Dehydration Of Lactic Acid Research Articles

Dual-Column Stopped-Flow GC Method for Quantification of Permanent Gases, Water, and Organic Acids from a Single Injection.

Analysis of permanent gases and organic acids is typically performed with separate methods due to challenges in achieving sufficient resolution when using GC columns that are chemically compatible with acids. We developed a method to analyze samples containing high levels of water, organic acids, oxygenates, and permanent gases (CO, CO2, and C2H4) using a single injection. Resolution is achieved using two columns: (1) an HP-FFAP column resistant to water and acids, which separates compounds based on hydrogen-bonding affinity, and (2) a GS-CarbonPLOT column capable of separating permanent gases. We employed a column isolation methodology using rotary valves to allow a heart cut of permanent gases, which coelute off the HP-FFAP column, to be trapped on the CarbonPLOT column. After separation and analysis of water, organic acids, and oxygenates via the HP-FFAP column, flow is resumed on the CarbonPLOT column, and the permanent gases are separated independently. By utilizing the unique combination of columns and the stopped-flow sequence, we achieved separation and quantification of the wide array of compounds occurring during lactic acid dehydration to acrylic acid from a single injection without the need for a sophisticated flow modulator or multiple GCs or detector arrays. This GC apparatus serves as an economical in-line analysis method for our catalytic studies and is applicable to a wide array of samples relevant to biobased fuels and chemicals.

Dehydration of lactic acid to prepare acrylic acid over Hβ zeolite modified by acid treatment and Rb ion-exchange

The catalytic dehydration of bio-derived lactic acid into acrylic acid is one of the research hotspots in the field of green chemical industry, but the selectivity of acrylic acid and the stability of catalyst still face great challenges. In this work, a modified Hβ zeolite catalyst was prepared by sequential nitric acid treatment and Rb ion-exchange for the gas phase dehydration of lactic acid to prepare acrylic acid. The nitric acid treatment increased the content of Lewis acid sites together with the decrease of the content of Bronsted acid sites, which enhanced the dehydration and hindered the decarboxylation/decarbonylation of lactic acid. Consequently, the selectivity of acrylic acid was improved. The Rb ion-exchange not only significantly decreased the density of acidic sites but also regulated the density of basic sites of the catalyst. The optimal 0.1NA-6.8Rb/Hβ catalyst treated by 0.1 mol/L of nitric acid and 6.8 wt% of Rb ion-exchange contributed to a 99.28 % conversion of lactic acid and 76.72 % yield of acrylic acid. The catalyst showed a better stability and was easy to regenerate, maintaining 87.35 % conversion of lactic acid and 62.49 % yield of acrylic acid, respectively, after two cycles of consecutive 48 h reaction.

Designing alkali-exchanged ZSM-5 catalysts for the dehydration of lactic acid to acrylic acid

This report shows that complete control of the degree of alkali exchange is possible by controlling the pH strength, and that is possible to distinguish the selectivity of the cations themselves in the lactic acid (LA) dehydration reaction by excluding undesired active sites arising from excess salts. We discovered that strong base conditions induced by alkali hydroxides (e.g., KOH) increase the degree of alkali ion exchange, and that in the absence of additional salts−such as halogen anions, oxides−the KOH-ZSM-5 catalyst exhibited high acrylic acid (AA) selectivity (∼70%) and durability (100 h). Characterization via temperature-programmed desorption (TPD) and pyridine-infrared (Py-IR) analysis revealed a full exchange of the protons bound to the Si–O–Al sites with potassium in commercial ZSM-5. In addition, structural pore expansion due to the desilication by KOH leads to significant enhancement in the selectivity for AA. The mechanistic impact of KOH treatment on lactic acid dehydration is also systematically verified by in situ IR spectroscopy.

Poly lactic acid production using the ring opening polymerization (ROP) method using Lewis acid surfactant combined iron (Fe) catalyst (Fe(DS)3)

