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High-pure crude glycerol, obtained from the transesterification of coconut oil with ethanol using lipase enzyme-type as biocatalyst, has been used for the acetalization of furfural with several SAPO 5 and SAPO 34 catalysts. SAPOs were prepared using microwaves and conventional heating for comparison, and were characterized by X-ray diffraction, nitrogen physisorption, elemental analysis, thermogravimetry of adsorbed cyclohexylamine and scanning electron microscopy techniques. The use of microwaves allowed us the incorporation of slightly higher amounts of silicon into the aluminophosphate structure, and the preparation of the materials in much shorter preparation times, with the subsequent energy saving. Additionally, the SAPOs prepared with microwaves showed lower crystallinity but higher surface area than those prepared by conventional heating. Comparable catalytic results were obtained when these catalysts were tested for the acetalization of furfural with commercial or with the crude glycerol obtained by biocatalytic transesterification of coconut oil, leading to very high selectivity values to the desired mixture dioxane + dioxolane (93–100 %), which can be used as biofuel additives, for conversion values between 60 and 73 %, as determined by gas chromatography. This confirmed the high purity of the glycerol obtained by the biocatalytical process, as previously observed by 1H NMR. SAPO 34 catalysts showed higher conversion than SAPO 5 catalysts due to their higher amount of more accessible Brønsted acid sites, related to their structure. Interestingly, catalysts prepared with microwaves resulted in slightly higher conversion values than those prepared by conventional heating. This can be explained by the incorporation of higher amounts of silicon in the framework

© 2020 The Korean Society of Industrial and Engineering Chemistry This study evaluates the techno-economic feasibility to produce tert-butyl ethers of glycerol in Colombia using glycerol obtained from biodiesel production. The major drawback of this process is related to the high costs associated to the isobutylene reagent used for this reaction. Three possible scenarios, using isobutylene: glycerol molar ratios of 2:1 and 4:1, have been evaluated by simulation and techno-economical assessment using pure isobutylene, C4 fraction and a mixture of C4 and isobutylene as well as a refining stage for crude glycerol. The desired product, a mixture of di- and tri- ethers of glycerol (h-GTBE) was obtained in high amounts for the three scenarios (92–99 wt.%) and a direct relation between production cost and raw material cost was established. The prices for h-GTBE were higher than the proposed selling prices; however, the formation of byproduct (C4 fraction) can make the process competitive. h-GTBE production did not have a competitive price for any scenario at high isobutylene: glycerol molar ratio. The production price was lowered by around 20% for all scenarios when crude glycerol was considered. Finally, competitive price of h-GTBE (0.96 $/kg) and NPV positive was obtained using a mixture of C4 and isobutylene and crude glycerol.

© 2020 Elsevier B.V. Nickel catalysts supported on mesoporous clays with different acid properties, such as montmorillonite MK-10, Al-pillared montmorillonite, mesoporous Na-saponite and mesoporous H-saponite, were prepared, characterized and tested for the hydrogenation of furfural to tetrahydrofurfuryl alcohol (THFA). Clays were also modified introducing basicity through magnesium oxide in different amounts. Catalysts with higher acidity or low amounts of metallic centres favoured deactivation and/or selectivity to the non-desired products. Interestingly, the addition of MgO both neutralized the acidity of the montmorillonite supports and improved the hydrogenation of the furanic ring, resulting in higher selectivity to THFA. The best catalyst was the one prepared with montmorillonite MK-10 covered by 30 wt% of magnesium oxide and with 8.8 % of the Ni metal phase achieving total conversion and total selectivity to THFA. The activity of this catalyst was maintained after several reuses.

© 2020 Elsevier B.V. Several Ni, Cu and Ni-Cu catalysts supported on mesoporous hectorite were prepared, characterized and tested for the hydrogenation of commercial furfural to obtain tetrahydrofurfuryl alcohol (THFA). The highest selectivity to THFA (95 %) for a total conversion was achieved with the Ni-Cu catalyst prepared with a Ni:Cu molar ratio of 1:1 after 4 h of reaction. This can be explained by the formation of NiCu alloy in high amounts for this sample (88 %), as detected by XRD. The lower selectivity to THFA obtained with other bimetallic catalysts prepared with Ni:Cu molar ratios of 6:1 and 1:6 were attributed to the lower percentage of NiCu alloy together with the lowest Ni richness of the NiCu alloy. Additionally, the best catalyst resulted in a yield to THFA of 90 %, in the toluene phase, and 80 % in the aqueous neutralized phase, when using a biomass extract of furfural obtained from almond shells instead of commercial furfural. After several reuses of the catalyst employed in the toluene phase, some decrease of THFA was observed due to the increase of the crystallite size of the Cu phase, as observed by XRD, that should decorate the active NiCu alloy particles.

