Method for determination of asphaltenes, paraffins, oils and resinous substances in residual petroleum products

Abstract

FIELD: analytical chemistry.SUBSTANCE: method for determining asphaltenes, paraffins, oils and resinous substances in residual petroleum products is disclosed, in which a precipitate comprising asphaltenes is obtained, the precipitate is filtered and washed with a solvent, then washed from the filter with hot benzene and dried; the filtrate comprising paraffins, oils and resins is poured onto the sorbent, sorption is carried out in a static mode, then the de-resined liquid phase is drained by decantation, the sorbent is washed and placed in a freezer until paraffin crystals appear, the paraffin precipitated as a result of crystallization in the cold is filtered, the filtrate with oils is evaporated on a rotary evaporator and the oils are dried, the paraffins are washed from the filter with hot toluene and dried; resinous substances are desorbed from silica gel by treating it 3-4 times with a mixture of solvents, the solution is evaporated and dried; the relative content of the component being determined in the original sample is calculated.EFFECT: simplification while simultaneously increasing the accuracy and reliability of determining the content of asphaltenes, resinous substances, oil fractions and paraffin hydrocarbons, using a single sample of the original sample.3 cl, 1 tbl, 1 ex

Description

[0001] The invention relates to analytical chemistry, namely, to methods for determining the content of asphaltenes, paraffins, oils and resinous substances (resins) in residual petroleum products of direct distillation of oil such as bitumen, fuel oil, tar, and can be used for use in laboratories of oil producing and oil refining companies, as well as in companies engaged in pipeline transportation of oil and petroleum products, in research laboratories.

[0002] Residual petroleum products are the heaviest fractions obtained after distilling light and middle distillates from crude oil. These high-molecular-weight, viscous, and complex mixtures are known as fuel oils, tars, and bitumens. These products are the basis for the production of boiler fuel, road and construction bitumens, and also serve as feedstock for further downstream processes such as deasphalting and hydrocracking.

[0003] The main components of residual petroleum products are asphaltenes, paraffins, oils, and resinous substances. The amount of asphaltenes influences the softening point and hardness of residual petroleum products. Resins play a key role in stabilizing asphaltenes. However, resins are chemically unstable, so prolonged exposure to oxygen or other oxidizing environments causes the resins to convert into asphaltenes. The resin-to-asphaltene ratio is one of the most important parameters determining the colloidal structure of residual petroleum products. Disruption of this balance, caused by technological processes or product aging, leads to irreversible changes in its rheological and performance properties.

[0004] Petroleum oils are a product of the processing of high-boiling petroleum fractions, consisting of a mixture of alkylnaphthenic and alkylaromatic hydrocarbons, among others. The presence of several hydrocarbon groups with diverse compositions leads to varying effects on the properties of petroleum products. The ratio of oils to asphaltenes has a significant impact on the softening point and brittleness temperature. Paraffins, particularly solid saturated hydrocarbons of normal structure, have a dual effect. On the one hand, they can improve lubricating properties in oils; on the other hand, at high concentrations and at low temperatures, they precipitate as crystals, sharply increasing the pour point and impairing the flowability of residual fuels and oils.Monitoring the paraffin component is necessary to ensure normal transportation, storage and use of residual petroleum products in different climatic zones, as well as to assess the need and effectiveness of dewaxing.

[0005] Thus, the properties of residual petroleum products are determined by the ratio of their constituent components: oils, resins, paraffins, and asphaltenes. An increase in the asphaltene and resin content leads to an increase in the hardness, softening point, and brittleness of the product. Conversely, oils that partially dissolve resins make it soft and easily fusible. A decrease in the molecular weight of oils and resins also increases its plasticity.

[0006] Comprehensive analysis of residual petroleum products for the content of asphaltenes, paraffins, oils and resins is not just a quality control procedure; it allows us to predict the behavior of raw materials during processing, calculate the yield and quality of target products, develop optimal compositions of commercial materials, prevent process risks and ensure product compliance with standards and technical requirements.

