LIQUEFACTION AND THE CHARACTERIZATION OF COAL DERIVED LIQUIDS OF MENGEN LIGNITE

ABSTRACT

The liquefaction characteristics of Mengen lignite has been investigated in the presence of cobalt-molybdenum on alumina catalyst in a 1 lt batch autoclave system with anthracene oil used as solvent. The experiments were carried out in the range of 15–60 atm for initial hydrogen pressure, 360–440°C for reaction temperature, 1–5 for solvent to coal ratio and 0–20% of coal for catalyst loading which were chosen as process variables. Coal particle size and reaction time were kept constant as below 200 mesh and 30 minutes respectively, (Erdem 1987)

The product was analyzed in terms of total conversion, liquid yield and liquid product distribution determined as preasphaltenes, asphaltenes and oils. The oil fraction was further separated by column chromatography while the asphaltenes were separated into basic and acid/neutral fractions. The preasphaltenes were divided into two fractions as carbene (CS₂ solubles) and carboid (CS₂ insolubles). (Inanç 1989)

The oil yield is mostly affected by the catalyst loading which shows to a certain extent that the conversion of asphaltenes to oils is a catalytic step. The selected process variables showed a positive trend with respect to the yield of hexane eluted oil which is the desired product of liquefaction.     

VARIATION IN THE CHEMICAL NATURE OF ASPHALTENES WITH THE PROCESS,THE COAL AND THE REACTION CONDITIONS

ABSTRACT

Average structure data for twelve asphaltenes are reported, based on ¹³C- and H- n.m.r. spectroscopy combined with elemental, molecular weight and functional group analyses. The asphaltenes were from supercritical gas extraction, flash pyrolysis and hydrogenation of a brown and a bituminous coal. The effect of the reaction temperature and, for hydrogenation, the catalyst and solvent on the nature of the asphaltene produced was studied. The asphaltene obtained from supercritical gas extraction of the brown coal at 350°C was the least aromatic (f_a = 0.44) with the highest H/C atomic ratio (1.16) and probably consists mainly of single ring aromatlcs with about half of the aromatic sites substituted. A significant proportion of the carbon in this asphaltene is in long alkyl chains and the hydroxyl content is high. Whereas, the asphaltenes produced by hydrogenatlon of the bituminous coal at 450°C were far more aromatic with more highly condensed but less substituted aromatic ring systems and few, if any, long alkyl chains, together with a lower hydroxyl content. The asphaltenes obtained from the brown coal are less aromatic with less condensed aromatic ring systems but a higher degree of aromatic substitution than those produced from the bituminous coal under the same conditions. The asphaltenes formed at 450°C had lower H/C atomic ratios, molecular weights and degree of aromatic substitution, but higher aromaticities Ohan those produced at 35O°C or 400°C under like processing conditions. The asphaltene produced in the presence of both stannous chloride catalyst and tetralin was less aromatic than when either of these species was absent.     

Kinetics of desulfurization by electrochemical oxidation in an emulsifying electrolyte

Diesel with S content 624.4 µg/g was directly used, and a constant current of 500 mA was proposed in this work. Emulsification as an enhancement method was used to enhance the interphase mass transfer. After emulsifying electrochemical oxidation–extraction, the sulfur content of diesel decreased to 8.1 µg/g and the desulfurization efficiency reached 98.71 %. On comparingwith the non-emulsifying electrochemical oxidation–extraction, it has a highly efficient deep desulfurization.

The analysis also found that the effect of emulsion and non-emulsion extraction desulfurization process on electrochemical oxidation has great difference under the same operating conditions, and parameters such as the order, reaction rate and activation energy of the two kinds of oxidation desulfurization reaction were studied. The results showed the oxidative desulfurization reaction is the first reaction. When the temperature reached T₂, the oxidation rate constant of the emulsion/non-emulsion system was 0.0199 min^?1 and 0.0179 min^?1, respectively. When the temperature reached T₁, the oxidation rate constant of the emulsion/non-emulsion system was 0.0375 min^?1 and 0.0346 min^?1, respectively. According to Arrhenius' law, the apparent activation energy of sulfur compounds in the raw oil is E_a (emulsion) = 6.9783 kJ/mol and E_a (non-emulsion) = 9.1826 kJ/mol, respectively.     

