The project undertook a systematic study of chlorination of titanium oxycarbide and oxycarbonitride with the aim to develop further understanding of kinetics and mechanisms of the chlorination reactions. The project studied titania, ilmenite ores, and synthetic rutile reduced by carbon in argon and nitrogen and chlorinated at different temperatures, gas flow rates and compositions. Chlorination of titanium suboxides, iron and impurities in ilmenite was also examined. Chlorination of titanium oxycarbide Ti(O,C) or oxycarbonitride Ti(O,C,N) can be implemented at 200 to 400 deg.C, while the commercial chlorination process in the production of titanium metal or titania pigment requires 800 to 1100 deg.C. This makes chlorination of Ti(O,C) or Ti(O,C,N) an attractive technology in processing of titanium minerals. Chlorination reaction is strongly exothermal, which increased the sample temperature up to 200 deg.C above the furnace temperature. The chlorination of Ti(O,C) or Ti(O,C,N) was ignited at 150 deg.C to 200 deg.C depending on the sample composition. Their chlorination at 235 deg.C to 400 deg.C was close to completion in less than 30 min. The chlorination rate of titanium oxycarbide or oxycarbonitride increased with increasing gas flow rate. Sample composition had a significant effect on the extent of chlorination. The optimum results were obtained for titanium oxycarbide or oxycarbonitride produced with carbon to titania molar ratio of 2.5; these samples contained no detectable excess of carbon or unreduced titanium suboxides. In chlorination of reduced ilmenite ores and synthetic rutile, Ti(O,C) or Ti(O,C,N), metallic iron and Ti2O3 were chlorinated. The rate and extent of chlorination of titanium increased with increasing carbon to TiO2 ratio. Chlorination of Ti2O3 was slow relative to Ti(O,C) or Ti(O,C,N) and iron; chlorination of impurity oxides such as MgO, SiO2 and Al2O3 was not observed. The project also examined chlorination of Ti(O,C) or Ti(O,C,N) in ilmenite ore and synthetic rutile after removal of iron, which was achieved by aerated leaching of reduced samples in heated flask containing 0.37 M of ammonium chloride solution. Iron removal from the ilmenite ore or synthetic rutile resulted in higher rate and extent of chlorination of titanium oxycarbide or oxycarbonitride.

The project undertook a systematic study of chlorination of titanium oxycarbide and oxycarbonitride with the aim to develop further understanding of kinetics and mechanisms of the chlorination reactions. The project studied titania, ilmenite ores, and synthetic rutile reduced by carbon in argon and nitrogen and chlorinated at different temperatures, gas flow rates and compositions. Chlorination of titanium suboxides, iron and impurities in ilmenite was also examined. Chlorination of titanium oxycarbide Ti(O,C) or oxycarbonitride Ti(O,C,N) can be implemented at 200 to 400 deg.C, while the commercial chlorination process in the production of titanium metal or titania pigment requires 800 to 1100 deg.C. This makes chlorination of Ti(O,C) or Ti(O,C,N) an attractive technology in processing of titanium minerals. Chlorination reaction is strongly exothermal, which increased the sample temperature up to 200 deg.C above the furnace temperature. The chlorination of Ti(O,C) or Ti(O,C,N) was ignited at 150 deg.C to 200 deg.C depending on the sample composition. Their chlorination at 235 deg.C to 400 deg.C was close to completion in less than 30 min. The chlorination rate of titanium oxycarbide or oxycarbonitride increased with increasing gas flow rate. Sample composition had a significant effect on the extent of chlorination. The optimum results were obtained for titanium oxycarbide or oxycarbonitride produced with carbon to titania molar ratio of 2.5; these samples contained no detectable excess of carbon or unreduced titanium suboxides. In chlorination of reduced ilmenite ores and synthetic rutile, Ti(O,C) or Ti(O,C,N), metallic iron and Ti2O3 were chlorinated. The rate and extent of chlorination of titanium increased with increasing carbon to TiO2 ratio. Chlorination of Ti2O3 was slow relative to Ti(O,C) or Ti(O,C,N) and iron; chlorination of impurity oxides such as MgO, SiO2 and Al2O3 was not observed. The project also examined chlorination of Ti(O,C) or Ti(O,C,N) in ilmenite ore and synthetic rutile after removal of iron, which was achieved by aerated leaching of reduced samples in heated flask containing 0.37 M of ammonium chloride solution. Iron removal from the ilmenite ore or synthetic rutile resulted in higher rate and extent of chlorination of titanium oxycarbide or oxycarbonitride.