[0007] However, the methods widely used in the industry for determining the concentration of asphaltenes, resins, oils, and paraffins in petroleum products are labor-intensive and time-consuming. Furthermore, there is currently no generally accepted method for simultaneously determining the content of asphaltenes, resinous substances, oil fractions, and paraffinic hydrocarbons using a single sample. This results in significant costs associated with the increased use of, typically, expensive, solvents. Furthermore, the achieved accuracy of the results does not always meet the required standards. More advanced and technologically advanced methods are aimed at conducting large-scale analyses and require specialized hardware that requires maintenance by qualified specialists.

[0008] Therefore, it is necessary to create simple and inexpensive methods of determination that do not require complex equipment and ensure high accuracy and reliability of results.

[0009] A known method for determining the content of solid paraffin in bitumen is described in [GOST 33139-2014 "Public highways. Viscous petroleum road bitumens. Method for determining the content of solid paraffin" method A], which consists of preliminary dissolution of bitumen in toluene, precipitation of asphaltenes by adding a 40-fold amount of isooctane or heptane, filtration of the settled solution, while most of the solvent is distilled off from the resulting filtrate, the remaining concentrate is passed through an adsorption column with aluminum oxide, the solvent is distilled off from the eluate passed through the column, the precipitate is dissolved in an acetone-toluene mixture by heating to 50 ° C, cooled, kept for 1 hour at a temperature of -20 ° C and filtered through a porous glass filter cooled to the same temperature; plates, the precipitated paraffin is washed off the filter with heated toluene and after its distillation, the paraffin content is determined by weighing the resulting sediment in a desiccator.

[0010] The existing method traditionally involves multiple stages, is labor-intensive, and takes a considerable amount of time. Furthermore, it is characterized by increased consumption of expensive reagents, which negatively impacts cost-effectiveness and reduces the profitability of the process.

[0011] A known method for determining oils in crude oil and petroleum products [RU 2802284, published 08 / 24 / 2023], in which a sample (crude oil, petroleum product, ASPO) is dissolved in a 40-fold volume of petroleum ether and placed in a dark place for 16 hours. The settled solution is carefully filtered without stirring. The filtrate is concentrated to obtain 20-30 cm 3The mixture is transferred to an adsorption column filled with aluminum oxide, and the sorbent is washed several times with solvent. Petroleum ether is distilled from the resulting desorbed solution, the residue in the flask is dissolved in an acetone-toluene mixture, the resulting solution is cooled to -20°C, and filtered at -20°C through a porous filter. The oils remain in the acetone-toluene solution. This solution is evaporated, dried at 105°C to constant weight, and the weight of the isolated oils is determined.

[0012] The disadvantage of this method is the length of the process and the use of a sorbent that cannot be regenerated.

[0013] The closest technical solution to the claimed invention is a method for determining resinous substances in oil, petroleum products and asphaltene-resin-paraffin deposits [RU 2799314, published 04.07.2023; D.A. Struk et al. Rapid method for determining the resin content in oil and petroleum products and asphaltene-resin-paraffin deposits / / Bulletin of the Far Eastern Branch of the Russian Academy of Sciences. 2023. No. 6], in which a weighed sample is treated with isopropyl alcohol, the precipitate is filtered off, dried at room temperature and dissolved in a nefras-tolul mixture. The precipitate that has not dissolved at this stage is filtered off, which can be used to determine the content of asphaltenes and mechanical impurities. The filtrate is evaporated to a minimum volume, then sorption treatment is carried out in static mode, keeping it in contact with aluminum oxide, silica gel or silica from rice husk for 30-35 minutes, after which the liquid phase is drained.To determine paraffin, the liquid phase is evaporated to a minimum volume to remove as much solvent as possible. Adsorbed resinous substances are desorbed by threefold treatment with an alcohol-toluene mixture containing the components in a 1:1 volume ratio. The resulting solution is evaporated, the evaporated residue is dried at 105°C to constant weight, after which the relative resin content is calculated.

[0014] A disadvantage of this method is the initial treatment with isopropyl alcohol, which partially removes oils from the sample and, depending on the temperature, some paraffins. This prevents step-by-step separation and determination of the main components. This method, like others, lacks a comprehensive, consistent methodology for determining the content of asphaltenes, paraffins, oils, and resinous substances in petroleum products. Each method primarily describes the determination of a single component, only briefly mentioning that the sediments or filtrates obtained during the determination of a particular component can be analyzed for other substances.

