Modeling of carbon monoxide oxidation kinetics over NASA carbon dioxide laser catalysts

The recombination of CO and O2 formed by the dissociation of CO2 in a sealed CO2 laser discharge zone is examined. Conventional base-metal-oxide catalysts and conventional noble-metal catalysts are not effective in recombining the low O2/CO ratio at the low temperatures used by the lasers. The use of Pt/SnO2 as the noble-metal reducible-oxide (NMRO), or other related materials from Group VIIIA and IB and SnO2 interact synergistically to produce a catalytic activity that is substantially higher than either componet separately. The Pt/SnO2 and Pd/SnO2 were reported to have significant reaction rates at temperatures as low as -27 C, conditions under which conventional catalysts are inactive. The gas temperature range of lasers is 0 + or - 40 C. There are three general ways in which the NMRO composite materials can interact synergistically: one component altering the properties of another component; the two components each providing independent catalytic functions in a complex reaction mechanism; and the formation of catalytic sites through the combination of two components at the atomic level. All three of these interactions may be important in low temperature CO oxidation over NMRO catalysts. The effect of the noble metal on the oxide is discussed first, followed by the effect of the oxide on the noble metal, the interaction of the noble metal and oxide to form catalytic sites, and the possible ways in which the CO oxidation reaction is catalyzed by the NMRO materials

CO-oxidation catalysts: Low-temperature CO oxidation over Noble-Metal Reducible Oxide (NMRO) catalysts

Oxidation of CO to CO2 is an important reaction technologically and environmentally and a complex and interesting reaction scientifically. In most cases, the reaction is carried out in order to remove CO as an environmental hazard. A major application of heterogeneous catalysts is catalytic oxidation of CO in the exhaust of combustion devices. The reaction over catalysts in exhaust gas is fast and often mass-transfer-limited since exhaust gases are hot and O2/CO ratios are high. The main challenges to catalyst designers are to control thermal sintering and chemical poisoning of the active materials. The effect of the noble metal on the oxide is discussed, followed by the effect of the oxide on the noble metal, the interaction of the noble metal and oxide to form unique catalytic sites, and the possible ways in which the CO oxidation reaction is catalyzed by the NMRO materials

Policies and Motivations for the CO2 Valorization through the Sabatier Reaction Using Structured Catalysts. A Review of the Most Recent Advances

The current scenario where the effects of global warming are more and more evident, has motivated different initiatives for facing this, such as the creation of global policies with a clear environmental guideline. Within these policies, the control of Greenhouse Gase (GHG) emissions has been defined as mandatory, but for carrying out this, a smart strategy is proposed. This is the application of a circular economy model, which seeks to minimize the generation of waste and maximize the efficient use of resources. From this point of view, CO2 recycling is an alternative to reduce emissions to the atmosphere, and we need to look for new business models which valorization this compound which now must be considered as a renewable carbon source. This has renewed the interest in known processes for the chemical transformation of CO2 but that have not been applied at industrial level because they do not offer evident profitability. For example, the methane produced in the Sabatier reaction has a great potential for application, but this depends on the existence of a sustainable supply of hydrogen and a greater efficiency during the process that allows maximizing energy efficiency and thermal control to maximize the methane yield. Regarding energy efficiency and thermal control of the process, the use of structured reactors is an appropriate strategy. The evolution of new technologies, such as 3D printing, and the consolidation of knowledge in the structing of catalysts has enabled the use of these reactors to develop a wide range of possibilities in the field. In this sense, the present review presents a brief description of the main policies that have motivated the transition to a circular economy model and within this, to CO2 recycling. This allows understanding, why efforts are being focused on the development of different reactions for CO2 valorization. Special attention to the case of the Sabatier reaction and in the application of structured reactors for such process is paid

Study of Cu-Zn and Au/TiO2 Catalysts on Anodized Aluminum Monoliths for Hydrogen Generation and Purification

