Browsing by Author "Mohiuddin, Ebrahim"

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    Catalytic cracking of naphtha: The effect of Fe and Cr impregnated ZSM-5 on olefin selectivity
    (Springer Nature, 2018) Mohiuddin, Ebrahim; Mdleleni, Masikana M.; Key, David
    This study focuses on the modification of ZSM-5 in order to enhance the catalytic cracking of refinery naphtha to produce light olefins. ZSM-5 was metal modified using different loadings (0.5–5 wt%) of Fe and Cr via the impregnation method. The metal modified ZSM-5 samples are compared and the effect of metal loading on the physicochemical properties and catalytic performance is investigated. Fe and Cr modification had an effect on both the physicochemical properties of the catalysts as well as catalytic activity and selectivity. Metal loading caused a decrease in the specific surface area which decreased further with increased metal loading. Fe had a greater effect on the total acidity in particular strong acid sites when compared to Cr. The optimum Fe loading was established which promoted selectivity to olefins, in particular propylene. Fe also had a dominant effect on the P/E ratio of which a remarkable ratio of five was achieved as well as enhanced the stability of the catalyst. Cr was found to be a good promoter for selectivity to BTX products with a two-fold increase observed when compared to Fe-modified catalysts.
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    Effective hierarchical ZSM-5 catalysts for the cracking of naphtha and waste tire-derived oil to light olefins
    (John Wiley and Sons Ltd, 2024) Nqakala, Loyiso; Mohiuddin, Ebrahim; Mpungose, Philani; Mdleleni, Masikana
    Hierarchical ZSM-5 zeolite materials with different SiO2/Al2O3 molar ratios in the range of 60–300 were synthesized using soft templating and microemulsion methods to generate zeolite materials with narrow mesopore size distributions. The resulting materials were characterized by X-ray flourescence (XRF), Fourier transform infra-red (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), ammonia temperature programmed desorption (NH3-TPD), thermo-gravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) surface area measurements, and products from the catalytic tests were analyzed by gas chromatography (GC). The XRF analysis determined that the Si/Al ratios for the synthesized ZSM-5 were close to the batch ratios. The XRD and FTIR results revealed that the synthesized samples had crystalline ZSM-5 zeolite structures. The small angle observed from the XRD patterns confirmed the presence of mesopores in the structure of the prepared materials. The SEM results showed that the ZSM-5 synthesized materials had different morphologies and particle sizes, as well as worm-like holes indicating that some macropores with average pore sizes ranging between 68 and 85 nm were successfully generated in these materials. NH3-TPD results showed that the total acidity of the prepared materials decreased with an increase in the Si/Al (SA) ratio following this trend: SA = 71 > 177 > 345. This may be due to the decrease in the aluminum content, which is largely responsible for the formation of acidic sites in zeolites.
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    Hydrothermal synthesis of hierarchical ZSM-5 with different Si/Al ratio and their evaluation as catalysts in the catalytic cracking of hexane
    (University of Western Cape, 2021) Nqakala, Loyiso Clemence; Mdleleni, Masikana; Mohiuddin, Ebrahim; Mpungose, Philani Perfect
    Ethylene and propylene are greatly used for their importance as feedstocks for producing useful materials. Due to rise in prices and the demand of ethylene and propylene, the need to increase the selective production of these light olefins is necessary. To achieve this, zeolites, specifically ZSM-5 has been used to investigate catalytic cracking of several types of hydrocarbons for the production of these light olefins. This study focuses on developing hierarchical macro and/or mesoporous ZSM-5 zeolites with variable Si/Al ratios. The synthesized materials were then evaluated on their performance via catalytic cracking of hexane, dodecane and tyre derived oil [TDO] to produce light olefins, particularly ethylene and propylene.