α-Pinene (alpha-Pinene) and β-Pinene (beta-Pinene) are crucial natural monoterpene substances, widely applied across various sectors such as the synthesis of fragrances and flavours, deep processing of terpene resins, and the production of other fine chemicals. As vital terpene compounds, they can be efficiently and highly purely extracted from naturally renewable gum turpentine. α-Pinene and β-Pinene not only undergo deep biomass processing according to downstream supply chain demands but also actively integrate into the entire sustainable circular production system, fully demonstrating their significant green and environmental value.

From Batch to Continuous Vacuum Distillation

In its nascent stages in mainland China (roughly the 1980s to the 1990s), the industrial separation and production of α-Pinene (alpha-Pinene) and β-Pinene (beta-Pinene) primarily relied on single-column batch steam distillation under atmospheric or slightly reduced pressure. This was a classic batch operation, fundamentally based on the boiling point differences between components. The core of this technique involved using steam as a heating source to perform fractional distillation of crude turpentine feedstock within a rectification column, effectively separating the pinene components.

During the process, turpentine underwent steam stripping in a distillation column equipped with a certain number of theoretical plates. Through this fractional distillation, α-pinene, β-pinene, and some dipentene, along with other components, were collected at various distillate fractions. Any unqualified fractions or bottom liquids would be collected and re-distilled.

While the equipment required for these early processes was relatively simple, making them suitable for small to medium-scale factory production, their drawbacks were evident. These included high energy consumption, operating temperatures that were too high and could lead to product degradation and increased colouration, limited product purity (typically 85-90%), and difficulties in byproduct recovery. Nevertheless, due to the comparatively simpler structure of batch distillation equipment—such as the reboiler, column, and condenser—and its ability to quickly achieve the basic separation and production of pinene, this intermittent process was widely adopted in mainland China during the early period of reform and opening up to generate foreign exchange.

As continuous vacuum distillation technology progressively emerged, the production processes for α-/β-pinene gradually transitioned to adopt this more advanced method. This technology can be further subdivided into single-column multi-stage vacuum distillation and two-column continuous vacuum distillation, offering superior solutions for achieving high-purity and energy-efficient separation of α-/β-pinene.

This technological route fully leverages the relatively significant boiling point differences between α-pinene, β-pinene, and other components in turpentine (such as dipentene and high-boiling point substances). It achieves highly efficient separation through a continuous operation mode: gum turpentine feedstock is continuously fed into the distillation column, while products and residual liquids are continuously withdrawn from the column. By reducing the pressure at the top of the column, the operating temperature is consequently lowered significantly. This not only substantially mitigates the risk of material thermal decomposition but also reduces its boiling temperature. Coupled with continuous feeding and the application of highly efficient column internals, the purity of pinene can be elevated to over 95%.

Compared to batch distillation, continuous vacuum distillation significantly lowers the overall operating temperature, impacting both the column top and reboiler temperatures. This dramatically reduces the thermal degradation and isomerisation of pinene, effectively inhibiting resin formation and mitigating product colouration issues. Consequently, this leads to a substantial increase in product yield and quality. Furthermore, thanks to its more precise component separation, this technology consistently produces α-/β-pinene with higher purity.

Core Advantages of Continuous Vacuum Distillation Technology
Optimised Product Quality and Yield Lower Operating Temperature: A substantial reduction in both column top and reboiler temperatures dramatically minimises the thermal degradation and isomerisation reactions of pinene during the distillation process. This effectively inhibits resin formation and reduces the incidence of product colouration, fundamentally enhancing product stability. Increased Yield and Quality: By reducing heat loss and side reactions, the technology not only ensures high product purity but also significantly boosts the overall product yield.
Enhanced Separation Efficiency and Product Purity Precise Component Separation: Continuous operation, combined with optimally designed distillation columns (typically featuring more theoretical plates or high-efficiency packing), leads to vastly improved mass transfer efficiency. This enables more precise component separation, consistently producing α-pinene and β-pinene with purity exceeding 95%.
Significant Energy Saving Reduced Heat Source Demand: Vacuum operation lowers the boiling points of materials, consequently reducing the demand for high-temperature heat sources required for heating, which directly cuts energy consumption. High Thermal Efficiency: The continuous, stable operating mode boasts superior thermal efficiency compared to batch operations, resulting in lower overall energy consumption and aligning with principles of green production.
Increased Production Efficiency and Equipment Utilisation Continuous Stable Operation: This technology eliminates the non-productive times inherent in batch operations, such as loading, unloading, heating up, and cooling down, thus achieving a continuous and automated process flow. High Production Capacity and Equipment Utilisation: The continuous and stable production mode leads to a substantial increase in equipment production capacity, while also significantly boosting equipment utilisation rates, bringing greater economic benefits to the enterprise.

