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Gold nanoparticles on different oxidic supports (TiO2, Al2O3 and ZnO) have been studied for the oxidation of glycerol in methanol, using molecular oxygen as the oxidizing agent in a batch set-up. The main oxidation products are methyl glycerate and dimethyl mesoxalate in over 95% selectivity at high glycerol conversion, indicating that C–C bond scission occurs at a significantly lower extent compared to glycerol oxidations in water. The product selectivity is a function of the support. Highest selectivity (82% at 72% conversion) to methyl glycerate is observed in the case of Au/TiO2 as the catalyst. The use of a base is not essential for the glycerol oxidation reaction to occur, although for TiO2 and Al2O3 higher initial activities are found in the presence of sodium methoxide. Au/ZnO gives comparable activity and selectivity both in the presence and absence of a base. Oxidation experiments with reaction intermediates indicate that oxidation of methyl glycerate to higher oxygenates does not occur to a significant extent in methanol. An alternative pathway for the formation of dimethyl mesoxalate involving dihydroxyacetone is proposed. [ABSTRACT FROM AUTHOR]

The acetalization of acetone with glycerol to yield 2,2-dimethyl-1,3-dioxolane-4-methanol (solketal) was successfully catalyzed by mesoporous substituted silicates including the novel Hf-TUD-1 material. This reaction offers an attractive path for the conversion of glycerol, which is the main side-product in the synthesis of biodiesel, to a valuable compound with potential for industrial applications. The most promising among the heterogeneous catalysts employed in this work, Zr- and Hf-TUD-1 and Sn-MCM-41, display mainly Lewis acid properties as demonstrated by characterization with FT-IR analysis of pyridine adsorption, and achieve superior results compared to a reference solid acid catalyst such as Ultrastable zeolite Y. Especially the newly synthesized Hf-TUD-1, showing the highest conversion and turnover among the screened materials, is a promising catalyst for the acetalization of acetone with glycerol in a sustainable process. The excellent performance of these mesoporous catalysts is ascribed to their combination of acidity, wide pores, large specific surface area and relatively hydrophobic surface. [ABSTRACT FROM AUTHOR]

The effective conversion of carbon dioxide (CO2) and glycerol is an interesting topic in green chemistry. In this work, we studied the simultaneous transformation of CO2 and glycerol to value-added products using propylene oxide (PO) as coupling agent catalyzed by alkali metal halides. The effects of reaction temperature, CO2 pressure, reaction time, amount of catalyst, and PO to glycerol molar ratio on the reaction were investigated. It was discovered that the coupled catalytic reaction could produce glycerol carbonate (GC), propylene glycol (PG) and propylene carbonate (PC) very effectively using KI, an abundant and cheap salt, as the catalyst. The main reasons are that glycerol and PG are not only the reactant and product, respectively, but also act as the effective co-catalysts to promote the key step of the coupled reaction, and the reaction is thermodynamically favorable. This effective and atom economic route to convert glycerol and CO2 simultaneously has great potential application. [ABSTRACT FROM AUTHOR]

We describe herein the use of glycerol as the solvent in the copper-catalyzed cross-coupling reaction of diaryl diselenides with arylboronic acids using CuI and DMSO as additive. This cross-coupling reaction was performed with diaryl diselenides and arylboronic acids bearing electron-withdrawing and electron-donating groups, affording the corresponding diaryl selenides in good to excellent yields. The glycerol–CuI mixture can be directly reused for further cross-coupling reactions. [ABSTRACT FROM AUTHOR]

The selective telomerisation of 2,3-dimethylbuta-1,3-diene with several different mono- and polyalcohols proceeds in the presence of a heterogeneous palladium catalyst. By applying a green solvent (CO2), the selectivity of the reaction as well as the conversion of diene is easily moderated, imitating the results of reactions with organic solvents. In addition, the pressure tuning allows the driving of the reaction towards a highly selective synthesis of monotelomers, which could be valuable future intermediates in the production of surfactants or defoaming agents. Additionally, it was highlighted for the first time that the catalytic addition of glycerol and other polyalcohols to 2,3-dimethylbuta-1,3-diene is possible with complete avoidance of any volatile organic solvents. [ABSTRACT FROM AUTHOR]