Comparison of Different Power-law Kinetic Models for Hydrocracking of Asphaltenes

Abstract

Hydrotreating of Maya crude oil was carried out at a pilot plant scale under the following reaction conditions: pressure of 70–100 kg/cm², hydrogen-to-oil ratio of 5,000 ft³/bbl, temperature of 380°C–420°C, and space-velocity of 0.33–1.5 h^?1. Asphaltenes were precipitated from the feed and from all hydrotreated products using n-heptane as solvent. Hence, variations in asphaltenes concentration were obtained as a function of reaction conditions. Three different kinetic models were studied: a simple power-law model, a modified power-law model which assumes a parallel path reaction for asphaltenes hydrocracking with the same reaction order for more reactive and less reactive asphaltenes, and the same modified power-law model with different orders for both types of asphaltenes. This latter model exhibited the best fit of experimental asphaltenes concentrations.     

Kinetic Modeling of Hydrocarbon Conversion to Asphaltenes in Sulphur-treated Asphalts

Abstract

A study was made of the kinetics of the conversion of the hydrocarbon constituents of residual asphalts to asphaltenes at temperatures of 210–250°C. The reactions occurring led to the manifold increases in the composition of asphaltenes. Kinetic rate parameters were determined at different temperatures and the temperature effect was correlated by Arrhenius dependency. The reaction order was found to vary with temperature, increasing from 1.60 and yielding a maximum order of 4.2 at 250°C, thus confirming other results obtained in the literature. An activation energy of 266.0 kJ/mol was also recorded which is quite lower than 373 kJ/mol reported for the noncatalytic reaction. The overall effect of the catalyst employed was the reduction of the temperature at which maximum asphaltene yield could be obtained.     

Steady State Size Distribution of Asphaltenes by Flocculation From Toluene–n-Heptane Mixtures

Abstract

The aggregation mechanisms of asphaltenes have been the subject of several recent studies. In this work, we have studied the effect of inhibitors on size distribution of asphaltene particles, in solutions containing toluene and mixtures of n-heptane and toluene. The asphaltenes used have been extracted from Marlim crude oil, using a modified procedure IP-143/82. Several solutions containing one percent volume of asphaltenes have been prepared in pure toluene and in toluene and n-heptane mixtures with and without inhibitors and have been homogenized during a period of 24 h. The particles sizes were determined by filtering the solutions through a set of standard filters ranging from 0.45 to 0.02 µm pore size. In addition, from the saturated filtered solution of asphaltene in toluene, three other solutions were prepared having 10, 20, and 30% volume of n-heptane and were homogenized for 24 h. Again the size distribution of precipitated particles was obtained by filtering. The concentration of asphaltenes remaining in the solution was measured directly by evaporation or by spectroscopy. The results have shown that large part of asphaltenes remain as colloidal particles in the size range tested in toluene solution without inhibitor. On the solutions in which inhibitors were used, one of the inhibitors effectively prevented flocculation, concentrating the asphaltene particles on the smaller size range even on mixtures containing 20 and 30% volume of n-heptane, which is a strong flocculating agent.     

