Kinetics and microkinetic study of the selective oxidation of ethanol on an alumina-supported silver catalyst

Orientador: Gustavo Paim ValençaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia QuímicaResumo: A cinética da oxidação seletiva do etanol a acetaldeído num catalisador 2,56%Ag/Al2O3 foi determinada experimentalmente em um reator de leito fixo a 150 e 170 °C, e um modelo micro-cinético foi desenvolvido baseado no formalismo UBI-QEP. Inicialmente, catalisadores Ag/Al2O3 com teores nominais de prata entre 0,5 e 10% m/m foram preparados mediante impregnação úmida com excesso de solvente; caracterizados por DRX, MEV/EDS, fisissorção de N2, picnometria de hélio, ICP-OES, quimissorção de O2 e TPR; e foram testados na reação de oxidação de etanol, em fase vapor, a temperaturas entre 150 e 250 °C, usando razões molares entre o etanol e o oxigênio de 0,6 e 0,2 e massas de catalisador entre 25 e 200 mg. A taxa de reação foi calculada utilizando o método do reator diferencial e a lei de velocidade de reação foi obtida mediante ajustes da taxa de reação a modelos de lei de potência e do tipo Langmuir-Hinshelwood. Por último, foi utilizada uma sequência de reações elementares para o desenvolvimento do estudo micro-cinético conforme o método UBI-QEP. Os catalisadores Ag/Al2O3 com teores nominais de prata acima de 2% m/m mostraram alta seletividade a acetaldeído e CO2. A cinética da oxidação parcial do etanol a acetaldeído a 150 °C apresentou um comportamento do tipo Langmuir¿Hinshelwood, enquanto a 170 °C apresentou um comportamento do tipo lei de potência, mostrando uma ordem de reação parcial de 0,41 com relação à pressão parcial do etanol e de -0,15 com relação à pressão parcial do oxigênio. A energia de ativação da reação foi de 50,5 kJ mol-1. Cálculos da concentração de etanol na superfície do catalisador e do coeficiente de Weisz-Prater confirmaram que a taxa de reação não foi afetada por limitações de transferência de massa interna ou externa. Finalmente, um modelo micro-cinético foi desenvolvido e comparado com a cinética de reação obtida experimentalmenteAbstract: The rate law of the selective oxidation of ethanol to acetaldehyde on a 2.56%Ag/Al2O3 catalyst at 150 and 170 °C was determined using a packed bed reactor. Also, a micro-kinetic model was developed using an appropriate sequence of elementary reactions and the UBI-QEP method. Several Ag/Al2O3 catalysts with nominal silver load from 0.5 up to 10 wt% were prepared, characterized and tested in the catalytic oxidation of ethanol in vapor phase. The reaction rate was calculated using the differential reactor method and the rate law was obtained by fitting the reaction rate to power law and Langmuir-Hinshelwood models. The catalysts Ag/Al2O3 with nominal silver loads above 2 wt% showed high selectivity to acetaldehyde and CO2. The kinetics of the partial oxidation of ethanol to acetaldehyde at 150 °C showed a behavior Langmuir-Hinshelwood type, whereas at 170 °C it showed a power law behavior type, with a partial reaction order of 0.41 in relation to the partial pressure of ethanol and -0.15 in relation to the partial pressure of oxygen. The activation energy was 50.5 kJ mol-1. The reaction rate was not limited by internal or external mass transfer. Finally, a micro-kinetic model was developed and compared to the rate law obtained experimentallyDoutoradoEngenharia de ProcessosDoutor em Engenharia Química142738/2011-533003017034P8CNPQCAPE

Assessing technology for reducing the viscosity of heavy petroleum residues using laser

