Statistically Guided Synthesis of MoV-Based Mixed-Oxide Catalysts for Ethane Partial Oxidation

The catalytic performance of Mo8V2Nb1-based mixed-oxide catalysts for ethane partial oxidation is highly sensitive to the doping of elements with redox and acid functionality. Specifically, control over product distributions to ethylene and acetic acid can be afforded via the specific pairing of redox elements (Pd, Ni, Ti) and acid elements (K, Cs, Te) and the levels at which these elements are doped. The redox element, acid element, redox/acid ratio, and dopant/host ratio were investigated using a three-level, four-factor factorial screening design to establish relationships between catalyst composition, structure, and product distribution for ethane partial oxidation. Results show that the balance between redox and acid functionality and overall dopant level is important for maximizing the formation of each product while maintaining the structural integrity of the host metal oxide. Overall, ethylene yield was maximized for a Mo8V2Nb1Ni0.0025Te0.5 composition, while acetic acid yield was maximized for a Mo8V2Nb1Ti0.005Te1 catalyst

Statistically Guided Synthesis of MoV- Based Mixed Oxide Catalysts for Ethane Partial Oxidation

The catalytic performance of Mo8V2Nb1-based mixed-oxide catalysts for ethane partial oxidation is highly sensitive to the doping of elements with redox and acid functionality. Specifically, control over product distributions to ethylene and acetic acid can be afforded via the specific pairing of redox elements (Pd, Ni, Ti) and acid elements (K, Cs, Te) and the levels at which these elements are doped. The redox element, acid element, redox/acid ratio, and dopant/host ratio were investigated using a three-level, four-factor factorial screening design to establish relationships between catalyst composition, structure, and product distribution for ethane partial oxidation. Results show that the balance between redox and acid functionality and overall dopant level is important for maximizing the formation of each product while maintaining the structural integrity of the host metal oxide. Overall, ethylene yield was maximized for a Mo8V2Nb1Ni0.0025Te0.5 composition, while acetic acid yield was maximized for a Mo8V2Nb1Ti0.005Te1 catalyst

A study of the oxidehydration of 1,2-propanediol to propanoic acid with bifunctional catalysts

[EN] The gas-phase oxidehydration (ODH) of 1,2-propanediol to propionic acid has been studied as an intermediate step in the multi-step transformation of bio-sourced glycerol into methylmethacrylate. The reaction involves the dehydration of 1,2-propanediol into propionaldehyde, which occurs in the presence of acid active sites, and a second step of oxidation of the aldehyde to the carboxylic acid. The two reactions were carried out using a cascade strategy and multifunctional catalysts, made of W-Nb-O, W-V-O and W-Mo-V-O hexagonal tungsten bronzes, the same systems which are also active and selective in the ODH of glycerol into acrylic acid. Despite the similarities of reactions involved, the ODH of 1,2-propanediol turned out to be less selective than glycerol ODH, with best yield to propanoic acid no higher than 13%, mainly because of the parallel reaction of oxidative cleavage, occurring on the reactant itself, which led to the formation of C-1-C-2 compounds.Bandinelli, C.; Lambiase, B.; Tabanelli, T.; De Maron, J.; Dimitratos, N.; Basile, F.; Concepción Heydorn, P.... (2019). A study of the oxidehydration of 1,2-propanediol to propanoic acid with bifunctional catalysts. Applied Catalysis A General. 582:1-9. https://doi.org/10.1016/j.apcata.2019.05.036S1958

Influence of Coordination Environment on Catalyst Structure and Function for CO2 Hydrogenation and Ethane Partial Oxidation

