Abdulrahim A. Al-Zahrani

New spectral techniques for systems of fractional differential equations using fractional-order generalized Laguerre orthogonal functions

Fractional-order generalized Laguerre functions (FGLFs) are proposed depends on the definition of generalized Laguerre polynomials. In addition, we derive a new formula expressing explicitly any Caputo fractional-order derivatives of FGLFs in terms of FGLFs themselves. We also propose a fractional-order generalized Laguerre tau technique in conjunction with the derived fractional-order derivative formula of FGLFs for solving Caputo type fractional differential equations (FDEs) of order ν (0 < ν < 1). The fractional-order generalized Laguerre pseudo-spectral approximation is investigated for solving nonlinear initial value problem of fractional order ν. The extension of the fractional-order generalized Laguerre pseudo-spectral method is given to solve systems of FDEs. We present the advantages of using the spectral schemes based on FGLFs and compare them with other methods. Several numerical example are implemented for FDEs and systems of FDEs including linear and nonlinear terms. We demonstrate the high accuracy and the efficiency of the proposed techniques.

Hydrogen production by ammonia decomposition using high surface area Mo2N and Co3Mo3N catalysts

High surface area bulk molybdenum nitride catalysts were synthesized via temperature-programmed ammonolysis of an ammonium heptamolybdate and citric acid (CA) composite. The synthesized materials were tested for COx-free H2 production via ammonia decomposition for fuel cell application. Cobalt was added at different loadings (1, 3, and 5 wt%) as a promoter for the bulk molybdenum nitrides. The chemical composition and surface morphology of the nitride catalysts were studied by means of XRD, XPS, SEM-EDAX and TEM techniques. Addition of cobalt increased the formation of the γ-Mo2N phase and cobalt existed as the Co3Mo3N phase, which was uniformly distributed over Mo2N as evidenced by TEM and SEM analyses. A drastic increase in Mo2N crystal size was observed when the Co loading exceeded 3 wt%, which in turn decreased the catalyst activity for ammonia decomposition reaction. All catalysts exhibit higher activity than the reported nitride catalysts at low temperatures. All catalysts showed stable activity for 30 hours. The activation energy calculated for ammonia decomposition was decreased drastically from 131.2 to 99 kJ mol−1 by the addition of cobalt (1 wt%) in Mo2N preparation.

Fractional sub-equation method for the fractional generalized reaction Duffing model and nonlinear fractional Sharma-Tasso-Olver equation

In this paper the fractional sub-equation method is used to construct exact solutions of the fractional generalized reaction Duffing model and nonlinear fractional Sharma-Tasso-Olver equation.The fractional derivative is described in the Jumarie’s modified Riemann-Liouville sense. Two illustrative examples are given, showing the accuracy and convenience of the method.

Partial oxidation of methanol over Au/CeO2–ZrO2 and Au/CeO2–ZrO2–TiO2 catalysts

Experimental data on hydrogen production via a partial oxidation of methanol (POM) reaction on Au/ZrO2, Au/CeO2–ZrO2 and Au/CeO2–ZrO2–TiO2 catalysts is presented in this article. The gold catalysts were prepared by a deposition–precipitation (DP) method and characterized by XRF, XRD, H2-TPR, XPS methods N2 adsorption. The activity results show that the catalyst containing 1 wt% gold supported on a CeO2–ZrO2 carrier demonstrates very good hydrogen selectivity and the highest catalytic activity among all tested catalysts. The optimal working temperature established was 375 °C. At this temperature 75.5% hydrogen selectivity was registered. The presence of oxidized gold in the catalysts composition as well as the support redox properties are the major factors controlling the observed catalytic activity.

Concept design of a PGNAA system for optimizing the performance of gravity separators

A detection system for the determination of the level of different layers inside the oil gravity separators is presented. The system is based on prompt gamma neutron activation analysis using D-T neutron source. The performance of the system proved to be superior to current and potential nuclear counting techniques proposed in the literature for the same purpose including neutron backscattering, gamma backscattering, and gamma transmission. According to the concept design calculations using the Monte Carlo method, the proposed system detects the levels of different layers with high accuracy. This concept design is the first stage of the research project entitled “design of an instrument for measurement of oil, water, vapour and sand layers in oil separators using neutrons” supported by King Abdulaziz University.

A Modified Generalized Laguerre-Gauss Collocation Method for Fractional Neutral Functional-Differential Equations on the Half-Line

The modified generalized Laguerre-Gauss collocation (MGLC) method is applied to obtain an approximate solution of fractional neutral functional-differential equations with proportional delays on the half-line. The proposed technique is based on modified generalized Laguerre polynomials and Gauss quadrature integration of such polynomials. The main advantage of the present method is to reduce the solution of fractional neutral functional-differential equations into a system of algebraic equations. Reasonable numerical results are achieved by choosing few modified generalized Laguerre-Gauss collocation points. Numerical results demonstrate the accuracy, efficiency, and versatility of the proposed method on the half-line.

COBALT SUPPORTED ON CARBON NANOTUBES. AN EFFICIENT CATALYST FOR AMMONIA DECOMPOSITION

Cobalt supported on carbon nanotubes catalyst is much more active in reaction of ammonia decomposition than nickel and iron catalysts. The observed low temperature activity of Co/carbon nanotubes catalysts is promising option for creating of ammonia decomposition catalysts with low working temperatures.

Correction: New Operational Matrices for Solving Fractional Differential Equations on the Half-Line

The affiliation for the fifth author is incorrect. Abdulrahim A. Alzahrani is not affiliated with #3, but with: Chemical and Materials Engineering Department, Faculty of Engineering, King Abdulaziz University, Jeddah, Saudi Arabia.

Quantitative safety analysis of a laboratory-scale bioreactor for hydrogen sulfide biotreatment using fault tree analysis

Numerous research activities are conducted all over the world to study biological treatment of H2S in laboratory‐scale bioreactors. Important hazards associated with these bioreactor systems include the escape of H2S gas and leakage of chemical/biological liquids, which have severe adverse effects on the involved labors, equipment, and materials. The objective of this article is to present a quantitative safety analysis of a laboratory‐scale continuous bioreactor system for H2S gas biotreatment using the fault tree analysis approach. Three unwanted top events were determined as the most hazardous events, being H2S leakage inside the laboratory, H2S leakage to outdoor from bioreactor outlet, and leakage of liquid chemical/biological solutions. The minimal cut sets and the probability of the occurrence of each top event were determined. The importance of cut sets and basic events were calculated, and priorities for control measures were determined. The analysis allows better decision on priority of control measures, and maintenance or replacement schemes of the system components in an endeavor to minimize the probability of failure or hazard occurrence. The presented analysis proves the usefulness of fault tree analysis in making quantitative risk assessment and safety analysis, which are important elements in laboratory safety management system.

Ammonia treated Mo/AC catalysts for CO hydrogenation with improved oxygenates selectivity

A series of ammonia treated Mo/Activated Carbon (AC) catalysts were synthesized by wet impregnation method by nominal incorporation of 5, 10 and 15 wt% of molybdenum. The calcined catalysts (