STUDY OF THE COMPOSITIONAL CHARACTERISTICS OF PYROLYSIS LIQUID BASED ON CHROMATOGRAPHIC ANALYSIS

УДК 66.092-977

Abstract

The increasing accumulation of waste automobile tires has become a significant environmental challenge worldwide, creating an urgent need for effective recycling technologies. This study investigates the purification and compositional characteristics of pyrolysis liquid obtained from the thermal decomposition of vulcanized rubber waste. Sulfur-containing compounds were removed from the liquid fraction using an Al₂O₃-based adsorbent derived from industrial waste sludge. Chemical analysis, X-ray fluorescence (XRF), and scanning electron microscopy (SEM) were employed to characterize both the adsorbent and the pyrolysis products.

The pyrolysis process was conducted at 650–700 °C, and the resulting liquid fraction was analyzed to determine its chemical composition.

The results revealed that the liquid mainly consisted of C5–C6 and C7 aliphatic hydrocarbons, benzene, and other aromatic and aliphatic compounds. XRF analysis of the waste sludge indicated an aluminum content of approximately 75 wt.%, confirming its suitability as a low-cost precursor for Al₂O₃-based adsorbents. The application of the obtained adsorbent effectively reduced the concentration of sulfur-containing compounds in the pyrolysis liquid.

The findings demonstrate the potential of utilizing industrial waste materials for the purification of pyrolysis liquids and contribute to the development of environmentally sustainable technologies for waste tire recycling. Furthermore, the proposed approach promotes resource recovery and enhances the value of pyrolysis products through desulfurization and compositional improvement.

Аннотация

Рост количества отработанных автомобильных шин во всем мире представляет собой серьезную экологическую проблему, что обусловливает необходимость разработки эффективных технологий их переработки. В данной работе исследованы процессы очистки и изучения компонентного состава пиролизной жидкости, полученной при термическом разложении вулканизированных резиновых отходов. Для удаления серосодержащих соединений из жидкой фракции использован адсорбент на основе Al₂O₃, полученный из промышленного отхода – шлама. Для характеристики адсорбента и продуктов пиролиза применены методы химического анализа, рентгенофлуоресцентного анализа (XRF) и сканирующей электронной микроскопии (SEM).

Процесс пиролиза проводился при температуре 650–700 °С, после чего полученная жидкая фракция была исследована с целью определения её химического состава. Установлено, что пиролизная жидкость преимущественно состоит из алифатических углеводородов С5–С6 и С7, бензола, а также других ароматических и алифатических соединений. Результаты XRF-анализа шлама показали содержание алюминия на уровне около 75 мас.%, что подтверждает возможность его использования в качестве дешевого сырья для получения адсорбентов на основе оксида алюминия. Применение полученного адсорбента обеспечило эффективное снижение содержания серосодержащих соединений в пиролизной жидкости.

Полученные результаты подтверждают перспективность использования промышленных отходов для очистки пиролизных жидкостей и способствуют развитию экологически безопасных технологий переработки изношенных автомобильных шин. Предложенный подход обеспечивает рациональное использование вторичных ресурсов и позволяет повысить потребительскую ценность продуктов пиролиза за счет их десульфуризации и улучшения компонентного состава.

Keywords: Tire pyrolysis oil (TPO); waste rubber; low-temperature pyrolysis; desulfurization; fractional distillation; FTIR analysis; alternative fuel.

Ключевые слова: Пиролизное масло (ППМ); отходы резины; низкотемпературный пиролиз; десульфуризация; фракционная перегонка; ИК-Фурье анализ; альтернативное топливо.

Introduction

 In recent decades, the rapid growth of the global automotive industry has led to a continuous increase in the amount of end-of-life tires. Currently, approximately 7–8 million tons of waste tires are generated annually worldwide. In the United States alone, this amount reaches 1.8–2.0 million tons, while in the United Kingdom nearly 0.45 million tons of waste tires accumulate every year, of which more than 40% are recycled and the remainder are incinerated or landfilled. Used tires contain 60–65 % rubber, 18–22 % carbon black, and 10–12 % steel cord, making them valuable secondary raw materials. Among chemical recycling technologies, pyrolysis occupies a special place, since it enables the conversion of waste tires into pyrolysis liquid, gas, and solid residues. Pyrolysis liquid possesses high calorific value and can be used as fuel or chemical feedstock. Therefore, studies aimed at improving the compositional characteristics and purification of pyrolysis liquid are of considerable scientific and practical importance [2].