In Europe and North America, factories primarily collect pinene raw materials via the Crude Sulphate Turpentine (CST) process route. This is largely due to the region’s abundance of long-established, technologically advanced, and large-scale modern pulp mills. These mills generally prioritised and invested earlier in the construction of highly efficient CST recovery systems. Furthermore, Southern Yellow Pine (P.palustris) is frequently the predominant pinene source in these areas. This tree species, processed through the CST method, yields a higher α-pinene content (reportedly, North American Southern Yellow Pine contains approximately 60~70% α-pinene).

Due to the variations in tree species distribution across different countries, Chinese mainland commonly selects Masson Pine, Slash Pine, and Simao Pine as raw materials for turpentine separation. Consequently, their component content naturally differs from that of Southern Yellow Pine. For instance, Masson Pine from Chinese origins typically has a higher α-pinene content than Slash Pine, while Simao Pine from Yunnan province boasts the highest α-pinene content. Slash Pine, conversely, is rich in α-pinene, with its content exceeding that of β-pinene. Other components, such as camphene, myrcene, carene, and dipentene, also vary depending on the origin and tree species.

From a resin acid perspective, Masson Pine and Armand’s Pine (P.armandi) are abundant in Abietic acid, making them highly suitable for deep processing to produce hydrogenated rosin resins and electronic solders. In contrast, Yunnan Pine is rich in Palustric acid and Levopimaric acid. After modification, it exhibits excellent oxidative stability, rendering it ideal for deep processing into printing ink resins to significantly enhance their anti-yellowing performance.

Advancements in Energy Integration and Multi-Section Reflux

Since the 2010s, the industry has increasingly adopted energy integration technologies in pinene distillation systems to further boost energy efficiency. This technology’s core principle revolves around the ‘circular utilisation’ of heat within the system. It effectively transfers waste heat or low-grade heat generated by one process unit to another unit requiring heating, significantly cutting down on reliance on external energy sources like steam and electricity.

Specifically, the pinene distillation process involves both heating (in the reboiler) and cooling (in the condenser). Given that α-pinene has a lower boiling point than β-pinene, it releases heat when it condenses at the top of the distillation column. Energy integration technology ingeniously captures and harnesses this heat (the temperature of which typically depends on the vacuum level). Although this isn’t a high-temperature heat source, it’s sufficient for:

• Preheating the cold turpentine feedstock entering the distillation system.
• Supplying partial or full heat requirements to the reboilers of other separation columns within the system (e.g., β-pinene columns or light component removal columns), thereby achieving thermal coupling between columns.

For instance, employing a thermally coupled double-column design can typically reduce steam consumption by over 20~40%. The application of energy integration technology has remarkably lowered the total energy consumption of the entire distillation system, reduced steam and cooling water usage, and substantially enhanced energy utilisation efficiency. This marks a crucial step towards achieving green and sustainable production.

Unlike traditional distillation columns, which feature only a single top reflux and a bottom reboiler, the multi-section reflux process incorporates an innovative internal heat integration design. This technology permits the withdrawal and treatment (e.g., cooling) of material (liquid or vapour) from intermediate points within the distillation column, before it’s returned to form an intermediate reflux, or for direct heat exchange.

This design enables the formation of multiple independent temperature control zones inside the column, allowing for far more precise control over component separation. By establishing isothermal zones at different column sections, a multi-section reflux distillation column can significantly optimise the separation process and effectively reduce the risk of thermal cracking. Concurrently, each independent intermediate reflux ratio facilitates the accurate separation of α- and β-pinene and other key components.

These combined technical improvements dramatically enhance product yield and the stability of the final product, ensuring the high-quality output of pinene.

Deep Vacuum Multi-section Distillation stands as one of the forefront processes in current distillation technology. This advanced technique ingeniously integrates sophisticated optimisation methods such as energy integration and multi-section reflux, thoroughly showcasing its outstanding application within the field of distillation.

