The use of bio-diesel based additive as rheology improver and pour point depressant of Nigerian waxy crude

The chemical method has proved to be the most effective mitigating method of wax deposition in petroleum system as it deals with the root cause of wax formation. Most of the commercial chemicals in the industry are very expensive and toxic. This paper aims the use of biodiesel based additives for improving the rheological behavior and pour points of waxy crude from Nigeria field. The biodiesels derived additives gave better performance than the commercial chemical and the seed oils as greatly improvement in rheology and pour point values of the waxy crude were observed     

THE KINETICS OF H2S DECOMPOSITION OVER PRECIPITATED COBALT SULPHIDE CATALYST

Cobalt sulphide catalyst prepared via a new method involving the precipitation reaction between cobaltous acetate and ammonium sulphide solutions has been shown to be favourably active for the catalytic decomposition of H₂S when compared with data for other transition metal sulphides.

The BET surface area of this unsupported catalyst is about an order of magnitude higher than cobalt sulphide formed by direct sulphidation of cobalt oxide with H₂S gas. XRD, SEM and TEM analyses were used to obtain bulk composition and morphological characteristics. Catalyst specimen calcined at 823 K showed the best activity.

The kinetics of the decomposition reaction has been studied over this new preparation. Experiments conducted at atmospheric pressure between 933-983 K using about 11 feed compositions showed that below 40% H₂S/Ar the reaction was essentially 1st order with respect to H₂S partial pressure. Beyond this point, rate remained invariant with feed composition. A mechanism involving catalysis via co-ordinative unsaturation sites on the CoS was proposed and kinetic model based on the cleavage of the surface H-S bond as the rate-determining step appeared to be the most adequate representation of the rate data. Hydrogen production rates at all temperatures also paralleled the behaviour seen for H₂S decomposition. Activation energy for H₂S decomposition and H₂ production rates were estimated as 111 kJ mol^-1 and 88 kJ mol^-1 respectively     

Supported Rh catalysts for the indirect partial oxidation of isooctane

The production of hydrogen from isooctane over three rhodium-based catalysts has been examined. The reaction entailed total oxidation of a proportion of the fuel followed by reforming of isooctane to produce hydrogen. Rhodium (1% wt) was impregnated on three different supports: alumina, ceria-alumina, and ceria-zirconia. No differences in catalytic activity were observed, but reaction yield changed with the support. Ceria-zirconia was found to be the preferred support since methanation did not occur over the catalyst.     

Modeling and simulation of non-isothermal catalytic packed bed membrane reactor for H2S decomposition

The recovery of H₂ from H₂S is an economical alternative to the Claus process in petroleum and minerals processing industries. Previous studies [React. Kinet. Catal. Lett. 62 (1997) 55; Catal. Lett. 37 (1996) 167] have demonstrated that catalytic decomposition of H₂S over bimetallic sulfide can proceed at relatively higher rates than over mono-metallic systems due to chemical synergism although conversions are still thermodynamically limited. In the present study, the performance of a catalytic membrane reactor containing a packed bed of Ru–Mo sulfide catalyst has been investigated with a view to improving H₂ yield beyond the equilibrium ceiling. A system of differential equations describing the non-isothermal reactor model has been solved to examine the effect of important hydrodynamic and transport properties on conversion. The results were obtained using a Pt-coated Nb membrane tube as the catalytic reactor enclosed in a quartz shell cylinder. Reynolds number for shell and tube side (Re^s and Re^t) as well as the modified wall Peclet number, Pe_m, dramatically affect H₂S conversions. Membrane reactor conversion rose monotonically with axial distance exceeding the equilibrium conversion by as much as eight times under some conditions.     

Optimization of the fabrication of novel stealth PLA-based nanoparticles by dispersion polymerization using D-optimal mixture design

Purpose: Nanoparticle size is important in drug delivery. Clearance of nanoparticles by cells of the reticuloendothelial system has been reported to increase with increase in particle size. Further, nanoparticles should be small enough to avoid lung or spleen filtering effects. Endocytosis and accumulation in tumor tissue by the enhanced permeability and retention effect are also processes that are influenced by particle size. We present the results of studies designed to optimize cross-linked biodegradable stealth polymeric nanoparticles fabricated by dispersion polymerization.

