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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Hydrothermal synthesis of hierarchical ZSM-5 with different Si/Al ratio and their evaluation as catalysts in the catalytic cracking of hexane

Nqakala, Loyiso Clemence January 2021 (has links)
>Magister Scientiae - MSc / Ethylene and propylene are greatly used for their importance as feedstocks for producing useful materials. Due to rise in prices and the demand of ethylene and propylene, the need to increase the selective production of these light olefins is necessary. To achieve this, zeolites, specifically ZSM-5 has been used to investigate catalytic cracking of several types of hydrocarbons for the production of these light olefins. This study focuses on developing hierarchical macro and/or mesoporous ZSM-5 zeolites with variable Si/Al ratios. The synthesized materials were then evaluated on their performance via catalytic cracking of hexane, dodecane and tyre derived oil [TDO] to produce light olefins, particularly ethylene and propylene.
2

Light Olefins Cracking by ZSM-5 Prepared from Oxidized Disulfide Oil Refinery Waste

Al Rebh, Mohammad 07 1900 (has links)
Saudi Aramco is investigating the potential use of oxidized disulfide oil (ODSO), a refinery waste, as a solvent to replace water in zeolite preparation for the implication in industrial processes such as Fluidized Catalytic Cracking (FCC) aiming to increase propylene production. Utilizing ODSO helps Saudi Aramco reduces its processing costs, creates a value for this solvent and reduces the zeolite synthesis cost. One major concern is the effect ODSO may have on the catalytic performance of the prepared zeolites. This study investigates the catalytic cracking of 1-hexene and 2-methyl-2-butene (2M2B) at various WHSV and temperatures over ZSM-5 catalysts prepared from gels with SiO$_2$/Al$_2$O$_3$ ratios (SAR) of 50 and 25 and various ODSO/water substitutions. Six ODSO-based ZSM-5 catalysts were prepared and characterized in terms of acidity, morphology, and textural properties. The impact of catalyst composition and properties on conversion and selectivity is examined and compared to commercial ZSM-5 catalysts with similar SAR (CBV2314 and CBV5524G). At 477 h$^{-1}$ WHSV, ODSO-based catalysts achieved 80% 1-hexene conversion with 53-60% propylene selectivity, outperforming commercial catalysts (52%). However, 2M2B cracking exhibits slower reaction rates and more oligomerization cracking, resulting in lower conversion (46-61%) and propylene selectivity (22-29%). Notably, MAR- 2-3 (30% ODSO, 50 SAR gel) shows the best performance among the ODSO catalysts in terms of stability and selectivity, with results comparable to the commercial catalysts. We noticed, on the other hand, that ODSO-based catalysts possess larger crystals and higher acid site density compared to the commercial catalysts leading, generally, to a decreased stability. These findings enhance understanding of waste-based zeolites in catalytic cracking processes and guide the development of improved ODSO-based catalysts for petrochemical applications.
3

