Porous Silica-Based Organic-Inorganic Hybrid Catalysts: A Review

[EN] Hybrid organic-inorganic catalysts have been extensively investigated by several research groups in the last decades, as they allow combining the structural robust-ness of inorganic solids with the versatility of organic chemistry. Within the field of hybrid catalysts, synthetic strategies based on silica are among the most exploitable, due to the convenience of sol-gel chemistry, to the array of silyl-derivative precursors that can be synthesized and to the number of post-synthetic functionalization strategies available, amongst others. This review proposes to highlight these advantages, firstly describing the most common synthetic tools and the chemistry behind sol-gel syntheses of hybrid catalysts, then presenting exemplificative studies involving mono- and multi-functional silica-based hybrid catalysts featuring different types of active sites (acid, base, redox). Materials obtained through different approaches are described and their properties, as well as their catalytic performances, are compared. The general scope of this review is to gather useful information for those approaching the synthesis of organic-inorganic hybrid materials, while providing an overview on the state-of-the art in the synthesis of such materials and highlighting their capacities.This research was funded by Spanish Government (MAT2017-82288-C2-1-P and Severo Ochoa Excellence Program SEV-2016-0683) and MULTY2HYCAT (EU-Horizon 2020 funded project under grant agreement no. 720783).Erigoni, A.; Díaz Morales, UM. (2021). Porous Silica-Based Organic-Inorganic Hybrid Catalysts: A Review. Catalysts. 11(1):1-39. https://doi.org/10.3390/catal11010079S13911

Optimization of Process Flowsheets through Metaheuristic Techniques

This book presents a multi-objective optimization framework for optimizing chemical processes. The proposed framework implements a link between process simulators and metaheuristic techniques. The proposed approach is general, and there can be used any process simulator and any metaheuristic technique. This book shows how to implement links between different process simulators such as Aspen Plus®, HYSYS®, SuperPro Designer®, and others, linked to metaheuristic techniques implemented in Matlab®, Excel®, C++, or other programs. This way, the proposed framework allows optimizing any process flowsheet implemented in the process simulator and using the metaheuristic technique, and this way the numerical complications through the optimization process can be eliminated. Furthermore, the proposed framework allows using the thermodynamic, design, and constitutive equations implemented in the process simulator to implement any process

Sustainable Catalytic Processes for the Synthesis and Use of Organic Carbonates

The present study is focused on the development and improvement of sustainable catalytic processes for the synthesis of organic carbonates. In particular, the condensation reaction between carbon dioxide and several alcohols and diols has been investigated using a new generation of mesoporous nanosilicas functionalized by the insertion of amino groups on the catalyst surface. This reaction were performed in a high-pressure batch vessel (autoclave). Moreover, the carbonate interchange reaction (CIR) of the simplest linear organic carbonate, dimethyl carbonate (DMC) with several alcohols has been implemented by means of a new lab-scale reactive distillation system. In this new system, the distilled mixture is continuously passed over molecular sieves able to promote a selective adsorption of methanol (co-product of the reactions) while DMC is continuously refluxed back into the reaction batch. In this way, we were able to promote an efficient shift of the reaction equilibria toward the formation of the desired products. This system allowed us to achieve up to 90% isolated yield of pyrocatechol carbonate (PCC), a new and previously scarcely investigated carbonate. The PCC has been used as a new and more efficient carbonate source for the selective synthesis of symmetric carbonates and for the synthesis of glycerol carbonate (GlyC). GlyC has been also used as glycidol intermediate, for the condensation reaction with catechol in order to obtain the efficient synthesis of 2-hydroxymethy-1,4-benzodioxane (HMB) an important intermediate for the pharma industry. Finally, some of the synthesized carbonates were tested for the gas-phase phenol alkylation showing an interesting reactivity that could be properly modulated by changing the reaction conditions and the catalyst acid-base properties