Orientador: Rubens Maciel FilhoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia QuímicaResumo: Na presente dissertação foi avaliado o uso de radiação infravermelha, produzida por um laser de CO2, na viscorredução de frações pesadas do petróleo, sendo uma tecnologia inédita na literatura. O principal critério utilizado para a avaliação da tecnologia foi comparar as viscosidades dos resíduos da destilação atmosférica antes e depois de serem irradiados sob diferentes condições operacionais do laser. Para estabelecer um perfil adequado de comparação foi realizado um amplo estudo reológico destes materiais usando-se de um reômetro de placas paralelas. Caracterizações químicas e térmicas; assim como simulações numéricas do efeito térmico do laser sobre os resíduos foram também desenvolvidas para uma melhor avaliação do processo. Os resíduos atmosféricos mostraram estar constituídos por hidrocarbonetos na faixa dos C20 a C110 e de alto grau de aromaticidade; sendo 5% da sua composição correspondente a hidrocarbonetos asfalténicos. Esta composição fez com que o comportamento newtoniano fosse obtido a temperaturas de 100 °C, para o resíduo mais pesado, e 90 ºC para o menos pesado, apresentando a estas temperaturas viscosidades de 1200 e 500 cP, respectivamente. As irradiações com o laser em modo automático permitiram reduzir estes valores em até 13%; enquanto que as irradiações em modo manual produziram o efeito contrário devido à excessiva liberação de gases. Finalmente, a simulação com o software ANSYS CFX 11.0 demonstrou a alta sensibilidade da temperatura da amostra quando realizadas pequenas modificações nos parâmetros operacionais do laser assim como o pequeno volume de amostra capaz de atingir a temperatura de craqueamento durante a irradiação.Abstract: The use of infrared radiation produced by a CO2 laser in visbreaking of heavy fractions of petroleum was assessed. The main criterion used to evaluate the technology was to compare the viscosities of atmospheric distillation residues before and after being irradiated under different operating conditions of the laser. A suitable profile for comparison was developed through a large rheological study of the materials by using a parallel plate rheometer. Chemical and thermal characterizations, as well as numerical simulations of the thermal effect of laser on the atmospheric residues were also developed aiming a better evaluation of the process. The atmospheric residua analyzed shown to be composed by hydrocarbons with carbon chains ranging from C20 to C110 and a high degree of aromaticity, corresponding the 5% of its composition to asphaltenic hydrocarbons. The Newtonian behavior was obtained at temperatures of 100 ° C, for the heavier residue, and 90 ° C for the lightest one, showing viscosities of 1200 and 500 cP, at these temperatures, respectively. The irradiations with the laser in automatic mode led to a reduction of these figures by 13%, while in manual mode, the radiation produced the opposite effect due to excessive release of gases. Finally, the simulation with ANSYS CFX 11.0 demonstrated the high sensitivity of the sample temperature when carried out minor modifications to the operating parameters of the laser as well as the small sample volume that attains the cracking temperature during irradiation.MestradoDesenvolvimento de Processos QuímicosMestre em Engenharia Químic

Optimiranje proizvodnje β-fruktofuranozidaze s pomoću gljivice Aspergillus carbonarius iz poljoprivrednog otpada i primjena tog enzima u proizvodnji invertnog šećera

