Academic literature on the topic 'Sintesi de metanol'

Pengembangan produksi DME (dimetil eter) sebagai energi alternatif yang ramah lingkungan sudah banyak dilakukan di negara-negara lain seperti Jerman, Belanda, Australia, Jepang, China dan Taiwan. Indonesia masih mengimpor DME untuk memenuhi seluruh kebutuhan industri dalam negeri, karena itu perlu didirikan pabrik pembuatan DME. Proses pembuatan DME secara indirect melibatkan sintesis metanol, dehidrasi metanol, purifikasi DME hingga purifikasi metanol untuk di recylce. Optimasi proses purifikasi DME dilakukan dengan mendapatkan kinerja pengendalian yang optimum pada proses purifikasi DME hingga purifikasi metanol. Unit-unit yang ada pada proses purifikasi DME ialah unit distilasi DME, unit cooler dan unit storage tank, sedangkan pada proses purifikasi metanol terdapat unit distilasi metanol, unit cooler dan unit pompa. Proses purifikasi DME dan Metanol ini mengandalkan unit distilasi yang memiliki suhu operasi hingga 190oC dan tekanan hingga 1950 kPa. Sistem pengendalian yang dipilih untuk proses ini ialah jenis pengendali Proportional Integral (PI) karena dapat menangani hampir setiap situasi pengendalian proses di dalam skala industri. Penelitian ini menggunakan pemodelan penyetelan pengendali Ziegler Nichols dan Lopez, lalu dibandingkan nilai parameter kinerja pengendalinya yaitu Offset, Rise Time, Time of First Peak, Settling Time, Periode osilasi, Decay Ratio, Overshoot, Deviasi maksimum, Integral Absolute Error (IAE) dan Integral Square Error (ISE) dari kedua jenis penyetelan tersebut. Hasil penelitian ini dapat digunakan untuk penentuan variabel input dan output yang optimum pada proses purifikasi DME dan Metanol yang dapat diterapkan pada pabrik DME.

Sintesis titanium oksida (TiO2) telah dilakukan pada penelitian ini menggunakan metode sol gel. Titanium isopropoksida (TTIP) digunakan sebagai prekursor. Pelarut yang digunakan antara lain metanol, etanol, dan 2-propanol. Sintesis TiO 2 juga memakai polietilen glikol (PEG) sebagai molekul template. Variasi yang digunakan adalah variasi pelarut dan berat molekul template. Hasil analisa XRD untuk variasi pelarut menunjukkan bahwa pelarut metanol menghasilkan ukuran kristal yang lebih kecil dibandingkan dengan etanol dan 2-propanol yaitu sebesar 137,50 nm.Kata Kunci: Pelarut, Polietilen glikol, Sol Gel, TiO2.

Telah dilakukan sintesis katalis Zn/Zeolit alam dengan metode impregnasi menggunakan larutan [ZN(NH3)4(NO3)2] dan zeolit alam dari Cipatujah, Jawa Barat dengan variasi tempeatur reduksi. Sintesis katalis Zn/Zeolit alam dengan temperatur oksidasi 350oC dan temperatur reduksi 400oC mempunyai karakter katalis yang paling optimal, mempunyai keasaman total 4,07 mmol NH3/g dan kandungan Zn 0,81%. Dibandingkan dengan katalis H+-zeolit alam dengan reaksi thermal, energi aktivasi (Ea) konversi metanol menjadi hidrokarbon menggunakan katalis Zn/zeolit alam mempunyai harga relatif kecil. Analitis konversi metanol menjadi hidrokarbon dilakukan dengan kromatografi gas.

Telah dilakukan penelitian tentang pengaruh pelarut pada rendemen sintesis senyawa kompleks bis-asetilasetonatotembaga(II). Tujuan penelitian ini adalah untuk mensintesis senyawa kompleks bis-asetilasetonatotembaga(II) dengan pelarut metanol, aseton, dan kloroform, menentukan pelarut terbaik untuk sintesis dan membandingkan rendemen hasil sintesis pada pelarut yang berbeda. Senyawa kompleks bis-[Cu(acac)2] disintesis dengan mencampurkan CuSO4.5H2O dan ligan asetilaseton dalam pelarut metanol, aseton dan kloroform. Hasil yang diperoleh berupa endapan berwarna biru. Hasil analisis UV-Vis menunjukkan bahwa senyawa bis-[Cu(acac)2] dalam beberapa pelarut mempunyai panjang gelombang 654-657 nm. Hasil analisis FTIR menunjukkan adanya atom O dari ligan asetilaseton terkoordinasi dengan atom pusat Cu(II) pada bilangan gelombang 455,2 cm-1. Rendemen senyawa kompleks paling banyak diperoleh pada senyawa kompleks bis-[Cu(acac)2] dalam pelarut aseton yaitu sebesar 2,50 gram.

Telah dilakukan penelitian tentang pengaruh pelarut pada rendemen sintesis senyawa kompleks bis-asetilasetonatokobalt (II). Penelitian ini bertujuan untuk memperoleh senyawa kompleks bis-asetilasetonatokobalt (II) dengan pelarut yang bervariasi, membandingkan hasil karakterisasi senyawa kompleks yang terbentuk, dan menentukan pelarut yang baik dalam sintesis senyawa kompleks tersebut. Metode yang digunakan pada penelitian ini adalah metode Powlikowski. Tahapan penelitian ini meliputi sintesis senyawa kompleks dengan variasi pelarut dan karakterisasi dengan analisis menggunakan UV-Vis, AAS dan FTIR. Sintesis senyawa kompleks dilakukan dengan mereaksikan Co(NO3)2.6H2O dengan ligan asetilaseton dengan perbandingan 1:3 mol dalam berbagai pelarut (metanol, aseton, dan kloroform). Endapan yang diperoleh dianalisis menggunakan FTIR dan Uv-Vis sedangkan filtrat yang peroleh dianalisis dengan AAS. Sintesis senyawa kompleks dari ion logam Co dengan asetilaseton dengan variasi pelarut menghasilkan senyawa kompleks bis-asetilasetonatokobalt (II). Spektra FTIR menunjukan ikatan koordinasi antara atom pusat Co dan ligan asetilasetonat (Co-O) pada bilangan gelombang 424,34 cm-1. Hasil analisis UV-Vis menunjukkan senyawa kompleks mempunyai panjang gelombang maksimum yang sama yaitu pada 491 nm dengan energi 10Dq sebesar 243,335 kJ/mol. Rendemen senyawa kompleks dalam pelarut metanol sebesar 0,53 gram, aseton 1,37 gram dan kloroform 1,08 gram. Pelarut yang baik dalam sintesis ini adalah pelarut aseton.

