p-Xylene is an important industrial compound, and its demand has been increasing in recent years. It is mostly produced from cracking of naphtha, but there is a need for new and cost-effective methods for the production. Toluene alkylation with methanol over an alumino-silicate zeolite catalyst, such as ZSM-5, produces a mixture of xylene isomers with low p-xylene selectivity. Due to the very close boiling points of xylene isomers, it is very expensive to separate them. There has been some success in enhancing p-xylene selectivity by modifying the ZSM-5 catalyst. This results in reduced separation cost, which makes toluene methylation a competitive process for p-xylene production. Based on these findings, a novel process for the production of p-xylenes by the catalytic methylation of toluene followed by reactive distillation for the separation of p-xylene (instead of the more costly conventional technique of separation based on crystallization and adsorption) is developed and a complete process flow diagram is simulated using Aspen Plus. Using the built-in optimization tool in Aspen Plus, we optimized reactor parameters for a maximum p-xylene selectivity of 97.7%. After separation, a p-xylene product stream purity of 99.7% is achieved. High p-xylene selectivity in the reactor and use of reactive distillation reduces the separation cost and renders the new process economically competitive.

No abstract

No abstract

The use of numerical modeling in oil spill incidents is a well established technique that has proven to provide cost-effective and reasonable estimates of oil surface drift. Good predictability of such models depends highly on the quality of the input data of the incident and on the model calibration effort. This paper presents the results of simulating oil spillage trajectory in the Arabian (Persian) Gulf. The study employed a 3-D rectilinear hydrodynamic model combined with oil spill model. Typical representative environmental conditions of the Arabian Gulf were first setup into a hydrodynamic circulation model using data from various sources. The performance of the hydrodynamic model was then tested against measurements of tidal fluctuation and sea currents at selected locations. The spill analysis model was setup using the flow field produced from the hydrodynamic simulation and its performance was further validated against documented events of Al-Ahmadi historical oil spill crisis in the Gulf. The comparison of the actual and simulated oil spill drift was found reasonably acceptable allowing for further application in risk assessment studies in UAE Coastal water and in the entire Arabian Gulf as well.

No abstract