Research background. Microbial β-fructofuranosidases are widely employed in food industry to produce inverted sugar or fructooligosaccharides. In this study, a newly isolated Aspergillus carbonarius PC-4 strain was used to optimize the β-fructofuranosidase production in a cost-effective process and the sucrose hydrolysis was evaluated to produce inverted sugars. Experimental approach. Optimization of nutritional components of culture medium was carried out using simplex lattice mixture design for 72 and 120 h at 28 °C. One-factor-at-a-time methodology was used to optimize the physicochemical parameters. Crude enzyme was used for sucrose hydrolysis at different concentrations. Results and conclusions. The optimized conditions of enzyme production were achieved from cultivations containing pineapple crown waste (1.3%, m/V) and yeast extract (0.3%, m/V) after 72 h with an enzyme activity of 9.4 U/mL, obtaining R2=91.85%, R2adjusted=85.06%, highest F-value (13.52) and low p-value (0.003). One-factor-at-a-time used for optimizing the physicochemical conditions showed optimum temperature (20 °C), pH (5.5), agitation (180 rpm) and time course (72 h) with a 3-fold increase of enzyme production. The invertase-induced sucrose hydrolysis showed the maximum yield (3.45 mmol of reducing sugars) using 10% of initial sucrose concentration. Higher sucrose concentrations caused the inhibition of invertase activity, possibly due to the saturation of substrate or formation of sucrose aggregates, making it difficult for the enzyme to access sucrose molecules within the created clusters. Therefore, a cost-effective method was developed for the invertase production using agroindustrial waste and the produced enzyme can be used efficiently for inverted sugar production at high sucrose concentration. Novelty and scientific contribution. This study presents an efficient utilization of pineapple crown waste to produce invertase by a newly isolated Aspergillus carbonarius PC-4 strain. This enzyme exhibited a good potential for inverted sugar production at high initial sucrose concentration, which is interesting for industrial applications.Pozadina istraživanja. Mikrobne β-fruktofuranozidaze imaju široku primjenu u prehrambenoj industriji, i to u proizvodnji invertnog šećera ili fruktooligosaharida. U ovom je radu korišten novi soj gljivice Aspergillus carbonarius PC-4 za optimiranje ekonomski isplativog postupka proizvodnje β-fruktofuranozidaze, te je ispitana hidroliza saharoze radi dobivanja invertnih šećera. Eksperimentalni pristup. Sastav hranjive podloge optimiran je primjenom simpleks-metode tijekom 72 i 420 h pri 28 °C. Jednofaktorskom su metodom optimirani fizikalno-kemijski uvjeti proizvodnje enzima. Sirovi je enzim korišten za hidrolizu saharoze pri različitim koncentracijama. Rezultati i zaključci. Optimirani su uvjeti proizvodnje enzima dobivenog uzgojem na podlozi s krunom ploda ananasa (1,3 % m/V) i ekstraktom kvasca (0,3 % m/V) nakon 72 h, pri čemu je aktivnost enzima iznosila 9,4 U/mL, s R²=91,85 %, R²adj=85,06 %, najvišom F-vrijednosti (13,52) i niskom p-vrijednosti (0,003). Jednofaktorskom su metodom određeni sljedeći optimalni fizikalno-kemijski uvjeti: temperatura od 20 °C; pH-vrijednost od 5,5; brzina miješanja od 180 okretaja u minuti i trajanje postupka od 72 h, pri čemu je proizvedena trostruko veća količina enzima. Najveći prinos reducirajućih šećera pri hidrolizi saharoze pomoću invertaze s početnom količinom od 10 % saharoze bio je 3,45 mmol. Veće količine saharoze inhibirale su aktivnost invertaze, vjerojatno zbog zasićenja podloge ili formiranja nakupina šećera koje su enzimu otežale pristup molekulama saharoze. Zaključeno je da je razvijen ekonomski isplativ postupak proizvodnje invertaze iz agroindustrijskog otpada, a da se dobiveni enzim može učinkovito upotrijebiti za dobivanje invertnog šećera pri većim količinama saharoze. Novina i znanstveni doprinos. U radu je prikazan djelotvoran način iskorištenja krune ploda ananasa kao biootpada u proizvodnji invertaze s pomoću novog soja gljivice Aspergillus carbonarius PC-4. Dobiveni je enzim pokazao potencijal za proizvodnju invertnog šećera pri velikoj početnoj količini saharoze, što je korisno za industrijsku primjenu

Processo De Craqueamento E Petróleo Com Laser De Co2

PROCESSO DE CRAQUEAMENTO DE PETRÓLEO COM LASER DE CO2. Um processo para o craqueamento rápido de petróleos pesados e resíduos ultra pesados de petróleo foi proposto com a finalidade de romper as cadeias de hidrocarbonetos pelo aquecimento (craqueamento) através da energia térmica gerada pela interação laser de CO2/petróleo. O processo é operado sob uma ampla variedade de condições de irradiação em uma faixa de temperatura entre 200 a 1000°C, suficiente para dar inicio as reações de craqueamento térmico.BRPI0900271 (E2); BRPI0900271 (A2)C10G15/10BR2009PI00271C10G15/1

