Molybdenum Nitrides, Carbides and Phosphides as Highly Efficient Catalysts for the (hydro)Deoxygenation Reaction

Bulk Molybdenum and Tungsten Phosphides for Selective Phenol Production from Guaiacol

Bulk MoP and WP were investigated and compared in guaiacol hydrodeoxygenation to phenol. The catalysts obtained were studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and temperature-programmed desorption of NH₃ (NH₃-TPD) analyses. MoP was shown to be more active than WP. However, WP was more selective in phenol production. Guaiacol conversion using MoP was 90-98%. The highest selectivity for phenol was 66% (340 °C). By increasing the temperature to 380 °C, phenol selectivity decreased to 31%, while selectivity for cyclohexane increased to 29%. Thus, MoP was active not only in hydrodeoxygenation but also in hydrogenation. Guaiacol conversion over WP was 53-90%. The highest selectivity for phenol was 84% (380 °C). Hydrogenation products were also detected but with low selectivity. Thus, WP was active in the partial hydrodeoxygenation of guaiacol and was more suitable for the selective production of phenol than MoP. It was shown that after a 30 h recycling test, the activity of MoP did not decrease (1st and 5th cycle conversion value was 91%), while the activity of WP reduced (1st and 5th cycle conversion values were 81 and 64%, respectively). However, the activity of both catalysts at average conversion values decreased. Selectivity for phenol remained unaltered over both catalysts. It was supposed that catalyst activity decreased due to partial destruction of the crystalline phosphide phase and the surface phosphide oxidation to phosphate.

Utility of NaMoO3F as a Precursor for Homogeneous Distribution of Cobalt Dopants in Molybdenum Oxynitrides

Molybdenum nitrides and their related compounds have been focused as a catalyst for several reactions. Although the doping into molybdenum nitrides lead to the higher catalytic activity, the simultaneous control of the morphology, the crystallinity, and the dopant state in doped MoN cannot be easily achieved due to the limitation of the synthesis method. In this study, one of the mixed anion compounds, NaMoO 3 F was used as a precursor for molybdenum oxynitrides with hexagonal MoN phase. This route led to the homogeneous distribution of cobalt in the molybdenum oxynitride compared with that obtained by the other method. The cobalt-doped molybdenum oxynitride from NaMoO 3 F exhibited high oxygen reduction reaction catalytic activity due to the high distribution of cobalt in the crystal. This paper proposes that the mixed anion compounds can be a unique precursor for the other materials to expand the controllability of materials toward improvement of their activity.

Hydrocracking optimization of palm oil to bio-gasoline and bio-aviation fuels using molybdenum nitride-bentonite catalyst

In this study, molybdenum nitride-bentonite was successfully employed for the reaction of hydrocracking of palm oil to produce a bio-gasoline and bio-aviation fuel. The prepared catalyst was characterized using XRD, FT-IR, and SEM-EDX. The acidity of the catalyst was determined using the pyridine gravimetric method. The result showed that the acidity of bentonite was increased after modification using molybdenum nitride. The hydrocracking study showed that the highest conversion and product fraction of bio-gasoline and bio-aviation fuel were exhibited by molybdenum nitride-bentonite 8 mEq g⁻¹. The catalyst was later used to optimize the hydrocracking process using RSM-CCD. The effects of the process variables such as temperature, contact time, and catalyst to feed ratio, on the response variables, such as conversion, oil, gas, and coke yield, were investigated. The analysis of variance showed that the proposed quadratic model was statistically significant with adequate precision to estimate the responses. The optimum conditions in the hydrocracking process were achieved at a temperature of 731.94 K, contact time of 0.12 h, and a catalyst to feed ratio of 0.12 w/v with a conversion of 78.33%, an oil yield of 50.32%, gas yield of 44.00% and coke yield of 5.73%. The RSM-CCD was demonstrated as a suitable method for estimating the hydrocracking process of palm oil using a MoN-bentonite catalyst due to its closeness to the optimal value of the expected yield. This study provided a potential catalyst of based on bentonite modified using molybdenum nitride for the hydrocracking of palm oil.

In this study, molybdenum nitride-bentonite was successfully employed for the reaction of hydrocracking of palm oil to produce a bio-gasoline and bio-aviation fuel.

Hydrotreating of Atmospheric Gas Oil and Co-Processing with Rapeseed Oil Using Sulfur-Free PMoCx/Al2O3 Catalysts

Sulfur-free molybdenum carbides have the potential to replace the conventional sulfided catalysts used for hydrotreating. For these catalysts, it is not necessary to add sulfur to maintain their activity. This fact makes it worthwhile to continue working on improving their hydrotreating efficiency. According to our previous studies, the addition of Co or Ni promotes the hydrotreating activity, but only significant in the case of hydrodesulfurization efficiency (up to 30%). To increase the hydrodenitrogenation efficiency, other promoters, such as phosphorus, can be added. However, most of the published studies do not focus on co-processing or only on hydrotreating of gas oil model molecules at a laboratory scale. In this paper, we build on our previous research by studying five sulfur-free phosphorus-modified MoCx/Al₂O₃ catalysts (0.5, 1.5, 2.5, 3.5, and 4.5 wt %) for the hydrotreating of atmospheric gas oil and co-processing with rapeseed oil (5, 10, and 25 wt %) under industrial conditions (330-350 °C, 5.5 MPa, WHSV 1-2 h^-1). A phosphorus content up to 1.5 wt % promoted the hydrodesulfurization (5-10%) and the hydrodenitrogenation (10-25%) efficiencies of catalysts. Moreover, the triglycerides addition did not significantly decrease the catalyst activity during co-processing. Therefore, our results enable us to define the range of phosphorus addition that enhances MoCx activity using industrial conditions and commercial feedstocks, pointing the way to develop a suitable and sulfur-free alternative to conventional hydrotreating catalysts.