Research Object The research object of this study is waste vulcanized rubber materials, primarily used automobile tires, which serve as the main raw material for low-temperature pyrolysis. These materials consist of a complex composite structure including natural and synthetic rubbers, carbon black, sulfur compounds, metal cord, and various additives used during tire manufacturing.

Methods and materials

Pyrolysis liquid obtained from waste automobile tires was selected as the research object. Aluminum-containing sludge was investigated for sulfur removal from the liquid, and its structural composition was studied using X-ray phase diffraction analysis. The experiments were carried out using a “Shimadzu XRD-6100” powder X-ray diffractometer equipped with a copper (Cu) anode tube (Kα₁ = 1.5406 Å, Kα₂ = 1.5443 Å, Kα₂/Kα₁ = 0.5). [3-4].

Results and discussion

 Urrently, desulfurization processes aimed at removing sulfur-containing compounds such as thiophene, benzothiophene, and dibenzothiophene from pyrolysis liquid are widely applied. Literature analysis indicates that Al₂O₃ is an effective adsorbent due to its high surface area and the presence of acidic-basic active centers capable of adsorbing sulfur-containing aromatic compounds. However, considering the economic aspects of Al₂O₃ production and the increasing use of local and waste-derived materials, waste sludge was selected as an alternative raw material in this study [5-7].

According to XRF analysis, the aluminum content in the sample reached 75.5 wt.%, indicating that aluminum was the dominant component. The relatively high sulfur content (10.8 wt.%) suggested the sulfate nature of the material. These findings confirmed that the waste sludge can serve as a suitable raw material for obtaining aluminum oxide (Al₂O₃) [8].

Table 1. Main elemental composition of sludge (XRF analysis)

The obtained XRF results demonstrated that the sludge was highly enriched with aluminum. Chemically, the material may correspond to Al₂(SO₄)₃ or similar aluminum salts. Although XRF analysis does not directly detect Al₂O₃, the high aluminum content confirms the suitability of this waste material for the production of aluminum oxide through subsequent chemical processing [9-10].

The liquid products formed during thermal decomposition were initially purified from water and suspended impurities. Subsequently, several fuel mixtures were prepared using different ratios of waste and purified fractions, namely 80:20, 70:30, and 50:50. The resulting samples were analyzed under laboratory conditions. Their main physical and эксплуатационные properties are presented below.

Table 2. Main properties of pyrolysis liquid

The obtained results indicate that the prepared pyrolysis fuel samples satisfy the requirements of current standards and can be considered suitable for practical application. Spectroscopic analysis also demonstrated a significant reduction in sulfur-containing compounds after treatment. Furthermore, chromatographic analysis revealed the presence of various aliphatic and aromatic hydrocarbons in the pyrolysis liquid. These compounds included C₅–C₆ and C₇ aliphatic hydrocarbons, benzene, toluene, ethylbenzene, xylene, styrene, indene, naphthalene, alkylnaphthalene, polycyclic aromatic hydrocarbons, and heavy resin-like fractions.

Table 3. Compounds identified in pyrolysis liquid

The presence of styrene is associated with the decomposition of styrene-butadiene rubber. The identified aromatic compounds contribute significantly to the fuel characteristics of pyrolysis oil.

Conclusion

The conducted studies demonstrated that the pyrolysis liquid obtained from vulcanized rubber waste through thermal decomposition at 650–700 °C possesses a complex chemical composition. XRF and chromatographic analyses confirmed the predominance of low-molecular-weight aliphatic and aromatic hydrocarbons in the liquid phase. The use of waste sludge based on Al₂O₃ proved to be an effective approach for sulfur removal from pyrolysis liquid.

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