D. S. El-Desouki

Hydroisomerization of n-Hexane Using Unloaded and Low-Platinum-Loaded H-ZSM-5 and H-MOR Catalysts

Abstract The applicability for investing and comparing two zeolites (H-ZSM-5 and H-MOR) as supports for low-platinum (less expensive) catalysts used principally for hydroisomerization of n-paraffins in light petroleum naphtha is investigated using n-hexane as a model n-paraffin feed at temperatures of 250°C–500°C in a flow-type reactor with a hydrogen flow of 20 cm3 min−1 at atmospheric pressure. H-ZSM-5 zeolite acquires higher density of strong acid sites, which are still somewhat weaker than the respective sites in H-MOR. These milder sites in H-ZSM-5 zeolite enhanced hydroisomerization and dehydrocyclization but suppressed hydrocracking after incorporating 0.15% Pt. Hydrochlorination (HCl) and hydrofluorination (HF) of 0.15% Pt/H-ZSM-5 were carried out to modify its acidity and Pt dispersion with the goal of maximizing n-hexane hydroisomerization. The HCl treatment seems to have significantly approached the requirement for optimum catalytic bifunctionality, whereas HF treatment appears mostly deteriorative.

Direct Conversion of Natural Gas to Petrochemicals Using Monofunctional Mo/SiO2 and H-ZSM-5 Zeolite Catalysts and Bifunctional Mo/H-ZSM-5 Zeolite Catalyst

Abstract The components of the standard catalyst globally used for natural gas direct conversion (6% Mo/H-ZSM-5) have been separately prepared and examined to represent: (a) monofunctional metallic component (6% Mo/SiO2) and (b) acidic component (H-ZSM-5 zeolite) to numerically investigate the extent of activity of each catalytic component in comparison to the activity of the standard catalyst in a fixed-bed flow-type reactor. The temperature and gas hourly space velocity are 700°C and 1500 mLg−1 h −1, respectively, which are very close to those used in the industrial gas conversion reactions. Time on stream up to 240 min was examined. The gaseous products were ethylene, propylene, and hydrogen, whereas the liquid products were benzene, toluene, and naphthalene. Carbon was also produced as deposited particles on the catalyst.

Nanosized Platinum-Loaded H-ZSM-5 Zeolite Catalysts for n-Hexane Hydroconversion

Abstract A series of nanosized platinum-containing catalysts was successfully loaded on/in zeolite H-ZSM-5 via exchanging the zeolitic proton with platinum from Pt tetramine dichloride complex. Another series of Pt/H-ZSM-5 catalysts was prepared via wet impregnation of H2PtCl6 solution for comparison. The latter series was found to produce lower Pt dispersion. Pt dispersion was determined by H2 chemisorption. Catalyst characterization via ammonia temperature-programmed desorption (TPD), temperature-programmed reduction (TPR), and transmission electron microscopy (TEM) was examined for all catalysts and showed large differences in particle sizes. The data on n-hexane reactions of the catalysts of both series confirmed the formation of Pt nanoparticles in the exchanged catalysts. The relatively lower density and strength of acid sites acquired by Pt-exchanged catalysts contributed to this difference; stronger acid sites in the impregnated catalysts are in favor of hydrocracking reactions, which inhibit isomerization selectivity.

n-Pentane Hydroconversion Using Pt-loaded Zeolite Catalysts

Abstract Pt/H-ZSM-5 and Pt/H-MOR catalysts with different Pt contents were prepared via impregnation using H2PtCl6 · 6H2O or via exchange using Pt(NH3)4Cl2, calcination in air at 530°C and reduction in H2 at 500°C. The prepared catalysts were tested for n-pentane hydroisomerization and hydrocracking via bifunctionality at 250–500°C using a micro-catalytic pulse reactor. It is found that the dispersion of Pt-exchanged zeolites is higher than the corresponding Pt-impregnated zeolites at all Pt contents. It is also found that the dispersion of Pt/H-ZSM-5 catalysts either exchanged or impregnated are higher than the corresponding Pt/H-MOR catalysts. Temperature-programmed desorption (TPD) data showed that the impregnated catalysts possess a higher acid sites number than the exchanged catalysts; and that the Pt/H-ZSM-5 catalysts have a higher number of acid sites than do the Pt/H-MOR catalysts, whereas the latter catalysts possess higher strength of acid sites at all Pt contents. The hydroisomerization activities using Pt exchanged catalysts, supported either on H-ZSM-5 or H-MOR, are higher than the impregnated catalysts at almost all Pt contents. It is also concluded that the H-ZSM-5-supported catalysts, either exchanged or impregnated, are more active than the H-MOR supported ones. Hydrocracking is higher using all loaded H-MOR catalysts.