POLYORGANOSILOXANES: MOLECULAR NANOPARTICLES, NANOCOMPOSITES AND INTERFACES

Five research projects described. First, a reproducible, lab-scale synthesis of MQ silicone copolymers is presented. MQ copolymers are commercially important materials that have been ignored by the academic community. One possible reason for this is the difficulty of controlling and reproducing the preparative copolymerizations that have been reported. A reproducible method for lab-scale preparation was developed that controls molecular weight by splitting the copolymerization into the discrete steps of sol growth from silicate precursor and end-capping by trimethylsiloxy groups. Characterization of MQ products implicates that they are composed of highly condensed, polycyclic structures. The MQ copolymers prepared in the first project were observed to form tenacious emulsions and foams. This was an obvious indication of surface activity and led to further investigation. No open literature reports any measurements of MQ copolymers at interfaces. In this second project, selected MQ structures were studied at three interfaces: the air-water interface, the oil-water interface and the solid-air interface of supported MQ monolayers. The qualitative surface activity of MQ is confirmed and quantified. Residual silanols are found to be responsible for surfactantcy in MQ copolymers. The third and fourth projects encompass research in Silicone-CNT composites. The first part of this work describes the ease with which CNTs can be dispersed into silicone matrices. Changes in silicone chemistry can improve CNT dispersion resulting in improved conductivities and mechanical reinforcement at CNT loadings of only fractions of a weight percent. The second portion of work on nanocomposites involves the discovery and investigation of the dramatic increase in thermal stability of silicone elastomers containing CNTs. Thermogravimetric analysis and pyrolysis gas chromatography-mass spectrometry indicate that the CNT network constrains silicone polymer chains and alters the mechanisms of decomposition. The last project uses the Piers-Rubinsztajn reaction to rapidly and cleanly modify silicon oxide surfaces. This reaction has been studied very little as a method to modify surfaces and there has yet to be any work that measures dynamic contact angles on smooth surfaces. Trialkylsilane and methylsiloxane monolayers were prepared and analyzed. Monolayer densities are low in this reaction and result in anomalously low contact angle hysteresis for alkylsilane monolayers. Wetting properties in precise methylsiloxane polymer monolayers are shown to depend on graft structure. Dynamic contact lines from the liquid-like mobility of these grafts results in low contact angle hysteresis

Industrial applications of principles of green chemistry

Cross-linked polyethylene has higher upper use temperature than normal polyethylene and is used as an insulating material for electricity carrying cables and hot water pipes. The most common method of inducing crosslinks is by reaction with silanes. After incorporation of silanes into polyethylene and upon hydrolysis with ambient moisture or with hot water, Si-O-Si crosslinks are formed between the various linear polyethylene chains. Industrially, this reaction is performed routinely. However, the efficiency of this reaction with respect to the silane is low and control of product distribution is difficult. A precise fundamental understanding is necessary to be able to manipulate the reactions and thus, allow for the facile processing of the polymers. Hydrocarbon models of polymers - heptane, dodecane - are being used to study this reaction in the laboratory. For the reaction, vinyltrimethoxysilane is used as the grafting agent along with di-tert-butyl peroxide as the radical initiator. MALDI, a mass spectrometric technique is used for the analysis of the product distribution after work-up. Advanced NMR techniques (COSY, HSQC, DEPT, APT, HMBC) are being conducted on the grafted hydrocarbon compounds to gain an in-depth understanding of the mechanism and regiochemistry of the grafting reaction. Scalable and cost effective methods to capture CO2 are important to counterbalance some of the global impact of the combustion of fossil fuels on climate change. The main options available now include absorption, adsorption and membrane technology. Amines, especially monoethanolamine, have been the most commercialized technology. However, it is not without disadvantages. House et al have investigated the energy penalty involved in the post-combustion CO2 capture and storage from coal-fired power plants and found that 15-20% reduction in the overall electricity usage is necessary to offset the penalty from capturing and storing 80% of United States coal fleet's CO2 emssions1. Novel non-aqueous amine solvents, developed by the Eckert Liotta group, react with CO2 to form ionic liquids. The ionic liquids readily desorb CO2 upon heating, regenerating the reactive amines and this cycle can be carried out multiple times. An iterative procedure is being adopted to develop amine solvents for CO2 capture. Thermodynamic information like reversal temperature and boiling point of the solvents are collected; they are then used to formulate structure property relationships which allow for new molecules to be engineered. On reaction with CO2, there is a sharp increase in viscosity which is unfavorable from a processing standpoint. Many approaches to mitigate and control viscosity are being studied as well. 1House et al, Energy Environ Sci, 2009, 2, 193-205MSCommittee Chair: Dr Charles Eckert; Committee Co-Chair: Dr Charles Liotta; Committee Member: Dr Amyn Tej

