Synthetic fatty acid from crude oil of Tamsagbulag petroleum deposit (Mongolia)

In this work, we studied to obtain synthetic fatty acids raw materials to produce surfactants and various detergents from paraffin. The solid paraffin extracted from the Tamsagbulag petroleum deposit was 46 mass%, distilled 350-450°C, by complexing with urea. Experimental study indicates paraffin's physicochemical characteristics from this petroleum are more suitable to use in the production of synthetic fatty acids. By solid paraffin oxidation, we obtained 33.01% of the synthetic fatty acids containing monocarboxylic acids.We suggest obtaining the synthetic fatty acid by oxidation process in normal condition from petroleum paraffin.


INTRODUCTION
Crude oil, one of the most complex chemical mixtures in the world, serves as a feedstock 27 for the petrochemical industry and as raw material for many chemical products such as fuels, solvents, lubricant oils, plastics, fertilizers, detergents, and others [1,2].
There are some deposits of crude oil in our country. Out of them, 3 large deposits are being 30 exploited. The Tamsagbulag deposit is located in the Matad area of Dornod province, Mongolia. Other deposits such as Zuunbayan and Tsagan-Els are situated in the Zuunbayan area Dornogovi province, with 332.67 million tons of proven oil reserves and 33 43.25 million tons of proven reserves [3][4][5].
Previously, we studied the physicochemical properties of petroleum and the detail of the complete hydrocarbon composition of crude oils from the Tsagaan-Els, Zuunbayan, and 36 Tamsagbulag deposits. Based on the previous report, the crude oil of Mongolia was determined as heavy oil with high viscosity and has a lower yield of light fraction, and it belongs to the high-paraffinic category of crude oil [3,6,7]. One of a kind products obtained 39 from the high paraffin crude oil is a synthetic fatty acid. Synthetic fatty acids are critical raw materials for soaps, detergents, fragrances, emulsifiers, organic lubricating oils, and surfactants, which can be obtained by oxidation of paraffin-rich crude oil. During the 42 oxidation process, 70% of the high molecular monocarboxylic acids can be produced by the oxidation of solid paraffin to manufacture aliphatic alcohols and surfactants, and the remaining 30 % consume for lubricants (15%) and in other industries [1,8,9]. 45 For over some years, various researchers have studied the air oxidation of paraffinic hydrocarbons to produce synthetic fatty acids [1,8]. In the previous research, based on the high-paraffin crude oil in the field of Tsagaan-Els, solid paraffin was extracted from the 48 oil fraction and further oxidized by molecular oxygen the in the presence of a catalyst to produce synthetic fatty acids [10]. Tsagaan-Els crude oil deposit has a lower reserve than the Tamsagbulag oil deposit. Moreover, it contains low asphaltene, low oil, and high water 51 content than the Tamsagbulag oil deposit [10]. Since the Tamsagbulag and Tsagaan-Els deposit crude oil show different physical and chemical characteristics, it's evident that the technological scheme for obtaining synthetic fatty acid is expected to be different.

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At the same time, the development of petrochemical synthesis technology from various petroleum sources in Mongolia is an important study. It has practical significance in creating opportunities for domestic goods production.

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In this work, we aimed at the possibility of isolating synthetic fatty acid from solid paraffin from the Tamsagbulag crude oil deposit and studied its properties. As a research sample of crude oil from the depth of 2300-2600 m in the XXI   block of Eastern of Tamsagbulag field Mongolia, which had brought at September 2018 year, was used. The petroleum exploration blocks in Mongolia and sample collected area 63 are shown in Fig. 1.  [2,11,12]. SARA method is used for group composition (oil, resin, and asphaltenes) of crude oil [2,13,14]. Experimental to isolate synthetic fatty acids from petroleum were carried out according to the following scheme. The FT-IR spectra of oxide products were obtained on a Nicolet 20-PC FT-IR spectrometer with CsI optics and a DTGS detector. The KBr disc contained a 0.5% finely ground shell 84 sample. All the spectra were measured with a frequency range of 4000 to 400 cm -1 and 32 scans for each sample [17,18].

RESULTS AND DISCUSSION
The physical and chemical characteristics, group composition, and content of fraction of 93 the petroleum of Tamsagbulag deposit of Mongolia have been studied. The physical and chemical characteristics of the oil are given in Table 1.  Table 2 shows that the physicochemical characteristics of paraffin wax obtained from the oil fraction of this oil are classified as C-type paraffin, which can be used to produce synthetic fatty acids [27,29].   the oxidation of paraffin is carried out at temperatures above 120°C, it forms large quantities of low molecular weight fatty acids -oxyacids, dicarboxylic acids, and other related products like a mixture various oxygen compounds [32,33].

