Mohammed A.B. Siddiqui

Dearomatization, cetane improvement and deep desulfurization of diesel feedstock in a single-stage reactor

Hydrotreating of light cycle oil over CoMo/Al2O3, NiMo/Al2O3 and NiW/Al2O3 catalysts has shown that the type of catalyst has a critical influence on the composition and properties of the product. Divergent effects of aromatics content and molecular weight on the cetane index by these catalysts occurred. Data show that it was not possible to obtain a diesel product that meets stringent specifications using one type of catalyst in a single-stage reactor even under severe operating conditions.

Investigation of the rapid crystallization method for the synthesis of MFI-type zeolites and study of the physicochemical properties of the products

MFI-type zeolites were synthesized by the rapid crystallization method in 2 h. The synthesis parameters were studied briefly using a statistical method, and the pH of the initial hydrogel was found to be the most critical parameter under the synthesis conditions used and the crystallization time constrain. The physicochemical properties of the zeolite products were studied and found to have some advantages over conventionally synthesized zeolites. The thermal stability was found to decrease with increasing Si/Al ratio contrary to what was widely accepted. It was speculated that high concentrations of defect sites exaggerated by the rapid crystallization time may be responsible for the trend of thermal stability.

UCloud: A simulated Hybrid Cloud for a university environment

Universities all around the world play a vital role in improving the society. But in the current economic crisis, they are facing difficulties in providing necessary resources for research and educational purposes. The solution of this problem is in the use of Cloud Computing. It is a new distributive computing model which provides applications and services over the Internet. In this paper, we investigate, study, and simulate a cloud for a university environment. We propose an architecture based on the hybrid cloud model which uses both the public and private clouds. It consists of two main parts, i.e., the Cloud Management System and the Hybrid Cloud. The proposed architecture is simulated using CloudSim. The evaluation of this architecture is performed for two separate scenarios. In the first one, the number of tasks is kept constant; and in the second, the number of tasks is changed. The results obtained are encouraging and support the use of a hybrid cloud solution for a university. The public cloud is used only to get a better performance or when the load is too high for the private cloud. The results show that high performance can be obtained while keeping the cost low.

Kinetics of methyl tertiary butyl ether synthesis catalyzed by sulphuric acid

Abstract The results of an experimental investigation into the kinetics of the liquid-phase reaction between methanol and isobutene, catalyzed by sulphuric acid These kinetic data were fitted to a powerlaw kinetic model, using a,non-linear least-squares regression technique. The reaction was found to follow fir

Production of methyl tert-butyl ether (MTBE) over MFI-type zeolites synthesized by the rapid crystallization method and modified by varying Si/Ai ratio and steaming

Abstract The reaction of isobutene and methanol to produce methyl tert-butyl ether (MTBE) has been studied over MFI-type zeolites (ZSM-5) with varying Si/Al ratios. All the zeolites were synthesized by the rapid crystallization method. The number of Bronsted acid sites on the zeolite surface have been shown to increase proportionally with the aluminum contents of the zeolites. Under kinetically limited reaction conditions, the activity of the catalysts increased with number of acid sites. However near reaction equilibrium, the rate of increase of catalyst activity slowed down. The maximum activity was achieved at 80°C which was an optimum temperature condidering the catalyst activity and equilibrium conversion. Mild steaming caused a modest increase in isobutene conversion which was close to equilibrium conditions. On the other hand, severe steaming resulted in a decrease in activity. The effect of steaming was best attributed to new adsorption sites and/or enhanced Bronsted acidity. The zeolite gave a stable performance in an extended test up to at least 30 h on stream. All the catalysts tested displayed 100% selectivity for the production of MTBE at all the reaction conditions studied.

Performance evaluation of HDS catalysts by distribution of sulfur compounds in naphtha

Abstract This paper presents results of pilot plant evaluation of two commercial hydrodesulfurization (HDS) catalysts and demonstrates the use of trace sulfur analysis and distribution of sulfur compounds for reliable and better catalyst evaluation. Straight-run naphtha (SRN) and a blend of SRN and hydrocracked naphtha containing 897 and 534 ppm sulfur respectively were analysed for sulfur compound distribution by gas chromatography with flame photometric detection and hydrocarbon type composition by a PONA analyser. G.c.-f.p.d. analysis indicated the presence of 52 sulfur compounds, including mercaptans (55.7%), thiophenes and sulfides (43.1%), disulfides (1.1%) and traces of polysulfides, hydrogen sulfide and elemental sulfur. Pilot plant experiments were carried out with two catalysts at 220–350°C, space velocities of 10 and 13 h−1 and gas rates of 67 and 8011−1. Total and mercaptan sulfur in the product passed through a minimum with increasing temperature. The optimum temperature was 320°C for SRN and 300°C for the blend naphtha. Thiophenes, forming a major portion of the sulfur in the product, could be removed by hydrotreating at >280°C. At higher temperatures, methyl mercaptan increased, owing to hydrogen sulfide recombination reactions. One of the catalysts performed better than the other.

Development of a multi-resolution framework for NUBS

The piecewise polynomial B-spline representation is a flexible tool in Computer Aided Geometric Design (CAGD) for representing and designing the geometric objects. In the field of Computer Graphics (CG), Computer Aided Design (CAD), or Computer Aided Engineering (CAE), a very useful property for a given spline model is to have locally supported basis functions. This allows localized modification of the shape. Unfortunately this property can also become a serious disadvantage when the user wishes to edit the global shape of a complex object. A multi-resolution representation is proposed as a solution to alleviate this problem.In this work, we propose a multi-resolution representation for Non-uniform B-splines (NUBS). The proposed multi-resolution model has three features that it uses control point decimation strategy for decomposing NUBS curves and it is efficient in both time and space utilization. A comparative study of the proposed work is also made with an alternate approach in the literature, which is based upon knot decimation.

Evaluation of naphtha reforming catalysts by accelerated deactivation tests

Accelerated deactivation tests of four commercial Pt−Re/Al2O3 catalysts have been carried out in a pilot plant at RON values of 98–100. From this 350-hour test, specific performance data for objective comparison of catalysts were obtained.