Monday, February 26, 2024
Monday, February 26, 2024
HomeScienceSynthesis and biodegradation tests of some ester-based synthetic oils - Scientific Reports

Synthesis and biodegradation tests of some ester-based synthetic oils – Scientific Reports

There is an urgent need to develop pollution-free and environmentally friendly lubricants as an alternative to mineral-based lubricants.17. Rapeseed, soybean and palm oils are among examples of base oils. They have good tribological properties. Despite their obvious benefits, they have limited corrosion resistance and are at risk of hydrolytic and oxidative instability.18. glycol esters They are an effective substitute for mineral and vegetable oils. This research focuses on the synthesis of diestersthe biodegradability rate of the preparation estersand their suitability for use as synthetic lubricants.

Preparation of diesters.

diesters were produced by reacting individually valeric acid With several glycols (ethylene glycol, propylene glycol, butylene glycol or polyethylene glycol 400). So, ethylene glycol reacts with minor (propanoic acid) and higher (heptanoic or octanoic acid) acids separately. The general esterification reaction is shown in Fig. 1.

Figure 1

The esterification reaction of valeric acid and ethylene glycol.

Confirmation of the structure of the prepared esters.


FTIR spectroscopy was used to ensure completion of the esterification reactions. The ghosts of all esters They are almost the same with slight differences as seen in Figs. 2a–d. Generally, FTIR spectra show the following: the disappearance of strong –OH peaks at 3500 cm-−1 ±10cm−1 and acid C=O group band at 1730 cm−1 at the end of esterification and its replacement by ester C=O group bands at 1735 cm−1and 1265cm−1±10cm−1, respectively. This shows that the esterification procedure was carried out successfully.eleven.

Figure 2
Figure 2

GO spectrum of compound A (to), compound B (b), compound C (c), compound F (d).

1H-NMR spectroscopy

1H-MRI Spectroscopy was used to investigate the composition of the AF products. Figures 3a to f demonstrate diesters chemical shift as follows: 1H-CH3triplet at 0.96 ppm (to), 1H-CH2multiplet at 1.33 ppm (b), 1HC-C(O)OR estersmultiplet at 1.68 ppm (c), 1HC(O)-OC, triplet at 2.25 ppm (d), 1 HOC(O)R, triplet at 4.36 ppm (my), as well as the loss of RCOOH carboxylic acidwhich approve the complete esterification of acids.

figure 3
figure 3

He 1H-MRI spectrum of compound A (to), compound B (b), compound C (c), compound D (d), compound E (my), compound F (F).

Thermal stability of prepared esters.

He diestersThe thermal properties (A – G) were also investigated. For example, in Figures 4a to f, complete degradation occurs between 150 and 300 °C, demonstrating reasonable thermal stability of the preparation. esters. Therefore, its use corresponds to the temperature restrictions indicated in the thermograms.

Figure 4
Figure 4

TGA of prepared ester A (to), ester B (b), ester C (c), ester D (d), ester E (my), ester F (F).

Physicochemical properties of the prepared esters.

Rheological behavior of the preparation. esters

The synthesized compounds have Newtonian rheological properties, as illustrated in Fig. 5a, b. This means that Newtonian fluids continue Newton law of viscosity. Viscosity is not affected by cut rate. In lubrication, Newtonian fluids, such as motor oil, are used for lubrication purposes in engines and machinery to reduce friction, dissipate heat and protect against wear. Newtonian lubricant is preferable to improve tribological performance. Newtonian fluid can significantly increase the load capacity of the bearing.19 .

Figure 5
Figure 5

Rheological behavior of synthetic oil D (to), synthetic oil G (b).

Biological degradability of the prepared esters.

Cultural media (MSM) detected seventeen bacterial isolates (B1-B17) in a sample of water contaminated with oil. In MSM media, bacterial isolates B1 and B2 are considered predominant.fifteen determined that two species of biodegrading bacteria have the best growth rate in MSM half.

Molecular identification of selected oil-degrading bacteria.

Under the light microscope, the bacterial isolate (B1) is a rod-shaped, Gram-negative organism. 16S rRNA identifies the bacterial isolate (B2) as Enterobacter hormaechei subsp. Xiangfangensis strain 10-17 having 99.17% similarity. The MEGA program is being used. A sequence of Enterobacter hormaechei subsp. identified in this research coincided with other Enterobacter species. Figure 6a shows the phylogenetic tree constructed from Enterobacter hormaechei and closely related bacterial strains using 16S. rRNA Gene neighbor joining method.

