CVD‐Made Spinels: Synthesis, Characterization and Applications for Clean Energy

To reduce emissions and protect environment from pollution caused by volatile organic compounds (VOCs) and CO, catalytic oxidation can be applied as an efficient and promising technique. This review provides a novel and facile strategy to synthesize spinel-type and non-spinel-type transition metal oxides (TMOs). Specifically, single (Co3O4, α-Fe2O3, Mn3O4, CuO, Cu2O and Cr2O3) and binary (Co3-xCuxO4, Co3-xMnxO4 and Co3-xFexO4) TMOs have been prepared using pulsed spray evaporation chemical vapor deposition approach (PSE-CVD). PSE-CVD offers several advantages over conventional methods, such as relatively low cost, simplicity and high throughput, which makes it a promising strategy. Moreover, the PSE delivery system allows using less stable precursors and permits improving the reproducibility of the film properties with tailored compositions. The above listed TMOs prepared by PSE-CVD were successfully tested as catalysts toward the complete oxidation of some real fuels such as CO, C2H2, C3H6, n-C4H8 and C2H6O as representatives of VOCs and industrial exhaust streams. The active TMOs explored in this review could be potential catalysts candidates in one of the research areas that are currently under scrutiny, as the battle for the future of energy and environment involves the generation and application of clean energy

Synthesis and catalytic application of functional transition metal oxides

Mountapmbeme Kouotou P. Synthesis and catalytic application of functional transition metal oxides. Bielefeld University: Bielefeld University; 2014.Carbon monoxide and volatile organic compounds (VOCs) are serious air pollutants that may give rise to deleterious health and environmental effects. Such compounds are commonly found in the atmosphere at ground level in all urban and industrial centers. Total catalytic combustion has been considered as an effective and viable approach in controlling environmental emission; however some problems such as the non-availability of catalysts with low cost, high activity and stability in prevailing conditions remain. Hence, this thesis aims at developing economic combustion catalysts such as transition metals oxides (TMOs), using an elaborated Pulsed Spray Evaporation Chemical Vapor Deposition (PSE-CVD) approach and improved understanding of their behavior. Catalysts based on TMOs were successfully synthesized by PSE-CVD. Comprehensive characterization techniques, e.g. X-ray diffraction (XRD), Raman spectroscopy, Fourier transformed infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Helium ion microscopy (HIM), Energy dispersive spectroscopy (EDS), X-Ray photoelectron spectroscopy (XPS) and Ultra-Violet Visible spectroscopy (UV-Vis) as well as temperature-programmed reduction/re-oxidation (TPR/TPO) techniques were used to characterize the obtained films. To assess their functionality, the catalytic performance of the prepared catalysts was investigated for the conversion of some representative volatile organic compounds which may be contained in exhaust stream of industrial processes. One important conclusion that can be drawn based on the results presented is that TMOs are active catalysts with real potential mainly in processes relevant to air pollution control. Aiming for eventual commercial applications of some very active TMOs catalysts, fundamental studies concerning various aspects of TMOs catalysis have been carried out throughout this thesis. The investigations have been performed using TMO-based catalysts deposited on supports, with grid mesh of stainless steel as the common used substrates. Five main types of TMO-based catalysts were prepared, including single oxides such as Co3O4, Mn3O4, α-Fe2O3, CuO and mixed oxides (Co-Fe oxides). Several reactions with direct relevance to air-pollution control were studied, i.e. oxidation of carbon monoxide (CO), propene (C3H6), n-butene (n-C4H8), dimethyl ether (C2H6O) and n-butanol (n-C4H8O) in the presence of argon and oxygen. The catalytic performance of the chosen oxides was compared to reference results from the literature. Different aspects of these reactions were studied: (i) the effect of solvent and deposition temperature on the catalyst morphology, (ii) the effect of the deposition condition (substrate temperature), the thermal properties, the morphology and the doping on the catalyst performance. In our preliminary results, we briefly describe the controlled synthesis of Co3O4 spinel using Co(acac)3 as precursor; in this investigation, special attention was focused on the role played by solvents, deposition temperature and pressure on the thin film growth and morphology. As application, the performance of the deposited Co3O4 samples was tested towards CO and C3H6 conversion (Publication 1). As interesting materials, α-Fe2O3, CuO and Mn3O4 were also prepared. Thin films of α-Fe2O3 were selectively synthesized, and the effect of the deposition temperature and lattice oxygen on the catalytic combustion of C3H6 and CO was studied (Publications 2 and 3). In the same logic, copper oxide was prepared and found to be catalytically active towards CO and C3H6 oxidation (Publication 4). Besides the activity, the thermal properties of the catalyst were investigated, and a detailed study of the synthesis of the catalytically active Mn3O4 spinel and its thermal stability were performed. The obtained Mn3O4 exhibited high thermal stability and good catalytic performance in the combustion of CO and C3H6 (Publication 5). Based on the results obtained with Co3O4 and α-Fe2O3, we have prepared a mixed oxide of cobalt and iron (Co-Fe-O). Cobalt ferrite with spinel structure has presented technologically interesting solid-solution phases. In fact the combination of Fe and Co at different ratios has improved the physico-chemical properties and the catalytic performance of the materials. It was noticed that the composition played a significant role concerning the film morphology, band gap energy and the redox properties with consequence for the catalytic behavior of the material. For example, just small amounts of cobalt in cobalt ferrite mixed oxides were sufficient to enhance the performance in the CO oxidation (Manuscript 1) and the deep oxidation of olefins (such as for n-butene and propene) and DME (Manuscript 2). In the framework of a cooperation project with Moroccan partners with the topic “Catalytic application of natural clay”, we have compared the catalytic performance of Moroccan natural clays with Co3O4 and α-Fe2O3 towards the conversion of n-butanol (Publication 6). Synthesis and Catalytic Application of Functional Transition Metal Oxide