Printed inorganic transistors

Thesis (Ph. D.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2003.Includes bibliographical references (leaves 146-175).Forty years of exponential growth of semiconductor technology have been predicated on the miniaturization of the transistors that comprise integrated circuits. While complexity has greatly increased within a given area of processed silicon, the cost per area has not decreased. Current fabrication methods are further hindered by high facility costs and environmentally unfriendly processing. Moving to a new means of semiconductor fabrication may drastically reduce both financial and environmental costs. One such approach is based on the extension of printing techniques to the fabrication of electronic devices. Such printed electronics are envisioned to enable applications in flexible displays and electronic paper, personal fabrication, wearable computing, and disposable medical diagnostics. This dissertation focuses on the development of printable materials, specifically inorganic semiconductor inks. At the outset of this research, organic semiconductors were the only materials known and pursued as printable semiconductors. The ability to process organic semiconductors in common organic solvents makes them amenable to a wide range of printing technologies, but their electrical performance is fundamentally limited and their utility is confined to applications in which only low speeds are required. The goal of this thesis was to demonstrate the feasibility of printing inorganic materials, the same materials that are used to fabricate high quality semiconductor devices. Cadmium selenide was studied as a model inorganic semiconductor and silicon was studied because of its commercial dominance. The insolubility and high processing temperatures of inorganic semiconductors, both of which can prevent(cont.) their use in printed electronics, were overcome through the use of nanoparticle inks. At very small sizes, nanoparticles can be highly soluble in organic solvents and can have a pronounced melting point depression. Leveraging these size-dependent properties, the first semiconductor nanoparticle inks were developed using cadmium selenide and the first all-printed inorganic thin film transistors were demonstrated. Printed active layers in thin film transistors attained a semiconductor mobility of 1 cm²V⁻¹s⁻¹and an ON/OFF ratio in excess of 10⁴. Further development of inorganic nanoparticle inks and efforts to extend this approach to silicon are described, addressing silicon nanoparticle synthesis, purification, and ink formulation.Brent Ridley.Ph.D

The Treatment of Saline Solutions Utilizing Ceramic Membranes in Membrane Distillation Processes

