In this study, zeolites prepared from fly ash pretreated with hydrochloric acid were used for catalysis. The synthesis was performed by a pre-fusion hydrothermal activation with low crystallization ...temperature (60 °C) and using both seawater and distilled water. The synthetic zeolites were tested via the base-catalyzed gas-phase alkylation of phenol using diethyl carbonate as an innovative alkylating agent, thus obtaining phenol conversions up to 95% with a selectivity of more than 85% in phenetole. These data indicate that the newly-formed zeolites are very selective for the O-ethylation of phenol also at high temperatures. Moreover, the results show that the zeolites formed from fly ash have a greater catalytic activity than that shown by commercial NaY and synthetic MgO, which were chosen as basic reference catalysts.
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•Zeolites were prepared from acid pre-treated fly ash by hydrothermal process.•Synthetic zeolites were used for gas-phase catalysis.•Zeolites were tested in base-catalyzed phenol alkylation with diethylcarbonate.•Phenol conversions up to 95% was achieved, with a selectivity to phenetole higher than 85%.•The catalytic activity of the synthetic zeolites was higher than that of commercial NaY.
Bio-feedstocks are destined to replace fossil fuels for specialty chemicals, but current bio-refineries mainly ferment monosaccharides to ethanol, a commodity chemical that is blended with gasoline ...as a fuel. The market price of biofuels is several-fold lower than specialty chemicals and monomers. Rather than cracking the C6-sugars ethanol, here, develop dehydration and oxydehydration processes to valuable platform C6-chemicals like 5-hydroxymethyl furfural (HMF), 2,5-dimethyl furan (DFF), and 2,5-furandicarboxylic acid. This gas-phase process atomizes an aqueous solution of fructose into a fluidized bed reactor operating at 350°C. The solution forms an aerosol (droplet size of 30µm), which contacts the hot Pt-WO3/TiO2 catalyst and reacts to HMF rather than caramelizing. The maximum yield reached 21% and it increased slightly with temperature, and decreased with increasing catalyst inventory; it was less sensitive to O2 concentration, Pt loading on the catalyst, liquid feed flow rate, and fructose feed concentration. At the optimal condition, selectivity continued to increase with time even after 3h reaction. Selectivity to 2,5-diformyl furan reached 42% at 250°C with HMF as a feedstock.
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•Pt-WO3 oxydehydrates fructose to furans in the gas phase: <300 °C, <20% selectivity.•By-product gases from fructose oxydehydration include CO2, CH4, and CO.•The CO2:CH4 product ratio is close to 1: stoichiometric fructose decomposition.•2,5-diformyl furan selectivity from HMF as a feedstock approaches 50%.•Operational difficulties included agglomeration at the sparger and coke formation.
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•Efficient catalytic system for ethanol homologation to biofuel.•Suitable transformation of wine waste bio-ethanol to second generation biofuel.•Boosting the Guerbet reaction: a ...tandem homogeneous catalytic solution.
The catalytic activity of anionic ruthenium complexes toward the transformation of bio-ethanol to 1-butanol and higher alcohols is found to be dependent on the imidazolium counterion. After the identification of a parallel reaction involving the catalyst in hydrogen evolution, conversion and selectivity are impressively boosted by the addition of p-benzoquinones as co-catalysts. The catalytic system avoids the side reaction and led to highly competitive conversions up to 88% (0.2 % mol ruthenium catalyst loading, 1.5 % mol benzoquinone loading). Butanol and higher alcohols are produced in yields up to 85% (overall selectivity 97%) as a mixture of valuable alcohols for advanced biofuel and lubricants applications. The catalytic system can be recycled and the reaction shows comparable efficiency on a real matrix (alcohol from wine production chain wastes) even in the presence of significant amounts of water, thus closing a hypothetic economic circle. A reaction mechanism is proposed for the most promising ruthenium complex working in cooperation with the most efficient co-catalyst: p-benzoquinone.
In this study we explore the use of Ga as a new component in MgO‐SiO2 catalysts for the Lebedev reaction (the one‐pot conversion of ethanol to butadiene). Several characterisation techniques (XRD, ...temperature‐programmed desorption of NH3, BET measurements, IR spectroscopy) and in situ spectroscopic studies (DRIFTS‐MS) were performed with the aim to correlate the properties of the modified materials with the catalytic results. We concluded that the wet impregnation of Ga3+ on the MgO‐SiO2 catalyst creates new Ga−O(H)−Si sites. These sites interact strongly with alcohol and not only facilitate its dehydrogenation to acetaldehyde and its transformation into the intermediate crotyl alcohol but also enhance the dehydration of the latter because of an improved acidity. However, an appropriate amount of gallium oxide is needed to avoid excessive acidity, which is conducive to an increased selectivity to ethylene.
Feel the Lebedev: Gallium oxide is an activity and selectivity promoter for MgO‐SiO2 catalysts for the direct transformation of ethanol into butadiene (Lebedev process).