Methods: Nanoparticles were fabricated using different amounts of macromonomer, initiators, crosslinking agent and stabilizer in a dioxane/DMSO/water solvent system. Confirmation of nanoparticle formation was by scanning electron microscopy (SEM). Particle size was measured by dynamic light scattering (DLS). D-optimal mixture statistical experimental design was used for the experimental runs, followed by model generation (Scheffe polynomial) and optimization with the aid of a computer software. Model verification was done by comparing particle size data of some suggested solutions to the predicted particle sizes.

Results and conclusion: Data showed that average particle sizes follow the same trend as predicted by the model. Negative terms in the model corresponding to the cross-linking agent and stabilizer indicate the important factors for minimizing particle size.     

Differential role for protein kinase C-mediated signaling in the proliferation of medulloblastoma cell lines

7-beta-D-Ribofuranosylxanthine, a previously unreported isomer of xanthosine, was prepared in four steps from 7-benzylxanthine. The procedure, which involves the use of pivaloyloxymethyl groups to protect the xanthine ring, was also applied to preparation of some 1-N-alkyl derivatives of 7-ribosylxanthine. Adenosine receptor affinity for these compounds was determined. 7-beta-D-Ribofuranosylxanthine was found to have higher affinity and greater selectivity for the A1 receptor than previously reported xanthine nucleosides, and to be a partial agonist.     

Coke removal from deactivated Co–Ni steam reforming catalyst using different gasifying agents: An analysis of the gas–solid reaction kinetics

The reactivity of various gases, namely; O₂, air, CO₂, H₂ and N₂, with carbon deposited on alumina-supported Co–Ni catalyst during propane reforming in a fluidized bed reactor at 773–973 K using relatively low feed steam:carbon ratio (0.8–1.5) has been investigated in a thermogravimetric analysis unit. Analysis of the transient solid weight loss revealed that carbon removal mechanism is dependent on the type of gasifying agent. Carbon gasification kinetics using O₂ and air followed the Avrami-Erofeev (A2) model while data for both CO₂ and H₂ were captured by the geometrical (contracting area, R2) model. However, carbon gasification with inert N₂ proceeded at much slower rate (about 10 times lower than air) and was adequately fitted by the one-dimensional diffusion (D1) model. Specific reaction rates from these phenomenological models were also linearly correlated with the catalyst carbon content with reactivity coefficient of the gasifying agent decreasing in the order, O₂ > air > CO₂ > H₂ > N₂. In order to minimize energy consumption during catalyst regeneration, reduce greenhouse gas emissions and reduce catalyst sintering, it would be desirable to employ a mixture of air and CO₂ as the carbon gasifying agent to take advantage of the coupled exothermic (air oxidation) and endothermic (reverse Boudouard reaction involving CO₂ and carbon) nature taking place during the carbon removal operation.     

Correction to: Durability Properties of Alkali Activated Slag Composites: Short Overview

Silicon - The original version of this paper was unfortunately published as a book review, when it is a review article.     

Uniform Virus‐Like Co–N–Cs Electrocatalyst Derived from Prussian Blue Analog for Stretchable Fiber‐Shaped Zn–Air Batteries

Zn‐air batteries (ZABs) offer promising commercialization perspectives for stretchable and wearable electronic devices as they are environment‐friendly and have high theoretical energy density. However, current devices suffer from limited energy efficiency and durability because of the sluggish oxygen reduction and evolution reactions kinetics in the air cathode as well as degenerative stretchability of solid‐state electrolytes under highly alkaline conditions. Herein, excellent bifunctional catalytic activity and cycling stability is achieved by using a newly developed Co–N–C nanomaterial with a uniform virus‐like structure, prepared via a facile carbonization of a prussian blue analogue (PBA). Furthermore, a solid‐state dual‐network sodium polyacrylate and cellulose (PANa‐cellulose) based hydrogel electrolyte is synthesized with good alkaline‐tolerant stretchability. A solid‐state fiber‐shaped ZAB fabricated using this hydrogel electrolyte, the virus‐like Co–N–Cs air cathode, and a zinc spring anode display excellent stretchability of up to 500% strain without damage, and outstanding electrochemical performance with 128 mW cm^?2 peak power density and good cycling stability for >600 cycles at 2 mA. The facile synthesis strategy demonstrated here opens up a new avenue for developing highly active PBA‐derived catalyst and shows, for the first time, that virus‐like structure can be favorable for electrochemical performance.