Removal of Lipophilic Wood Extractives from TMP Process Waters by Wet Oxidation

Työssä tutkittiin kokeellisesti rasvaliukoisten uuteaineiden poistamista TMP -prosessin vesikierroista märkähapetuksen avulla. Työn tavoitteena oli tutkia mahdollisuudet hyödyntää TMP -prosessissa vallitsevaa korkeaa lämpötilaa rasvaliukoisten uuteaineiden poistamiseen hapettamalla niitä puhtaalla hapella. Kirjallisuusosassa tarkasteltiin märkähapetuksen teknologiaa, reaktiomekanismia, käytettyjä katalyyttejä, käyttökohteita sekä kustannuksia. Kokeita suoritettiin autoklaavireaktorissa lämpötiloissa 140 °C, 160 °C ja 180 °C. Vetyperoksidia käytettiin katalyyttinä lisätyn vetyperoksidin määrän ollessa 100 - 1800 mg/l ja hapen osapaineen ollessa 0 ( typpiatmosfääri) - 15 baria. Kokeissa tarkasteltiin kemiallisen hapenkulutuksen (COD), rasvaliukoisten uuteaineiden konsentraation, orgaanisen kokonaishiilen (TOC) ja värin muutoksia kokeiden aikana eri lämpötiloilla, hapen osapaineilla ja lisätyn vetyperoksidin määrillä. Kokeissa saavutettiin 30 %:n COD:n vähenemä sekä 90 %:n vähenemä rasvaliukoisissa uuteaineissa lämpötiloissa 160 °C ja 180 °C. Lisäämällä vetyperoksidia katalyyttinä saavutettiin lähes sama tulos lämpötilassa 140 °C. Suurin tässä työssä havaittu ongelma oli lisääntynyt värinmuodostus vedessä olevassa hienojakoisessa kiintoaineessa hapetuksen aikana. Tämän vuoksi lisätutkimukset ovat tarpeellisia sen seikan selvittämiseksi, voidaanko muodostunut väri mahdollisesti poistaa massan valkaisussa.

Lipase Improvement: Goals and strategies

Lipases have received great attention as industrial biocatalysts in areas like oils and fats processing, detergents, baking, cheese making, surface cleaning, or fine chemistry . They can catalyse reactions of insoluble substrates at the lipid-water interface, preserving their catalytic activity in organic solvents. This makes of lipases powerful tools for catalysing not only hydrolysis, but also various reverse reactions such as esterification, transesterification, aminolysis, or thiotransesterifications in anhydrous organic solvents. Moreover, lipases catalyse reactions with high specificity, regio and enantioselectivity, becoming the most used enzymes in synthetic organic chemistry. Therefore, they display important advantages over classical catalysts, as they can catalyse reactions with reduced side products, lowered waste treatment costs, and under mild temperature and pressure conditions. Accordingly, the use of lipases holds a great promise for green and economical process chemistry.

The initial oxidation of transition metal surfaces

Due to their numerous novel technological applications ranging from the example of exhaust catalysts in the automotive industry to the catalytic production of hydro- gen, surface reactions on transition metal substrates have become to be one of the most essential subjects within the surface science community. Although numerous applications exist, there are many details in the different processes that, after many decades of research, remain unknown. There are perhaps as many applications for the corrosion resistant materials such as stainless steels. A thorough knowledge of the details of the simplest reactions occuring on the surfaces, such as oxidation, play a key role in the design of better catalysts, or corrosion resistant materials in the future. This thesis examines the oxidation of metal surfaces from a computational point of view mostly concentrating on copper as a model material. Oxidation is studied from the initial oxidation to the oxygen precovered surface. Important parameters for the initial sticking and dissociation are obtained. The saturation layer is thoroughly studied and the calculated results arecompared with available experimental results. On the saturated surface, some open questions still remain. The present calculations demonstrate, that the saturated part of the surface is excluded from being chemically reactive towards the oxygen molecules. The results suggest, that the reason for the chemical activity of the saturated surface is due to a strain effect occuring between the saturated areas of the surface.

Síntese de catalisadores Ziegler-Natta: algumas rotas e suas dificuldades

The Ziegler-Natta catalyst and the polymerization thereof are systems which require careful handling and special treatment of chemicals. In spite of the use of inert atmosphere and dry chemicals, some Ziegler-Natta systems may present low activities or even may deactivate because of unsuitable handling. Some features of the TiCl3 synthesis and its characterization when related to the presence of impurities are described. Evidences of poor handling of chemicals and/or laboratory devices while in synthesis of the catalyst are emphasized. The problems arising from butadiene polymerization and some relevant details in propylene polymerization are also presented with teaching objectives.