In this work, we set out to establish strong structure/activity relationships for various catalytic compositions and reactions. Through in situ spectroscopic approaches, specifically DRIFTS, Raman XPS, and XAFS, we were able to discern the reactive species in CO2 hydrogenation over highly active cobalt nanostructures, the relevant ensemble size and composition of single site catalysts for CO2 hydrogenation, and active vibrational modes of mixed oxide catalysts for ethane partial oxidation (EPO). First, we illustrate how tailoring surface orientations of Co3O4 catalysts on the nanoscale results in control over catalytic performance via the preferential formation of active surface species during CO2 hydrogenation. This resulted in over an order of magnitude increase in the methane turnover frequency on Co3O4 nanorods with the exposed {110}/{001} family of surface facets, as opposed to conventional Co3O4 nanoparticles with the exposed {111}/{001} family of surface facets. We found via in situ DRIFTS studies that this difference in catalytic performance for the Co3O4 nanorods was due to the inhibition of the formate spectator species. Furthermore, by studying the second hydrogenation step in CO2 hydrogenation, which is CO hydrogenation, we were able to discern that the formation of bridged CO was the key difference between the two catalyst. Second, cobalt and ruthenium single site catalyst were explored due to their highly uniform active sites; allowing for definitive claims as to which surface species are responsible for the reaction mechanisms. To characterize the structure and dispersion of the single-site catalysts, techniques such as UV-vis, XAFS, XPS, TPR, and Raman were vi utilized under ambient conditions as well as under reductive environments to simulate reaction conditions. For the case of cobalt single sites, the surface moieties under ambient and reductive environments coupled with their corresponding catalytic performance during CO2 hydrogenation allowed us to discern how the transition between isolated atoms to small nanoparticles affects the reaction mechanism. For ruthenium single site catalysts supported on boronnitride, we found atomic and/or subnanometer clusters to be over an order of magnitude more active than their analogous nanoparticles First, we illustrate how tailoring surface orientations of Co3O4 catalysts on the nanoscale results in control over catalytic performance via the preferential formation of active surface species during CO2 hydrogenation. This resulted in over an order of magnitude increase in the methane turnover frequency on Co3O4 nanorods with the exposed {110}/{001} family of surface facets, as opposed to conventional Co3O4 nanoparticles with the exposed {111}/{001} family of surface facets. We found via in situ DRIFTS studies that this difference in catalytic performance for the Co3O4 nanorods was due to the inhibition of the formate spectator species. Furthermore, by studying the second hydrogenation step in CO2 hydrogenation, which is CO hydrogenation, we were able to discern that the formation of bridged CO was the key difference between the two catalyst. Second, cobalt and ruthenium single site catalyst were explored due to their highly uniform active sites; allowing for definitive claims as to which surface species are responsible for the reaction mechanisms. To characterize the structure and dispersion of the single-site catalysts, techniques such as UV-vis, XAFS, XPS, TPR, and Raman were vi utilized under ambient conditions as well as under reductive environments to simulate reaction conditions. For the case of cobalt single sites, the surface moieties under ambient and reductive environments coupled with their corresponding catalytic performance during CO2 hydrogenation allowed us to discern how the transition between isolated atoms to small nanoparticles affects the reaction mechanism. For ruthenium single site catalysts supported on boronnitride, we found atomic and/or subnanometer clusters to be over an order of magnitude more active than their analogous nanoparticle reaction

Combinatorial Study of Oxidation Catalysts: Uncovering Synthesis-Structure-Activity Relationships