LASC catalyst synthesis process was carried out using iron metal (Fe) and its characterization properties were tested. There are five stages carried out, namely, the manufacture of the LASC Fe(DS)3 catalyst, lactic acid dehydration, polycondensation of lactic acid into l-lactic acid oligomers (OLLA), depolymerization of oligomers into l-lactide, and the ROP process to convert l-lactide into Polymers. l-lactic acid (PLLA). The analysis used is as follows, Karl-Fisher; Spectroscopy Fourier Transform Infrared (FTIR); and Nuclear Magnetic Resonance (HNMR); Gel Permeation Chromatography (GPC); Thermogravimetry Gravity Analysis (TGA) and X-Ray Diffraction (XRD). Based on the experimental results, the catalyst Fe(DS)3 has a crystallinity value of 24% which indicates an amorphous nature and is easy to react. The value of the thermal stability of the catalyst is at 180 °C where the catalyst is able to process up to a temperature of 180 °C. Each step of the ROP is validated by FTIR analysis which shows that the components of the group are in accordance with the expected product. The comparison of the crystallinity values of PLA produced with FeCl3 and Fe(DS)3 were 37.5 and 49%, respectively. Melting temperature (Tm) values are 111 and 107 °C, respectively, Td values are 327 and 352 °C, and the resulting molecular weights are 23,720 and 20,232 g/mol. Based on the results obtained, it can be seen that the use of a LASC catalyst in the form of Fe(DS)3 is more effective than without using a LASC catalyst.

Production of acrylic acid from Bio-Derived lactic acid over a Defect-Rich molybdenum phosphosulfide catalyst

Introducing phosphorous and sulphur with molybdenum possess molybdenum phosphosulfate (MoP|S), and the material showed significant activity and stability for the vapour phase dehydration of bio-derived lactic acid to acrylic acid. Adding excessive thiourea-raptured layer spacing creates a defect-rich catalytic structure with more edges and kinks. This disordered atomic arrangement on the basal surface enhanced the dehydration performances of MoS2 catalysts. Considering the inverse trend of acetaldehyde and AA selectivity, we can assume that the decarboxylation of LA is favoured at low temperatures, whereas dehydration is favoured at high temperatures. Rate expression governed by the power law equation was found to be the best fit during the kinetic study, and the Ea of the dehydration was 11.39 KJ/mol. A conversion of 94% with a selectivity of 91% for acrylic acid at 450 °C was achieved over the defect-rich MoS2 catalyst.

Selective conversion of lactic acid to renewable acrylic acid over SDA-free Na-ZSM-5: The critical role of basic sites of sodium oxide

Dehydration of biomass-derived lactic acid (LA) is a promising, sustainable alternative to conventional acrylic acid (AA) production through the oxidation of petroleum-derived propylene. Although alkali-exchanged zeolites (e.g., K-ZSM-5) are known to be active for AA production, controlling the selectivity of competitive decarbonylation remains elusive. Herein, we report on a new, highly selective, and durable catalyst—NaxOy/Na-ZSM-5 catalyst for the high-yield production of AA (∼80%) up to 200 h. When Na-ZSM-5 was directly synthesized using Na cations as the structure-directing agent under strongly basic (NaOH) conditions, the inevitable excess sodium residue remained on the surface. Characterization performed by TPD and 23Na NMR analyses revealed the presence of sodium oxide (NaxOy) in addition to Na cations coordinated to Si–O–Al sites in the synthesized ZSM-5, providing the additional basicity and thereby leading to significant enhancement in the AA selectivity through the synergy between two active sites. The catalytic role of NaxOy in LA dehydration was systematically verified by the direct sodium impregnation experiments and in-situ IR spectroscopy.

Conceptual Process Design to Produce Bio-Acrylic Acid via Gas Phase Dehydration of Lactic Acid Produced from Carob Pod Extracts

This work discusses the conceptual process design for the integrated production of bio-based acrylic acid from carob pod aqueous extracts. CHEMCAD was used for the process simulation and cost estimation of the relevant equipment. The process was designed for a capacity of 68 kt of carob pod per year, operating 8000 h annually, and involving extraction, fermentation, catalytic dehydration, and distillation to achieve 99.98%w/w acrylic acid as the main product. The economic assessment for the base case suggests a fixed capital investment of EUR 62.7 MM with an internal rate of return of 15.8%. The results obtained show that carob pod is a promising biomass source for the production of bio-acrylic acid.

Influence of the Synthesis Protocol on the Catalytic Performance of PHI-Type Zeolites for the Dehydration of Lactic Acid

Acrylic acid is an important basic chemical and a key starting compound for a variety of consumer products. Today, acrylic acid is still produced from fossil-based propene. If acrylic acid were produced from bio-based lactic acid, this would be an important step towards sustainability. The gas-phase dehydration reaction of lactic acid to acrylic acid was performed over eight-membered ring PHI-type zeolites in the Na+ and K+-form. A few variations in the synthesis procedure of PHI-type zeolite made a big difference in the performance during the catalytic reaction due to differences in the physical and chemical properties, especially the accessibility of the pores. The catalysts were characterized with ICP-OES, XRD, CO2 physisorption, SEM and 27Al MAS NMR. The calcination resulted in a partial collapse of the PHI structure. In the case of Na,K-PHI with a low surface area, the catalysis tends to take place on the outer surface, while in the case of Na,K-PHI with a high surface area the catalysis can also take place within the pore system. This has a considerable influence on the selectivity of the catalysts.

