New nickel catalysts supported on highly porous alumina intercalated laponite for methane reforming with CO2

Alumina intercalated laponite (Al-laponite) was prepared with a polyethylene oxide (PEO) surfactant and used as supports of nickel catalysts for the carbon dioxide reforming reaction with methane to synthesis gas. The effects of the supports of intercalated laponite and catalyst preparation on catalytic activity, stability and carbon deposition were investigated for the above reforming reaction. We found that the pore structure of the Al-laponite supports can be tailored with the surfactant and the catalyst with well-developed porosity exhibited higher catalytic activity and a longer time of catalyst stability. (C) 2001 Elsevier Science B.V. All rights reserved.

Isomerization-cracking of n-octane on catalysts based on heteropolyacid H3Pw12O40 and heteropolyacid supported on zirconia and promoted with Pt and Cs

Isomerization - cracking of n-octane was studied using H3PW12O40 (HPA) and HPA supported on zirconia and promoted with Pt and Cs. The addition of Pt and Cs to the supported HPA did not modify the Keggin structure. The Pt addition to the supported HPA did not substantially modify the total acidity; however, the Brönsted acidity increased significantly. Cs increased the total acidity and Brönsted acidity. A linear relation was observed between the n-C8 total conversion and Brönsted acidity. The most adequate catalysts for performing isomerization and cracking to yield high research octane number (RON) are those with higher values of Brönsted acidity.

Aqueous-phase reforming of renewables for selective hydrogen production in the presence of supported platinum catalysts

The evolution of our society is impossible without a constant progress in life-important areas such as chemical engineering and technology. Innovation, creativity and technology are three main components driving the progress of chemistry further towards a sustainable society. Biomass, being an attractive renewable feedstock for production of fine chemicals, energy-rich materials and even transportation fuels, captures progressively new positions in the area of chemical technology. Knowledge of heterogeneous catalysis and chemical technology applied to transformation of biomass-derived substances will open doors for a sustainable economy and facilitates the discovery of novel environmentally-benign processes which probably will replace existing technologies in the era of biorefinary. Aqueous-phase reforming (APR) is regarded as a promising technology for production of hydrogen and liquids fuels from biomass-derived substances such as C3-C6 polyols. In the present work, aqueous-phase reforming of glycerol, xylitol and sorbitol was investigated in the presence of supported Pt catalysts. The catalysts were deposited on different support materials, including Al2O3, TiO2 and carbons. Catalytic measurements were performed in a laboratory-scale continuous fixedbed reactor. An advanced analytical approach was developed in order to identify reaction products and reaction intermediates in the APR of polyols. The influence of the substrate structure on the product formation and selectivity in the APR reaction was also investigated, showing that the yields of the desired products varied depending on the substrate chain length. Additionally, the influence of bioethanol additive in the APR of glycerol and sorbitol was studied. A reaction network was advanced explaining the formation of products and key intermediates. The structure sensitivity in the aqueous-phase reforming reaction was demonstrated using a series of platinum catalysts supported on carbon with different Pt cluster sizes in the continuous fixed-bed reactor. Furthermore, a correlation between texture physico-chemical properties of the catalysts and catalytic data was established. The effect of the second metal (Re, Cu) addition to Pt catalysts was investigated in the APR of xylitol showing a superior hydrocarbon formation on PtRe bimetallic catalysts compared to monometallic Pt. On the basis of the experimental data obtained, mathematical modeling of the reaction kinetics was performed. The developed model was proven to successfully describe experimental data on APR of sorbitol with good accuracy.

Catalytic upgrading of biomass extractives to fine chemicals over supported ionic liquid catalysts (SILCAs)