Effect of Novel Quercetin Titanium Dioxide-Decorated Multi-Walled Carbon Nanotubes Nanocomposite on Bacillus subtilis Biofilm Development

The present work was targeted to design a surface against cell seeding and adhering of bacteria, Bacillus subtilis. A multi-walled carbon nanotube/titanium dioxide nano-power was produced via simple mixing of carbon nanotube and titanium dioxide nanoparticles during the sol-gel process followed by heat treatment. Successfully, quercetin was immobilized on the nanocomposite via physical adsorption to form a quercetin/multi-walled carbon nanotube/titanium dioxide nanocomposite. The adhesion of bacteria on the coated-slides was verified after 24 h using confocal laser-scanning microscopy. Results indicated that the quercetin/multi-walled carbon nanotube/titanium dioxide nanocomposite had more negativity and higher recovery by glass surfaces than its counterpart. Moreover, coating surfaces with the quercetin-modified nanocomposite lowered both hydrophilicity and surface-attached bacteria compared to surfaces coated with the multi-walled carbon nanotubes/titanium dioxide nanocomposite.

High Yields of LPG Via n-Hexane Hydrocracking Using Unloaded Acidic Zeolite Catalysts

This work includes investigating the hydrocracking of n-hexane, as a low-octane naphtha component to high-octane gaseous motor fuel (LPG) in a pulse flow atmospheric microreactor using untreated and steam-treated H-MOR, H-BEA, or H-ZSM-5 zeolite catalysts. All zeolites were metal-free and their bifunctionality depended only on the Brønsted zeolitic acid sites. The temperature programmed desorption analysis was performed to compare the weak and strong acid sites in the current catalysts. The catalytic activities of the catalysts were found to correlate well with their acid strengths. The most active catalyst was St-H-MOR, which acquired the strongest acid sites and highest densities. On this catalyst, 92.1% LPG was produced at 350°C, whereas on the un-steamed one (H-MOR), the LPG yield amounted to 88.0% at the same temperature. Maximum LPG production on H-BEA acquired 84.6% at 400°C, whereas on St-H-BEA, it acquired a close yield (85.7%). Zeolites H-ZSM-5 and St-H-ZSM-5 acquire very low catalytic activities mainly due to their narrow pore structure, as well as due to their partial pore filling by Al debris in case of St-H-ZSM-5.

Reactions of Cyclohexane on Platinum, Palladium, or Iridium-loaded H-ZSM-5 Zeolite Hydrohalogenated Catalysts

Abstract The catalytic hydroconversion of cyclohexane using catalysts containing H-ZSM-5 zeolite loaded with 0.35 wt% platinum, palladium, or iridium was studied in a pulse-type microreactor/GC system at atmospheric pressure. These catalysts were also either doped with 3.0% of HCl or HF. The activities of these catalysts and the distribution of the products formed were found to depend on the dispersion of the metallic component as well as on the acidity, acid sites number, and strength in the catalysts. TPD of ammonia and hydrogen chemisorption were applied to evaluate acid site strength distribution and metals dispersion, respectively, in the catalysts. In case of the Pt- and Pd-containing catalysts, hydrochlorination enhanced the isomerization and dehydrogenation activities and selectivities of cyclohexane, but decreased its hydrocracking activity. However, catalyst hydrofluorination resulted in the reverse effects. Nevertheless, for the Ir-loaded catalyst, both hydrohalogenation treatments decreased the isomerization and dehydrogenation of cyclohexane. The Ir/H-ZSM-5 catalyst exhibited higher hydrogenolysis activities than did those acquired by the Pt- and Pd-containing catalysts.

Photocatalytic degradation of TNT in wastewater using Fe doped TiO2 nanoparticles

Catalysts Characterization Laboratory, Petroleum Refining Division, Egyptian Petroleum Research Institute (EPRI), 1 Ahmed El Zomour St., Nasr City, PO Box 11727, Cairo, Egypt, Tel. +20 2 22736349; Fax +20 2 22747433; emails: sehamshaban@yahoo.com (S.A. Shaban), saharahmed92@hotmail.com (S.M. Ahmed), doaadesouki@hotmail.com (D.S. El-Desouki), nohaaboulgheit@yahoo.com (N.A.K. Aboul-Gheit), samiraepri@hotmail.com (S.M. Abdel-Azim)