Wild melon: a novel non-edible feedstock for bioenergy

In the present research work, a non-edible oil source Cucumis melo var. agrestis(wild melon) was systematically identified and studied for biodiesel production and its characterization. The extracted oil was 29.1% of total dry seed weight. The free fatty acid value of the oil was found to be 0.64%, and the single-step alkaline transesterification method was used for conversion of fatty acids into their respective methyl esters. The maximum conversion efficiency of fatty acids was obtained at 0.4 wt% Na OH(used as catalyst), 30%(methanol to oil, v/v) methanol amount, 60 ℃ reaction temperature,600-rpm agitation rate and 60-min reaction time. Under these optimal conditions, the conversion efficiency of fatty acid was 92%. However, in the case of KOH as catalyst, the highest conversion(85%) of fatty acids was obtained at 40%methanol to oil ratio, 1.28 wt% KOH, 60 ℃ reaction temperature, 600-rpm agitation rate and 45 min of reaction time.Qualitatively, biodiesel was characterized through Fourier transform infrared spectroscopy(FTIR) and gas chromatography and mass spectroscopy(GC–MS). FTIR results demonstrated a strong peak at 1742 cm~(-1), showing carbonyl groups(C=O)of methyl esters. However, GC–MS results showed the presence of twelve methyl esters comprised of lauric acid, myristic acid, palmitic acid, non-decanoic acid, hexadecanoic acid, octadecadienoic acid and octadecynoic acid. The fuel properties were found to fall within the range recommended by the international biodiesel standard, i.e., American Society of Testing Materials(ASTM): flash point of 91 ℃, density of 0.873 kg/L, viscosity of 5.35 c St, pour point of-13 ℃, cloud point of-10 ℃, total acid number of 0.242 mg KOH/g and sulfur content of 0.0043 wt%. The present work concluded the potential of wild melon seed oil as excellent non-edible source of bioenergy.     

EFFECT OF Ni-Mo CATALYST MESOPORE DIAMETER ON CATALYTIC ACTIVITIES IN HYDROTREATING OF COAL LIQUID

ABSTRACT

A mixed 450^°C+ vacuum residue obtained from Austra-rian brown coal-derived oil with hydrogenated creosote oil was hydrogenated to elucidate the effect of catalyst mesopore diameter on the activities of Ni-Mo-γ-Al2O3 catalysts. Catalyst activities, especially for the heavy fraction in feedstock, were evaluated mainly by the conversion of 350^°C+ residue to 35O^°C ^? oil (HDC), hydrodesulfurization (HDS) and hydrodenitrogenation (HDN). These decreased in the order of HDS > HDN > HDC; whereas the deactivation rate during 50 hours on stream decreased in the order of HDC > HDN > HDS due to carbonaceous deposits on the catalyst. HDC, HDS and HDN rates per unit surface area of catalyst indicated that the HDS reaction was more strongly influenced by pore diffusion than the HDN and HDC reactions. The heavy ends in feedstock (such as asphaltenes) contained higher amounts of oxygen and nitrogen compounds. These polar compounds tended to be accumulated on the catalyst surface as the precursors for the formation of carbonaceous material deposits. The profile of carbon inside catalyst particle indicated that mesopore size of 22.6 nm might be satisfactory for reactant molecules to diffuse to the center of catalyst particle and access all of the active sites effectively.     

Conversion of n-heptane over different catalysts: Effect of catalyst-to-oil ratio and temperature

Catalytic cracking of n–heptane was investigated over various catalysts including ZSM-5, MCM-41, USY and mordenite. The influence of reaction temperature and catalyst-to-oil ratio was investigated in the case of ZSM-5 as more favorable catalyst in terms of conversion and light olefins yield. The highest n-heptane conversion of 97.3 wt.% was achieved over USY zeolite. Both conversion and olefin selectivity were increased by temperature over ZSM-5 zeolite. Increasing catalyst-to-oil ratio enhanced conversion with no significant changes in olefins selectivity. The highest olefin production was achieved over ZSM-5 zeolite in catalyst-to-oil ratios of 1.5 and 3.0 (g/g) at 550°C.     

CATALYTIC HYDROTREATMENT OF PETROLEUM RESIDUE

ABSTRACT

Iraqi reduced crude (350°C+) with a sulfur content of 4.3 wt% and a total metal content (Ni+V) of 141 WPPM was n-heptane deasphalted at specified conditions. The deasphalted oil (97.2 wt% of original residue) contains 4.1 wt% of sulfur and 103 ppm of metal. The original reduced crude and deasphalted oil were hydrotreated on a commercial Ni-Mo-alumina catalyst presulfided at specified conditions in a laboratory trickle-bed reactor. The reaction temperatures varied from 300 to 420°C with the liquid hourly space velocity (LHSV) ranging from 0.37 to 2.6 h^?1. Hydrogen pressure was kept constant throughout the experiments at 6.1 MPa, with a hydrogen/oil ratio of about 300 NLL^?1 (normal liters of hydrogen per liter of feedstock). Analysis for sulfur, nickel, vanadium and n-pentane asphaltenes were carried out for hydrotreated products from both the original residue and the deasphalted oil. The comparison of the results obtained for the hydrotreatment of deasphalted oil and original reduced crude indicates that the removal of sulfur, nickel and vanadium was higher for the deasphalted oil than those obtained for the non-deasphalted residue over the entire range of conversion. The exclusion of extremely high molecular weight asphaltenes by n-heptane deasphalting seems to improve the access of oil into catalyst pores resulting in higher desulfurization and conversion of the lower molecular weight asphaltenes. The sulfur content of n-pentane precipitated asphaltenes remained unchaneed with LHSV for various temperature for hydrotreated products produced from both deasphalted oil and original reduced crude.     

