Use of ultrasound in petroleum residue upgradation

Conventional processes for the upgradation of residual feedstocks, viz., thermal cracking and catalytic cracking are carried out in the temperature range of 400–520°C. Such high temperatures can in principle be substituted by acoustic cavitation. In the present work, two vacuum residues, namely, Arabian mix vacuum residue (AMVR) and Bombay high vacuum residue (BHVR) and one asphalt, viz., Haldia asphalt (HA) were subjected to acoustic cavitation for different reaction times from 15 min to 120 min at ambient temperature and pressure. An attempt has been made to seek a performance comparison of two devices of acoustic cavitation, namely, ultrasonic bath and ultrasonic horn with regard to their ability to upgrade the petroleum residues to lighter, more value‐added products mainly the hydrocarbons boiling in the range of gas oil fraction. Another attempt has been made to study the effect of ultrasound on the upgradation of the residue when it is emulsified in water with the help of different surfactants. For all the cases, a kinetic model has been developed based on the constituents of the residue so as to get an insight into the reaction mechanism. The study revealed that ultrasonic horn is more effective in bringing about the upgradation than ultrasonic bath and that the acoustic cavitation of the aqueous emulsified hydrocarbon mixture could reduce the asphaltenes content to a greater extent than the acoustic cavitation of non‐emulsified hydrocarbon mixture. The reduction in asphaltenes content of BHVR was found to be more followed by AMVR followed by HA. The variation in the rate constants was found to be feed specific and the rate constants for the conditions of maximum conversion of asphaltenes to gas oil for AMVR, BHVR and HA were found to be 0.29 × 10^?4 s^?1, 1.4 × 10^?4 s^?1 and 0.23 × 10^?4 s^?1, respectively.     

CFD simulation of acoustic cavitation in a crude oil upgrading sonoreactor and prediction of collapse temperature and pressure of a cavitation bubble

In acoustic cavitation, high pressure and temperature are generated due to cavitation bubble collapse in the liquid bulk around the bubble which causes physical and chemical changes in the liquid. In this study, pressure distribution in water caused by ultrasonic wave propagation in a sonoreactor was investigated. Active cavitation zones were determined by calculating acoustic pressure threshold for cavitation inception and compared with experimental results. Collapse pressure and temperature were predicted 3000 atm and 3200 K, respectively, for crude oil at temperature of 25 °C by evaluating cavitation bubble dynamics in the exerted acoustic field. As a consequence, the huge amounts of energy generated by this phenomenon can be applied for changes in oil properties and crude oil upgrading.     

Transformation of petroleum asphaltenes in supercritical water

The transformation of petroleum asphaltenes in supercritical water was studied. The experiments were performed in autoclave at temperature 380 °C and pressure 226 atm with stirring for 3 h, medium density was about 0.33 g/cm³. The reaction resulted in the formation of gas products, about 4.3%, and an insoluble residue (coke) with about 48.6% yield. The remaining products were separated into fractions by consecutive dissolution in hexane (30.0%), benzene (10.6%), and chloroform (5.7%). The properties of the obtained products were studied with FT-IR spectrometry and ¹H NMR spectroscopy. The method of simulated distillation was used to demonstrate that the fractional composition of the hexane-soluble part of the products is close to the fractional composition of a mixture of the diesel fraction and vacuum gas oil of the corresponding oil in 1:1 ratio. The obtained data support the conclusion that asphaltene cracking proceeds in SCW, with most probable main processes being dealkylation of substituents in the aromatic fragments of molecules and aromatization. This leads to formation of gaseous products and hexane-soluble fraction consisting of lighter aliphatic and aromatic compounds, as well as carbonized solid residue.     

