Distribution of methanol and catalysts between biodiesel and glycerin phases

The Inhibiting Behavior of Glycerol on the Kinetics of Transesterification of Palm Oil

Glycerol, a by-product from transesterification, is well-known as one of the factors inhibiting the reaction. Previous works have mostly shown that the reaction rate slows to a near-steady state and eventually reaches chemical equilibrium. This work aimed to study the inhibiting behavior of glycerol on the transesterification of palm oil. Observation under an LCD digital microscopy showed that glycerol-coated droplets of catalyst-methanol dispersed in the triglyceride phase. This work proposes that glycerol inhibits transesterification by the following mechanism: Droplets of catalyst-methanol disperse into the triglyceride phase; the reaction takes place at an interphase called the reactive zone; methyl ester, the desired product, has low polarity and moves to the triglyceride phase, whereas glycerol, the non-desired product, is more highly polar and accumulates on the droplet surface of catalyst-methanol droplets, inhibiting triglyceride mass transfer and diluting the concentration of the catalyst-methanol. The triglyceride mass transfer coefficient and reaction rate constant were both investigated and expressed as the exponential function.

Kinetic study of free fatty acid esterification reaction catalyzed by recoverable and reusable hydrochloric acid

The catalytic performance and recoverability of several homogeneous acid catalysts (hydrochloric, sulfuric, and nitric acids) for the esterification of enzyme-hydrolyzed free fatty acid (FFA) and methanol were studied. Although all tested catalysts drove the reaction to a high yield, hydrochloric acid was the only catalyst that could be considerably recovered and reused. The kinetics of the esterification reaction catalyzed by hydrochloric acid was investigated under varying catalyst loading (0.1-1M), reaction temperature (303-343K), and methanol/FFA molar ratio (1:1-20:1). In addition, a pseudo-homogeneous kinetic model incorporating the above factors was developed. A good agreement (r(2)=0.98) between the experimental and calculated data was obtained, thus proving the reliability of the model. Furthermore, the reusability of hydrochloric acid in FFA esterification can be predicted by the developed model. The recoverable hydrochloric acid achieved high yields of FFA esterification within five times of reuse.

Glycerol extracting dealcoholization for the biodiesel separation process

By means of utilizing sunflower oil and Jatropha oil as raw oil respectively, the biodiesel transesterification production and the multi-stage extracting separation were carried out experimentally. Results indicate that dealcoholized crude glycerol can be utilized as the extracting agent to achieve effective separation of methanol from the methyl ester phase, and the glycerol content in the dealcoholized methyl esters is as low as 0.02 wt.%. For the biodiesel separation process utilizing glycerol extracting dealcoholization, its technical and equipment information were acquired through the rigorous process simulation in contrast to the traditional biodiesel distillation separation process, and results show that its energy consumption decrease about 35% in contrast to that of the distillation separation process. The glycerol extracting dealcoholization has sufficient feasibility and superiority for the biodiesel separation process.

From symmetric glycerol derivatives to dissymmetric chlorohydrins

The anticipated worldwide increase in biodiesel production will result in an accumulation of glycerol for which there are insufficient conventional uses. The surplus of this by-product has increased rapidly during the last decade, prompting a search for new glycerol applications. We describe here the synthesis of dissymmetric chlorohydrin esters from symmetric 1,3-dichloro-2-propyl esters obtained from glycerol. We studied the influence of two solvents: 1,4-dioxane and 1-butanol and two bases: sodium carbonate and 1-butylimidazole, on the synthesis of dissymmetric chlorohydrin esters. In addition, we studied the influence of other bases (potassium and lithium carbonates) in the reaction using 1,4-dioxane as the solvent. The highest yield was obtained using 1,4-dioxane and sodium carbonate.

Catalytic Conversion of Glycerol to Valuable Commodity Chemicals

The recent progress of research and development on the catalytic selective conversion of glycerol to valuable commodity chemicals is reviewed in this chapter. Glycerol is currently produced in large quantities during the biodiesel process and as such is an important and useful by-product. The reaction networks of the different processes such as selective oxidation, hydrogenation, dehydrogenation, hydrogenolysis, gasification, etc., are discussed as a function of the type of catalyst (supported noble or non-noble metal catalysts, porous oxides, micro- and mesoporous) and reaction conditions on the selectivity to desired products. In conclusion, the effective utilization of glycerol will be a key factor that can promote biodiesel commercialization and further development. As a biomass-derived chemical feedstock, its utilization is also part of the global challenge aiming at the production of marketable chemicals via the catalytic transformation of biosustainable resources employed as substitutes for fossil fuels and fine chemicals.

Kinetics of sunflower oil methanolysis at low temperatures

The kinetics of the sunflower oil methanolysis process was studied at lower temperatures (10-30 degrees C). The sigmoidal kinetics of the process was explained by the mass transfer controlled region in the initial heterogenous regime, followed by the chemical reaction controlled region in the pseudo-homogenous regime. A simple kinetic model, which did not require complex computation of the kinetic constants, was used for simulation of the TG conversion and the FAME formation in the latter regime: the fast irreversible second-order reaction was followed by the slow reversible second-order reaction close to the completion of the methanolysis reaction. The mass transfer was related to the drop size of the dispersed (methanol) phase, which reduced rapidly with the progress of the methanolysis reaction. This was attributed to the formation of the emulsifying agents stabilizing the emulsion of methanol drops into the oil.

Chemoselective catalytic conversion of glycerol as a biorenewable source to valuable commodity chemicals

New opportunities for the conversion of glycerol into value-added chemicals have emerged in recent years as a result of glycerol's unique structure, properties, bioavailability, and renewability. Glycerol is currently produced in large amounts during the transesterification of fatty acids into biodiesel and as such represents a useful by-product. This paper provides a comprehensive review and critical analysis on the different reaction pathways for catalytic conversion of glycerol into commodity chemicals, including selective oxidation, selective hydrogenolysis, selective dehydration, pyrolysis and gasification, steam reforming, thermal reduction into syngas, selective transesterification, selective etherification, oligomerization and polymerization, and conversion of glycerol into glycerol carbonate.