Mineral matter hydropyrolysis of Tarfaya oil shale and influence of sedimentation edge

Abstract

In hydrotreating the reactivity of the mineral matter of the oil shale from the five layers of the Tarfaya deposit and the M layer of the Timahdit deposit, both located in Morocco, is different. This reactivity is a function of the climates of the geological eras: Z0 (Tertiary era: cold climate), Z1 (Maestrichtian: hot climate), Z2 (Senonian: cold climate), Z3 (Turonian: warm climate) and Z4 (Cenomanian: warm climate). This explains why the Z3 and Z4 layers are the most reactive, also due to the location of the low peak temperatures as established by derivative thermogravimetry (DTG) for these two layers. There was also a disproportion between the DTG peak area values and the reactivity of the mineral material. The composition of dolomite CaMg(CO3 )2 in the Z1 layer is responsible for the low reactivity observed for this layer. Oil shale is a sedimentary rock which is composed of a complex mixture of organic and mineral matter. It is a natural mineral resource, and constitutes a richness of Morocco, with the most important deposits being Tarfaya of marine origin and Timahdit of lacustrine origin. A comparison was made between the reactivity of the mineral matter of layers Z1, Z2, Z3, Z4 (deposit of Tarfaya) and M (deposit of Timahdit) by using the thermogravimetric analysis (TGA) coupled with its derivative. This is a technique of analysis consisting in following the loss in mass of a compound according to the temperature in dynamic regime at three speeds of heating: 9 °C/min, 15 °C/min and 21 °C/min. This analysis was carried out for the hydrotreating reaction (hydrogen carrier gas) for the 5 layers of Tarfaya: Z0, Z1, Z2, Z3, Z4 and the M layer of Timahdit. The influence of the climate of the sedimentation geological stage of the different layers of the Tarfaya deposit was discussed in order to understand the corresponding reactivity.

Keywords

• hydropyrolysis
• moroccan oil shale
• mineral matter
• thermo-gravimetric analysis
• reactivity
• x-ray diffraction.