Figure 6
figure 6

(to) A phylogenetic tree of Enterobacter hormaechei subsp. Evolutionary relationships of the Xiangfangensis 10–17 16S strain with other strains, extracted from the NCBI database and the phylogenetic tree made by the Mega X program. (b) A phylogenetic tree of Pseudomonas aeruginosa Evolutionary relationships of ATCC 10145 with other strains, taken from the NCBI database and the phylogenetic tree made by the Mega X program.

Under a light microscope, the bacterial isolate (B2) appears as a rod-shaped, Gram-negative organism. Pseudomonas aeruginosa ATCC 10145 It is recognized as the bacterial isolate (B2) by 16S rRNA with a similarity of 99.53%. using the MEGA program. Pseudomonas aeruginosa sequences from the isolate of this study were compared to Pseudomonas species by BLAST analysis. Figure 6b shows how the phylogenetic tree of Pseudomonas aeruginosa and closely related bacterial strains were reconstructed using the 16S neighbor-joining method. rRNA gene.

Biodegradation of different lubricating oil samples using degrading bacterial strains.

In the current study, the ability of two different bacterial isolates (B1-B2) to biodegrade the lubricating oil sample was evaluated. The pure bacterial isolates were inoculated in MSM Media with different lubricating oils used separately as sole carbon source for 3 days. The oil samples were accurately weighed by gravimetric analysis. The percentage of the oil that had biodegraded was estimated and gravimetric analysis (GC) It was used to find the change in chemical composition.

gravimetric analysis of the different degraded lubricating oils

According to the results of gravimetric analysis In Table 3, different bacterial isolates (B1-B2) degraded lubricating oil in the range of 34 to 84% after incubation for three days. Compared with other types of lubricating oil, the microcosms containing the individual bacterial isolates (B1 and B2) with A and D gave a higher percentage of degradation. Verma et al.twentystated that, after 5 days, Pseudomonas sp. The oily sludge degradation capacity of SV 17 represents around 60% of the saturated and aromatic components. El-Sheshtawy et al.sixteenshowed that after 7 days, the bacterial strains had broken down between 30 and 50% of the crude oil.

Table 3 Residual lubricating oil after biodegradation by two different bacterial isolates.
Gas chromatographic analysis

The first step in the mechanism alkane The degradation of lubricating oil by bacteria under aerobic conditions is the oxidation of alkanes by the class of oxygenase enzymes (enzymes that catalyze the incorporation of oxygen into the substrate), namely alkane hydroxylase enzymes that catalyze the addition of hydroxyl groups attacking the O atom by oxidation during the alkane hydroxylation reaction. alkanes they oxidize to alcohol and later become fatty acidyestwenty-one. The next path of fatty acid Metabolism can occur through cellular lipid, β-oxidation, and α-oxidation pathways. Through the β-oxidation pathway fatty acids it will become in acetyl CO-A and enters the TCA cycle, converted to CO2 and energy. If through fatty acid α-oxidation pathway will be converted directly to CO2 and fatty derivatives22.

In this study, the biodegradation of various lubricating oils was examined in the current study using the GC for aliphatic compounds after three days of incubation period. After biodegradation by two different bacterial strains, the residue n-paraffin and isoparaffin The percentages contained in various lubricating oils were calculated and contrasted with the control sample in Tables 4, 5.

Table 4 Percentages of residual north- and isoparaffins samples after bacterial degradation by bacterial strain (B1) using GC Chromatography.
Table 5 Percentages of residual north- and isoparaffins samples after bacterial degradation by bacterial strain (B2) using GC Chromatography.

The results showed that isoparaffins degrade faster than n-paraffins, which are considered more resistant to the biodegradation process in most different microcosms separately. In the study of the literature, hydrocarbons vary in their sensitivity to microbial attack, and were previously classified in the following order of decreasing sensitivity: n-alkanes ˃ branched alkanes ˃ aromatics with low molecular weight cycloalkanes6. On the other hand, additional consumption of high molecular weight substances can be blamed for an increase in the percentage of any compound, causing a proportional accumulation of that hydrocarbon component in the low molecular weight chemicals. The above data indicate that types (A and D) of lubricating oil were more consistently degraded by two separate bacterial strains than other types of lubricating oil.

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