Stability and Activity of Rhodium Promoted Nickel-Based Catalysts in Dry Reforming of Methane.

The rhodium oxide (Rh2O3) doping effect on the activity and stability of nickel catalysts supported over yttria-stabilized zirconia was examined in dry reforming of methane (DRM) by using a tubular reactor, operated at 800 °C. The catalysts were characterized by using several techniques including nitrogen physisorption, X-ray diffraction, transmission electron microscopy, H2-temperature programmed reduction, CO2-temperature programmed Desorption, and temperature gravimetric analysis (TGA). The morphology of Ni-YZr was not affected by the addition of Rh2O3. However, it facilitated the activation of the catalysts and reduced the catalyst's surface basicity. The addition of 4.0 wt.% Rh2O3 gave the optimum conversions of CH4 and CO2 of ~89% and ~92%, respectively. Furthermore, the incorporation of Rh2O3, in the range of 0.0-4.0 wt.% loading, enhanced DRM and decreased the impact of reverse water gas shift, as inferred by the thermodynamics analysis. TGA revealed that the addition of Rh2O3 diminished the carbon formation on the spent catalysts, and hence, boosted the stability, owing to the potential of rhodium for carbon oxidation through gasification reactions. The 4.0 wt.% Rh2O3 loading gave a 12.5% weight loss of carbon. The TEM images displayed filamentous carbon, confirming the TGA results.

Development and Intensification of the Ethylene Process Utilizing a Catalytic Membrane Reactor.

Ethylene is considered the most important petrochemical constituent in the world today. It is currently produced via the thermal cracking process, which is generally expensive. Ethane dehydrogenation (EDH) is endothermic, and the thermodynamic equilibrium limits its conversion. The present study explores the viability of using a catalytic membrane reactor (MR) for ethylene production from EDH. The removal of hydrogen from the reaction zone using a palladium-silver (Pd-Ag) membrane has led to a high shift in the equilibrium conversion. The effects of operating conditions and reactor configurations on the ethane conversion were investigated. The ultimate ethane conversion was 22.2% when using the MR at 660 K and 300 kPa. The ethane conversion in the shell-side of the reactor increased to ∼99% when benzene hydrogenation was added as an auxiliary reaction in the tube-side of the reactor. Two new processes for ethylene production were developed for an annual capacity of 100,000 metric tons. Cryogenic distillation was required to separate ethylene from ethane if there is no auxiliary reaction. On the other hand, the ethylene process with cyclohexane as a byproduct does not require a refrigeration cycle system, and its economic analysis shows a return on investment of 34.4%, indicating that the process is a promising technology.

Predictive approach of COVID-19 propagation via multiple-terms sigmoidal transition model.

The COVID-19 pandemic with its new variants has severely affected the whole world socially and economically. This study presents a novel data analysis approach to predict the spread of COVID-19. SIR and logistic models are commonly used to determine the duration at the end of the pandemic. Results show that these well-known models may provide unrealistic predictions for countries that have pandemics spread with multiple peaks and waves. A new prediction approach based on the sigmoidal transition (ST) model provided better estimates than the traditional models. In this study, a multiple-term sigmoidal transition (MTST) model was developed and validated for several countries with multiple peaks and waves. This approach proved to fit the actual data better and allowed the spread of the pandemic to be accurately tracked. The UK, Italy, Saudi Arabia, and Tunisia, which experienced several peaks of COVID-19, were used as case studies. The MTST model was validated for these countries for the data of more than 500 days. The results show that the correlating model provided good fits with regression coefficients (R2) > 0.999. The estimated model parameters were obtained with narrow 95% confidence interval bounds. It has been found that the optimum number of terms to be used in the MTST model corresponds to the highest R2, the least RMSE, and the narrowest 95% confidence interval having positive bounds.

Combined organic-inorganic fouling of forward osmosis hollow fiber membranes.

This research focused on combined organic-inorganic fouling and cleaning studies of forward osmosis (FO) membranes. Various organic/inorganic model foulants such as sodium alginate, bovine serum albumin (BSA) and silica nanoparticles were applied to polyamide-polyethersulfone FO hollow fiber membranes fabricated in our laboratory. In order to understand all possible interactions, experiments were performed with a single foulant as well as combinations of foulants. Experimental results suggested that the degree of FO membrane fouling could be promoted by synergistic effect of organic foulants, the presence of divalent cations, low cross-flow velocity and high permeation drag force. The water flux of fouled FO hollow fibers could be fully restored by simple physical cleaning. It was also found that hydrodynamic regime played an important role in combined organic-inorganic fouling of FO membranes.