Catalyst deactivation during hydrotreating of Maya crude in a batch reactor

The deactivation of a hydrotreating catalyst is investigated in a batch reactor by using Maya heavy crude as a feed. A reference catalyst NiMo supported on gamma alumina having wide pore diameter is used to evaluate hydrodemetallation (HDM) and hydrodesulfurization (HDS) activities. It is found that, with increasing contact time, the conversion and deposits increase. The pore size distribution results show that surface area and total pore volume significantly reduce on the spent catalysts due to coke deposits. However, loss of these properties is reversed upon regeneration of the spent catalysts. It is observed from SEM study that coke preferably deposits on the pore mouth whereas vanadium is more evenly distributed throughout the catalyst particles. These deposits cause the deactivation of HDM activity; however, the reason for the loss of HDS activity is only the presence of metal deposits which may cover active sites.