Recuperação de metais de catalisadores usados de hidrotratamento (NiMo E CoMo/AL2O3)

This work presents a detailed study of the leaching behavior of deactivated hydrotreating catalysts (CoMo, NiMo/Al2O3) in presence of oxalate and NH4+ ions in various media. The yield of metals recovery may be optimized by adjusting several experimental parameters (time, temperature, etc). Leaching is limited by physical factors (diffusional effects caused by coke) and by the existence of silicate/spinel-like species which are poorly soluble in leaching solutions. Coke may be eliminated by an oxidation step at temperatures between 300-400ºC. Above 400ºC, solubilization of Ni and Co is drastically reduced. 50-90% wt of sulphate species and 15-30% wt of phosphate ions are solubilized during leaching. Silicon (as SiO2) is not solubilized. The best Ni-Co-Mo recoveries are in the 70-90% wt range; Fe recovery may be quantitative, whereas Al leaching may be lower than 5% wt.

Ação promotora do berílio em catalisadores da síntese do estireno

The catalytic dehydrogenation of ethylbenzene in presence of steam is the main commercial route to produce styrene. The industrial catalysts are potassium- and chromia-doped hematite which show low surface areas leading to bad performance and short life. In order to develop catalysts with high areas, the effect of beryllium on the textural properties and on the catalytic performance of this iron oxide was studied. The influence of the amount of the dopant, the starting material and the calcination temperature were also studied. In sample preparations, iron and beryllium salts (nitrate or sulfate) were hydrolyzed with ammonia and then calcinated. The experiments followed a factorial design with two variables in two levels (Fe/Be= 3 and 7; calcination temperature= 500 and 700ºC). Solids without any dopant were also prepared. Samples were characterized by elemental analysis, infrared spectroscopy, surface area and porosity measurements, X-ray diffraction, DSC and TG. The catalysts were tested in a microreactor at 524ºC and 1 atm, by using a mole ratio of steam/ ethylbenzene=10. The selectivity was measured by monitoring styrene, benzene and toluene formation. It was found that the effect of beryllium on the characteristics of hematite and on its catalytic performance depends on the starting material and on the amount of dopant. Surface areas increased due to the dopant as well as the nature of the precursor; samples produced by beryllium sulfate showed higher areas. Beryllium-doped solids showed a higher catalytic activity when compared to pure hematite, but no significant influence of the anion of starting material was noted. It can be concluded that beryllium acts as both textural and structural promoter. Samples with Fe/Be= 3, heated at 500ºC, lead to the highest conversion and were the most selective. However, catalysts prepared from beryllium sulfate are the most promising to ethylbenzene dehydrogenation due to their high surface area which could lead to a longer life.

Anticorpos catalíticos: expandindo o alcance da catálise enzimática

The vast binding repertoire of the immune system has been exploited for the generation of tailor-made selective catalysts. Since the first reports of chemical reactions catalyzed by antibodies were published, research in this field, which borders chemistry and biology, has been rapidly established and a number of catalytic antibodies that carry out a wide range of reactions, have been developed. Recent advances have led to antibodies that catalyse complex, multi-step reactions and difficult chemical transformations, as well as reactions that do not have an organic equivalent at all. Current research in this field has been devoted to practical applications of this technology.

Troca iônica no estado sólido de európio3+ em zeólita Y: influência do tempo de reação

Rare earth elements supported in zeolites are the most important catalysts in the fluid cracking of petroleum. The solid state ion exchange of Eu3+ in Y zeolite was investigated. First of all, the hydrated EuCl3 was well mixed in a ball mill and was then heated at 300ºC for different times. The quantitative determination of Eu3+ showed that the degree of ion exchange depends on the reaction time at constant temperature, being ~95% in 4 h. The X-ray study showed that the crystallinity of the zeolite is little affected by the exchange procedure. The study of spectroscopic properties of Eu3+, emission spectra and lifetime, give information about the migration and position of the ion in the zeolite cages.

Hidróxidos duplos lamelares: síntese, estrutura, propriedades e aplicações

The layered double hydroxides, known as anionic clays and represented by the general formula [M2+1-x M3+x (OH) 2]x+ Am-x/m·nH 2O, are a group of materials which are of much interest currently. They present a variety of potential applications as adsorbents, catalysts and catalyst support, ion-exchangers, antacids and as a polymer stabilizer. It is possible to obtain a broad variety of layered double hydroxides (LDHs), depending on the identity and ratio of the cations M2+ and M3+, as well as the interlamelar anion. The aim of this review is to give out some information about this class of materials, concerning to the synthesis, characterization, properties and applications.

