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Article

Surface-Functionalized Nano-Montmorillonite and Its Application as Crude Oil Flow Improver

by
Kechen Liu
1,2,
Michal Slaný
3,4,*,
Alena Golian-Struhárová
5,
Hailong Wang
6,
Liyuan Zhang
6,
Jiyou Fu
7,
Gang Chen
1,2 and
Yingna Du
1,2,*
1
Engineering Research Center of Oil and Gas Field Chemistry, Universities of Shaanxi Provence, Xi’an Shiyou University, Xi’an 710065, China
2
Shaanxi Province Key Laboratory of Environmental Pollution Control and Reservoir Protection Technology of Oilfields, Xi’an Shiyou University, Xi’an 710065, China
3
Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, 845 36 Bratislava, Slovakia
4
Department of Materials Engineering and Chemistry, Faculty of Civil Engineering, Czech Technical University in Prague, Thákurova 7, 166 29 Prague, Czech Republic
5
Department of Materials Engineering and Physics, Faculty of Civil Engineering, Slovak University of Technology, Radlinského 11, 810 05 Bratislava, Slovakia
6
No.11 Oil Production Plant, PetroChina Changqing Oilfield Company, Xi’an 710060, China
7
Changqing Oilfield Shale Oil Development Branch, PetroChina Changqing Oilfield Company, Xi’an 710060, China
*
Authors to whom correspondence should be addressed.
Minerals 2024, 14(7), 696; https://doi.org/10.3390/min14070696
Submission received: 28 May 2024 / Revised: 1 July 2024 / Accepted: 4 July 2024 / Published: 8 July 2024
(This article belongs to the Special Issue Applications of Clay-Based Materials)
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Abstract

:
In view of the problem of poor flowability in the production and transportation of high-wax crude oil and high-viscosity crude oil, crude oil flow improvers are commonly used to reduce their viscosity and pour point. Although polymer-based crude oil flow improvers are highly effective in improving crude oil flowability, there are still problems such as high cost and the need for a large amount of solvent dilution when used. In this work, highly dispersed organic modified nano-montmorillonite was prepared by using Na-based montmorillonite and quaternary ammonium salts, and the influencing factors on the viscosity of the crude oil were investigated. The most effective modified nano-montmorillonite (B@MMT) can reduce the viscosity by 96.7% (21 °C) and depress the pour point by 15 °C. Furthermore, it has shown a high improvement in flowability in the other four different sources of crude oil, with viscosity reduction rates of 52.2, 93.4, 79.1 and 67.4%, respectively. B@MMT was characterized by FTIR, SEM, zeta potential and contact angle. Based on DSC and wax crystal structure analysis, the mechanism of the influence of B@MMT on crude oil viscosity and pour point was explored. Finally, the cost of B@MMT was estimated, and the result shows that, compared with the crude oil flow improver in use, B@MMT has considerable commercial competitive advantages.

