Glycerol Molar Research Articles

Electrocatalytic oxidation of glycerol performed by nickel/cobalt alloys: Adding value to a common subproduct of chemical industry

The present work shows the electrocatalytical performance of nickel/cobalt alloys towards the conversion of glycerol into higher value molecules, such as glycolic acid, oxalic acid, maleic acid, diethylene glycol and ethylene glycol, identified by chromatographic technique. To do so, the alloy was directly electrodeposited on graphite electrodes, which is a simple, readily available and cheap material, the modified electrodes were characterized by scanning electron microscopy, infrared spectroscopy and electrochemical analysis. Kinetic parameters were obtained using by both Galus methodology and rotating disc electrode (RDE), obtaining the better electrocatalytic modified electrode and the total number of electrons transferred per mol of glycerol. The modified electrode labeled as Ni0.8Co0.2(OH)2 proportion has achieved the highest glycerol conversion after 4 h of reaction, approximately 99.8%, with an energy consumption of 36.38 W/mol.

Durian peel (Durio zibethinus) utilization as an adsorbent in the purification of acidified crude glycerol

Durian (Durio zibethinus) is highly consumed seasonal fruit that generates abundant waste in the form of peel. Durian peel can serve as an effective adsorbent because it is rich in cellulose–lignin. This waste has potential applications in the chemical industry, such as using durian peel to purify crude glycerol. This research studied durian peel as an adsorbent in the form of activated carbon in the purification of acidified crude glycerol. The purification process begins with the acidification process of crude glycerol using concentrated acid with a mole ratio of phosphoric acid:glycerol (n/n) of 0.5:1, 1:1, 1.5:1, 2:1, and 2.5:1. The adsorption process by carbonization and activated of durian peel using 0.1 N KOH as adsorbent with a mass percentage ratio of adsorbent:crude glycerol (%wt) of 5 %, 10 %, 15 %, 20 %, and 25 %, and stirred using a magnetic stirrer at a speed of 250 rpm for 2 h. The adsorbent utilized has a carbon-rich content of as much as 80.6 % based on Energy Dispersive X-ray analysis. The highest glycerol purity obtained at 96.26 % is achieved at phosphoric acid:glycerol mole ratio of 1:1 and adsorbent:glycerol mass ratio of 25 %. This result also matches the analysis by gas chromatography. Thus, the others test of the purified glycerol, such as density of 1.267 g/cm3, water content of 1.6 %, ash content of 0.2 %, and matter organic non-glycerol of 1.94 %, are in accordance with the glycerol standard BS 2621:1979.

Influence of alumina fixed-bed in steam reforming of glycerol for hydrogen production

In this study, hydrogen production by steam reforming was carried out in a tubular fixed-bed reactor. The influence of some operating variables such as temperature, flow rate of the feeding glycerol solution and space velocity on hydrogen production under a non-catalyzed reaction was analyzed. The results showed that the hydrogen yield increased with temperature and decreased with the space velocity. As the feedstock flow rate increased, the hydrogen yield decreased rapidly. Compared with a reference experiment without fixed-bed, the use of non-porous alumina fixed-bed showed better results. Under the best reaction conditions (900 °C and a feedstock flow rate of 0.85 g/min), 17 L/h of syngas were obtained, with a purity of about 55% of hydrogen and a production of 2.7 moles of hydrogen by mol of glycerol.

Local solvation structures govern the mixing thermodynamics of glycerol-water solutions.

Glycerol is a major cryoprotective agent and is widely used to promote protein stabilization. By a combined experimental and theoretical study, we show that global thermodynamic mixing properties of glycerol and water are dictated by local solvation motifs. We identify three hydration water populations, i.e., bulk water, bound water (water hydrogen bonded to the hydrophilic groups of glycerol) and cavity wrap water (water hydrating the hydrophobic moieties). Here, we show that for glycerol experimental observables in the THz regime allow quantification of the abundance of bound water and its partial contribution to the mixing thermodynamics. Specifically, we uncover a 1 : 1 connection between the population of bound waters and the mixing enthalpy, which is further corroborated by the simulation results. Therefore, the changes in global thermodynamic quantity - mixing enthalpy - are rationalized at the molecular level in terms of changes in the local hydrophilic hydration population as a function of glycerol mole fraction in the full miscibility range. This offers opportunities to rationally design polyol water, as well as other aqueous mixtures to optimize technological applications by tuning mixing enthalpy and entropy based on spectroscopic screening.

