Cellulose, a biopolymer composed of glucose units, is an abundant and renewable resource. Its selective depolymerisation into building blocks is difficult due to its strong resistance to chemical reactions ascribed to its semi-crystalline structure. The aim of the thesis is to study the transformation of cellulose by heterogeneous catalysis. It has been shown that a partial cellulose depolymerisation in aqueous media was promoted by the hydroxonium ions generated in situ by water autoprotolysis at 190°C. The presence of a solid BrØnsted acid in the reaction media neither improved the cellulose conversion nor led to a particular selectivity into a valuable product. By contrast, solid Lewis acids were capable of significantly improving the cellulose conversion but also of favoring the formation of lactic acid in high yield. It is proposed that the solid Lewis sites intervene via coordination of oligosaccharides, issued from cellulose depolymerisation initiated by hydroxonium ions from water. The addition of a metallic phase such as Pt° on a solid Lewis acid support has also led to remarkable performances in term of extent of cellulose conversion and selectivity towards acetol and propylene glycol. The metallic bi-functionnal catalyst, under hydrogen atmosphere, not only leads to hydrogenated products but could also intervene into hydrides transfer elementary steps. An efficient cellulose conversion is the result of a combined action of hydroxonium ions provided by the hot water media with active sites of the bifunctionnal heterogeneous catalysts.