LIQUEFACTION OF BEYPAZARI LIGNITE USING NiCl2-KCl-LiCl CATALYSTS. 1. DIFFERENCE IN SOLID AND MOLTEN SALT CATALYSIS

ABSTRACT

Liquefaction of Beypazan lignite in tetralin using NiCl₂-KCl-LiCl (14:36:50 molar percentages) as catalyst was investigated. Effects of the catalyst/lignite ratio and temperature were determined in experiments done at 275°C, 300°C and 360°C. Liquid products were separated into oils, asphaltenes and asphaltols by a solvent extraction method. Yield of liquefaction increased with temperature in all experiments, the highest yield was observed in experiments performed at the eutectic temperature of the catalyst mixture. The highest yields of oils were 20% and 30% with a catalyst/coal ratio of 0.5 at 275°C and 300°C, respectively. The activity of the catalyst increased in experiments in which the catalyst was molten. The yield of asphaltenes were not affected with increases in the catalyst/coal ratio in the experiments done at 275°C or 300°C in which the catalyst mixtures were in solid state. Asphaltene yields decreased from 25% to less than 5% with increasing values of catalyst/coal ratio and the asphaltol yields remained constant at 10% between catalyst/coal ratios of 0.25 and 1.00 and suddenly increased to 30% and 40% for catalyst/coal ratios of 1.50 and 2.00, respectively, at 360°C. The molecular weights of the oils decreased from 340 to a minimum value of 245 as the catalyst/coal ratio was increased from 0 to 1.00 in experiments done at 360°C where the catalyst was molten. As the catalyst/coal ratio was further increased from 1.00 to 2.00 the molecular weight increased to 310.It seemed that the N1Cl₂-KCl-LiCl catalyst mixture in all catalyst/coal ratios was more efficient in molten phase than it was used as a solid mixture.     

超细负载型Ni-Mo/Al2O3催化剂在渣油加氢裂化中的应用

针对渣油固定床加氢工艺催化剂易结焦失活以及悬浮床加氢工艺催化剂活性偏低的问题,将能悬浮在渣油中的超细负载型催化剂(Ni-Mo/Al2O3)应用于渣油的加氢裂化反应,并在高压釜中考察了反应条件对新疆减压渣油(XJVR)转化率的影响,其中催化剂添加量(质量分数)的考察范围为1%～10%、反应温度为410～450℃、反应时间为0.5～2.5 h、氢气初始压力为5～9 MPa。结果表明,催化剂的添加量对渣油、沥青质以及残炭转化率的影响都很小,但增加催化剂添加量能明显地促进硫的转化,即在此催化体系下,渣油的裂化反应以热反应为主,而加氢脱硫反应则由催化剂的活性中心所决定;反应温度对渣油、残炭、沥青质以及硫的转化率的影响较大,随着反应温度的提高,渣油、残炭、沥青质以及硫的转化率都呈上升的趋势,且前三者的上升趋势更为显著;延长反应时间对反应转化率的影响与提高反应温度所得到的结果类似;当氢气严重过量时,再提高氢气压力对硫转化率没有影响,但可在一定程度上促进残炭和沥青质的加氢反应。     

Adsorption of nitrogen compounds from diesel fuels over alumina-based adsorbent towards ULSD production