Studies on thermal cracking behavior of residual feedstocks in a batch reactor

Thermal cracking of residual fractions has gained interest of refiners due to increasing demand of middle distillates and at the same time decline in demand of fuel oils. The present study is an attempt to gain deeper insight into the thermal cracking behavior of residual feedstocks in terms of certain key characteristics. Laboratory scale experiments on a 400 ml capacity stainless steel batch reactor were conducted with four residual feedstocks of Indian and Middle East origin—North Gujarat short residue (NGSR), Visbreaker feed from Mathura refinery (MVBF), Bombay High short residue (BHSR) and Asphalt from Haldia refinery (HRA), with asphaltene content varying in the range 1.85-10.15 wt%. The cracked products were separated by distillation up to 500 ^°C. The distillate (500 ^°C-) was analyzed by ASTM D2887 (SIMDIST) method and obtained data were classified into lumps, namely Gas (C₅-), Gasoline (IBP-150 ^°C), Light Gas Oil (150-350 ^°C) and Vacuum Gas Oil (350-500 ^°C) prior to detailed data analysis. The analysis of results reveals that the thermal cracking of petroleum residues follows first order kinetics. The rate constants and activation energies have also been estimated.     

Microstructural study of asphaltene precipitated with methylene chloride and n-hexane

This work presents a study of the microstructure, molecular structure and elemental composition of asphaltene precipitated from vacuum residue using a solvent mixture. The infrared spectroscopy (FTIR) results show vibration bands of functional groups such as aromatic C-H (4 adj H and 1 adj H) and sulfoxide (C₂SO). Low vacuum scanning electron microscopy (LV-SEM) reveals a highly porous and a smooth surface asphaltene. C, S and V are the main elements identified by energy dispersive X-ray spectroscopy (EDS) analysis, though some variations in concentration were observed between the porous and the smooth surface asphaltene. Transmission electron microscopy (TEM) analysis shows that asphaltenes are constituted by nanometric particles (micelles) of ∼50 nm in diameter. These particles conform agglomerates (flocs) from ∼350 to ∼550 nm in size, some of them in layer arrangement with a tendency to graphitize. These results reveal important information about flocculation processes of the asphaltene.     

Effect of ultrasound on bubble breakup within the mixing chamber of an effervescent atomizer

Gas bubbles introduced into a liquid in the mixing chamber help to break up the liquid into fine droplets on being expanded to the ambient pressure. The passage of gas bubbles through the orifice of the nozzle requires that the size of the bubbles be much smaller than the diameter of the orifice. In the present work, the effectiveness of 20 kHz ultrasound to increase number density of fine bubbles within the mixing chamber of an effervescent atomizer by breaking up bubbles introduced in it by an aerator was investigated. Bubbles of initial size in the range of 5-10 mm were shown to get disintegrated into clusters of micron and sub-micron sized bubbles. A fine spray was produced in the presence of ultrasound at a gas-to-liquid mass flowrate ratio (GLR) of 0.063%. The half-cone angle of spray was in the range of 6-10°, which compares favorably with conventional atomizers. The experimental findings of bubble breakup were theoretically modeled by the Rayleigh-Plesset equation. The results of the model indicate that bubbles having initial radius less than 3 mm undergo growth and subsequent disintegration at 20 kHz for the given acoustic pressure of 0.3 MPa.     

Production of biodiesel by ultrasound assisted esterification of Oreochromis niloticus oil

This paper evaluates the production of methyl esters from Oreochromis niloticus (Nile tilapia) oil and methanol. The reaction was carried out applying low-frequency high-intensity ultrasound (40 kHz) under atmospheric pressure and ambient temperature. Response surface methodology (RSM) was used to evaluate the influence of alcohol to oil molar ratio, catalyst concentration (sulfuric acid) and temperature on the yield of O. niloticus oil into methyl esters. Analysis of the operating conditions by RSM showed that the most important operating condition affecting the reaction was the alcohol to FFA molar ratio. The highest yield observed was of 98.2% after 90 min of reaction. The optimal operating condition was obtained applying an alcohol to oil molar ratio of 9.0 and a catalyst concentration of 2.0% w/w and temperature of 30 °C.     

