CHEMICAL MODIFICATION AND FTIR CHARACTERIZATION OF BITUMEN EXTRACTED FROM HEAVY OIL ROCKS IN CHIMYON DISTRICT

ABSTRACT

This study investigates the structural and chemical transformation of bitumen extracted from heavy oil-bearing rocks located in the Chimyon district of Fergana region, Uzbekistan. The bitumen was isolated through chloroform extraction, yielding approximately 22.5–24.5% of solvent-soluble material. To improve elasticity and thermal behavior, the bitumen was chemically modified using formalin under high-pressure conditions (15 atm, 120°C) for six hours, resulting in the formation of methylol functional groups. FTIR analysis confirmed the appearance of new peaks in the 1000–1300 cm cm^-¹ and 1600–1700 cm cm^-¹ regions, indicating successful incorporation of polar groups. The mechanical properties of the modified bitumen significantly improved, with penetration values increasing at both 25°C and 0°C. This chemical modification effectively enhanced the material's flexibility and made it more suitable for road construction and other industrial applications in cold climates.

АННОТАЦИЯ

В данном исследовании изучается структурно-химическая трансформация битума, добываемого из тяжелых нефтеносных пород, расположенных в Чимёнском районе Ферганской области Узбекистана. Битум был выделен путем хлороформной экстракции, в результате чего было получено приблизительно 22,5-24,5% растворимого материала. Для улучшения эластичности и термического поведения битум химически модифицировали с использованием формалина в условиях высокого давления (15 атм, 120°C) в течение шести часов, в результате чего образовались метилольные функциональные группы. FTIR-анализ подтвердил появление новых пиков в областях 1000-1300 см^-1 и 1600-1700 см^-1, что свидетельствует об успешном включении полярных групп. Механические свойства модифицированного битума значительно улучшились, а значения пенетрации увеличились как при 25°C, так и при 0°C. Это химическое модифицирование эффективно улучшило пластичность материала и сделало его более подходящим для дорожного строительства и промышленного применения в холодных климатических условиях.

Keywords: Bitumen modification, FTIR analysis, formalin treatment, penetration degree, heavy oil rocks.

Ключевые слова: Модификация битума, ИК-Фурье-анализ, обработка формалином, степень пенетрации, тяжелые нефтяные породы.

Introduction

Background of study. The global energy landscape is witnessing a growing interest in unconventional hydrocarbon resources such as heavy oil and natural bitumen. These resources, though technically more challenging to extract and refine, offer significant reserves that can contribute to long-term energy security [1]. In this context, the identification and study of new deposits, especially in geologically complex regions, have become increasingly important [2].

Regional significance of chimyon district. The Chimyon district, located in the Fergana region of Uzbekistan, is a geologically diverse area known for its mountainous terrain and sedimentary formations. Historical observations and geological surveys indicate the presence of heavy oil and bitumen-impregnated rocks in this region. Despite its strategic potential, the area remains underexplored in terms of detailed petrographic and geochemical studies [3-4].

Nature of heavy oil and bitumen deposits. Heavy oil and natural bitumen are highly viscous, semi-solid hydrocarbons typically found in porous rock matrices or impregnated into fractured systems [5]. Their high molecular weight, low API gravity, and high content of asphaltenes and resins make them distinct from conventional light crude oil. Understanding the host rock composition is vital for predicting fluid mobility and developing efficient recovery technologies [6].

Scientific relevance of the study. The petrographic and mineralogical analysis of bitumen-bearing formations can reveal important insights into their genesis, reservoir quality, and alteration history. These analyses not only help in estimating resource potential but also support the design of suitable extraction and processing methods such as thermal recovery, solvent injection, or bio-upgrading [7].

Objectives of the research. Identify and classify the types of rocks containing heavy oil and bitumen in the Chimyon district. Determine the chemical and mineralogical composition of these rocks using modern analytical techniques. Evaluate the spatial distribution and physical properties of the bituminous material. Assess the potential industrial applications of the extracted bitumen and its compatibility with refining technologies [8].

