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Supported metal catalysts for friedel-crafts alkylationHlatywayo, Tapiwa January 2013 (has links)
Doctor Educationis / The research focused on the synthesis, characterisation and activity of zeolite supported metal catalysts for the Friedel-Crafts alkylation of benzene with t-butyl chloride. Alkyl benzenes are traditionally produced via systems that employ the use of Lewis acids or strong mineral acids. There have been widespread concerns over these approaches based on their environmental impacts and separation difficulties. Recent approaches have endeavoured the much to use more environmentally eco-friendly systems and zeolites have proved to be versatile support materials. The use of zeolites has also shown to greatly improve product selectivity as well as easing separation constraints. However the adoption of zeolites on large scale Friedel-Crafts alkylation has been hampered by the high cost of zeolite production from commercial sources. On the other hand fly ash
has been found to be a viable starting material for zeolite synthesis. Apart from that
South Africa is faced with fly disposal challenges and there is continual accumulation of fly ash at the coal fired power stations, which provide about 77 % of the power produced in the country. In this light the use of fly ash will help to reduce the disposal constraints as well as providing a cheap starting material for zeolite synthesis. In this study the hierarchical Zeolite X has been successfully synthesised from fly ash via a hydrothermal treatment. The zeolite was then loaded with Fe/Mn via two approaches namely liquid phase ion exchange and incipient wetness impregnation. For comparison purposes seasoned commercial support materials namely HBEA and MCM- 41 were also loaded with the same metals and characterised with various techniques namely; HRSEM, EDS, HRTEM, XRD, SAED, ICP-OES and N2 adsorption analysis, It was found from the characterisation undertaken that the integrity of the respective supports was generally retained upon metal loading. Both the ICP-OES and the EDS proved that the desired metals were successfully introduced onto the zeolitic support materials. The calculated percentage metal loading for the catalysts prepared via incipient wetness impregnation was closely related to the actual values obtained from
the ICP-OES analysis for both the monometallic and the bimetallic catalysts (Fe/Mn). It was observed that the amount of metal that can be introduced on a zeolite via liquid phase ion exchange is largely dependent on the cation exchange capacity of the zeolite Supported metal catalysts for FC alkylation Page v
and of the catalysts prepared using 0.25 M Fe solution it was found that Zeolite X had the highest Fe wt% loading of 11.4 %, with the lowest loading of 2.2 % obtained with the MCM-41 supported catalyst. The XRD patterns for the both HBEA and the MCM-41 supported metal catalysts resembled the patterns of the respective prestine support materials except in the case of catalysts with anFe wt % of more than 10, which exhibited peaks due to the Fe2O3 crystallites. In the case of the hierarchical Zeolite X, the metal loaded support had a significant reduction in the XRD peak intensities. The prepared catalysts were tested for the alkylation of benzene with t-butyl chloride. The benzene was also used as the solvent. The alkylation reaction was carried out in a round bottomed flask under reflux conditions and stirring at a temperature of 45 oC over a period of 5 h. A total of 18 catalysts was tested and the highest percentage conversion of 100 % was obtained with the 10%FeH after a reaction time of 2 h. The general trend
obtained with the majority of the catalysts was characterised with a rapid initial increase and then steady state was achieved. Generally after a reaction time of 3 h almost all the catalysts had reached steady state in terms of the percentage conversion obtained. The outcomes reflect that the inclusion of Mn does not enhance the conversion but rather decreases it. It was also found that the Mn was not active in the alkylation of benzene as shown by the inactivity of the 10%MnM, where 10% by weight Mn was loaded on MCM-41. However the other monometallic catalysts containing Mn supported on Zeolite X and HBEA were found to be active. The activity is attributed to the presence of Brønsted acid sites in these zeolites which are not present in MCM-41. The selectivity studies reflect that the inclusion of Mn does slightly improve the selectivity towards the formation of the monoalkylated product (t-butyl benzene). The highest selectivity of 91.1 % was obtained with the 10%FeMnM after a reaction time of 4 h. MCM-41 supported catalysts had a relatively higher selectivity compared to the other supports. Considering the Fe monometallic catalysts tested it generally can be said
that the yield were in the order HBEA > MCM-41 > Zeolite X. It however should be
noted that the percentage yield is calculated from the conversion and selectivity
percentages, this implies that the factors affecting these parameters will consequently affect the percentage yield obtained. Supported metal catalysts for FC alkylation Page vi The alkylation reaction was found to be characterised by the formation of two intermediate products which could not be identified. These products were formed during the transient start up stages of the reaction and would disappear from the reaction mixture with longer reaction times, and after 3 h in almost all the reactions studied the intermediates were not detected in the reaction mixture. The main products found were the monoalkylated product (desired product) and the para isomer (1,4-t-di-butyl benzene). There were no other dialkylated isomers or trialkylated products detected. The formation of the para isomer was usually after a reaction time of 2 h in most reactions. The research managed to show that the hierarchical Zeolites X can be synthesised from
fly ash and ion exchange and incipient wetness impregnation are appropriate approaches that can be used to introduce Fe/Mn onto the support materials studied. The catalysts prepared were active to varying degrees in the Friedel-Crafts alkylation of benzene with t-butylchloride, with the exception of the 10%MnM which was found to be inactive.