Behovet av förnyelsebar energi ökar ständigt eftersom det finns en strävan att minska beroendet av fossila bränslen. Dessutom är tillgångar av fossila bränslen begränsade. Miljövänliga processer för bioraffinaderier erbjuder en stor möjlighet för produktion av energi, bränslen och kemikalier. Den finska och svenska skogsindustrin har en lång tradition i utnyttjandet av skogsbiomassor. Bioraffinaderier som integreras med pappers- och cellulosaindustrin kan frambringa både ekonomiska och ekologiska fördelar i framställning av traditionella och biobaserade produkter. I doktorsarbetet studerades omvandling av extraktivämnen till finkemikalier som kan användas t.ex. av läkemedelsindustrin. Extraktivämnen fås ur biomassa. I forskningsarbetet framställdes biobaserade finkemikalier med hjälp av katalysatorer som baserar sig på joniska vätskor. Biomassan består av cellulosa, hemicellulosa, lignin och extraktivämnen, vilka huvudsakligen är terpener, vaxer och fettsyror. Extraktivämen är vedens komponenter, som kan separeras ur vedmaterialet med hjälp av neutrala lösningsmedel. Joniska vätskekatalysatorer som var immobiliserade på fasta bärare utnyttjades för isomerisering av α,β-pinenoxider samt hydrogenering citral. Inverkan av joniska vätskor på katalysatorns aktivitet och reaktionernas produktfördelning undersöktes under varierande reaktionsbetingelser. Kinetiska modeller för pinenoxidens isomeriseringsreaktioner beskrev väl experimentellt upptäckta skillnader mellan olika katalysatorer. --------------------------------------------------- Uusiutuvan energian tarve on kasvussa, koska riippuvuutta fossiilisista polttoaineista pyritään vähentämään. Tämän lisäksi fossiilisten polttoaineiden varannot ovat rajalliset. Ympäristöystävälliset biojalostusprosessit ovat näin ollen suuri mahdollisuus energian, polttoaineiden ja kemikaalien tuotannossa. Suomen ja Ruotsin metsäteollisuudella on pitkät perinteet metsäbiomassojen hyödyntämisessä. Paperi- ja selluteollisuuden yhteyteen integroiduilla biojalostamoilla voidaan luoda taloudellisia ja ympäristöllisiä etuja sekä perinteisten että biopohjaisten tuotteiden valmistuksessa. Väitöstyössä on tutkittu biomassan uuteaineiden kemiallista muuntamista hienokemikaaleiksi, joita voidaan käyttää esimerkiksi lääkeaineteollisuudessa. Biopohjaisia hienokemikaaleja on valmistettu biomassan uuteaineista ionisiin nesteisiin perustuvilla katalyyteillä. Biomassa koostuu selluloosasta, hemiselluloosasta, ligniinistä sekä uuteaineista, jotka ovat pääosin terpeenejä, vahoja tai rasvahappoja. Uuteaineet ovat puun komponentteja, jotka voidaan erottaa puusta neutraalien liuottimien avulla. Kiinteän kantajan päälle immobilisoituja ionisia nestekatalyyttejä (Supported Ionic Liquid Catalyst) hyödynnettiin α,β-pineenioksidien isomerisointireaktioissa sekä sitraalin vedytysreaktioissa. Ionisten nesteiden vaikutusta katalyyttien aktiivisuuteen sekä reaktioiden tuotejakaumaan tutkittiin erilaisissa reaktio-olosuhteissa. Pineenioksidien isomerisointireaktioiden kineettiset mallit kuvasivat hyvin kokeellisesti todettuja katalyyttien eroavaisuuksia.

Studies on the preparation of Supported nickel catalysts using bis(ethylenediamine)nickel(II) complexes as precursors

Dept.of Applied Chemistry,Cochin University of Science and Technology

New supported transition metal complexes: synthesis, characterization and application as catalysts for oxidation/hydrodesulphurization reactions

This thesis deals with the synthesis and charcterisation of some supported transition metal complexes and their catalytic properties. Two industrially important reactions were carried out: i) cyclohexanol oxidation and ii) hydrodesulphurization of diesel. Thesis is divided into nine chapters. An overview of the heterogenised homogeneous systems is given in Chapter 1. Chapter 2 deals with the materials and methods used for the preparation and characterisation. Details regarding the synthesis and characterisation of zeolite encapsulated transition metal complexes are given in Chapter 3 to Chapter 7. In Chapter 8, the results of catalytic activity studies of the cyclohexanol oxidation using the zeolite encapsulated complexes are presented. Details of preparation of hydrodesulphurization catalysts through the molecular designed dispersion method, their characterization and catalytic activity studies are presented in Chapter 9. References are given at the end of the thesis.

Studies on some supported transition metal complex and metal oxide catalysts for oxidation reactions

Zeolite encapsulated transition metal complexes have received wide attention as an effective heterogenized system that combines the tremendous activity of the metal complexes and the attractive features of the zeolite structure. Zeolite encapsulated complexes offer a bright future for attempts to replace homogeneous systems retaining its catalytic activity and minimizing the technical problems. especially for the partial oxidation of organic compounds. Studies on some zeolite encapsulated transition metal complexes are presented in this thesis. The ligands selected are technically important in a bio-mimetic or structural perspective. Attempts have been made in this study to investigate the composition, structure and stability of encapsulated complexes using available techniques. The catalytic activity of encapsulated complexes was evaluated for the oxidation of some organic compounds. The recycling ability of the catalyst as a result of the encapsulation was also studied.Our studies on Cu-Cr/Al2O3, a typical metal oxide catalyst. illustrate the use of design techniques to modify the properties of such conventional catalysts. The catalytic activity of this catalyst for the oxidation of carbon monoxide was measured. The effect of additives like Ce02 or Ti02 on the activity and stability of this system was also investigated. The additive is potent to improve the activity and stability ofthe catalyst so as to be more effective in commercial usage.