[0015] The objective of the invention is to create a highly cost-effective method for determining the content of resinous substances, asphaltenes, paraffins and oils in residual petroleum products, which is simple to implement and does not require significant time and cost.

[0016] The technical result of the method consists in its simplification and improvement of technical and economic indicators while simultaneously increasing the accuracy and reliability of determining the content of asphaltenes, resinous substances, oil fractions and paraffin hydrocarbons, using one sample.

[0017] The method for determining the content of resinous substances, asphaltenes, paraffins and oils in residual petroleum products from one sample is carried out as follows.

[0018] A weighed initial sample weighing up to 1.5 g is homogenized and heated in a water bath, then dissolved in warm petroleum ether, brought to a boil, cooled to 20°C and settled for an hour to obtain a precipitate containing asphaltenes, the precipitate is filtered and washed with a solvent, then washed off the filter with hot benzene and dried to a constant weight at 105°C, the residue that does not dissolve on the filter can be used to determine the content of mechanical impurities in bitumen; the filtrate containing paraffins, oils and resins is evaporated on a rotary evaporator to 30-50 ml and added to a sorbent, which is silica gel that has undergone heat treatment at 105-110°C and impregnated with a mixture of petroleum ether: toluene solvents (1:1), sorption is carried out in static mode for 40 minutes, then the de-resined liquid phase is decanted through a filter, the sorbent is thoroughly washed 2-3 times with a mixture of petroleum ether: toluene to remove residual paraffin and oil,the eluate is evaporated on a rotary vacuum evaporator to a minimum, the residue is dissolved in a mixture of toluene: acetone = 65:35 heated to 40-50°C and transferred to a pre-weighed container, allowed to cool to room temperature and placed in a freezer at a temperature not exceeding minus 25°C for 1-2 hours until paraffin crystals appear, the paraffin that has precipitated as a result of crystallization in the cold is very quickly, within literally one or two minutes, without raising the temperature, filtered under vacuum on a filter previously kept in the freezer and washed with a cooled mixture of solvents, the filtrate with oils is evaporated on a rotary evaporator to a minimum and the oils are dried to a constant weight at 105°C, the paraffins are washed off the filter with hot toluene and dried in a drying oven at 105-110°C to a constant weight; desorption of resinous substances from silica gel is carried out by treating it 3-4 times with a mixture of solvents containing ethyl alcohol and toluene in a volume ratio of 2:1,the resulting solution is evaporated on a rotary vacuum evaporator and the evaporated residue is dried at a temperature of 110°C to a constant weight; calculation of the relative content of the component being determined C, м (in %) in the original sample is calculated according to formula 1:

[0019] C м = m1 / m2·100% (1)

[0020] where m1 is the weight of the dried residue, g; m2 is the weight of the original sample, g.

[0021] After desorption of resinous substances, the sorbent can be regenerated and reused. To do this, it is washed with toluene and an alcohol-toluene mixture until a colorless solvent is obtained, then filled with distilled water six times at 200 cm 3 water per 100-150 g of silica gel. After separating the water, the silica gel is dried at 50°C until the lumps disintegrate, and then the dried silica gel is kept in an air thermostat at 180 ±10°C for 6 hours.

[0022] It was found that, for complete sorption and accurate determination of resin content in bitumen, a comparative analysis using different sorbents was conducted using alumina, rice husk silica, and silica gel. When using alumina and rice husk silica, resin results were underestimated by 20-25%.

[0023] The improved technical and economic performance of the proposed method is based on its simplification and the simultaneous determination of four parameters from a single sample, including a reduced number of stages, and a reduction in the time and cost of implementation. The proposed method allows for the determination of asphaltenes, resins, oils, and paraffins from a single sample within two working days, a significant advantage. The reuse of solvents also enhances the method's economic benefits.

[0024] Examples of specific implementation of the method.

[0025] In all examples of the specific implementation of the method, a rotary vacuum evaporator RotavaporRII (BuchiLabortechnik, Germany) was used to remove solvents, with the help of which the solvent distillation is carried out quickly and economically, without losses with the possibility of reuse.