Graphene merupakan material 2 dimensional yang mempunyai sifat unik salah satunya memiliki luas permukaan sangat tinggi (~2630 m2g-1) yang dapat mengadsorbsi gas target. Tidak seperti sensor gas lainnya, sensor graphene dapat dioperasikan di bawah kondisi sekitar dan pada suhu kamar. Interaksi antar gas metanol dengan graphene menghasilkan perubahan pada sifak konduktifitas dan resistensinya yang membuat graphene menjadi elemen sensor yang baik. Struktur dan sifat elektronik graphene tergantung pada proses sintesisnya. Metode Hummers dan microwave irradiation dipilih karena biaya produksi efektif, menghasilkan graphene dengan sensitifitas tinggi terhadap target gas. Dari ketiga variasi pembuatan graphene dari Graphene Oxide (GO) melalui microwave irradiation yaitu 0,1 g-450 Watt, 0,1 g-630 Watt dan 0,02 g-450 Watt menunjukkan sensitifitas paling tinggi pada variasi graphene 0,02 g-450 Watt. Hal ini mengindikasikan semakin kecil massa GO dan semakin tinggi daya microwave membentuk sifat graphene yang lebih optimal terlebih untuk sensor gas.

Senyawa koordinasi adalah senyawa yang terbentuk karena adanya ikatan antara ligan dengan ion pusat. Penelitian ini dilakukan dengan tujuan memperoleh senyawa kompleks Zn(II)-8-Hidroksikuinolin dengan pelarut asetonitril, metanol dan etanol serta menentukan karakteristik dari produk yang diperoleh. Metode penelitian ini dilakukan dengan mencampurkan larutan ZnCl2 dan larutan 8-Hidroksikuinolin disertai pengadukan dengan menggunakan magnetik stirrer selama 60 menit. Karakterisasi uji dilakukan dengan menggunakan UV-Vis, FTIR dan AAS. Dari sintesis kompleks Zn(II)-8-Hidroksikuinolin dalam pelarut asetonitril, metanol dan etanol, diperoleh rendemen sebesar 73,07 % ; 63,46% ; dan 48,67%, dengan panjang gelombang maksimum berturut-turut sebesar 319,5 nm ; 313 nm ; and 320 nm. Adanya ikatan Zn-N teridentifikasi pada pita serapan pada kisaran 439,79 cm-1 hingga 513,09 cm-1, sedangkan ikatan Zn-O teridentifikasi pada pita serapan pada kisaran 542,98 cm-1 hingga 543,95 cm-1. Dapat disimpulkan bahwa Zn(II) terkoordinasi dengan ligan 8-Hidroksikuinolin membentuk endapan senyawa kompleks Zn(II)-8-Hidroksikuinolin berwarna kuning.

Pembuatan biodiesel dari minyak kelapa sawit dilakukan melalui metode transesterifikasi menggunakan metanol dan menghasilkan hasil samping berupa gliserol yang dapat mengurangi nilai ekonominya. Oleh karena itu, metode transesterifikasi digantikan menjadi metode interesterifikasi dengan mengubah metanol menjadi metil asetat yang menghasilkan hasil samping berupa triasetin. Penelitian ini bertujuan untuk mengetahui kondisi optimal dari variasi konsentrasi katalis NaOH 1,0%, 1,5%, dan 2,0% dan lama waktu sintesis selama 3 jam dan 6 jam terhadap karakteristik biodiesel dengan metode interesterifikasi. Rendemen biodiesel yang dihasilkan berkisar antara 40,87% - 59,50% dengan karakteristik viskositas 4,807 - 4,848 mm2/s, nilai densitas 0,869 - 0,870 g/ml, dan kandungan FAME 81,79% - 84,84%. Hasil penelitian telah sesuai dengan Standar Nasional Indonesia (SNI) Biodiesel, kecuali FAME. Namun, kandungan FAME pada penelitian ini masih mendekati standar. Hasil analisis sidik ragam menunjukkan adanya perlakuan variasi konsentrasi katalis NaOH dan waktu sintesis yang tidak memiliki pengaruh terhadap rendemen, viskositas, densitas, dan kandungan FAME. Dengan demikian dalam menentukan perlakuan yang lebih baik dapat dikaitkan dengan keekonomisan (seperti waktu proses dan biaya). Perlakuan yang lebih baik adalah pada katalis NaOH 1% dan waktu sintesis selama 3 jam, dimana memiliki rendemen 49,16% dengan karakteristik yang memiliki nilai viskositas 4,813 mm2/s, densitas 0,869 g/ml, dan kandungan FAME 83,40%.