Synthesis, characterization and catalytic activity of Nd203 supported V205 catalysts

A series of rare-earth neodymia supported vanadium oxide catalysts with various V205 loadings ranging from 3 to 15 wt.% were prepared by the wet impregnation method using ammonium metavanadate as the vanadium precursor. The nature of vanadia species formed on the support surface is characterized hy a series of different physicochemical techniques like X-ray diffraction (XRD). Fourier transform infrared spectroscopy (FTIR). BET surface area, diffuse reflectance UV-vis spectroscopy (DR UV-vis), thermal analysis (TG-DTG/DTA) and SEM. The acidity of the prepared systems were verified by the stepwise temperature programmed desorprion of ammonia (NH3-TPD) and found that the total acidity gets increased with the percentage of vanadia loading. XRD and FT1R results shows the presence of surface dispersed vanadyl species at lower loadings and the formation of higher vanadate species as the percentage composition of vanadia is increased above 9 wt.%. The low surface area of the support. calcination temperature and the percentage of vanadia loading are found to influence the formation of higher vanadia species. The catalytic activity of the V205-Nd203 catalysts was probed in the liquid phase hydroxylation of phenol and the result show that the present catalysts are active at lower vanadia concentrations.

High activity supported gold catalysts by incipient wetness impregnation

It is generally thought that catalysts produced by incipient wetness impregnation (IW) are very poor for low temperature CO oxidation, and that it is necessary to use methods such as deposition-precipitation (DP) to make high activity materials. The former is true, indeed such IW catalysts are poor, and we present reactor data, XPS and TEM analysis which show that this is due to the very negative effect of the chloride anion involved in the preparation, which results in poisoning and excessive sintering of the Au particles. With the DP method, the chloride is largely removed during the preparation and so poisoning and sintering are avoided. However, we show here that, contrary to previous considerations, high activity catalysts can indeed be prepared by the incipient wetness method, if care is taken to remove the chloride ion during the process. This is achieved by using the double impregnation method (DIM). In this a double impregnation of chloroauric acid and a base are made to precipitate out gold hydroxide within the pores of the catalyst, followed by limited washing. This results in a much more active catalyst, which is active for CO oxidation at ambient temperature. The results for DIM and DP are compared, and it is proposed that the DIM method may represent an environmentally and economically more favorable route to high activity gold catalyst production. (C) 2007 Elsevier B.V. All rights reserved.

Polymer-supported nitroxyl catalysts for selective oxidation of alcohols

Novel non-toxic poly(ethylene glycol)-supported 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) moieties are demonstrated to give an excellent interfacial catalysis for the selective oxidation of alcohols to the corresponding carbonyl species in biphasic media and investigation for the recovery of these new macromolecular catalysts via precipitation with diethyl ether after catalysis has also been briefly studied.

Hydrogen spillover on carbon-supported metal catalysts studied by inelastic neutron scattering. Surface vibrational states and hydrogen riding modes

Hydrogen spillover on carbon-supported precious metal catalysts has been investigated with inelastic neutron scattering (INS) spectroscopy. The aim, which was fully realized, was to identify spillover hydrogen on the carbon support. The inelastic neutron scattering spectra of Pt/C, Ru/C, and PtRu/C fuel cell catalysts dosed with hydrogen were determined in two sets of experiments: with the catalyst in the neutron beam and, using an annular cell, with carbon in the beam and catalyst pellets at the edge of the cell excluded from the beam. The vibrational modes observed in the INS spectra were assigned with reference to the INS of a polycyclic aromatic hydrocarbon, coronene, taken as a molecular model of a graphite layer, and with the aid of computational modeling. Two forms of spillover hydrogen were identified: H at edge sites of a graphite layer (formed after ambient dissociative chemisorption of H-2), and a weakly bound layer of mobile H atoms (formed by surface diffusion of H atoms after dissociative chernisorption of H-2 at 500 K). The INS spectra exhibited characteristic riding modes of H on carbon and on Pt or Ru. In these riding modes H atoms move in phase with vibrations of the carbon and metal lattices. The lattice modes are amplified by neutron scattering from the H atoms attached to lattice atoms. Uptake of hydrogen, and spillover, was greater for the Ru containing catalysts than for the Pt/C catalyst. The INS experiments have thus directly demonstrated H spillover to the carbon support of these metal catalysts.

