Use of renewables for the production of chemicals: Glycerol oxidation over carbon supported gold catalysts

As a renewable feedstock and due to its high functionality glycerol is an attractive reactant for the production of a large number of valuable compounds. We report on an environmentally friendly alternative to produce chemicals from the glycerol oxidation, which are currently produced either by stoichiometric oxidation processes or by enzymatic routes. We investigate the heterogeneously catalyzed liquid-phase oxidation of glycerol with carbon supported gold catalysts. The prepared nanosized gold catalysts are highly active, so that the reaction could be performed under atmospheric pressure. The influence of the preparation method of the catalysts has been investigated. Moreover, the support effect on the catalytic process has been studied and discussed in terms of pore structure of the investigated carbon materials. The promotor effect of platinum on Au/C catalysts was examined and it could be shown that the presence of Pt increases not only the catalyst activity but also the selectivity. By promoting the gold catalysts with platinum the selectivity to dihydroxyacetone could be increased from 26% (Au/C) to 36% (Au–Pt/C).     

Oxidation by UV and Ozone of Organic Contaminants Dissolved in Deionized and Raw Mains Water

Organic contaminants dissolved in deionized pretreated and raw mains water were reacted with ultraviolet light and ozone. Ozone first was used for partial oxidation followed by ozone combined with ultraviolet radiation to produce total oxidation. The reduction of TOC level and direct oxidation of halogenated compounds were measured throughout the treatment process. The rate of TOC reduction was compared for ozone injected upstream and inside the reactor.     

Amperometric biosensor for formic acid in air

The possibility of developing a simple, inexpensive and specific personal passive “real-time” air sampler incorporating a biosensor for formic acid was investigated. The sensor is based on the enzymatic reaction between formic acid and formate dehydrogenase (FDH) with nicotinamide adenine dinucleotide (NAD⁺) as a co-factor and Meldola's blue as mediator. An effective way to immobilise the enzyme, co-factor and Meldola's blue on screen-printed, disposable, electrodes was found to be in a mixture of glycerol and phosphate buffer covered with a gas-permeable membrane. Steady-state current was reached after 4–15 min and the limit of detection was calculated to be below 1 mg/m³. However, the response decreased by 50% after storage at −15°C for 1 day.     

Sweet and sour potential of yeast from the Yarrowia clade

The food industry is witnessing a growing demand for food additives. Microbial fermentation is an attractive way to produce them using microorganisms, including the yeast Yarrowia lipolytica. Twelve species of the Yarrowia clade were screened for erythritol, mannitol and citric acid production from pure glycerol, glucose or fructose in four different media. During shake-flask cultures, only Y. lipolytica was able to secrete citric acid. Glycerol was found to be the best substrate for erythritol and mannitol biosynthesis by all the species. The six best candidate species for sweetener biosynthesis were cultivated in bioreactors. Up to 69.8 g dm⁻³ of total polyols with a yield of 0.59 g g⁻¹ was obtained for Candida oslonensis, the best sweetener producer. It secreted 44.6 g dm⁻³ of erythritol (Q_Ery = 1.16 g dm⁻³ h⁻¹ and Y_Ery/S = 0.4 g g⁻¹) and 34 g dm⁻³ of mannitol (0.29 g g⁻¹). Additionally, Candida hollandica and Yarrowia divulgata represent promising species for which media composition and culture parameters still have to be optimized.     

A comparative study on the performance of M (Rh,Ru, Ni)-promoted metallurgical waste driven catalysts for H2 production by glycerol steam reforming

A comprehensive study was conducted on the performance of M-promoted (M = 1%Ru, 1%Rh, 5%Ni) upgraded slag oxide metallurgical waste catalysts (M-UGSO) for hydrogen production by glycerol steam reforming (GSR). The results confirmed that the tendency of the incorporated metal to interact with Mg/Fe containing species within UGSO plays a key role in the surface availability of the corresponding metal, structural changes after reduction, and catalyst stability. Aside its best stability, 5% Ni-UGSO showed a performance (glycerol conversion to gaseous products of 100% and H₂ yield of 74%) comparable with 1% Rh-UGSO (100% and 78%, respectively) or even surpassing that of 1% Ru-UGSO (94% and 71%, respectively), as noble metal-based catalysts. Synergistic cooperation was achieved by incorporated metals (M) and Fe/Mg containing species within UGSO, resulting in enhanced glycerol and water activation. The weakest results of Ru-UGSO could be justified by lack of propensity for MgO–RuO₂ interaction on UGSO surface.     