I-Hexene dimerisation over a solid phosphoric acid catalyst

Schwarzer, Renier Bernhard 28 June 2012 (has links)
Solid phosphoric acid is a catalyst used for the upgrading of light olefins into fuels. To delve into the mechanism of olefin dimerisation over the catalyst, the oligomerisation of 1- hexene was investigated over a wide range of operating conditions. The reaction progression of 1-hexene dimerisation over solid phosphoric acid was interpreted by means of kinetic experiments for both a linear hexene (1-hexene) and a branched hexene (2,3-dimethylbutene). The reaction rate for both reagents was described by using an elementary kinetic model. From the experimental data it was shown that the rate of dimerisation of branched hexenes was faster than the rate observed for linear hexene dimerisation. To correlate the two sets of kinetic data, the reaction network was expanded to incorporate skeletal isomerisation of 1-hexene with dimerisation only taking place by the co-dimerisation of linear and branched hexenes and the dimerisation of branched hexenes. The fit of the kinetic equation demonstrated that the reaction rate of 1-hexene is essentially controlled by the rate of skeletal isomerisation. Due to the large activation energy for skeletal isomerisation, low reaction temperatures favoured the co-dimerisation of linear and branched hexenes whereas at higher temperatures, the reaction rate was dominated by the dimerisation of branched hexenes. The product distribution indicated that, because of the fast rates of both cracking and secondary dimerisation (dimerisation of cracked products), the product distribution instantaneously reached a pseudo equilibrium after the dimerisation of hexenes. Therefore the carbon distribution was found to depend only on the reaction temperature, not on the residence time in the reactor. Solid phosphoric acid is a supported liquid phosphoric acid where the condensed state of the acid, e.g. ortho phosphoric acid (H3PO4) and pyro phosphoric acid (H4P2O7), is dependent on the quantity of water present in the reaction mixture. With a decrease in water content, the distribution of acid shifts and the ortho phosphoric acid becomes more condensed (H4P2O7, H5P3O9 etc.), i.e. high water content → low acid strength, low water content → high acid strength. The experiments completed at various degrees of catalyst hydration and free acid loading showed that the rate of reaction over solid phosphoric acid was dependent on the acid strength of the catalyst. The effect of acid strength on the reaction rate was integrated into the rate constants by means of an exponential dependency on acid strength. It was also shown that both the product distribution and the degree of branching remained unaffected by acid strength. The constant product indicates that the rate of cracking is limited by the rate of oligomerisation of hexenes, irrespective of the acid strength of the catalyst. Since the product from the dimerisation of 1-hexene could be used as fuel, the quality of the desired fuel would therefore depend solely on the reaction temperature, not on the hydration of the catalyst. The work performed in this thesis has been published in two peer-review articles: 1. Schwarzer R.B., Du Toit E. and Nicol W. (2008) Kinetic model for the dimerisation of 1-hexene over a solid phosphoric acid catalyst, Applied Catalysis A: General, 340, 119-124. 