Enabling anaerobic growth of Escherichia coli on glycerol in defined minimal medium using acetate as redox sink

Glycerol has become an attractive substrate for bio-based production processes. However, Escherichia coli, an established production organism in the biotech industry, is not able to grow on glycerol under strictly anaerobic conditions in defined minimal medium due to redox imbalance. Despite extensive research efforts aiming to overcome these limitations, anaerobic growth of wild-type E. coli on glycerol always required either the addition of electron acceptors for anaerobic respiration (e.g. fumarate) or the supplementation with complex and relatively expensive additives (tryptone or yeast extract). In the present work, driven by model-based calculations, we propose and validate a novel and simple strategy to enable fermentative growth of E. coli on glycerol in defined minimal medium. We show that redox balance could be achieved by uptake of small amounts of acetate with subsequent reduction to ethanol via acetyl-CoA. Using a directed laboratory evolution approach, we were able to confirm this hypothesis and to generate an E. coli strain that shows, under anaerobic conditions with glycerol as the main substrate and acetate as co-substrate, robust growth (μ = 0.06 h−1), a high specific glycerol uptake rate (10.2 mmol/gDW/h) and an ethanol yield close to the theoretical maximum (0.92 mol per mol glycerol). Using further stoichiometric calculations, we also clarify why complex additives such as tryptone used in previous studies enable E. coli to achieve redox balance. Our results provide new biological insights regarding the fermentative metabolism of E. coli and offer new perspectives for sustainable production processes based on glycerol.

A kinetic study of the ultrasonically assisted ethyl esterification of fatty acids using an immobilized lipase catalyst and deep eutectic solvent

AbstractIn this study, the esterification reaction kinetics of biodiesel (fatty acid ethyl ester) prepared from waste oil (cooking oil waste and oleic acid mixture) and ethanol at three different temperatures (313.15, 323.15, and 333.15 K) by lipase (Novozym®435) catalyzed. It was investigated under three different reaction systems of ultrasonic (without DES), deep eutectic solvent (DES, choline chloride: glycerol mole ratio = 1:2, without ultrasonic), and ultrasonic‐assisted DES. The results showed that the combination of the ultrasonic and DES had a synergistic effect on the enzymatic reaction. The activation energy of the reaction was the smallest (24.82 kJ/mol) compared to the other two processes (ultrasonic: 34.38 kJ/mol and DES: 29.43 kJ/mol), and the reaction was easier to proceed. Subsequently, the reusability of lipase and the composition of the product were studied. The results showed that the conversion rate of fatty acid ethyl ester decreased from the initial 93.33% to 80.31% when the experiment was repeated five times in the ultrasonic‐assisted DES system. The ethyl ester composition of the product was mainly concentrated between C14 and C24, and the proportion of ethyl oleate was the most abundant.

Acetalization of Glycerol with Citral over Heteropolyacids Immobilized on KIT-6

Glycerol acetalization with citral was studied using a heteropolyacid (tungstophosphoric acid) supported on KIT-6, as a catalyst, at 100 °C. Different catalysts were synthesized. Catalysts were characterized by scanning electron microscopy (SEM), inductively coupled plasma (ICP), X-ray diffraction (XRD), attenuated total refletion-Fourier transform infrared spectroscopy (ATR-FTIR), and potentiometric titrations. At a fixed time, the glycerol conversion increased with the H3PW12O40 (PW) on KIT-6. PW4-KIT-6 material had a higher conversion than other catalysts. The optimization of glycerol’s acetalization with citral was studied under the PW4-KIT-6 catalyst. After 5 h, it was found that, at T = 100 °C, with m = 0.3 g of solid, molar glycerol:citral = 1:2.25, the conversion of glycerol was 89%. Moreover, the PW4-KTI-6 catalyst showed good catalytic stability.