Propriedades texturais e catalíticas de óxidos de ferro contendo cromo e cobre

Chromium and copper-doped hematites were prepared with the aim of studying the synergistic effect of these dopants on the textural and on the catalytic properties of the iron oxides towards the high temperature shift reaction. It was found that the most active catalysts were those with the highest amount of copper. They had the Fe(II)/Fe(III) ratio near the stoichiometric value of magnetite, the highest surface areas under the reactional atmosphere and the greatest tendency to produce the active form; they also were poorly crystalline solids. The best performance was shown by the catalyst with Fe/Cu=10, heated at 300ºC. It can thus be concluded that copper acts both as textural and structural promoter in these catalysts.

Fischer-Tropsch Slurry Bubble Column Reactor Modeling

The literature part of the work reviews overall Fischer-Tropsch process, Fischer-Tropsch reactors and catalysts. Fundamentals of Fischer-Tropsch modeling are also presented. The emphasis is on the reactor unit. Comparison of the reactors and the catalysts is carried out to choose the suitable reactor setup for the modeling work. The effects of the operation conditions are also investigated. Slurry bubble column reactor model operating with cobalt catalyst is developed by taking into account the mass transfer of the reacting components (CO and H2) and the consumption of the reactants in the liquid phase. The effect of hydrostatic pressure and the change in total mole flow rate in gas phase are taken into account in calculation of the solubilities. The hydrodynamics, reaction kinetics and product composition are determined according to literature. The cooling system and furthermore the required heat transfer area and number of cooling tubes are also determined. The model is implemented in Matlab software. Commercial scale reactor setup is modeled and the behavior of the model is investigated. The possible inaccuraries are evaluated and the suggestions for the future work are presented. The model is also integrated to Aspen Plus process simulation software, which enables the usage of the model in more extensive Fischer-Tropsch process simulations. Commercial scale reactor of diameter of 7 m and height of 30 m was modeled. The capacity of the reactor was calculated to be about 9 800 barrels/day with CO conversion of 75 %. The behavior of the model was realistic and results were in the right range. The highest uncertainty to model was estimated to be caused by the determination of the kinetic rate.

Decomposição catalítica de óleo de soja em presença de diferentes zeólitas

The catalytic decomposition of soybean oil was studied in a fix bed reactor at 673 and 773 K and using amorphous silica-alumina and the zeolites USY, H-Mordenite and H-ZSM-5 as catalysts. Both the selectivity and the catalytic activity were determined by studying the product composition resulting from the chemical reactions. Physicochemical characteristics of the catalysts were obtained by X-ray fluorescence, Fourier Transform infrared spectroscopy, 29Si and 27Al Nuclear Magnetic Ressonance and textural analysis. The zeolites USY and H-ZSM-5, showing higher Brönsted acidity, yielded products with higher concentration in aromatic hydrocarbons, whereas with both H-Mordenite and amorphous silica-alumina the main products were paraffins.

Ácido L-ascórbico: reações de complexação e de óxido-redução com alguns íons metálicos de transição

The strong reducing action of L-ascorbic acid (Vitamin C) are of fundamental interest in biochemical and related process. The oxidation of ascorbic acid by molecular oxygen and others oxidants are of fundamental importance, involving the intervention of transition metal ions as catalysts and the formation transition metal complexes of ascorbic acid as intermediates. The present article is intended to cover some aspects of the reactions of ascorbic acid and related compounds involving some transition metal ions.

Argilas pilarizadas - uma introdução

The synthesis, characterization and some applications in catalysis of pillared clays are described at an introductory level. The use of x-ray diffraction, surface area measurements, thermal analysis, IR spectrophotometry and solid-state NMR in the characterization of pillared clays is briefly discussed. Pillarization followed by doping or introduction of metal clusters into clays could lead to the development of selective heterogeneous catalysts.

Atividade e seletividade de catalisadores a base de caulim modificado

Studies of the use of a soil from river Pardo basin located at the Ribeirão Preto region, were realized with the aim of preparing catalysts. A clay, high purity kaolin type, was obtained after purification followed by treatment with acid and then calcined. The activity and selectivity of the catalysts were determined using cycloexene as substrate. The majority of the catalysts obtained yield a conversion higher than 70%.