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No / In this paper, a model of catalytic naphtha reforming process of commercial catalytic reforming unit of Kaduna Refining & Petrochemical Company (KRPC) is adopted and simulated using the gPROMS software, an equation-oriented modelling software. The kinetic and thermodynamic parameters and properties were obtained from literature. The model was used to monitor the behaviour of the temperature and concentrations of parafins, naphthenes and aromatics with respect to the changing heights of the reactors. A comprehensive sensitivity analysis of the product quality (Aromatics) and product yield, reformate, lighter gases and hydrogen yields is performed by varying the operating conditions of the reaction and the following conclusions were made. It was found that the production of aromatics, hydrogen yield, lighter gases and coke on catalyst increase with increasing temperature of the reaction while the reformate yield decreases with the increasing temperature and vice versa. The aromatics, hydrogen yield, coke on catalyst and lighter gases decrease with increasing pressure while the reformate yield decreases with decreasing pressure and vice versa. Hydrogen-hydrocarbon ratio (HHR) affects the product quality slightly by increasing the reformate and hydrogen yield and decreasing the aromatics slightly as well decreasing the coke on catalyst.

As biomass and municipal solid wastes become increasingly viable fossil fuels alternatives, more researches are being conducted to improve on the processes for their conversion to energy or energy carriers. Gasification is one of such processes and it forms the core of this project. This project presents a specified design of a small-scale fixed-bed reactor for the purpose of investigating the gasification processes of biomass and municipal solid wastes. Gas extraction ports are evenly distributed along the height of the reactor to extract product gases and accommodate thermo-couples for temperature measurement. A cyclone separator was incorporated to clean the gases as well as extract bio-oil from the gases. / Program: Masterutbildning i energi- och material

This dissertation explores catalyst technology for the production of renewable liquid fuels via thermo-chemical conversion of biomass derived syngas. Fischer-Tropsch synthesis is a process for converting syngas, i.e. a mixture of CO and H2, into energy rich long chain hydrocarbons and oxygenated compounds. This synthesis process involves a number of elementary reactions leading to an array of polymeric products. The economic operation of an FTS process lie in the interplay of both catalyst and reactor design. In relation to catalysis, the nature of chemisorbed species, and the fractional availability of active metal sites determines rate, conversion and yield. Similarly, reactor design decides the operational envelope and determines the economics of an FTS process. Eggshell cobalt catalysts are used in CO hydrogenation reactions due to their ability to maximize the use of precious cobalt metal. The thickness of the shell can be utilized to control the product yield and distribution. In this study, during catalyst synthesis stage, metal-support interaction has been exploited to control the thickness and hence, the product distribution. The catalysts are prepared using precipitation of cobalt nitrate (dissolved in ethanol) on silica support. The metal deposition rate and the location are controlled through optimized non-polar solvent imbibing, followed by water addition to a Co(NO3)2-ethanol solution and hydrolysis by urea. The eggshell coating thickness (in the absence of restricting solvent) onto silica gel substrate was modeled via theoretical equations and experimentally verified during catalyst preparation through microscopic analysis of catalyst samples. Bulk precursor solution properties such as viscosity and surface tension along with substrate properties such as tortuosity are analyzed and included in the theoretical analysis for tailoring the catalyst eggshell thickness. Polar and non-polar solvent interactions with silica gel are exploited during cobalt precipitation to control the eggshell thickness. The catalyst samples were characterized using hydrogen chemisorption studies. The catalyst was tested in a fixed bed tubular bench scale reactor using research grade synthetic feed gases (H2:CO being 2:1). Products were analyzed in a GC column fitted with flame ionized detector and the results were compared with Anderson-Schulz-Flory distribution. Liquid product analysis validated the approach used for eggshell catalyst design and synthesis. The impact of solvent and calcination conditions, on the performance of eggshell catalysts was examined. Solvents such as water and alcohol attach to the silanol groups on the silica gel surface and compete with metal salts during ion exchange and adsorption. The solution properties impact metal dispersion and interaction with metal support. The calcination conditions (static versus dynamic, oxidizing versus reducing atmosphere) also have an impact on metal dispersion and support interaction. Ethanol proved to be a better solvent for enhancing the dispersion due to its surface wetting properties. Direct reduction in dynamic hydrogen provided gradual decomposition of the cobalt precursor thus reducing agglomeration. Both the use of water as a solvent and a static air environment during calcination led to lower dispersion. The back reaction of calcination products (especially H2O) and agglomeration due to thermal expansion were competing phenomenon in a static oxidizing environment. Catalyst characterization revealed that the latter effect was pre-dominant. Catalyst performance testing was first done with pure gases (H2 & CO) in a fixed bed reactor. Additionally, to examine the technological feasibility and economic viability of producing liquid fuels from biomass via the thermo-chemical route, laboratory scale testing was done using syngas produced by gasification of pine chips. The pine chips were gasified in a tubular entrained flow gasifier operated at MSU and supplied in cylinders. The raw biomass syngas was treated using a series of adsorbents to remove tar, water and other impurities. This pre-treated gas was subjected to Fischer-Tropsch Synthesis (FTS) in a bench scale fixed bed reactor using the eggshell cobalt catalyst developed in our laboratory. Hydrogen was added to attain the 2:1 stoichiometric ratio required for the FTS reaction. The product gases were analyzed using an FTIR gas cell while liquid product was analyzed using a GC/MS HP-5 column. The eggshell catalyst produced fuel preferentially in the range of middle distillates. The activity of FTS catalyst under biomass derived syngas was lower when compared to that under pure surrogates (H2/CO) due to the presence of inert components (such as methane) in the biomass derived syngas To complement the experimental study, a comprehensive model of FTS catalytic process was developed. This included both catalyst and a fixed bed reactor model. While modeling a catalyst pellet, intra-particle diffusion limitation was taken into account. For a spherical 2mm pellet, eggshell morphology provided highest activity and selectivity. The reactor model was developed by coupling intra-pellet model with inter-pellet model via reaction term. The entire process operation starting with gas injection was considered. Presence of radial temperature profile, due to wall cooling, was confirmed by Mears criterion. Thus for a fixed time duration, a 2-dimensional reactor model, with respect to temperature and concentration, was developed. The safe operational envelopes for a fixed bed reactor, using cobalt catalyst, was narrow 473 < T < 493. The extent of catalyst pore fill changed (i) the radial thermal conductivity (ii) the overall temperature and concentration profile across the bed and (iii) the limits of safe operation without reaction runaway. Finally, hydrocarbon product selectivity also varied during startup. While the catalyst pores were being filled, effluent product mainly composed of lighter, more volatile components. Once the pores are filled, heavier products started to trickle down the bed. The economics of a large scale production of liquid fuels using this technology was explored using a CHEMCAD model of a large scale process for producing liquid fuel from biomass, a sensitivity study was conducted to determine key process parameters Two different gasification technologies were compared, one that uses only biomass (BTL process) and a second process that supplements the biomass feed with natural gas for meeting energy and hydrogen needs (BGTL process). The basis for the design was 2000 metric tons of dry biomass feed per hour. The breakeven price for synthetic crude oil was estimated at $106/bbl. for the BTL plant, and $88/bbl. for a natural gas assisted BGTL plant using current market prices for raw materials utilities and capital equipment. With the increasing availability, and falling prices of natural gas, the reforming of natural gas will provide a bridge solution in the short term for economical natural gas assisted BTL conversion, thus making it competitive in marketplace.

