Cette présente étude se propose d’actualiser la problématique des relations entre religieux et politique (dans l’espace sénégambien), en s’appuyant sur le cas des relations entre prédicateurs (saltigi) sereer et acteurs politiques. L’objet à partir duquel nous nous proposons d’analyser ces interrelations est le xoy, littéralement « l’appel » en sereer-siin. Les xoy sont des réunions de prédiction convoquées dans les localités sereer-siin à l’approche ou (plus rarement encore) pendant la saison des pluies. Les prédictions tenues (localement) par les saltigi et autres voyants sont en principe censées porter sur des questions tournant essentiellement autour de l’hivernage : pluie, récoltes, tempêtes, invasions de criquets, maladies etc. Cette forte orientation des xoy autour des questions d’hivernage, tout comme leur caractère communautaire ou local, semblent en revanche trancher d’avec le caractère associatif, « extracommunautaire », médiatique et national d’une réunion en particulier, celle organisée depuis 1981 par l’ONG PRO.ME.TRA dans la localité de Fatick et plus exactement dans un Centre de Médecine traditionnelle nommé Malango. Dans ce xoy auquel assistent des représentants locaux ou nationaux de l’Etat, les prédictions sont notoirement axées sur les questions de succession au sommet de l’Etat sénégalais. Ainsi, par une démarche de recherche associant en permanence données empiriques et éléments de littérature, nous analysons le sens et les fondements de ces prédictions axées sur le politique. Nos données nous conduisent à envisager ces prédictions comme l’expression et la conséquence d’un clientélisme discret entre acteurs politiques et saltigi du xoy de Malango. / This study is aiming to update the problem of the relationships between religion and politics in Senegambia. It is not based on the already well documented case of the relations between marabouts and modern politicians, but on the relation between sereer preachers (saltigi) and politicians. This research is based on an analysis of the xoy, meaning “the call” in sereer-siin language. Xoy are prediction reunions convened before or (more rarely) during the rainy season in sereer-siin localities. Predictions provided (locally) by saltigi and other seers are supposed to be about wintering: rain, harvests, tempests, grasshopper invasions, diseases, etc. This strong focus of xoy toward wintering questions, just as their local or community aspect, seems however to sever with the associative, extracommunal, mediatical and national dimensions of a particular meeting held by the NGO PRO.ME.TRA since 1981, that take place in Fatick (west-central Senegal) and more exactly in a traditional medicine center named Malango. This xoy is attended by local and national government representatives and predictions are notoriously focused on succession issues at the top of the Senegalese state. Thus, through empirical data (from 31 interviews and observations of xoy Malango) and elements of literature, we analyze the meaning and the basis of these political predictions. Our data show that these predictions are the expression and the consequence of a discrete clientelism between politicians and saltigi of the Malango’s xoy.

[pt] Esta tese descreve a síntese de um óxido misto de Zn e Zr (ZnxZr1-xOy), mediante uma técnica ainda não reportada e a utilização deste material na síntese de acetona a partir de etanol. O objetivo foi desenhar um catalisador com propriedades óxido-redutoras e capacidade de se autorregenerar após cada ciclo. A zircônia monoclínica (m-ZrO2) é um óxido já usado em catálise devido às suas propriedades ácido-básicas, mas com fracas propriedades óxido-redutoras. Estas últimas poderiam ser promovidas mediante dopagem substitucional deste material. A inserção de pequeníssimas quantidades de Zn na rede da m-ZrO2, mostraram um incremento apreciável na sua redutibilidade. O material obtido foi caracterizado por diversas técnicas e testado na obtenção de acetona a partir de etanol. O resultado indicou que a dopagem permitiu a formação de vacâncias de oxigênio, as quais promoveram a mobilidade do oxigênio até a superfície e, com isso, aumentaram redutibilidade do material. A seletividade da reação de conversão de etanol teve como produto maioritário a acetona. Foi demostrado que a regeneração do catalisador se deve a espécies oxidantes provenientes da dissociação da água presente no médio reacional; esta dissociação ocorreu nas vacâncias superficiais. Assim, demonstrou-se que a técnica desenvolvida no presente estudo, além de simples, resultou efetiva na síntese do óxido misto de Zn e Zr, um catalisador de composição simples, capaz de conduzir os diferentes passos do mecanismo na síntese de acetona. Considera-se que esta é a primeira etapa na sua viabilização comercial. / [en] This thesis describes the synthesis process of a mixed oxide with Zn and Zr (ZnxZr1-xOy), through a not yet published technique, as well as the utilization of this material in the acetone synthesis from ethanol. The mean goal was to design a catalyst with enhanced oxy-reduction properties and capability for selfregeneration after each cycle. Monoclinic zirconia (m-ZrO2) is already used in catalysis due to its acidic-basic properties, although its oxy-reduction properties are negligible. The enhancement of the oxy-reduction properties can be reached by substitutional doping of this material with a lower oxidation state metal. The insertion of very small quantities of Zn in the m-ZrO2 lattice, showed a high increment of its reducibility. The mixed oxides obtained were characterized by several techniques and catalytically tested in the acetone synthesis from ethanol. The results showed that doping allows the formation of oxygen vacancies, which allow oxygen mobility and therefore, the enhancement of reducibility. The reaction selectivity had acetone as majority product. It was shown that water is also produced and that it is dissociated in the oxygen vacancies generating oxidant species. The catalysts regeneration occurs due to those oxidant species. Therefore, it was demonstrated that the technique developed in this study was easy and effective in the synthesis of the mixed oxide with Zn and Zr, a catalyst with simple composition able to conduct every step of the acetone synthesis. This is considered the first step in the commercial feasibility of this material.