Décentralisation fiscale et croissance des dépenses locales dans les collectivités territoriales décentralisées au Cameroun : cas de la ville de Douala

La mise en oeuvre de la décentralisation soulève l’épineux problème de la mobilisation des ressources pour le développement des collectivités locales. Le budget communal étant tributaire des recettes fiscales, il s’avère nécessaire que la fiscalité locale assure une bonne couverture des dépenses publiques communales. L’objectif de ce papier est de déterminer les contributions de la fiscalité propre, la fiscalité partagée, les subventions et l’emprunt à la croissance des dépenses des collectivités territoriales décentralisées de la ville de Douala. La méthode des moindres carrés ordinaires a permis d’estimer un modèle à effets individuels fixes à partir des données de panel de six collectivités territoriales décentralisées sur la période 2011-2015. Lorsque la fiscalité propre, la fiscalité partagée, les subventions et l’emprunt varient d’une unité, les dépenses locales varient de 104.65%, 163.69%, 13.65% et -76,75%, respectivement. The implementation of decentralization raises the problem of the mobilization of the resources for the development of the local communities. The local taxation has to cover the communal public expenditures. The purpose of this paper is to determine the contributions from the local taxation, the shared taxation, the subsidies and the local state bonds to the Douala City Council expenditures. The ordinary least squares method has been used to estimate an individual fixed effect model from the panel data of the six local government making up the Douala City Council over the period going from 2011-2015.When the local taxation, the shared taxation, the subsidies and the local state bonds vary from a unit, the local expenditures vary from 104.65%, 163.69%, 13.65% and -76.75%, respectively

ANALYSIS OF THE CONTRIBUTION OF THE PROFILE OF THE LEADER-OWNER TO THE FINANCIAL PERFORMANCE OF THE CAMEROON INDIVIDUAL ENTERPRISE

This study aims to verify the influence of the personal and managerial characteristics of the owner-manager on the financial performance of the individual company. We collected our data from a face-to-face questionnaire with 152 Cameroonian companies. Our analyzes show that all the companies selected are sole proprietorships from different sectors of activity. Moreover, the binary logistic regression tells us that: the manager's level of education has no effect on the residual result, however, his training on the activity, his experience, his ability to innovate, his ability to invest exert a significant and positive influence on the residual result indirectly on the financial performance of the individual company. Similarly, when the executive is more than 40 years old, he exercises a significant and positive influence on the result of his business and thus on the financial performance of the individual company

Le logiciel sage Saari à l’épicentre du système d’information des entreprises au Cameroun : une culture comptable perçue à travers le modèle de l’acceptation technologique