Made available in DSpace on 2014-12-17T14:58:13Z (GMT). No. of bitstreams: 1 RaquelGC_DISSERT.pdf: 1617455 bytes, checksum: fe137c67d61e0483bac922261c815e1e (MD5) Previous issue date: 2011-11-23 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / In this study we used the plasma as a source of energy in the process of carbothermic reduction of rutile ore (TiO2). The rutile and graphite powders were milled for 15 h and placed in a hollow cathode discharge produced by in order to obtain titanium carbonitride directly from the reaction, was verified the influence of processing parameters of plasma temperature and time in the synthesis of TiCN. The reaction was carried out at 600, 700 and 800˚C for 3 to 4 hours in an atmosphere of nitrogen and argon. During all reactions was monitored by plasma technique of optical emission spectroscopy (EEO) to check the active species present in the process of carbothermal reduction of TiO2. The powder obtained after the reactions were characterized by the techniques of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The technique of EEO were detected in all reactions the spectra CO and NO, and these gas-phase resulting from the reduction of TiO2. The results of X-ray diffraction confirmed the reduction, where for all conditions studied there was evidence of early reduction of TiO2 through the emergence of intermediate oxides. In the samples reduced at 600 and 700˚C, there was only the phase Ti6O11, those reduced to 800˚C appeared Ti5O9 phases, and Ti6O11 Ti7O13, confirming that the carbothermal reduction in plasma, a reduction of the ore rutile (TiO2) in a series of intermediate titanium oxide (TinO2n-1) where n varies between 5 and 10 / Neste trabalho foi utilizado o plasma como fonte energ?tica no processo de redu??o carbot?rmica do min?rio rutilo (TiO2). Os p?s de rutilo e grafite foram mo?dos durante 15 h e introduzidos numa descarga produzida por c?todo oco a fim de obter carbonitreto de tit?nio diretamente da rea??o, sendo verificado a influ?ncia dos par?metros de processamento de plasma, temperatura e tempo na s?ntese de TiCN. As rea??o foram efetuadas a 600, 700 e 800˚C por 3 e 4 horas numa atmosfera de nitrog?nio e arg?nio. Durante todas as rea??es o plasma foi monitorado pela t?cnica de espectroscopia de emiss?o ?ptica (EEO) para verificar as esp?cies ativas presente no processo de redu??o carbot?rmica de TiO2. Os p?s obtidos ap?s as rea??es foram caracterizados pelas t?cnicas de difra??o de raios X (DRX) e microscopia eletr?nica de varredura (MEV). Pela t?cnica de EEO foram detectados em todas as rea??es os espectros CO e NO, sendo essas fases gasosas resultante da redu??o do TiO2. Os resultados de difra??o de raios X confirmou essa redu??o, onde para todas as condi??es estudadas houve evid?ncia de in?cio da redu??o do TiO2 atrav?s do aparecimento de ?xidos intermedi?rios. Nas amostras reduzidas a 600 e 700˚C observou-se apenas a fase Ti6O11, naquelas reduzidas a 800 ˚C apareceram as fases Ti5O9, Ti6O11 e Ti7O13, comprovando que com a redu??o carbot?rmica em plasma, houve redu??o do min?rio rutilo (TiO2) em uma s?rie de ?xido intermedi?rios de tit?nio (TinO2n-1) onde n varia entre 5 e 10