Die Entsalzung ist eine der wichtigsten Technologien, um den Frischwasserbedarf in vielen Regionen der Welt sicherzustellen. Bevölkerungswachstum, der Klimawandel und stetig steigender Konsum werden die Bedeutung von Entsalzungstechnologien weiterwachsen lassen. Die Möglichkeit des Einsatzes etablierter konventioneller Verfahren wird begrenzt durch die hohen ökologischen und ökonomischen Kosten dieser Verfahren. Unkonventionelle Entsalzungsverfahren wie die Membrandestillation (MD) bieten einige Vorteile, mit denen sie konventionelle Verfahren jenseits dieser Limitationen ergänzen können. Die MD ist ein thermisch angetriebener Prozess, in welchem eine hydrophobe Membran das warme, flüssige Feed räumlich von der kälteren Permeatseite trennt, während nur dampfförmige Moleküle durch die Membran permeieren können. Wie in allen membranbasierten Trennprozessen bestimmen die Charakteristika der verwendeten Membran die Leistungsfähigkeit (Massentransport, Rückhaltevermögen und Energieeffizienz) des Prozesses und das damit verbundene kommerzielle Interesse. Durch ihre intrinsisch hydrophoben Materialeigenschaften und ihren guten Massentransfercharakteristika ist die Verwendung von Polymermembranen in der MD aktuell Stand der Technik. Um die Einsatzmöglichkeiten von MD Verfahren auf aggressive Lösungen zu erweitern, werden thermisch, mechanisch und chemisch stabile Membranen benötigt. Obwohl keramische Membranen im Vergleich zu Polymermembranen eine höhere Stabilität aufweisen (wodurch die Behandlung von aggressiven Lösungen mit MD-Verfahren prinzipiell möglich wird) muss die Eignung von keramischen Membranen für MD-Verfahren wissenschaftlich belegt und ein Konzept zur Membranoptimierung entwickelt werden. Im Rahmen dieser Arbeit wurden verschiedene Typen modifizierter keramischer Membranen (z.B. Materialauswahl und Schichtaufbau) vollständig im Hinblick auf ihre spezifischen Membraneigenschaften (z.B. Porengröße, Wärmeleitfähigkeit und hydrophobe Eigenschaften) charakterisiert und anschließend unter Verwendung von salzhaltigen Lösungen in der Direktkontaktmembrandestillation (DCMD) und der Vakuummembrandestillation (VMD) getestet. Diese Daten wurden genutzt, um den Stofftransport von asymmetrischen keramischen Membranen unter Verwendung eines anerkannten VMD-Modells (basierend auf dem Dusty-Gas-Modell) zu berechnen und um die Leistungsfähigkeit (d.h. Stabilität, Stofftransport, Selektivität und Energieeffizienz) von modifizierten keramischen Membranen in der MD in Hinblick auf spezifische Membraneigenschaften und Verfahrensparameter zu bewerten. Anschließend wurde die Eignung von keramischen Membranen für MD-Prozesse evaluiert und Optimierungskonzepte für keramische Membranen vorgeschlagen. Damit wurde mit dieser Arbeit die Grundlage gelegt, die Kommerzialisierung von keramischen Membranen in der MD voranzutreiben. Keramische Membranen wurde mit verschiedenen Molekülen hinsichtlich ihrer Oberflächeneigenschaften modifiziert. Dadurch konnte ein nicht-fluorisiertes Molekül als potenzielle Alternative zu den üblicherweise verwendeten fluorierten Molekülen identifiziert wurde. Für alle modifizierten Membranen (unabhängig von dem Hydrophobierungsmittel) mit Porengrößen kleiner oder gleich 400 nm, wurde ein Flüssigkeitseindringdruck (LEP) über 2,5 bar gemessen, welcher jedoch eine starke Abhängigkeit von den Eigenschaften der Testlösung zeigt. Während symmetrisch aufgebaute keramische Membranen modifiziert mit einem fluorierten Hydrophobierungsmittel die Behandlung mit heißer, salzhaltiger Lösung über 96 Stunden standhielten, zeigten diese deutlich geringere Permeatflüsse in der VMD als asymmetrisch strukturierte keramische Membranen. Der Stofftransport von asymmetrischen keramischen Membranen war in der VMD höher ausgeprägt als in der DCMD. Der Stofftransport von asymmetrischen keramischen Membranen wird in der VMD vorwiegend von den Supporteigenschaften beeinflusst, während der Strofftransport in der DCMD erheblich von den Eigenschaften der trennaktiven Membranschicht (z. B. die Porengröße) bestimmt wird. Ein in der Literatur beschriebenes VMD-Modell in Bezug vorhandener Defizite durch Korrekturfaktoren erfolgreich erweitert und zur Berechnung des Strofftransportes für asymmetrische TiO2 Membranen angewandt. TiO2 und Al2O3 Membranen wurden in der VMD erfolgreich zur Behandlung hochkonzentrierter Salzlösungen (synthetische und reale Lösungen) verwendet. TiO2 Membranen zeigten höhere Permeateflüsse als Al2O3 Membranen in der DCMD und der VMD. Das begründet sich insbesondere bedingt durch die bessere Moderierung von Temperaturpolarisationseffekten aufgrund der geringen Wärmeleitfähigkeit von TiO2 Membranen. Beispielsweise wurden bei der Behandlung einer hochkonzentrierte NaCl-Lösung (350 g NaCl pro kg H2O) mit einer TiO2 Membran (Finale Porengröße: 100 nm) in der VMD hervorragende Salzrückhalte von über 99,9 % und Permeatflüsse von bis zu 35 kg/( m² h) erreicht. Die Stofftransportraten der modifizierten keramischen Membranen in der VMD sind im Vergleich zu den Permeatflüssen von Polymermembranen (Literaturwerte) unter ähnlichen Testbedingungen wettbewerbsfähig. Es wurde gezeigt, dass die geringe Energieeffizienz von keramischen Membranen weiterhin die größte Herausforderung für deren kommerzielle Nutzung in MD-Prozessen darstellt und diese der Fokus der Membranoptimierung darstellen sollte