Hydrogen production from heavy oil in the presence of calcium hydroxide

A new hydrogen production method, the HyPr-RING process was applied to a vacuum residue of Arabian light crude oil to clarify the effects of added water, calcium hydroxide, which absorbs carbon dioxide, and the reaction temperature. It was determined that when a sufficient amount of calcium hydroxide was present, it provided enough water to produce hydrogen and additional water was not necessary. To consume all of the carbon dioxide in 1 mol of carbon from the feedstock, 25 mol% of calcium hydroxide was needed and hydrogen production was saturated at 50 mol%. Carbon conversion was dependent mainly on the temperature and was slightly dependent on water and pressure. The reaction pressure was as low as 4.2 MPa. Thermal decomposition of the feedstock was the dominant reaction below 600 °C, which produced methane.     

Characterization of an ultrasonic system using wavelet transforms

A new method has been developed for the determination of the spatial distribution of the cavitation intensity in an ultrasound processor. The method uses wavelet transform analysis of the acoustic emission profiles. The periodic modulation of the acoustic pressure field in an ultrasound processor causes unsteady radial motion of the bubbles, resulting in non-stationary acoustic emission profiles that cannot be analyzed by Fourier transform. The cavitation intensity has been judged experimentally and numerically. The experimental method used the “cavitation noise coefficient” defined as the sum of the energy at different scales (or levels) in the wavelet transform of the measured signal containing the subharmonic and harmonics of the fundamental frequency. The numerical method involved the simulation of the radial motion of a bubble and the pressure waves radiated by it, applying experimentally measured acoustic pressure signals as the forcing function. The numerically predicted spatial variation of the cavitation intensity was in agreement with the experimental measurements. It is proposed that the conical divergence of the acoustic waves from the transducers and the differences in the electrical and acoustical characteristics of the adjacent transducers in the bath give rise to a non-uniform cavitation intensity distribution.     

Ultrasonically initiated free radical‐catalyzed emulsion polymerization of methyl methacrylate (i)

The emulsion polymerization of methyl methacrylate initiated by ultrasound has been studied at ambient temperature using sodium lauryl sulfate as the surfactant. The investigation includes the: (1) nature and source of the free radical for the initiation process; (2) effects of different types of cavitation; and (3) dependence of the polymerization rate, polymer particle number generated, and the polymer molecular weight on acoustic intensity, argon gas flow rate, surfactant concentration, and initial monomer concentration. It was found that the polymerization could be initiated by ultrasound in the emulsion systems containing methyl methacrylate, water, and sodium lauryl sulfate at ambient temperature in the absence of a conventional initiator. The source of the free radical for the initiation process was found to come from the degradation of the sodium lauryl sulfate, presumably in the aqueous phase. The weight average molecular weight of the poly(methyl methacrylate) obtained varied from 2,500,000 to 3,500,000 g mol⁻¹, and the conversion for polymerization was up to 70%. Deviations from the Smith–Ewart kinetics were observed. The polymerization rate was found to be proportional to the acoustic intensity to the 0.98 power; to the argon gas flow rate to the 0.086 power; to the surfactant concentration to the 0.08 power, with the 0.035M–0.139M surfactant concentration range; and to the surfactant concentration to the 0.58 power, with the 0.139M–0.243M surfactant concentration range. The polymerization rate was found to increase with increasing initial monomer concentration up to a point where it became independent of initial monomer concentration. The polymer particle number generated per milliliter of water was found to be proportional to the acoustic intensity to the 1.23 power; to the argon gas flow rate to the 0.16 power; to the surfactant concentration to the 0.3 power, with the 0.035M–0.139M surfactant concentration range; and to the surfactant concentration to the 1.87 power, with the 0.139M–0.243M surfactant concentration range. The polymer weight average molecular weight was found to be proportional to the acoustic intensity to the 0.21 power, and to the argon gas flow rate to the 0.02 power. It was found to be inversely proportional to the surfactant concentration to the 0.12 and 0.34 power, with the 0.035M–0.139M and the 0.139M–0.243M surfactant concentration ranges, respectively. The polymer yield and polymerization rate were found to be much larger than those obtained from an ultrasonically initiated bulk polymerization method. The polymerization rates obtained at ambient temperature were found to be similar to or higher than those obtained from the conventional higher temperature thermal emulsion polymerization method. This investigation demonstrated the capability of ultrasound to both initiate and accelerate polymerization in the emulsion system, and to do this at a lower temperature that could offer substantial energy savings. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 797–825, 1999     