Tropical tree growth driven by dry-season climate variability

Interannual variability in the global land carbon sink is strongly related to variations in tropical temperature and rainfall. This association suggests an important role for moisture-driven fluctuations in tropical vegetation productivity, but empirical evidence to quantify the responsible ecological processes is missing. Such evidence can be obtained from tree-ring data that quantify variability in a major vegetation productivity component: woody biomass growth. Here we compile a pantropical tree-ring network to show that annual woody biomass growth increases primarily with dry-season precipitation and decreases with dry-season maximum temperature. The strength of these dry-season climate responses varies among sites, as reflected in four robust and distinct climate response groups of tropical tree growth derived from clustering. Using cluster and regression analyses, we find that dry-season climate responses are amplified in regions that are drier, hotter and more climatically variable. These amplification patterns suggest that projected global warming will probably aggravate drought-induced declines in annual tropical vegetation productivity. Our study reveals a previously underappreciated role of dry-season climate variability in driving the dynamics of tropical vegetation productivity and consequently in influencing the land carbon sink

Tropical tree growth driven by dry-season climate variability

Interannual variability in the global land carbon sink is strongly related to variations in tropical temperature and rainfall. This association suggests an important role for moisture-driven fluctuations in tropical vegetation productivity, but empirical evidence to quantify the responsible ecological processes is missing. Such evidence can be obtained from tree-ring data that quantify variability in a major vegetation productivity component: woody biomass growth. Here we compile a pantropical tree-ring network to show that annual woody biomass growth increases primarily with dry-season precipitation and decreases with dry-season maximum temperature. The strength of these dry-season climate responses varies among sites, as reflected in four robust and distinct climate response groups of tropical tree growth derived from clustering. Using cluster and regression analyses, we find that dry-season climate responses are amplified in regions that are drier, hotter and more climatically variable. These amplification patterns suggest that projected global warming will probably aggravate drought-induced declines in annual tropical vegetation productivity. Our study reveals a previously underappreciated role of dry-season climate variability in driving the dynamics of tropical vegetation productivity and consequently in influencing the land carbon sink

Global attitudes in the management of acute appendicitis during COVID-19 pandemic: ACIE Appy Study

Background: Surgical strategies are being adapted to face the COVID-19 pandemic. Recommendations on the management of acute appendicitis have been based on expert opinion, but very little evidence is available. This study addressed that dearth with a snapshot of worldwide approaches to appendicitis. Methods: The Association of Italian Surgeons in Europe designed an online survey to assess the current attitude of surgeons globally regarding the management of patients with acute appendicitis during the pandemic. Questions were divided into baseline information, hospital organization and screening, personal protective equipment, management and surgical approach, and patient presentation before versus during the pandemic. Results: Of 744 answers, 709 (from 66 countries) were complete and were included in the analysis. Most hospitals were treating both patients with and those without COVID. There was variation in screening indications and modality used, with chest X-ray plus molecular testing (PCR) being the commonest (19\ub78 per cent). Conservative management of complicated and uncomplicated appendicitis was used by 6\ub76 and 2\ub74 per cent respectively before, but 23\ub77 and 5\ub73 per cent, during the pandemic (both P < 0\ub7001). One-third changed their approach from laparoscopic to open surgery owing to the popular (but evidence-lacking) advice from expert groups during the initial phase of the pandemic. No agreement on how to filter surgical smoke plume during laparoscopy was identified. There was an overall reduction in the number of patients admitted with appendicitis and one-third felt that patients who did present had more severe appendicitis than they usually observe. Conclusion: Conservative management of mild appendicitis has been possible during the pandemic. The fact that some surgeons switched to open appendicectomy may reflect the poor guidelines that emanated in the early phase of SARS-CoV-2

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field