© 2019 Elsevier B.V. Acidity and basicity of four hydrocalumite-type materials were studied by infrared spectroscopy through the adsorption of pivalonitrile and acetonitrile, as probe molecules. Samples were prepared by coprecipitation of the corresponding chloride salts with and without ultrasounds and later aging by refluxing under microwaves or by conventional heating. After pivalonitrile adsorption, the samples outgassed at room temperature showed very weak acidity. The number of Lewis acid sites increased after activation at 100 °C, and stronger Lewis acid sites were detected after outgassing at 400 °C. Moreover, these samples showed strong basicity due to the O2– anions, as evidenced by the formation of (CH2CN)− anions after acetonitrile adsorption at high temperature. Additionally, coprecipitation under ultrasounds seems to enhance the basicity of the resulting hydrocalumite. This could explain the higher activity observed for the sample synthesized under ultrasounds when tested as catalyst for the transesterification of glycerol with dimethylcarbonate.

The effect of using microwaves or conventional heating for synthesizing/modifying several acid micro- and mesoporous materials have been studied by testing them as catalysts for the acetalization of glycerol with furfural to obtain 1,3-dioxane and 1,3-dioxolane (fuel additives). Microwaves allowed us the incorporation of higher amounts of sulfonic groups in SBA-15 and montmorillonite MK-10 catalysts whereas for zeolite samples the differences were not significant. The catalysts prepared/modified with microwaves led to higher conversion but slight lower selectivity to the desired products than those prepared by conventional heating. Sulfonated montmorillonite MK-10 catalysts showed high conversion (62-68%) and the highest selectivity values to the desired products (72-86%). This has been related to the higher surface density of Brønsted acid sites observed for these catalysts. The presence of Lewis acid centres in the ReOx/hectorite catalyst increased the formatron od dioxane.

Several hydrocalumite-type materials and some of their calcined forms have been tested for the catalytic transesterification of glycerol towards glycerol carbonate under microwaves, and by conventional heating for comparison. Microwaves slightly increased conversion but greatly increased selectivity to glycerol carbonate for all catalysts while the selectivity to glycidol was similar. Glycerol conversion values were 63-95% in microwaves and 61-91% by conventional heating, while selectivity to glycerol carbonate values were 53-92% in microwaves and 30-80% by conventional heating. Interestingly, microwaves favored transesterification since the sum of the selectivity values to glycerol carbonate and glycidol was higher than when using conventional heating.

Europium-doped La2O3 nanocrystalline powders with sizes ranging from 4 nm to 300 nm have been obtained by the modified Pechini, hydrothermal with conventional furnace, hydrothermal with microwave furnace, and precipitation with ultrasonic bath methods. X-ray diffraction techniques were used to study the evolution of the prepared gels towards the desired crystalline phase. We determined the size and the morphology of the nanoparticles by electronic microscopy. Finally, we studied and analyzed the luminescence properties of the trivalent europium in the hexagonal La2O3 nanocrystals by photoluminescence and cathodoluminescence.

Filiació URV: SI, This study explores the use of glycidol, as alternative to glycerol, to improve the selectively to 1,3-propanediol (PrD) by hydrogenolysis. The reaction was performed using Ni (with different Ni wt %) supported on an acid delaminated saponite catalysts which are cheaper compared to the expensive catalysts needed to favor the 1,3-PrD formation by glycerol hydrogenolysis. An increase in metallic area and a decrease in the catalyst acidity resulted in higher conversion and selectivity to propanediols (1,2- + 1,3-PrD). An acid activation of glycidol during hydrogenolysis promoted the 1,3-PrD formation and increased the 1,3-PrD/1,2-PrD ratio. For the catalyst prepared with 40 wt % Ni loading, an increase in the reaction temperature to 423 and 453 K led to higher 1,3-PrD/1,2-PrD ratio. The highest 1,3-PrD yield (29%) and 1,3-PrD/1,2-PrD ratio (0.97) at total conversion were obtained at 453 K, after 1 h. The overall 1,3-PrD yield from glycerol, assuming a two-step synthesis (Glycerol  Glycidol  1,3-PrD) and a yield of 78% for the first step, should be around 23%. This value is comparable to that reported for the hydrogenolysis of glycerol using noble metal catalysts.