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Parmi les réacteurs de génération IV, le GFR et le VHTR utilisent l'hélium comme caloporteur. Il est nécessaire de contrôler sa qualité chimique. Outre des impuretés radiochimiques et particulaires, il peut contenir H2, CO, CH4, CO2, H2O, O2 et des composés azotés, et doit être purifié en permanence. Au CEA, un pilote permet d'étudier cette purification, réalisée en trois étapes: oxydation de H2 et CO sur CuO, puis deux étapes d'adsorption. L’objectif est de fournir une analyse détaillée des deux premières étapes, en les mettant en œuvre à l'échelle du laboratoire. On montre à l’aide d’une première modélisation que la consommation du lit de CuO est totale, et en régime chimique. Les particules de CuO sont constituées de grains d'environ 200 nm de diamètre. Un deuxième modèle, défini à l'échelle de ces grains, permet de trouver des résultats en accord avec les précédents. Un facteur d'échelle lié à la géométrie entre les constantes cinétiques issues des deux types de modélisation a été mis en évidence. Une compétition entre les réactions d'oxydation du CO et de H2 a été observée. Les énergies d'activation des ces réactions sont de l'ordre de 30 kJ.mol-1. La réaction CO/CuO est favorisée. La simulation numérique du déroulement simultané des deux réactions montre qu'il faut envisager une adsorption préférentielle de CO sur le CuO. Dans le cas de l'étape d'adsorption sur tamis moléculaire de CO2 et H2O, une méthodologie similaire a été mise en œuvre. Les isothermes expérimentales obtenues sont de type Langmuir. Les courbes de percée en sortie d'adsorbeur ont montré que le comportement global du lit était correctement représenté par le modèle retenu / In GEN IV studies on future fission nuclear reactors, two concepts using helium as a coolant have been selected: GFR and VHTR. Among radioactive impurities and dusts, helium can contain H2, CO, CH4, CO2, H2O, O2, as well as nitrogenous species. To optimize the reactor functioning and lifespan, it is necessary to control the coolant chemical composition using a dedicated purification system. A pilot designed at the CEA allows studying this purification system. Its design includes three unit operations: H2 and CO oxidation on CuO, then two adsorption steps. This study aims at providing a detailed analysis of the first and second purification steps, which have both been widely studied experimentally at laboratory scale. A first modelling based on a macroscopic approach was developed to represent the behaviour of the reactor and has shown that the CuO fixed bed conversion is dependent on the chemistry (mass transfer is not an issue) and is complete. The results of the structural analysis of the solids allow considering the CuO as particles made of 200 nm diameter grains. Hence, a new model at grain scale is proposed. It is highlighted that the kinetic constants from these two models are related with a scale factor which depends on geometry. A competition between carbon monoxide and hydrogen oxidation has been shown. Activation energies are around 30 kJ.mol-1. Simulation of the simultaneous oxidations leads to consider CO preferential adsorption. A similar methodology has been applied for CO2 and H2O adsorption. The experimental isotherms showed a Langmuir type adsorption. Using this model, experimental and theoretical results agree