Design and technical evaluation of a conceptual process for transferring solvent precipitated asphaltenes into water utilising surfactant phase behaviour

Experiments are described which demonstrate that asphaltenes precipitated from a refinery tar using an excess of n-heptane spontaneously partition into a contacting water phase in the presence of an ethoxylated nonionic surfactant by effecting a temperature change. The process appears to be related to the temperature-dependent phase behaviour of the particular surfactant. Hot (ca. 80–90 °C) aqueous octa(ethyleneoxy) nonylphenylether (NPE8) and the heptane-diluted tar, were thoroughly and vigorously mixed for a short time and then allowed to stand and cool under quiescent conditions. A distinct oil/water interface rapidly appeared after the mixing had stopped and, at a specific temperature, asphaltene particles were observed to begin to “rain” into the lower aqueous phase, producing an aqueous asphaltene suspension. The temperature at which asphaltene transfer occurred was close to the phase inversion temperature of the NPE8/heptane system. Subsequent to different laboratory batch experiments, a larger-scale semi-continuous operation was carried out allowing other aspects of the process to be investigated. Rigorous economic analyses of the process have not been included in this study, although it is apparent that surfactant recycling would need to be ensured in order to approach commercial viability, even if the technical concepts translate well to large-scale operation.     

Co-liquefaction of lignite and sawdust under syngas

Individual and co-liquefaction of lignite and sawdust (CLLS) under syngas was performed in an autoclave and the effects of temperature, initial syngas pressure, reaction time and ratio of solvent to coal and biomass on the product distribution of CLLS were studied. Sawdust is easier to be liquefied than lignite and the addition of sawdust promotes the liquefaction of lignite. There is some positive synergetic effect during CLLS. In the range of the experimental conditions investigated, the oil yield of CLLS increases with the increase of temperature, reaction time (10-30 min) and the ratio of the solvent to the feedstock (0-3), but varies little with the increase of initial syngas pressure. Accordingly, the total conversion, the yield of preasphaltene and asphaltene (PA + A) and gas, changes by the difference in operation conditions of liquefaction. The gas products are mainly CO and CO₂ with a few C₁-C₄ components. The syngas can replace the pure hydrogen during CLLS. The optimized operation conditions in the present work for CLLS are as follows: syngas, temperature 360 °C, initial cold pressure 3.5 MPa, reaction time 30 min, the ratio of solvent to coal and sawdust 3:1. Water gas shift reaction occurs between CO in the syngas and H₂O from coal and sawdust moisture during the co-liquefaction, producing the active hydrogen which increases the conversion of liquefaction and decreases the hydrogen consumption.     

Upgrading of bitumen with formic acid in supercritical water

Upgrading of bitumen was examined with formic acid in supercritical water (SCW) from 673 to 753 K and at a water/oil ratio from 0 to 3. Decomposition of bitumen in SCW + HCOOH gave higher conversions of asphaltene and lower coke yields than those of pyrolysis or with only SCW. Decomposition of bitumen was also conducted in SCW + H₂, SCW + CO, toluene and tetralin, which revealed that decomposition of asphaltene was promoted and coke formation was suppressed when using SCW + HCOOH. In SCW + HCOOH, an increase in the water/oil ratio promoted both decomposition of asphaltene and suppression of coke formation. Formic acid in SCW seemed to enhance the conversion of bitumen to lower molecular weight compounds because formic acid seems to produce active species in SCW. The low temperature region (ca. 723 K) was suitable for upgrading bitumen with formic acid in SCW since coke formation was strongly promoted at high temperature (>753 K). A reaction model was proposed and the model predicted that hydrogenation of the asphaltene core was important for the suppression of coke formation.     

