Ahmed A. Abdeltawab

A review of extractive desulfurization of fuel oils using ionic liquids

Hydrodesulfurization (HDS), a widely employed method in industries for the desulfurization of fuel oils, such as gasoline and diesel fuel is faced with the challenge of producing lower-sulfur or sulfur-free fuel oils, which are required by more and more countries. However, HDS is not very effective for the removal of thiophenic sulfur compounds due to sterically-hindered adsorption on the catalyst surface, unless operated under harsh conditions, such as high temperature, high pressure, and requirement of a noble catalyst and hydrogen. Extractive desulfurization (EDS) of fuel oils using ionic liquids (ILs) has been intensively studied in recent decades and has a good future as an alternative or complementary method to HDS. In this review, we reviewed the research results of EDS using ILs and provided comprehensive discussions on diverse factors, which influence desulfurization, such as the IL species, IL–oil mass ratio, initial sulfur content, temperature, time, mutual solubility, multiple extractions and regeneration. Potential problems or shortcomings were also stated. Some other desulfurization methods currently under study, such as extraction, oxidation, adsorption and biodesulfurization were also briefly outlined. It can be inferred that ILs remain a class of ideal solvents to realize clean fuel oil in the near future because of their desirable physiochemical properties, which are lacking in molecular organic solvents, while there are possible challenges, such as relatively high viscosity and low efficiency.

Computational fluid dynamics study on mixing mode and power consumption in anaerobic mono- and co-digestion

Computational fluid dynamics (CFD) was applied to investigate mixing mode and power consumption in anaerobic mono- and co-digestion. Cattle manure (CM) and corn stover (CS) were used as feedstock and stirred tank reactor (STR) was used as digester. Power numbers obtained by the CFD simulation were compared with those from the experimental correlation. Results showed that the standard k-ε model was more appropriate than other turbulence models. A new index, net power production instead of gas production, was proposed to optimize feedstock ratio for anaerobic co-digestion. Results showed that flow field and power consumption were significantly changed in co-digestion of CM and CS compared with those in mono-digestion of either CM or CS. For different mixing modes, the optimum feedstock ratio for co-digestion changed with net power production. The best option of CM/CS ratio for continuous mixing, intermittent mixing I, and intermittent mixing II were 1:1, 1:1 and 1:3, respectively.

Extractive Desulfurization of Fuel Oils with Dicyano(nitroso)methanide-based Ionic Liquids

The inability of traditional hydrodesulfurization (HDS) to effectively remove aromatic sulfur compounds such as thiophene (TS) and dibenzothiophene (DBT) has called for alternative methods to be studied, among which extractive desulfurization using ionic liquids (ILs) has attracted increasing interest. In this work, we prepared a new IL, 1-butyl-3-methylimidazolium dicyano(nitroso)methanide ([C4mim][dcnm]), and investigated its extractive desulfurization for both model oils and real FCC gasoline, where model diesel fuel was composed of n-hexane and droplets of DBT and model gasoline was composed of n-hexane, toluene and droplets of TS. Other three [dcnm]-based ILs, 1-ethyl-3-methylimidazolium dicyano(nitroso)methanide ([C2min][dcnm]), N-ethyl-N-methylpyrrolidinium dicyano(nitroso)methanide ([C2mpyr][dcnm]), and N-butyl-N-methylpyrrolidinium dicyano(nitroso)methanide ([C4mpyr][dcnm]), were also comparatively investigated. These [dcnm]-based ILs have low viscosity which favors the mass transfer and reduces the extractive equilibrium time, also are fluorine-free which avoids the corrosion by hydrogen fluoride from anion decomposition that occurs generally in fluorine-containing ILs. The desulfurization ability follows the order [C4min][dcnm] > [C4mpyr][dcnm] > [C2min][dcnm] > [C2mpyr][dcnm]. Typically, [C4min][dcnm] is capable of removing 66% DBT and 53% TS from their respective model oils after one cycle (initial 500 ppm S, 25°C, 15 min, mass ratio of IL:oil 1:1), and < 10 ppm S-content can be obtained after 4 cycles. It was observed interestingly that the S-content in real FCC gasoline can be reduced from initial 250 ppm to < 30 ppm after 6 cycles using [C4min][dcnm] as extractive reagent, which is better than some previous results for real feedstocks. Mutual solubility, extractive temperature, IL:oil mass ratio, multiple extraction, initial S-content, and regeneration were also studied. These dcnm-based ILs are competitive extractive reagents compared with some other ILs to remove those aromatic S-compounds from fuel oils.

