Joël Barrault

Rational design of solid catalysts for the selective use of glycerol as a natural organic building block.

Glycerol is the main co-product of the vegetable oils industry (especially biodiesel). With the rapid development of oleochemistry, the production of glycerol is rapidly increasing and chemists are trying to find new applications of glycerol to encourage a better industrial development of vegetable oils. In this Review, attention is focused on the selective use of glycerol as a safe organic building block for organic chemistry. An overview is given of the different heterogeneous catalytic routes developed by chemists for the successful and environmentally friendly use of glycerol in sustainable organic chemistry. In particular, the effects of different catalyst structural parameters are discussed to clearly highlight how catalysis can help organic chemists to overcome the drawbacks stemming from the use of glycerol as a safe organic building block. It is shown that heterogeneous catalysis offers efficient routes for bypassing the traditional use of highly toxic and expensive epichlorohydrin, 3-chloro-1,2-propanediol, or glycidol, which are usually used as a glyceryl donor in organic chemistry.

Selective etherification of glycerol to polyglycerols over impregnated basic MCM-41 type mesoporous catalysts

Abstract In the general context of the development of the use of agricultural products for non-food applications, and particularly in the field of the glycerol valorisation (co-product of the triglycerides hydrolysis or methanolysis process), the selective etherification of glycerol was studied. The objective of this work is the direct and selective synthesis, from glycerol and without solvent, of polyglycerols having a low polymerisation degree (di- and/or triglycerol), in the presence of solid mesoporous catalysts. The main part of this study consists in the synthesis and the impregnation of mesoporous solids with different basic elements in order to make them active, selective and stable for the target reaction. The catalytic results obtained show that this impregnation method gives important activity, which must be correlated to an important active species incorporation. Concerning the selectivity of the modified mesoporous catalysts, the best value to (di-+tri-) glycerol are obtained over solids prepared by caesium impregnation. The re-use of these caesium impregnated catalysts does not affect the selectivity to the (di-+tri-) glycerol fraction. In the presence of lanthanum or magnesium containing catalysts, the glycerol dehydration to acrolein is very significant whereas this unwanted product is not formed when caesium is used as impregnation promoter.

Catalytic wet peroxide oxidation (CWPO) of phenol over mixed (AlCu)-pillared clays

Abstract New mixed (Al Cu)-pillared clays are prepared from a crude bentonite sample (H) (Tunisia deposit) by two discrete procedures: (a) a classical ‘D’ method by which Al or (Al, Cu) nitrate solutions, hydrolyzed with NaOH, are added to a 2% clay suspension and (b) a ‘P’ method where the clay powder is directly dispersed in the pillaring solution. Intercalation reactions are performed at 40°C, with an OH/(Al, Cu) molar ratio equal to 1.5 or 2 and an initial atomic percentage of copper (100 Cu/Al + Cu) of 0, 5 or 10%. Chemical analyses, XRD spectra and surface properties show that clays are intercalated after calcination at 300°C from both preparation procedures. There is increase of the Al content, d 001 and of the BET surface area, the copper content remains quite low whatever the conditions of preparation. Nevertheless, it seems that the copper content resulting from the ‘P’ method is higher. During phenol oxidation with hydrogen peroxide (CWPO reaction), the copper content and the procedure of preparation significantly influence the catalytic activity. Moreover, the very low copper solubilization proves that copper is certainly associated with alumina at the surface of the catalyst in mixed species intercalated or/and dispersed on the clay surface.

Heterogeneously catalyzed etherification of glycerol: new pathways for transformation of glycerol to more valuable chemicals

Direct etherification of glycerol with alkyl alcohols, olefins and dibenzyl ethers was successfully catalyzed by acid functionalized silica, allowing the first catalytic access to valuable monoalkyl glyceryl ethers.

