Sameh M. Aboul-Fotouh

Production of dimethylether （DME） as a clean fuel using sonochemically prepared CuO and/or ZnO-modified γ-alumina catalysts

Abstract The catalytic conversion of methanol to dimethylether (DME) was studied over CuO/Al2O3, ZnO/Al2O3 and ZnO-CuO/Al2O3 nanocatalysts prepared in presence or absence of ultrasonic irradiation. The catalysts were characterized by X-ray diffraction (XRD), surface characterization method (BET), scanning electron microscope (SEM), H2-temperature programmed reduction (H2-TPR) and temperature programmed desorption of ammonia (NH3-TPD). The experimental results show that during catalytic dehydration of methanol to dimethylether, the activities of the CuO/Al2O3, ZnO/Al2O3 and ZnO-CuO/Al2O3 catalysts prepared using ultrasonic treatment are much higher than those prepared in absence of ultrasonication. SEM shows that the use of ultrasonication results in much smaller nanoparticles. BET and XRD show that the ultrasonication increases the surface area and pore volume of the catalysts. H2-TPR profiles indicated that reducibility of the sonicated nanocatalysts is carried out at lower temperatures. NH3-TPD shows that ultrasound irradiation has enhanced the acidity of the nanocatalyst and hence enhanced catalytic performance for DME formation.

Conversion of Methanol Using Modified H-MOR Zeolite Catalysts

Abstract The conversion of methanol was carried out over various mordenite zeolite catalysts to evaluate their catalytic performance. A post-preparation treatment of the H-MOR catalyst by halogenation with NH4Cl or NH4F and by hydrohalogenation with HCl or HF was carried out and its effect on methanol conversion reactions at 100–300 °C in a continuous flow reactor was investigated. The as-synthesized H-mordenite (H-MOR) is generally more active during dimethyl ether (DME) production than the NH4-MOR and Na-MOR. Fluorinated treatment with HF or NH4F significantly improved the catalytic activity during methanol conversion and the formation of DME in comparison to chlorinated treatments with HCl or NH4Cl. This is principally attributed to the higher Si/Al ratio and an increase in the number of acid sites and their strength. Halogenation treatment with the acids of F− or Cl− gave the highest conversion activity for DME production compared to halogenation treatments with the salts of the same halogens. Zeolite dealumination by the acids was more profound than that by the halogen ion salts, which resulted in a decrease in the crystallinity and crystallite sizes of the zeolite.

Effect of ultrasonic irradiation and/or halogenation on the catalytic performance of γ-Al2O3 for methanol dehydration to dimethyl ether

Abstract Dimethyl ether (DME) is amongst one of the most promising alternative, renewable and clean fuels being considered as a future energy carrier. In this study, the comparative catalytic performance of the halogenated γ-Al 2 O 3 prepared from two halogen precursors (ammonium chloride and ammonium fluoride) is presented. The impact of ultrasonic irradiation was evaluated in order to optimize both the halogen precursor for the production of DME from methanol in a fixed bed reactor. The catalysts were characterized by SEM, XRD, BET and NH 3 -TPD. Under reaction conditions where the temperature ranged from 200 to 400°C with a WHSV =15.9 h −1 was found that the halogenated catalysts showed higher activity at all reaction temperatures. However, the halogenated alumina catalysts prepared under the effect of ultrasonic irradiation showed higher performance of γ-Al 2 O 3 for DME formation. The chlorinated γ-Al 2 O 3 catalysts showed a higher activity and selectivity for DME production than fluorinated versions.

Methanol conversion to DME as a blue fuel：The beneficial use of ultrasonic irradiation for the preparation of CuO/H-MOR nanocatalyst