1. Introduction

At present, with the increase in traditional light oil consumption and the gradual reduction in traditional petroleum resources, oil and gas resources have entered both the conventional and unconventional development stage [1,2,3,4,5]. Among them, heavy oil is one of the unconventional oil resources, accounting for about 40% of the world’s oil reserves [6,7,8,9,10]. The main characteristics of heavy oil are low flowability caused by high viscosity and high pour point [11,12,13,14,15], which makes it more challenging in production and transportation than light oil [16,17,18,19]. During the production stage, due to the deposition of wax in heavy oil, small pore throats are blocked [20,21], which can reduce the porosity and average pore size of the reservoir and reduce the recovery efficiency of heavy oil [22,23,24,25]. Moreover, due to the poor fluidity of heavy oil, pipeline transport at lower temperatures especially needs more energy or electricity [26,27,28].
Therefore, it is an important issue in crude oil production to reduce the viscosity and pour point of heavy oil through rational methods to improve the recovery rate of heavy oil resources and reduce the difficulty of transportation. The addition of crude oil flow improvers to reduce the viscosity and pour point of heavy oils is a commonly used and effective method. At present, the classification of crude oil flow improvers, namely polymers, nanocomposites, surfactants and organic solvents, their research and use are still in development. By grafting EVA onto n-alkyl acrylates with various alkyl chain lengths, Chen et al. [29,30,31] prepared polymethacrylate (PMA) by the transesterification of polymethyl methacrylate (PMMA) with base-catalyzed aliphatic alcohols. The synthesized PMAs have the characteristics of long hydrocarbon chains and hydrophilic parts (ester groups) derived from fatty alcohols. Therefore, PMAs may change the properties of crude oil precipitated crystals and destroy the cohesion between crystals, thereby effectively reducing the risk of forming a three-dimensional network. Finally, the pour point was depressed by 7.1 °C, and PMA-1 can reduce the viscosity of crude oil by 64.5% (50 °C). Based on the principle that the co-crystallization of alkylbenzene sulfonates and saturated hydrocarbons in crude oil can cause the wax crystal to be disordered, Zhou et al. [32,33,34,35] synthesized a variety of alkylbenzenesulfonates for viscosity reducers. It was found that the synthesized alkylbenzene sulfonates were effective, and the viscosity reduction rates of the two viscosity reducers were above 90%. Wang et al. [36,37] used medical waste polypropylene-based mask-derived materials as viscosity reducers and pour point depressants. The results showed that the intermediate layer (PP-2) of the mask had the highest efficiency. At 500 ppm, the viscosity reduction rate can reach 81%, and the pour point is reduced by 4 °C. Mao et al. [38] explored effective and low-cost nanoparticles to reduce and transport high-viscosity and high-pour-point heavy oil. The synthesized nanoparticles can reduce the viscosity of different heavy oils by more than 60% and depress the pour point by more than 10 °C. Zhao [39] et al. synthesized two oil-soluble viscosity reducers, namely MMT-CTAB and MMT-OTAC, using cetyltrimethylammonium bromide (CTAB) and octadecyltrimethylammonium chloride (OTAC) as montmorillonite modifiers. It was found that the modifier depresses the pour point of the model oil by 6 °C with a viscosity reduction of 91.1%. However, there is limited research on the application of nano-modified montmorillonite in enhancing crude oil fluidity, and the interaction mechanism between nano-modified montmorillonite and various components in crude oil remains unclear. In this study, a cost-effective method was employed to prepare surface-functionalized nano-montmorillonite. The resulting surface-functionalized nano-montmorillonite exhibits a universal viscosity reduction and condensate mitigation effect on crude oil from diverse sources.
On the basis of summarizing the research progress in this field, montmorillonite was selected as the basic raw material for the preparation of organically modified nano-montmorillonite, because nano-montmorillonite materials can be produced on a large scale at present. Moreover, its nanometer thickness and negatively charged silicate sheet layer on the surface make it easy to modify with lower cost. But ultrafine montmorillonite suffers from the problems of less uniform dispersion and easy agglomeration, so nanoscale montmorillonite with a high degree of dispersion was prepared by organic modification of the surface. Nanoscale montmorillonite particles have a larger specific surface area and increased effective content in crude oil, resulting in better viscosity and pour point reduction. The properties of the nano-organic modified montmorillonite were characterized and evaluated by Fourier transformation infrared spectroscopy (FTIR), contact angle analysis, scanning electronic microscopy (SEM), zeta potential analysis and dispersion stability experiments. The possible mechanism of interaction of the nano-organic modified montmorillonite and crude oil was studied by differential scanning calorimetry (DSC) analysis and wax crystal morphology.