La rápida industrialización y urbanización mundial ha creado un sin número de contaminantes para los medios acuosos tóxicos y peligrosos, los cuales en su gran mayoría son difícil de degradar de forma natural. Los fenoles son algunos de estos compuestos tóxicos que se encuentran con frecuencia en muchos efluentes industriales. Revisión literaria específica que la oxidación catalítica en aire húmedo utilizando carbón activado podría ser una solución prometedora para la destrucción de estos contaminantes fenólicos. Sin embargo, parece difícil lograr la estabilidad del catalizador dentro del reactor de lecho fijo, en estado estacionario, debido a la combustión lenta de carbón activado. Dentro de este contexto, el presente trabajo se centró en tres aspectos principales para extender los conocimientos actuales sobre la oxidación catalítica del aire húmedo, los cuales son: el establecimiento de las condiciones de arranque del reactor, el estudio de la cinética de reacción y la evaluación de la operación periódica de reactores de lecho fijo. Se ha demostrado que la cinética de la reacción puede llevarse a cabo en un reactor por goteo de lecho fijo sin limitaciones de transferencia de masa y calor. Y más importante aún, el catalizador pudo mantenerse estable durante la oxidación catalítica del aire húmedo de fenol sobre carbón activo en un reactor de lecho fijo, a través de la operación de un reactor dinámico mediante la optimización de los parámetros periódicos. / The fast world industrialization and urbanization creates a large number of water pollutants that are toxic and hazardous and in most cases too hard to amend naturally. Phenols are amongst those toxic compounds frequently found in many industrial effluents. A review of the specific literature points out that catalytic wet air oxidation using activated carbon can be a promising solution for the destruction of phenolic pollutants. However, it seems unlikely to achieve stable catalyst in fixed bed reactor under steady state operation due to the slow combustion of activated carbon. Within this context, the present work focus on three main aspects to extend the current state of art of catalytic wet air oxidation: establishing reactor start-up, kinetic measurements and periodic operation of fixed bed reactors. It has been shown that kinetic measurement can be conducted in trickle bed reactor without mass and heat transfer limitations. Most importantly, stable catalyst during catalytic wet air oxidation of phenol over active carbon was achieved in fixed bed reactor through dynamic reactor operation by optimizing periodic parameters.