2. Schwarzer R.B., Du Toit E. and Nicol W. (2009) Solid phosphoric acid catalysts: The effect of free acid composition on selectivity and activity for 1-hexene dimerisation, Applied Catalysis A: General, 369, 83-89. / Thesis (PhD(Eng))--University of Pretoria, 2012. / Chemical Engineering / unrestricted
4

Production of renewable biofuels and chemicals by processing bio-feedstock in conventional petroleum refineries / Nghiên cứu khả năng tích hợp chế biến nguyên liệu sinh khối trong nhà máy lọc dầu để sản xuất nhiên liệu sinh học và hóa phẩm cho hóa dầu

Vu, Xuan Hoan, Nguyen, Sura, Dang, Thanh Tung, Armbruster, Udo, Martin, Andreas 09 December 2015 (has links) (PDF)
The influence of catalyst characteristics, i.e., acidity and porosity on the product distribution in the cracking of triglyceride-rich biomass under fluid catalytic cracking (FCC) conditions is reported. It has found that the degradation degree of triglyceride molecules is strongly dependent on the catalysts’ acidity. The higher density of acid sites enhances the conversion of triglycerides to lighter products such as gaseous products and gasoline-range hydrocarbons. The formation of gasolinerange aromatics and light olefins (propene and ethene) is favored in the medium pore channel of H-ZSM-5. On the other hand, heavier olefins such as gasoline-range and C4 olefins are formed preferentially in the large pore structure of zeolite Y based FCC catalyst (Midas-BSR). With both catalysts, triglyceride molecules are mainly converted to a mixture of hydrocarbons, which can be used as liquid fuels and platform chemicals. Hence, the utilization of the existing FCC units in conventional petroleum refineries for processing of triglyceride based feedstock, in particular waste cooking oil may open the way for production of renewable liquid fuels and chemicals in the near future. / Bài báo trình bày kết quả nghiên cứu khả năng tích hợp sản xuất nhiên liệu sinh học và hóa phẩm từ nguồn nguyên liệu tái tạo sinh khối giầu triglyceride bằng công nghệ cracking xúc tác tấng sôi (FCC) trong nhà máy lọc dầu. Kết quả nghiên cứu cho thấy xúc tác có ảnh hưởng mạnh đến hiệu quả chuyển hóa triglyceride thành hydrocarbon. Tính acid của xúc tác càng mạnh thì độ chuyển hóa càng cao và thu được nhiều sản phẩm nhẹ hơn như xăng và các olefin nhẹ. Xúc tác vi mao quản trung bình như H-ZSM-5 có độ chọn lọc cao với hợp chất vòng thơm thuộc phân đoạn xăng và olefin nhẹ như propylen và ethylen. Với kích thước vi mao quản lớn, xúc tác công nghiệp FCC dựa trên zeolite Y ưu tiên hình thành C4 olefins và các olefin trong phân đoạn xăng. Ở điều kiện phản ứng của quá trình FCC, triglyceride chuyển hóa hiệu quả thành hydrocarbon mà có thể sử dụng làm xăng sinh học cho động cơ và olefin nhẹ làm nguyên liệu cho tổng hợp hóa dầu.
5