Abstract Methanol conversion to DME was investigated over CuO/H-MOR nanocatalyst prepared by precipitation and/or by precipitation flowed by ultrasonic irradiation methods. BET, XRD, SEM, NH 3 -TPD and H 2 -TPR techniques were used to characterize nanocatalysts. The effective ultrasonication factors encountered during carrying out the dehydration of methanol on CuO/H-MOR zeolite catalysts to produce dimethylether are studied in the present work. These factors include: the type of ultrasonication media, the ultrasonication time, and the fixed weight of the solid catalyst per the volume of the ultrasonication liquid media ( W catalyst / V liquid ratio). XRD showed that structure of H-MOR is not damaged even after it is loaded with CuO nanoparticles or with ultrasonication. H 2 -TPR profiles indicated that reducibility of sonicated CuO/H-MOR nanocatalyst is higher than non-sonicated catalyst. It is found that employing ultrasound energy for 60 min has the highest influence on the surface properties of nanocatalyst and its catalytic performance (activity and stability) of CuO/H-MOR catalyst. Surface morphology (SEM) of the sonicated CuO/H-MOR catalysts have clarified that methanol by itself used as an ultrasonication medium gives the best results concerning the homogeneity of particle sizes compared to the non-sonicated catalyst, where large agglomerates and non-homogeneous clusters appeared. Water used as a sonication medium showed many large agglomerates in addition to some smaller particles resulted in low catalytic activity. The different alcohols and ( W catalyst / V liquid ) ratio were examined to give precise correlation with the catalytic activity of the sonicated CuO/H-MOR zeolite catalyst. These findings certified that ultrasonication has a deep effect on the surface morphology and hence on the catalytic behavior of the dehydration of methanol to DME. NH 3 -TPD shows that ultrasound irradiation has enhanced the acidity of CuO/H-MOR catalyst and hence its catalytic performance for DME formation.

Effect of Hydrohalogenation of PtRe/H-ZSM-5 for Cyclohexene Conversion

Extended use of supported Pt catalysts causes thermal migration of Pt particles to form large agglomerates, thus decreasing the catalytic activity. The combination of Pt with Re protects Pt against migration. In addition, Cl− injection into the reactor assists Pt particles redispersion to prolong catalyst life. In this work, a PtRe/H-ZSM-5 catalyst was treated with either HCl or HF to investigate their role in activating or deactivating the catalyst. The conversion exceeded 90% in the whole temperature range with the PtRe/H-ZSM-5(HCl) catalyst, and its activity for the direct isomerization of cyclohexene to methylcyclopentenes (MCPEs) was the lowest but the activity for the hydrogenation of the MCPEs to methylcyclopentane was the highest. The reactivities of MCPEs and cyclohexadienes on the catalysts were similar because both are dehydrogenation reactions. Benzene production was significantly higher on the hydrochlorinated catalyst than on the other catalysts, and its hydrocracking activity was the lowest, which is a good characteristic for processing catalysts where cracking is undesired.

Dimethyletherproduction on zeolite catalysts activated by Cl−, F− and/or ultrasonication

Abstract The chlorinated and fluorinated zeolite catalysts were prepared by the impregnation of zeolites (H-ZSM-5, H-MOR or H-Y) using two halogen precursors (ammonium chloride and ammonium fluoride) in this study. The influence of ultrasonic irradiation was evaluated for optimizing both halogen precursors for production of dimethylether (DME) via methanol dehydration in a fixed bed reactor. The catalysts were characterized by SEM, XRD, BET and NH 3 -TPD. The reaction conditions were temperatures from 100 to 300°C and a WHSV =15.9 h −1 . All halogenated catalysts show higher catalytic activities at all reaction temperatures studied. However, the halogenated zeolite catalysts prepared under ultrasonic irradiation show higher performance for DME formation. The chlorinated zeolite catalysts show higher activity and selectivity for DME production than the respective fluorinated versions.

Effect of the Si/Al ratio of HZSM-5 zeolite on the production of dimethyl ether before and after ultrasonication

Abstract A series of as-synthesized HZSM-5 zeolites with different Si/Al ratios (25, 90, 120, 240 and 400) were post-treated by ultrasonication for an optimum time of 60 min. The morphology, acidity and textural properties of HZSM-5 were characterized with XRD, SEM, N2 adsorption and NH3-TPD techniques. The catalytic performance was evaluated by dehydration of methanol to dimethyl ether (DME), which is a promising gaseous automotive fuel in future. It was found that the Si/Al ratio of HZSM-5 had considerable impacts on its catalytic performance for dehydration of methanol to DME. Its activity increased with decreasing Si/Al ratio from 400 to 25. Ultrasonication of HZSM-5 could significantly improve its catalytic performance.