High throughput experimentation (HTE) in catalysis has proven useful in expediting materials discovery via parallelized synthesis, characterization, and testing of candidate materials. However, even in a high-throughput manner, the combinatorial explosion of relevant parameters far exceeds our ability to study. To further complicate the problem, a large time investment and great deal of characterization is often required to build an in-depth understanding of catalytic materials. It follows that the field of heterogeneous catalysis is rich with examples of catalytic systems that have been developed using trial and error efforts for which a lot is known but context is lacking. Techniques such as statistical design methodology can be used together with HTE to address this by facilitating more efficient and meaningful exploration of large parameter space problems. In this work, three examples of oxidation catalysis are highlighted where design of experiments was successfully paired with HTE to aid the catalyst development process and uncover novel synthesis-structure-activity relationships. In addition, the prepartion of polyacid functionalized gold nanomaterials for use in Alzheimer’s therapy will be discussed First, synthesis factors important in the one pot colloidal synthesis of cobalt oxide nanoparticles including surfactant type, heating regimen,reducingagent, and reagent concentrations were studied with a series of factorial designs. Factors were linked to structural parameters including grain size and morphology as well as CO oxidation activity parameters such aslight offtemperature and activation energy. Ultimately, experiments revealed that the density of catalytically active grain boundaries and structure of the CoOx intermediates were the most important factors in enhancing the cobalt oxide reactivity and provided models to tune these variables using synthesis conditions Second, the optimization of the co-promoter space for Cu-Ag/-Al2O3 catalzed ethylene epoxidation will be discussed, where an emphasis was placed on screening novel promoting materials and using factorial design to develop an understanding of how catalyst structure and promotional effects change with respect to promoter loading and impregnation sequence. It was found that the activity of the catalysts was sensitive to both the co-promoters used and the reactant feed composition which further experimentation revealed was linked to the Cu-Ag alloy behavior as well as the Ag particle size and morphology. Additional studies investigating the ethylene epoxidation activity of novel AgNP-Ag-LSX hybrid materials prepared with various post-synthetic modifications by collaborators will also be discussed. The partial oxidation of ethane to acetic acid and ethylene will be discussed as a third application in oxidation catalysis. In this work, the structure and activity of doped Mo8V2Nb1 mixed oxide catalysts were investigated. Specifically, the mixed oxide was doped with various redox (Pd,Ni,Ti) and acid (K,Te,Cs) elements at different redox:acid and dopant:host ratios; the effects of which were explored using a threelevel, four-factor full factorial design. An emphasis was placed on understanding how the incorporation of various dopants affected the structure of the mixed metal oxide and the redox:acid dopant balance needed to achieve the desired specificity to various partial oxidation products. In a slightly unrelated thrust, the development of polyacid functionalized gold nanoparticles and studies of their efficacy as Amyloid-aggregation inhibitors in Alzheimer’s therapy will be discussed. The main focus of this work was leveraging existing polymer science and nanomaterials synthesis knowledge to establish on-demand control of the polymer length and nanoparticle size for the development of functionalized AuNP therapeutics. Additionally, the experimental efforts of the project collaborators led to an understanding of how the PAA-AuNP properties (nanoparticle size and polymer length) changed their ability to inhibit Amyloid-aggregation

Gas Phase Transformation of (Bio) - Polyols into Carboxylic Acids by Means of Multifunctional Catalysis

The research activity carried out during the Ph.D aimed at the development of new synthetic routes for the production of acrylic and methacrylic acid using bio-alcohols as raw materials, respectively glycerol and propylene glycol. The first chapter of the thesis concerns the one-pot transformation of glycerol into acrylic acid, performed by using multifunctional catalysts. The overall process formally consists in two reaction steps: i) glycerol dehydration to acrolein, promoted by acid catalysis, and ii) acrolein oxidation to acrylic acid, promoted by redox catalysis. The design of suitable multifunctional catalysts is a complex matter and, so far, fundamental understanding behind the catalytic phenomenon remains unclear. In this context, the research work here reported aimed to shed light on the molecular-level relations that lie behind the catalytic results shown by several types of V-containing catalysts. The second chapter of the thesis concerns the study of a new synthetic route for the production of methacrylic acid starting from bio-propylene glycol. The overall process formally consists in three reaction steps: i) propylene glycol dehydration to propanal, ii) propanal oxidation to propionic acid, and iii) propionic acid condensation with formaldehyde, generated in-situ from methanol. Referring to reactions i) and ii), the research activity focussed on the possibility to perform the single-step gas-phase transformation of propylene glycol into propionic acid, by means of multifunctional catalysis (as previously done for glycerol one-pot transformation to acrylic acid). Finally, the study of the latter stage of the overall process to produce methacrylic acid was started, that is the condensation reaction between propionic acid and formaldehyde, generated in-situ from methanol. In particular, the catalytic activity of aluminium phosphate was fully investigated, so as to define the reactions that may occur when feeding propionic acid and methanol on pure acid catalysts