This work reports the preparation of Cu-Zn and Au/TiO2 catalysts on anodized aluminum monoliths(AAM). The structured catalysts were studied for the generation of H2 by methanol steam reforming (MSR) and its purification by preferential oxidation of CO (CO-PrOx). Initially, it was possible to generate a surface with whiskers and larger surface area by hydrothermal treatment of the AAM. Subsequently, the structured catalysts were synthesized by incipient wetness impregnation (IWI) and ydrothermal synthesis (HS). IWI synthesis allowed for the deposition of a larger amount of catalytic material than HS, with very good adhesion. The TiO2-IWI structured catalyst presented a homogeneous catalytic coating, with the presence of agglomerated particles. On theother hand, Cu-Zn-IWI showed good dispersion of the deposited particles with a homogeneous surface coating. EDX analysis corroborated the presence of Ti, Cu and Zn in all the catalytic surfaces. The incorporation of Au over TiO2-IWI structured catalysts was successfully performed by IWI using a colloidal solution of gold nanoparticles.MSR was studied over the developed metallic monoliths functionalized with Cu-Zn by the IWI method. The samples showed promising results in terms of activity, selectivity, and stability. Both diluted and concentrated methanol + water feeds were assayed. Complete methanol conversion was achieved for the diluted feed. Maximum methanol conversions of 55% with 60% H2 yield were measured when the concentrated feed was selected. Promising results were also achieved for the Au-based structured catalysts in the CO-PrOx in an H2- rich atmosphere. Although CO conversions of approximately 60% were achieved, operating with higher catalyst loadings would be recommended to reach the high CO conversions required for PrOx catalysts.Fil: Adrover, María Esperanza. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Boldrini, Diego Emmanuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Jiménez Divins, Nuria. Universidad Politecnica de Catalunya; EspañaFil: Casanovas Hoste, Adria. Universidad Politecnica de Catalunya; EspañaFil: Tonetto, Gabriela Marta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Lopez, Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Llorca Piqué, Jordi. Universidad Politecnica de Catalunya; Españ

Reaction kinetics for the synthesis of methanol from CO and H2 on a copper catalyst = Reaktionskinetik der methanolsynthese aus CO und H2 auf einem kupferkatalysator

The kinetics for the low-pressure synthesis of methanol from CO and H2 were studied in a small integral reactor. The mole fraction of CO was varied from 0.1 to 0.54, the total pressure from 3 to 9 MPa and the temperature from 483 to 545 K.\ud \ud Using the maximum likelihood approach, seventeen possible reaction rate correlations were evaluated statistically. Among these models three appear to fit the experimental data satisfactorily

Potential Routes for Thermochemical Biorefineries

This critical review focuses on potential routes for the multi-production of chemicals and fuels in the framework of thermochemical biorefineries. The up-to-date research and development in this field has been limited to BTL/G (biomass-to-liquids/gases) studies, where biomass-derived synthesis gas (syngas) is converted into a single product with/without the co-production of electricity and heat. Simultaneously, the interest on biorefineries is growing but mostly refers to the biochemical processing of biomass. However, thermochemical biorefineries (multi-product plants using thermo-chemical processing of biomass) are still the subject of few studies. This scarcity of studies could be attributed to the limitations of current designs of BTL/G for multi-production and the limited number of considered routes for syngas conversion. The use of a platform chemical (an intermediate) brings new opportunities to the design of process concepts, since unlike BTL/G processes they are not restricted to the conversion of syngas in a single-reaction system. Most of the routes presented here are based on old-fashioned and new routes for the processing of coal- and natural-gas-derived syngas, but they have been re-thought for the use of biomass and the multi-production plants (thermochemical biorefinery). The considered platform chemicals are methanol, DME, and ethanol, which are the common products from syngas in BTL/G studies. Important keys are given for the integration of reviewed routes into the design of thermochemical biorefineries, in particular for the selection of the mix of co-products, as well as for the sustainability (co-feeding, CO2 capture, and negative emissions).Ministerio de Educación FPU Program (AP2010-0119)Ministerio de Economía y Competitividad ENE2012-3159

