synthesis with a high Si/Al ratio is higher than that of methyl lactate from the parent catalyst with a low initial Si/Al ratio. And the maximum methyl lactate yield of 46.66% was achieved on Sn-Al-Beta (DSi-277). In contrast, the yield of methyl lactate on Sn-Al-Beta (DAl-493) was 24.54%. Results from spectroscopic analysis and probe molecular FTIR indicated that the post-synthesis process altered the structure of the zeolite, which changed its aluminum concentration and existence form (1.8ppm chemical shift), Additionally, when the aluminum interacted with the Sn that had been added to the zeolite, it encouraged the Sn transformation to the high energy state and created the weaker Lewis acid site, as well as more effective action to improve reaction yield.

Improving the methyl lactate yield from glucose over Sn–Al-Beta zeolite by catalyst promoters

Sn–Al-Beta zeolite was prepared through a hydrothermal method and further modified by alkali and alkaline earth (e.g. Sr and Ba) metals not practically altering the textural properties of the catalyst. The catalytic materials were tested in glucose transformation to methyl lactate in a batch reactor at 180 °C allowing to correlate catalytic activity and selectivity with the strength and type of acid sites. The results showed that by suppressing the Brønsted acidity of the modified catalyst with different promoters the yield of methyl lactate can be increased from ca. 20% to over 50%.

The important role of weak Brønsted acid site of Sn-β in conversion of sucrose to methyl lactate

Sucrose is an abundant, cheap and sustainable substrate for producing high value-added chemicals. In this work, the role of weak Brønsted (B) acid site of Sn-β zeolite was revealed in sucrose conversion to methyl lactate (MLA). Sn-β zeolites were prepared by post-synthesis and hydrothermal synthesis in F‒ media and modified by Mg2+ to tune the B acidity. The acidity of the zeolites was characterized by FT-IR spectroscopy of pyridine/CD3CN adsorption and hydroxyl region. Their catalytic performance for sucrose conversion to MLA in methanol indicates that weak B acid sites of silanols are indispensible for breaking the glycosidic bond of sucrose, so the highest MLA yield was obtained over the postsynthesized Mg-Sn-β-P with moderate amount of weak B acid sites of silanols, strong L acid sites and no strong B acid sites, which juggled the alcoholysis/hydrolysis of sucrose and the retro-aldol of C6 monosaccharide to MLA, and at the same time inhibited the dehydration side-reaction.

Generation and nature of water-tolerant Lewis acid sites in InxSn10−xOy/Al2O3 catalysts as active centers for the green synthesis of methyl lactate from glucose

The improvement of methyl lactate yield was achieved by constructing water-tolerant Lewis acid sites, which were generated by reducing hydroxyl groups and increasing coordinatively unsaturated sites.

High-Pressure Depolymerization of Poly(lactic acid) (PLA) and Poly(3-hydroxybutyrate) (PHB) Using Bio-Based Solvents: A Way to Produce Alkyl Esters Which Can Be Modified to Polymerizable Monomers.

The polyesters poly(lactic acid) (PLA) and poly(3-hydroxybutyrate) (PHB) used in various applications such as food packaging or 3D printing were depolymerized by biobased aliphatic alcohols-methanol and ethanol with the presence of para-toluenesulphonic acid (p-TSA) as a catalyst at a temperature of 151 °C. It was found that the fastest depolymerization is reached using methanol as anucleophile for the reaction with PLA, resulting in the value of reaction rate constant (k) of 0.0425 min-1 and the yield of methyl lactate of 93.8% after 120 min. On the other hand, the value of constant k for the depolymerization of PHB in the presence of ethanol reached 0.0064 min-1 and the yield of ethyl 3-hydroxybutyrate was of 76.0% after 240 min. A kinetics study of depolymerization was performed via LC-MS analysis of alkyl esters of lactic acid and 3-hydroxybutanoic acid. The structure confirmation of the products was performed via FT-IR, MS, 1H NMR, and 13C NMR. Synthesized alkyl lactates and 3-hydroxybutyrates were modified into polymerizable molecules using methacrylic anhydride as a reactant and potassium 2-ethylhexanoate as a catalyst at a temperature of 80 °C. All alkyl esters were methacrylated for 24 h, guaranteeing the quantitative yield (which in all cases reached values equal to or of more than 98%). The methacrylation rate constants (k') were calculated to compare the reaction kinetics of each alkyl ester. It was found that lactates reach afaster rate of reaction than 3-hydroxybutyrates. The value of k' for themethacrylated methyl lactate reached 0.0885 dm3/(mol·min). Opposite to this result, methacrylated ethyl 3-hydroxybutyrate's constant k' was 0.0075 dm3/(mol·min). The reaction rate study was conducted by the GC-FID method and the structures were confirmed via FT-IR, MS, 1H NMR, and 13C NMR.