2. Experimental

2.1. Material

The oil samples were acquired from Jidong Oilfield (J76), Changqing Pipeline Crude Oil (CQ1), Yanglou (YL), Xinjiang Haqian Oilfield (HQ) and Muxiu (GMX). The properties of the crude oil are shown in Table 1.
The sodium-based montmorillonite was separated from the bentonite deposit Jelšový potok (Slovakia) and was used in application as crude oil flow improver. The bentonite was suspended in distilled water, Na-saturated by repeated treatment with 1 M NaCl and the <2 μm fraction was collected. The excess of the Cl− ions was removed by washing with distilled water. The sample (Na-Mt) was dried at 60 °C and ground to pass through a 0.2 mm sieve. The cation exchange capacity (CEC) of Na-Mt was of 96 meq/100 g (0.96 mmol/g).
The reagents used in this experiment were purchased from Tianjin Damao Chemical Reagent Factory (Tianjin, China). Specifically, quaternary ammonium salts with different alkyl, dodecyltrimethylammonium chloride (C12, DTAC), tetradecyltrimethylammonium chloride (C14, TTAC), cetyltrimethylammonium chloride (C16, TAC), octadecyltrimethylammonium chloride (C18, OTAC) and docosyltrimethylammonium chloride (C22, BTAC) were prepared by synthesis.

2.2. Material Preparation

Under ambient conditions, an amount of surfactant was added to n-octanol and sonicated for 1 h until all dissolved. The surfactant was dissolved and an amount of Na-montmorillonite was added and sonicated for 2 h. The above suspension was centrifuged and washed three times using n-octanol, and then n-octanol was added to prepare a modified montmorillonite suspension at a concentration of 0.8%. A quantity of the suspension was taken and added to the crude oil for subsequent studies.
A specific volume of oil sample was taken and placed in a sealed water bath at 70 °C for 30 min to maintain a constant temperature environment. The modified material was added to n-octanol, followed by one hour of ultrasonic treatment to ensure uniform dispersion. Subsequently, the prepared suspension of modified material was added to the pre-treated crude oil and stirred in a closed water bath at 70 °C with constant temperature. Once the desired effect was achieved, the mixture was transferred to another water bath set at a specified temperature for viscosity measurement.

2.3. Differential Scanning Calorimetry (DSC) Analysis

The wax precipitation point and wax precipitation temperature peak test analysis method refer to the standard SY/T 0545-2012.

2.4. Wax Crystal Morphology Analysis

The saturated hydrocarbons were separated from crude oil by SY/T 5119-2016 method, and the wax crystals were studied morphologically with a BX41-OLYMPUS polarized light microscope (Microscope Central, Feasterville-Trevose, PA, USA).

2.5. Zeta-Potential Particle Size Analysis

Particle size and zeta potential analyzer (NanoBrook Omni, Brookhaven, MS, USA) were used for particle size analysis according to the reported methods [40]. The experimental analysis method was in accordance with GB/T 32668-2016.

2.6. Scanning Electron Microscope (SEM) Analysis

Scanning electron microscope (SEM) Vega 3, Tescan, Czech Republic equipped with SE and BSE detectors was used for observing the samples’ morphology at a voltage of 30 kV. The samples were coated with gold [41]. The test method was implemented according to JY/T 0584-2020.

2.7. FTIR Analysis

Fourier transform infrared spectroscopy was used according to GB/T 6040-2019. The infrared spectra were collected using the Nicolet 6700 Fourier Transform Infrared (FT-IR) spectrometer from Thermo Scientific™ (Waltham, MA, USA). The method according to the reference was used for sample preparation [42].

2.8. Decentralized Experiments

The same mass of montmorillonite with different particle sizes were taken in special sample bottles and distilled water and n-octanol were added. The samples were treated by using ultrasonic treatment for 3 h, and after the end of the treatment, they were left at room temperature to observe the phenomena.

2.9. Contact Angle Measurement

The contact angle measurement method was according to GB/T 30447-2013. The conical curve method or tangent method [43,44] was used to fit the ellipse of the droplet shape and establish a baseline.