Next to economic success, ecological considerations have become increasingly important for companies synthesizing various compounds ranging from bulk chemicals to pharmaceuticals. In this context, the economic and ecological feasibility of asymmetric biocatalytic styrene epoxidation has previously been investigated and compared to chemical alternatives. Although the biotechnological two-liquid phase approach was found to be highly interesting in economic terms, the ecological performance is restrained by the applied organic carrier solvent bis(2-ethylhexyl)phthalate, which is toxic to humans and produced from non-renewable resources. As an alternative carrier solvent, the biodiesel constituent ethyl oleate was tested. Furthermore, the switch from glucose to glycerol as a carbon and energy source was investigated, the latter being a cheap abundant resource, as it is a waste product of the biodiesel and soap industries. Both strategies slightly reduced the productivity and final product titer. An ecological and economic assessment on process level, however, revealed a superior environmental performance (by 13%) with ethyl oleate as the extractive solvent, at the expense of slightly reduced economics (by 9%), whereas glycerol use reduced the performance with respect to both aspects. Based on available data, the application of resting cells was evaluated, providing the opportunity of more efficient carbon utilization via decoupling of growth and biotransformation. Their stability is, however, yet to be improved to achieve competitiveness. In general, this study underlines the potential of ecological and economic assessments for systematic process intensification. Even if advantages of proposed changes seem obvious, their true suitability can only be judged by detailed economic and ecological analyses at the process level. [ABSTRACT FROM AUTHOR]

A biocatalytic synthesis of glycerol carbonate (GlyC), as an added-value product of renewable glycerol, has been developed using a catalytic route in which glycerol (Gly) was reacting with dimethyl carbonate (DMC) in the presence of lipase under solvent-free conditions. The enzyme screening indicated lipase from Aspergillus niger as the most efficient biocatalyst for the GlyC synthesis. After the optimization of the reaction conditions it was established that the best results corresponded to 12% (w/w) Aspergillus niger lipase, to a glycerol : DMC molar ratio of 1 : 10, to an incubation time of 4 h and to an incubation temperature of 60 °C. Consequently, the glycerol conversion was around 74%, the yield in GlyC of 59.3% and the selectivity to GlyC of 80.3%. Recycling experiments demonstrated that the biocatalyst can be successfully used for several reaction cycles (at least 4 times) and confirmed its very high stability under the reaction conditions. [ABSTRACT FROM AUTHOR]

At T≥ 200 °C, in the presence of K2CO3 as a catalyst, an original etherification procedure of non-toxic acetals such as glycerol formal (GlyF) and solketal has been investigated by using dialkyl carbonates as safe alkylating agents. The effects of parameters including the temperature, the reaction time, and the loading of both the catalyst and the dialkyl carbonate have been detailed for the model case of dimethyl carbonate (DMC). Both GlyF and solketal were efficiently alkylated by DMC to produce the corresponding O-methyl ethers with selectivity up to 99% and excellent yields (86–99%, by GC). The high selectivity could be accounted for by a mechanistic study involving a combined sequence of methylation, carboxymethylation, decarboxylation and hydrolysis processes. The O-methylation of GlyF and solketal could be successfully scaled up for multigram synthesis even operating with a moderate excess (5 molar equiv.) of DMC and in the absence of additional solvent. Notwithstanding the advantageous reduction of the process mass index, scale up experiments provided evidence that prolonged reaction times may induce the decomposition of DMC mainly by the loss of CO2. The K2CO3-catalyzed etherification of solketal with other carbonates such as dibenzyl and diethyl carbonate (DBnC and DEC, respectively), proceeded with the same good selectivity observed for DMC. However, at 220 °C, the solketal conversion did not exceed 81% since both DBnC and DEC were extensively consumed in competitive decarboxylation and hydrolysis reactions. [ABSTRACT FROM AUTHOR]

A simple procedure has been developed for the synthesis of enantio- and diastereomerically pure carbohydrate analogues from glycerol and a variety of aldehydes in one pot using a four-enzyme cascade reaction. As a proof of concept of the usefulness of this enzymatic catalytic cascade the naturally occurring azasugar d-fagomine was synthesized. This work highlights the potential value of using enzymes in cascade reactions to selectively form complex products that by previous traditional organic chemistry could only be obtained via repeated isolation and purification of intermediates. [ABSTRACT FROM AUTHOR]