This technology typically achieves absolute pressures as low as 20 kPa, or even below 5 kPa. It utilises more than two fractionation sections (which can be either columns in series or columns with internal multi-sections) to perform extremely precise separation of heat-sensitive terpene components or crude wood byproducts, based on their boiling point gradients.

Its scope of application is extensive, with notable results. For example, Finland’s Neste Corporation, leveraging its NEXPINUS™ solution based on this technology, successfully produces Tall Oil Fatty Acid (TOFA) with purity exceeding 95% and high-grade Tall Oil Rosin (TOR). Throughout the crude tall oil refining process, other components like tall oil pitch can also be separated under deep vacuum and at higher temperatures of 220-280°C, then used as combustion fuel, thereby maximising resource utilisation.

In recent years, several leading global enterprises, including China’s NHU, Sweden’s SunPine, and Germany’s Symrise, have all expanded their pinene distillation production lines. This underscores the robust market demand for high-purity pinene products and the recognition of advanced distillation technologies. Notably, SunPine invested SEK 35 million in 2023 to construct a new α-pinene production line. Furthermore, after adopting the NEXPINUS™ solution, Finland’s Fintoil factory saw its crude tall oil annual capacity reach 200,000 tonnes, making it the third-largest crude tall oil refinery globally. These cases undeniably showcase the immense potential of deep vacuum multi-section distillation technology in boosting capacity and industry standing.

The ongoing advancements in pinene production processes, particularly innovations in energy integration and efficient heat utilisation, are playing a pivotal role in reducing carbon footprints. For instance, France’s DRT company fully leverages its production waste wood (DRT AB plante) and distillation by-products (DerTal product line) as fuel for its biomass power station. Currently, this power station has achieved a thermal efficiency exceeding 65%. According to DRT’s reports, when the biomass power station’s thermal efficiency surpasses 60%, it can reduce carbon dioxide emissions by up to 20,000 tonnes (20 kt) annually.

This innovative Combined Heat and Power (CHP) solution not only converts biomass fuel into steam and electricity but, more importantly, it facilitates a closed-loop green production system, transforming waste into valuable energy. Currently, 73% of the energy supply for DRT’s steam and electricity co-generation at its French production site originates from the aforementioned biomass fuel. This not only highlights the company’s steadfast commitment to environmental protection but also sets a benchmark for sustainable development across the industry.

α/β-Pinene Deep Processing Applications

α-Pinene and β-Pinene, vital monoterpene compounds found in nature, are not only abundant natural green chemicals but also indispensable, versatile starting materials in the fine chemical industry. This is due to their unique chemical structures and high reactivity. Through reactions like isomerisation, pyrolysis, hydration, oxidation, hydrogenation, and polymerisation, they can be used to produce monomeric substances such as camphene, myrcene, pinonic acid, pinane, terpineol, and borneol. These compounds offer vast potential for the synthesis of numerous high-value chemicals, serving as crucial building blocks for modern fine chemical industry supply chains. They’re extensively used in daily chemical formulations, plant protection, and as pharmaceutical intermediates.

From initial distillation separation to the complex and diverse chemical transformations available today, the application value of pinene is continuously being discovered and expanded. Whether through rearrangement, oxidation, reduction, or polymerisation, these two natural terpenes can yield a wide array of intermediate and end products. They serve various industries, showcasing immense potential in driving industrial upgrades and green development. As research progresses, more downstream monomers are finding widespread use. For instance, myrcene can be further processed into linalool, which in turn can lead to the production of linalyl acetate and citral – key intermediates for Vitamin A/E synthesis. Similarly, α-pinene can be oxidised to produce pinene oxide, which then yields substances like verbenol and verbenone. Furthermore, α-pinene and β-pinene can undergo polymerisation to create high-grade terpene resins.