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Functional silica materials for controlled release, sensing and elimination of target moleculesCandel Busquets, Inmaculada 29 July 2014 (has links)
La presente tesis doctoral titulada “Materiales de sílice funcionales para la
liberación controlada, detección y eliminación de moléculas de interés” se centra
en el diseño y desarrollo de materiales híbridos orgánico-inorgánicos mediante la
aplicación de los conceptos de Química Supramolecular. Durante el desarrollo de
la presente tesis doctoral se han preparado y caracterizado diferentes materiales
de base silícea para distintas aplicaciones.
La primera parte de la tesis se centra en el desarrollo de materiales de base silícea
capaces de variar su comportamiento fluorescente en función de la presencia o
ausencia de un cierto analito en el medio. Estos materiales emplean como soporte
nanopartículas de sílice que se funcionalizan superficialmente con dos unidades
diferentes, una coordinante y una indicadora (un fluoróforo). La interacción del
analito de interés (en nuestro caso aniones) con la unidad coordinante modificará
las propiedades emisivas del fluoróforo. Así, se han preparado dos materiales en
los cuales el grupo fluorescente es rodamina mientras que el grupo coordinante
es un imidazolato o una sal de guanidinio respectivamente. Una vez
caracterizados ambos materiales se estudió su comportamiento frente a
diferentes especies aniónicas a diferentes concentraciones resultando selectivos a
la presencia de benzoato (el material funcionalizado con imidazolatos),
dihidrógeno fosfato e hidrógeno sulfato (el material funcionalizado con sales de
guanidinio).
El tercer capítulo de la tesis se centra en la aplicación de materiales híbridos
orgánico-inorgánicos para la detección y eliminación de especies altamente
tóxicas como son los agentes neurotóxicos. Estos son compuestos
organofosforados capaces de causar graves lesiones en el sistema nervioso
central. En una primera aproximación se emplea el concepto de puerta molecular
para la detección de agentes neurotóxicos. Para ello, se utiliza como soporte
inorgánico un material mesoporoso de sílice (MCM-41) cuyos poros se cargan con
un colorante que actúa de indicador mientras que la superficie externa del mismo se funcionaliza con una molécula capaz de reaccionar con dichos agentes
neurotóxicos. Dicha molécula es capaz de interaccionar entre sí (mediante enlaces
de hidrógeno) formando una red que mantiene bloqueada la salida de los poros.
En presencia de DCP (dietilclorofosfato, un simulante de agente neurotóxico), y
después de que este reaccione con dicha molécula, se produce una reorganización
espacial que permite la liberación del colorante. De este modo, la presencia de los
agentes neurotóxicos está señalizada mediante un cambio de color. En una
segunda aproximación se aborda el uso de soportes inorgánicos de tipo MCM-41
como materiales para la eliminación de agentes neurotóxicos. Para ello se
modificaron químicamente las superficies de estos materiales silíceos mediante
tratamiento con distintas bases. Como consecuencia de este tratamiento básico
los silanoles de la superficie se desprotonan dando lugar a los correspondientes
silanolatos (nucleófilos fuertes). Estos silanolatos son capaces de reaccionar con
los agentes neurotóxicos descomponiéndolos y favoreciendo su eliminación de un
medio contaminado.