Oxidative Desulfurization of Gasoline by Ionic Liquids Coupled with Extraction by Organic Solvents

In this work, desulfurization of real fluidized catalytic cracking (FCC) gasoline was investigated in dual steps; first in oxidative desulfurization (ODS) using imidazolium and pyrrolidonium based Bronsted acidic ionic liquids (ILs) as solvent and catalyst and hydrogen peroxide as oxidant. In second step, extractive desulfurization took place using organic solvents of furfural, furfural alcohol and ethylene glycol. Variety of factors such as temperature, time, mass ratio of oil/ILs and regeneration and recycling of ILs, multiple-step desulfurization of ILs and organic solvents and solvent/oil ratio were also investigated. The S-content was significantly decreased to ca. 18 ppm from initial S-content of 260 ppm with a total S-removal of ca. 95% in one-step ODS using pyrrolidonium based ILs coupled with five-step extraction desulfurization (EDS) using furfural alcohol as extractant. This work shows that oxidative desulfurization using ionic liquids coupled with extractive desulfurization using organic solvents is a potential method to produce clean gasoline.

N-methyl-2-pyrrolidonium-based Brönsted-Lewis acidic ionic liquids as catalysts for the hydrolysis of cellulose

We experimentally studied the catalytic performances of a series of Brönsted-Lewis acidic N-methyl-2-pyrrolidonium metal chlorides ([Hnmp]Cl/MClx, where M=Fe, Zn, Al, or Cu) for the hydrolysis of microcrystalline cellulose (MCC) and cotton to produce reducing sugar. A variety of factors, such as temperature, time, ionic liquid (IL) species, IL dosage, and the concentration of the metal chloride were investigated. [Hnmp]Cl/FeCl3 presented the best hydrolysis performance, affording a 98.8% yield of total reducing sugar from MCC (1 h, 100 °C, 0.1 g MCC, 0.2 g acidic IL, 2.0 g [Bmim]Cl as solvent), which is better than or comparable to results previously obtained with other–SO3H functionalized acidic ILs. The hydrolysis performances of [Hnmp]Cl/MClx were rationalized using density functional theory calculations, which indicated that interactions between the metal chlorides and the cellulose, including charge-transfer interactions are important in the hydrolysis of cellulose and degradation of glucose. This work shows that Brönsted-Lewis acidic ILs are potential catalysts for the hydrolysis of cellulose to produce sugar.

Cholinium amino acids-glycerol mixtures: New class of solvents for pretreating wheat straw to facilitate enzymatic hydrolysis

New solvents for pretreating wheat straw, mixtures of cholinium amino acids ionic liquids ([Ch][AA] ILs) and glycerol, were developed. As a typical result, 50% cholinium alanine-glycerol is capable of removing 67.6% lignin while reserving 95.1% cellulose (90°C, L/S mass ratio of 20:1, 6h) and the conversions of cellulose and xylan are 89.7% and 70.9%, respectively, which is comparable to the pretreatment capability of other solvents, while [Ch][AA]-glycerol mixtures have desirable advantages, e.g., biocompatibility, lower cost with adding glycerol than pure IL, much lower pretreatment temperature (typically <100°C) than that by glycerol (typically >200°C). Lignin removal and polysaccharide conversion are dependent on [Ch][AA] content and pH of pretreatment solvents. [Ch][AA] not only remove lignin in wheat straw effectively but also swell cellulose while not remarkably dissolve cellulose with high cellulose reservation, favoring the enzymatic hydrolysis. Such mixtures of ILs and co-solvents are potential solvents for pretreating biomass.