Materials and methods

1. Sample collection. A total of 12 representative rock samples were collected from surface outcrops and shallow boreholes located in the Chimyon district, Fergana region. The sampling sites were chosen based on visual evidence of bituminous saturation, color alteration, and field geologist assessments. Samples were labeled and stored in airtight containers to prevent oxidation.
2. Geological logging and field observations. Each sampling point was documented using geological field log sheets, GPS coordinates, and high-resolution photographs. Field notes included information on lithology, structural orientation (bedding, faulting), color, texture, and visible hydrocarbon presence. Preliminary macroscopic classification was made on-site.
3. Sample preparation. Rock samples containing visible bituminous material were selected for extraction and chemical modification. Approximately 100 g of finely ground rock sample was subjected to solvent extraction using chloroform in a Soxhlet apparatus. The extraction process continued for 12 hours to ensure maximum dissolution of bitumen. As a result, 22.5–24.5% of chloroform-soluble organic matter was obtained relative to the dry sample weight. The obtained chloroform extract was concentrated by evaporating the solvent under reduced pressure. The remaining solid residue, which represents the extracted bitumen, was analyzed for its chemical composition. To enhance the elastic properties of the extracted bitumen, a chemical modification was carried out. The bitumen was treated with formalin under high pressure conditions. Specifically, the extract was mixed with a stoichiometric amount of formalin and subjected to a temperature of 120°C under 15 atm pressure for 6 hours. During this reaction, methylol (–CH₃OH) groups were formed, indicating the initiation of a condensation reaction between the polar components of the bitumen and formaldehyde. Following the pressure treatment, the product was dehydrated at 120°C in an open vessel for 4 hours. This thermal treatment promoted the conversion of aromatic hydrocarbons (such as asphaltenes) present in the bitumen into a thermoplastic resin-like structure. As a result, the bitumen underwent a transition from a brittle, glassy phase to a more elastomeric, flexible structure, improving its applicability in industrial materials.
4. Fourier Transform Infrared Spectroscopy (FTIR). FTIR spectra were recorded using a PerkinElmer Spectrum Two spectrometer in the range of 4000–400 cm^-¹ using KBr pellet technique. The functional groups of organic matter and bituminous components were determined from characteristic absorption bands, such as aliphatic C–H, aromatic C=C, and sulfoxide S=O.
5. Scanning Electron Microscopy (SEM-EDS). Selected samples were examined under a Hitachi S-4800 SEM for detailed morphology and microstructure. Energy-dispersive X-ray spectroscopy (EDS) was employed for elemental composition analysis, especially to detect heavy elements (e.g., Fe, Ni, V) associated with bitumen and clay minerals.

Results and discussion

This section presents and interprets the experimental results obtained from the physicochemical analysis and chemical modification of bitumen extracted from bituminous rock samples of the Chimyon district. The study aimed to evaluate how formalin-induced methylolation affects the structural, mechanical, and thermal behavior of the bitumen. Key properties such as penetration, softening point, ductility, and elasticity were assessed before and after modification to determine the suitability of the treated bitumen for potential industrial applications. Particular attention was given to the temperature-dependent consistency changes, as they directly influence the performance of bitumen under service conditions.

Figure 1. Penetration degree at 25 and 0 ^oC of natural bitumen

Figure 1 shows a clear comparison between unmodified and formalin-modified bitumen samples in terms of their penetration values at two different temperatures (25 °C and 0 °C):

• At 25 °C, the penetration value increased from 35 (0.1 mm) in the unmodified sample to 65 (0.1 mm) after modification.
• At 0 °C, the penetration value rose from 18 (0.1 mm) to 51 (0.1 mm) following modification.

These results indicate a substantial improvement in bitumen flexibility due to formalin treatment. The increase in penetration values at both temperatures suggests that the bitumen has transitioned from a rigid, glassy structure to a more elastic and softer material. This transformation is particularly crucial at low temperatures, where brittleness typically leads to cracking in bituminous materials. The modified bitumen’s ability to maintain higher penetration at 0 °C demonstrates enhanced performance under cold climate conditions, making it more suitable for road construction and coating applications where thermal resistance and elasticity are critical.

Figure 2. FTIR of Natural bitumen

This FTIR spectrum displays transmittance (%) versus wavenumber (cm cm^-¹) and appears to compare two samples, likely representing unmodified and formalin-modified bitumen. The differences between the two spectra reflect chemical structural changes due to the modification process.

1. Region: 2850–2950 cm^-¹ (C–H Stretching)

• Strong absorption peaks in this range are associated with aliphatic CH₂ and CH₃ stretching vibrations.
• Both spectra show pronounced peaks here, indicating the presence of saturated hydrocarbon chains.
• However, changes in peak intensity may suggest increased chain mobility or structural reorganization due to modification.

2. Region: 1600–1700 cm cm^-¹ (C=C and C=O Stretching)

• Absorptions in this region indicate the presence of aromatic rings (C=C) or carbonyl (C=O) groups.
• The modified sample shows noticeable variations, implying that formalin treatment induced chemical changes, possibly forming new polar groups or altering aromatic character.

3. Region: 1000–1300 cm cm^-¹ (C–O Stretching and S=O)

• This area corresponds to C–O stretching vibrations, typical for alcohols, esters, or sulfoxide groups.
• The enhanced peaks in the modified sample suggest the formation of methylol (–CH₃OH) groups due to reaction with formalin.

4. Region: 600–900 cm cm^-¹ (Aromatic C–H Bending)

• Peaks in this range are attributed to out-of-plane bending of aromatic C–H bonds.
• Both samples exhibit these features, confirming the continued presence of aromatic structures even after modification.

Conclusion

The FTIR spectral analysis of bitumen samples extracted from the Chimyon region revealed significant structural and compositional differences between the unmodified and formalin-modified samples. Characteristic peaks corresponding to aliphatic (CH₂ and CH₃) and aromatic hydrocarbons were observed in both spectra, confirming the presence of complex hydrocarbon matrices. However, the modified bitumen exhibited increased absorption in the regions associated with polar functional groups, particularly in the 1000–1300 cm cm^-¹ and 1600–1700 cm cm^-¹ ranges. These changes indicate the successful incorporation of methylol groups (–CH₃OH) and the transformation of aromatic asphaltenes into more elastic resin-like structures. Such chemical modifications are essential for improving the mechanical and rheological properties of bitumen, making it more suitable for industrial applications such as road surfacing, waterproofing, and insulation materials.

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