EFFECT OF MoO3 LOADING ON PRODUCT SELECTIVITY FOR CALCIUM PYROPHOSPHATE CATALYZED VAPOR PHASE LACTIC ACID DEHYDRATION

Calcium pyrophosphate and hydroxyapatite catalysts with varying C/P ratios have been previously used by our group for vapor phase dehydration of lactic acid to acrylic acid with almost 100% conversion and up to 78% acrylic acid selectivity. The activity was highly sensitive to acidity and basicity of the catalyst. Hence the catalyst with maximum activity, calcium pyrophosphate, was modified with MoO<sub>3</sub> for modifying its acidity and to study its effect on product selectivity for lactic acid dehydration. The MoO<sub>3</sub> modified calcium pyrophosphate with 5% MoO<sub>3</sub> loading was used for vapor phase dehydration of lactic acid at 375°C using 50% lactic acid concentration with WHSV of 3 h<sup>-1</sup>. The activity was compared with nonmodified calcium pyrophosphate catalyst. Surprisingly, deoxygenation was predominant compared to dehydration. Acidity was observed to play a crucial role in product selectivity (i.e,. with less acidic support, calcium pyrophosphate with 5 wt% MoO<sub>3</sub> showed more deoxygenation activity as compared to acidic support γ-Al<sub>2</sub>O<sub>3</sub> as well as SiO<sub>2</sub> with same MoO<sub>3</sub> loading). Higher acidity led to formation of acetaldehyde as the only product. The results confirmed formation of propionic acid by deoxygenation of lactic acid using in situ generated hydrogen after decarboxylation of lactic acid to acetaldehyde.

On the catalytic vapor-phase dehydration of lactic acid to acrylic acid: a systematic review

This review gives an explicit overview of developments in the vapor-phase dehydration of lactic acid to acrylic acid with the rational design of heterogeneous catalyst systems. Constructive critiques are presented.

Effect of MoO3 loading on product selectivity for calcium pyrophosphate catalyzed vapor phase lactic acid dehydration

Effect of MoO3 loading on product selectivity for calcium pyrophosphate catalyzed vapor phase lactic acid dehydration

Lactide: Production Routes, Properties, and Applications

Lactide dimer is an important monomer produced from lactic acid dehydration, followed by the prepolymer depolymerization process, and subsequent purification. As lactic acid is a chiral molecule, lactide can exist in three isomeric forms: L-, D-, and meso-lactide. Due to its time-consuming synthesis and the need for strict temperature and pressure control, catalyst use, low selectivity, high energy cost, and racemization, the value of a high purity lactide has a high cost in the market; moreover, little is found in scientific articles about the monomer synthesis. Lactide use is mainly for the synthesis of high molar mass poly(lactic acid) (PLA), applied as bio-based material for medical applications (e.g., prostheses and membranes), drug delivery, and hydrogels, or combined with other polymers for applications in packaging. This review elucidates the configurations and conditions of syntheses mapped for lactide production, the main properties of each of the isomeric forms, its industrial production, as well as the main applications in the market.

Stable catalysis of neutral silica-supported potassium lactate for vapour-phase dehydration of lactic acid to acrylic acid - critical role of the support.

We have deeply investigated KNO3-derived silica-supported potassium lactate catalysts for the vapour-phase dehydration of lactic acid (LA) to acrylic acid (AA) by catalytic testing, IR spectroscopic monitoring, ammonia temperature-programmed desorption, isopropyl amine temperature-programmed desorption, IR spectroscopy of pyridine adsorption and thermogravimetric analysis (TGA). A combination of catalytic and acid property studies illustrates that the acidic KNO3/silica systems are not favourable for catalytic selectivity and stability for the production of AA whereas the neutral KNO3/silica systems favour catalytic selectivity and stability for the production of AA. A combination of catalytic and TGA studies indicates that the interaction between KNO3 and silica has a strong promotional effect on catalytic stability for the production of AA. A combination of IR monitoring and catalytic studies suggests that the effects of the surface acidity and the interactions between the potassium salt or base and silica on the catalytic performance are associated with the content and stability of potassium lactate as the catalytic active species. The catalyst stabilization and deactivation under LA dehydration conditions are discussed in detail. The neutral KNO3/silica systems enable the formation of potassium lactate to become dominant whereas the unsupported KNO3 and acidic KNO3/silica systems lead to the formation of poly(potassium acrylate), i.e. catalyst deactivation. This contribution includes for the first time that the dehydration of LA to AA proceeds smoothly with a neutral heterogeneous catalyst.