Value-added Chemicals from Biomass by Heterogeneous Catalysis

I den samtidige debat om ressourceudnyttelse har anvendelsen af biomasse været diskuteret som en alternativ carbon-kilde til de fossile reserver med henblik på at reducere CO2-emissionen til atmosfæren. Erstatningen eller supplementet til de oliebaserede transportbrændstoffer gennem konversion af biomasse er allerede etableret. Fremstilling af kemikalier fra biomasse har haft ringere bevågenhed. Denne afhandling beskriver og evaluerer en søgen efter en alternativ konversionsrute, baseret på biomasseføde og under anvendelse af en heterogen katalysator, som er i stand til at omsætte føden til et merværdi-kemikalie. Projektarbejdet i denne forbindelse er udført med en tværfaglig tilgang omfattende fra fundamentale katalysatorundersøgelser, gennem eksperimenter, karakterisering og procesevalueringer til markedsanalyse. Rationalet herfor er søgt gennem aktiverne i den opnåede bæredygtige ressourceudnyttelse for sådan en proces og under hypotesen, at lønsomheden af processen, i sammenligning med de konventionelle teknologier, yderligere kan opnås gennem fordelen ved bevarelsen af kemiske C-C bindinger i biomasse-baserede føder. Med udgangspunkt i ethanol som eksempel på en biomasse-baseret føde, som har beholdt en C-C binding fra det oprindelige biomasse-udgangsstof, bliver aspekterne for at udnytte heterogen katalyse til dets omsætning til merværdi-kemikalier undeersøgt. Gennem en simpel analyse af kendte, men ikke-industraliserede procesruter, bliver ethanol til eddikesyre-ruten identificeret som én, der viser gode perspektiver. Inkorporeringen af en nyttig katalysator i en effektiv proces er afgørende for potentialet af den overordnede procesinnovation. En gruppe Cu baserede katalysatorer, som viser sig aktive i pågældende konversion, bliver identificeret i en forundersøgelseseksperimentrække. Under hensynet til handlefriheden bliver endvidere procesudviklingsmuligheder afdækket, baseret på de opnåede eksperimentelle vidnesbyrd, teori og proceselementer beskrevet i litteraturen (fortrinsvis patent-). Der bliver søgt beskyttelse af de relaterede opfindelser gennem indlevering af tre patentansøgninger. Afhandlingens vigtigste bidrag er afspejlet i den endelige konklusion, at en ethanol til eddikesyreproces og tilhørende katalysator, begge genstande for videreudvikling, er identificeret. Forståelsen af den katalytiske opførsel af udvalgte katalysatorer, Cu spinel (CuAl2O4) og Cu/SiO2, bliver opnået gennem karakterisering heraf såvel som målinger af aktivitet, selektivitet og stabilitet bl.a. i formålsudviklede testopstillinger. Gennem adskillige karakteriseringsanalyser (XAFS, XRPD, SEM, TEM, TPR, carbon analysis etc.) kan det konkluderes, at den hurtige deaktivering af Cu spinel katalysatoren skyldes dannelsen af højmolekylære kulholdige stoffer som dækker katalysatoroverfladen, katalyseret af sure alumina sites, der opstår under katalysatoraktiveringen. Denne forklaring er i overensstemmelse med adskillige observerede fænomener for katalysatoren. Cu/SiO2 - katalysatoren, som har en inert support, viser langt højere robusthed over for procesvariationer, men udviser umiddelbart en for lav katalytisk aktivitet set fra en industriel vinkel. Adskillige måder til forbedring af aktiviteten bliver belyst. F.eks. indikeres en aktivitetsafhængighed af Cu-krystalstørrelsen ved en sammenligning af aktivitet og XRPD analyser for nedknuste og hele katalysatorpiller. Der bliver udledt empiriske kinetiske modeller, i god overensstemmelse med de opnåede eksperimentelle data for Cu/SiO2-katalysatoren, for at understøtte etableringen af en forbedret økonomisk vurdering af den undersøgte proces. Ekstrapolation af de udledte modeller indikerer tilfredsstillende aktivitet i det industrielle trykområde. Cu/SiO2-katalysatoren er endvidere i stand til at klare delvist oxidative dehydrogeneringsbetingelser, som tillader betydelige procesforbedringer. Slutteligt bliver ethanol til eddikesyre processen sat i en større sammenhæng ved i et tilbageblik at revurdere de i arbejdet anvendte metoder, markedets indflydelse på processens chancer, konklusioner og forbedringsmuligheder for processen. Endeligt, i betragtning af nogle fremadrettede alternative procesmuligheder, gives mine konkluderende anbefalinger under hensynet til det oprindelige projektformål. Afhandlingens resultater viser, med udgangspunkt i et enkelt eksempel på biomassekonversion, at udnyttelsen af biomasse i produktionen af kemikalier er lovende fra et teknisk synspunkt. Men risikoen for markedsprisudsving, domineret af fossilt baserede kemikalier, stiller endvidere kriteriet om en pålidelig økonomisk margin. Derfor bør man under markedshensyn undersøge alternativer. I tillæg til de tekniske konklusioner forekommer det, at en tvær-disciplinær tilgang til procesinnovation er fordelagtig.In the contemporary debate on resource utilisation, biomass has been discussed as an alternative carbon source to fossil reserves in order to reduce the emission of CO2 to the atmosphere. The replacement or supplement of oil based transportation fuels through biomass based conversions has already been implemented. The subject on chemical production has received less attention. This thesis describes and evaluates the quest for an alternative conversion route, based on a biomass feedstock and employing a heterogeneous catalyst capable of converting the feedstock, to a value-added chemical. The project work to fulfil the above objective has been conducted with a multi-disciplinary approach ranging from fundamental catalyst research, through experiments, characterisation and process evaluation to market analysis. The motivation herein is sought in the assets of sustainable resource utilisation obtained for such a process and the hypothesis that process feasibility in comparison with the conventional synthesis gas based technologies may further be attainable, taking advantage of the conservation of chemical C-C bonds in biomass based feedstocks. With ethanol as one example of a biomass based feedstock, having retained one C-C bond originating from the biomass precursor, the aspects of utilising heterogeneous catalysis for its conversion to value added chemicals is investigated. Through a simple analysis of known, but not industrialised catalytic routes, the direct conversion of ethanol to acetic acid product is identified to show good perspectives. The nesting of a useful catalyst and an effective process is crucial to the potential of the overall process innovation. In a pre-screening study, a group of Cu based catalysts active in the conversion have been identified. Considering the freedom to operate, the prospects of process development are further identified through process calculations based on the experimental evidence attained, theory and the process elements described in literature (primarily patent-related). The protection of the process inventions made in relation to this is sought through the filing of three patent applications. The most important contributions of this thesis are reflected in the eventual conclusion that an ethanol to acetic acid process and a related catalyst, both subject to further development, are identified. The understanding of the catalytic behaviour of down-selected catalysts, Cu spinel (CuAl2O4) and Cu/SiO2, is obtained through characterisation as well as activity, selectivity and stability studies in appropriately developed experimental set-ups. Through numerous characterisation analyses (XAFS, XRPD, SEM, TEM, TPR, carbon analysis etc.) the rapid deactivation of the Cu spinel catalyst may be concluded to be attributed to the formation of high molecular carbonaceous compounds covering the catalytic surface, being catalysed by acidic alumina sites present during and after catalyst activation. This theory explains several phenomena observed for this catalyst. The Cu/SiO2 catalyst, having an inert support, shows far higher robustness to process variations, but immediately exhibits a too low activity from an industrial angle. Several means of improving its activity are elucidated. For example an activity dependence on the Cu crystal size is indicated by the comparison of the activity and XRPD analyses obtained for crushed and whole catalyst pellets. Empirical kinetic models, in good agreement with the experimental data obtained for the Cu/SiO2 catalyst, are developed in order to support the establishment of an improved economic evaluation of the investigated process. Extrapolation of the derived model to the industrial pressure regime indicates a satisfactory activity. The Cu/SiO2 catalyst is further able to withstand partly oxidative dehydrogenation conditions, allowing for immense process improvements. Finally, the ethanol to acetic acid process is put into a broader context, by reviewing the methods used in this work, the market influence on its fate, the conclusions and suggested improvements listed. Eventually, with an outlook on some alternative process possibilities, my recommendations are given under the consideration of the initial project objective. The results of the thesis, taking one example of biomass conversion, show that the utilisation of biomass in the production of chemicals by heterogeneous catalysis is promising from a technical point of view. But risks of market price excursions dominated by fossil based chemicals further set a criterion of a solid economic margin. Therefore, under market considerations other alternatives are to be investigated. In addition to the technical conclusions it appears that a multi-disciplinary approach to process innovation is advantageous