PRODUÇÃO DE OLEFINAS LEVES A PARTIR DE ETANOL EM ZSM-5 SINTETIZADA SEM DIRECIONADOR NITROGENADO / LIGHT OLEFINS PRODUCTION FROM ETHANOL IN ZSM-5 SYNTHESIZED WITHOUT NITROGENOUS TEMPLATE

Albiero, Jalusa Konzen 05 March 2015 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The petrochemical industry is currently strongly based on the production of light olefins ethylene and propylene, which are mainly produced by hydrocarbons from oil. Due to the environmental appeal and unstable oil market scenario, alternative routes to the production of these olefins are being developed, meanly regarding the use of alcohol as raw material. In this context, ethanol is highlighted with Ethanol to Olefins Process (ETO), in which there is catalytic conversion via reactions of dehydration, oligomerization, cracking, isomerization, among others. This work aims to obtain ethylene and propylene from ethanol using ZSM-5 zeolite as catalyst in its acid form. The synthesis of this material was performed using non-conventional sources of silicon and aluminum, kaolin and silica extracted from rice husk ash, and in the absence of nitrogenous templates. The use of seeds was employed together with ethanol, which acts as cotemplate of the zeolitic structure, in different quantities, and in different silica/alumina ratios and crystallisation times. The influence of each of these variables was evaluated with the support of a full factorial experimental design on the final characteristics of the synthesized samples, such as relative crystallinity, chemical composition and textural properties. All samples presented the characteristic crystal structure of ZSM-5 as verified by both X-ray diffractograms and infrared spectra. However, samples with small amounts of seed and ethanol added to short periods of crystallization presented lower crystallinities and specific areas in comparison to other samples. On the other hand, the use of high quantities of seed can lead to the formation of quartz when the crystallization time is extended. With the catalytic tests of ethanol conversion into olefins it was possible to evaluate the influence of synthesis variables, the residence time and the concentration of ethanol in feed, proving the importance of all synthesis variables in the distribution of the reaction products The total conversion of ethanol was observed in all tests made, evidencing the high activity of hZSM-5 in the dehydration of ethanol to ethylene, being the propylene yield strongly influenced by the reaction temperature and characteristics of the catalitic material, with a maximum yield of 27% at 500 °C. The HZSM-5 presented high stability under reaction conditions while maintaining the production of ethylene for more than 40 hours of reaction, whereas the coke formation drastically reduces the production of propylene still in the early hours of reaction. / A indústria petroquímica atualmente está fortemente baseada na produção das olefinas leves eteno e propeno, que são principalmente produzidas através de hidrocarbonetos oriundos do petróleo. Em virtude do apelo ambiental e do instável cenário do mercado de petróleo, rotas alternativas para a produção destas olefinas estão sendo desenvolvidas, principalmente no que tange a utilização de álcoois como matéria-prima. Neste contexto, o etanol ganha destaque com o processo Ethanol to Olefins (ETO), no qual se tem conversão catalítica via reações de desidratação, oligomerização, craqueamento, isomerização, entre outras. O presente trabalho tem por objetivo a obtenção de eteno e propeno através de etanol empregando como catalisador a zeólita do tipo ZSM-5 na forma ácida. A síntese deste material foi realizada utilizando fontes não convencionais de silício e alumínio, o caulim e a sílica extraída da cinza da casca de arroz, e na ausência de direcionadores de estrutura nitrogenados. O emprego de sementes foi adotado juntamente com etanol, que atua como codirecionador da estrutura zeolítica, em diferentes quantidades, assim como em diferentes razões sílica/alumina e tempos de cristalização. A influência de cada uma destas variáveis foi avaliada com o auxílio do planejamento experimental fatorial completo nas características finais das amostras sintetizadas, como cristalinidade relativa, composição química e propriedades texturais. Todas as amostras obtidas apresentaram estrutura cristalina característica da ZSM-5, comprovada tanto nos difratogramas de Raios-X como nos espectros de absorção na região do Infravermelho. Entretanto, as amostras com pequenas quantidades de sementes e de etanol somadas a curtos períodos de cristalização apresentaram cristalinidades e áreas específicas reduzidas em relação às demais amostras. Em contrapartida, o emprego de elevadas quantidades de sementes pode levar a formação de quartzo quando o tempo de cristalização é prolongado. Com os testes catalíticos de conversão de etanol em olefinas foi possível avaliar a influência das variáveis de síntese, do tempo de residência e a concentração de etanol na alimentação, comprovando a importância de todas as variáveis de síntese na distribuição dos produtos da reação. A conversão total de etanol foi observada em todos os testes realizados, evidenciando a elevada atividade da HZSM-5 na desidratação de etanol a eteno, sendo o rendimento a propeno fortemente influenciado pela temperatura de reação e características do material catalítico, com máximo rendimento igual a 27% na temperatura de 500°C. A HZSM-5 apresentou elevada estabilidade nas condições de reação, mantendo a produção de eteno por mais de 40 horas de reação, enquanto que a formação de coque reduz drasticamente a produção de propeno ainda nas primeiras horas de reação.
6