Lactic acid conversion into acrylic acid and other products over natural and synthetic zeolite catalysts: theoretical and experimental studies

In the present study we are interested in designing theoretical and experimental approach for the production of acrylic acid (AA) from lactic acid (LA) over various zeolite catalysts: synthetic BEA and natural clinoptilolite CLI zeolites modified with metals (Sn, Co, Cu and Fe). The catalysts were prepared using an ion exchange method. In the theoretical studies the metal M-O-M dimers were found to be stable above oxygen bound with aluminium centres of BEA and CLI zeolites. The mechanism of direct lactic acid dehydration in Sn-, Co-, Cu- and Fe-BEA zeolites was found inside the zeolites pores and in the hierarchical/surface model. Experimentally, the investigated catalysts set trends in the following by-product formation: acrylic acid, pyruvic acid (PAC), 2,3-pentanedione (2,3-PD) or acetaldehyde (AC). Based on the collected results, the following types of LA conversion reactions can be proposed: dehydration to AA, decarboxylation to acetaldehyde, hydrogenation to 2,3-pentanedione, oxidation to acetic acid, reduction to propionic acid, oxidative dehydrogenation to pyruvic acid, condensation to 1,2-propanediol.

Influence of Ionic Liquid on Transport Properties of Hybrid Membranes in the Lactic Acid Dehydration Process

Influence of Ionic Liquid on Transport Properties of Hybrid Membranes in the Lactic Acid Dehydration Process

Enhancing Pervaporation Membrane Selectivity by Incorporating Star Macromolecules Modified with Ionic Liquid for Intensification of Lactic Acid Dehydration.

Modification of polymer matrix by hybrid fillers is a promising way to produce membranes with excellent separation efficiency due to variations in membrane structure. High-performance membranes for the pervaporation dehydration were produced by modifying poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) to facilitate lactic acid purification. Ionic liquid (IL), heteroarm star macromolecules (HSM), and their combination (IL:HSM) were employed as additives to the polymer matrix. The composition and structure of hybrid membranes were characterized by X-ray diffraction and FTIR spectroscopy. Scanning electron microscopy was used to investigate the membranes surface and cross-section morphology. It was established that the inclusion of modifiers in the polymer matrix leads to the change of membrane structure. The influence of IL:HSM was also studied via sorption experiments and pervaporation of water‒lactic acid mixtures. Lactic acid is an essential compound in many industries, including food, pharmaceutical, chemical, while the recovering and purifying account for approximately 50% of its production cost. It was found that the membranes selectively remove water from the feed. Quantum mechanical calculations determine the favorable interactions between various membrane components and the liquid mixture. With IL:HSM addition, the separation factor and performance in lactic acid dehydration were improved compared with pure polymer membrane. The best performance was found for (HSM: IL)-PPO/UPM composite membrane, where the permeate flux and the separation factor of about 0.06 kg m−2 h−1 and 749, respectively, were obtained. The research results demonstrated that ionic liquids in combination with star macromolecules for membrane modification could be a promising approach for membrane design.

Nano-design of Zeolites Biomass Wastes Valorization: Dehydration of Lactic Acid into Acrylic Acid

The valorization of waste from biomass currently arouses great interest. In the present study we concentrate on the design of innovative BEA zeolite catalysts with applied metal nanoparticles - copper, vanadium and manganese for the dehydration of lactic acid to acrylic acid. Th e ab initio method based on density functional theory (DFT) was used to calculate the electron structure of the analyzed molecules. The non-local generalized gradient corrected functionals GGA-RPBE was used to in order to account for electron exchange and correlation. The cluster model was represented by a hierarchical zeolite M2Al2Si12O40H22 (M = Cu, V, Mn). Th e stabilization of the M-Ob-M dimer complex in the hierarchical structure of BEA, mechanism of adsorption of lactic acid on BEA zeolite with applied metal dimers and formation of acrylic acid on these zeolites were investigated. Th e examined metals form stable dimers interconnected by a bridge oxygen (Ob). Adsorption of lactic acid takes place in the vicinity of a dimer of M-Ob-M.The dehydration of lactic acid to acrylic acid in all cases consists in the separation of the hydroxyl group and creating a connection with a metal center of dimer and disconnection of a single hydrogen atom from the methyl group and its interaction with bridge oxygen of dimer.