Catalytic performance of cerium-modified ZSM-5 zeolite as a catalyst for the esterification of glycerol with acetic acid

Abstract Esterification of glycerol with acetic acid was carried out over cerium-modified ZSM-5 zeolites to synthesize monoacetin (MA) and diacetin (DA). The modified zeolite catalyst was characterized. The effect of reaction process parameters such as acetic acid to glycerol mole ratio (1–11), reaction temperature (30–120 °C), and catalyst weight (2–8 wt %) on the selectivity of the product was investigated. At 120 °C reaction temperature, 8 wt % catalyst, and 9:1 acetic acid to glycerol mole ratio, about 98.32% conversion of glycerol were obtained. This reaction follows pseudo-first-order reaction kinetics and the activation energy was found to be 63.72 kJ mol−1.

Efficacy of Passion Fruit Cryopreservation Using Cryopotectant Agents

ABSTRACT This study aimed to evaluate the effects of cryoprotectant agents on Passiflora eichleriana, Passiflora crystallina and Passiflora nitida seeds undergoing cryopreservation. The experiment was conducted with non-cryoprotected or non-cryopreserved seeds (control), cryopreserved seeds without cryoprotectant and cryopreserved seeds treated with the following cryoprotectants: 1.73, 2.28, 2.60 or 2.71 mol glycerol; 0.37, 0.46, 0.54 or 0.61 mol sucrose; or 0.37, 0.72, 1.04 or 1.35 mol dimethylsulfoxide (DMSO). After treatment, the seeds were cryopreserved in liquid nitrogen (LN2) for 7 days and then defrosted in 37°C water for 5 min. The seeds were submitted to germination and vigor tests consisting of four replicates of 50 seeds. Percentage of germination (PE) and germination velocity index, percentage of emergence velocity index, shoot and root length, and shoot and root dry mass were evaluated. After cryopreservation, all of germination and vigor values were higher without the use of cryoprotectants. The cryoprotectant glycerol had a deleterious effect on seed viability and vigor for all Passiflora species. Glycerol inhibit seedling emergence and concentrations higher than 2.60 mol seed germination on P. cristalina. Higher concentrations of DMSO decrease seed viability and vigor in P. crystalina and P. nitida.

Promotion of compound K production in Saccharomyces cerevisiae by glycerol

BackgroundGinsenoside compound K (CK), one of the primary active metabolites of protopanaxadiol-type ginsenosides, is produced by the intestinal flora that degrade ginseng saponins and exhibits diverse biological properties such as anticancer, anti-inflammatory, and anti-allergic properties. However, it is less abundant in plants. Therefore, enabling its commercialization by construction of a Saccharomyces cerevisiae cell factory is of considerable significance.ResultsWe induced overexpression of PGM2, UGP1, and UGT1 genes in WLT-MVA5, and obtained a strain that produces ginsenoside CK. The production of CK at 96 h was 263.94 ± 2.36 mg/L, and the conversion rate from protopanaxadiol (PPD) to ginsenoside CK was 64.23 ± 0.41%. Additionally, it was observed that the addition of glycerol was beneficial to the synthesis of CK. When 20% glucose (C mol) in the YPD medium was replaced by the same C mol glycerol, CK production increased to 384.52 ± 15.23 mg/L, which was 45.68% higher than that in YPD medium, and the PPD conversion rate increased to 77.37 ± 3.37% as well. As we previously observed that ethanol is beneficial to the production of PPD, ethanol and glycerol were fed simultaneously in the 5-L bioreactor fed fermentation, and the CK levels reached 1.70 ± 0.16 g/L.ConclusionsIn this study, we constructed an S. cerevisiae cell factory that efficiently produced ginsenoside CK. Glycerol effectively increased the glycosylation efficiency of PPD to ginsenoside CK, guiding higher carbon flow to the synthesis of ginsenosides and effectively improving CK production. CK production attained in a 5-L bioreactor was 1.7 g/L after simultaneous feeding of glycerol and ethanol.