Supercritical Water Gasification: Practical Design Strategies and Operational Challenges for Lab-Scale, Continuous Flow Reactors

Optimizing an industrial-scale supercritical water gasification process requires detailed knowledge of chemical reaction pathways, rates, and product yields. Laboratory-scale reactors are employed to develop this knowledge base. The rationale behind designs and component selection of continuous flow, laboratory-scale supercritical water gasification reactors is analyzed. Some design challenges have standard solutions, such as pressurization and preheating, but issues with solid precipitation and feedstock pretreatment still present open questions. Strategies for reactant mixing must be evaluated on a system-by-system basis, depending on feedstock and experimental goals, as mixing can affect product yields, char formation, and reaction pathways. In-situ Raman spectroscopic monitoring of reaction chemistry promises to further fundamental knowledge of gasification and decrease experimentation time. High-temperature, high-pressure spectroscopy in supercritical water conditions is performed, however, long-term operation flow cell operation is challenging. Comparison of Raman spectra for decomposition of formic acid in the supercritical region and cold section of the reactor demonstrates the difficulty in performing quantitative spectroscopy in the hot zone. Future designs and optimization of SCWG reactors should consider well-established solutions for pressurization, heating, and process monitoring, and effective strategies for mixing and solids handling for long-term reactor operation and data collection