Applications of photothermal displacement spectroscopy to the study of asphaltenes adsorption

We have developed an application of photothermal surface deformation (PTD) to study asphaltenes adsorption on inorganic surfaces. Using an appropriate ratio of the probe and excitation beam spot size at the sample surface we have been able to measure the magnitude of the PTD using a single photodiode detector, The magnitude of the PTD signal is shown to be related to the amount of adsorbed asphaltene. This technique offers a direct non-perturbing and completely contactless detection of adsorbed asphaltenes. Solute-solid adsorption isotherms (SSA) of asphaltenes from two Venezuelan extra-heavy oil (Jobo and Hamaca) were measured using a glass thin plate as adsorbent. The results obtained are in good agreement with those reported using conventional indirect techniques but better precision is achieved. (C) 1998 Elsevier Science B.V.