3. Results and Discussion

3.1. Effect of Montmorillonite Dosage

The effect of montmorillonite dosage on the viscosity and pour point of J76 crude oil was evaluated first, and the results are summarized in Figure 1. Montmorillonite with a 9 μm particle size was used in this part. It can be clearly seen from Figure 1a that the effect on viscosity was significant in the temperature range of 21~25 °C. The dosages of 1000 ppm and 500 ppm have the most significant effect on crude oil viscosity at 21 °C. The viscosity was reduced to 71,300 mPa·s (21 °C) with 1000 ppm montmorillonite, and further to 61,700 mPa·s (21 °C) with 500 ppm montmorillonite, and the pour point was depressed to 13.5 °C. For the subsequent study, the dosage of montmorillonite was determined to be 500 ppm because it can lower the freezing point and reduce the viscosity relatively more.

3.2. Effect of Particle Size

The amount of montmorillonite was set to 500 ppm for the experiment. It is clearly visible from Figure 2a that all montmorillonite with different particle sizes has a certain viscosity reduction effect. At 21 °C, the viscosity of crude oil decreased sequentially with decreasing particle size. This should be related to the effective concentration of nanoparticles in crude oil. The smaller the particle size, the more effective the sites are, and the higher the effect of reducing viscosity and pour point. As the montmorillonite particle size reached 50 nm, the viscosity reduction rate was 63.3% (21 °C). The pour point was 11.5 °C. In conjunction with the pour point comparison of Figure 2b, 50 nm montmorillonite was selected for subsequent experiments.

3.3. Effect of Modifier Dosage

The effect of modifier (quaternary ammonium salt) dosage used in modification on the viscosity reduction effect of modified montmorillonite was investigated, using tetradecyltrimethylammonium chloride (TTAC). The viscosity reducing effect of modified montmorillonite was evaluated as the mass ratios of modifiers were 0.1 wt%, 1, 10 and 15 wt%, respectively. As can be seen from Figure 3a, the viscosity reduction effect was slightly lower at lower modifier dosages, and the highest viscosity reduction rate of 83.4% (21 °C) was achieved at 10 wt%. The pour point is depressed to 9.0 °C (Figure 3b). Therefore, montmorillonite modified by the 10 wt% modifier was selected for subsequent experiments.

3.4. Effect of Modifier

Quaternary ammonium salts with different alkyl, dodecyltrimethylammonium chloride (C12, DTAC), tetradecyltrimethylammonium chloride (C14, TTAC), cetyltrimethylammonium chloride (C16, TAC), octadecyltrimethylammonium chloride (C18, OTAC) and docosyltrimethylammonium chloride (C22, BTAC) were selected to investigate the effect of modifiers on the viscosity reducing effect of the modified montmorillonite. After being modified by the 10 wt% modifier under the same condition, 500 ppm-modified montmorillonite was added into the crude oil, and the viscosity and the pour point of the crude oil were measured. From Figure 4a, is clearly visible that all the quaternary ammonium modifiers contributed to the viscosity reduction in montmorillonite. The most significant of these was BTAC, which decreased the viscosity up to 96.7% (21 °C) in the low-temperature range and 65.8% (31 °C). In the high-temperature range, while also lowering the pour point to 5.5 °C, a decrease in depression of 15 °C was recorded (Figure 4b). Therefore, BTAC-modified montmorillonite (B@MMT) was selected for subsequent studies.

3.5. B@MMT Dosage Screening

The effect of the amount of modified montmorillonite on the viscosity of crude oil was investigated. From Figure 5a, it can be seen that the viscosity reduction effect was remarkable in the low-temperature range. At 21 °C, the viscosity of the oil sample with 500 ppm B@MMT was only 3980 mPa·s (21 °C), which means that the viscosity was reduced by 96.7% (21 °C). The pour point was depressed to 5.5 °C and the viscosity reduction rate of 500 ppm was higher than that of other dosages. Therefore, the dosage of 500 ppm was determined for the following studies.