Por último, se estudia la aplicación de materiales híbridos orgánico-inorgánicos
funcionalizados con puertas moleculares en aplicaciones de liberación controlada,
concretamente, en liberación controlada intracelular de fármacos de interés. El
material híbrido consta de un soporte de sílice mesoporosa cuyos poros se cargan
con un compuesto citotóxico (camptotecina) y su superficie externa se
funcionaliza con una gluconamida. La presencia de una monocapa densa de
gluconamidas por el exterior del material inhibe la liberación del compuesto
citotóxico. Al añadir enzimas con capacidad para hidrolizar enlaces amida
(amidasa y pronasa) se produce la liberación de la camptotecina. El correcto
funcionamiento del material se comprobó in vitro e in vivo (en células HeLa). / Candel Busquets, I. (2014). Functional silica materials for controlled release, sensing and elimination of target molecules [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/39101 / TESIS
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Untersuchungen zur Wirt-Gast-Polymerisation von Vinylethern in Zeolithen und MCM-41Graeser, Annett 02 August 1996 (has links)
Im Rahmen dieser Diplomarbeit sollten die Moeglichkeiten einer
kationisch initiierten Polymerisation im Zeolithkanal ueberprueft werden.
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Overview of business models for Web 2.0 communitiesHoegg, Roman, Martignoni, Robert, Meckel, Miriam, Stanoevska-Slabeva, Katarina January 2006 (has links)
A new type of communities is gaining momentum on the web and is reshaping online communication and collaboration patterns and the way how information is consumed and produced [Gros04, Kolb06]. Examples of such communities are Wikipedia, MySpace, OpenBC, YouTube, Folksonomies, numerous Weblogs and others. In literature different terms can be found to denote the emerging and growing new phenomenon: social software [Bäch06] or peer production [Scho05]. In the year 2005, Tim O'Reilly popularized the term Web 2.0 [O'Reil05]. While the first two terms can be applied also to earlier, already established forms of online communities (for an overview see [Stan02]), the term Web 2.0 is mostly applied to emphasize the differences of emerging communities compared to earlier forms of online communities, encompassing various perspectives - technology, attitude, philosophy. (...)
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Nanostructured Porous High Surface Area Ceramics for Catalytic ApplicationsKrawiec, Piotr 20 December 2006 (has links)
In the present work new methods were developed for preparation of novel nanosized and nanostructured ceramic materials. Ordered mesoporous silica SBA-15 was found to be useful as a hard template for the nanocasting of silicon carbide and allowed the preparation of high temperature stable mesoporous silicon carbide ceramics. Chemical vapor infiltration of SBA-15 with dimethyldichlorosilane at elevated temperatures yields SiC/SBA-15 nanocomposites. The subsequent HF treatment of those composites resulted in silica removal and preparation of mesoporous silicon carbide with surface areas between 410 and 830 m2g-1 and high mesopore volume (up to 0.9 cm3g-1). The pore size (between 3 and 7nm in diameter) and surface area of mesoporous silicon carbide were controlled by adjusting the infiltration conditions (time, atmosphere). The mesoporous silicon carbide prepared via this method showed high structural thermal stability at 1300 oC, exceeding that of the SBA-15 template. However, the ordering on the mesoscopic scale was low. Nevertheless, highly ordered mesoporous silicon carbide materials were obtained via polymer melt infiltration in SBA-15. The low molecular weight polycarbosilane used as a preceramic precursor was converted at 1300 oC to silicon carbide inside the SBA-15, and after subsequent silica removal by HF, a highly ordered mesoporous material was obtained. Ordered mesoporous silicon carbide prepared by the methods reported here, may be an interesting material as a support due to its high temperature stability, chemical inertness, high thermal conductivity and semiconductor properties. In contrast to the nanocasting approach, based on the complete pore filling, also a new in-situ procedure for the preparation of finely dispersed metal and metal oxide particles inside ordered mesoporous silica was developed. A swelling agent (toluene) was used to deliver a hydrophobic platinum precursor into the surfactant micelles before addition of silica source. Such an in-situ method resulted in very high platinum incorporation (80-100%), not achieved for any other in-situ preparation procedures. Additionally, the presence of platinum allowed to decrease the template removal temperatures. Moreover, the method was also extended to other metal or metal oxide/ordered mesoporous silica systems. This may be especially interesting for the preparation of ordered mesoporous materials with low melting points, where typically the structure collapses during the high temperature calcinations process. The in-situ synthesized V2O5/MCM-41 materials were used to prepare VN/MCM-41 composites via nitridation in ammonia at 800oC. This method allowed to prepare highly dispersed, X-ray amorphous vanadium nitride species, with high activity in the propane dehydrogenation. Compared to nitridation of supported vanadium oxide prepared via the ex-situ procedure, in-situ synthesized materials showed similar catalytic activity, in spite of having significantly lower vanadium loading. As an alternative for the preparation of supported nitride materials, a novel preparation procedure of bulk not supported nanocrystalline vanadium nitride with high surface area was presented. Instead of pure oxide powder (which was typically used in the preparation of high surface area vanadium nitride catalysts), a macroporous amine intercalated V2O5 was used as the starting material. The obtained nitride consisted of small crystallites and had a surface area up to 198 m2g-1. Moreover, this foam-derived VN showed significantly improved activity as a catalyst in propane dehydrogenation. This novel preparation method could also be extended to other systems such as ternary VMoxNy nitrides.
