ZSM-5 is a highly active and stable catalyst for the conversion of biomass to fuels and bio-oil.zsm-5 catalyst However, the presence of oxygenates in the produced bio-oil hinders its direct use as a fuel in internal combustion engines [49]. The occurrence of these oxygenated compounds can be minimized by the introduction of nickel to the catalytic surface of the zeolite. This has the potential to improve the selectivity of shape-selective cracking and thereby enhance the production of light alkanes from bio-oil.
The formation of coke deposits on the catalytic surface is one of the major challenges during the pyrolysis of biomass to produce bio-oil and biofuels.zsm-5 catalyst This deactivation is attributed to the hindrance of volatile vapours through the pores of the zeolite and consequently to its dealumination [50]. The removal of these carbon materials from the pore system of the zeolite is crucial to its reusability and catalytic performance.
Various studies have reported that the addition of nickel to the zeolite surface results in improved selectivity and stability during the methanol-to-olefins conversion reaction.zsm-5 catalyst The effect of the methanol/toluene feed composition on these selectivities has also been investigated. The presence of oxygenates leads to the activation of the ligands and thereby the deactivation of the catalyst [51]. The introduction of nickel has been shown to improve the activity of the ZSM-5 zeolite for butene cracking by suppressing the formation of coke.
To investigate the effect of the Na bulk concentration on methanol-to-olefins selectivity, a series of crystalline ZSM-5 samples with different sodium bulk content were prepared.zsm-5 catalyst Their physisorption properties were assessed in liquid nitrogen. The samples with higher crystallinity showed the best conversion and selectivity toward light olefins. The morphology and mesoporous/micropore volume of the samples were also evaluated using 29Si and 27Al NMR spectroscopy.
The preparation of the monometallic and bimetallic ZSM-5 based catalysts was carried out by the impregnation method.zsm-5 catalyst In the case of the monometallic catalyst, 50 g of protonated ZSM-5 was mixed with ammonium nitrate solution (2 mol L-1) and heated at 80 degC for 1 h. Then 100 mL of a Ni nitrate solution (1 mol L-1) was added and stirred for another hour. The resultant catalysts were characterized by scanning electron microscopy (SEM) and nuclear magnetic resonance spectroscopy (NMR).
Both monometallic and bimetallic catalysts exhibited similar physicochemical properties, but the monometallic catalyst had a lower acidity index than the bimetallic catalyst.zsm-5 catalyst The monometallic catalyst also had a larger mesoporous volume than the bimetallic catalyst.
Both monometallic and bimetallic ZSM-5-based catalysts demonstrated high conversion and selectivity during the n-octane hydroconversion reaction. However, the monometallic catalyst had a slower reaction rate than the bimetallic one. Moreover, the bimetallic catalyst exhibited better stabilization during the reaction and a longer time-on-stream. The results of this study highlight that the acidity of the Ni/ZSM-5 based bimetallic catalyst is essential for improved activity and stability. Furthermore, the morphology and mesoporous volume of the sample are crucial to the n-octane conversion process.
