20411-31-8

This work investigates the use of MgFe mixed oxides, derived from layered double hydroxides (LDH) with Mg/Fe molar ratio ranging from 1 to 4, as base catalysts for the etherification of glycerol. LDH precursors and catalysts were characterized by XRD, XPS, CO2-TPD, NH3-TPD, N2 adsorption and DTA-TG analysis. The MgFe mixed oxides exhibit excellent textural properties, with specific surface areas close to 200 m2 g-1 and average pore diameters in the mesoporous range. This family of catalysts has shown to be active in the formation of polyglycerols from glycerol without solvent, at 220 C, in a batch reactor. The highest conversion (41%) is found for the MgFeO4 catalyst prepared with a Mg/Fe molar ratio of 4, whereas full selectivity to diglycerols is only reached for the MgFeO1 catalyst. Only diglycerols (DGs) and triglycerols (TGs) have been detected after 24 h of reaction.

Diglycerol (DG) and triglycerol (TG) were synthesized via dehydrative etherification reaction of glycerol without solvent. The catalytic activities of alkali metal-acetate salts (LiOAc, NaOAc, and KOAc) for the etherification reaction of glycerol were investigated. Compared to the stronger basic catalysts, the less basic catalysts showed higher selectivity of DG and TG. A half mol % of LiOAc exhibited excellent selectivities of DG and TG as 52.5 and 30.4%, at 260 °C and 6 h. The dependence of reaction on the relative basicity and loading amount of catalyst, reaction time, and reaction temperature were investigated to elucidate the characteristics of etherification reaction of glycerol.

The catalytic etherification of glycerol using calcium-lanthanum oxide supported on MCM-41 as a stable heterogeneous basic catalyst was investigated. Stable heterogeneous mesoporous basic catalysts were synthesized by wet impregnation of MCM-41 with calcium nitrate and lanthanum nitrate. The surface and structural properties of the prepared catalysts were when characterized using different techniques. MCM-41 and modified MCM-41 were used in the solventless etherification of glycerol to produce diglycerol as the desired product. The reaction was performed at 250 °C for 8 h, and catalyst activity was evaluated. Catalytic etherification over the 20%Ca1.6La 0.6/MCM-41 catalyst resulted in the highest glycerol conversion of 91% at the diglycerol yield of 43%. The distribution of diglycerol isomer in the etherification of glycerol was studied, and the value of the sum of two dimers (ββ′ + αβ = 67%) was found to be higher than that of αα′ dimer (33%) after 8 h of reaction. Thus, the major reaction occurred inside the porous area instead of the external surface area.

MgAl mixed oxide from hydrotalcite was modified with niobium and evaluated as a catalyst for a liquid-phase glycerol conversion in the presence of hydrogen peroxide. Niobium oxide exhibited high activity for glycerol conversion via heterogeneous catalysis at 250 C. Gas chromatography with mass spectrometry (GC-MS) analysis of the reaction showed that diglycerol, ethers and ketone were the main products. The results strongly suggest that the glycerol conversion involves acid groups and oxidizing species generated upon reacting with H 2O2 and niobium. Furthermore, catalytic tests monitored by electrospray mass spectrometry (ESI-MS) suggest that ethers, such as di, tri and tetra glycerols, are formed during the glycerol condensation (m/z = 167, 223, 241, and 315). Preliminary tests using the reaction products as additives for gasoline demonstrate that the octane is increased due to the presence of ether formed from glycerol conversion.

In the present work, amorphous niobium oxides with 5% (w/w) vanadium or molybdenum isomorphically substituted into the material structure were synthesized. The materials were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDS), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The results show that vanadium and molybdenum were incorporated into the niobium oxide structure with concomitant changes in the morphologic and catalytic properties. Catalytic studies on the conversion of residual glycerin generated during biodiesel production in the presence of H2O2 showed enhanced efficiency of ether formation with the vanadium-containing material. The NbV/ethanol/glycerin/250 °C system was found to convert 80% of glycerin. Experiment-planning studies in conjunction with the analysis of the surface response via gas chromatography-mass spectrometry (GC-MS) aided in the determination of the optimal conditions. The catalytic tests monitored by GC-MS showed the formation a mixture of ethers obtained by the condensation of glycerol. Furthermore, it was observed that the modification of the catalyst directs the formation of larger molecules such as ketone mainly in the catalyst containing vanadium.

The present invention relates to a process for accelerated preparation of polyglycerol from crude glycerol using microwave irradiation as the heat element in the presence of soap as the catalyst. The process includes the steps of (a) heating the crude glycerol that contain soap to an elevated temperature for a certain reaction time by using a microwave technology, (b) acidifying the crude polyglycerol with mineral acid at a specific temperature and centrifuging acidified crude product obtained from step (b) at a specific temperature for a certain duration of time.

A polyglycerol composition contains diglycerol, triglycerol, and tetraglycerol each in a content of 5 percent by weight or more, has a total content of diglycerol, triglycerol, and tetraglycerol of 75 percent by weight or more, has a total content of higher polyglycerol components of 10 percent by weight or less, the higher polyglycerol components each having a degree of polymerization of 7 or higher, and is substantially free from chlorine atom. A process prepares a polyglycerol composition by reacting glycerol and/or a polyglycerol with glycidol in the presence of an activated carbon catalyst.

Bromination of glycerol by 48percent hydrobromic acid in the presence of an acid ion exchange resin (C264 or A19) led to the formation of a mixture of 1,3- and 2,3-dibromohydrins in a yield of around 70percent.The side products were essentially brominated polyglycerols.