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Under suitable conditions for synthetic fatty acids, the product yield formed high, and the by-product is less developed. Therefore, it is necessary to select the appropriate conditions and carry out the reaction.
As the result of oxidation of paraffin of Tamsagbulag's oil is tested several times in the 165 temperatures range of about 105 to 130°C with a 0.6 l/min oxygen flow in the oxidizing reactor, as the following conditions are selected as the best. It is considered that the amount of catalyst will be 0.3 mas. % [1,10,34].

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In the early stages of the oxidation of paraffin, we carried out the reaction at relatively high temperatures (120-130°C) for 2 h to form free radicals and stimulate the faster reaction.
During the process, the catalyst dissolves in paraffin and stimulates an oxidation reaction.

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In the second stage of the reaction, the temperature was gradually down to 105-110°C, and 0.6 l/min flow rate of molecular oxygen was entered, and then an oxidation reaction takes place. During this process, the paraffin-free radicals are oxidized by oxygen, the by-174 product is minor at relatively low temperatures, and the reaction takes place in the direction of the formation of fatty acids [33,34].
As a result of the oxidation of n-paraffin, a mixture of acidic and neutral oxygenated 177 compounds is formed. The amount of these compositions is controlled by the value of acid.
Generally, the value of acid varies from 70 to 76 mg KOH/g when synthetic fatty acid is oxidized [1,31].

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It shows that the number of oxidizing acids was 74 mg KOH/g when the solid paraffin of petroleum of Tamsagbulag is oxidized under these conditions for 30 h, and paraffin's hydrocarbons are oxidized to form fatty acids.

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The dependence between the oxidation period of paraffin and the number of acids is shown in Fig. 5. Oxidation is high as the number of acids increases, and it is linearly related to the oxidation period. The structure of the hydrocarbons in the composition of paraffin and oxidized products of Tamsagbulag's oil was determined by IR spectroscopy and are shown in Fig. 6.  pressure. Generally, after synthetic fatty acid is formed, the raw material of fatty acids (С10-С20) is used to manufacture soap [1].
The ester value is between 5-10 mg KOH/g, and the saponification value is 245-260 mg 207 KOH/g, and the acid value is 245-260 mg KOH/g [1,31]. The parameters of the extracted fatty acids were determined and shown in Table 3.
210 Ester value, mg KOH/g 6.2 From the Table 4, according to the parameters of synthetic fatty acids obtained by oxidizing 213 petroleum paraffin from the Tamsagbulag deposit, the acids value is 254 mg KOH/g, the esters value is 6.2 mg KOH/g, and the saponification value is 260.0 mg KOH/g. It indicates that fatty acids are formed as a result of the oxidation process.

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The chemical composition of the fatty acid obtained by paraffin oxidation was determined by gas chromatography, and the results are shown in Fig. 7 and Table 4.   Table 4. Chemical composition of fatty acid from paraffin of Tamsagbulag oils 222 As shown in Table 4, the composition of synthetic fatty acids obtained by the oxidation of petroleum paraffin contains synthetic fatty acids with carbon atoms С7-С20 with a variation 225 of content 0.2-3.5%.
In a mixture of synthetic fatty acids extracted from petroleum paraffin at the Tamsagbulag deposit, the monocarboxylic acids are 33.01 and 49.45% of non-oxidized paraffin 228 hydrocarbons, and the content of other oxygen compounds is 17.54%.
As a result of this study, it has been determined that the oxidation of petroleum paraffin at an oxygen flow rate of 0в6 l/min at a variable temperature of 130-105°C, with the presence 231 of 0.3% catalyst (KMnO4), is the optimal condition of reaction.
Although it has been considered that the paraffin's hydrogen carbons are inactive and require a unique condition for the chemical synthesis, the present research indicated that The total content of fatty acids (C6-C20) 33.01 Content of non-oxidized paraffin (C9-C23) 49.45 Other compounds 17.54 the paraffin from the Tamsagbulag oil can be processed to form synthetic fatty acid without using special requirements.

CONCLUSIONS
It has been determined that 46% paraffin can be obtained by forming a complex of urea, solid paraffin extracted from the oil fraction of Tamsagbulag oil distilled at 350-450°C, and 240 it belongs to the technical category C type used in the production of synthetic fatty acids.
Our study has indicated that the superior fatty acid, which is a raw material for surfactants, can be obtained by oxidizing petroleum paraffin hydrocarbons with oxygen under normal 243 conditions of the oxygen flow rate of 0,6 l/min at a variable temperature of 130-105°C, with the presence of 0.3% catalyst (KMnO4). The obtained fatty acid's total content of fatty acids (C7-C20) is 33.01%, and the content of non-oxidized paraffin C7-C20 is 49.45%.