Search

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.