Biji alpukat merupakan limbah pangan yang mengandung minyak nabati. Salah satu pemanfaatan minyak nabati adalah biodiesel. Biodiesel dapat digunakan sebagai bahan bakar alternatif yang ramah lingkungan dikarenakan dapat menurunkan emisi jika dibandingkan dengan minyak diesel. Penelitian ini bertujuan untuk memanfaatkan biji alpukat sebagai bahan baku sintesis biodiesel serta karakterisasinya. Sintesis biodiesel dilakukan melalui reaksi esterifikasi minyak biji alpukat menggunakan pelarut metanol dengan perbandingan massa 1:20 disertai dengan penambahan katalis asam dan melalui reaksi transesterifikasi menggunakan pelarut metanol dengan perbandingan massa 1:6 dan disertai katalis basa, dengan konsentrasi katalis yang digunakan sebesar 2,5% dari bobot minyak. Karakterisasi dilakukan dengan analisis spektrofotometer FTIR yang menunjukkan adanya gugus fungsi ester yang merupakan karakteristik dari biodiesel hasil sintesis dengan melihat adanya ikatan C-O pada pada bilangan gelombang 1244,09 cm-1 dan ikatan C=O pada bilangan gelombang 1737,86 cm-1. Selain itu dilakukan juga analisis gas chromatography (GC) yang menunjukkan kandungan minyak terbanyak yang berhasil terekstrak dari biji alpukat, yaitu senyawa metil ester oleat dengan waktu retensi 20,618 menit. Pada tahap akhir dilakukan pengujian spesifikasi terhadap biodiesel yang dihasilkan berdasarkan Standar Nasional Indonesia (SNI) 04-7182-2006 yang telah ditetapkan, yang menunjukkan angka asam sebesar 0,4 mg NaOH/g, massa jenis sebesar 679,335 kg/m3 dan viskositas kinematik sebesar 4,980 mm2/s pada 40ºC, dan warna nyala api biru kemerahan dan tidak berasap yang lebih baik dibandingkan dengan solar.

Telah dilakukan penelitian sintesis emulsifier ester sukrosa asam lemak (FACE) dari minyak jagung menggunakan Na2CO3. Sintesis FACE dilakukan dengan metode refluks menggunakan metil ester asam lemak (FAME), sukrosa, pelarut metanol, dan katalis Na2CO3 dengan variasi rasio berat katalis terhadap FAME 1,5%, 3%, 4,5%, 6%, dan 7,5%. Kondisi optimum FACE terjadi pada FACE dengan rasio berat Na2CO3 6% dengan derajat transesterifikasi 1,169 dan waktu pecah emulsi 347,47 detik. Hasil analisis GC-MS pada FAME menunjukkan komposisi senyawa mayor penyusun FAME adalah metil ester asam linoleat, metil ester asam oleat, metil ester asam palmitat, dan metil ester asam stearat. Banyaknya katalis mempengaruhi FACE yang dihasilkan.

El CO2 en la atmósfera aumenta a raíz del empleo de combustibles fósiles. La hidrogenación de CO2 ofrece una ruta única para transformar esta molécula en productos químicos o combustibles como el metanol. El uso de alta presión en el ratio CO2:H2 = 1:>3 permite incrementar la cinética de la reacción, alcanzando así la conversión termodinámica como ya se ha reportado. No obstante, el mayor inconveniente del mencionado proceso es el tratamiento del hidrógeno sin reaccionar. Por ello, se evaluaron las ventajas de realizar la reacción a alta presión en condiciones estequiométricas (CO2:H2=1:3) examinando diferentes parámetros. Una vez optimizados, se alcanzó el límite termodinámico y se obtuvo un valor de conversión de CO2 cercano al 90% con una selectividad para metanol > 95% a 280 °C y 442 bar empleando Cu/ZnO/AlO3 como catalizador. Al minimizar las limitaciones de transferencia de masa, el rendimiento fue de 15.6 gMeOH gcat-1 h-1, aproximadamente un orden de magnitud mayor comparado con los de bibliografía. Adicionalmente, los mecanismos de la reacción en condiciones de alta presión se estudiaron mediante análisis espacial de la fase gas por CG y espectroscopía Raman. El estudio mostró que el CO2 se convierte directamente a metanol a baja temperatura, mientras que a alta temperatura la reacción water-gas shift es predominante generando CO, que produce metanol posteriormente. estructura core-shell. Este material mostró un recubrimiento uniforme del ZnO en los cores de Cu, y el espesor del shell se optimizó. Dichos nanomateriales mostraron alta actividad catalítica, útil para comprender la interacción entre Cu y Zn y en concreto, las exclusivas fases de Zn formadas durante la reacción a alta presión mediante operando DRX a alta presión.<br>Carbon dioxide concentration in the atmosphere is continuously increasing as a consequence of the combustion of fossil fuels. CO2 hydrogenation offers a unique path to transform the chemically stable CO2 to useful chemicals or fuel such as methanol. High-pressure advantages under over-stoichiometric CO2:H2 ratio (1:>3) has been reported previously by drastically increasing the reaction kinetics and even reaching the thermodynamic conversion. However, the major drawback of such processes is the treatment of unreacted hydrogen. Reflecting this background, the advantages of the high pressure approach in stoichiometric CO2:H2 (1:3) ratio were critically evaluated by examining different reaction and process parameters. When optimized, we could reach the thermodynamic limit and obtained about 90% CO2 conversion with >95% methanol selectivity at 280 °C and 442 bar using Cu/ZnO/Al2O3 catalyst. When the mass transfer limitation was minimized, an outstanding weight time yield was achieved with 15.6 gMeOH gcat-1 h-1, which is about one order of magnitude higher than the state-of-the-art values. Furthermore, the reaction mechanisms under high-pressure reaction conditions were studied by spatially-resolved gas phase analysis through the axial direction of the catalytic reactor by GC and Raman spectroscopy.