Keggin-Type Catalysts Partially Oxidize 2-Methyl-1,3- Propanediol to Methacrylic Acid in a Micro-Fluidized Bed Reactor

RÉSUMÉ Le méthacrylate de méthyle est le monomère du polyméthacrylate de méthyle. Ce dernier, commercialisé sous les noms de marques Acrylite®, Plexiglas®, Lucite®, Optix®, Perspex®, Oroglas®, Cyrolite®, Sumipex® et Altuglas®, a diverses applications industrielles dans les peintures et revêtements ou l’électronique, comme modificateur pour le PVC, ou pour les implants osseux Nagai (2001); Godfrey (1963); Kung (1994); W. Dormer et al. (1998); Smith et al. (1999). La demande en MMA dépassera les 4.8 millions de tonnes d’ici à 2020 Global Market Analysts (2016). La région Asie–Pacifique est son principal marché, elle inclut notamment la Chine, son premier producteur et consommateur mondial. L’Amérique du Nord et l’Europe se classent deuxième et troisième, respectivement, tandis que le Moyen–Orient, l’Afrique, et l’Amérique Latine représentent les marchés en plus forte croissance Global Market Analysts (2016). Le PMMA (produit à partir de MMA) dépassera lui les 2.8 millions de tonne en demande annuelle. Mitsubishi Rayon a ainsi rapporté une croissance de la demande de plus de 0.2 millions de tonnes en rythme annuel (5% to 6%) Nagai et Ui (2004); Program (2006); Schunk et Brem (2011). Cette hausse de la demande en PMMA se traduit en moyenne par une augmentation annuelle de l’ordre de 10% du prix au gros du MMA Jing (2012). En 2015, la demande globale égalait la capacité de production à l’échelon mondial Markit (2016); Global Market Analysts (2016). La production de méthacrylate de méthyle (MMA) par le procédé acétone cyanohydrine (ACH) dépend de matières premières couteuses et toxiques et souffre de faibles conversions. L’estérification de l’acide méthacrylique (MAA) en MMA est une alternative au ACH. Cependant, les procédés de synthèse de MAA requièrent plusieurs étapes et leurs catalyseurs ont une faible durée de vie. L’oxydation d’oléfines légères en acide méthacrylique (MAA) – en tant que matières premières alternative pour le MMA— réduit les lacunes du précédé actuel Montag et Mckenna (1991); Drent et Budzelaar (1996); Zhou et al. (2015). Toutefois, les voies proposées depuis ces matières premières souffrent également de faibles conversions, de multiples étapes et de la faible durée de vie des catalyseurs. Nous avons employé un micro-lit fluidisé gaz-solide pour oxyder partiellement, et pour la première fois, du 2–méthyl–1,3–propanediol (2MPDO) sur un catalyseur hétérogène. Au travers du choix du catalyseur, du design du micro-lit fluidisé, de la réaction des composés thermosensibles en produits à valeur ajouté, et du modèle cinétique, nous avons cherché à optimiser l’ensemble du procédé catalytique pour développer une nouvelle approche pour l’oxydation partielle du 2MDPO en produits chimiques de spécialité. Avant de s’attaquer au corps de ce projet de recherche, nous avons réalisé dans le second chapitre une étude compréhensive de l’ensemble des procédés actuels, commerciaux et potentiels permettant la “Synthèse catalytique d’acide méthacrylique et de méthacrylate de méthyle” (Chapitre 2 : “Catalysis for the synthesis of methacrylic acid and methyl methacrylate”) afin de comprendre les points suivants: 1. Les avantages et inconvénients des procédés actuels ; 2. Le choix, potentiel ou commercial, du catalyseur pour chaque approche ; 3. Les conditions opératoires optimales et les mécanismes réactionnels possibles. Pour le premier objectif spécifique, nous proposons un nouveau procédé hétérogène gaz-solide-liquide dans lequel nous atomisons le réactif, liquide, sur le catalyseur pour réaliser l’oxydation partielle du 2MPDO en MAA et en méthacroléine (MAC). À cet égard, nous avons assigné les chapitres 3 et 4 de cette thèse– ainsi que deux articles publiés– à cet objectif spécifique. Le chapitre 3 est intitulé : “Oxydation en phase gaz du 2–méthyl–1,3–propanediol en acide méthacrylique sur des catalyseurs hétéropolyacidiques” (“Gas phase oxidation of 2–methyl–1,3–propanediol to methacrylic acid over heteropolyacid catalysts”). Le quatrième chapitre, portant sur le même thème, est intitulé : “Oxydation partielle du 2–méthyl–1,3–propanediol en acide méthacrylique : modélisation expérimentale et du réseau neural” (“Partial oxidation of methyl–1,3–propanediol to methacrylic acid : experimental and neural network modeling”). Le 2MPDO liquide est atomisé par de l’argon sur la surface du catalyseur à une température de 250 °C. La première difficulté expérimentale est l’agglomération du catalyseur au cours du temps qui conduit à l’obstruction du distributeur après quelques expériences. Afin de surmonter ce problème, nous avons optimisé le ratio Ar/2MPDO (gaz/réactif liquide), la configuration de la buse, et la perte de charge. Parmi tous les catalyseurs hétérogènes synthétisés, les hétéropolycomposés de type Keggin sont ceux qui se sont montrés les plus actifs pour réaliser le clivage de la liaison