The objective of this paper was to verify whether the profile of the entity, the profile of the account preparer and the perceived profile of the wise Saari management software allow each, as far as he is concerned, the daily use of the wise Saari management in companies in Cameroon. The problem arises in that out of thirty companies observed in the field as a prelude to this study, we found that all of them (100%) have actually installed the wise Saari management software at home but only do not use enough of this for the production of information and the management of the entity. To meet the verification objective, we opted for the positivist posture, for the hypothetico-deductive reasoning, for the quantitative approach, for a non-probability sampling method. We therefore used data collected by questionnaire on a sample of 34 companies in Cameroon. At the end of the descriptive analysis, the chi-square test of independence and the binary logistic regression which are indeed tests that we have retained for data processing using the SPSS data analysis software, we retain that 52.9% of the companies studied are from the trade sector, 26.5% from the industrial sector and 20.6% from the service sector and that the more the management of the company is decentralized, the higher the level of education and As the experience of a company's account preparer grows, the more perceived the usefulness and ease of use of wise software, the more likely it is that the company will actually adopt wise Saari.     JEL Classification : M40, L86 Paper type : Empirical researchL’objectif de ce papier était de vérifier si le profil de l’entité, le profil du préparateur de comptes et le profil perçu du logiciel de gestion sage Saari permettent chacun en ce qui le concerne, l’usage quotidien de l’outil de gestion sage Saari  dans les entreprises au Cameroun. Le problème se pose en ceci que sur trente entreprises observées sur le terrain en prélude de cette étude, nous avons constaté qu’elles toutes (100%) ont réellement installé le logiciel de gestion sage Saari chez-elles, mais seulement ne se servent pas suffisamment de cela pour la production des informations et le pilotage de l’entité. Pour répondre à l’objectif de vérification, nous avons opté pour la posture positiviste, pour le raisonnement hypothético-déductif, pour l’approche quantitative, pour une méthode d’échantillonnage non probabiliste.  Nous avons de ce fait exploité des données recueillies par questionnaire sur un échantillon de 34 entreprises au Cameroun. Au sortir de l’analyse descriptive, du test d’indépendance de khi-deux et de la régression logistique binaire qui sont effectivement des tests que nous avons retenus pour le traitement des données au biais du logiciel d’analyse de données SPSS, on retient que 52,9% des entreprises étudiées sont du secteur de commerce, 26,5% du secteur industriel et 20,6% du secteur de service et que plus la gestion de l’entreprise est décentralisée, plus le niveau d’étude et d’expérience du préparateur de comptes de l’entreprise croît, plus l’utilité et la facilité d’usage du logiciel sage sont perçues, plus il y a des chances que l’entreprise adopte réellement sage Saari.         Classification JEL : M40, L86 Type de l’article : Recherche appliqué

REMOVAL OF INDIGO CARMINE DYE (IC) BY BATCH ADSORPTION METHOD ONTO DRIED COLA NUT SHELLS AND ITS ACTIVE CARBON FROM AQUEOUS MEDIUM

Natural cola nut shells and its active carbons were used to remove indigo carmine dye from aqueous solution using batch adsorption test. The effect of pH, contact time (t), adsorbent dose (m) and initial concentrations (Co) were investigated. The equilibrium adsorption data were analyzed by Langmuir, Freundlich, Tempkin and Dubin-Kaganer-Raduskushkevich classical isotherm models. This equilibrium data best fits with all the four isotherm models for cola nut shells. Langmuir and Freundlich equations correlated well with data obtained using activated carbon based H3PO4 while Freundlich and Tempkin best agreed with activated carbon based KOH. The kinetics of indigo carmine dye was discussed by pseudo-first order, pseudo-second order, Elovich and Intra-particle diffusion models. The pseudo-second order kinetic model equation fitted best to the data from all the three adsorbents. Elovich fitted best with data obtained using activated carbon based H3PO4 while intra-particle diffusion model for activated carbon based KOH. D-K-R shows that adsorption process was chemisorption for all the three adsorbents. Natural cola nut shells and activated carbon based KOH show higher adsorption capacities with indigo carmine compared to activated carbon based H3PO4. The results indicated that these shells and it active carbon can be used as an effective and low-cost adsorbent to remove indigo carmine from aqueous solution

ACCESSIBILITE DES FEMMES A LA PROPRIETE FONCIERE ET DEVELOPPEMENT AGRICOLE DE BAÏGOM (OUEST-CAMEROUN)

Context and Background:Women represent close to 51% of the Cameroonian population and they are more than 70% active in food and market gardening  activities (INS, 2010). To this end, they need land and  capital to carry out their activities in order to make agriculture profitable and ensure food security for their families. The rural women of Baigom, like those elsewhere, are fighting with all the means at their disposal to gain access to land and participate in the agricultural development of this village.Goal and objectives: This contribution makes it possible to analyze the socio-economic and cultural context which is largely unfavorable to women's access to land in Baigom. Women who are active in agricultural production activities are limited by the unavailability of land resources, which nevertheless constitute a no less negligible factor of production. This state of virtual exclusion of these leading actors in family farming is detrimental to the development of the agricultural economy.Methodology: To conduct this study, the methodology adopted focused on primary and secondary sources and field observations. As for the primary sources, socio-economic surveys were carried out with a target population made up of women producers in the village of Baïgom. Young girls are more like family labor in peasant agriculture. The socio-economic surveys reached 5% of women over the age of 15, in the end 150 questionnaires were collected in the five main districts of the village (Nkoupetgom, Nkou gahri, Chaanké, Mbayé, Njissen).The secondary data are the fruit of the literature review and the consultation of the archives. These archives are present in the decentralized services of the State of the specialized institutions which generate official statistics such as the National Institute of Statistics (INS). The webography was not, moreover, a source of acquisition of certain knowledge in terms of the gender approach to land issues in tropical Africa as a whole.Results:The main results indicate that women's access to land ownership is low, with only about 8% holding a land title. Furthermore, the juxtaposition of modern and customary rights complicates the marginalization of women's access to land, with a negative impact on agricultural production activities. In spite of these obstacles, solutions are envisaged by all the actors to involve women more in the management of rural land