Orientador: Mario de Jesus Mendes<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Campinas<br>Made available in DSpace on 2018-07-16T17:55:15Z (GMT). No. of bitstreams: 1 Nascimento_AlvimarFerreirado_M.pdf: 2565624 bytes, checksum: 179d503d584f787cb2b7d36381ea59aa (MD5) Previous issue date: 1987<br>Resumo: O interesse no estudo da reação de síntese do metanol baseia-se em dois aspectos principais: Por um lado, a obtenção do metanol, um importante produto da indústria química e um combustível automotivo potencial. No Brasil, esta segunda utilização do metanol oferece grandes possibilidades, pelas reservas de madeira, matéria prima básica da produção do monóxido de carbono e hidrogênio, reagentes básicos da reação de síntese. Por outro lado, o desafio que representa ao entendimento dos fenômenos catalíticos. A produção do metanol via hidrogenação do monóxido ou dióxido de carbono é, pela termodinâmica, francamente desfavorecida. A síntese só é possível quando é utilizado um catalisador altamente seletivo o conhecimento profundo do mecanismo da reação poderá tornar ainda mais viável, economicamente, a produção do metanol, quando a pressão de síntese, atualmente na faixa de 50 a 100atm, puder ser reduzida a níveis de 5 a 10atm. Neste trabalho é apresentada uma discussão dos catalisadores e do mecanismo de reação de síntese do metanol, é descrita uma instalação utilizada para coleta de dados cinéticos, e são apresentados os resultados experimentais obtidos<br>Abstract: The interest in studying the methanol synthesis reaction is based on two principal aspects: On the one hand, the obtainment of methanol, an important product of the chemical industry and a potential automotive fuel. In Brazil, this second methanol usefulness offers large possibilities, owing to its huge reservoirs of wood, a raw material for the sybthesis gas production. On the other hand, the challenge that it represents to the understanding of the catalytic phenomena. The methanol production through hydrogenation of carbon monoxide or of carbon dioxide is outspokenly deseteemed by thermodynamics. The synthesis is only possible when a highly selective catalyst is utilized. The knowledge about the reaction mechanism may however have a high economic value, if it makes it possible to reduce the synthesis pressure, today at a value from 50 to 100atm, to the level of 5 to 10atm. In this work we first discuss the catalysts and the reaction mechanism of the methanol synthesis; then we describe the installation utilized to collect kinetic data, and finally we present the experimental results<br>Mestrado<br>Mestre em Engenharia Química

Orientador: Gustavo Paim Valença<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica<br>Made available in DSpace on 2018-07-27T17:48:45Z (GMT). No. of bitstreams: 1 Goncalves_EmersonSarmento_M.pdf: 6577943 bytes, checksum: 7f0584919df305f521c9d43f2ec3654a (MD5) Previous issue date: 2001<br>Resumo: A partir do gás de síntese (que constitui uma mistura gasosa de óxidos de carbono e hidrogênio), pode-se obter hidrocarbonetos, álcoois e aldeídos. Estes podem ser obtidos também através da via petroquímica. Portanto, a produção desses compostos a partir do gás de síntese constituem vias alternativas que podem ser exploradas em função de aspectos econômicos existentes no mercado. Este fato tem motivado um interesse renovado pelo aprofundamento do conhecimento acerca da reação de Fischer- Tropsch. Além disso, é possível transformar gás de síntese resultante de transformações ocorridas com o metano, em produtos com maior valor agregado. O problema proposto é a análise sistemática de possíveis catalisadores eficazes no aumento da especificidade de um produto desejado. No caso particular desse trabalho, a atenção é direcionada a três produtos: metano, metanol e etileno. Na literatura, são apresentados diversos catalisadores para essas reações. Por exemplo, Ni, Pd, FelW são catalisadores seletivos para a reação de metanação. Fe, Co e Ru, são catalisadores seletivos para a formação de hidrocarbonetos e álcoois com mais de 2 átomos de carbono. Cu, Pt e Pd são catalisadores seletivos para a formação de metanol e poliálcoois. O fato de a reação de Fischer-Tropsch apresentar grande diversidade de produtos é coerente com a variedade de mecanismos propostos. Cada um deles é capaz de justificar satisfatoriamente o espectro de produtos formados, mas a evidência usada para sustentar as teorias individuais é usualmente indireta e pode, algumas vezes, ser interpretada em mais de uma rota. Segundo descrições usuais, há três principais categorias, no tocante ao que acontece inicialmente com o monóxido de carbono: na primeira, ele quimissorve dissociativamente e é sucessivamente hidrogenado; na segunda, o CO adsorve associativamente e é sucessivamente hidrogenado; na terceira, a molécula não dissocia e se insere entre ligações metal-hidrogênio ou metal-carbono. Neste trabalho a metodologia de análise das etapas elementares utiliza o formalismo baseado na conservação da ordem de ligação e em Potenciais de Morse (BOC-MP), desenvolvido por E. Shustorovich. Este formalismo aplicado a outras reações resultou em valores para a entalpia de adsorção e energia de ativação de etapas elementares dentro de 10 kJ morl dos valores experimentais. O método estima as entalpias de adsorção qas espécies e a energia de ativação das etapas envolvidas em cada rota de reação. Em reações tais como a oxidação do CO, hidrogenólise do etano, hidrogenação do eteno e decomposição catalítica da hidrazina, o método apresentou bastante sucesso, com erros inferiores a 15% com relação aos valores obtidos experimentalmente. O trabalho consiste em identificar as espécies envolvidas na reação e equaclOnar as entalpias de adsorção de cada espécie e a energia de ativação de cada etapa elementar da reação em função das entalpias de adsorção dos átomos de carbono, oxigênio e hidrogênio apenas. Em seguida, procede-se com análise dos resultados de energia de ativação versus entalpia de adsorção de carbono e de oxigênio. A análise é baseada primeiramente em comparações duas a duas de etapas que apresentem valores de fatores pré-exponenciais com a mesma ordem de grandeza. Busca-se com essa análise as faixas em que cada etapa é predominante, isto é superficies que favorecem uma ou outra etapa. Subseqüentemente, procede-se com o agrupamento das diversas etapas de cada conjunto de etapas, ou rotas de reação, visando determinar regiões ou domínios dos mínimos locais de energia de ativação. Identifica-se dessa maneira as diversas faixas onde cada uma das diversas reações podem ocorrer, de tal maneira a serem identificados os catalisadores ótimos para as diversas reações estudadas. Desta etapa, parte-se para a comparação com resultados experimentais apresentados na literatura procurando-se mostrar onde cada catalisador está localizado. Dependendo dos resultados encontrados será possível sugerir novos domínios ( catalisadores) para outras reações decorrentes dos mesmos reagentes. Uma conseqüência da análise proposta é a sugestão de desenvolvimento de novos catalisadores para reações com gás de síntese e do projeto de catalisadores eficazes na transformação de gás de síntese em produtos com maior valor agregado. Os resultados mostram que, num certo sentido, a forma como o CO quimissorve sobre a superficie metálica é decisiva para o tipo de produto final. A seqüência de etapas elementares que leva à síntese de metanol concorre principalmente com a seqüência de metanação. Desde a primeira até a última etapa, catalisadores de cobre estarão bastante associados à manutenção da ligação CO e sva hidrogenação, bem como das espécies subseqüentes, até o metanol. Platina e paládio apresentam também certa tendência para síntese de metanol. Ferro e níquel estão associados à quebra da ligação CO e são catalisadores de síntese de Fischer- Tropsch e metanação, respectivamente<br>Abstract: The Fischer- Tropsch synthsis is an altemative route for the production of hydrocarbons, alcohol and aldehydes, chemicals that may also be obtained in a petrochemical route. The final decision on the use of either route depends on economic aspects of local markets. Nonetheless, there has been a renewed interest in the Fischer- Tropsch reaction, particularly as petroleum becomes scarce in many parts of the world and methane-derived syngas may be obtained ITom renewable sources. The present work proposes a detailed analysis of different sequence of elementary steps for the Fischer- Tropsch reaction that may take place on different surfaces, in the search of an increase in product selectivity. As a case study, attention is directed to three products: methane, methanol and ethylene. For example, Ni, Pd, Fe/W are selective catalysts for the methanation reaction while Fe, Co or Ru are selective catalysts for the production of hydrocarbons and alcohols with more than two carbon atoms. Cu, Pt e Pd are selective catalysts for the methanol synthesis and for the formation of polyalcohols. In order to explain the wide variety of products obtained in the Fischer- Tropsch reaction, different sequence of steps are proposed. Each of them is in agreement with the formation of a product, but the evidence used to support individual theories is usually indirect and may be ambiguous. In any event, it is well accepted that CO is involved in three possible steps, namely, dissociative chemisorption with subsequent hydrogenation; non-dissociative chemisorption with subsequent hydrogenation; or insertion ofthe undissociated molecule into either a metal-hydrogen or a metal-carbon bonds. In this work the analysis of elementary steps is based on the bond order conservation and Morse Potentials method (BOC-MP), developed by E. Shustorovich. The method estimates the adsorption enthalpies of the species and the activation energy of the each elementary step. The BOC-MP formalism has been used for reactions such as the CO oxidation, hydrogenolysis of ethane, hydrogenation of ethylene and catalytic decomposition of hydrazine, with errors in activation energy less than 15% of experimental values. First, the possible species involved in all steps were identified and the equations to calculate the adsorption enthalpy of each species as a function of the adsorption enthalpies of O, C and H (Qo, Qc and QH) were written. Then, the elementary steps of each reaction and the equation for the activation energy of each step were written as a function of the adsorption enthalpies of C, O and H. The activation energy was then analysed as a function ofthe adsorption enthalpy ofC and O. Related steps with the same pre-exponential factors are then compared in the search of regions or domains where each step is favoured. Subsequently, alI steps were grouped together and domains of Qo and Qc where local minimum of activation energy exist can be identified. These domains correspond to different catalysts used for each product. There is a good agreement between the surfaces suggested by the present method and real catalysts. Thus, the proposed methodology is able to identify possible surfaces to be used as prospective catalysts for a given reaction or modifications ofthe surface structure ofworking catalysts. The results show that, in a sense, the manner as CO chemissorb over the metalic surface is decisive to the type of final product. The sequence of elementary steps which drive to the methanol synthesis compete principalIy with the sequence of reaction of methanation. From first untillast step, catalysts of copper is very associated at mantainance of bond CO and its hidrogenation, welI as of subsequent species, until methanol. Platinum e paladium also show toa a tendency to methanol synthesis. lron and nickel are associated to break the CO bond and are catalysts ofFischer- Tropsch synthesis and methanation, respectively<br>Mestrado<br>Desenvolvimento de Processos Químicos<br>Mestre em Engenharia Química