Common downstream products of α-Pinene and β-Pinene
Isomerisation Reactions	Camphene: Pinene can be isomerised to produce camphene, a key precursor in the synthesis of pharmaceutical and fragrance products like camphor and borneol. Myrcene: Another important isomerisation product, myrcene, demonstrates multi-layered value in its applications. Downstream, it can be further processed to prepare linalool, a widely popular fragrance component. A deeper application involves linalool’s downstream products, such as linalyl acetate and citral. These are not only star products in the flavour and fragrance industry but also crucial intermediates for Vitamin A/E synthesis, significantly expanding pinene’s application value in the nutritional and healthcare sectors.
Hydration and Addition Reactions	Terpineol: Pinene can undergo hydration to form terpineol. Known for its pleasant pine scent, terpineol is widely used in daily chemical products such as detergents, soaps, and air fresheners. Borneol: With its refreshing and invigorating properties, borneol holds a significant position in the pharmaceutical, fragrance, and cosmetics sectors.
Oxidation Reactions	Pinene Oxide: alpha-pinene can be oxidised to produce pinene oxide. Further downstream, this yields compounds like verbenol and verbenone. These substances possess unique aromatic properties and are distinctly applied in the high-end flavour and fragrance and daily chemical industries.
Hydrogenation Reactions	Pinene can be hydrogenated to produce pinane, which can be used as a high-energy fuel additive or as a green solvent in certain specialised organic synthesis reactions.
Pyrolysis Reactions	Under specific conditions, pyrolysis can transform pinene into other commercially valuable alkenes, such as terpinene.
Polymerisation Reactions	Through polymerisation, α-pinene and β-pinene can be processed into high-grade terpene resins. These resins, known for their excellent adhesive properties, tackiness, ageing resistance, and electrical insulation, find widespread and crucial applications in areas such as adhesives (e.g., pressure-sensitive adhesives, hot-melt adhesives), coatings, inks, rubber, and electronic materials. High-quality terpene resins significantly enhance product performance and stability, making them indispensable components in the formulations of numerous industrial products.

Given their diverse chemical transformation capabilities, α-pinene and its derivatives are extensively applied across numerous core industries. They meet varied demands ranging from everyday consumer products to high-end technologies. This isn’t merely an extension of chemical synthesis; it embodies the green chemistry principle of deriving high-value products from renewable natural resources. With the deepening integration of biotechnology and chemical engineering, future research into pinene deep processing will become even more profound. Its application scope will continue to broaden, providing innovative, efficient, and environmentally friendly solutions for various sectors, jointly driving the industrial chain towards a more sustainable future.

Fine Application of Downstream Products of α-Pinene and β-Pinene
Daily Chemical Formulations	As pivotal components in fragrances and flavours, cosmetics, and personal care products, they impart unique aromas and functionalities, enabling the creation of fresh, woody, and floral scent profiles, for example.
Plant Protection	Certain pinene derivatives can serve as biopesticides, plant growth regulators, insect repellents, or pesticide adjuvants, offering safer and more environmentally friendly plant protection solutions for modern agriculture.
Pharmaceutical Intermediates	Many pinene derivatives are crucial intermediates in the synthesis of various drugs (such as anti-cancer agents, anti-inflammatory drugs, and nervous system medications), providing essential raw material support for innovation and development within the pharmaceutical industry.
Inks and Coatings	Terpene resins and their derivatives impart excellent adhesion, gloss, and abrasion resistance to inks and coatings, significantly enhancing product performance.
Adhesives and Sealants	As tackifiers and resin components, they play a crucial role in products such as tapes, labels, construction adhesives, and hot-melt glues, ensuring superior bond strength and durability.
Other Fine Chemicals	They are also applied in rubber processing aids, food additives (for instance, as solvents or flavouring agents), and the synthesis of certain high-performance materials, thereby meeting the diverse demands of various industries for advanced materials and specialised chemicals.

Environmental Issues Requiring Further Attention

While the continuous advancements in distillation technology have significantly boosted product yield and capacity, and made remarkable contributions to carbon footprint reduction, we still need to confront the environmental challenges it faces. A core issue among these is the presence of low molecular weight volatile organic compounds (VOCs) entrained in the top condenser’s waste gases.

Taking the production of α- and β-pinene as an example, under deep vacuum operating conditions, the top condenser temperature typically ranges between 80 – 120 °C. It’s crucial to note that while deep vacuum operation substantially lowers the system’s total pressure and component boiling points (which is vital for mitigating the thermal decomposition risk of heat-sensitive pinene and enabling separation at lower temperatures), vacuum itself doesn’t eliminate vapour pressure differences between components. During distillation, components with higher vapour pressure tend to enter the gas phase and rise to the top of the column, whereas those with lower vapour pressure are more inclined to remain in the liquid phase and descend. Consequently, light components such as methanol, ethanol, methyl mercaptan, hydrogen sulphide, and dimethyl sulphide (DMS), which have significantly higher vapour pressures than pinene, maintain a high partial vapour pressure even at the top condenser temperature. This makes them difficult to fully liquefy alongside the main distillate. They accumulate at the top of the column and primarily exist in gaseous form within the waste gases from the condenser, becoming potential emission sources.

