Mohammed Ashraf Ali

Photodegradation of Rhodamine B over unexcited semiconductor compounds of BiOCl and BiOBr

This study reported, for the first time systematically, photodegradation of Rhodamine B (RhB) in aqueous solution over BiOCl and BiOBr semiconductors. Under visible light irradiation (λ>400 nm, λ>420 nm and λ=550±15 nm), RhB adsorbed on the surface of BiOCl and BiOBr was photosensitized and decomposed effectively over unexcited BiOCl and BiOBr. The degradation of Methyl Orange (MO) and Methylene Blue (MB) over BiOCl and BiOBr was investigated as well, and the results were compared with RhB photodegradation. It was found that MB molecules having the lowest LUMO could not be degraded by this process. Utilizing the quantum chemical calculation (Gaussian 03 program), the relationship between frontier orbital energy of selected dye molecules and photodegradation rate was established for the first time in this study.

Comparative Study of Solvents for the Extraction of Aromatics from Naphtha

An experimental investigation was carried out to evaluate the efficiencies of different selective solvents used for the extraction of aromatic hydrocarbons from naphtha (boiling range IBP-200°C) distilled from Saudi Arabian light crude oil. The solvents used were 3-methoxypropionitrile, ethylene glycol, dimethylsulfoxide, sulfolane, phenol, and nitrobenzene. The parameters studied were operating temperature (range 20°-125°C), solvent-to-oil ratio (range 1:1-3:1), selectivity, and solvent capacity. The results indicate that sulfolane exhibits excellent extraction properties in comparison with other solvents. In addition, sulfolane has the advantage of having good solvent properties such as high density, low heat capacity, and appropriate boiling point, which helps simplify separation of the solvent from extract. Sulfolane is also commercially feasible as a solvent for aromatic extraction.

Determination of hydrocarbon types in naphthas, gasolines and kerosenes: a review and comparative study of different analytical procedures

Abstract Standardized and non-standardized methods were used to study hydrocarbon types, namely paraffins, olefins, naphthenes and aromatics (PONA) in petroleum fractions. They were determined using the ASTM method of fluorescent indicator adsorption (FIA) and gas chromatographic techniques including capillary and valve switching multiple packed columns. Refinery products with final boiling points up to 270 °C were analysed, and results were reported according to carbon number. The advantages and disadvantages of the methods investigated are presented in this paper. Generally, results of multicolumn gas chromatography (MC-g.c.) were closer to FIA compared with capillary column gas chromatography (CC-g.c.). Furthermore, MC-g.c. gives better results and requires less interpretation time than CC-g.c., While changing calibration tables for radically different samples in CC-g.c. is a time consuming and tedious job, the other two methods do not require such an elaborate step. However, CC-g.c. is suitable for laboratories dealing with basically similar types of samples, or samples having a small number of components.

Impact of gasoline and diesel specifications on the refining industry

Future gasoline specifications demand reduction in aromatics, benzene, sulfur, volatility, and boiling point. In response, refiners must modify their processing conditions, catalysts, and mode of operation of catalytic reformers and isomerization units. Diesel fuel is also facing tighter specifications for cetane number, aromatic content, sulfur, and color. To meet these specifications, operational modifications include use of higher activity catalysts, higher hydrotreating seventy, and two-stage processing. This paper reviews fuel legislation adopted recently worldwide, and refining technology solutions practiced and / or planned to meet the new specifications.

APPLICATION OF HIGH PERFORMANCE LIQUID CHROMATOGRAPHY FOR HYDROCARBON GROUP TYPE ANALYSIS OF CRUDE OILS

ABSTRACT High performance liquid chromatography (HPLC) was applied to four commercial grade Saudi Arabian crude oils having API gravity in the range 28 to 38 for the determination of hydrocarbon group types namely asphaltenes, saturates, aromatics and polars. Each of these crude oils was separated into asphaltenes and maltenes using n-hexane as the precipitating solvent. The maltenes (n-hexane soluble) were fractionated into saturates, aromatics and polars fractions by n-hexane elution on a column packed with amino propylsilane chemically bonded to porous silica particles. The data obtained shows that the weight percent saturates increase whereas aromatics, polars and asphaltenes decrease from Arab Heavy to Arab Bern through Arab Medium and Arab Light crude oil. The results obtained from HPLC were in comparison with those obtained from ASTM method D2007. This method is easier, faster and offer good repeatability. This method can be applied to other crude oils.