Arylamines are a class of compounds whose importance in chemical and pharmaceutical fields has been consolidated over time. With the increasing use of these Active Pharmaceutical Ingredients (APIs), many synthesis techniques have been created since the 1990s to obtain these products. The most well-known arylamines synthesis techniques to date are all catalyzed metal reactions. Chronologically, the synthesis changed from the use of cross coupling reactions such as Buchwald-Hartwig or Chan-Evans-Lam, to oxidative reactions in the presence of noble metals. The aim of this project was to outline a new synthetic strategy to obtain arylamine substrates, thus avoiding the use of catalysts made by noble metals. The reaction was discovered accidentally following an experimental evidence, since a by-product different was obtained. The main purpose of the thesis was to optimize the following reaction to obtain a high yield and in the meantime try to understand how the particular structure of substrate could be fundamental to allow the aromatization of the molecule.

In questo lavoro di tesi è stata investigata la possibilità di utilizzare i metallo-esacianoferrati, in particolare il nichel-esacianoferrato (NiHCF) ed indio-esacianoferrato (InHCF), come setacci ionici, per la rimozione selettiva di cationi di terre rare. In particolare si è voluto studiare l’influenza di cationi diversi dal K+ e la loro capacità di intercalare nel reticolo cristallino dell’InHCF e NiHCF. Grazie alla proprietà di scambio ionico, gli esacianoferrati sono in grado di fungere da setacci ionici. I cationi (ad esempio K+) intercalati nella struttura possono essere scambiati con cationi più pesanti, fino al raggiungimento di un certo limite, dopo il quale un ulteriore scambio è sfavorito dalle interazioni repulsive tra gli ioni carichi positivamente. I campioni di indio-esacianoferrato (InHCF) e nichel-esacianoferrato (NiHCF) sono stati sintetizzati sia per via elettrochimica che per via chimica e sono stati caratterizzati utilizzando tecniche elettrochimiche (in particolare la voltammetria ciclica), IR, XRF, TGA e TEM. In questo studio è stato dimostrato come l’InHCF ed il NiHCF riescano a scambiare in modo selettivo cationi di terre rare e possano quindi essere considerati ottimi candidati nella sintesi e produzione di setacci molecolari.

