Catalysing sustainable fuel and chemical synthesis

Concerns over the economics of proven fossil fuel reserves, in concert with government and public acceptance of the anthropogenic origin of rising CO2 emissions and associated climate change from such combustible carbon, are driving academic and commercial research into new sustainable routes to fuel and chemicals. The quest for such sustainable resources to meet the demands of a rapidly rising global population represents one of this century’s grand challenges. Here, we discuss catalytic solutions to the clean synthesis of biodiesel, the most readily implemented and low cost, alternative source of transportation fuels, and oxygenated organic molecules for the manufacture of fine and speciality chemicals to meet future societal demands

Desalination site selection on North-African coasts

The North-African coasts are characterized by a severe hydric stress while the potable water demand keeps increasing; this situation implies inter alias the implementation of desalination equipment with judicious types and locations. Site selection for a desalination plant is a very challenging task as various aspects are affected such as technical criteria, costs, time schedule, environmental impacts as well as political-social-human factors. All parties are concerned, not only governments but also lenders, general public, investors, utilities. This presentation will focus on the sequential steps from data gathering till final decision making. The sites comparison will involve a large range of topics such as for example, potable water demand, seawater intakes and outfalls, subsoil conditions, fresh water and power availability, accessibility, seashore line protection, local labor and infrastructure, regulations, etc. This requires multidisciplinary teams to work together not only to cover all individual elements but also to tackle the interdependences between them. A key choice will be the selection of the desalination process type i.e. thermal processes (multistage flash, multieffect distillation), membrane process (reverse osmosis) or hybrid process (mix of thermal and membrane processes): this decision, among others, is linked to either existing power generation - grid or power demand as well as to the raw water quality. While site selection decision making is an issue, one should not overlook the importance of the plant overall layout. As an illustration of the above considerations, several North-African coast sites are reviewed

Bismuth-promoted palladium catalysts for the selective oxidation of glyoxal into glyoxalic acid

The incorporation of bismuth in carbon-supported Pd-based catalysts is shown to increase significantly the catalytic activity in the selective oxidation of glyoxal into glyoxalic acid. Main side products are glycolic acid resulting from Cannizzaro dismutation and oxalic acid, generated by further oxidation of glyoxalic acid. Catalysts characterized by different Bi/Pd ratios (with Pd + Bi = 10 wt.%) were prepared according to various experimental procedures from two kinds of precursors, containing either inorganic (chloride, nitrate) or organic (acetate) ligands. The fresh and used catalysts were characterized by X-ray diffractometry and X-ray photoelectron spectroscopy. When comparing the time dependence of the performances of catalysts having the same overall composition (Bi/Pd = 0.5), bimetallic catalysts prepared from inorganic ligands or from acetate precursors exhibit comparable activities, while the selectivity towards glyoxalic acid remains higher for the acetate-type catalysts. In addition, the catalytic performances of Pd-Bi/C catalysts were found to be dependent upon the catalyst composition, those characterized by molar ratios Bi/Pd between 0.5 and 1.0 representing the most adequate compromise between high activity and high selectivity. Complementary experiments were also conducted on the second step of the oxidation scheme, i.e. oxidation of glyoxalic acid to oxalic acid. The behavior of the bimetallic Pd-Bi catalysts is also compared to that of a commercial trimetallic PdPtBi/C catalyst. (C) 2001 Elsevier Science B.V. All rights reserved

Mechanistic and kinetic studies on glyoxal oxidation with Bi- and Pb-promoted Pd/C catalysts

Bimetallic Pd-M/C catalysts (M = Bi, Pb) for the selective oxidation of glyoxal into glyoxalic acid were prepared either from inorganic salts or from acetate-type precursors. The bimetallic catalysts were found to be very active, confirming the promoting ability of both bismuth and lead in this reaction. The magnitude of their effect in terms of activity and selectivity was similar, and dependent on the preparation method and on the composition (optimum for ratios Pd:M = 1). The heavy elements could play their promoter role when introduced in solution in combination with a monometallic Pd/C catalyst. A kinetic treatment of the complex reaction scheme was carried out, and the rate constants for each step were determined. This showed that the reaction proceeds through a real heterogeneous mechanism involving the catalyst for the oxidation of glyoxal into glyoxalic acid and then, in a second step, into oxalic acid. The direct formation of oxalic acid from glyoxal could be neglected, and the formation of glycolic acid was confirmed to depend only on the pH. The absence of deactivation with our catalysts was also demonstrated. Correlations between the rate constants and some surface characteristics of the promoted catalysts were evidenced. (C) 2004 Elsevier B.V. All rights reserved

Thermal and membrane processe economics: optimized selection for seawater desalination

While the fuel cost has increased in the past years, the desalinated water demand has also increased sharply, especially in the deserted areas. The challenge is to be able to meet such future demand, minimizing the water production costs. The desalination concepts have evolved, achieving substantial progress: desalination thermal process is moving from MSF to MED, hybrids involving both thermal and membrane process are more and more implemented. Reduction in cost and the improved economics of desalination plants are essential elements for the development of communities. Energy, capital, and operating costs are key issues of water desalination economics. This will lead to an optimized process selection on a case by case approach: the choice will depend on the specific conditions prevailing on site, such as existing facilities, power and water demand increase, land availability, raw water quality, quality of water to be produced, ratio between power and water production, ratio between thermal and membrane desalination. The presentation will focus on these various aspects of seawater desalination economics