Data di Pubblicazione:
2014
Citazione:
HETEROGENEOUS CATALYSIS FOR THE SYNTHESIS OF BIOPRODUCTS / M. Mariani ; tutor: L. Santagostini ; co-tutor: N. Ravasio ; coordinator: D. Roberto. Università degli Studi di Milano, 2014 Dec 02. 27. ciclo, Anno Accademico 2014. [10.13130/mariani-matteo_phd2014-12-02].
Abstract:
Dottorato di Ricerca in Chimica Industriale (XXVII Ciclo)
Report finale
Dottorando: Dott. Matteo Mariani
Tutor: Dott.ssa Laura Santagostini
Co-Tutor: Dott. ssa Nicoletta Ravasio
Heterogeneous catalysis for the synthesis of bioproducts
Before the discovery of crude oil, in 19th century, society was dependent only on biomass to answer to its energy request.
Petroleum discovery provided a source of inexpensive material for energy production, that helped to industrialize the world and improved the standards of living.
Unfortunately petroleum sources are waning, due to the growing request especially from the emerging countries, like India, China and Brazil.
Moreover the crude oil usage creates very burdensome pollution problems, related to the emission of greenhouse gases.
One possible answer to this important challenge could be the exploitation of biomass resources to produce not only energy, but also chemicals and liquid fuels in a sustainable way. In fact biomass is a renewable feedstock, that can be also obtained from agricultural and forest wastes.
BIOLUBRICANTS
Lubricants cover a large part of the worldwide chemicals market, and their consumption is estimated to be around 40 million metric tonnes per year. Automotive and hydraulics are the largest group of sold and used lubricant in the world. Unfortunately about 50% of all sold lubricants are loss in environment, resulting in severe contamination of soil, groundwater and air [1].
As a result, there has been an increasing demand of biolubricants, derived from vegetable oils. This kind of materials are biodegradable, and permit to limit the environmental pollution [2].
Vegetable oils have technical properties suitable for their use in lubricants formulation, but one significant problem is their low thermal stability, that depends on the presence of H atoms located in the beta position of ester groups, thus making the glycerol esters susceptible to elimination reaction and subsequent degradation of the native molecule. That is why so called hindered esters, that is esters of fatty acids with alcohols without H atoms in beta position, are preferred for lubricants that have to withstand high temperature and pressures [3].
The synthesis of these esters is based on the esterification reaction between an acid, derived from vegetable oils, and a polyol, like trimethylolpropane (TMP) or pentaerithrol (PE). The reaction is usually carried out with a homogeneous acidic catalyst (e.g., p-toluenesulfonic acid, mineral acids) that requires neutralization and washing steps:. In order to make the reaction greener it would be better to use heterogeneous catalysis and to avoid in particular the use of huge amounts of water. Heterogeneous catalysts provide simpler and cheaper separation processes, reduced wastes production, in this case inorganic salts, and in some cases can be recycled.
Scheme 1: Esterification reaction between TMP and a carboxylic acid
I tested in the esterification of fatty acids with polyols a series of amorphous mixed oxides, namely Silica zirconia silica alumina and silica titania, with surface area ranging from 300 to 500 m2/g and porosity in the range of mesoporousity. Results are summed up in Table 1
Polyol Fatty Acid Cat (%) Exp. Cond. t (h) Conv (%)
TMP Nonanoic SiO2-ZrO2 (2,5%) 5% exc TMP 6 99
TMP Nonanoic SiO2-TiO2 (2,5%) 5% exc TMP 6 94
TMP Nonanoic SiO2-Al2O3 (2,5%) 5% exc TMP 6 94
TMP Caprilic SiO2-ZrO2 (2,5%) 5% exc TMP 6 98
TMP Caprilic SiO2-TiO2 (2,5%) 5% exc TMP 6 92
TMP Caprilic SiO2-Al2O3 (2,5%) 5% exc TMP 6 92
TMP Oleic SiO2-ZrO2 (2,5%) 5% exc TMP 6 98
TMP Oleic SiO2-TiO2 (2,5%) 5% exc TMP 6 95
TMP Oleic SiO2-Al2O3 (2,5%) 5% exc TMP 6 89
TMP Oleic SiO2-TiO2 (2,5%) stoichiometric 6 87
NPG Oleic SiO2-ZrO2
Tipologia IRIS:
Tesi di dottorato
Elenco autori:
M. Mariani
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