Il metil metacrilato (MMA) è un importante intermedio chimico principalmente utilizzato come monomero per la sintesi del poli metil metacrilato (PMMA). Il processo più moderno e sostenibile per la sintesi di MMA è il processo Alpha, che consiste nell'idrossi-metilazione del metil propionato (MP) con formaldeide (FAL) seguita dalla disidratazione dell’intermedio ottenuto. Il MP, attualmente prodotto tramite carbonilazione dell’etilene in presenza di metanolo (MeOH), può essere sintetizzato anche da glicerolo (coprodotto dalla produzione del biodiesel), un’economica molecola piattaforma di origine rinnovabile. Il principale svantaggio del processo Alpha consiste nell’utilizzo di FAL pura, notoriamente cancerogena. Questo inconveniente può essere superato promuovendo la formazione di FAL mediante deidrogenazione in-situ del MeOH, nello stesso reattore in cui avviene la reazione tra MP e FAL. Per questo motivo, la sintesi di MMA a partire da MP e MeOH è stata studiata in un reattore in continuo operante in fase vapore, investigando inizialmente due ossidi metallici come catalizzatori eterogenei: ossido di magnesio (MgO) e ossido di gallio (Ga2O3). Quest’ultimo è risultato molto più selettivo grazie alla moderata basicità ed al forte potere redox in grado di favorire la deidrogenazione del MeOH, tuttavia ha mostrato problemi di disattivazione. Nel tentativo di modulare le caratteristiche acido-base e redox dei catalizzatori, sono stati sintetizzati due ossidi misti con rapporto atomico Mg/Ga uguale a 10 e 20. L’introduzione di Ga3+ nella struttura aumenta l’attività catalitica per la deidrogenazione di MeOH e riduce la basicità totale rendendo il catalizzatore meno attivo per le reazioni parassite di chetonizzazione e riduzione tramite meccanismo di H-transfer. L’influenza dei principali parametri operativi (T, rapporto MeOH/MP, time factor) sul decorso della reazione è stato investigato approfonditamente ed è stato possibile proporre un complesso schema di reazione.

La messa a punto di processi in grado di utilizzare le biomasse lignocellulosiche per la produzione di molecole piattaforma, utilizzabili per la sintesi di intermedi per la chimica fine, l’industria polimerica ed i combustibili, è attualmente un argomento di ricerca di grande interesse. Tra le molecole più studiate vi è la furfurale (FU), che si può ottenere mediante disidratazione dei monosaccaridi pentosi contenuti nei materiali lignocellulosici. Il prodotto di riduzione della furfurale, l’alcol furfurilico (FAL), è commercialmente interessante perché trova applicazione nell’industria polimerica e viene utilizzato come intermedio nella produzione di lisina, vitamina C, lubrificanti e agenti dispersanti. In letteratura sono riportati numerosi processi che permettono di ottenere questo prodotto, utilizzando la riduzione catalitica con H2 in pressione, che però presentano problemi di selettività, costo, sostenibilità e tossicità del catalizzatore utilizzato. La possibilità di effettuare la riduzione selettiva della furfurale senza fare ricorso all’idrogeno molecolare, utilizzando un processo di H-transfer e catalizzatori eterogenei a base di ossidi misti, risulta quindi di estremo interesse perché permette di eliminare i suddetti problemi. Lo scopo di questa tesi è stato quello di ottimizzare il processo, confrontando catalizzatori basici, quali MgO, CaO e SrO ottenuti tramite calcinazione a diverse temperature dei rispettivi precursori. In particolare, è stata valutata l’influenza che la temperatura di calcinazione, il tempo e la temperatura di reazione hanno sulla reattività e la stabilità dei sistemi catalitici sintetizzati. La caratterizzazione dei catalizzatori tramite diffrazione ai raggi X (XRD), analisi termiche (TGA, DTA) e misure di area superficiale con tecnica BET ha permesso di correlare le proprietà chimico-fisiche dei materiali con la loro attività catalitica.

Le biomasse sono attualmente la più promettente alternativa ai combustibili fossili per la produzione di sostanze chimiche e fuels. A causa di problematiche di natura etica la ricerca oggi si sta muovendo verso l'uso delle biomasse che sfruttano terreni non coltivabili e materie prime non commestibili, quali la lignocellulosa. Attualmente sono state identificate diverse molecole piattaforma derivanti da biomasse lignocellulosiche. Tra queste ha suscitato grande interesse la 2-furaldeide o furfurale (FU). Tale molecola può essere ottenuta mediante disidratazione di monosaccaridi pentosi e possiede elevate potenzialità; è infatti considerata un intermedio chiave per la sintesi di un’ampia varietà di combustibili alternativi come il metilfurano (MFU) e prodotti ad elevato valore aggiunto per l’industria polimerica e la chimica fine come l’alcol furfurilico (FAL). In letteratura tali prodotti vengono principalmente ottenuti in processi condotti in fase liquida mediante l’utilizzo di catalizzatori eterogenei a base di metalli nobili come: Ni-Co-Ru-Pd, Pt/C o Pt/Al2O3, NiMoB/γ-Al2O3, in presenza di idrogeno molecolare come agente riducente. La riduzione del gruppo carbonilico mediante l’utilizzo di alcoli come fonti di idrogeno e catalizzatori a base di metalli non nobili tramite la reazione di Meerwein–Ponndorf–Verley (MPV), rappresenta un approccio alternativo che limita il consumo di H2 e permette di utilizzare bio-alcoli come donatori di idrogeno. Lo scopo di questo lavoro di tesi è stato quello di mettere a punto un processo continuo, in fase gas, di riduzione della FU a FAL e MFU, utilizzando metanolo come fonte di idrogeno tramite un meccanismo di H-transfer. In dettaglio il lavoro svolto può essere così riassunto: Sintesi dei sistemi catalitici MgO e Mg/Fe/O e loro caratterizzazione mediante analisi XRD, BET, TGA/DTA, spettroscopia RAMAN. Studio dell’attività catalitica dei catalizzatori preparati nella reazione di riduzione in fase gas di FU a FAL e MFU utilizzando metanolo come fonte di idrogeno.