Glycerol transesterification with methyl stearate over solid basic catalysts: I. Relationship between activity and basicity

Abstract The preparation of monoglycerides from fatty acids or fatty methyl esters and glycerol can be carried out in the presence of acid or basic catalysts. The use of solid basic catalysts could limit secondary reactions leading to product degradation. A comparison of several basic solids (MgO, CeO2, La2O3 and ZnO) has shown that the more significant the intrinsic basicity is, the more active the catalyst is. In order to increase the performance of these solids, several methods have been used for the preparation of MgO and CeO2. MgO prepared by hydration followed by calcination of a commercial raw material is the most active catalyst.

Catalytic wet peroxide oxidation of phenol over Al-Cu or Al-Fe modified clays

Al–Fe or Al–Cu modified clays were prepared from two natural montmorillonites and employed in the phenol oxidation with hydrogen peroxide in water. The samples were efficient in phenol elimination under mild experimental conditions (atmospheric pressure, 293 K and small quantities of hydrogen peroxide) without considerable leaching of the metal ions. The clays modified with Fe achieved high conversions of phenol and TOC thus showing to be very selective towards the formation of CO2 and H2O.

Effects of manganese oxide and sulphate on olefin selectivity of iron supported catalysts in the Fischer-Tropsch reaction

Abstract In agreement with previous studies, the addition of manganese compounds to iron or cobalt catalysts yields reproducible changes of catalytic properties. When iron catalysts were prepared from salt precursors, we generally observed a decrease of activity and an increase in light olefins selectivity, a maximum value being obtained for a Co (Fe)/Mn ≅ 1.0 bulk composition. Moreover, when there are small quantities of sulphate salt in iron or iron-manganese supported catalysts, we observed significant changes in catalytic properties, especially when activation temperature or reaction conditions favoured H 2 S formation. In the latter case, the promoter effect of the manganese compound on olefin selectivity was less pronounced, or even entirely nullified.

Reaction of glycerol with fatty acids in the presence of ion-exchange resins. Preparation of monoglycerides

The preparation of monoglycerides from glycerol and fatty acids in the presence of ion-exchange resins is studied. A preliminary swelling in the glycerol inhibits the reaction, whereas a swelling of the resin in the oleic acid, before the reaction, increases the activity and the selectivity. This result shows that the competitive adsorption of glycerol and fatty acid influences greatly the esterification rate. Generally, water is an inhibitor of the esterification reaction (catalyst poisoning and thermodynamic equilibrium) and different procedures have already been suggested for its elimination. By using a molecular sieve as a water trap, the oleic acid conversion increases up to 90% without any change of the monoglyceride selectivity (85%). Moreover, owing to the pore structure of the catalyst, it has to be expected that the hydrocarbon chain length of the fatty acid will influence the activity and the selectivity, evidence of which we give in the present study. Finally, if an excess of glycerol increases the selectivity of the monoglycerides, it decreases the activity and can be considered as a selective inhibitor.

Catalysis and fine chemistry

Triglycerides from vegetable oils are very important raw and renewable materials for the preparation of products useful for foods, pharmaceutics, cosmetics, From the methanolysis or hydrolysis of that glycerides, methyl esters or fatty acids and glycerol are obtained. Furthermore it is demonstrated in this paper that solid and basic materials may replace the usual homogeneous catalysts with the same activity and selectivity but without formation of by-products and wastes. Moreover, in the presence of mesoporous solids with an accurate pore size the glycerol is selectively transformed to linear di and triglycerol; and a yield of more than 80% is obtained.

Conversion of fructose and inulin to 5-hydroxymethylfurfural in sustainable betaine hydrochloride-based media

We show here that betaine hydrochloride (BHC), a co-product of the carbohydrate industry, can be used for the design of cheap and safe media capable of promoting the dehydration of fructose and inulin to HMF. In particular, in these BHC-based media, HMF was obtained with up to 84% yield, thus offering a competitive route to the traditional imidazolium-based ionic liquids.