Alcoholysis of waste PLA-based plastics to methyl lactate over sulfated ZrO2/SiO2 catalyst

Polylactic acid (PLA) is popularly used to replace some petroleum-based polymers due to its biodegradability. However, biodegradation of waste PLA requires specific bacteria, stringent conditions and long time. Catalytic recycling of waste PLA to valuable added products rather than composting is a sustainable green routine. In this work, catalytic alcoholysis of waste PLA to methyl lactate (MLA) was carried out over a SiO2 @UiO-66 derived solid acid (SO2–4/ZrO2/SiO2). Characterizations indicated that SO2–4/ZrO2/SiO2 processed large surface area and homogenously dispersed acid sites, and it exhibited excellent performance for the alcoholysis of waste PLA under mild conditions. At 140 oC, the yield of MLA is 92.7% within 5 h, and SO2–4/ZrO2/SiO2 could be recycled at least five times without obvious loss of activity. The specific yield of MLA over SO2–4/ZrO2/SiO2 reached 2678 mg-MLA/g-cat/h, which was higher than that of H3PW12O40, Amberlyst-45, Hβ, HZSM-5 and α-ZrP. At the same time, SO2–4/ZrO2/SiO2 was also capable of the alcoholysis of waste PLA-based products. A possible pathway of PLA alcoholysis over SO2–4/ZrO2/SiO2 catalyst was proposed.

Catalytic Performances of Sn-Beta Catalysts Prepared from Different Heteroatom-Containing Beta Zeolites for the Retro-Aldol Fragmentation of Glucose

Beta zeolites with different heteroatoms incorporated into the lattice at two loadings (Si/M = 100 or 200, where M = Al, Fe, Ga, B) were hydrothermally synthesised and used as starting materials for the preparation of Sn-Beta using Solid-State Incorporation. 119Sn CPMG MAS NMR showed that various Sn species were formed, the distribution of which depended on the identity of the initial heteroatom and the original Si/M ratio. The final Sn-Beta materials (with Si/Sn = 200) were explored as catalysts for the retro-aldol fragmentation of glucose to α-hydroxy-esters in the continuous regime. Amongst these materials, B-derived Sn-Beta was found to exhibit improved levels of selectivity and stability, particularly compared to Sn-Beta catalysts synthesised from commercially available Al-Beta materials, achieving a combined yield of methyl lactate and methyl vinyl glycolate > 80% at short times on the stream. Given that B atoms can be removed from the Beta lattice in mild conditions without the use of highly concentrated acidic media, this discovery demonstrates that B-Beta is an attractive starting material for the future post-synthetic preparation of Lewis acidic zeolites.

Accelerated synthesis of Sn-Beta with less silanols by alkaline (earth) salt for efficient transformation of glucose to methyl lactate

Sn-Beta zeolite is an excellent catalyst for the transformation of biomass derived carbohydrates. However, the long synthesis time restricted its application. Here, alkaline (earth) salt was used as promoter to accelerate the crystallization of Sn-Beta. Different alkaline (earth) salts and the amount of MgCl2 were investigated. The properties of the synthesized samples were characterized by various techniques and compared with Sn-Beta, and the catalytic performance was investigated for the conversion of glucose to methyl lactate (MLA). The results indicate that a small amount of alkaline (earth) salt, especially MgCl2, promoted dramatically the crystallization of Sn-Beta. The full crystallization time was shortened from 15 d to 5 d with the aid of MgCl2 (nMg/nSn of 1.0) for Sn-Beta with nSi/nSn of 100. Sn4+ cations were incorporated into the framework sites, while Mg2+ cations replaced the protons of silanol defects. Mg–Sn-Beta with strong Lewis acid sites and less silanols showed high activity and selectivity for glucose conversion to MLA. The yield of MLA is 20% over the fully crystallized Sn-Beta at 120 °C for 15 h and glucose concentration of 3.1 wt%, which increased significantly to 44% over the fully crystallized 1 Mg–Sn-Beta. Furthermore, Mg–Sn-Beta is stable and recyclable.