3.6. Universalization Evaluation

The universality of the flow improver is an important factor concerning the application; therefore, in this work, the viscosity reducing effect of B@MMT on Xinjiang Hasho oil sample (HQ), Muxiu oil sample (GMX), Yanglou oil sample (YL) and North China high condensate (GN) was evaluated. The viscosity change in these crude oils is shown in Figure 6, and the pour point change is shown in Figure 7. The viscosity of the HQ oil sample with the addition of B@MMT was reduced by 56.1% (30 °C), and the pour point was depressed by 5.0 °C. The viscosity of the GMX oil sample with the addition of B@MMT was reduced by 67.4% (30 °C), and the pour point was depressed by 6 °C. The viscosity of the YL oil sample with the addition of B@MMT was reduced by 93.4% (30 °C), and the pour point was depressed by 9 °C. The viscosity of GN oil with the addition of B@MMT was reduced by 73.4% (50 °C), and the pour point was depressed by 7 °C. The aforementioned research shows that B@MMT is somewhat universal and has a wide range of potential applications.

3.7. DSC Analysis

As the temperature decreases, the wax in the crude oil begins to precipitate and grow, forming a three-dimensional network structure that restricts the flow of liquid hydrocarbons until the entire crude oil loses its fluidity. The thermal behavior of the wax precipitation process of J76 crude oil before and after the addition of nano-modified montmorillonite B@MMT was investigated using differential scanning calorimetry (DSC). From Figure 8, is clearly visible that the wax precipitation point decreased from 20.0 °C to 15.2 °C, and the temperature peak of wax precipitation decreased from 10.0 °C to 6.9 °C. This indicates that the added nanoscale-modified montmorillonite inhibited the wax precipitation from the crude oil, thus reducing the wax precipitation point and wax precipitation peak temperature of the oil samples. The macroscopic effect of condensation reduction and viscosity reduction in the low-temperature range of crude oil was manifested, which may be attributed to the effect of nano-modified montmorillonite co-crystallizing with waxes, inhibiting the precipitation of wax crystals and dispersing wax crystals.

3.8. Microscopic Wax Crystal Morphology Analysis

The effect of nanoscale-modified montmorillonite on wax crystal morphology in saturated hydrocarbons from J76 crude oil was analyzed by optical microscopy at low temperature. The number of wax crystals in the saturated hydrocarbons without B@MMT was enormous and very close, and it is easy to build a network structure, as shown in Figure 9. The number of wax crystals was small and somewhat loose after adding B@MMT, making it difficult to construct a network structure. This suggests that nano-modified montmorillonite exerts an inhibitory effect on wax crystallization and reduces the number of wax crystals at a certain temperature, which can reduce the viscosity of crude oil at that temperature.

3.9. Particle Size Analysis

The particle size of montmorillonite and B@MMT was analyzed with a zeta potential particle size analyzer. It is clearly visible from Figure 10 that the unmodified nano-montmorillonite raw material coexists with large and small particles, and the modified montmorillonite has a more uniform particle size, with particle sizes concentrated in a very small range. The average particle size of unmodified montmorillonite was of 53.97 nm, and in the contrary for B@MMT it was of 45.33 nm. This also shows that the modifier effectively reduces the specific surface energy of the nanomaterial, making it more dispersed and the making the particle size smaller.

3.10. SEM Analysis

The morphology of unmodified montmorillonite and B@MMT was characterized by scanning electron microscopy, and the results are shown in Figure 11. From Figure 11a, it can be seen that the morphology of unmodified montmorillonite was nanosized spherical particles. Moreover, from Figure 11b, it can be seen that the shape and structure of modified montmorillonite basically do not have any visible changes and remain nanosized spherical particles, which is consistent with the results of particle size analysis.

3.11. FTIR Analysis

Comparative analysis of montmorillonite and B@MMT was carried out using FTIR spectroscopy and the results are shown in Figure 12. The new absorption bands at 2973 cm−1, 2846 cm−1 and 2917 cm−1 are attributed to the stretching vibration of the CH vibration band. The new absorption band at 1110 cm−1 is attributed to C-N stretching vibrations. Absorption bands at 1340 and 1381 cm−1 are attributed to the bending vibration of the -CH band, thus proving that the BTAC has been loaded on the montmorillonite.

