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espanolRESUMEN En este documento, se describe el desarrollo e implementacion de un modelo de simulacion molecular que describe la nucleacion del proceso de condensacion de componentes pesados del gas natural mezclas de alcanos lineales (Ci - C6 y C9) a condiciones de transporte (10 - 40 bar). Especificamente, se uso el metodo de Monte Carlo con sesgo configuracional, el campo de fuerza llamado de atomo unido para equilibrio de fases (TraPPE-UA) y la tecnica de muestreo sombrilla. El crecimiento de las gotas fue evaluado con el modelo de Young considerando numeros de Knudsen por debajo de 0.1. Los resultados de simulacion obtenidos para la nucleacion y crecimiento de gota fueron comparados con datos experimentales reportados en la literatura con el fin de validar los modelos implementados. Las simulaciones predicen un tamano de la gota de 2.09 μm el cual esta de acuerdo con los resultados experimentales. EnglishABSTRACT This paper describes the development and implementation of a molecular simulation model to predict the nucleation process during the condensation of heavy components of the gas natural mixtures of linear alkane (C1 - C6 and C9) at transport conditions (10-40 bar). Specifically, it was used the Monte Carlo method with configurational-bias, the united-atom force field known as "Transferable Potentials for Phase Equilibria (TraPPE-UA)," and the Umbrella sampling technique. The growth of the droplets was evaluated with the model of Young considering numbers of Knudsen below 0.1. The simulation results obtained for the droplet nucleation and growth were compared with experimental data reported in the literature with the aim of validating the implemented models. The simulations predict a droplets size of 2.09 μm which is in good agreement with the experimental results.

espanolRESUMEN Las fuerzas de adhesion entre asfalto y diferentes minerales fueron obtenidas empleando el microscopio de fuerza atomica (AFM). El AFM permite el estudio de la interaccion entre dos moleculas en la misma superficie o en interfaces y su comportamiento. En esta investigacion, varias muestras de asfalto con diferentes propiedades fueron puestas en contacto con puntas modificadas para el AFM. Estas puntas fueron fabricadas con minerales comunmente encontrados en los agregados empleados en mezclas asfalticas, como son en dioxido de silicio (SiO2) y el carbonato de calcio (CaCO3). El trabajo de adhesion fue obtenido empleando curvas de fuerza - distancia para cada sistema asfalto-mineral. La medicion directa de las fuerzas desarrolladas entre asfalto y agregado en la interface empleando tecnicas nanoscopicas proveen un mejor entendimiento del sistema y sus caracteristicas. Esto, sin duda alguna contribuira en la seleccion de combinaciones asfalto - agregado empleadas en mezclas asfalticas que desarrollen enlaces mas fuertes, produciendo sistemas mas resistentes a las diferentes fallas relacionadas al fenomeno de adhesion que pueden generarse en pavimentos asfalticos. EnglishABSTRACT The adhesion forces between bitumen and minerals were measured, using Atomic Force Microscopy (AFM). The AFM enables the study of the interactions between two molecules in a same surface or at interfaces and their behavior. In this case, bitumen samples with different properties were placed in contact with AFM modified tips. The tips were fabricated with minerals found in aggregates used in asphalt mixtures, like silicon dioxide (SiO2) and calcium carbonate (CaCO3). The work of adhesion was obtained measuring adhesion forces for each bitumen-mineral pair. The direct measurement of forces between asphalt and aggregates at interface level through nanoscopic techniques provides a better insight of the system and its characteristics. This will help to improve the selection of bitumen-aggregate combinations used in asphalt mixtures, obtaining systems with higher bond strength, therefore more resistant to failures. portuguesRESUMO As forcas de adesao entre o asfalto e diversos minerais foram obtidas atraves microscopio de forca atomica (AFM) O AFM possibilita o estudo entre duas moleculas na mesma superficie ou em interfaces e seu comportamento. Varias amostras de asfalto com diversas propriedades foram colocadas em contato com pontas modificadas para o AFM, nesta pesquisa. Essas pontas foram fabricadas com minerais geralmente encontrados nas adicoes empregadas em misturas asfalticas, tais como dioxido de silicio (SiO2) e o carbonato de calcio (CaCO3). O trabalho de adesao obteve-se empregando curvas de forca (distância para cada sistema asfalto-mineral). A medicao das forcas desenvolvidas entre asfalto e adicao na interface utilizando tecnicas nanoscopicas dao uma melhor compreensao do sistema e suas caracteristicas. Isso, sem duvida nenhuma, ira contribuir na selecao de combinacoes asfalto - adicoes utilizadas em misturas asfalticas que desenvolvam ligacoes mais fortes, produzindo sistemas mais resistentes as diversas falhas relacionadas com o fenomeno de atrito que podem ser geradas em pavimentos asfalticos.

This paper reviews the impact of asphaltenes on wax crystallization and on the properties of crude oils, and the consequences thereof on the flow assurance of waxy crude oil. It initially includes studies of the crystallization of both pure n-alkanes as well as the mixtures thereof, because they have led to an understanding of how their precipitation occurs along with their transitions of crystalline phases, particularly, by studies of X-ray diffraction (XRD). This is followed by the studies and results of crystallization in crude oils and/or the fractions thereof and how their properties are affected in the presence of asphaltenes. The results on the influence of asphaltenes are inconclusive and sometimes contradictory: some confirm that their presence decreases pour point, others affirm that it increases it and yet others say there is no effect. Similar results have been reported for properties such as crystallization point, phase transition and rheological properties. The influence of the chemical structure of asphaltenes on the change in crude oil properties has not been generalized either. It has been inferred that is possibly due to the interaction between aliphatic chains of asphaltenes and waxes, and it has been established that there is synergy in coprecipitation due to evidence in the analysis of organic deposits.