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Synthesis, adsorption and structural properties of carbons with uniform and ordered mesoporesGierszal, Kamil Piotr 09 April 2008 (has links)
No description available.
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Synthesis of Ordered Mesoporous Silica and Alumina with Controlled Macroscopic MorphologiesAlsyouri, Hatem M. January 2004 (has links)
No description available.
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S?ntese de catalisadores nanoporosos na aus?ncia total e parcial de direcionadores org?nicos para pir?lise catal?tica de ?leos pesados e intermedi?riosCosta, Maria Jos? Fonseca 03 June 2013 (has links)
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Previous issue date: 2013-06-03 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The processing of heavy oil produced in Brazil is an emergency action and a strategic
plan to obtain self-sufficiency and economic surpluses. Seen in these terms, it is indispensable
to invest in research to obtain new catalysts for obtaining light fraction of hydrocarbons from
heavy fractions of petroleum. This dissertation for the degree of Doctor of Philosophy reports
the materials preparation that combine the high catalytic activity of zeolites with the greater
accessibility of the mesoporosity, more particularly the HZSM-5/MCM-41 hybrid, done by
synthesis processes with less environmental impact than conventional ones. Innovative
methodologies were developed for the synthesis of micro-mesoporous hybrid material by dual
templating mechanism and from crystalline zeolitic aluminosilicate in the absence of organic
template. The synthesis of hybrid with pore bimodal distribution took place from one-single
organic directing agent aimed to eliminate the use of organic templates, acids of any kind or
organic solvents like templating agent of crystalline zeolitic aluminosilicate together with
temperature-programmed microwave-assisted, making the experimental procedures of
preparation most practical and easy, with good reproducibility and low cost. The study about
crystalline zeolitic aluminosilicate in the absence of organic template, especially MFI type, is
based on use of H2O and Na+ cation playing a structural directing role in place of an organic
template. Advanced characterization techniques such as X-Ray Diffraction (XRD), Fourier
Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Highresolution
Transmission Electron Microscopy (HRTEM), Adsorption of N2 and CO2, kinetic
studies by Thermogravimetric Analysis (TGA) and Pyrolysis coupled to Gas
Chromatography/Mass Spectrometry (Pyrolysis-GC/MS) were employed in order to evaluate
the synthesized materials. Achieve the proposed objectives, has made available a set of new
methodologies for the synthesis of zeolite and hybrid micro-mesoporous material, these
suitable for catalytic pyrolysis of heavy oils aimed at producing light fraction / O processamento do petr?leo pesado produzido no Pa?s ? uma a??o emergencial e
estrat?gica para obter a auto-sufici?ncia e super?vits econ?micos. Neste sentido, ?