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas. Programa de Pós-Graduação em Química.<br>Made available in DSpace on 2012-10-22T18:16:43Z (GMT). No. of bitstreams: 1 230074.pdf: 2278286 bytes, checksum: 566304e98f55e0e1a2b3ede6927d6cf0 (MD5)<br>A natureza aprendeu a utilizar propriedades especiais dos metais para realizar uma ampla variedade de funções associadas aos sistemas vivos. Metaloproteínas que realizam funções catalíticas são denominadas de metaloenzimas, constituindo então uma classe especial de compostos bioinorgânicos. Neste contexto, as fosfatases ácidas púrpuras (PAPs), metaloenzimas pertencentes à classe das hidrolases, catalisam a hidrólise de ésteres e anidridos do ácido fosfórico em uma faixa de pH de 4 a 7. A característica cor púrpura dessa subclasse de fosfatases ácidas é resultado de um de transferência de carga do tipo ligante metal (OTyr?FeIII) em torno de 560 nm. Os complexos modelos tiveram papel fundamental no entendimento das propriedades físicos-químicas das PAPs, antes da resolução das estruturas cristalinas das mesmas. Assim, através do estudo estrutural, espectroscópico e de testes de reatividade, busca-se esclarecer o mecanismo através do qual ocorre o processo catalítico em complexos modelos para que estes possam auxiliar na elucidação do mecanismo pelo qual a enzima nativa atua. Neste trabalho foram sintetizados e caracterizados por análise elementar de CHN; medidas de condutividade; espectroscopias no infravermelho, eletrônica e Mössbauer; eletroquímica e titulação potenciométrica dois novos complexos de ferro(III)cobalto(II) e gálio(III)cobalto(II) empregando-se o ligante H2BPBPMP76, já descrito na literatura. Os complexos 1 - [FeIIICoII(BPBPMP)(µ-OAc)2]ClO4 . 0,25 H2O e 2 - [GaIIICoII(BPBPMP)(µ-OAc)2]ClO4 . H2O tiveram suas estruturas cristalinas resolvidas apresentando-se isoestruturais entre si, sendo ainda apontados como modelos estruturais para as PAPs metalo-substituídas, pois mimetizam os resíduos de aminoácidos presentes no sítio ativo das PAPs e simulam a distância intermetálica presente nas mesmas. Os estudos realizados frente à hidrólise do substrato modelo 2,4-bisdinitrofenilfosfato (2,4-BDNPP) resultaram em fatores de aceleração de 19,2 e 21,2 mil vezes, espectivamente, em relação à reação não catalisada sendo o complexo 2 (GaIIICoII) o que se apresentou mais efetivo na conversão do substrato a produtos. Estudos inibitórios (por íons OAc- e HPO4 2-) para a reação do 2,4-BDNPP mostraram que os íons acetato à baixas concentrações não influenciam significativamente o processo catalítico, porém, íons fosfato devido a sua alta constante de associação podem comprometer a catálise mesmo em concentrações reduzidas. A partir dos dados estruturais, espectroscópicos, eletroquímicos, cinéticos e de titulação potenciométrica foi possível propor um ciclo catalítico para a hidrólise do 2,4-BDNPP, mediada pelos complexos 1 e 2 compatível com outros já descritos na literatura.

Orientador: Regina Buffon<br>Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica<br>Made available in DSpace on 2018-08-03T15:58:55Z (GMT). No. of bitstreams: 1 Campos_JoseDanielRibeirode_D.pdf: 4250480 bytes, checksum: b3118a291b7ace284d7cc6991666bf45 (MD5) Previous issue date: 2003<br>Doutorado

Additive manufacturing (AM) has emerged as the most versatile process in the manufacturing sector. The advantages of AM such as applicability in a wide range of industries, ease of manufacturing, and reduction in waste production have increased its demand over the past decades. Out of the many techniques under AM, direct metal laser sintering (DMLS) is one of the most efficient manufacturing techniques that uses a high-powered laser beam to sinter metal powders in a layer-by-layer fashion. With the current usage of computational modeling, the prediction of microstructure evolution and other thermo-mechanical properties of different materials have been of great advantage to researchers. Along with a detailed classification of AM techniques, this chapter focuses on the use of continuum, phase field, and atomistic modeling under the DMLS process. The results show that multiscale modeling can be advantageous in gaining deeper insight into various phenomena like diffusion and sintering.

The IV and V group transition metals borides, carbides, and nitrides are widely known as ultra-high temperature ceramics (UHTCs), owing to their high melting point above 2500°C. These ceramics possess outstanding physical and engineering properties, such as high hardness and strength, low electrical resistivity and good chemical inertness which make them suitable structural materials for applications under high heat fluxes. Potential applications include aerospace manufacturing; for example sharp leading edge parts on hypersonic atmospheric re-entry vehicles, rocket nozzles, and scramjet components, where operating temperatures can exceed 3000°C. The extremely high melting point and the low self-diffusion coefficient make these ceramics very difficult to sinter to full density: temperatures above 2000°C and the application of pressure are necessary conditions. However these processing parameters lead to coarse microstructures, with mean grain size of the order of 20 µm and trapped porosity, all features which prevent the achievement of the full potential of the thermo-mechanical properties of UHTCs. Several activities have been performed in order to decrease the severity of the processing conditions of UHTCs introducing sintering additives, such as metals, nitrides, carbides or silicides. In general the addition of such secondary phases does decrease the sintering temperature, but some additives have some drawbacks, especially during use at high temperature, owing to their softening and the following loss of integrity of the material. In this chapter, composites based on borides and carbides of Zr, Hf and Ta were produced with addition of MoSi2 or TaSi2. These silicides were selected as sintering aids owing to their high melting point (&gt;2100°C), their ductility above 1000°C and their capability to increase the oxidation resistance. The microstructure of fully dense hot pressed UHTCs containing 15 vol% of MoSi2 or TaSi2, was characterized by x-ray diffraction, scanning, and transmission electron microscopy. Based on microstructural features detected by TEM, thermodynamical calculations, and the available phase diagrams, a densification mechanism for these composites is proposed. The mechanical properties, namely hardness, fracture toughness, Young’s modulus and flexural strength at room and high temperature, were measured and compared to the properties of other ultra-high temperature ceramics produced with other sintering additives. Further, the microstructural findings were used to furnish possible explanations for the excellent high temperature performances of these composites.