Green solvents made from glycerol change the classical regioselectivity of Biolacta No 5 β-galactosidase, from β(1→4) to β(1→6) linkages when a 2 M concentration was used. In order to explain these results, the non-proteic compounds present in the Biolacta preparation were separated by precipitation with ammonium sulfate and the remaining protein extract was used to set reactions with appropriate organic solvents to find that the regioselectivity towards the β(1→6) isomer is retained. According to proteomic analysis, a 98% homology between Streptococcus pneumoniae and Biolacta β-galactosidase preparation was found. With these data, molecular modelling was done which predicts a tridimensional interaction in the enzyme active site with the donor (GlcNAc) and the water-solvent mixture which explains this phenomenon. [ABSTRACT FROM AUTHOR]

Due to its three hydroxyl groups, glycerol is a potential starting material for various high value fine chemicals such as dihydroxyacetone, tartronic acid and mesoxalic acid. The corresponding oxidation reactions are catalysed by various metals such as palladium, platinum, bismuth or gold. Nevertheless, the selectivity not only depends on the type of the active phase, but is also influenced by numerous parameters such as the metal particles size, the pore size of the support and the pH of the reaction medium. This review not only describes the recent developments in the field of research for new catalysts but also spotlights the role of the reaction conditions as well as the possible transport limitations in this tri-phasic system. Furthermore, an economical analysis of some processes is given, which shows that this is realistic to envision sustainable production of, e.g., dihydroxyacetone. [ABSTRACT FROM AUTHOR]

Esterification of glycerol with acetic acid was studied using a series of Brønsted acidic ionic liquids as catalysts. The results indicate that double SO3H-functionalized ionic liquids show high catalytic activity and fair reusability even at very low catalyst loadings, while the conventional non-functionalized ionic liquids show poor activity. The Brønsted acidity–catalytic activity relationships were also investigated and the results showed that the sequence of the catalytic activity observed in the transformation was in good agreement with the Brønsted acidity order determined by the Hammett method. [ABSTRACT FROM AUTHOR]

While the initial catalytic performances of silica-supported silicotungstic acid are high in the glycerol dehydration reaction, they rapidly decrease with time on stream and the acrolein yield quickly decreases. [ABSTRACT FROM AUTHOR]

Supported Cu-containing bimetallic catalysts were prepared and used to convert glycerol to propanediols. The effects of supports, metals, metal loadings, and impregnation sequences were examined. A synergistic effect was observed between Cu and Ag when they were impregnated on γ-Al2O3. Characterizations revealed that the addition of Ag not only resulted in an in situreduction of CuO, but also improved the dispersion of the Cu species on the support. A CuAg/Al2O3catalyst with optimal amounts of Cu and Ag (Cu/Ag molar ratio 7 : 3, 2.7 mmol Cu+Ag per gram of γ-Al2O3) showed a near 100% selectivity to propanediols with a glycerol conversion of about 27% under mild reaction conditions (200 °C, 1.5 MPa initial H2pressure, 10 h, (Cu+Ag)/glycerol molar ratio of 3/100). Compared with a commercial copper chromite catalyst commonly used for this reaction, the CuAg/Al2O3catalyst had much higher activity and did not need a reduction pretreatment. [ABSTRACT FROM AUTHOR]

Deoxygenation of glycerol in aqueous medium catalyzed by Pt/WO3/ZrO2at relatively low temperatures (110–140 °C) under hydrogen pressure range from 2 to 5 MPa in a fixed-bed continuous-flow reactor gives 1,3-propanediol (1,3-PDO) and n-propanol (n-PrOH) as the predominant products, indicating high selectivity for deoxygenation of the secondary hydroxyl group over the primary hydroxyl groups of the glycerol. The optimum catalyst was prepared by calcination of WO3/ZrO2at 700 °C and loading of 3.0 wt% Pt with W content of 10 wt%. The effect of reaction temperature, hydrogen pressure and initial water content were evaluated to find the optimum reaction conditions. The glycerol conversion and the yield of 1,3-PDO greatly depended on these factors. At 130 °C, 4 MPa and 70.2% conversion, the yield of 1,3-PDO was up to 32.0% (1,3-PDO/1,2-PDO = 17.7). The proposed mechanism for glycerol deoxygenation in aqueous medium over Pt/WO3/ZrO2is an ionic pathway involving proton and hydride ion transfer steps. [ABSTRACT FROM AUTHOR]