Lanthanum phosphate: an efficient catalyst for acrylic acid production through lactic acid dehydration

In this work, biomass-based platform molecule lactic acid conversion to acrylic acid has been studied. A series of lanthanum phosphate (LaP) catalysts prepared by varying the lanthanum to phosphorus (La/P) mole ratio (i.e., 0.2, 0.35, 0.5, 1.0, and 2.0) and also prepared at different calcination temperatures (i.e., 400, 500, 600, and 800 °C) were investigated. The catalysts were characterized by using different techniques and tested in the dehydration of lactic acid (LA) to acrylic acid (AA) production. All the synthesized catalysts were characterized to analyze the physicochemical properties such as degree of crystallinity, total surface acidity, specific surface area, and morphology. The La/P mole ratio was found to be significant in designing the optimized catalytic system. The NH3-TPD results imply that all the catalysts exhibited varied amount of total acidity with phosphate loadings, which are mostly weak acid sites. The weak acid sites which are mainly Lewis acidity type played an important role in producing AA selectively and efficiently from the LA conversion. The most optimized reaction conditions were determined to obtain the highest LA conversion, selectivity, and AA yield. The catalyst with an La/P mole ratio of 0.35 and calcined at 500 °C exhibited the best performance with complete LA conversion, AA selectivity of ~ 74%, and a maximum yield of AA of ~ 74%. Furthermore, the LaP(0.35)[500] catalyst was successfully tested at three different time on streams and found to be stable.

Comparative study of gas-phase “dehydration” of alkyl lactates and lactic acid for acrylic acid production over hydroxyapatite catalysts

Gas-phase “dehydration” of methyl (ML) and ethyl lactates (EL) for acrylic acid (AA) production was studied and compared with the dehydration of lactic acid (LA) over serial hydroxyapatite catalysts of varying compositions (HAPm-360, molar Ca/P ratio m = 1.58–1.68, calcination temperature: 360 °C). The product distribution from both lactic esters was found very similar to that from LA; AA but not methyl (MA) or ethyl acrylate (EA) also appeared as the prevailing product (> 50 mol% by selectivity) from both ML and EL. Compared with the reaction of LA, both esters showed much lower reactivity but higher AA selectivity. Among the two esters EL was less reactive but produced a higher selectivity for AA formation. Correlating the AA selectivity or yield with the catalyst surface acid-base property uncovers that a suitable balance between the surface acidity and basicity (or acidity/basicity ratio) is the key to the lactic ester-to-AA reactions. However, the optimum surface acidity/basicity ratio for producing the highest AA selectivity from both esters was higher than that from LA. These results suggest that the lactic ester-to-AA reactions proceeded by catalytic tandem processes involving a formation of LA (or adsorbed lactate) as the key intermediate at the catalyst surface. Acid-base catalysis responsible for these observations is discussed.

Acrylic Acid Production by Gas-Phase Dehydration of Lactic Acid over K+-Exchanged ZSM-5: Reaction Variable Effects, Kinetics, and New Evidence for Cooperative Acid–Base Bifunctional Catalysis

This study investigates the effects of reaction variables (including space velocity, temperature, and partial pressures of LA and H2O) and acidic and basic additives on the gas-phase dehydration of lactic acid (LA) for acrylic acid (AA) production, using an aluminum-rich K+-exchanged ZSM-5 zeolite (molar SiO2/Al2O3 = 27, K/Al = 1.0, K/Na = 8) identified among many high-silica zeolites as the most efficient catalyst in our prior work (Yan et al. ACS Catal. 2017, 7, 538−550). Under widely varied reaction conditions (340–380 °C, feed GHSV: 9,500–38,000 h–1, 1.8–11.7 kPa LA, 52.0–73.0 kPa H2O), the catalyst offers not only high selectivity for AA (>75 mol %) but also long-term catalytic stability. Rate equations and their associated kinetic parameters for LA consumption and AA production are obtained by measuring the kinetically relevant catalytic rates under high feed space velocity (GHSV ≥ 57,000 h–1). Acidic (CO2, acetic acid, and trifluoroacetic acid) and basic (NH3) additives are added, respectively, to the reaction feed to investigate their effects on performance of the working catalyst. While addition of either CO2 or acetic acid shows no effect on the catalyst performance, the addition of either NH3 or trifluoroacetic acid causes significant decline in both the catalyst activity and selectivity for AA production, due to poisoning of the surface acidic sites by NH3 or basic sites by trifluoroacetic acid. These data well highlight the excellent catalytic performance of the investigated catalyst and offer a new piece of evidence in support of the cooperative acid–base bifunctional catalysis for the LTA reaction.