Several Ni-based transition metal carbide catalysts supported on Al-SBA-15 were studied for the hydrothermal decarboxylation of oleic acid and soybean oil to produce diesel range hydrocarbons with no added H 2 . The effect of pre-reduction, sub-critical and super-critical water conditions on the catalyst activity and selectivity was investigated. Both the conversion of oleic acid and selectivity of decarboxylation products under super-critical conditions for each catalyst were about 2-times greater than at sub-critical conditions. In addition, the potential of these catalysts for utilizing aqueous phase reforming (APR) of glycerol for in situ H 2 production to meet process demands was demonstrated. The performance of the catalysts increases with the addition of glycerol, especially for the NiWC/Al-SBA-15 catalyst. With the addition of glycerol, the NiWC/Al-SBA-15 catalyst showed greater conversion of oleic acid and selectivity to heptadecane; however, most of the oleic acid was hydrogenated to produce stearic acid. The highest conversion of oleic acid and selectivity for heptadecane was 97.3% and 5.2%, respectively. Furthermore, the NiWC/Al-SBA-15 catalyst exhibited good potential for hydrolyzing triglycerides (soybean oil) to produce fatty acids and glycerol, and then generating H 2 in situ from the APR of the glycerol produced. A complete conversion of soybean oil and hydrogenation of produced oleic acid were obtained over the NiWC/Al-SBA-15 at super-critical conditions.

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Nickel-based carbide catalysts combined with four different metals (Mo, Nb, W, and Zr) and supported on Al-SBA-15 were investigated for the hydrocracking of distillers dried grains with solubles (DDGS) corn oil to produce biofuels under mild reaction conditions. The effects of the fractional sums of the electronegativities of the transition metals on the catalyst activities, selectivities, and stabilities were investigated. The closer the fractional sum of the transition metal electronegativities was to the electronegativity range of the noble catalysts (2.0-2.2), the better was the catalyst performance. The highest diesel selectivity was obtained from NiWC/Al-SBA-15, with a fractional sum of electronegativity of 2.06. The effects of doping a promoter (Ce) on the catalyst electronegativity and activity were studied. Adding Ce generally improved the catalyst performance, by adjusting the combined electronegativities nearer to 2.0−2.2. However, other parameters affected by Ce addition, such as textural properties, or the performance of individual metals could also impact catalyst performance. The NiNbC/Al-SBA-15 catalyst promoted with 5% Ce maintained stable activity for 168 hrs at 400 °C and 4.48 MPa H 2 .

The hydrocracking of distillers dried grains with solubles (DDGS) corn oil over bimetallic carbide catalysts was explored for green diesel production. A catalyst composed of nickel–tungsten (Ni–W) carbide supported on Al-SBA-15 was designed based on the ability of nickel to adsorb and activate hydrogen and the potential of tungsten for hydrogenation reactions. Four different Ni–W ratios (1:9, 1:1, 2:1, and 9:1) were prepared by the impregnation method to study the effect of metal ratio on the catalyst structure, activity, and selectivity. Catalyst activity was evaluated in a fixed bed reactor at 400 °C and 650 psi (4.48 MPa) with a hydrogen flow rate of 30 mL min–1 and DDGS corn oil flow rate of 0.08 mL min–1. The catalysts showed significant differences in activity and selectivity, with the catalyst having a Ni–W ratio of 9:1 achieving 100% conversion of corn oil and 100% selectivity to diesel for 2 days. Results indicate that by minimizing metal alloy formation and enhancement of the metal dispersion leads to higher activity, selectivity, and durability of the catalysts. A dendrimer-encapsulated nanoparticle (DENP) method was employed to minimize alloy formation and increase the metal dispersion on the support. The catalysts prepared by the DENP method showed activity greater than that of the catalyst prepared by the impregnation method for the hydrocracking of DDGS corn oil.

Super-spreaders of the novel coronavirus disease (or COVID-19) are those with greater potential for disease transmission to infect other people. Understanding and isolating the super-spreaders are important for controlling the COVID-19 incidence as well as future infectious disease outbreaks. Many scientific evidences can be found in the literate on reporting and impact of super-spreaders and super-spreading events on the COVID-19 dynamics. This paper deals with the formulation and simulation of a new epidemic model addressing the dynamics of COVID-19 with the presence of super-spreader individuals. In the first step, we formulate the model using classical integer order nonlinear differential system composed of six equations. The individuals responsible for the disease transmission are further categorized into three sub-classes, i.e., the symptomatic, super-spreader and asymptomatic. The model is parameterized using the actual infected cases reported in the kingdom of Saudi Arabia in order to enhance the biological suitability of the study. Moreover, to analyze the impact of memory index, we extend the model to fractional case using the well-known Caputo–Fabrizio derivative. By making use of the Picard-Lindelöf theorem and fixed point approach, we establish the existence and uniqueness criteria for the fractional-order model. Furthermore, we applied the novel fractal-fractional operator in Caputo–Fabrizio sense to obtain a more generalized model. Finally, to simulate the models in both fractional and fractal-fractional cases, efficient iterative schemes are utilized in order to present the impact of the fractional and fractal orders coupled with the key parameters (including transmission rate due to super-spreaders) on the pandemic peaks.