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Previous issue date: 2010-07-12 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Corrosion is an important phenomenon that frequently occurs in the oil industry,
causing surface ablation, such as it happens on the internal surfaces of oil pipes. This work
aims to obtain new systems to reduce this specific problem. The surfactants SDS, CTAB, and
UNITOL L90 (in micellar and microemulsionated systems) were used as corrosion inhibitors.
The systems were obtained using a C/S ratio of 2, butanol as cosorfactant, kerosene as oil
phase and, as water phase, NaCl solutions of 0.5M with pH = 2, 4, and 7. Microemulsion
regions were found both for direct and inverse micelles. SDS had the higher microemulsion
region and the area was not dependent of pH. The study of micellization of these surfactans in
the liquid-gas interface was carried out via the determination of CMC from surface tension
measurements. Regarding microemulsionated systems, in the case of CTAB, CMC increased
when pH was increased, being constant for SDS and UNITOL L90. Concerning micellar
systems, increase in pH caused decrease and increase in CMC for SDC and CTAB,
respectively. In the case of UNITOL L90, CMC was practically constant, but increased for pH
= 4. The microemulsionated systems presented higher CMC values, except for UNITOL L90
L90. The negative values of free energy of micellization indicated that the process of
adsorption was spontaneous. The results also indicated that, comparing microemulsionated to
systems, adsorption was less spontaneous in the case of SDS and CTAB, while it did not
change for UNITOL L90. SAXS experiments indicated that micelle geometry was spherical,
existing also as halter and flat micelles, resuting in a better inght on the adsorption at the
liquid-solid interface. Efficiency of corrosion inhibition as determined by electrochemical
measurements, from corrosion currents calculated from Tafel extrapolation indicuting heat
showed surfactants to be efficient even at low concentrations. Equilibrium isotherm data were
fitted to the Freundlich model, indicating that surfactant adsorption occurs in the form of
multilayers / A corros?o ? um fen?meno presente em diversos seguimentos da ind?stria do petr?leo,
causando desgastes em superf?cies de equipamentos met?licas, como exemplo a corros?o
interna nos oleodutos. Este trabalho visa obter novos sistemas qu?micos para diminuir tal
problema. Os tensoativos utilizados como inibidores de corros?o foram o SDS, CTAB e
UNITOL L90 em sistemas micelares e microemulsionados. Para obten??o dos sistemas
microemulsionados utilizou-se uma raz?o C/T=2, butanol como cotensoativo, querosene
como fase ?leo e como fase aquosa utilizou-se solu??es de NaCl 0,5M nos pH s 2, 4 e 7. As
regi?es de microemuls?o encontradas para os tr?s tensoativos s?o formadas por micelas
diretas e inversas. A ?rea se mant?m constante com a varia??o do pH, o SDS tem maior regi?o
de microemuls?o. O estudo da miceliza??o destes tensoativos na interface l?quido-g?s foi
realizado a partir de medidas de tens?o superficial obtendo os valores de c.m.c, os quais foram
particamente constantes para os sistemas microemulsionados com os tensoativos SDS e
UNITOL L90 L90, e aumentaram para o CTAB quando elevou-se o pH. Os valores de c.m.c
para os sistemas micelares com os tensoativos SDS e CTAB diminu?ram e aumentaram,
respectivamente, quando aumentou-se o pH. J? o UNITOL L90 apresentou valores
praticamente constantes, por?m foi maior em pH 4. Os sistemas microemulsionados
apresentaram valores de c.m.c maiores, exceto para o tensoativo UNITOL L90. Os valores
negativos de energia livre de miceliza??o indicaram que o porcesso de adsor??o ? espont?neo.
Os resultados mostraram que os sistemas microemulsionados para os tensoativos SDS e
CTAB foram menos espont?neos comparados ao sistema micelar, enquanto o UNITOL L90
apresentou valores praticamente constantes. Experimentos com SAXS mostraram que as
geometrias das micelas foram esf?ricas, existindo ainda na forma de halteres ou de micelas
achatadas, o que facilitou a compreens?o do estudo de adsor??o na interface l?quido-s?lido.
As efici?ncias de inibi??o ? corros?o foram determinadas mediante medidas eletroqu?micas, a
partir das correntes de corros?o encontradas atrav?s da extrapola??o de Tafel. Os tensoativos
estudados se mostraram eficientes mesmo em baixas concentra??es. Os dados experimentais
de ajustaram ao modelo da isoterma de Freundlich, indicando que a adsor??o dos tensoativos
ocorre em multicamadas
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/17629 |
| Date | 12 July 2010 |
| Creators | Roberto, Erileide Cavalcanti |
| Contributors | CPF:07286937391, http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4783139Z0&dataRevisao=null, Huitle, Carlos Alberto Martinez, CPF:01139059980, http://lattes.cnpq.br/2485073932883264, Santanna, Vanessa Cristina, CPF:77938780430, http://lattes.cnpq.br/9445575768909084, Wanderley Neto, Alcides de Oliveira, Dantas, Tereza Neuma de Castro |
| Publisher | Universidade Federal do Rio Grande do Norte, Programa de P?s-Gradua??o em Qu?mica, UFRN, BR, F?sico-Qu?mica; Qu?mica |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | Portuguese |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Format | application/pdf |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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