The chemoselective dehydrogenation of glycerol was catalyzed by organoiridium derivatives of the type [HIr(cod)L] (cod = 1,5-cyclooctadiene; L = Prn-N(CH2CH2PPh2)2, Et2NCH2CH2N(CH2CH2PPh2)2, o-Me2NC6H4PPh2) using hydrogen acceptors such as acetophenone, cyclohexanone, styrene and benzaldehyde. The catalytic reactions were performed in the absence of a basic cocatalyst in order to avoid decomposition of the desired product, i.e.dihydroxyacetone. Acceptor-less dehydrogenation was also observed either in the absence of a hydrogen acceptor, or as a parallel route, when the reaction was performed in the presence of acetophenone. [ABSTRACT FROM AUTHOR]

The direct conversion of C3sugars (or trioses) to alkyl lactates was achieved using zeolite catalysts. This reaction represents a key step towards the efficient conversion of bio-glycerol or formaldehyde to added-value chemicals such as lactate derivatives. The highest yields and selectivities towards the desired lactate product were obtained with Ultrastable zeolite Y materials having a low Si/Al ratio and a high content of extra-framework aluminium. Correlating the types and amounts of acid sites present in the different zeolites reveals that two acid functions are required to achieve excellent catalysis. Brønsted acid sites catalyse the conversion of trioses to the reaction intermediate pyruvic aldehyde, while Lewis acid sites further assist in the intramolecular rearrangement of the aldehyde into the desired lactate ester product. The presence of strong zeolitic Brønsted acid sites should be avoided as much as possible, since they convert the intermediate pyruvic aldehyde into alkyl acetals instead of lactate esters. A tentative mechanism for the acid catalysis is proposed based on reference reactions and isotopically labelled experiments. Reusability of the USY catalyst is demonstrated for the title reaction. [ABSTRACT FROM AUTHOR]

The direct conversion of C3sugars (or trioses) to alkyl lactates was achieved using zeolite catalysts. This reaction represents a key step towards the efficient conversion of bio-glycerol or formaldehyde to added-value chemicals such as lactate derivatives. The highest yields and selectivities towards the desired lactate product were obtained with Ultrastable zeolite Y materials having a low Si/Al ratio and a high content of extra-framework aluminium. Correlating the types and amounts of acid sites present in the different zeolites reveals that two acid functions are required to achieve excellent catalysis. Brønsted acid sites catalyse the conversion of trioses to the reaction intermediate pyruvic aldehyde, while Lewis acid sites further assist in the intramolecular rearrangement of the aldehyde into the desired lactate ester product. The presence of strong zeolitic Brønsted acid sites should be avoided as much as possible, since they convert the intermediate pyruvic aldehyde into alkyl acetals instead of lactate esters. A tentative mechanism for the acid catalysis is proposed based on reference reactions and isotopically labelled experiments. Reusability of the USY catalyst is demonstrated for the title reaction. [ABSTRACT FROM AUTHOR]

Herein we show that glycerol can be considered as a promising cheap and green solvent for the regioselective β,β-diarylation of alkenes. Whereas this reaction is generally catalyzed under an inert atmosphere by expensive phosphine or carbene-palladium complexes, we show here that the diarylation of alkenes can be conveniently achieved in glycerol in the presence of air-stable palladium nanoparticles. These palladium nanoparticles were stabilized over a sugar-based surfactant derived from biomass. By an adjustment of the reaction temperature, we were able to control the mono- and diarylation step of alkenes, thus offering a convenient route to unsymmetrical diarylated alkenes. At the end of the reaction, the diarylated alkenes were cleanly and selectively extracted from the glycerol-palladium catalytic phase using supercritical carbon dioxide, thus affording a convenient purification work-up. Within the framework of green chemistry, this work combines (i) catalysis in a cheap, safe and sustainable medium, (ii) easily made and air-stable palladium nanoparticles as the catalyst, and (iii) a clean and selective extraction of the reaction products with supercritical carbon dioxide. [ABSTRACT FROM AUTHOR]

Many multicomponent reactions (MCRs) of 1,3-disubstituted 5-pyrazolones and formaldehyde were developed in environmentally benign solvent systems. Styrenes, vinylferrocene and 2-phenylindoles could easily react, under solvent-free conditions or in glycerol solvent, with 1,3-disubstituted 5-pyrazolones and paraformaldehyde in the absence of any catalyst to afford a variety of complex skeletons in moderate to excellent yields. Particularly, these MCRs are proved to be combinable with the synthesis of 1,3-disubstituted 5-pyrazolones from phenylhydrazines and β-ketone esters in glycerol or a carboxylic acid-functionalized ionic liquid, [MIm-CO2H]BF4. Therefore, some two-step sequential reactions of phenylhydrazines, β-ketone esters, formaldehyde and styrenes or indoles were developed for the first time. All these MCRs were conducted in environmentally benign solvent systems that not only minimize generation of wastes but also simplify the work-up procedure. [ABSTRACT FROM AUTHOR]