Glycerol and Acetate Additions to Maximize Lipid Content in High-Density Cultures of Phagotrophic Alga Ochromonas danica

Waste organics conversion to algal lipid is environmentally friendly and it promotes sustainability. Achieving high-lipid content in cells is crucial to the economic feasibility of algal lipid production and collection. Here, a phagotrophic microalga Ochromonas danica was grown on waste ketchup and then stimulated to accumulate high-lipid content using glycerol and acetate. Individually, glycerol and acetate could increase lipid synthesis. Sequential glycerol-then-acetate addition was more effective; for an O. danica culture with 0.25 g L⁻¹ cells, the intracellular lipid content was increased to 70–80% (w/w) in 6–12 hours. However, acetate added at >1 g L⁻¹ damaged cells. For high-density (25 g L⁻¹) fermentations, glycerol and acetate addition strategies were evaluated to overcome this inhibition. Results indicated that glycerol could be added in batches or continuously as long as the amount was sufficient to satisfy the glycerol consumption rate of 6 mg (g cells-hour)⁻¹ while acetic acid needed to be added continuously, optimal at a rate of 0.27–0.30 g hour⁻¹ or 12–14 mg (g cells-hour)⁻¹. Intracellular lipid content could reach 70–80% after 2-day supplementation of glycerol and acetic acid. The methods of glycerol/acetate additions developed here enhance algal lipid production and enable effective conversion of organic wastes to algal lipids as sustainable bioproducts.     

A novel route to synthesis of glycerol dimethyl ether from epichlorohydrin with high selectivity

The effective utilization of glycerol, a by-product in the production of biodiesel, into useful chemicals is desirable from the viewpoint of green chemistry. With this in mind, a novel and highly selective route to synthesizing glycerol dimethyl ether (2,3-dimethoxy-1-propanol), a potential fuel additive, from glycerol was proposed. This route uses both glycerol and methanol as starting materials, takes epichlorohydrin as an intermediate product, and utilizes HCl as a recycling agent. Hereinto, the key step of this route is the reaction between epichlorohydrin and methanol to produce 2,3-dimethoxy-1-propanol which is identified by GC–MS, ESI-MS, IR and NMR. The thermodynamics of this reaction was analyzed and the result showed that the thermodynamics of a reaction was favorable and a high product yield was expected. The effect of various parameters such as kind of acid catalyst, molar ratio of epichlorohydrin to methanol, reaction temperature and reaction time was studied. Among various acid catalysts investigated, the acidic ionic liquid [HSO₃-b-N(CH₃)₃]HSO₄ exhibited the highest activity and selectivity: conversion of epichlorohydrin of 100% and selectivity of 2,3-dimethoxy-1-propanol of 99% at 393 K, 10 h, an initial pressure of 0.1 MPa and a molar ratio of catalyst:ECH:CH₃OH of 0.01:1:5. After the reaction, [HSO₃-b-N(CH₃)₃]HSO₄ was separated by vacuum distillation and then reused for the next cycle directly. The results showed that the product selectivity remained at about 94% but the conversion of epichlorohydrin dropped to 75% after being used five times. Subsequently, a reaction mechanism for the synthesis of 2,3-dimethoxy-1-propanol from epichlorohydrin and methanol was proposed.     

High selectivity of erythritol production from glycerol by Yarrowia lipolytica

The effect of different vitamins and nitrogen sources on the yield, productivity and selectivity of erythritol production from glycerol in batch and fed-batch cultures by Yarrowia lipolytica Wratislavia K1 strain was examined in the study.Thiamine was a vitamin necessary for efficient erythritol production and the yeast extract (YE) turned out to be its best source. The YE was additionally a very good source of nitrogen in this process. Erythritol production may be efficient in the media containing only yeast extract and crude glycerol. The application of a high substrate concentration (325 kg m⁻³) in the fed-batch system with pulsed addition of glycerol resulted in erythritol production of 201.2 kg m⁻³ after 168 h of cultivation. The mass fraction of by-products, such as other polyols and organic acids, did not exceed 10%. The study showed that by-products formation could be significantly reduced by the addition of a nitrogen source after glycerol depletion from the media. Wratislavia K1 strain does not utilize erythritol in the presence of other carbon sources and this feature was used in order to increase product selectivity up to 99.7% and protein content in yeast biomass up to 28.7%. The factors determining the use of biomass as animal feed, i.e. protein concentration and presence of metal ions, were discussed as well.     

Structural Analysis of Partial and Total Esters of Glycerol Undecenoate and Diglycerol Undecenoate

The direct esterification reaction between glycerol and undecylenic acid or between diglycerol and undecylenic acid generates all the possible types of glycerol or diglycerol esters. Purification by silica gel chromatography resulted in the isolation of each of these types of ester in a pure form. The molecular structures of the compounds isolated were characterized and identified by mass spectrometry, ¹H NMR, ¹³C NMR and DEPT‐135. We then studied the composition of esters of undecylenic acid formed with glycerol or diglycerol as a function of their reaction conditions, which constitute a highly complex system. We purified undecylenic acid esters from each polyol family to allow the structural identification of each ester of glycerol and each ester of diglycerol with undecylenic acid. We found that the polarity of these non‐ionic amphiphilic esters directly affected their affinity for organic and inorganic solvents and that these esters behaved very differently from anionic amphiphilic molecules, such as undecylenic acid.