indispens?vel o investimento em pesquisas de novos catalisadores para obten??o de derivados
leves a partir de fra??es pesadas do petr?leo. O trabalho de doutorado aqui reportado dedicouse
? prepara??o de materiais que combinem, numa ?nica estrutura, a elevada atividade
catal?tica de ze?litas, com melhor acessibilidade de materiais mesoporosos, como a estrutura
h?brida HZSM-5/MCM-41, utilizando processos de s?ntese com menor impacto ambiental que
os convencionais. Metodologias inovadoras foram desenvolvidas para a s?ntese do catalisador
h?brido micro-mesoporoso ou ze?lito-mesoporoso por mecanismo de direcionamento
estrutural via duplo agente diretor org?nico e tamb?m a partir de estrutura zeol?tica sintetizada
na aus?ncia total de direcionador org?nico. Esse ?ltimo, tamb?m chamado de s?ntese do
h?brido com distribui??o bimodal de poros a partir de um ?nico agente diretor org?nico, visou
eliminar o uso dos direcionadores org?nicos, ?cidos de qualquer natureza ou solventes
org?nicos como molde estrutural da estrutura zeol?tica em conjunto com o m?todo
hidrot?rmico assistido por irradia??o via micro-ondas, tornando o procedimento experimental
de prepara??o pr?tico e simples, com boa reprodutibilidade e menor custo. A metodologia de
prepara??o da ze?lita MFI do tipo ZSM-5 utiliza H2O e c?tions Na+ no papel de
direcionamento estrutural e compensa??o de cargas na estrutura. T?cnicas relevantes de
caracteriza??o, como Difra??o de Raios-X (XRD), Espectroscopia no Infravermelho com
Transformada de Fourier (FTIR), Microscopia Eletr?nica de Varredura (SEM), Microscopia
Eletr?nica de Transmiss?o de Alta Resolu??o (HRTEM), Adsor??o de N2 e CO2, estudos
cin?ticos via An?lises Termogravim?tricas (TGA) e Pir?lise acoplada ? Cromatografia
Gasosa/Espectrometria de Massas (Pyrolysis-GC/MS), foram empregadas no intuito de
avaliar os materiais sintetizados. Alcan?ados os objetivos propostos, disponibilizou-se um
conjunto de novas metodologias para s?ntese de catalisadores zeol?ticos e h?bridos micromesoporosos,
estes adequados para pir?lise catal?tica de ?leos pesados visando ? produ??o de
derivados leves
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Degradacao termica e catalitica da borra oleosa de Petroleo com materiais nanoestruturados al-mcm-41 e AL-SBA-15Paulino, Ana Adalgisa Dias 04 November 2012 (has links)
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Previous issue date: 2012-11-04 / Aiming to reduce and reuse waste oil from oily sludge generated in large volumes by the oil
industry, types of nanostructured materials Al-MCM-41 and Al-SBA-15, with ratios of Si / Al
= 50, were synthesized , and calcined solids used as catalysts in the degradation of oily sludge
thermocatalytic oil from oilfield Canto do Amaro, in the state of Rio Grande do Norte.
Samples of nanostructured materials were characterized by thermogravimetric analysis (TG /
DTG), X-ray diffraction (XRD), scanning electron microscopy (SEM), absorption
spectroscopy in the infrared Fourier transform (FT-IR) and adsorption nitrogen (BET). The
characterization showed that the synthesized materials resulted in a catalyst nanostructure,
and ordered pore diameter and surface area according to existing literature. The oily sludge
sample was characterized by determining the API gravity and sulfur content and SARA
analysis (saturates, aromatics, resins and asphaltenes). The results showed a material
equivalent to the average oil with API gravity of 26.1, a low sulfur content and considerable
amount of resins and asphaltenes, presented above in the literature. The thermal and catalytic
degradation of the oily sludge oil was performed from room temperature to 870 ? C in the
ratios of heating of 5, 10 and 20 ? C min-1. The curves generated by TG / DTG showed a
more accelerated degradation of oily sludge when it introduced the nanostructured materials.