From phosphinoboranes to mercaptopyridines : a journey into the reactivity of not so frustrated Lewis pairs

La catalyse est une des pierres d’assise de la chimie moderne. Elle permet de faire des transformations difficiles d’une manière efficace et sélective, rendant possible des voies de synthèse plus courtes qui permettent ainsi à l’industrie chimique des économies de temps et d’argent. Par conséquent, le développement de la catalyse est d’une grande importance. Dans les dernières décennies, la plupart des efforts ont été orientés vers l’utilisation de métaux de transition de la seconde et troisième rangée, une approche couronnée de succès. Cependant, la maturité de ce sous-domaine et les améliorations des méthodes de caractérisation et de modélisation ont encouragé les chercheurs académiques à explorer le potentiel d’autres éléments du tableau périodique pour la catalyse. Cette thèse explore la catalyse sans métal, ou comme nous aimons l’appeler, la chimie organométallique sans métal. Elle présente des avancées dans le domaine des paires de Lewis frustrées (PLFs), qui utilisent des molécules comportant des fonctions acide de Lewis et base de Lewis pour rendre possible des transformations qui ne le seraient pas en utilisant seulement l’une ou l’autre des fonctions. Le focus particulier du travail est de comprendre et d’exploiter la chimie des PLFs. Par conséquent, nous ne nous sommes pas limités à seulement une sous-classe de PLFs ni à une seule transformation chimique. Les sujets contenus dans la thèse sont diversifiés et incluent la réduction du CO2, la fonctionnalisation de liens C-H, la chimie des liens B-B, la chimie des liens B-S ainsi que des discussions plus fondamentales sur le futur de la catalyse utilisant les PLFs.Catalysis is one of the cornerstones of modern chemistry. It allows difficult transformations to take place in an efficient and selective manner, making possible the design of shorter synthetic pathways and saving the chemical industry time and money. Thus, the improvement of catalysis is of great importance. In the past decades, most efforts have been oriented toward the use of second and third row transition metals, an approach that has been very successful. However, the maturity of that subfield and the improvement of characterization and modelization techniques have been leading academic researchers in exploring catalysis with other elements of the periodic table. This thesis explores metal-free catalysis, or as we like to call it metal-free organometallic chemistry. It presents advances in frustrated Lewis pair (FLP) chemistry, which uses molecules containing Lewis basic and Lewis acidic functions to access transformations that would not be possible using only one or the other. The focus of the work is mostly on understanding and exploiting FLP chemistry. Thus, we did not limit ourselves to some sub-class of FLP nor to only one transformation. The subjects contained in the thesis are quite diverse and include CO2 reduction, C-H bond functionalization, B-B bond chemistry, B-S bond chemistry as well as more fundamental discussions on future FLP catalysis development

Selective Chemistry to Improve Organic Chemistry and Drug Discovery

University of Minnesota Ph.D. dissertation. August 2018. Major: Medicinal Chemistry. Advisor: Courtney Aldrich. 1 computer file (PDF); xxi, 641 pages.Selectivity in both organic and medicinal chemistries represents the pinnacle of these scientific fields. The ability to do exactly as one intends in the most efficient manner facilitates a limited negative impact technology may impart in the environments in which it acts. As such, during these dissertation studies, I have endeavored to design new selective reactions to enable the most streamlined synthesis of organic molecules that may impart a variety of functions while simultaneously working to rationally create new drug substances that limit side effects in the patient, while also protecting the molecule from the harsh environment of an organism. To briefly summarize the material contained herein, the first chapter comprises of the technologies I have developed for better enabled organic synthesis. These reactions can improve green chemistry initiatives to limit the negative impact on the environment, only possible because of the highly selective nature of these reactions. I expect these technologies should enable chemists who design molecules with many intended purposes, although they were designed with the intent of empowering medicinal chemists. The second chapter of this work covers highly collaborative efforts to design improved chemotherapeutics in an effort to eradicate Tuberculosis, the leading cause of infectious disease mortality worldwide. These molecules range from selective pro-drugs that are released at the site of action by utilizing a selective targeting pro-moiety to rationally designed agents to take advantage of biological mechanism knowledge. These molecules can potentially be drugs in themselves while they certainly inform future endeavors to make new drug materials to combat Tuberculosis