Sulfonic acid-functionalized mesostructured silicas have demonstrated excellent catalytic behaviour in the acetalisation of glycerol with acetone to yield 2,2-dimethyl-1,3-dioxolane-4-methanol, also known as solketal. This molecule constitutes an excellent compound for the formulation of gasoline, diesel and biodiesel fuels. The activity achieved with arenesulfonic acid-functionalized silica is comparable to that displayed by Amberlyst-15. Optimal production of solketal over arenesulfonic acid mesostructured silica has been established for a reaction system consisting of three consecutive 2-step batches (30 min under reflux and an evaporation step under vacuum), and using a 6/1 acetone/glycerol molar ratio. The use of lower grades of glycerol, such as technical (purity of 91.6 wt%) and crude (85.8 wt%) glycerol, has also provided high conversions of glycerol over sulfonic acid-modified heterogeneous catalysts (84% and 81%, respectively). For refined and technical glycerol the catalysts have been reused, without any regeneration treatment, up to three times, keeping the high initial activity. However, the high sodium content in crude glycerol deactivates the sulfonic acid sites by cation exchange. This deactivation is readily reversed by simple acidification of the catalyst after reaction. [ABSTRACT FROM AUTHOR]

The article focuses on copper oxide/zinc oxide catalyst prepared by an oxalate gel method which is used for hydrogenolysis of glycerol with the help of transmission electron microscopy (TEM). It also explores the impact of modifying solvent and reaction temperature on catalyst deactivation. It discusses the conditions under which hydrogenolysis reaction is carried in an autoclave which includes optimum temperature range between 190 to 225 degree Celsius and pure form of glycerol.

The irreversible adsorption and decomposition of glycerol and other polyhydric alcohols over ruthenium metal at 298–353 K has been examined in a recirculating microreactor system. The quantity of glycerol (GO), propylene glycol (1,2-propanediol, herein PG), ethylene glycol (EG), or 1,3-propanediol (1,3-PDO) adsorbed on a reduced and evacuated bulk Ru metal powder at saturation is 0.8 ± 0.2 μmol/g, a value approximately one-tenth that of CO adsorbed (9.0 μmol/g) on the same material. The quantity of polyol adsorbed is independent of temperature, but is strongly affected by the condition of the Ru surface—saturating the metal surface with hydrogen prior to exposure to the polyol significantly reduces the quantity of polyol adsorbed. When they are present together in solution, GO adsorbs more readily than PG, to the point of excluding PG from adsorbing when excess GO is present. Removal of adsorbed species in their original form by heating or flushing with water is not possible, but all carbon is accounted for as desorbed methane when the Ru catalyst is heated under hydrogen. [ABSTRACT FROM AUTHOR]

Glycerol was used, for the first time, as a green and effective promoting medium for electrophilic activation of aldehydes, and with which, a catalyst-free system for some reactions that conventionally carried out using acid catalysts, such as synthesis of di(indolyl)methanes, 3,4,5,6,7,9-hexahydro-9-aryl-1H-xanthene-1,8(2H)-dione and 1-oxo-hexahydroxanthenes, was developed. [ABSTRACT FROM AUTHOR]

A family of glycerol-based solvents, consisting of eighteen 1,3-dialkoxy-2-propanols and 1,2,3-trialkoxypropanes, both symmetrically and unsymmetrically substituted at terminal positions, has been tested as new solvents in cyclooctene epoxidation with hydrogen peroxide, using a diselenide catalyst, but also without a catalyst. A quantitative relationship between the reactivity and solvent polarity properties has been developed through statistical linear regression analyses, and the predictive ability of the resulting equation has been demonstrated. [ABSTRACT FROM AUTHOR]

The vapour pressures of several ionic liquids, liquid polymers and derivatives of glycerol were investigated by thermogravimetric analysis (TGA). The experimental method is described and discussed. Vapour pressure data for various solvents with low vapour pressures are reported at 100–120 °C. The thermogravimetric method for vapour pressure measurement is useful for the rapid screening of solvents. Ionic liquids have a low but detectable vapour pressure at 100–120 °C. The vapour pressures of liquid polymers such as poly(ethylenimine) and polyethylene glycols are in the same range, which might make these substances a less expensive alternative to ionic liquids. [ABSTRACT FROM AUTHOR]

