Ahmed E. Abasaeed

A method of predicting effective solvent extraction parameters for recycling of used lubricating oils

Solvent extraction technique is one of the cheapest and most efficient processes experienced in recycling of used lubricating oils. In this paper, the performance of three extracting solvents (2-propanol, 1-butanol, and methyl-ethyl-ketone (MEK) in recycling used oil was evaluated experimentally. The effect of the most critical parameters (type of solvent, solvent to oil ratio, and extraction temperature) was investigated. The results show that MEK achieved the best performance with the lowest percent oil losses, followed by 2-propanol and 1-butanol, and as the extraction temperature increases the percent oil losses decreases. The anti-solvency energy (Es), which originates from the solubility parameters difference between the solvent and oil was related to the solvent to oil ratio. It was found that the critical clarifying ratio predicted from such relations for the three solvents reasonably agrees with that measured experimentally. Relations between Es and solvent to oil ratio give a proper guideline for preliminary evaluation of the extracting solvent. It also can be used to predict the optimum solvent:oil ratio and extraction temperature based on the solvent ability to dissolve the base oil in used motor oil.

Effects of Selected Promoters on Ni/Y-Al2O3 Catalyst Performance in Methane Dry Reforming

The Ni catalysts supported on γ-Al2O3 were synthesized by an impregnation method. Their catalytic performance in methane dry reforming was investigated. The reforming reactions were carried out in a microreactor using a CO2:CH4 feed ratio of 1:1, a F/W = 2640 ml/(h·g), reaction temperatures between 500-850 (C, and at atmospheric pressure. The influence of Ca, Ce, and Zr promoters on catalyst stability, coke deposition, and the H2/CO ratio were also studied. Effluents were analyzed using an online gas chromatograph equipped with a thermal conductivity detector. The spent and fresh catalysts were characterized by scanning electron microscopy and thermogravimetric analysis. It was found that 3%Ni/γ-Al2O3 promoted with 0.15% Ce and 0.05% Ca gave the best performance and resulted in less coke formation. The highest CH4 and CO2 conversion activities were found to be 94.1% and 98.3% at 850 (C, respectively. Stability tests were carried out for 130 h and this provided a H2 yield of 91%. Moreover, the amount of formed carbon was negligible and did not increase to more than 1.5 wt%.

Role of La2O3 as Promoter and Support in Ni/γ-Al2O3 Catalysts for Dry Reforming of Methane

Abstract The nature of support and type of active metal affect catalytic performance. In this work, the effect of using La2O3 as promoter and support for Ni/γ-Al2O3 catalysts in dry reforming of methane was investigated. The reforming reactions were carried out at atmospheric pressure in the temperature range of 500–700 °C. The activity and stability of the catalyst, carbon formation, and syngas (H2/CO) ratio were determined. Various techniques were applied for characterization of both fresh and used catalysts. Addition of La2O3 to the catalyst matrix improved the dispersion of Ni and adsorption of CO2, thus its activity and stability enhanced.

Oxidative dehydrogenation of isobutane over pyrophosphates catalytic systems

The catalytic effect of metal pyrophosphates (i.e., Mn2P2O7, Ni2P2O7, CeP2O7, Mg2P2O7, ZrP2O7, Ba2P2O7, V4(P2O7)3 and Cr4(P2O7)3) on the oxidative dehydrogenation of isobutane to isobutene in the reaction temperature range of 400–600 °C has been investigated. CeP2O7 gives the highest isobutene yield and selectivity (71%), however, V4(P2O7)3 is the most active catalyst with an isobutane conversion of 33.5% at 500 °C. Increasing the reaction temperature results in higher isobutane conversions and lower isobutene selectivity. Reaction by-products are propylene, CO, CO2 and traces of methane and ethylene. No oxygenate products are formed under the used reaction conditions. The sum of selectivities of CO, CO2 and methane is approximately equal to that of propylene, indicating their formation from total oxidation of C1 species accompanying the isobutane crack reactions. Working at temperatures higher than 550 °C, the homogeneous gas phase reactions become significant and the oxygen conversion reaches 100%.

Alumina-supported chromium-based mixed-oxide catalysts in oxidative dehydrogenation of isobutane to isobutene

The effect of various metal additives on the catalytic performance of a chromium-based alumina-supported catalyst in oxidative dehydrogenation of isobutane was investigated in the low reaction temperature range 200 � /350 8C and at atmospheric pressure. Various parameters such as Cr wt.% in Cr � /M � /O system, different i C4H10:O2 ratios at a total flow rate of 75 cm 3 /min, and contact time on the activity and selectivity of the catalysts were varied in this study. For the binary catalysts, the addition of Co and Ni enhanced the overall activity while W and Mo improved the catalyst selectivity to i C4H8. The presence of V and Li deteriorated significantly the catalyst activity and selectivity. Increasing the percent of Cr in Cr � /M � /O increased i C4H10 and O2 conversion at the expense of selectivity. Tertiary systems such as Cr � /W � /Co � /O, Cr � /W � /Ni � /O and Cr � /Ni � /Co � / Og ave a much better overall performance compared with Cr � /O alone. In particular, Cr � /W � /Co � /O improved the overall activity of Cr � /O catalyst by 17% while its i C4H8 selectivity improved by 15%. The low temperature activity of these catalysts makes them important candidates for further investigations. # 2002 Elsevier Science B.V. All rights reserved.

Stabilities of zeolite-supported Ni catalysts for dry reforming of methane

Ni/γ-Al2O3, Ni/Y-zeolite, and Ni/H-ZSM-5 catalysts were prepared using the incipient wetness impregnation method. Their catalytic performance in dry reforming of methane was studied. The fresh and used catalysts and deposited carbon were characterized using H2 temperature-programmed reduction, temperature-programmed oxidation, N2 adsorption-desorption, X-ray diffraction, and thermogravimetric analysis. The H-ZSM-5-supported Ni catalyst proved to be more stable than the other two catalysts, as it had the lowest carbon deposition.