Catalytic Conversion of High Fructose Corn Syrup to Methyl Lactate with CoO@silicalite-1

Methyl lactate (MLA), a versatile biomass platform, was typically produced from the catalytic conversion of high-priced fructose. High fructose corn syrup (HFCS) is a mixture of glucose, fructose, water, etc., which is viewed as an economical substitute for fructose to produce MLA due to the much lower cost of separation and drying processes. However, the transformation of HFCS to MLA is still a challenge due to its complex components and the presence of water. In this work, the catalytic conversion of HFCS to MLA over CoO@silicalite-1 catalyst synthesized via a straightforward post citric acid treatment approach was reported. The maximum MLA yield reached 43.8% at 180 °C for 18 h after optimizing the reaction conditions and Co loading. Interestingly, adding extra 3% water could further increase the MLA yield, implying that our CoO@silicalite-1 catalyst is also capable for upgrading wet HFCS. As a result, the costly drying process of wet HFCS can be avoided. Moreover, the activity of CoO@silicalite-1 catalyst can be regenerated for at least four cycles via facile calcination in air. This study, therefore, will provide a new opportunity to not only solve the HFCS-overproduction issues but also produce value-added MLA.

Cost-effective and fast synthesis of Sn-β zeolite with less silanol defects for efficient conversion of glucose to methyl lactate

Sn-β with strong Lewis acid sites is considered as the state-of-the-art solid catalyst for converting glucose to alkyl lactate. However, the extensive use of organic template and mineralizing agent and long preparation period in the synthesis of Sn-β brought serious environmental pollution and high synthesis cost. Herein, a cost-effective and fast synthesis strategy using fewer organic template and mineralizing agent, fumed silica as Si source, Mg2+ cation as crystallization promoter and without additional solvent, is proposed to alleviate the aforementioned shortcomings. The results reveal that highly crystalline Mg-Sn-β can be synthesized in 3 days from the gel of 0.005MgO/0.005SnO2/SiO2/0.15TEAOH/0.15NH4F/3.75H2O. Besides accelerating the crystallization, it is found that Mg2+ cation facilitated Sn4+ incorporation into the framework site and lessened the silanol defects of zeolite notably. For conversion of glucose to methyl lactate (MLA), a higher yield of MLA was obtained over 1Mg-Sn-β-3d (54.4%) compared with Sn-β-H-7d (37.2%) and Sn-β-7d (41.3%).

Enhanced catalytic activity of layered double hydroxides via in-situ reconstruction for conversion of glucose/food waste to methyl lactate in biorefinery

Conversion of food waste into valuable chemicals under mild conditions has attracted increasing attention. Herein, a series of nano-sized MgAl layered double hydroxides (LDHs) were firstly developed as solid base catalyst for the methyl lactate (MLA) production directly from glucose/food waste. Glucose, which could be easily obtained from cellulose or starch-rich food waste via hydrolysis, was thus selected as the model compound. It is inspiring to find that the metal hydroxide layer in prepared LDHs was highly stable and suitable enlarged interlayer distance was reconstructed owing to in-situ intercalation of formed aromatics during the reaction, which was demonstrated by 27Al magic angle spinning nuclear magnetic resonance and time-of-flight secondary ion mass spectrometry analysis. As a result, in-situ activation of the catalysts along with gradually enhanced catalytic activity was obtained in the recycling runs and the highest MLA yield of 47.6% from glucose was achieved over LDHs (5:1) after 5 runs at 150 °C. Most importantly, the scope was further extended to other typical substrates (e.g. Chinese cabbage and rice) and the results demonstrated the effectiveness of present conversion system for real food waste.

Catalytic Conversion of Glycerol to Methyl Lactate over Au-CuO/Sn-Beta: The Roles of Sn-Beta

The production of methyl lactate as a degradable polymer monomer from biomass was an important topic for a sustainable society. In this manuscript, glycerol was oxidated to methyl lactate catalyzed by the combination of Au-CuO and Sn-Beta. The influence of Sn content, Sn source, and the preparation conditions for Sn-β was studied. The Au content in Au/CuO was also investigated by varying the Au content in Au/CuO. The catalysts were characterized by XRD, FTIR spectroscopy of pyridine adsorption, and TEM to study the role of Sn and the influence of different parameters for catalyst preparation. After the optimization of reaction parameters, the yield of methyl lactate from glycerol reached 59% at 363 K after reacting in 1.6 MPa of O2 for 6 h.

