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Sustainability is an urgent need to secure the progress of our civilization and to reach it is getting more and more into common conscious. From a chemists viewpoint, this means the customary practices of the last centuries have to be overcome, chemicals and chemical processes must be designed safe and environmentally friendly without long term consequences while at the same time conserving resources. A main part within this is the reduction of toxic waste, often originated in solvents. To accomplish this, new paths have to be discovered. One possible path is mechanochemistry, which describes chemical reactions initiated by mechanical forces like milling balls and vessels in a ball mill. In this environment solubility is not required and thus turns the use of solvents obsolete. However, in mechanochemical catalytic reactions for instance catalyst complexes with ligands are used, that originally ensured solubility in the former reaction medium. Since no solubility is required in this solvent free reaction environment, the complexes can be simplified to salts or further to pure metal powder catalysts. Complexes, salts and powders alike are difficult to recycle from the reaction mixture, thwarting the aim of sustainability. A concept to overcome this drawback is direct mechanocatalysis that uses milling materials themselves made of the catalytic metal, likewise accounting for the catalyst and the energy input. The aim of the thesis on hand was to expand the concept towards new direct mechanocatalytic reactions and gain insights beyond the mere phenomenology. In detail, the palladium catalysed Suzuki coupling as well as the copper catalysed Ullmann reaction/coupling, and Glaser coupling were investigated.

Die am häufigsten für die Zerkleinerung des Zementklinkers eingesetzte Kugelmühle stellt eine relativ einfache Maschine dar, in der sehr komplizierte dynamische Wechselwirkungen herrschen. Die direkte Messung der Beanspruchungsintensitäten ist heutzutage immer noch eine schwierige Aufgabe. In der vorliegenden Arbeit sind die Spektren der Beanspruchungsgrößen sowie einige spezifische integrale Größen mit der Methode der diskreten Elemente (DEM) untersucht worden. Eine besondere Aufgabe bestand in der Ermittlung der Parameter des viskoelastischen Kontaktmodells und der den Zementklinker charakterisierenden mechanischen Größen. Die reale Abbildung der Stoßvorgänge wurde anhand vereinfachter Modelle der Messprüfstände validiert. Mit den ermittelten Parametern sind numerische Untersuchungen durchgeführt worden, mit denen ihre Auswirkung auf die Zielgrößen bestimmt wurde. In Hinsicht auf eine mögliche konstruktive Weiterentwicklung sind Simulationen mit festgelegten betrieblichen und zu variierenden konstruktiven Parametern durchgeführt worden.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / This paper describes a study of reaction parameters in a ball mill in the synthesis of 1H-pyrazole acid catalyzed. The studied parameters were: amount of reactants, frequency, reaction time, amount of catalyst, number of milling balls, different catalysts, diameter and material of the milling balls. Another study was conducted to study the mechanism of solid-solid reaction involved in the cyclocondensation between enaminones and hydrazine hydrochloride acid catalyzed. These mixtures were studied by thermal analysis (TGA and DSC), where eight enaminones were evaluated and four eutectic mixtures were identified. / Este trabalho descreve o estudo de parâmetros reacionais em moinho de bolas na síntese de 1H-pirazol catalisada por ácido. Os parâmetros estudados foram: quantidade de reagentes, frequência, tempo, quantidade de catalisador, número de esferas, diferentes catalisadores, diâmetro e material das esferas de moagem. Outro trabalho realizado foi o estudo do mecanismo de reação sólido-sólido envolvido na reação de ciclocondensação entre enaminonas e cloridrato de hidrazina catalisada por ácido. Estas misturas foram estudadas através de análises térmicas (TGA e DSC), sendo que de oito enaminonas avaliadas, 4 misturas eutéticas binárias foram identificadas.