Les procédés thermochimiques solaires étudiés concernent la conversion de charges hydrocarbonées solides ou gazeuses en syngas, ainsi que la réduction d’oxydes en métaux en utilisant l’énergie solaire concentrée pour effectuer les réactions endothermiques, permettant ainsi le stockage de l’énergie solaire intermittente en carburants sans émissions de CO2. Ce travail a pour objectif l’étude expérimentale de trois procédés solaires incluant la gazéification de biomasse, le reformage de méthane en boucle chimique, et la carboréduction de ZnO et MgO. La gazéification et le reformage permettent la valorisation de biomasse bois et de méthane en syngas, tandis que la carboréduction permet de produire Zn et Mg à partir de ZnO et MgO. Ces procédés ont été étudiés dans des réacteurs solaires de 1.5 kWth, en utilisant le rayonnement concentré fourni par des systèmes à concentration du laboratoire PROMES, Odeillo, France. L’impact des paramètres opératoires de chaque procédé sur les mécanismes réactionnels, conversion, rendement, et performances énergétiques a été évalué en détail. Ces procédés ont permis d’améliorer la conversion chimique, les rendements en syngas, les efficacités énergétiques tout en permettant un stockage de l’énergie solaire en combustibles transportables, avec des performances globales supérieures aux procédés conventionnels. De plus, leur faisabilité, fiabilité et robustesse pour la conversion de méthane et biomasse en syngas et la production de Mg et Zn en fonctionnement batch ou continu sous pression réduite ou atmosphérique en conditions solaires réelles ont été démontrés. / The investigated solar thermochemical processes consist of the thermochemical conversion of solid and gaseous carbonaceous feedstocks into syngas as well as metal oxides reduction into metal commodities utilizing concentrated solar energy to drive endothermic chemical reactions, thereby enabling intermittent solar energy storage into solar fuels and avoiding CO2 emissions. This work aims to experimentally investigate three key solar thermochemical conversion approaches regarding biomass gasification, chemical looping reforming of methane, and carbothermal reduction of ZnO and MgO. Solar gasification and solar chemical looping reforming allowed valorizing wood biomass and methane into syngas, while solar carbothermal reduction was applied to produce Zn and Mg from ZnO and MgO. Such solar thermochemical processes were performed in 1.5 kWth prototype solar chemical reactors, utilizing highly concentrated sunlight provided by a solar concentrator at PROMES laboratory, Odeillo, France. The impact of controlling parameters of each process on the reaction mechanism, conversion, yields, and process performance, during on-sun testing was investigated and evaluated thoroughly. Such processes were proved to significantly improve the chemical conversion, syngas yields, energy efficiency, with solar energy storage into transportable fuels, thereby outperforming the conventional processes. Moreover, their feasibility, reliability, and robustness in converting both methane and biomass feedstocks to syngas as well as producing Mg and Zn metals in batch and continuous operation under vacuum and atmospheric conditions during on-sun operation were successfully demonstrated.

A tutorial review on cellular as well as nanoporous carbides covering their structure, synthesis and potential applications. Especially new carbide materials with a hierarchical pore structure are in focus. As a central theme silicon carbide based materials are picked out, but also titanium, tungsten and boron carbides, as well as carbide-derived carbons, are part of this review. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

A tutorial review on cellular as well as nanoporous carbides covering their structure, synthesis and potential applications. Especially new carbide materials with a hierarchical pore structure are in focus. As a central theme silicon carbide based materials are picked out, but also titanium, tungsten and boron carbides, as well as carbide-derived carbons, are part of this review. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Nano-scaled carbons were produced by thermal treatment of pine wood chips and bio-char. The influence of temperature, heating rate, pyrolysis time, and type and flow rate of purge gas on the production of nano-carbons was investigated. Using TEM and SEM, different carbon-based nanomaterials were observed in the prepared samples. The effect of metal ion doping on the bio-char was also investigated. Highly functionalized nano carbonaceous materials were synthesized by low temperature hydrothermal carbonization (HTC) using glucose, sucrose, xylose, and cellulose. Carbon-encapsulated iron (Fe@C) core-shell particles were also synthesized by the HTC method and used as catalyst for Fischer-Tropsch synthesis to produce liquid hydrocarbons from syngas; it showed excellent activity. Nano-structured Co-Mo carbides over several nano-sized carbon materials were prepared using the carbothermal reduction and carbothermal hydrogen reduction methods. Nano-structured Co-Mo carbides derived from Vulcan® XC-72 were used as the catalyst to produce higher alcohols.