Craqueamento de hidrocarbonetos naftênicos sobre zeólitas HZSM-12 modificadas – rendimento e seletividade a olefinas leves

Silva Júnior, José Roberto da 30 September 2015 (has links)
Submitted by Alison Vanceto (alison-vanceto@hotmail.com) on 2016-10-21T11:11:40Z No. of bitstreams: 1 TeseJRSJ.pdf: 5314232 bytes, checksum: 9352e78958e9a2f45a12e9a77f564bdd (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-11-08T18:37:37Z (GMT) No. of bitstreams: 1 TeseJRSJ.pdf: 5314232 bytes, checksum: 9352e78958e9a2f45a12e9a77f564bdd (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-11-08T18:37:44Z (GMT) No. of bitstreams: 1 TeseJRSJ.pdf: 5314232 bytes, checksum: 9352e78958e9a2f45a12e9a77f564bdd (MD5) / Made available in DSpace on 2016-11-08T18:37:52Z (GMT). No. of bitstreams: 1 TeseJRSJ.pdf: 5314232 bytes, checksum: 9352e78958e9a2f45a12e9a77f564bdd (MD5) Previous issue date: 2015-09-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / It was studied the catalytic performance of ZSM-12 zeolites modified by desilication in the cracking of naphthenic hydrocarbons. ZSM-12 zeolites with nominal a SiO2/Al2O3 ratio were synthesized during 96 or 144 h under hydrothermal conditions and the obtained zeolites were treated with NaOH solutions under different conditions. The samples were characterized by thermogravimetric analysis (TA), X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 physisorption, temperature programmed desorption of ammonia (NH3-TPD), 27Al MAS NMR spectroscopy, energy-dispersive X-ray spectroscopy (EDX) and infrared spectroscopy (Py-FTIR). The treatment with NaOH solutions under mild conditions was more effective for the ZSM-12 zeolite synthesized during 96 h. For the HZ12-96-0,2 sample, obtained by treatment at 35 °C with 0.2 mol.L-1 NaOH solution during 15 min, it was verified an increase in the external surface area and the formation of mesopores in the range of 2 to 14 nm. On that zeolite occurred a higher yields to light olefins during the cracking of cyclohexane at 400 °C and also in the cracking of methyl and ethylcyclohexane at 450 °C. This result was mainly related to the higher density of acid sites exhibited by the HZ12-96-0,2 zeolite compared with the parent ZSM-12 one, as consequence of the applied alkaline treatment. It was also verified that the ZSM-12 zeolites modified by more severe alkaline treatment (0.5 or 1.0 mol.L-1 NaOH solution at 80 °C for 30 min) presented significant increase of the external surface area and mesopores volume. The catalytic cracking of cyclohexane, methylcyclohexane and ethylcyclohexane at 500 °C, as well as the physicochemical characteristics of the MZ12-96-0,5 zeolite enhanced the formation of light olefins. The highest yield to light olefins was obtained on that zeolite during the cracking of ethylcyclohexane, which increased 9% when compared with the yield obtained on the not modified HZSM-12 zeolite. The selectivity to light olefins on the studied HZSM-12 zeolites was strongly influenced by presence of a side chain in the naphthenic ring (methyl or ethyl), as well as by the employed cracking operating conditions. / Estudou-se o desempenho de zeólitas ZSM-12 modificadas por dessilicalização no craqueamento de hidrocarbonetos naftênicos. Zeólitas ZSM-12 com razão SiO2/Al2O3 igual a 80 foram sintetizadas em 96 ou 144 h sob condições hidrotérmicas. As zeólitas ZSM-12 obtidas foram modificadas sob diferentes condições de tratamento alcalino com soluções de NaOH e posteriormente caracterizadas por termogravimetria, difratometria de raios X, microscopia eletrônica de varredura, fisissorção de nitrogênio, dessorção de amônia à temperatura programada, ressonância magnética nuclear do 27Al, espectroscopia de energia dispersiva de raios X e espectroscopia na região do infravermelho com adsorção de piridina. O tratamento alcalino, sob condições mais brandas, foi mais efetivo para a zeólita ZSM-12 sintetizada em menor tempo de cristalização (96 h). Para a zeólita HZ12-96-0,2, obtida por tratamento com solução de NaOH 0,2 mol.L-1 a 35 °C por 15 min, verificou-se um aumento na área superficial externa e distribuição de tamanho de mesoporos entre 2 e 14 nm. Nessa zeólita, ocorreu um maior rendimento a olefinas leves no craqueamento de cicloexano a 400 °C e, também, no craqueamento de metil- e etil-cicloexano realizado a 450 °C. Esse resultado foi relacionado, principalmente, com a maior concentração de sítios ácidos na zeólita HZ12- 96-0,2, em relação à zeólita HZSM-12 precursora, como consequência do tratamento alcalino. Verificou-se, também, que as zeólitas ZSM-12 modificadas por tratamento alcalino, sob condições mais severas (solução de NaOH 0,5 ou 1,0 mol.L-1 a 80 °C por 30 min), apresentaram aumento significativo de área superficial externa e volume de mesoporos. O craqueamento de cicloexano, metil- e etil-cicloexano realizado a 500 °C, assim como as características físicas e químicas da zeólita MZ12-96-0,5, favoreceram a formação de olefinas leves. O maior rendimento a olefinas leves ocorreu durante o craqueamento do etil-cicloexano sobre essa zeólita, com aumento desse rendimento em torno de 9% quando comparado ao rendimento obtido sobre a zeólita HZSM-12 não modificada. A seletividade a olefinas leves sobre as zeólitas HZSM-12 preparadas neste estudo sofreu forte influência da presença da cadeia lateral no anel naftênico (metil ou etil), assim como também das condições operacionais de craqueamento empregadas.
7