Different types of acidic heterogeneous catalysts, including sulfonic resins, zeolites and grafted silicas are used for the synthesis of mono-ethers of glycerol using ethanol as the alcohol. The study shows that the performances of the catalysts are governed by both the acidity and the polarity of their surface. Materials with strong hydrophobic character are not active as they do not allow the adsorption of the glycerol. On the other hand a strong adsorption of glycerol on the polar surfaces leads to low activity as well. The best compromise has been found by using sulfonic-acid polystyrene resins of the Amberlyst family and zeolites with intermediate aluminium contents. [ABSTRACT FROM AUTHOR]

The use of bio-renewable resources, such as glycerol, a by-product from bio-diesel manufacture, can provide a viable way to make valuable products using greener technology. In particular, glycerol can be reduced to give 1,2-propanediol that can then be selectively oxidised to lactate, which has immense potential as a monomer for the synthesis of biodegradable polymers. We show that gold-palladium alloy catalysts can be very effective for the selective oxidation of 1,2-propanediol to lactate. Two supports, TiO2and carbon, and two preparation methods, wet impregnation and sol-immobilisation, are contrasted. The addition of palladium to gold significantly enhances the activity and retains the high selectivity to lactate using O2as oxidant (we observe 96% lactate selectivity at 94% conversion). Use of hydrogen peroxide is also possible but lower activities are observed as a result of the reaction conditions, but in this case no marked enhancement is observed on addition of palladium to gold. Comparison of the activity for C3alcohols shows that the reactivity decreases in the order: glycerol > 1,2-propanediol > 1,3-propanediol ∼ 1-propanol > 2-propanol. The use of a sol-immobilisation preparation method as compared to impregnation leads to alloy catalysts with the highest activity for lactate formation from the oxidation of 1,2-propanediol; the origins of these activity trends are discussed. [ABSTRACT FROM AUTHOR]

Glycerol is a well-known renewable chemical, and its effective transformation to valuable chemicals accords well with the principles of green chemistry. In this work, a series of Ru-Cu bimetallic catalysts were prepared using cheap and abundant clay, bentonite, as the support. Bentonite was modified with a functional ionic liquid 1,1,3,3-tetramethylguanidinium lactate (TMGL) in an attempt to develop highly efficient catalysts. Hydrogenolysis of aqueous solution of glycerol was performed with the immobilized Ru-Cu catalyst under temperatures of 190–240 °C and pressures of 2.5–10 MPa. The bimetallic catalysts were very efficient for promoting the hydrogenolysis of glycerol. 100% of glycerol conversion and 85% yield of 1,2-propanediol could be achieved at 230 °C and 8 MPa. The conversion of glycerol and the selectivity to 1,2-propanediol did not decrease after the catalyst was used 5 times. TMGL played a crucial role in fabricating the new catalysts. The catalysts were characterized by FT-IR, XPS, SEM and TEM, and the reasons for the excellent performances of the catalyst were also discussed. [ABSTRACT FROM AUTHOR]

Organoiridium derivatives of the type Ir(diene)(N-N)X (diene = 1,5-hexadiene,1,5-cyclooctadiene; N-N = 2,2′-bipyridine, 1,10-phenanthroline and substituted derivatives; X = Cl, I) catalyze the hydrogen transfer reaction from glycerol to acetophenone, yielding dihydroxyacetone and phenylethanol. The catalytic reactions are performed at temperatures of 100 °C or higher, in the presence of a basic cocatalyst. The effect of experimental conditions on overall conversion and catalyst lifetime is discussed, as well as on the degradation of dihydroxyacetone, which can lead to an apparent decrease of selectivity of the catalytic reaction. [ABSTRACT FROM AUTHOR]