On the other hand, the sulphate pulping process uses an alkaline cooking liquor containing sulphides (like sodium sulphide, Na₂S) to effectively remove lignin from wood. The small amounts of organic sulphur naturally present in the wood, along with the sulphur from the cooking liquor, react in complex ways with organic matter in the wood under high-temperature alkaline conditions. This forms various organic sulphur compounds, such as mercaptans (R-SH) and sulphides (R-S-R). When crude tall oil (CTO) or crude sulphate turpentine (CTP) is processed at high temperatures, the mercaptans and sulphides they contain can further undergo thermal cracking and decomposition reactions. These reactions produce smaller, more volatile sulphur-containing gases, some of which, like H₂S, MeSH, and DMS, have unpleasant odours that can potentially impact the environment.

In 2024, Kraton Corporation in the United States invested $35 million to complete the upgrade of its former crude tall oil (CTO) distillation column in Panama City, a facility originally owned by Arizona Chemical.

For a long time, environmental pollution issues linked to the former Arizona Chemical plant had been severely criticised by local residents. This dispute dates back to 2009, when Arizona Chemical closed its Port St. Joe plant and relocated production to its Panama City facility, adjacent to a WestRock Company paper mill. Although odour complaints near the site eased after WestRock permanently shut down its Panama City paper mill in 2022, citing return on investment considerations, environmental concerns, including odour and groundwater contamination, still persist and continue to draw complaints from residents.

With the paper mill now closed, public attention naturally shifted to the neighbouring distillation plant. In response, Kraton has committed to implementing the Ecosorb solution in 2024 for further odour adsorption treatment. This aims to resolve the odour issues related to their operations at the source and address community concerns.

Conclusion

Distillation technology plays a pivotal role as the core separation and purification method in pinene production, whether based on Gum Turpentine (GT route) or Crude Sulphate Turpentine (CST) processes. These two routes, due to fundamental differences in their raw material sources and process characteristics, each face unique environmental challenges and technical limitations.

Regarding the GT route, widely adopted in countries like China and Brazil, it inherently avoids the pungent odours caused by volatile sulphur compounds in the CTO/CST system because it doesn’t involve sulphate digestion. However, this route still comes with the characteristic piney aroma of turpentine itself. Additionally, emitted monoterpene VOCs are prone to photochemical reactions under sunlight and nitrogen oxides (NOₓ), promoting ozone formation and potentially impacting ambient air quality. Consequently, the GT route is better suited for applications demanding higher product purity and specific odour profiles, or for small to medium-scale production needs.

Summary of different pinene routes

Gum Turpentine (GT) Route: The Gum Turpentine (GT) route directly relies on the refined management and sustainable harvesting of forestry resources. This makes it a natural fit for small to medium-sized projects focused on fine products and low emissions. This route emphasises the gentle utilisation of natural resources and, crucially, reduces specific pollutants right at the source.

CST Route: The Crude Sulphate Turpentine (CST) route, on the other hand, boasts the distinct advantage of high-value circular utilisation of pulp industry by-products. This makes it better suited to meet the high capacity demands of bulk resins and integrated pulp and paper mills. It represents a path towards more promising sustainable development, effectively seeking a balance between efficient resource utilisation and environmental protection by transforming what was originally waste into high-value chemical products.

Admittedly, no industrial technological route can achieve absolute perfection. Under current conditions, production processes often involve a degree of ‘unavoidable pollution.’ Continuous technological improvement and innovation are therefore essential to overcome these inherent drawbacks and drive industrial progress.

Looking ahead, the choice of pinene process routes will increasingly prioritise the balance between ‘economies of scale‘ and ‘sustainability.’ As green chemistry and sustainable development philosophies gain deeper traction, future pinene production will continuously explore more environmentally friendly, efficient solutions through technological innovation, capable of meeting diverse market demands.