C−H et oxyder sélectivement le 2MPDO en MAA+MAC. La température et le ratio 2MPDO:O2 affectent de façon prépondérante le rendement en produits désirés. Les autres éléments à considérer pour ce procédé sont la formation de coke, le haut taux de conversion, et la formation de sous-produits. Bien que nous ayons testé différent types de catalyseurs avec différentes conditions opératoires, nous n’avons toujours aucune idée de la nature de la relation entre structure du catalyseur et sélectivité en produits. Il nous faut également réfléchir à la nature des sites actifs pour ce type de catalyseur et pour cette réaction sachant que la température de calcination est le paramètre de synthèse ayant le plus d’impact sur les performances du catalyseur. Notre second objectif spécifique a ainsi consisté à calciner le catalyseur optimal (déterminé au premier objectif) à différentes températures. Nous avons caractérisé le catalyseur avec différentes techniques pour distinguer les différences induites par la calcination en termes de structures. Nous proposons ainsi un nouveau mécanisme qui lie la structure du catalyseur, les réactifs, et les produits. Les résultats du second objectif ont été publiés dans un article reproduits dans le chapitre 5. Le chapitre 5 est intitulé “Des catalyseurs de type Keggin à base de Cs, V et Cu oxydent partiellement le 2–méthyl–1,3–propanediol en acide méthacrylique” (“Cs, V, Cu Keggin–type catalysts partially oxidize 2–methyl–1,3–propanediol to methacrylic acid”). La dernière étape a consisté à modéliser les données expérimentales des différents mécanismes. Le modèle de Mars et Van Krevelen caractérise nos données mieux que ceux de Langmuir– Hinshelwood ou de Eley–Rideal : la séquence réactionnelle implique à la fois des réactions en série et en parallèle dans lesquelles le 2MDPO forme du MAC et du MAA directement et où le MAC formé réagit ensuite pour donner du MAA. Le taux de réaction en série du MAC en MAA est 50 fois plus rapide que celui de la réaction en parallèle (formation du MAC et du MAA). La réaction de 2MPDO sur les sites oxydés pour former des produits est la étape limitante. Le chapitre 6 intitulé “Cinétique d’oxydation du 2-méthyle-1,3-propanediol en acide méthacrylique”. À l’aide de la compréhension glanée dans ce projet, nous pouvons conclure que l’oxydation partielle du 2MDPO dans un réacteur à lit fluidisé gaz-solide est une approche novatrice pour valoriser le 2MDPO en produits chimiques de spécialité et en acides carboxyliques en particulier. Dans le système gaz-solide-liquide, le 2MDPO est introduit lentement dans le lit avec lequel il est en contact direct. Il s’évapore, et s’oxyde soit à la surface du catalyseur, soit dans le lit. Il est converti en acides carboxyliques. Les catalyseurs acides à base de vanadium et de molybdène font preuve de performances prometteuses pour la conversion du 2MDPO en produits à valeur ajoutée. Si l’activité catalytique affecte le rendement et la sélectivité en produits, les conditions opératoires telles que la température et la concentration en O2 ont elles-aussi un impact majeur. Le modèle cinétique proposé prédit de façon précise, tout en restant simple, la conversion en 2MDPO, la sélectivité en produits, et l’effet des différents paramètres. Le co-produit de la méthode ici-présentée est du syngaz, un mélange de CO+H2 pouvant être transformé en carburants et autres produits chimiques. ---------- ABSTRACT Methyl methacrylate (MMA) is a specialty monomer for poly–methyl–methacrylate (PMMA), which is marketed under trademarks Acrylite®, Plexiglas®, Lucite®, Optix®, Perspex®, Oroglas®, Cyrolite®, Sumipex® and Altuglas® and applied in diverse industries including paints and coatings, electronics, as a modifier for PVC, and as bone inserts Nagai (2001); Godfrey (1963); Kung (1994); W. Dormer et al. (1998); Smith et al. (1999). Demand of MMA will surpass 4.8 million metric tonne by 2020 Global Market Analysts (2016), where Asia–Pacific is the main market in which China ranks first for production and consumption. North America and Europe are ranked second and third, respectively, while the Middle East, Africa, and Latin America are the areas growing the fastest Global Market Analysts (2016). PMMA (produced from MMA) surpassed 2.8 million tonne annually. Mitsubishi Rayon reported annual growth in demand of more than 0.2 million tonnes (5% to 6%) Nagai et Ui (2004); Program (2006); Schunk et Brem (2011). Due to the increasing demand for PMMA, the price of bulk MMA increased by 10% annually Jing (2012).In 2015, the worldwide demand equalled the global supply capacity Markit (2016); Global Market Analysts (2016). The acetone cyanohydrin process (ACH) to produce methyl methacrylate (MMA) relies on expensive and toxic feedstock and suffers from low yield. Methacrylic acid (MAA) esterification to MMA is an alternative to ACH. However, current processes to produce MAA require multi steps and catalysts lifetime are short. Oxidizing light olefins to