Adsorption of uranium in the presence of different ions, humic acid and effect of thorium on uranium adsorption by activated carbon

AbstractIn this study, rice straw-based carbon was prepared and then modified by two acidic and basic oxidizing agents. One oxidized by HNO3, labeled as RSN, and other oxidized by KOH labeled as RSK. The modified carbons (RSN and RSK) were tested in two single-component systems: Removal of U(VI) using RSK and Th(IV) using RSN. Factors affecting U(VI) in three multi-component systems were examined: (i) Co-existing anions and cations, (ii) co-existing Th(IV), and (iii) presence of humic acid (HA). In this concern, different cations under investigation have marginal effect on the adsorption of uranium, except in case of iron ion. Co-existing of iron ions at high levels may compete strongly for the adsorption sites with uranium ions, resulting in a substantial reduction of uranium removal. The prepared carbon showed good selectivity in extracting uranium even in the presence of relatively high concentrations (100 mg/l) of anionic complexing agents and common electrolyte species. In case of multi-component sys...

Pretreatment of wheat straw using basic ethanolamine-based deep eutectic solvents for improving enzymatic hydrolysis

A series of ethanolamine based deep eutectic solvents (DESs), which have strong basicity, were firstly applied in wheat straw pretreatment. Typically, choline chloride: monoethanolamine (C:M) as the best solvent among these DESs can remove 71.4% lignin and reserve 93.7% cellulose (70 °C, L/S mass ratio of 20:1, 9 h), and improve the enzymatic hydrolysis of residue, i.e., 89.8% cellulose and 62.0% xylan conversion. The pretreatment capacity of C:M is comparable to other solvents while C:M has several advantages, e.g., lower cost with cheap materials and simpler preparation process, mild conditions and lower polysaccharide loss. The XRD, SEM and FT-IR results verified that the polysaccharide conversion and sugars yield were enhanced by the removal of lignin in the pretreatment process. The basic ethanolamine based DESs are promising solvents for industrial application of wheat straw pretreatment.

Elimination of the azeotropic point of acetone and methanol by 1,3-dimethylimidazolium dimethylphosphate: an ab initio calculation study

Abstract1,3-Dimethylimidazolium dimethylphosphate ([C1mim][DMP]) was observed experimentally to be able to eliminate the atmospheric azeotropic point of acetone and methanol, which is an important azeotrope generally encountered in furfural production and the Fischer-Tropsch process. Here, we employed ab initio calculation to understand the underlying mechanism of [C1mim][DMP] in eliminating the azeotropic point of acetone and methanol. Structure, energy and interaction in binary-, ternary- and quaternary-clusters composed of methanol, acetone, [C1mim]+ or/and [DMP]‾ were calculated. The σ-hole, AIM and NBO analyses were performed to understand intermolecular interaction with electron density, electron occupancy, charge transfer and molecular orbital interaction. Hydrogen bond interaction plays a key role in azeotropic point elimination; due to the much stronger hydrogen bond interaction between methanol and [C1mim][DMP] than that between acetone and [C1mim][DMP], [C1mim][DMP] prefers to interact with methanol rather than acetone, and the original interaction between methanol and acetone is separated by [C1mim][DMP]. The hydrogen bond is from the orbital interaction between O lone-pair-electron orbitals of the hydrogen bond acceptor and σ * (C-H) or σ * (O–H) anti-bonding orbitals of the hydrogen bond donor, where remarkable electron or charge transfer occurs. These theoretical calculation results are in agreement with the experimental observation that [C1mim][DMP] eliminates the azeotropic point of methanol and acetone. This work shows that ab initio calculation may be employed to rationalize the design or synthesis of ionic liquids for separating azeotropes. Graphical AbstractElimination of azeotropic point of acetone and methanol by [C1mim][DMP]