3.12. Contact Angle Analysis

The 48 μm montmorillonite, 53.97 nm montmorillonite and modified montmorillonite were pressed into thin sheets. The contact angle was measured by adding drops of distilled water and kerosene, and the results are shown in Figure 13. A comparison of the contact angles shows that the contact angles of 48 µm montmorillonite, 20 nm montmorillonite and modified montmorillonite with distilled water increased in that order, and the modified montmorillonite had the largest contact angle with water, which reached 31.75°. The results show that the hydrophobicity of montmorillonite was enhanced after modification, but it still belongs to the hydrophilic category, indicating that most of the hydroxyl groups on its surface are not changed or covered. The contact angles of 48 μm montmorillonite, 20 nm montmorillonite and modified montmorillonite with oil decreased in that order, and the contact angle of modified montmorillonite with oil approached 0°. The above experimental results show that montmorillonite has amphiphilicity, the surface modification by quaternary ammonium salt slightly reduces the hydrophilicity, the lipophilicity was visibly improved and the prepared modified montmorillonite still has amphiphilicity.

3.13. Dispersion Test

The dispersion and stability of modified and unmodified montmorillonite with different particle sizes were evaluated in water and n-octanol (Figure 14). By comparing 1# and 2#, it is evident that the larger particle size disperses well in water, while the smaller montmorillonite is easy to gather and settle. The comparison between 1# and 3# shows that montmorillonite has strong hydrophilicity and was easy to settle in the organic phase. The dispersion and stability of modified montmorillonite in water and n-octanol can be seen by comparing 5# and 6#. Modified montmorillonite was unstable in water and tended to settle, while it was well dispersed in octanol and did not settle easily. The results of the aforementioned studies show that the surface-organized modified montmorillonite can be more evenly distributed in the organic phase, which was advantageous for its use in crude oil.

3.14. Mechanism Analysis

The resin and asphaltenes in crude oil contain a large number of polynuclear aromatics, acyl groups, hydroxyl groups, amine groups, sulfhydryl groups and heterocyclic structures, which form a network structure through hydrogen bonding, π-π stacking and so on, forming part of the viscosity of crude oil. The surface of B@MMT has a large number of silicon hydroxyl and aluminum hydroxyl groups, which can form hydrogen bonds with the above groups, block or weaken the interaction between resin and asphaltene and partially dismantle the network structure [45], so as to achieve the viscosity reduction effect on crude oil (Figure 15). As the temperature lowers, the originally dissolved wax in the crude oil will precipitate and aggregate to form a three-dimensional network structure, resulting in a sharp increase in the viscosity of the crude oil. In the above study, it can be seen that B@MMT has a significant reduction effect on the viscosity of crude oil in the low-temperature region, which is due to the fact that the long-chain alkyl groups on the surface of B@MMT can co-crystallize or adsorb with wax crystal molecules, dispersing the wax crystals, and it can change the crystalline structure of the waxes [46], preventing the wax crystals from growing up to form a network structure (Figure 16).

3.15. Economic Feasibility

The crude oil flow improver raw materials developed in this work are nanosized montmorillonite, BTAC and n-octanol. BTAC in excess or not interacting with the montmorillonite also has the effect of improving the flow of the crude oil; thus, can be used directly without separation [47]. In addition, it also involves energy consumption, packaging, transportation, labor costs, etc. From this, the total cost of B@MMT can be calculated by Equation (1) to be about 7796.87 CNY/ton. The current polymer viscosity reducer, such as commercial-grade EVA, costs 30,000 CNY/ton; the thick oil emulsification viscosity reducer costs 18,000 CNY/ton; and most surfactants used in crude oil, such as industrial grade octadecyldimethylammonium chloride, cost 17,000 CNY/ton. Therefore, the B@MMT crude oil flow improver has a clear commercial competitive advantage and has a very broad application prospect.
C = M 0 ⋅ C 0 + M 1 ⋅ C 1 + M 2 ⋅ C 2 + C X + C Y
where C is the total cost of B@MMT crude oil flow improver, CNY/ton; M0 is the proportion of n-octanol per ton of B@MMT crude oil flow improver containing B@MMT, 0.9230 ton/ton; C0 is the price of n-octanol, 7500 CNY/ton; M1 is the proportion of montmorillonite per ton of B@MMT crude oil flow improver containing B@MMT, 0.0700 ton/ton; C1 is the price of montmorillonite, 8000 CNY/ton; M2 is the proportion of BTAC in the flow improver of crude oil containing B@MMT per ton, 0.0070 ton/ton; C2 is the price of BTAC, 38,000 CNY/ton; CX is the cost of energy consumption for the production of B@MMT per ton, CNY/ton; and CY is the cost of labor for the production of B@MMT per ton as well as the cost of packaging, CNY/ton.
C X = Q + C e
where Ce is the price of industrial electricity in China, 0.725 CNY/kW·h; Q is the electricity consumption for producing one ton of B@MMT, kW·h; CX is the total cost of energy consumption per ton of B@MMT produced, CNY/ton.