The effect of the preparation conditions of several calcined Ca/Al layered double hydroxide compounds (CaAl-LDH) on the catalytic transesterification of glycerol with dimethyl carbonate to obtain glycerol carbonate has been studied. The CaAl-LDH precursors were prepared by aging under microwaves or conventional heating, and using chlorides or nitrates as interlayer anions. Calcination conditions, such as temperature, time and calcination system, were modified. After 3 h of reaction, the catalysts obtained by calcination at 450 ºC for 15 h in air exhibited moderate-high glycerol conversion (46-76%) and moderate selectivity to glycerol carbonate (41-65%). Calcination at 450 ºC at longer calcination time or the use of a dynamic inert-atmosphere system during calcination led to higher conversion (89-94%) and higher selectivity to glycerol carbonate (72-73%). This has been related to the higher basicity of these catalysts. Finally, calcination at 750 ºC resulted in high conversion (88-98%) and high selectivity to glycerol carbonate (60-85%) due to the presence in the catalysts of highly basic CaO. Several catalytic reuses favoured the decarboxylation of glycerol carbonate resulting in the formation of higher amounts of glycidol (42%). The progressive loss of conversion and selectivity to glycerol carbonate observed has been attributed to the loss of some CaO basic centres during reaction.

Filiació URV: SI, Ni and Cu mono- and bi-metallic catalysts modified with various types of acid oxides MOx (M = Mo, V, W and Re) were tested for hydrogenolysis of glycidol, as alternative route to hydrogenolysis of glycerol to obtain 1,3-propanediol. Characterization results revealed that the presence of modifiers affected dispersion and reducibility of the NiO particles, and the strength and amount of the acid sites. Among the modifiers tested, Re showed the highest activity, high propanediols selectivity and the highest 1,3-PrD/ 1,2-PrD ratio. Ni-Cu/Re ratio was optimized to improve the catalytic activity. The best catalytic result, with 46 % 1,3-PrD yield and 1,3-PrD/1,2-PrD ratio of 1.24, was obtained when monometallic Ni catalyst at 40 wt % loading and modified with 7 wt % Re was used at 393 K, 5 MPa H2 pressure after 4 h of reaction. The overall 1,3-PrD yield starting from glycerol and assuming a two-step synthesis (Glycerol  Glycidol  1,3-PrD) and a yield of 78% for the first step, would be 36 %. This 1,3-PD yield is the highest for non-noble metal catalyzed reaction and is comparable to direct hydrogenolysis of glycerol using noble metal catalysts, at longer time and high H2 pressure.

H- and Na-saponite supports have been prepared by several synthesis approaches. 5% Cu/saponite catalysts have been prepared and tested for soot combustion in a NOx + O-2 + N-2 gas flow and with soot and catalyst mixed in loose contact mode. XRD, FT-IR, N-2 adsorption and TEM characterization results revealed that the use of either surfactant or microwaves during the synthesis led to delamination of the saponite support, yielding high surface area and small crystallite size materials. The degree of delamination affected further copper oxide dispersion and soot combustion capacity of the Cu/saponite catalysts. All Cu/saponite catalysts were active for soot combustion, and the NO2-assisted mechanism seemed to prevail. The best activity was achieved with copper oxide supported on a Na-saponite prepared at pH 13 and with surfactant. This best activity was attributed to the efficient copper oxide dispersion on the high surface area delaminated saponite (603 m(2) g(-1)) and to the presence of Na. Copper oxide reduction in H-2-TPR experiments occurred at lower temperature for the Na-containing catalysts than for the H-containing counterparts, and all Cu/Na-saponite catalysts were more active for soot combustion than the corresponding Cu/H-saponite catalysts.

10.1016/j.clay.2013.05.006, Friedel's salt [Ca2Al(OH)6]Cl·2H2O, commonly known as hydrocalumite, was synthesized by co-precipitation following different aging treatments, using microwave irradiation or conventional heating and by refluxing or in autoclave, with the aim of decreasing the aging times (24 h) employed when aging by conventional heating or at room temperature. Hydrocalumites were characterized by XRPD, FT-IR, N2 physisorption, ICP-OES, TEM, TEM-electron diffraction and TGA techniques. The use of microwaves favors a faster crystalline growth in the stacking direction whereas the use of autoclave improves the lamellar crystallinity. The highest crystallinity was found for the sample aged with microwave irradiation by autoclaving at 453 K for 1 h. This sample presented the highest crystallite size in the stacking direction (76 nm), the largest lamellar crystals (4000 nm) with R3c symmetry, and the highest dehydration- and dehydroxylation temperatures.