A reaÃÃo de sÃntese de Fischer-Tropsch, que pode ser compreendida como uma polimerizaÃÃo entre os gases monÃxido de carbono e hidrogÃnio, mistura conhecida por gÃs de sÃntese, com a formaÃÃo de hidrocarbonetos parafÃnicos e olefÃnicos, ocorre na presenÃa de catalisadores heterogÃneos, onde aqueles de cobalto aparecem como os mais promissores quando se deseja produzir fraÃÃes de hidrocarbonetos comercialmente mais favorÃveis, como gasolina, diesel e graxas. A reaÃÃo jà à encarada como alternativa ao petrÃleo, pois o gÃs de sÃntese à gerado a partir de outras fontes, notadamente o gÃs natural. O conhecimento da reaÃÃo ainda à fundamentalmente experimental, e nÃo existem mecanismos especÃficos que expliquem com exatidÃo a formaÃÃo dos produtos e sua distribuiÃÃo ao longo de uma faixa de hidrocarbonetos. Esse trabalho realiza inicialmente uma estimaÃÃo de parÃmetros, enquadrados em uma modelagem cinÃtica, que procuram explicar o desenvolvimento da reaÃÃo e a formaÃÃo das parafinas e olefinas em reatores tubulares de leito fixo com catalisadores de cobalto. De posse dos parÃmetros, procurou-se um modelo matemÃtico mais adequado à operaÃÃo do reator tubular, com a utilizaÃÃo de equaÃÃes para a transferÃncia de massa e de calor. Essas simulaÃÃes foram submetidas posteriormente a uma anÃlise estatÃstica para a determinaÃÃo de variÃveis mais significativas para a reaÃÃo. / In this work, the reaction of the Fischer-Tropsch synthesis, which may be understood as a polymerization between the gases carbon monoxide and hydrogen, mixture known as synthesis gas, with the formation of paraffinic and olefinic hydrocarbons, occurs under heterogeneous catalysis, where those of cobalt appear as the most promising when you want to produce hydrocarbon fractions commercially more favorable, such as gasoline, diesel and waxes. The reaction is already perceived as an alternative to petroleum, since the synthesis gas is generated from other sources, notably natural gas. The knowledge of the reaction is still essentially experimental, and there are no specific mechanisms that explain precisely the formation of the products and their distribution over a range of hydrocarbons. This work performs initial parameter estimation, framed in a kinetic modeling, which seek to explain the development of the reaction and the formation of paraffins and olefins in tubular fixed bed reactors with cobalt catalyst. In possession of the parameters, we tried to one better suited to reality modeling of reactor operation, with the use of equations for mass transfer and heat. These simulations were later subjected to a statistical analysis to determine the most significant variables for the reaction.

This work begins with an introduction to catalysis focusing on heterogeneous systems and surface science phenomena. A study on the partial oxidation reaction of n-butane to maleic anhydride (MA) is presented in the first part. MA supplies are barely adequate for market requirements due to continued strong demand. Only slight improvement in catalytic performance would be welcome in the industrial community. The vanadium phosphorus oxide (VPO) catalyst was used in this work. The reaction is highly exothermic and the need to properly support the catalyst, not only for good dispersion but adequate heat dissipation is of crucial importance. For this, alpha-SiC commercial powders were used in synthesizing the catalyst due to its high thermal conductivity. Up to 25% MA yields were obtained and the reaction temperature was lowered by up to 28% using SiC/VPO mixed catalysts. The second part of this work is focused on the Fischer-Tropsch synthesis (FTS) process using cobalt silica supported catalysts. The main objective is the production of synthetic ultra high purity jet fuel (JP5). This is a very timely topic given the energy issues our world is facing. Almost all aspects of the FTS process have been extensively studied, however the effects of calcination temperature and silica support structure on the catalyst performance are lacking in literature. The catalysts were prepared using various silica supports. The catalysts had different drying and calcination temperatures. It was found that lower support surface area and calcination temperature catalysts exhibited higher activity due to lower support cobalt phase interaction. Co/silica catalysts calcined at 573K showed the highest CO conversion and the lowest CH4 selectivity. Catalysts prepared with 300m²/g support surface area exhibited 79.5% C5+ selectivity due to higher reducibility and less metal support interaction. The properties and performance of various prepared catalysts in both VPO and Co/silica systems are characterized by FTIR, XRD, BET, GC and XPS techniques. Theoretical FTS deactivation by sintering calculations and SiC/VPO particle temperature gradient calculations are presented as well. Finally, conclusions and future work on improving the yield and selectivity and scaling up the bench top setups are also presented.

A highly selective eggshell Fischer-Tropsch catalyst has been fabricated via interaction of hydrophobic and hydrophilic molecules on thermally treated silica gel. The physical interactions of the mesoporous silica support and the effect of catalyst preparation conditions on the performance of the cobalt/SiO2 were explored. It was found that dispersion and performance of the FT cobalt/SiO2 catalyst were significantly affected by the preparation technique used. In this study we focus on two key variables: the solvent used during the precursor loading and the calcination atmosphere. Silanol groups on the silica surface and near-surface regions can alter morphology and dispersion of the supported active metals. Solvents used for precursor such as water or alcohol attach to these silanol sites in specific configurations and compete with metal salts during ion exchange and adsorption. By fine tuning the solvent attachments on heat treated silica we have fabricated a cobalt/silica catalyst with high dispersion and low metal loads. Additionally, since silica has affinity for both polar and non-polar molecule depending on the surface conditions; this property has been exploited in preparing an engineered eggshell profile. This together with simultaneous calcination/ reduction in a dynamic hydrogen environment has been shown to further enhance dispersion and reducibility. Characterization techniques including BET, XPS, XRD, H-chemisorption and FTIR were employed. Catalyst activity, product selectivity, distribution and conversion were studied using a bench scale fixed bed reactor fitted with a GC/MS instrument.