Ni-Mo-Titania-Alumina Catalysts with USY Zeolite for Low Pressure Hydrodesulfurization and Hydrocracking

Abstract Titania-alumina based catalysts were prepared and tested for hydrodesulfurization (HDS) and hydrocracking activity in the temperature range 300°C to 350°C in a fixed-bed reaction system using 4,6-dimethyldibenzothiophene (4,6-DMDBT) dissolved in n-hexadecane. Characterization results show that the metal-loaded titania-alumina possesses a high pore radius and pore volume but low surface area. The physical mixing with USY zeolite increased its surface area. The surface area was further increased upon mixing with nanoporous alumina. The total ammonia based acidity of the titania-alumina was lower than that of the ultra stable Y (USY) zeolite, but Ni-Mo loading was found to increase the acidity. The acidity of titania-alumina was further increased by mixing with nanoporous alumina and USY zeolite. All catalysts exhibited good HDS and hydrocracking activity for 4,6-DMDBT and n-hexadecane. The catalyst showing the highest HDS activity using 4,6-DMDBT was further tested and was found to have reasonable activity for both low- and high-sulfur vacuum gas oil feeds. This study demonstrated low-pressure HDS activity of the catalysts.

Prediction of reformate research octane number by FT-i.r. spectroscopy

Abstract Fourier transform infrared (FT-i.r.) spectroscopy was used to calculate the research octane number (RON) of naphtha feed and reformate during the course of performance evaluation of reforming catalysts. Five absorption regions that correspond to aliphatic and aromatic bands within the mid-infrared region were utilized for developing the correlation for RON estimation. Statistical methods were used to derive third degree polynomial equations which could give a better estimate of engine RON. The technique was found to give excellent correlation (R2 = 0.95) with the engine RON data.

Investigation of nitrogen compound types in high-boiling petroleum distillates from Saudi Arabian crude oils

ABSTRACT Acids, bases and neutral nitrogen compounds from high-boiling petroleum distillates were separated and further fractionated into fractions containing nitrogen compound types by HPLC on neutral alumina. Acids and bases were separated with anion and cation exchange resins respectively while the neutral nitrogen compounds were removed by complexation with ferric chloride supported on Attapulgus clay. The HPLC fractions were characterized by potentiometric titration for their basic and nonbasic nitrogen contents while infrared spectroscopy was used for the quantitative determination of major compound types present which are pyridines, pyrroles, amides, phenols and carboxylic acids. Characterization of individual nitrogen compounds was accomplished using gas chromatography and gas chromatography -mass spectrometry. The nitrogen compounds identified belong to three compound types which are pyridine, pyrrole and amide.

Hydrocarbon group (PONA) analysis of reformate by FT-i.r. spectroscopy

Multicolumn valve-switching gas chromatography is commonly used in refineries for determining paraffins, olefins, naphthenes and aromatics (PONA) contents of reformate and naphtha samples. A simplified and fast alternative method, Fourier transform infrared (FT-i.r.) spectroscopy, for the same purpose was successfully used in the present work. In this method, a calibration technique which took both spectral and concentration data into consideration was developed by using the instrument manufacturers software utilizing partial least-squares (PLS) regression analysis. For this, the mid-i.r. range (4000-400 cm−1) was subdivided into four regions that are usually attributed to different functional groups. An excellent correlation between the FT-i.r. and g.c. results was found, particularly for paraffins and aromatics (R2 = 0.97 and 0.96 respectively). The average absolute differences between the results obtained from FT-i.r. and g.c. were 1.3, 0.5, 0.2 and 0.9 vol.% for paraffins, olefins, naphthenes and aromatics respectively.

Photo-conversion of methane into higher hydrocarbons using 355 nm laser radiation

A laser‐based technique for the conversion of methane into higher hydrocarbons and hydrogen has been developed. This technique involves the photo‐dissociation of methane using a high power pulsed ultraviolet laser at 355 nm. The reaction products, such as CH, CH2, C2H2, atomic and molecular hydrogen, are characterized by real‐time laser induced fluorescence for the first time, to our knowledge. In addition to this online fluorescence detection of the species, gas chromatography is also applied to analyze the stable hydrocarbon products generated due to photo‐dissociation of methane. Another interesting result of the laser excitation of methane is the observation of Stimulated Raman lines (Stokes and Antistokes) observed in the 150–850 nm region, which is a manifestation of the inherent characteristics of the laser radiation such as high directionality and high intensity.