The aim of this work is to estimate some nitrogen (N)-adsorption properties and the N-adsorption capacity (q) required for commercial application in the ultra-low sulfur diesel production. Hydroxyl (OH) groups and interactions among the commercial adsorbent Selexsorb® CDX (CDX) and pyridine and indole were studied by means of Fourier transform infrared spectroscopy. The adsorption of N-compounds from three diesel fuels over CDX was estimated at CDX/fuel ratio: 0.01–0.09 g/g, Contact time: 1–60 m, 303 K, and 0.078 MPa in a batch setup. It was concluded that an appropriate N-adsorbent should have high densities of suface OH groups and Lewis and Brønsted strong-acid sites and a q ≥ 0.70 mmol/g.     

Correlation Between Properties of Asphaltenes and Precipitation Conditions

Abstract

Asphaltenes from three crude oils were precipitated by using a pressurized system. Different conditions during the precipitation of asphaltenes were studied: pressure was varied between 15 and 45 kg/cm² and temperature between 40°C and 100°C. The effect of contact time and solvent-to-oil ratio was also studied in the range of 0.5–6 hr and 2:1 to 5:1 mL/g, respectively. Asphaltenes properties were analyzed as a function of pressure and temperature. It was found that in a deeper way temperature influences the asphaltenes properties than pressure in the range studied in this work. Asphaltenes properties were highly dependent on the nature of crude oil. Various correlations were developed and experimental and calculated asphaltenes contents and properties were in good agreement with absolute error less than 0.2%.     

Spectrophotometric Measurement of Asphaltene Concentration

Abstract

Typically, when ultraviolet and visible absorbance of asphaltenes is employed to measure asphaltene concentration, linear calibrations of absorbance vs. asphaltene concentration are prepared from a sample of asphaltenes in a given solvent. This calibration is shown to be sensitive to: (a) the inorganic solids content of the asphaltenes; (b) physical–chemical differences between asphaltenes from different sources or extracted with different methods; and (c) selective adsorption of asphaltenes on liquid–liquid or solid–liquid interfaces. Calibration constants were determined at wavelengths of 288 and 800 nm for samples of Athabasca and Cold Lake asphaltenes obtained using different extraction methods, from precipitation experiments, and from adsorption experiments on water-in-hydrocarbon emulsions and on powdered metals. It was found that the inorganic solids content did not affect absorbance but the asphaltene concentrations must be corrected to a solids-free basis for accurate results. Calibration constants were found to correlate to the average associated molar masses of the asphaltenes. Therefore, any change in molar mass of asphaltenes during the course of an experiment may change the calibration constant. Partial precipitation and the selective adsorption of asphaltenes can lead to a change in the molar mass of asphaltenes left in solution. The corresponding change in the calibration constants can lead to errors of 5–25% in the estimated concentration.     

Hydrothermal synthesis of unsupported MoS2 as catalyst for hydrodesulfurization of gas oil

Hydrothermal synthesis with ammonium heptamolybdate and thiourea as precursors was used to obtain an unsupported MoS₂ catalyst. The catalyst was obtained in sulfide state directly at mild reaction conditions (i.e., 180°C during 5 h). After catalyst was obtained, it was characterized through nitrogen physisorption, transmission electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Catalytic evaluation was carried out in a batch reactor at 350°C, 55 bar of hydrogen pressure, 750 rpm, and 3 h of reaction time using straight-run gas oil (SRGO) as feedstock. A commercial CoMo/Al₂O₃ catalyst was used for comparison of activity. The synthesized catalyst was slightly more active toward SRGO hydrodesulfurization than commercial one keeping constant the sulfur removal after two runs.     

The catalytic deacidification of acidic crude oil using Cu-doped alkaline earth metal oxide catalysts

Naphthenic acids (NAs) tend to cause operational problems that can lead to the deactivation of catalysts. To overcome the problem, catalytic deacidification was introduced utilizing an ammonia solution in ethylene glycol with the aids of alkaline earth metal catalyst with alumina as a support. The initial total acid number observed for NAs in n-dodecane was 4.21 mg KOH/g. In total, 1,000 mg/L of 0.4% NH₃-EG were used as the acid removal agent. Calcium, barium, and magnesium catalysts were tested in this study. The results showed Cu/Ca/Al₂O₃ was found to be the best catalyst that could be used to enhance the reaction.     