These results were confirmed by activation energy calculated by the method of Flynn-Wall, in
the presence of catalysts reduced energy, in particular in the range of cracking, showing the
process efficiency, mainly for extraction of lightweight materials of composition of oily
sludge, such as diesel and gasoline / Com o objetivo de reduzir e reutilizar o res?duo de borra oleosa de petr?leo, gerado em
grandes volumes pela ind?stria petrol?fera, materiais nanoestruturados dos tipos Al-MCM-41
e Al-SBA-15, com raz?es de Si/Al = 50, foram sintetizados, calcinados e utilizados como
s?lidos catal?ticos na degrada??o termocatal?tica da borra oleosa de petr?leo, proveniente do
campo petrol?fero Canto do Amaro, no estado do Rio Grande do Norte. As amostras dos
materiais nanoestruturados foram caracterizadas por an?lise termogravim?trica (TG/DTG),
difra??o de raios X (DRX), microscopia eletr?nica de varredura (MEV), espectroscopia de
absor??o na regi?o do infravermelho com transformada de Fourier (FT-IR) e adsor??o de
nitrog?nio (BET). A caracteriza??o mostrou que os materiais sintetizados resultaram em um
catalisador nanoestruturado, ordenado e com di?metro de poros e ?rea superficial de acordo
com a literatura existente. A amostra de borra oleosa foi caracterizada atrav?s da
determina??o do grau API e do teor de enxofre e da an?lise do SARA (saturados, arom?ticos,
resinas e asfaltenos). Os resultados mostraram um material equivalente ao petr?leo m?dio,
com grau API de 26,1, baixo teor de enxofre e com quantidade consider?vel de resinas e
asfaltenos, acima da apresentada na literatura. A degrada??o t?rmica e catal?tica da borra
oleosa de petr?leo foi realizada da temperatura ambiente at? 870?C, nas raz?es de
aquecimento de 5, 10 e 20oC min-1. As curvas geradas pela TG/DTG apresentaram uma
degrada??o mais acelerada da borra oleosa quando se introduziram os materiais
nanoestruturados. Esses resultados foram ratificados pela energia de ativa??o, calculada
atrav?s do m?todo de Flynn-Wall, em que a presen?a dos catalisadores reduziu a energia, em
especial na faixa de craqueamento, mostrando a efici?ncia do processo, principalmente para a
extra??o de materiais leves da composi??o da borra oleosa, como diesel e gasolina
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Photocatalysis studies using mesoporous modified V-MCM-48 Stober synthesis: acetaldehyde, carbon monoxide, ethanol, acetone, 2-propanol, & acetonitrileMahoney, Luther James January 1900 (has links)
Master of Science / Department of Chemistry / Kenneth J. Klabunde / Although Degussia-Huls P-25 TiO[subscript]2 semiconductor photocatalyst has high photodegradation rate for organic molecules, it works only under ultra-violet (UV) light. Mesoporous metal doped V-MCM-48 silica was synthesized under ambient conditions for use as a visible-light photocatalyst to convert toxic probe molecules to innocuous products: CO[subscript]2 + H[subscript]2O. The synthesis employed a modified Stober metal doped MCM-48 silica method. Powder X-ray diffraction (XRD), diffuse-reflectance-ultra-violet-visible (DR-UV-vis) spectroscopy, and N[subscript]2 adsorption-desorpton analysis characterization methods were completed on V-MCM-48 mesoporous material. These characterization methods indicate V-MCM-48 structure had formed with visible light absorption and mesoporous properties. Photocatalysis studies were completed with V-MCM-48 under dark, visible, and UV-light illumination conditions for the following probe molecules: acetaldehyde, carbon monoxide, ethanol, acetone, 2-propanol, and acetonitrile. Acetaldehyde over V-MCM-48 was converted to CO[subscript]2 under dark, visible, and UV-light conditions. Carbon monoxide photooxidation occurred over V-MCM-48 under visible and UV-light. Ethanol and acetonitrile had smaller photodegradation activity over V-MCM-48. Acetone and 2-propanol had no activity photocatalytically. Under dark and visible light illumination, V-MCM-48 consumed approximately one-half acetaldehyde and produced one-third CO[subscript]2 concentration as compared with the P-25 TiO[subscript]2 under UV-light. V-MCM-48 produced two-thirds of the amount of CO[subscript]2 in comparison to nanoparticle Au/ZnO catalyst under UV-light. The results infer V-MCM-48 might be useful in gas and liquid phase photocatalysis including water-splitting due to a high oxidation state (V[superscript]5+), visible light absorption, and high surface area. In conclusion, an extended literature review has been completed and literature employed extensively throughout the thesis with potential methods to further the research on V-MCM-48/Si-MCM-48 in catalysis, chromatography, adsorption/gas separation, and solar collection/water-splitting.
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