Nguyen Le-Phuc

A cheap, environmentally friendly, easily scalable post-treatment of Na-ZSM-5 (Si/Al molar ratio = 20 or 30) via electron-beam irradiation to produce hierarchical H-ZSM-5 as a propylene-increasing fluid catalytic cracking additive was performed. Higher specific surface areas and highly accessible porous systems were obtained among the irradiated samples. A combination of ²⁷Al, ¹H magic angle spinning nuclear magnetic resonance and NH₃-temperature-programmed desorption methods showed that upon irradiation, some of the framework’s tetrahedral Al atoms were removed as non-framework Al atoms via flexible coordination with Si-OH groups (either framework or non-framework defects), thus increasing the H-ZSM-5 acidity and stability during hydrothermal dealumination. The enhanced selectivity and stability toward propylene production over the irradiated H-ZSM-5 samples were attributed to the integration of the reserved population of medium acid sites into the highly accessible hierarchical network. N₂ adsorption–desorption isotherm data showed that the Si-rich H-ZSM-5 samples possessed an obvious ink-bottle-shaped micro-mesopore network and a greater degree of disordered orientation of the straight pore systems toward the exterior surfaces. Micro-activity test data suggested that with an increasing Si/Al ratio, the H-ZSM-5 additives lost some extent of their cracking activity due to the constricted hierarchical pore network toward the exterior surface but gained more stability and selectivity for propylene due to the reserved medium acid sites.

In this study, a promising monolithic catalyst composition for the production of syngas using bi-reforming (BRM) of CH₄–CO₂ mixture was proposed. The BRM performance was evaluated with N₂/CH₄/H₂O/CO₂ (1/1/0.8/0.4) mixture at 700–800 °C. First, the influence of MgO loading on the activity of 10 wt.% of Ni supported on xMgAl (x is MgO content, x = 10–40 wt.%) powder catalyst was studied. The addition of 10–20 wt.% of MgO leads to higher reforming performance, probably due to the formation of MgAl₂O₄ phase that enhance the Ni dispersion. At 800 °C, the CH₄ conversion and H₂ yield obtained with Ni/20MgAl are 1.7 and 1.5 times, respectively, higher than that of the Ni/Al catalyst. However, higher MgO loading causes a coverage of Ni active sites and decrease activity. Ni/20MgAl powder catalyst exhibit highest activity and this sample was then deposited on monolith substrate. The monolith catalyst shows higher BRM activity than powder form. Long-term test demonstrates high stability of monolith catalyst with less than 5% the losses in CH₄ and CO₂ conversions after 60 h time on stream. CH₄ and CO₂ conversion are 89% and 81%, respectively. The H₂/CO ratio is near 2, which meets the requirement for methanol/Fischer–Tropsch fuel synthesis.

The direct cracking of Bach Ho crude oil, having API gravity of 41°, over equilibrium FCC catalyst (Ecat), modified FCC catalyst (HT-FCC) and ZSM-5 additive were studied at 620–650 °C using short-contact-time micro activity testing unit. HT-FCC catalyst was prepared by the treatment of Ecat with oxalic acid in reflux condition. This treatment largely improves the porosity while keeping the particle size of Ecat. Hence, it leads to an important enhancement in catalytic cracking activity. Due to high activity of HT-FCC catalyst, the direct cracking of crude oil can be performed at a low catalyst-to-oil ratio (C/O) which helps to decrease the yield of dry gas. At 620–650 °C, C/O of 1.5–2.5, 18–23 wt.% of light olefins, 3–6 wt.% of dry gas together with 51–59 wt.% of gasoline yields can be obtained with HT-FCC catalyst. ZSM-5 addition favors the conversion of gasoline to light olefins. Compared to the results reported in literature, the use of HT-FCC and ZSM-5 catalysts at 650 °C, low C/O of 1.5 shows promising performances: (i) much lower dry gas yield (8%), (ii) high light-olefins yield (32%) while maintaining high gasoline yield (43%), and (iii) high BTXs content in gasoline (45%).

The influences of La addition on the properties and the performance of xLa/ZSM-5 additives with various La loading (x is molar ratio of La/Al, x = 0.25-1) for vacuum gasoil (VGO) cracking reactions were studied. Samples were deactivated via steaming treatment with 100% steam, 20 hours, 816 °C. The highest promoting effect was obtained with 0.25La sample. The higher La loadings decrease the enhancement effect of La. XRD, BET and NH₃-TPD results demonstrated that the use of low La³⁺ concentration solution during La addition step could lead to a better interaction of La³⁺ with ZSM-5 framework and increase the promoting effect.