Effects of Reducibility on Propane Oxidative Dehydrogenation over γ-Al2O3-Supported Chromium Oxide-Based Catalysts

Alumina-supported chromium oxide and binary mixed oxide catalysts of the form Cr–M oxide/γ-Al2O3 (where M is Ni, Co, Mo, W, Ho, La, Li, Cs or Bi) were found to catalyze the oxidative dehydrogenation of propane at 300-450 °C. The basic characters of the metals were found to determine partly the selectivity to propylene. Cr–Mo/γ-Al2O3 proved to be the most promising. It exhibited a propylene yield of 10.3% at 450 °C. The connections between the selectivity and reducibility of the catalyst were explored. TPR results showed that addition of molybdenum to chromium increased the temperature of reduction maxima. Thus the selectivity to propylene was improved by a decrease in the tendency of the catalyst to undergo a redox cycle. Further, an X-ray photoelectron spectroscopy study conducted on a sample of the catalysts showed that the basicity of the catalysts increased with increase in molybdenum. Catalysts with appropriate Cr/Mo ratios exhibited lower selectivity to over-oxidation product than those containing either chromium or molybdenum alone.

Propane Oxidative Dehydrogenation over Metal Pyrophosphates Catalysts

Metal pyrophosphates (M–P2O7, where M is V, Zr, Cr, Mg, Mn, Ni or Ce) have been found to catalyze the oxidative dehydrogenation of propane to propene. The reaction was conducted at 1 atm, 450–550°C and feed flowrate of 75 cm3/min (20 cm3/min propane, 5 cm3/min oxygen and the balance is helium). All catalysts showed increase in degrees of conversion and decrease in olefins selectivity with increase in reaction temperature. At 550°C, MnP2O7 exhibited the highest activity (40.7% conversion) and total olefins (C3H6 and C2H4) yield (29.3%). The other catalysts, indicated by their respective metals, may be ranked (based on olefins yield) as V (16.9%) < Cr (17.5%) < Ce (25.1%) < Zr (26.2%) < Ni (26.8%) < Mg (27.9%). The reactivity of the lattice oxygen was estimated from energy of formation of the corresponding metal oxides. Correlation between the selectivity to propene and the standard energy of formation was attempted. Although there was no clear correlation, the result suggested that the lattice oxygen play a key role in the selectivity-determining step.

Selectivity of layered double hydroxides and their derivative mixed metal oxides as sorbents of hydrogen sulfide.

In the context of finding high efficient sorbent materials for removing hydrogen sulfide (H2S) from air stream, a screening study was performed to find the best combination of metals for the synthesis of layered double hydroxides (LDHs) and their derivative mixed metal oxides. Based on selectivity of 998 natural mineral species of sulfur-containing compounds, Cu(2+), Ni(2+) and Zn(2+) were selected as divalent metals, and Fe(3+), Al(3+) and Cr(3+) as trivalent metals to synthesis the LDHs sorbents. 10 LDHs materials and their calcined mixed metal oxides, Ni(0.66)Al(0.34), Cu(0.35)Ni(0.32)Al(0.33), Zn(0.66)Al(0.34), Cu(0.36)Zn(0.32)Al(0.32), Ni(0.64)Fe(0.36), Cu(0.35)Ni(0.31)Fe(0.34), Ni(0.66)Cr(0.34), Cu(0.35)Ni(0.31)Cr(0.34), Zn(0.66)Cr(0.34), Cu(0.33)Zn(0.32)Cr(0.35) were synthesized, characterized chemically and physically, and then tested using breakthrough test to determine their sulfur uptake. Ni(0.64)Fe(0.36) mixed metal oxides was found to have the best uptake of hydrogen sulfide (136 mg H₂S/g). Regeneration of spent Ni(0.64)Fe(0.36) mixed metal oxides was studied using two different mixture solutions, NaCl/NaOH and acetate-buffer/NaCl/NaOH. The latter mixture successfully desorbed the sulfur from the Ni0.64Fe0.36 sorbent for 2 cycles of regeneration/sorption.

Activities of γ-Al2O3-Supported Metal Oxide Catalysts in Propane Oxidative Dehydrogenation

The activities of metal oxide catalysts in propane oxidative dehydrogenation to propene have been studied. The catalysts are M/γ-Al2O3 (where M is an oxide of Cr, Mn, Zr, Ni, Ba, Y, Dy, Tb, Yb, Ce, Tm, Ho or Pr). Both transition metal oxides (TMO) and rare-earth metal oxides (REO) are found to catalyze the reaction at 350-450 °C, 1 atm and a feed rate of 75 cm3/min of a mixture of C3H8, O2 and He in a molar ratio of 4:1:10. Among the catalysts, Cr-Al-O is found to exhibit the best performance. The selectivity to propene is 41.1% at 350 °C while it is 54.1% at 450 °C. Dy-Al-O has the highest C3H6 selectivity among the REO. At 450 °C, the other catalysts show C3H6 selectivity ranging from 16.2 to 37.7%. In general TMO show higher C3H6 selectivity than REO, which, however, show higher C2H4 selectivity. An attempt is made to correlate propane conversion and selectivity to C3H6 with metal-oxygen bond strength in the catalysts. For the TMO a linear correlation is found between the standard aqueous reduction potential of the metal cation of the respective catalyst and its selectivity to propane at 11% conversion. No such correlation has been found in the case of REO. Analyses of the product distributions suggest that for TMO propane activation the redox mechanism seems to prevail while the REO activate it by adsorbed oxygen.