As zeólitas apresentam significativa importância econômica para a indústria química e petroquímica. Desde o início do seu uso (1954) como catalisador e/ou peneira molecular vem mostrando crescente aplicação no refino do petróleo, com ênfase no craqueamento. A zeólita ZSM-22, embora eficiente para determinadas reações, ainda não é objeto de muitos estudos quando comparada com zeólitas em uso comercial. Uma etapa crucial para a viabilidade comercial da ZSM-22 é o processo de síntese que, em geral, utiliza direcionadores de estrutura e tempos de cristalização longos, tornando o material oneroso. Este trabalho pretende destacar a importância do desenvolvimento de rotas para obtenção da ZSM-22, visto seu potencial de aplicação. Para tanto, se desenvolve uma fundamentação teórica a partir de patentes e artigos acessíveis nas bases de dados do INPI, Espacenet, WIPO, DERWENT e USPTO e Periódicos Capes. Como resultado desta análise, foram estabelecidos as tendências e problemas para obtenção da ZSM-22.Palavras chave: Zeólita. ZSM-22. Sementes.
The hydrothermal synthesis of MCM-22 zeolite was investigated in reaction systems with different proportions of sodium and potassium cations. The potassium content R, defined as the molar ratio between potassium and the total inorganic cations amounts in the synthesis mixture, varied from 0 to 0.9, keeping constant the cationic concentration and the alkalinity of the system. The materials were characterized by X-ray diffraction (XRD), N2 adsorption/desorption and scanning electron microscopy (SEM). The K+ ions favored the formation of MCM-22 when 45% of sodium was replaced by potassium, reducing the time required to synthesize the MCM-22(P) precursor and producing more crystalline samples. Furthermore, the relative amounts of Na+ and K+ ions remarkably affected the morphology and particle size of the samples. The use of higher potassium contents (R = 0.68 – 0.9) hindered the crystallization of MCM-22 zeolite. Thus, the use of reaction mixtures with adequate proportions of Na+ and K+ can be an effective strategy to produce highly crystalline samples in shorter times, reducing the cost of synthesis of such zeolite
RESUMODevido a sua alta estabilidade térmica e acidez, a zeólita mordenita é utilizada como adsorvente na separação de gases ou misturas líquidas, e como catalisador nos processos de hidrocraqueamento, hidroisomerização, alquilação, reforma catalítica, desparafinação e síntese de dimetilaminas. A busca por novas propriedades das zeólitas conhecidas, a redução do tempo de cristalização e dos custos dos reagentes, torna o processo de síntese uma etapa crucial para sua viabilidade comercial. Este trabalho teve como finalidade destacar a importância do desenvolvimento de rotas para obtenção da mordenita, visto seu potencial de aplicação na indústria petroquímica. Para tanto, se desenvolveu uma fundamentação teórica a partir de patentes e artigos acessíveis nas bases de dados do INPI, Espacenet, WIPO, USPTO e Periódicos Capes. Como resultados destas análises foram estabelecidas as tendências para obtenção da zeólita mordenita.Palavras chave: Zeólita. Síntese. Mordenita. Sementes. ABSTRACTDue to its high thermal stability and acidity mordenite zeolite is used as adsorbent for the separation of gas or liquid mixtures, and as catalyst in processes of hydrocracking, hydroisomerization, alkylation, catalytic reforming, dewaxing and dimethylamines synthesis. The search for new properties of the known zeolites, the reduction of the crystallization time and cost of reagents, synthesis makes the process a critical step for its commercial viability. This work aimed to highlight the importance of developing routes to achieving mordenite, as their application potential in the petrochemical industry. Therefore, it has developed a theoretical framework from patents and accessible articles in the databases of the INPI, Espacenet, WIPO, USPTO and Portal periodicos Capes. As a result of these analyzes were established trends to obtain the mordenite zeolite.
The synthesis of ZSM-22 zeolite has been extensively studied due to its properties of form selectivity, acidity and hydrothermal stability, which is applied in important reactions in the areas of petroleum refining and petrochemicals. In view of this, the present work studied different approaches of synthesis of ZSM-22 using: 1-diaminohexane as a structure directing agent, (ii) methanol and seed crystals, (iii) aging of the synthesis gel with addition of polymer, surfactant and silane and (iv) starch, calcium carbonate and silanized silica with subsequent desilication. Thus, the effects of these methodologies on the textural properties, acidity and catalytic activity of the zeolites obtained were evaluated. The samples were characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption, scanning electron microscopy (SEM), ammonia desorption at programmed temperature (NH3-TPD) and thermal analysis (TG/DTG). The catalytic activity and selectivity of the catalysts were evaluated in the model catalytic cracking reaction of n-heptane at 650 °C for 180 min. The synthesis route using methanol and seed crystals allowed obtaining ZSM-22 in 3 h of crystallization, drastically reducing the synthesis time compared to other methodologies. Despite this, the use of 1-diaminohexane led to the obtaining of zeolite with textural properties, acidity and catalytic activity superior to the other samples. The generation of mesoporosity was obtained through the use of silanized silica and subsequent desilication, leading to greater catalytic stability and less deactivation by coke. All catalysts showed similar selectivity to the formation of compounds in the range C2 to C4.
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