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•Solvent-free conversion of levulinic acid to succinic acid with hydrogen peroxide and H2WO4.•Formation of an adduct between the catalyst and the substrate, which enhances the ...regioselectivity.•Maximum conversion of 48% with 75% selectivity to succinic acid, after 6 h.•A new green process for synthesize succinic acid from bio-sourced levulinic acid.
Levulinic acid is produced from the acidic aqueous degradation of 5-hydroxymethylfurfural, with potential applications in bio-value added chemicals synthesis. Here, we report for the first time, the Baeyer-Villiger oxidation of levulinic acid to succinic acid, with hydrogen peroxide and tungstic acid at mild conditions and without any organic solvent. We investigated the effects of time, amount of reagent-to-catalyst molar ratio and H2O2-to-levulinic acid molar ratio. The maximum succinic acid selectivity was 75% with a levulinic acid conversion as high as 48%, after 6 h at 90 °C. We propose a reaction mechanism based on results obtained from the reactivity of the intermediates. The catalyst interacts with the substrate, forming a cyclic species that enhances the formation of succinic acid versus 3-hydroxypropanoic acid.
Green chemistry is part of the chemical industry’s response to calls for improved environmental responsibility. It is also one of the industry’s several paths to redemption from its erstwhile ...infamous reputation as one of the most polluting sectors. We studied the impacts of implementing some of these principles on the production of methyl methacrylate (MMA), the monomer of PMMA popularly known as acrylic glass. This study used life cycle assessment (LCA) methodology to compare the potential environmental impacts of three different approaches to the production of MMA. Two of these are established industrial pathways: the acetocyanohydrin process (ACH-MMA) and the Alpha Lucite process (AL-MMA), which represent the conventional and a fast-rising industrial route, respectively, while the third, the in situ formaldehyde process (inFAL-MMA) is a lab-based process. The scenarios were evaluated using cumulative energy demand (CED) and the ReCiPe 2016 impact assessment methods. The results obtained highlighted some hotspots that can benefit from process improvements and careful material and energy source selection. It also underscored that AL-MMA can record significant improvements in environmental performance by reducing the overall resource intensity of the process. inFAL-MMA synthesis was adjudged to be the most evolved of the three alternatives with respect to green chemistry principles; hence, the study sought to investigate possible environmental gains attributable to this. Some limitations of the methodology uncovered during the study necessitated the use of an additional tool for further assessment of the potential risk. Thus, the GREEN MOTION was adopted to examine this relationship. Overall, the study established hotspots and areas for process improvements in the scenarios examined. It also confirmed the importance of different factors like data quality, degree of process optimization, energy source, and others on the results that can be obtained in a LCA.
Continuous-flow, gas-phase, catalytic transfer hydrogenation of methyl levulinate with ethanol over two different zirconia crystalline phases
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•Continuous-flow catalytic transfer ...hydrogenation of methyl levulinate with ethanol.•Structure-activity relationship of the effect of the zirconia crystalline structure.•Complementary approach with characterisation, experimental, DFT and NMR relaxation studies.
The depletion of fossil resources is driving the research towards renewable alternatives, like lignocellulosic biomass. Therefore, the development of efficient continuous-flow processes, allowing to achieve better productivity compared to batch processes, will play a crucial role in promoting a sustainable transition. In this context, we report on the continuous-flow, gas-phase, catalytic transfer hydrogenation (CTH) of methyl levulinate and ethanol over zirconia catalysts, in particular focusing on the effect of two different crystalline phases (i.e. monoclinic, m-ZrO2, and tetragonal, t-ZrO2) on catalyst performance. An in-depth catalyst characterisation was coupled with both computational and 1H-NMR relaxation studies to assess the structure-activity relationship, providing fundamental insights into the catalytic process and future catalyst optimization. The results, indicate that the higher Lewis acidity and basicity along with the lower affinity with ethanol of m-ZrO2 with respect to t-ZrO2 are responsible for the promotion of undesired oligomerisation reactions of angelica lactones responsible for catalyst deactivation.
Ordered mesoporous CeO2 has been prepared via a hard-template method using SBA-15 as a structure-directing agent. Leaching with NaOH and thermal treatment at 500 °C enabled the removal of the ...inorganic template, thus resulting in the formation of long-range ordered CeO2. Nevertheless, small amounts of silica were present in the final oxides. The resulting CeO2 samples were used as supports for Au nanoparticles and the prepared catalysts were tested in the selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA). Fine tuning of the silica template removal process was necessary to prepare active materials, by maximizing the close contact between the metal and the support, and thus confirming the important role of ceria defects in 5-hydroxymethylfurfural oxidation to 2,5-furandicarboxylic acid.
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•CeO2 with high surface area and a controlled morphology has been prepared by nanocasting using SBA-15 as template.•Gold–support interaction is crucial for favoring catalytic activity.•The fine tuning of the silica template removal process leads to the optimization of HMF oxidation to FDCA.