In MIM, fine metal powders are mixed with a binder and injected into molds, similar to plastic injection molding. After molding, the binder is removed from the part, and the compact is sintered to almost full density. The obstacle to sinter bonding a MIM part to a conventional (solid) substrate lies in the sinter shrinkage of the MIM part, which can be up to 20%, meaning that the MIM part shrinks during sintering, while the conventional substrate maintains its dimensions. This behavior would typically inhibit bonding and/or cause cracking and deformation of the MIM part. A structure of micro features molded onto the surface of the MIM part allows for shrinkage while bonding to the substrate. The micro features tolerate certain plastic deformation to permit the shrinkage without causing cracks after the initial bonds are established. In a first series of tests, bond strengths of up to 80% of that of resistance welds have been achieved. This paper describes how the authors developed their proposed method of sinter bonding and how they accomplished effective sinter bonds between MIM parts and solid substrates.

The bending fatigue properties of powder metal (P/M) gears as a function of density were investigated. SAE-AISI 4600 based steel gears were manufactured using various powdered metal processes. The processes used were press and sinter, double press and double sinter, surface densify, and powder forge (P/F). The resulting gears were then subjected to single tooth bending fatigue testing and compared with 4600 based wrought gears. It was found that the density of the P/M part had a significant influence on the bending fatigue properties. When compared to the wrought material, a P/M gear of equivalent density was found to have similar bending fatigue properties.

Pastes consisting of micron-sized particles of a low melting point metal (i.e. Sn) and a high melting point metal (e.g. Ag, Cu) embedded in organic binder have been developed to attach silicon or wideband gap semiconductor devices to metallic or ceramic substrates for power electronic applications requiring operation at high temperatures. The attachment is made by a pressure-less, low temperature transient liquid phase sintering (LT-TLPS) process in air. Process time and temperature, along with binder type and amount are adjusted to minimize the formation of voids in the joints. Test samples consisting of copper dice on copper substrates joined by these LT-TLPS sinter pastes have been manufactured for shear testing. A shear fixture for high-temperature testing has been designed, and shear tests have been performed at temperatures of 25°C, 125°C, 250°C, 400°C, and 600°C. The influence of process time, process temperature, and the ratio of low-melting point metal (Sn) to high-melting point metal (Ag, Cu) on the shear strength at each temperature has been assessed. It has been shown that the shear strength of TLPS sinter joints remains high up to the melting point of the dominant intermetallic phase of the joint. The joints show no softening below the melting point of these phases. AgSn sinter joints show only limited change in shear strength up to 400°C. CuSn joints exhibit high shear strength up to 600°C for high copper ratios. While process times of 5–15 minutes are sufficient to drive the sintering reaction to near completion, extended curing improves the strength of the sinter joints even more. Failure analyses for joints of different compositions have been conducted along with cross-sectioning of sintered but non-sheared specimens to correlate reliability to microstructure.

Recuperators can greatly improve the fuel efficiency of gas turbine engines, but they are normally heavy, bulky, expensive, and susceptible to high temperature creep, oxidation, and thermal stresses. One way to alleviate these problems is to make them from ceramic materials rather than metal alloys. However, fabricating these complex structures is a challenge. The technique investigated in this study was to laser-cut thin sheets of tapecast material into complex patterns, laminate them together into stacks, and sinter at high temperature. The layers were laminated together by applying heat, pressure, chemical solvents, and varying combinations of the three. This paper presents the results of all fabrication tests, describes the method used to successfully laminate and sinter one 33-layer stack, and summarizes other possible fabrication techniques for future investigation that would facilitate lamination the process.

The metal-supported solid oxide fuel cell (SOFC) was studied. Hydrocarbon fueled operation was used to make SOFC system. Different operating characteristics for metal-supported SOFC are used than for conventional ones. Metal-supported SOFC was successfully fabricated by a high temperature sinter-joining method and the cathode was in-situ sintered. Synthetic gas, which is compounded as the diesel reformate gas composition and low hydrocarbons was completely removed by the diesel reformer. Metal-supported SOFC with synthetic gas was operated and evaluated and its characteristics analyzed. The performance of hydrogen operation shows 0.4 W·cm−2 of maximum power density. The maximum power density of the synthetic gas operation decreased to 0.22 W·cm−2 and to 0.11 W·cm−2 after 10 hours operation, respectively. Degradation occurred because a large steam quantity made an oxidation atmosphere at high temperature, causing the metallic part damage.

Abstract This paper presents a study on the surface durability of sintered metal gears. Gear blanks made of partially prealloyed steel powders were compacted and sintered under various processes, then they were hobbed and case-hardened. Some gears were surface-rolled under various amount of rolling before case-hardening. The contact fatigue tests were carried out for these gears using the power-circulating-type gear test machine. The effects of sintering processes and rolling on the surface durability and wear of sintered metal gears were determined. Furthermore, the surface durability of the above-mentioned sintered metal gears was compared with that of the wrought steel gears. The density of sintered metal gears increases by adopting a double-press-double-sinter (2P2S) process as the sintering process. The surface density of the sintered metal gears tends to increase with rolling for the case of gears with relatively lower density. The surface durability of sintered metal gears tends to increase with an increasing surface density. The surface durability of sintered metal gears may approach that of the wrought steel gears by adopting the appropriate sintering and rolling processes.