4. Conclusions

In this paper, BTAC-modified nano-montmorillonite was prepared as a crude oil flow improver using a simple method. B@MMT prepared by the modification of 50 nm montmorillonite using 10 w% of BTAC can reduce the viscosity by 96.7% (21 °C), depress the pour point by 15 °C at most and reduce the wax precipitation point by 4.8 °C with a dosage of 500 ppm in J76 crude oil. Moreover, B@MMT can reduce the number of wax crystals at low temperature, so that the original dense stacking state can be changed to a sparse state, thereby reducing the pour point and viscosity. Based on the characterization and evaluation of particle size, FTIR, contact angle and dispersion, we elucidated the interaction mechanism of nano-modified montmorillonite with the components in crude oil, which lays a foundation for the subsequent research. Finally, the cost estimate indicates that the price of B@MMT is only 7796.87 CNY/ton, which is much lower than that of similar products in the current market. Therefore, it has obvious commercial competitive advantages and broad application prospects.

Author Contributions

Methodology, G.C.; validation, K.L.; formal analysis, K.L. and M.S.; investigation, M.S., A.G.-S., H.W., L.Z. and J.F.; data curation, A.G.-S., L.Z. and J.F.; writing—original draft preparation, K.L.; writing—review and editing, M.S., G.C. and Y.D.; supervision, M.S., H.W. and Y.D.; project administration, G.C.; funding acquisition, G.C. All authors have read and agreed to the published version of the manuscript.

Funding

The work was supported financially by the National Natural Science Foundation of China (51974252) and the Youth Innovation Team of Shaanxi University. The authors acknowledge the financial support of this research by the Slovak Grant Agency VEGA (2/0166/21) and the Slovak Research and Development Agency (APVV-20-0175). The research in this paper was supported by grant RVO: 11000.

Data Availability Statement

The original contributions presented in the study are included in the articlefurther inquiries can be directed to the corresponding authors.

Acknowledgments

We thank for the work of Modern Analysis and Testing Center of Xi’an Shiyou University.