methacrylic acid (MAA) – as an alternative feedstock for MMA– reduces the deficiencies of the current process Montag et Mckenna (1991); Drent et Budzelaar (1996); Zhou et al. (2015). However, the proposed routes from these feedstocks also suffer from low yield, multiple steps, and short catalyst lifetime. We employed a gas–solid micro fluidized bed reactor to partially oxidize 2–methyl–1,3–propanediol (2MPDO) over the heterogeneous catalysts for the first time. We targeted developing a catalytic process, the catalyst used, temperature sensitive materials to value added chemicals, a micro fluidized-bed reactor, and kinetic modeling to pave a new road in the partial oxidation of 2MPDO into specialty chemicals. Before starting the main body of the research, we did a comprehensive study as the second chapter entitled “Catalysis for the synthesis of methacrylic acid and methyl methacrylate” on all current commercialized/potential processes to understand the following aspects: 1. The advantages or disadvantages of the current approaches; 2. The potential commercial or developed catalysts for each route; 3. The optimum operating conditions and possible mechanisms. As the first specific objective, we propose a new gas-solid-liquid heterogeneous process in which we atomize the liquid reactant over the catalyst to partially oxidize 2MPDO into MAA and methacrolein (MAC). In this regard, we assigned chapters 3 and 4 of this thesis–as two published papers– to this specific objective. The third chapter is “Gas phase oxidation of 2–methyl–1,3–propanediol to methacrylic acid over heteropolyacid catalysts”. The fourth chapter is also assigned to “Partial oxidation of methyl–1,3–propanediol to methacrylic acid: experimental and neural network modeling”. Argon atomized the liquid 2MPDO over the catalyst surface operating at 250 °C. However, the first encountered issue was catalyst agglomeration with time which blocked injector after some experiments. To overcome this problem, we optimized the Ar/2MPDO ratio, the nozzle configuration and pressure drop. Among the synthesized heterogeneous catalysts, Keggin–type heteropolycompounds were active to cleavage C−H bond of hydrocarbon and selectively oxidize 2MPDO to MAA+MAC. Temperature and the 2MPDO:O2 ratio affect the yield of desired products. Coke formation, high conversion and forming byproducts are the other issues of this process. Although we tested several kind of catalysts over different operating conditions, we still have no idea what the correlation between catalyst structure and products selectivity. On the other hand what the active sites in this catalyst type for this reaction? Moreover, calcination temperature is the most effective parameters on charge transfer among metal ions of catalyst that affects its performance. Therefore as the second objective, we calcined the optimum catalyst structure (obtained from the first objective) at different temperatures. We characterized the catalyst with several techniques to distinguish the differences in their structures. We propose a new mechanism that correlates the catalyst structure, reactant, and products. The results of second objective published as a paper in chapter 5. Chapter 5 entitled “Cs, V, Cu Keggin–type catalysts partially oxidize 2–methyl–1,3–propanediol to methacrylic acid”. As the last step, we modeled experimental data by different mechanisms. The Mars and Van Krevelen model characterizes the experimental data better than the either the Langmuir–Hinshelwood or Eley–Rideal models: The reaction sequence involves both parallel and series reactions in which 2MPDO for MAC and MAA directly and MAC reacts to form MAA but the series reaction rate to MAA is 50 times faster than the parallel reaction rate. Reacting of 2MPDO over the oxidized sites to form products is the rate–limiting step. Chapter 6 entitled “Oxidation kinetics of 2–methyl–1,3–propanediol to methacrylic acid”. With the help of the insight gained in this study we can say that the partial oxidation of 2MPDO in the gas–solid fluidized–bed reactor is a novel approach for upgrading 2MPDO to value–added chemicals and in particularly carboxylic acids as an open chain product from 2MPDO. In the gas-solid-liquid system, 2MPDO was introduced to the bed slowly, directly contacted with the catalyst, evaporates, and oxidized on the surface of the catalyst or in the bed and converted to carboxylic acids. Acidic catalyst based on vanadium and molybdenum demonstrated promising performance in the conversion of 2MPDO to fine chemicals. However, catalyst activity and selectivity changes the liquid product yield and selectivity but reaction condition such as temperature and O2 concentration have a considerable effect, as well. The proposed kinetic model, however, was simple but accurately predicts 2MPDO conversion, product selectivity and the effect of various parameters. The by-product of the introduced method was syngas, which can be converted into fuel and chemicals