An improved gravimetric method applied to co-processing of polyethylene terephtalate and petroleum blend using HY zeolite as a catalyst

The co-processing of petroleum and polyethylene terephthalate (PET) was carried out in the presence and absence of a catalyst in an open vessel batch reactor at temperatures of 200, 300, 400, and 500 °C, which corresponds to temperatures of distillation and cracking. The catalyst used was the acidic HY zeolite, which is widely used in petroleum refining. The catalytic co-processing was carried out with the PET–oil charge, at a mass ratio of 1:1, containing 10% of HY zeolite. The conversion degree was measured by knowing the initial sample mass and amount of degraded material for each temperature and reaction time, using an improved gravimetric method consisting of a precision balance and an oven with a heating rate controller. The conversion values obtained were compared for petroleum and PET samples with and without the zeolite catalyst. At temperatures of 200 and 300 °C, the PET showed low conversions, about 5–10%. However, for the catalytic co-processing of PET–oil/HY at these same temperatures, an increase in conversion to about 25–30% was observed. At temperatures of 400 and 500 °C, conversions above 90% were obtained for the two samples, with a subsequent reduction in the activation energy, from 76 kJ mol^?1 (PET) to 56 kJ mol^?1 (PET–oil/HY). The decrease in the activation energy proved the efficiency of the HY zeolite and the synergistic effect when PET was blended to the oil for the catalytic co-processing, proving to be a viable alternative for the chemical recycling of PET in the petroleum industry.     

Optimization of reaction condition on the product selectivity of Fischer–Tropsch synthesis over a Co–SiO2/SiC catalyst using a fixed bed reactor

The Fischer–Tropsch (FT) synthesis is an important method for producing valuable key raw materials such as heavy and light hydrocarbons in various industries. The effects of process conditions (temperature of 503–543 K, pressure of 10–25 bar, and gas hourly space velocity (GHSV) of 1,800–3,600 Nml g _cat^?1 h^?1) on the FT product distribution using Co–SiO₂/SiC catalyst in a fixed bed reactor were studied by the design of experimental procedure and the Taguchi method. The optimization of the reaction conditions for the production selectivity of C₂–C₄ and heavy hydrocarbon (C₅₊) that has not been completely indicated elsewhere was investigated. The effect of operating conditions on the average carbon number distribution, dispersion, and skewness was also studied. Data analysis indicated the highest selectivity for the light hydrocarbons at a pressure of 20 atm, GHSV of 2,400 Nml g _cat^?1 h^?1, and temperature of 543 K resulting in a highest selectivity for heavier hydrocarbons (C₅₊) and the minimum amount of methane in the reaction products that is optimal at the pressure of 10 atm, GHSV of 1,800 Nml g _cat^?1 h^?1, and a temperature of 503 K. Furthermore, based on the surface plot, temperature has more significant effects than the other parameters. In addition, the obtained results indicated that the maximum average number of carbon was obtained in a pressure of 10 atm and a temperature of 503 K.     

Synthesis and characterization of Ni-Mo catalyst using Jatropha curcas leaves as carbon support and its catalytic activity for hydrotreating of gas oil,Jatropha oil,and their blends

A novel carbon-based Ni-Mo catalyst has been synthesized successfully from Jatropha curcas leaves using boric acid as a surface modifying agent. The Ni-Mo catalyst prepared on Jatropha curcas leaves had shown BET surface area of 316 m²/g whereas the Ni-Mo catalyst prepared without boric acid activation had shown BET surface area of only 14 m²/g. XRD and SEM data have shown that the active catalyst particles such as Ni and Mo have been found to be uniformly distributed. The inventive catalyst was studied for hydrotreating of gas oil, Jatropha curcas oil and 20% Jatropha oil in gas oil at 370°C, 90 bar H₂ pressure, liquid hour space velocity of 1 h^?1, and gas-to-oil ratio of 500 Nm³/m³ and the results obtained were found to be comparable with that of the commercial Ni-Mo catalyst supported on alumina.