Conflicts of Interest

Hailong Wang and Liyuan Zhang are employed by the No.11 Oil Production Plant, PetroChina Changqing Oilfield Company. Jiyou Fu is employed by the Changqing Oilfield Shale Oil Development Branch, PetroChina Changqing Oilfield Company. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Minerals 14 00696 g001
Figure 1. Effect of montmorillonite dosage on crude oil (a) viscosity, (b) pour point.
Figure 1. Effect of montmorillonite dosage on crude oil (a) viscosity, (b) pour point.
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Figure 2. Effect of particle size on crude oil ((a): viscosity; (b): pour point).
Figure 2. Effect of particle size on crude oil ((a): viscosity; (b): pour point).
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Minerals 14 00696 g003
Figure 3. Effect of modifier dosage on crude oil ((a): viscosity; (b): pour point).
Figure 3. Effect of modifier dosage on crude oil ((a): viscosity; (b): pour point).
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Figure 4. Effect of modifier on crude oil ((a): viscosity; (b): pour point).
Figure 4. Effect of modifier on crude oil ((a): viscosity; (b): pour point).
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Figure 5. Effect of B@MMT dosage on crude oil ((a): viscosity; (b): pour point).
Figure 5. Effect of B@MMT dosage on crude oil ((a): viscosity; (b): pour point).
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Figure 6. Effect of B@MMT on the viscosity of different oils.
Figure 6. Effect of B@MMT on the viscosity of different oils.
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Figure 7. Effect of B@MMT on pour point of different oils.
Figure 7. Effect of B@MMT on pour point of different oils.
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Figure 8. DSC analysis of crude oil with and without B@MMT.
Figure 8. DSC analysis of crude oil with and without B@MMT.
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Figure 9. Morphology image of wax crystals without (a) and with (b) B@MMT.
Figure 9. Morphology image of wax crystals without (a) and with (b) B@MMT.
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Figure 10. Particle size of montmorillonite particles.
Figure 10. Particle size of montmorillonite particles.
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Minerals 14 00696 g011aMinerals 14 00696 g011b
Figure 11. Scanning electron microscopy results of Na-MMT (a) and B@MMT (b).
Figure 11. Scanning electron microscopy results of Na-MMT (a) and B@MMT (b).
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Figure 12. FTIR spectrum of Na-MMT and B@MMT.
Figure 12. FTIR spectrum of Na-MMT and B@MMT.
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Minerals 14 00696 g013
Figure 13. Contact angle of Na-MMT and B@MMT.
Figure 13. Contact angle of Na-MMT and B@MMT.
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Figure 14. Dispersion of modified and unmodified montmorillonite.
Figure 14. Dispersion of modified and unmodified montmorillonite.
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Figure 15. Mechanism of B@MMT interaction with resin and asphaltene.
Figure 15. Mechanism of B@MMT interaction with resin and asphaltene.
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Figure 16. Mechanism of B@MMT interaction with waxes.
Figure 16. Mechanism of B@MMT interaction with waxes.
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Table 1. Physical analysis of crude oil.
Table 1. Physical analysis of crude oil.
Crude OilPour Point
/°C		Saturated HC
/%		Aromatic HC
/%		Asphaltene
/%		Resin
/%
J7620.5 ± 0.2549.52 ± 1.0031.43 ± 1.007.23 ± 0.2511.82 ± 0.25
GN49.0 ± 0.2562.45 ± 1.5020.12 ± 0.5010.41 ± 0.257.02 ± 0.25
YL31.0 ± 0.2545.63 ± 1.0033.24 ± 1.008.31 ± 0.2512.82 ± 0.25
GMX28.0 ± 0.2531.16 ± 1.0028.73 ± 0.5023.44 ± 0.5016.67 ± 0.25
HQ15.5 ± 0.2530.05 ± 1.0021.15 ± 0.5030.17 ± 1.0018.63 ± 0.25
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Liu, K.; Slaný, M.; Golian-Struhárová, A.; Wang, H.; Zhang, L.; Fu, J.; Chen, G.; Du, Y. Surface-Functionalized Nano-Montmorillonite and Its Application as Crude Oil Flow Improver. Minerals 2024, 14, 696. https://doi.org/10.3390/min14070696

AMA Style

Liu K, Slaný M, Golian-Struhárová A, Wang H, Zhang L, Fu J, Chen G, Du Y. Surface-Functionalized Nano-Montmorillonite and Its Application as Crude Oil Flow Improver. Minerals. 2024; 14(7):696. https://doi.org/10.3390/min14070696

Chicago/Turabian Style

Liu, Kechen, Michal Slaný, Alena Golian-Struhárová, Hailong Wang, Liyuan Zhang, Jiyou Fu, Gang Chen, and Yingna Du. 2024. "Surface-Functionalized Nano-Montmorillonite and Its Application as Crude Oil Flow Improver" Minerals 14, no. 7: 696. https://doi.org/10.3390/min14070696

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