Quartz halogen‐ultrasonication integrated rotating reactor for efficient photocatalytic‐thermocatalytic synthesis of glyceryl monocaprin: Kinetics of heterogeneous esterification

AbstractA pioneering intensification protocol for glyceryl monocaprin (GMC) synthesis deploying coactive electromagnetic energies,viz. quartz halogen radiation (QHR) and ultrasonication (US) is explored. Concurrently, Amberlyst 15 (A15) and nano‐TiO2 P25 (NT‐P25) were applied to achieve capric acid (CA) conversion of 97% ± 0.5%, employing the integrated QHR‐US energized rotating reactor (QHRUERR), which was 7.5% ± 0.5% higher than QH energized rotating reactor (QHERR) and 20% ± 1% greater compared to an ultrasonically energized rotating reactor (USERR). Optimal factors, viz., 0.35:1 CA:glycerol mole ratio, 343K temperature, 0.67:1 A15:P25(wt./wt.) dose, resulted maximum GMC selectivity (95% ± 0.3%). Langmuir–Hinshelwood model (R2 = .99) could best represent the esterification kinetics in QHRUERR under optimal condition. Significantly, reaction activation energy was found minimum in QHRUERR (9.63 kJ/mol) compared with a rotating reactor equipped either with QHR (27.5 kJ/mol) or the US (32.74 kJ/mol), thus implying promising synergy and energy efficiency of QHRUERR. Ultraviolet‐visible diffuse reflectance spectra and photoluminescence analyses exhibited the photoactivity of ATO (A15 : NT‐P25=0.67: 1 w/w) catalyst possessing lower band gap energy (2.98 eV). The optimal product GMC demonstrated appreciable food preservative attributes toward Aspergillus Niger food pathogen. An energy‐efficient and sustainable reactor could, thus, be explored in this study for proficient green synthesis of valuable food preservatives.

Metabolic engineering of Pseudomonas denitrificans for the 1,3-propanediol production from glycerol

Bio-production of 1,3-propanediol (1,3-PDO) from glycerol was studied using Pseudomonas denitrificans as host, which aerobically synthesizes coenzyme B12, an essential cofactor of glycerol dehydratase (GDHt). P. denitrificans was transformed with the 1,3-PDO synthesis pathway composed of GDHt and 1,3-PDO oxidoreductase (PDOR), and its putative 3-hydroxypropionaldehyde (3-HPA) dehydrogenase(s), leading to the production of 3-hydroxypropioninc acid form the intermediary 3-HPA, was identified and deleted. In addition, to improve the availability of NADH for PDOR, oxidation of NADH in the electron transport chain was disturbed by deletion of the nuo operon and/or ndh gene. Finally, acetate formation pathway was eliminated. One resulting strain could produce 68.95 mM 1,3-PDO with the yield of 0.92 mol 1,3-PDO/mol glycerol on flask scale and 440 mM with the yield of 0.89 mol 1,3-PDO/mol glycerol in a fed-batch bioreactor experiment. This study demonstrates that P. denitrificans is a promising recombinant host for the production of 1,3-PDO from glycerol.

Enzymatic Production of Diacylglycerols from High‐Acid Soybean Oil

AbstractIn this study, high‐acid soybean oil, with acid values (Av) ranging from 10 to 50, was enzymatically deacidified for diacylglycerol (DAG) production. The effects of glycerol amounts were studied intensively. The glycerol amount could be calculated theoretically based on the Av of the raw oil (1 mol glycerol with 2 mol oleic acid to form 1 mol DAG, and 1 mol glycerol with 2 mol soybean oil to form 3 mol DAG). A total of 60–62% of DAG could be obtained and the free fatty acid (FFA) content was reduced to 0.36–0.66%. Increased glycerol did not lead to DAG content improvement. However, the glycerol amount based on just the deacidification theoretical calculation (1 mol glycerol with 2 mol oleic acid to form 1 mol DAG) was not feasible to reduce the FFA content. Moreover, Novozym 435 was rather stable in the present reaction procedure, no loss of activity was observed after 10 consecutive uses.

From single to multiresponse modelling of food digestion kinetics: The case of lipid digestion

This work presents that lipid digestion kinetics of oil-in-water emulsions can be described by a mechanism-based multiresponse model. The modelling approach proposed takes into account multiple interlinked responses of in vitro lipolysis. Different reaction schemes are proposed and iteratively adapted for one dataset. Based on model discrimination, the model that best described the experimental data was selected. This selected multiresponse model assumes that 1 mol triacylglycerol hydrolyzes to release either 1 mol of monoacylglycerol and 2 mol of free fatty acids or either 3 mol of free fatty acids and 1 mol glycerol. Convergence was evaluated, as well as goodness of fit and accuracy of the parameter estimates (R2adj>0.986). The validity of this mechanistic model was checked using 28 independent datasets and clearly surpasses the outcome of single response modelling. This is the first proof of concept of the potential of multiresponse modelling in the context of food digestion.