[0026] Example 1.

[0027] A 1.06 g sample of bitumen was dissolved in 30 ml of petroleum ether in a conical flask, heated on a hotplate for 5-10 minutes until the sample was completely dissolved, then cooled to 20°C and allowed to settle for an hour until the asphaltenes completely precipitated. The resulting precipitate was filtered through a blue ribbon filter and washed with petroleum ether until the filtrate was clear. The remaining precipitate was washed from the filter with hot benzene into a tared beaker and dried to constant weight at 105°C. The precipitate weighed 0.0914 g, or 8.62%.

[0028] The filtrate was evaporated on a rotary evaporator to 30-50 ml. The evaporated residue was added to a sorbent consisting of silica gel heat-treated at 105-110°C and impregnated with a petroleum ether:toluene (1:1) solvent mixture. Adsorption was carried out in static mode for 40 minutes, then the de-resined liquid phase was decanted through cotton wool. After this, the sorbent was thoroughly washed 2-3 times with a petroleum ether:toluene mixture to remove residual paraffin and oil, with a volume of approximately 300 ml. The eluate was evaporated to dryness, the residue was dissolved in a toluene:acetone mixture (65:35) heated to 40-50°C and transferred to a pre-weighed 100 ml Conical flask. Cooled to room temperature and placed in a freezer at a temperature no higher than minus 25°C for 2 hours until paraffin crystals appeared.A set of equipment necessary for the precipitation of solid paraffin by cooling was placed in the freezer: a filter, a flask, a funnel, and a solvent mixture of toluene:acetone (65:35).

[0029] The paraffin precipitated as a result of cold crystallization was quickly, without raising the temperature, filtered under vacuum on a sintered glass filter and washed with a cooled solvent mixture. The filtrate containing the oils was evaporated to a minimum on a rotary evaporator, transferred to a tared flask with a toluene:acetone solvent mixture, and dried to constant weight at 105°C. The precipitate weighed 0.7502 g, or 70.77%.

[0030] The filtered paraffins were washed with hot toluene into the same tared conical flask used for precipitation, and the paraffins were dried in a drying oven at 105-110°C until constant weight. The precipitate weighed 0.70281 g, or 2.65%.

[0031] The resinous substances were desorbed from silica gel using a solvent mixture containing ethyl alcohol and toluene in a 2:1 volume ratio. The resulting solution was evaporated on a rotary vacuum evaporator, and the evaporated residue was dried at 110°C to constant weight. The precipitate weighed 0.1200 g, or 11.32%.

[0032] Similar to Example 1, asphaltenes, paraffins, oils, and resinous substances were analyzed from the same sample in other residual petroleum product samples (tar, M-100 fuel oil). Table 1 presents the results of the analysis of the main components using the proposed gravimetric method, with calculations of the reproducibility of the results and an assessment of the analytical control standard.

[0033] The reliability of the results of the proposed method is demonstrated using examples of its specific implementation; the reproducibility of the results complies with regulatory control. The results obtained for several repetitions are within the confidence interval.

[0034] The value of the relative error Δ, % for the proposed method, calculated using formula 2:

[0035] Δ, % = 0.84*1.96*R / 2.77 (2)

[0036] Table 1. Results of the analysis of the determination of the main components in residual petroleum products using the gravimetric method, with the calculation of the reproducibility of the results and the assessment of the control standard for the analysis.

