Saheed A. Ganiyu

Simultaneous HDS of DBT and 4,6-DMDBT over single-pot Ti-SBA-15-NiMo catalysts: influence of Si/Ti ratio on the structural properties, dispersion and catalytic activity

A series of Ti-SBA-15-NiMo catalysts with Si/Ti ratios of 1, 2.5, 5, and 10 were prepared by a single-pot method. The dispersion and performance of the catalysts were characterized by N2 adsorption, temperature programmed techniques (NH3-TPD and H2-TPR), X-ray diffraction (XRD), and X-ray fluorescence (XRF) as well as by Raman and Fourier transform infrared (FTIR) spectroscopy. The catalytic activity was determined by simultaneous hydrodesulfurization (HDS) of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) in a batch autoclave reactor. Variations in the Si/Ti ratio resulted in noticeable differences in the characteristics of the catalysts. XRD diffractograms show that Ti is well incorporated into the SBA-15 support at Si/Ti ratios of 10 and 5. However, at Si/Ti ratios below 5, the Ti phases predominate and peaks corresponding to MoO3 phases were not observed. As the Ti incorporation is increased, the moderate surface acidity decreases while the contribution from strong acidity becomes evident. TPR results indicate that a higher amount of Ti increases the metal-support interaction. The HDS rates for DBT and 4,6-DMDBT over a catalyst with an Si/Ti ratio of 10 increased by 33% and 49%, respectively. The enhancement in HDS can be attributed to a lower metal-support interaction. However, a further increase in the Si/Ti ratio removed the enhancement in the HDS rates. A regenerated catalyst with an Si/Ti ratio of 10 exhibited 91% and 86% HDS compared to the fresh catalyst for DBT and DMDBT, respectively. Direct desulfurization was the preferred route for both DBT and 4,6-DMDBT. The HDS rate for DDS is enhanced by the addition of Ti while the HDS rate for the hydrogenation route remains almost constant. The divergent effects on the DDS and HYD pathways indicate that the active sites for hydrogenolysis and hydrogenation are different and are influenced differently by titania addition.

4-phenyl-1,2,3-triazole functionalized mesoporous silica SBA-15 as sorbent in an efficient stir bar-supported micro-solid-phase extraction strategy for highly to moderately polar phenols

A simple and effective strategy for the extraction of highly to moderately polar phenols in water samples was developed by synthesizing a series of 4-phenyl-1,2,3-triazole functionalized SBA-15 sorbents (xN3-Ph-SBA-15; x = 2 - 10 wt%) via two steps: azide functionalization of SBA-15 and its click reaction with phenylacetylene. The formed sorbents, which have a blend of both polar (1,2,3-triazole) and non-polar (long chain alkyl groups) sites were characterized using magic angle spinning NMR, surface area, pore size/pore volume N2 adsorption-desorption isotherms, scanning electron microscopy, and Fourier transform infrared spectroscopy. The surface area and pore size/pore volume were seen to decrease with increasing loading of 4-phenyl-1,2,3-triazole. The sorbents were used in a stir bar-supported micro-solid-phase extraction (SB-µ-SPE) for seven selected phenols in 10 mL water samples, and in combination with gas chromatography - mass spectrometry (GC-MS). A wide number of parameters were studied in the method optimization: 10N3-Ph-SBA-15 was the best sorbent which performed better using 20 mg dosage; 15 min extraction time; 300 µL of ethyl acetate as desorption solvent, 20 min desorption time; and ionic strength set at 0.5 g NaCl. The approach provided the desired linearity range for all tested phenols with R2 value up to 0.9989 and detection limit (LOD) of 0.23-0.37 ng mL-1. Relative standard deviation (RSD) and relative recovery experiments were tested using phenols spiked at 1, 100 and 400 ng mL-1. RSD values were calculated in the range of 2.3-7.5% and the relative recoveries in the wastewater matrix successfully presented a range of 88.5-99.2%.