Selective oxidation of methane to formaldehyde by oxygen over SBA-15-supported molybdenum oxides

The selective oxidation of CH4 to formaldehyde by oxygen and its kinetics studies were investigated over MoOx/SBA-15 under atmospheric pressure. The comparative studies on catalytic reaction showed that the activity of polymeric MoOx species was significantly higher than that of isolated MoOx. The maximum HCHO yield was achieved over 20 wt% MoOx/SBA-15 catalyst at 873 K Although the studies on contact time effect indicated that HCHO was the primary product over both isolated and polymeric Mo species, the CH4 conversion followed different mechanisms: the reaction over isolated MoOx, species was a first-order reaction, whereas the other was a higher-order reaction. The catalytic activity of SBA-15-supported Mo-V-O mixed oxide was also investigated in this study. Hydrogen temperature-programmed reduction (H-2-TPR), UV-visible (UV-vis) spectroscopy and X-ray photoelectron spectra (XPS) studies were performed to characterize the supported MoOx. species, results showed that the nature of MoOx species remained unchanged during the reaction. (C) 2008 Elsevier B.V. All rights reserved.AcRF tier 2 [M45120006 ARC 13/07]; AcRF tier 1 [M52120049 RG45/06]; NSF of China [20433030]; National Basic Research Program of China [2005CB221408