Strain screening and optimization of biohydrogen production by Enterobacter aerogenes EB-06 from glycerol fermentation

Biohydrogen technology has drawn much attention due to its many advantages. However, it is still necessary to screen much more strains with stronger hydrogen-producing capacity for future commercialization processes. In this paper, a biohydrogen-producing strain Enterobacter aerogenes EB-06 was isolated, identified, and named. It could convert glycerol to biohydrogen by microorganism fermentation. The effects of oxygen content, initial pH, initial glycerol concentration, and initial nitrogen source content on biohydrogen production process were investigated. The results have shown that biohydrogen generation was more favorable under anaerobic conditions. The optimum specific biohydrogen production rate (QH2) was obtained as 41.47 mmol H2/g DCW h at 40 g/L initial glycerol concentration. The optimum volume H2 yield (CH2) was 83.76 mmol H2/L at initial pH 7.0. It was found that nitrogen source content (0–4 g/L) could promote biohydrogen production and cell growth. The biohydrogen production of Enterobacter aerogenes EB-06 from glycerol was optimized by the orthogonal experimental design. The optimal yield coefficient of biohydrogen from glycerol fermentation (YH2/glycerol) of EB-06 was obtained as 1.07 mmol H2/ mol glycerol at 10 g/L initial glycerol concentration, initial pH 5.0, and initial C/N ratio 5/3.

Nickel-based catalysts for hydrogen production by steam reforming of glycerol

As the renewable energy technologies are making progress every day, hydrogen energy technologies are taking huge part of this development. Nowadays, there are several industries using hydrogen. Also, the increase at biodiesel production amounts has increased the glycerol production as by-product. One of the main objectives of this study is to compare the effects Al2O3-, SiO2- and CeO2-supported nickel catalysts at steam reforming of glycerol in order to produce hydrogen. All catalysts were prepared by incipient to wetness method. The obtained steam reforming results showed that nickel catalysts supported on ceria showed the highest activity. Also the effect of nickel amount on CeO2 support material has been studied. The highest hydrogen amounts were obtained with 15 wt% nickel loading. Also the increase at water/glycerol ratio increased the hydrogen production amount. The highest hydrogen yield was obtained as 4.82 mol per glycerol mole, whereas the theoretical hydrogen yield is 7 mol, by using 15 wt% Ni/CeO2 catalyst, water/glycerol ratio of 15 and at 650 °C reaction temperature.

Modeling of Thermochemical Conversion of Glycerol: Pyrolysis and H2O and CO2 Gasification

Glycerol is the byproduct of biodiesel production. Biodiesel has been considered a strong alternative candidate to petro diesel. Stoichiometrically, one mole of glycerol is generated during the conversion of one mole of triglyceride feedstock or per three produced moles of biodiesel. This an equivalent to 10–15% byproduct volume/mass. The biodiesel production has observed a huge jump in production, being preserved as a renewable, sustainable and near CO2 neutral source. This is driven by advances in technology of 1st generation biomass lipid harvesting and advancement of 3rd generation breeding and maximizing algae lipids and their extraction. Therefore, a sound solution for velarizing the glycerol byproduct is becoming a necessity before it is viewed as waste burden. Currently, the glycerol market is saturated and substantial production can lead to an economic imbalance. Therefore, satisfying the energy needs following thermochemical conversion of glycerol into clean syngas fuel is a more favorable and dual solution to the problem, i.e. reducing process waste and generating clean fuel. In this work, the process metrics in using Glycerol as feedstock for the production of syngas fuel is evaluated under pyrolysis then gasification under steam (H2O(g)) and CO2 moderators. Process metrics are assessed using the syngas mole fractions and their normalized value termed as the cold gasification efficiency. The analysis followed equilibrium modeling based on Gibbs Energy Minimization and under sweeping reaction temperatures. The model is validated against experimental literature. Result of glycerol pyrolysis achieved a maximum of 83% at 0.43 CO and 0.57 H2 mole fraction. Glycerol gasification under steam moderator resulted in a slightly higher efficiency of 84% and 0.20 CO and 0.55 H2 mole fractions, while under CO2 moderator resulted in a lower efficiency of 80% and 0.40 CO and 0.30 H2 mole fractions. This emphasizes the technical feasibility of thermochemical conversion of glycerol into clean syngas and closes the loop of biodiesel production towards zero byproduct process.