Aerogel-coated metal nanoparticle colloids as novel entities for the synthesis of defined supported metal catalysts

Nanometer metal particles of tailored size (3-5 nm) and composition prepared via inverse microemulsion were encapsulated by ultrathin coatings (<2.5 nm) of inorganic porous aerogels covered with surface -OH groups. These composite materials formed metastable colloids in solvent(s), and the organic surfactant molecules were subsequently removed without leading to aggregation (the ethanolic colloid solution was shown to be stable against flocculation for at least weeks). We demonstrate that the totally inorganic-based composite colloids, after the removal of surfactant, can be anchored to conventional solid supports (gamma-alumina, carbons) upon mixing. Application of a high temperature resulted in the formation of strong covalent linkages between the colloids and the support because of the condensation of surface groups at the interface. Detailed characterizations (X-ray diffraction (XRD), pore analysis, transmission electron microscopy (TEM), CO chemisorption) and catalytic testing (butane combustion) showed that there was no significant metal aggregation from the fine metal particles individually coated with porous aerogel oxide. Most of these metal sites on the coated nanoparticles with and without support are fully accessible by small molecules hence giving extremely active metal catalysts. Thus, the product and technology described may be suitable to synthesize these precursor entities of defined metal sizes (as inks) for wash coat/impregnation applications in catalysis. The advantages of developing inorganic nanocomposite chemical precursors are also discussed.

Preparation of supported Pt(0) nanoparticles as efficient recyclable catalysts for hydrogenation of alkenes and ketones

A magnetically recoverable Pt(0) catalyst was prepared by in situ H(2) reduction of Pt(2+) species bound to an amino modified silica-coated magnetic nanoparticles. Compared to ordinary silica (maximum uptake Pt 0.03 wt%), the amino-functionalized silica surfaces were loaded with 1.95 wt% of metal. The supported Pt(0) nanoparticles exhibit high catalytic activity in the hydrogenation of alkenes and ketones under solventless mild reaction conditions. Partially hydrogenated products could also be isolated. The magnetic property of the catalyst grants a fast and efficient product isolation compared to traditional methods used in heterogeneous systems that generally make use of time- and solvent-consuming procedures. (C) 2009 Elsevier B.V. All rights reserved.

Ethanol steam reforming for production of hydrogen on magnesium aluminate-supported cobalt catalysts promoted by noble metals

The performance of noble metal (Pt, Ru, Ir)-promoted Co/MgAl(2)O(4) catalysts for the steam reforming of ethanol was investigated. The catalysts were characterized by energy-dispersive X-ray spectroscopy, Xray diffraction, UV-vis diffuse reflectance spectroscopy, temperature-programmed reduction, temperature-programmed oxidation and X-ray absorption near edge structure (XANES). The results showed that the formation of inactive cobalt aluminate was suppressed by the presence of a MgAl(2)O(4) spinel phase. The effects of the noble metals included a marked lowering of the reduction temperatures of the cobalt surface species interacting with the support. It was seen that the addition of noble metal stabilized the Co sites in the reduced state throughout the reaction. Catalytic performance was enhanced in the promoted catalysts, particularly CoRu/MgAl(2)O(4), which showed the highest selectivity for H(2) production. (C) 2009 Elsevier B.V. All rights reserved.

Nickel catalysts supported on ZrO2, Y2O3-stabilized ZrO2 and CaO-stabilized ZrO2 for the steam reforming of ethanol: Effect of the support and nickel load

Catalysts with various nickel loads were prepared on supports of ZrO2, ZrO2-Y2O3 and ZrO2-CaO, characterized by XRD and TPR and tested for activity in ethanol steam reforming. XRD of the supports identified the monoclinic crystalline phase in the ZrO2 and cubic phases in the ZrO2-Y2O3 and ZrO2-CaO supports. In the catalysts, the nickel impregnated on the supports was identified as the NiO phase. In the TPR analysis, peaks were observed showing the NiO phase having different interactions with the supports. In the catalytic tests, practically all the catalysts achieved 100% ethanol conversion, H-2 yield was near 70% and the gaseous concentrations of the other co-products varied in accordance with the equilibrium among them, affected principally by the supports. It was observed that when the ZrO2 was modified with Y2O3 and CaO, there were big changes in the CO and CO2 concentrations, which were attributed to the rise in the number of oxygen vacancies, permitting high-oxygen mobility and affecting the gaseous equilibrium. The liquid products analysis showed a low selectivity to liquid co-products during the reforming reactions. (c) 2007 Published by Elsevier B.V.