沥青质含量对重油中氢气溶解度影响的研究

氢气是油品加氢工艺中重要的反应组分,其在石油馏分中的溶解性能是影响加氢工艺过程的关键因素。重油中氢气溶解度的数据较为匮乏,尤其是重油中沥青质组分对氢气溶解度的影响并未受到关注。采用高压搅拌釜对氢气在四种重油原料中的溶解度进行系统研究,获得了氢气在重油中溶解性能随温度和压力的变化规律,并考察了沥青质含量对氢气溶解性能的影响。结果表明,氢气在相同重油原料中的溶解度随温度和压力的升高而增大,并且在较高温度或压力条件下,压力或温度变化对氢气溶解性能的影响更加显著。利用Aspen Plus中的Flash模块结合PR状态方程建立氢气溶解度计算模型,并进行高温条件氢气溶解度的预测,表明常规加氢条件下加拿大油砂沥青减渣中氢气溶解度与氢耗之间的矛盾极为尖锐,其脱沥青油的氢气溶解性能得到较大改善,胶质和沥青质的脱除缓解了氢气溶解和氢耗之间的矛盾。     

Cracking behavior of asphaltene in the presence of iron catalysts supported on mesoporous molecular sieve with different pore diameters

Cracking of a mixture of petroleum asphaltene and 10 wt% Fe catalyst supported on mesoporous molecular sieve (SBA-15) possessing a hexagonal array of uniform mesopores has been studied with a fixed bed reactor at 573 K under atmospheric He. When average pore diameter of Fe/SBA-15 is varied between 4.5 and 15 nm, asphaltene conversion increases almost linearly with increasing pore diameter up to 12 nm and reaches 65%, though the increment is small beyond this value. On the other hand, yield of maltene formed is almost independent of the diameter and less than 15% but greatly improved by using pressurized H₂ in place of He. Although pore volumes of all Fe/SBA-15 catalysts decrease by mixing with feed asphaltene, the extent of the decrease is larger for the catalyst with a larger pore diameter, which shows that higher asphaltene conversion may arise from the presence of larger amounts of asphaltene molecules held inside the larger mesopores. The N₂ adsorption measurements reveal that pore structures of Fe/SBA-15 catalysts are almost unchanged after cracking and subsequent re-calcination to remove deposited coke. The X-ray diffraction analysis and temperature programmed oxidation after cracking suggest that Fe species are highly dispersed inside the mesopores and present as the sulfided phases at the outermost layer.     

Application of Taguchi method in optimization of desalination by vacuum membrane distillation

This research focuses on desalination via vacuum membrane distillation (VMD). In order to enhance the performance of VMD in desalination and to get more flux, effects of operating parameters on the yield of distillate water were studied. Four parameters at three levels were selected: temperature (35, 45, and 55 °C), vacuum pressure (30, 80, and 130 mbar), flow rate (15, 30, and 60 mL/s) and concentration (50, 100, and 150 g/L). Taguchi method was used to plan a minimum number of experiments. The optimal levels thus determined for the four factors were: temperature 55 °C, vacuum pressure 30 mbar, flow rate 30 mL/s and concentration 50 g/L. The results show that increasing temperature and decreasing vacuum pressure improve permeate flux. However, the permeate flux increases with increasing flow rate initially and then reaches to a maximum value at 30 mL/s and then decreases with increasing the flow rate.     

High-pressure viscosity of used motor oil/vacuum residue blends

The overall objective of this work was to characterize and model the temperature-pressure-viscosity relationship for used motor oil, and its blends with heavy petroleum residue, in a wide range of pressure and temperature. With this aim, used motor oil, and a vacuum residue commonly used as bituminous base were used as components of the blends. Blends of used motor oil and vacuum residue were prepared by mixing both components in a batch tank with a four-blade impeller. Subsequently, the mixtures were stored at room temperature. The rheological study was performed using a controlled stress rheometer, using both a conventional coaxial cylinder geometry, and a coaxial cylinder-pressure cell. From the experimental results obtained it is apparent that whilst the used motor oil behaves as a Newtonian liquid, the blends behave as non-Newtonian fluids, showing a shear-thinning behaviour in most of the shear rate range studied, at atmospheric pressure, in a temperature range comprised between 0 and 60 °C. The viscous flow curves results obtained at different differential pressures prove that the influence of time-dependent phenomena on viscosity is not significant in most of the shear rate range studied (between 1 and 100 s⁻¹). Pressure-temperature-viscosity relationship modelling, at constant shear rate, can be performed from pressure sweep data at constant temperature, temperature sweep data at constant pressure, or pressure-temperature sweep data. In this sense, the FMT predicts the above-mentioned relationship fairly well.     