[0037] Indicators Bitumen Normative control │X1-X2│ ≤ R Δ, % X1 X2 X cf. │X1-X2│ R Ash (775̊C±25̊C), % 0,04 Paraffin, % 2,65 2,86 2,76 0,21 1,6 Satisfied. 0,95 Asphaltenes, % 8,62 8,16 8,4 0,46 1,1 Satisfied. 0,65 Resins, % 11,32 12,45 11,9 1,13 1,13 Satisfied. 0,67 For example, % 70,77 65,51 68,1 5,26 6,81 Satisfied. 4,05 Overall, % 93,34 88,98 91,16 Tar Normative control │X1-X2│ ≤ R Δ, % X1 X2 X cf. │X1-X2│ R Ash (775̊C±25̊C), % 0,05 Paraffin, % 4,98 5,70 5,34 0,72 0,75 Satisfied. 0,45 Asphaltenes, % 12,00 11,20 11,60 0,80 1,51 Satisfied. 0,90 Resins, % 8,62 8,05 8,34 0,57 0,82 Satisfied. 0,49 For example, % 62,90 68,90 65,90 6,0 6,59 Satisfied. 3,92 Overall, % 85,80 95,00 90,40 Fuel oil M-100 Normative control │X1-X2│ ≤ R Δ, % X1 X2 X cf. │X1-X2│ R Ash (775̊C±25̊C), % 0,44 Paraffin, % 0,94 1,03 0,99 0,07 0,15 Satisfied. 0,02 Asphaltenes, % 2,02 2,40 2,21 0,38 0,22 Satisfied. 0,13 Resins, % 5,72 5,58 5,65 0,14 0,57 Satisfied. 0,34 For example, % 75,87 73,88 74,88 1,99 7,49 Satisfied. 4,45 Overall, % 84,55 82,99 83,77

Claims

1. A method for determining asphaltenes, paraffins, oils and resinous substances in residual petroleum products, according to which a weighed initial sample is treated with solvents to obtain a precipitate containing asphaltenes, the resulting precipitate is filtered and washed with a solvent, the filtrate is subjected to sorption treatment with the separation of a liquid phase containing paraffins and oils, the adsorbed resinous substances are desorbed using a solvent, dried to a constant weight, characterized in that the initial sample is homogenized and heated in a water bath, then dissolved in warm petroleum ether, brought to a boil, cooled to 20 °C and settled for an hour to obtain a precipitate containing asphaltenes, the precipitate is filtered and washed with a solvent, then washed from the filter with hot benzene and dried to a constant weight at 105 °C; the filtrate containing paraffins, oils and resins is evaporated on a rotary evaporator to 30-50 ml and added to the sorbent,which is silica gel that has undergone heat treatment at 105-110 ° C and impregnated with a solvent mixture of petroleum ether: toluene 1: 1, sorption is carried out in a static mode for 40 minutes, then the de-resined liquid phase is decanted through a filter, the sorbent is thoroughly washed 2-3 times with a mixture of petroleum ether: toluene to remove residual paraffin and oil, the eluate is evaporated to a minimum, the residue is dissolved in a mixture of toluene: acetone 65: 35 heated to 40-50 ° C and transferred to a pre-weighed container, allowed to cool to room temperature and placed in a freezer at a temperature not exceeding minus 25 ° C for 1-2 hours until paraffin crystals appear, the paraffin that has precipitated as a result of crystallization in the cold is very quickly, within literally one or two minutes, without increasing the temperature, filtered under vacuum on a pre-aged in a freezer filter and rinsed with a cooled solvent mixture,the filtrate with oils is evaporated on a rotary evaporator to a minimum and the oils are dried to a constant weight at 105°C, the paraffins are washed off the filter with hot toluene and dried in a drying oven at 105-110°C to a constant weight; desorption of resinous substances from silica gel is carried out by its 3-4-fold treatment with a mixture of solvents containing ethyl alcohol and toluene in a volume ratio of 2:1, the resulting solution is evaporated on a rotary vacuum evaporator and the evaporated residue is dried at a temperature of 110°C to a constant weight; calculation of the relative content of the determined component C, м , %, in the original sample is determined according to the formula: WITH м = m1 / m2⋅100% where m1 is the weight of the dried residue, g; m2 is the weight of the original sample, g.

2. The method according to paragraph 1, characterized in that the sediment remaining on the filter after dissolving the asphaltenes with hot benzene can be used to determine the content of mechanical impurities in bitumen.

3. The method according to paragraph 1, characterized in that the sorbent after desorption of resinous substances can be regenerated and reused, for this it is washed with toluene and an alcohol-toluene mixture until a colorless solvent is obtained, then filled with distilled water six times at 200 cm 3 water per 100-150 g of silica gel, after separating the water, the silica gel is dried at 50°C until the lumps disintegrate, and then kept in an air thermostat at a temperature of 180±10°C for 6 hours.