Propriedades ácidas e texturais de zeólitas ZSM-5 dessilicalizadas ou desaluminizadas – análise do rendimento e seletividade a olefinas leves durante a transformação de cicloexano e metilcicloexano

Darim, Hélio Rubens Abdo 13 March 2015 (has links)
Submitted by Alison Vanceto (alison-vanceto@hotmail.com) on 2017-02-09T10:54:21Z No. of bitstreams: 1 DissHRAD.pdf: 15161052 bytes, checksum: e10c4924acc9cc8afc5ecbec12ee85aa (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-03-20T17:16:45Z (GMT) No. of bitstreams: 1 DissHRAD.pdf: 15161052 bytes, checksum: e10c4924acc9cc8afc5ecbec12ee85aa (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-03-20T17:16:55Z (GMT) No. of bitstreams: 1 DissHRAD.pdf: 15161052 bytes, checksum: e10c4924acc9cc8afc5ecbec12ee85aa (MD5) / Made available in DSpace on 2017-03-20T17:24:11Z (GMT). No. of bitstreams: 1 DissHRAD.pdf: 15161052 bytes, checksum: e10c4924acc9cc8afc5ecbec12ee85aa (MD5) Previous issue date: 2015-03-13 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Nowadays, the Brazilian petroleum is extracted from very deep fields and possesses a high naphthenic hydrocarbons composition, which imposes new challenges to refineries and specially to the catalytic cracking process. In that process, the catalyst must act maximizing the production of the highly demanded gasoline, diesel and light olefins from heavy fractions. Taking into consideration the above discussed context, this work aimed to evaluate the effect of basic or acid treatments applied on ZSM-5 zeolites (Si/Al=12 or 23) in the activity to cyclohexane or methylcyclohexane transformation. XRD and 27Al-NMR showed that the dealuminated zeolites presented an increase in their crystallinity due to the extra-framework aluminum lixiviation. On the other hand, in the desilicated zeolites occurred a decrease in their crystallinity as a consequence of the extra-framework aluminum generation. MEV images do not evidence any morphological change that could have been produced by the acid or basic treatments, however, the desilicated ZSM-5 zeolites treated under harder conditions presented significant textural modifications. As expected, the chemical ICP analyses showed a decrease in the Si/Al ratio in the desilicated zeolites and an increase of that ratio for those dealuminated ones, being the last variation more significative in the external surface of the zeolite crystals, as was evidenced by XPS analyses. Data from NH3-TPD showed that the acid treatment resulted in a higher ratio of strong acid sites, which suffered more deactivation during reaction. N2 fisisorption analyses of the ZSM-5 zeolites, showed that the desilication done at higher temperature was more efficient to mesopore generation. In the cyclohexane and methylcyclohexane transformation, the dealuminated zeolites were less active due to their lower aluminum content, nevertheless were more stable and presented a small increase to light olefins selectivity. The desilicated ZSM-5 zeolites presented higher activity and higher yield to light olefins that were supported by their lower Si/Al ratio and mainly by the presence of mesoporosity that enhanced the reagents and products internal diffusivity. / A produção nacional de petróleo, extraído de jazidas cada vez mais profundas, possui um elevado teor de hidrocarbonetos naftênicos, o que impõe novos desafios às refinarias brasileiras e, em particular, ao processo de craqueamento catalítico. Nesse processo, o catalisador deve maximizar a transformação das frações pesadas em produtos de alta demanda como gasolina, diesel e olefinas leves. Nesse contexto, esta dissertação objetivou avaliar o efeito de tratamentos de lixiviação ácida ou básica em zeólitas ZSM-5 (Si/Al=12 ou 23), na atividade para a transformação de cicloexano ou metilcicloexano. Dados de DRX e 27Al-RMN mostraram que as zeólitas desaluminizadas apresentaram um aumento da sua cristalinidade devido à remoção de átomos de alumínio extra-rede, por outro lado, nas zeólitas dessilicalizadas ocorreu uma redução da cristalinidade devido à geração de alumínio extra rede. As micrografias de MEV não evidenciaram modificação morfológica devido aos tratamentos, entretanto nas amostras dessilicalizadas sob condições mais severas, houve significativa mudança das propriedades texturais. Como esperado, as análises químicas por ICP mostraram uma redução na razão Si/Al para as amostras dessilicalizadas e um aumento dessa razão para as zeólitas desaluminizadas, sendo essa variação mais significativa na superfície externa dos cristais, como mostraram resultados de XPS. As análises de DTP-NH3 mostraram que o tratamento ácido resultou numa maior proporção de sítios ácidos fortes, os quais sofreram maior desativação durante a reação. Dados de fisissorção de N2 das zeólitas mostraram que a dessilicalização em temperatura mais elevada foi mais eficiente na geração de mesoporos. Na transformação do cicloexano e do metilcicloexano, as zeólitas desaluminizadas apresentaram menor conversão como resultado da diminuição do teor de alumínio, entretanto tiveram maior estabilidade e apresentaram um ligeiro aumento na seletividade a olefinas leves. As amostras dessilicalizadas apresentaram maiores conversões e rendimentos a olefinas leves, que se justificaram em função da diminuição da razão Si/Al, mas principalmente, como resultado da presença de mesoporosidade, que melhorou a difusão interna de reagentes e produtos.
8

