Noha A.K. Aboul-Gheit

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 Hydrohalogenation of Metal/Zeolite Catalysts for Cyclohexene Hydroconversion II. Rhenium/H-ZSM-5 Catalysts

Abstract A post-preparation treatment of the Re/H-ZSM-5 catalyst with HCl or HF was performed, and its effect on cyclohexene hydroconversion reactions at 50-400 °C in a continuous flow reactor was investigated. The HF treatment significantly improved the catalytic activity for cyclohexene hydrogenation to cyclohexane and methylcyclopentenes to methylcyclopentane in comparison to the HCl treatment. This is principally attributed to the higher Re dispersion and enhancement of the acid site number and strength. Thereupon occurs the highest hydrocracking activity and the lowest dehydrogenation activity for cyclohexene to cyclohexadienes on Re/H-ZSM-5(HF) by virtue of the highest strength of acid sites. The untreated Re/H-ZSM-5 catalyst exhibited the highest dehydrogenation activity for aromatics production, which may be attributed to the lowest quantity of extraframework Al and Si depositing in the pores and cavities of the zeolite support. Industrially, the relative amounts of xylene isomers produced on the hydrohalogenated catalysts are of interest. The amount of p -xylene was higher than m -xylene on the HF-treated catalyst; m - and p -xylenes presented almost equal values on the HCl-treated catalyst; m -xylene exceeded p -xylene on the untreated catalyst. O-xylene was almost equal to the sum of p - and m -xylenes in all cases.

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.

Hydrohalogenation of Platinum–Palladium/H-ZSM-5 Catalysts for n-Hexane Hydroconversion

Catalysts containing 0.3%Pt-, 0.3%Pd-, and 0.3%Pt-0.3%Pd-/H-ZSM-5 were prepared and modified via hydrochlorination or hydrofluorination and tested for n-hexane hydroconversion throughout a reaction temperature range of 250–500°C. Bifunctionality parameters of the current catalysts were characterized via acid site strength distribution by NH3-temperature programmed desorption, metal(s) component dispersion by H2 chemisorption, and temperature programmed reduction. Hydrochlorination was found to leach less structural zeolitic Al in the catalyst than hydrofluorination. HCl modification improved n-hexane hydroisomerization activity, whereas HF treatment was deteriorative via causing pore diffusion restriction by excessively formed debris. Acid sites density and strength were higher on hydrofluorination than on hydrochlorination. Surface area and metals dispersion were higher for hydrochlorinated catalyst but lower for the hydrofluorinated one. Maximum isohexanes production (70%) was realized on hydrochlorinated catalyst at 350°C with 100% selectivity. Crystal unit cell d-spacing, obtained by XRD, was smaller by hydrofluorination than by hydrochlorination, whereas such d-spacing was increased through incorporating Pt and increased more via Pd addition during preparation.

Correlation Between Periodicity and Catalytic Growth Activity of Bimetallic Co-group VI/MgO Catalysts for Production of Carbon Nanotubes by Acetylene Using Chemical Vapor Deposition

This work aims to discover a relationship between the periodicity and catalytic growth activity of carbon nanotubes by acetylene chemical vapor deposition. Hence, the effect of addition of group VI metals (25% of Cr, Mo, or W) of the periodic table to 25 wt% Co supported on MgO has been investigated. The fresh catalysts and carbon nanomaterials were characterized by XRD, TPR, TEM, Raman spectroscopy, BET surface measurements, and TG analysis. The results revealed that the addition of group VI metals induces a strong interaction with the structural MgO crystals associated with an enhancement in surface properties. XRD data shows that the appearance of group VI metal oxides in the diffraction patterns primarily dependent on the corresponding atomic weights. TGA data shows that the Co–W/MgO catalyst exhibited higher carbon nanotubes (CNTs) yield compared to the Co–Cr or Co–Mo containing catalysts. The yield of CNTs increases gradually with increasing the atomic weight of group VI metals (W > Mo > Cr). This finding can be attributed to the higher surface coverage of Co-W/MgO and consequently the larger amount of metal sites which are responsible for the higher yield of MWCNTs compared to the other bimetallic catalysts. The higher metallic surface permits decomposing a larger amount of C2H2 molecules more efficiently. XRD, TEM, and Raman spectroscopic data revealed that highly graphitized MWCNTs were produced over all catalysts under study.

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.

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.

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)

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.

The Production of LPG Using Low-octane Model-feed (n-Hexane) on Modified Unloaded and Pt-loaded MFI Zeolite Catalysts

Nowadays, many developing countries, particularly those non–oil producing ones, suffer from critical shortage of liquefied petroleum gas (LPG) that consists of various mixtures of propane plus butanes (C3H8 + C4H10). In the present communication, n-hexane was used as an n-paraffinic model hydrocarbon to be hydrocracked for LPG production that can be used both as a fuel in domestic heating appliances and also as high-octane gaseous motor fuels. Catalysts containing 0.15%Pt, 0.30%Pt, or 0.60%Pt loaded on H-MFI zeolite, aluminum-deficient MFI (AD-MFI), or hydrofluorinated MFI zeolite (F-MFI) were investigated. Also, the three unloaded modified zeolites were compared as catalysts for n-hexane hydroconversion, whereby the F-MFI catalyst exhibited superior catalytic activity by virtue of acquiring higher acid sites density and strength. The Pt/F-MFI catalysts also enjoy the highest activities by acquiring the highest acid sites density and strength as well as the highest Pt dispersion.