Continuous esterification of glycerol with acetic acid was investigated in supercritical carbon dioxide (scCO2) using Amberlyst 15® as a heterogeneous catalyst. The effect of pressure at (65–300) bar on the substrate conversion and the reaction yield and selectivity was studied. With increasing pressure, the percent of total yield and conversion remain almost unaffected and the selectivity of monoacetin synthesis increases while the selectivity for triacetin stays relatively unchanged. The effect of temperature on the yield, conversion, and the selectivity at (100–150) °C was also investigated. With increasing temperature from 100 to 140 °C, the selectivity for monoacetin decreases while for tri- and diacetin slightly increases. In contrast, with further increase in temperature, from 140 °C to 150 °C, the selectivity of monoacetin synthesis increases while that of diacetin decreases. By increasing the molar ratio of acetic acid to glycerol to 24, a selectivity of 100% was achieved for 2 h while the yield was 41% for the continuous triacetin synthesis in scCO2. When neat scCO2as solvent with no catalyst was used, only monoacetin with 29% conversion was synthesized. The catalyst durability was also studied by monitoring the reaction for 25 h. The results show that the catalyst retains its activity even for 25 h but the selectivity for triacetin synthesis declines from 100% to about 60%. [ABSTRACT FROM AUTHOR]

Aerobic oxidation of glycerol over metal oxide supported gold nanoparticles in methanol results in the formation of dimethyl mesoxalate in selectivities up to 89% at full conversion. The oxidative esterification takes place in methanol, acting both as solvent and reactant, and in the presence of base. Thus, it constitutes a direct transformation of the glycerol by-product phase from biodiesel production or from glycerol obtained e.g. by fermentation. Au/TiO2 and Au/Fe2O3 was found to have similar catalytic activity, whereas Au/C was inactive. 1,2-Propanediol was oxidized to methyl lactate with a selectivity of 72% at full conversion, while 1,3-propanediol yielded methyl 3-hydroxypropionate with 90% selectivity at 94% conversion. Methyl 3-hydroxy propionate can be easily converted into methyl acrylate, which is then a green polymer building block. [ABSTRACT FROM AUTHOR]

A Lewis basic mixture of quaternary ammonium salts with glycerol has been used to extract excess glycerol from biodiesel formed from the reaction of triglycerides with ethanol in the presence of KOH. The effect of the cation on the partition coefficient of glycerol was determined, together with the time taken for the systems to reach equilibrium. Protocols were also investigated for the separation of glycerol from the quaternary ammonium salt mixtures. [ABSTRACT FROM AUTHOR]

Glycerol is a main byproduct in the biodiesel production process, and the effective utilization of glycerol can contribute to biodiesel promotion. One of the possible methods is the catalytic conversion of glycerol to valuable chemicals, and this can also agree with the concept of green chemistry in terms of the utilization of renewable resources. Catalytic performance of supported metal catalysts (metal: Rh, Ru, Pt, Pd support: active carbon, SiO2, Al2O3) was evaluated in the reaction of glycerol aqueous solution under H2. It is found that Rh/SiO2 exhibited higher activity and higher selectivity to hydrogenolysis products such as propanediols and propanols than Ru/C catalysts at low temperature (393 K). We also investigated the additive effect of ion-exchange resin (Amberlyst). Regarding the reaction route in the reaction of glycerol, it is suggested that the consecutive hydrogenolysis of propanediols to propanols on Rh/SiO2 can proceed via 1,2-propanediol, while it can proceed on Ru/C via 1,3-propanediol. [ABSTRACT FROM AUTHOR]

Thermophysical and bionotox properties of a new class of natural solvo-surfactants, glycerol 1-monoethers, were investigated in comparison with widespread but harmful glycol ethers. Vapour pressures and heats of vaporization were measured between 25 °C and 50 °C, and calculated thanks to two group contribution methods. Evaporation rates and Hansen parameters, evaluated from TGA measurements and group contributions respectively, were compared as well. Bionotox properties, i.e. cytotoxicity, irritating power and biodegradability, were evaluated experimentally. Glycerol 1-monoethers turned out to be less volatile than glycol derivatives, but contrary to the latter they will not be considered as VOCs. Toxicities and irritating powers are equivalent and increase with increasing alkyl chain length, i.e. with increasing amphiphilicity. Glycerol ethers are degradable at lower concentrations compared to glycol compounds, which is related to their higher interfacial activity. [ABSTRACT FROM AUTHOR]

Selective conversion of glycerol into 1,2-propanediol in the presence of a Pd/Fe2O3catalyst, under inert atmosphere, is reported for the first time; the hydrogen necessary for the hydrogenolysis reaction derives from the dehydrogenation of the solvent (2-propanol or ethanol), promoted by supported palladium, itself reduced “in situ” by alcohols. [ABSTRACT FROM AUTHOR]