Production of renewable biofuels and chemicals by processing bio-feedstock in conventional petroleum refineries

Vu, Xuan Hoan, Nguyen, Sura, Dang, Thanh Tung, Armbruster, Udo, Martin, Andreas 09 December 2015 (has links)
The influence of catalyst characteristics, i.e., acidity and porosity on the product distribution in the cracking of triglyceride-rich biomass under fluid catalytic cracking (FCC) conditions is reported. It has found that the degradation degree of triglyceride molecules is strongly dependent on the catalysts’ acidity. The higher density of acid sites enhances the conversion of triglycerides to lighter products such as gaseous products and gasoline-range hydrocarbons. The formation of gasolinerange aromatics and light olefins (propene and ethene) is favored in the medium pore channel of H-ZSM-5. On the other hand, heavier olefins such as gasoline-range and C4 olefins are formed preferentially in the large pore structure of zeolite Y based FCC catalyst (Midas-BSR). With both catalysts, triglyceride molecules are mainly converted to a mixture of hydrocarbons, which can be used as liquid fuels and platform chemicals. Hence, the utilization of the existing FCC units in conventional petroleum refineries for processing of triglyceride based feedstock, in particular waste cooking oil may open the way for production of renewable liquid fuels and chemicals in the near future. / Bài báo trình bày kết quả nghiên cứu khả năng tích hợp sản xuất nhiên liệu sinh học và hóa phẩm từ nguồn nguyên liệu tái tạo sinh khối giầu triglyceride bằng công nghệ cracking xúc tác tấng sôi (FCC) trong nhà máy lọc dầu. Kết quả nghiên cứu cho thấy xúc tác có ảnh hưởng mạnh đến hiệu quả chuyển hóa triglyceride thành hydrocarbon. Tính acid của xúc tác càng mạnh thì độ chuyển hóa càng cao và thu được nhiều sản phẩm nhẹ hơn như xăng và các olefin nhẹ. Xúc tác vi mao quản trung bình như H-ZSM-5 có độ chọn lọc cao với hợp chất vòng thơm thuộc phân đoạn xăng và olefin nhẹ như propylen và ethylen. Với kích thước vi mao quản lớn, xúc tác công nghiệp FCC dựa trên zeolite Y ưu tiên hình thành C4 olefins và các olefin trong phân đoạn xăng. Ở điều kiện phản ứng của quá trình FCC, triglyceride chuyển hóa hiệu quả thành hydrocarbon mà có thể sử dụng làm xăng sinh học cho động cơ và olefin nhẹ làm nguyên liệu cho tổng hợp hóa dầu.

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