Analysis of the Continuous Bioconversion of Glycerol by Promotion of Highly Glycerol-Resistant Glycerol-Degrading Bacteria

We identified component microorganisms in a fed-batch operation by modulating the mixed flora via addition of glucose to achieve continuous bioconversion of hardly degradable glycerol. To study the microbial community structure of the flora accumulated by the addition of glucose, 16S ribosomal RNA (rRNA) gene was sequenced using PCR with denaturing gradient gel electrophoresis (DGGE). Burkholderia vietnamiensis, Burkholderia phenoliruptrix, Staphylococcus aureus, Bacillus licheniformis, and Clostridium pasteurianum were identified as component strains. Using the colony containing C. pasteurianum, the hydrogen yield was 0.34 mol/(mol glycerol). C. pasteurianum, B. licheniformis, B. vietnamiensis, and B. phenoliruptrix utilized both glycerol and glucose as substrates and could tolerate high glycerol loads. In early fermentation, predominance of the hydrogen-producing C. pasteurianum resulted in the conversion of glycerol into hydrogen and 1,3-propanediol. In contrast, in late fermentation, the auxiliary degradation of B. licheniformis and the two Burkholderia strains enabled continuous conversion of the glycerol to valuable compounds. Glucose addition results in a stable flora by optimizing the ratio of highly glycerol-resistant glycerol-degrading bacteria, thereby establishing an anaerobic digestion process that allows continuous conversion of high loads of glycerol.

Binary Diffusion Coefficients of Glycerol–Water Mixtures for Temperatures from 323 to 448 K by Dynamic Light Scattering

The binary diffusion coefficients of mixtures consisting of glycerol and water with glycerol mole fractions of 0.299, 0.500, and 0.699 were investigated by dynamic light scattering (DLS) in macroscopic thermodynamic equilibrium over the temperature range 323–448 K. Furthermore, a beam displacement method implemented in the same experimental setup was used to determine the refractive indices of the mixtures required for the evaluation of the DLS measurements. The reported results represent the first temperature-dependent data set for the binary diffusion coefficient of glycerol–water mixtures, where increasing diffusion coefficients were found for increasing temperature and decreasing glycerol concentration. The latter finding is consistent with literature data that are restricted to specific temperatures. The present results are in good agreement with the absolute values and concentration-dependent trends of the binary diffusion coefficients for glycerol–water mixtures available in the literature.

Ruthenium doped nickel-alumina-ceria catalyst in glycerol steam reforming

Crude glycerol excess as a by-product of biodiesel industry has given rise to the need to valorize glycerol, e.g. its conversion to hydrogen by steam reforming. While many studies have been made towards catalyst development and their performance, catalyst selectivity and stability continue to be issues of further investigation. In this work, ruthenium doped nickel-alumina-ceria catalyst has been studied. The catalyst was prepared by wet impregnation method. Characterization was done with BET surface area, SEM, temperature programmed reduction, temperature programmed oxidation and pulse hydrogen chemisorption techniques. Performance test experiments were carried out in a packed bed reactor with aqueous glycerol feed, in water to glycerol mole ratio 12:1, at temperatures 550°C to 800°C, weight hourly space velocity of 10h−1 and atmospheric pressure. It was found that 10Ni-1Ru/Al2O3/5CeO2 catalyst showed superior catalytic performance and stability, compared to 10Ni/Al2O3 and 10Ni/Al2O3/5CeO2. Hydrogen selectivity of 88.6% was obtained versus a thermodynamic value of 95.9% at 650°C. The catalyst was also stable for 24h on stream. From the kinetic study, overall activation energy was found to be 70.82kJ/mol and order of reaction with respect to glycerol and steam were 0.31 and 0.52 respectively.