Submitted by Kilvya Braga (kilvyabraga@hotmail.com) on 2018-04-23T14:56:43Z No. of bitstreams: 1 WLADMIR JOSÉ GOMES FLORÊNCIO - DISSERTAÇÃO (PPGEM) 2015.pdf: 4800490 bytes, checksum: f2bc5fbc0347cf5ae8fcd0816a8c0697 (MD5) / Made available in DSpace on 2018-04-23T14:56:43Z (GMT). No. of bitstreams: 1 WLADMIR JOSÉ GOMES FLORÊNCIO - DISSERTAÇÃO (PPGEM) 2015.pdf: 4800490 bytes, checksum: f2bc5fbc0347cf5ae8fcd0816a8c0697 (MD5) Previous issue date: 2015-06-19 / CNPq / Estudou-se a dinâmica do processo de moagem, analisando o movimento da carga de um moinho de bolas em escala de laboratório, a partir de ensaios realizados e a partir da simulação utilizando-se o Método dos Elementos Discretos (MED). Uma adaptação do sistema de transmissão mecânico, do moinho, foi feita com o objetivo de variar a velocidade de rotação entre: 57%, 60%, 65%, 70%, 75% e 80% da velocidade crítica (NC). Ensaios de peneiramento, sem moagem e com moagem, variando o percentual de velocidade crítica do moinho, foram realizados. Com isso estabeleceu-se um ponto de corte de referência na peneira de malha (+30#), cujo objetivo foi determinar a eficiência da moagem a partir da verificação da distribuição granulométrica obtida. O comportamento da dinâmica do processo de moagem foi observado utilizando-se um sistema de filmagem em que foram analisados os deslocamentos e comparados com os obtidos pela simulação computacional em 2D, realizada no software de simulação DEMpack®. Foi desenvolvida uma metodologia com o apoio da simulação computacional da moagem, utilizando-se a posição dos corpos moedores e as características da massa, cujo objetivo foi o de determinar a potência necessária ao movimento do moinho de bolas. Verificou-se ser possível realizar a calibração do modelo de simulação a partir da comparação das imagens obtidas pela filmagem do experimento. O coeficiente de atrito influenciou o comportamento da dinâmica do processo: obteve-se melhores resultados quando se utilizou um coeficiente de atrito mais baixo para simular o comportamento dos corpos moedores e um coeficiente de atrito mais alto para simular o comportamento da carga. / It was studied the dynamics of the grinding process, analyzing the movement of the load a ball mill on a laboratory scale, from tests carried out and from the simulation using the Discrete Elements Method (MED). An adaptation of mechanical transmission system of the mill was taken in order to vary the speed of rotation between: 57%, 60%, 65%, 70%, 75% and 80% of the critical speed (NC). Screening tests without crushing and grinding, varying the percentage of critical mill speed, were performed. With that it was established a reference cutoff point in the mesh sieve (+ 30 #), whose objective was to determine the grinding efficiency from checking the particle size distribution obtained. The dynamic behavior of the milling process was observed using a recording system in which the offsets were analyzed and compared with those obtained by computer simulation of 2D held in DEMpack® simulation software. A methodology with the help of computer simulation of milling was developed, using the position of the grinding media and mass characteristics whose goal was to determine the power required to move the ball mill. It was found to be possible to perform the calibration of the simulation model based on the comparison of images obtained by shooting the experiment. The friction coefficient influence the dynamic behavior of the process: better results are obtained when using a low coefficient of friction to simulate the behavior of the grinding bodies and a higher coefficient of friction to simulate the load behavior.

The objective of this study was to improve the operation of the classical semiautogenous and ball milling circuit also known as the SABC circuit. In order to achieve this goal, the challenges around this circuit were identified as the formation of critical sized material in a SAG mill. The size class considered for the critical sized material also known as pebbles was -100+23 mm. The attainable region (AR) method was used as an optimisation technique for the generated results using a computer simulation programme. MODSIM® demo version 3.6.22 is ore processing simulator that was used. The research was divided into two sections, the first being the variation of feed flow rate ranging from 50 – 150 tph and ore feed size ranging between 100 and 600 mm. The second section compared the variation of the operating parameters of the SAG mill, which were mill filling, ball filling, ball size and mill speed. The AR technique graphically presented the results which indicated the best operating conditions to minimise pebble formation. The effects of mill filling on a SAG mill indicate that a higher filling produces lower pebbles. Lower pebble generation also was observed at a higher ball filling. The influence of ball size indicated that the larger ball size was more effective in the reduction of pebbles. For mill speed the media displayed two common mode operations namely cascading at a low speed of 65% and cataracting at higher speed of 75%. The higher speed generated the least pebbles. / College of Engineering, Science and Technology / M. Tech. (Chemical Engineering)

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Made available in DSpace on 2017-07-21T20:42:35Z (GMT). No. of bitstreams: 1 rodrigoric.pdf: 9183178 bytes, checksum: 1d5fba078a589cbc1810eea245d1e019 (MD5) Previous issue date: 2006-10-31 / Mechanical alloying is a powder processing technique involving cold welding, fracturing mechanisms and rewelding of powder particles in a ball mill. The present work applied this technique with the purpose of processing titanium, niobium and tin alloys, through planetary ball mill and attritor mill. The atomic percentages of these elements were varied in six differents ways. The niobium hydrate was used on production of some alloys in study, with the purpose to observe the effects during the milling and on the alloys obtained after sintering. Differences between processing in planetary ball mill and attritor mill, as well the cold welding influences on the kinetic parameters of milling process were approached. The use of niobium hydrate result in a decrease of powders average crystallite size, and an increase of micro hardness of sintered alloys. This work obtained beta titanium alloys and alpha-beta titanium alloys in namometric sizes. The average crystallite size, for milled powders, was 7,6 nm. / Mecano-síntese é uma técnica de processamento em pó que envolve a soldagem a frio, mecanismos de fratura e a resoldagem das partículas de pós, em moinhos de bolas. O presente trabalho utilizou esta técnica com o propósito de processar ligas de titânio, nióbio e estanho, através de moinhos de bolas planetário e de atrito. As porcentagens atômicas destes elementos foram variadas de seis maneiras diferentes. O hidreto de nióbio foi utilizado na produção de algumas ligas em estudo, com o propósito de se observar os efeitos durante a moagem e na liga obtida após a sinterização. Diferenças entre o processamento em moinho de bolas planetário e o moinho de atrito, assim como as influências da soldagem a frio nos parâmetros cinéticos do processo de moagem, foram abordadas. O uso do hidreto de nióbio resultou na diminuição do tamanho médio de cristalito dos pós, e em um acréscimo na microdureza das ligas sinterizadas. Neste trabalho foram obtidas ligas de titânio beta e de titânio alfa-beta, em tamanhos nanométricos. O tamanho médio do cristalito, para os pós moídos, foi de 7,6 nm.