Knowledge of petroleum heavy residue potential as feedstock in refining process using thermogravimetry

In the petroleum industry, previous knowledge of the feedstock's potential to produce light material is an important aspect of refining. For the evaluation of heavy petroleum fractions, thermogravimetry (TG), a thermal analysis technique, is considered a good analytical tool to determine the thermal behavior of these fractions at high temperatures. In the present work, TG analyses were made of petroleum distillation residues from different Brazilian oils. The apparent cracking activation energy of saturates, aromatics, resins and asphaltenes was also determined by TG. Saturates and aromatics showed values of 80-120 kJmol^− 1 at low conversions (< 0.3) and of 120-220 kJ mol^− 1 at high conversions (> 0.3). The thermal cracking activation energy of resins and asphaltenes occurred between 220-300 kJ mol^− 1, i.e., at higher values than those of aromatic and saturated fractions. This paper discusses the prediction of carbonaceous residue based on thermal analysis.     

Conversion of Calotropis procera biocrude to liquid fuels using thermal and catalytic cracking

With the fast depletion of petroleum reserves, renewable resources like biomass are acquiring great significance. Calotropis procera, a laticiferous arid plant is identified as a potential petrocrop. The dried biomass of C. procera was subjected to non-polar (n-heptane) solvent extraction. Biocrude so obtained is a rich source of tri terpenoid type of hydrocarbons. The biocrude was upgraded to useful liquid fuels using different conversion processes such as thermal and catalytic cracking (fluid catalytic cracking, FCC). The temperature, pressure and reaction time maintained during thermal conversions were 430 and 460 °C; 1.2 and 0.2 MPa; and 15 and 30 min, respectively. Catalytic cracking was carried out in continuous mode micro reactor varying the catalyst to feed ratio (3-7.03) and temperature (460-520 °C) aiming at maximization of lighter fractions (up to diesel range). High conversions (up to 92%) were obtained using FCC as compared to thermal process (57.7%). The HPLC analysis of the liquid fuels indicated that thermal cracking yielded a better quality fuel compared to FCC. The fuel obtained by FCC was found to contain large proportions of aromatics and poly-aromatic hydrocarbons (PAH).     

Application of Chebyshev polynomials to predict phase behavior of fluids containing asphaltene and associating components using SAFT equation of state

In this work, a thermodynamic model based on statistical association fluid theory (SAFT) is developed to predict the phase behavior of mixtures containing asphaltene contents. The SAFT equation of state is a good candidate for closing that gap between statistical mechanic models and the classical models dominated by cubic equation of state. A robust, fast and accurate computational algorithm based on Chebyshev polynomial approximation is developed to calculate the density and hence fugacity using SAFT equation of state in order to perform phase equilibrium calculations. Application of Chebyshev polynomials to approximate pressure-density function leads to an interpolation error of degree 10⁻¹³. Application of the proposed algorithm to calculate density of binary systems composed of ethanol and toluene shows an average relative deviation of 0.143% in the temperature range 283.15-353.15 K and for pressures up to 45 MPa. The proposed model is developed to predict the precipitation behavior of petroleum fluids containing asphaltene. The effect of pressure, temperature and solvent concentration on the amount of asphaltene precipitation is investigated. A good agreement with an AAD of 2.593% is observed between experimental and predicted amount of asphaltene precipitate. The model is also tested to investigate the effect of temperature and solvent concentration on asphaltene onset pressures (upper and lower). Again, an excellent agreement is observed between experimental and predicted values of the asphaltene onset pressure at different temperatures and solvent concentrations with an average 0.705% relative error. The accuracy of the proposed model is compared with WinProp software using Peng-Robinson equation of state with average 53.132% and 8.657% relative errors for the amount of asphaltene precipitate and onset pressure, respectively.