Saud Aldrees

A research into the thermodynamics of methanol to hydrocarbon (MTH): conflictions between simulated product distribution and experimental results

Thermodynamic calculations and analysis were carried out for a rational understanding of the results from selected laboratory MTH reactions. Simulations without solid carbons (coke), CO, CO2 and light alkanes target on the yield of olefin and aromatic products, which has been found better referenced to the real experimental observations that occur in time-on-stream (TOS). The confliction between simulated data and real experimental results is presumably ascribed to the limited dwelling time of products in the reaction system. Hydrocarbon pool based reactions donate olefins and methyl-benzenes as primary products in a continuous-flow MTH reaction; when the dwelling time of product extends intra-conversions (H2 transfers) between products would further adjust the composition of MTH yield, in which case alkanes and aromatic products (cokes precursors) increase. In the case of intra-conversions are ignored due to limited product dwelling time, thermodynamic calculation on Gibbs free energy change of selected sub reactions shows fairly close results to the real experimental data, which well supports the above explanations. This work highlights the importance of proper choosing target products and/or sub reactions for a rational thermodynamic prediction of MTH product distribution obtained in time-on-stream.

Effect of urea/metal ratio on the performance of NiMoP/Al2O3 catalyst for diesel deep HDS

Alumina-supported NiMoPOx catalysts have been prepared using urea matrix combustion–decomposition method. The effect of urea/metal ratios on the metal oxide dispersion, the conversion of the metal precursor to oxide and the structure and catalyst performance for diesel HDS has been studied. It is shown that the addition of urea adjusts the metal–support interaction, leading to the easy reduction of the metal oxide over the catalyst surface. It also changes the surface cluster of the oxide and the oxide structure. The addition of urea to metal matrix significantly improves the catalytic diesel HDS performance and increases the catalyst stability. The urea to Ni metal ratio of 2 gives the highest sulfur removal rate in the real diesel HDS process.