Catalytic Production of Methyl Lactate from Fructose‐Based Carbohydrates Using Yttrium Modified ZSM‐5 Zeolite

AbstractA yttrium modified ZSM‐5 zeolite (Y‐ZSM‐5) for catalytic production of methyl lactate (MLA) has been prepared through the ion exchange of commercially available H‐ZSM‐5 with yttrium chloride (YCl3) and subsequent calcination procedures. The successful preparation of Y‐ZSM‐5 was characterized by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), inductively coupled plasma atomic emission spectrometry (ICP), Fourier transform infrared spectroscopy (FT‐IR), scanning electron microscope (SEM), and nitrogen adsorption‐desorption measurement (BET method). The acid property of Y‐ZSM‐5 was investigated through NH3‐temperature programmed desorption (NH3‐TPD), and pyridine adsorption Fourier‐transform infrared spectroscopy (Py‐IR), demonstrating the introduction of Y3+ species could enhance the acid sites of zeolite. The as‐prepared Y‐ZSM‐5 is an efficient catalyst for the catalytic conversion of fructose‐based carbohydrates into methyl lactate (MLA). Under the optimum conditions, 61.3 % of MLA yield can be afforded from fructose. Furthermore, sucrose and inulin could give 39.6 % and 45.6 % of MLA yield, respectively. Meanwhile, the Y‐ZSM‐5 is structurally stable and reusable, after being recycled 5 times, the catalyst showed no appreciable loss of activity.

Hierarchical Fe–Sn/Beta catalyzes the conversion of glucose to methyl lactate

Bimetallic modified Fe–Sn/Beta was synthesized and examined as a solid acid catalyst for the transformation of glucose into methyl lactate in methanol. The catalysts were characterized by a combined characterization techniques i.e. X-ray fluorescence spectroscopy, N2 physisorption, powder X-ray diffraction, X-ray photoelectron spectroscopy, NH3 temperature-programmed desorption, and pyridine adsorption Fourier transform infrared spectroscopy. A high yield of methyl lactate of 67% was achieved upon conversion of 0.3 g glucose in 24 g methanol over 0.15 g catalyst at 220 ℃ under 2 MPa N2 for 6 h. The recyclability of the catalyst was also investigated, and the conversion of glucose remained constant; conversely, the yield of methyl lactate decreased slightly in five catalytic runs. The excellent catalytic performance of Fe–Sn/Beta was attributed to the presence of large amounts of Lewis acid sites. Besides, the rich mesoporosity in Fe–Sn/Beta improved mass transfer rates in the conversion of glucose to alkyl lactates.

Highly efficient conversion of glucose to methyl lactate over hierarchical bimetal‐doped Beta zeolite catalysts

AbstractBACKGROUNDMethyl lactate is widely applied in the chemical, food, cosmetics and pharmaceutical industries. The conversion of carbohydrates over heterogeneous catalysts to methyl lactate is a promising environmentally benign process.RESULTSHierarchical Sn‐Beta zeolite (Sn‐Beta) and corresponding bimetal‐doped Beta zeolites (M‐Sn‐Beta; M = Zn, In, La, Ga, Ni) were prepared via a novel modified hydrothermal synthesis method to convert carbohydrates into methyl lactate. The introduction of Zn into Sn‐Beta considerably improved the yield of methyl lactate from glucose, while for the catalysts containing In, La, Ga and Ni, such improvements were not observed.CONCLUSIONSA methyl lactate yield reaching up to 66.7% was obtained over Zn‐Sn‐Beta at 220 °C for 6 h. The enhanced catalytic performance was attributed to high Lewis acid density and strength, together with synergistic effects between framework Sn4+ and Zn2+ ions of Zn‐Sn‐Beta. Additionally, Zn‐Sn‐Beta demonstrated fructose and sucrose conversion into methyl lactate with yields of 68.4% and 70.0%, respectively. The Zn‐Sn‐Beta catalyst could be re‐used at least five times with only a slight loss of methyl lactate yield. © 2021 Society of Chemical Industry (SCI).

Catalytic Conversion of High Fructose Corn Syrup to Methyl Lactate with Coo@Silicalite-1

Methyl lactate (MLA), a versatile biomass platform, was typically produced from the catalytic conversion of high-priced fructose in most research studies. High fructose corn syrup (HFCS) is a mixture of glucose, fructose, and water, and an economical substitute for fructose to produce MLA due to the much lower cost of separation and drying processes. However, the transformation of HFCS to MLA is still a challenge due to its complex components and the presence of water. In this work, the catalytic conversion of HFCS to MLA over CoO@silicalite-1 catalyst synthesized via a straightforward post citric acid treatment has been reported. The maximum MLA yield reached 43.8% at 180 oC for 18 h after optimizing the reaction conditions and Co loading. Interestingly, adding extra 3% water could further increase the MLA yield, implying that our CoO@silicalite-1 catalyst is also capable for upgrading wet HFCS. As a result, the costly drying process of wet HFCS can be avoided. Moreover, the activity of CoO@silicalite-1 catalyst can be regenerated for at least four cycles via facile calcination in air. This study, therefore, will provide a new opportunity to not only solve the HFCS-overproduction issues but also produce value-added MLA.