You’re looking at one of the most important plasticizers in modern manufacturing: diisononyl adipate, or DINA. If you work in plastics manufacturing, you’ve likely heard the industry quietly shift away from traditional phthalate plasticizers. DINA represents that shift—a safer, more sustainable alternative that performs exceptionally well in demanding applications.
This article walks you through the complete synthesis process of DINA, from raw materials to finished product. You’ll learn the chemistry, the two main manufacturing methods, the critical control points, and why one approach might make sense for your operation while another might not.
How is DINA Synthesized?
At its core, DINA synthesis relies on a single fundamental reaction: esterification. This reaction happens when an acid (adipic acid) meets an alcohol (isononyl alcohol) and they bond together, releasing a water molecule in the process.
The reaction looks straightforward on paper. In reality, it’s a balancing act. The reaction naturally reaches an equilibrium—meaning it doesn’t spontaneously drive all the way to completion. To push the reaction forward and achieve high conversion rates, you need to remove that water byproduct continuously.
Two distinct approaches dominate DINA manufacturing today: the traditional chemical catalyst method and the modern enzymatic method. Each has fundamental differences in operating conditions, efficiency, and environmental impact.
The Traditional Chemical Catalyst Method
For decades, manufacturers relied on chemical catalysts to drive DINA synthesis. This approach still dominates industrial production, and it works reliably when executed properly.
How the Reaction Happens
Chemical catalysts accelerate the esterification reaction by creating an alternative pathway that requires less energy. Common catalysts include magnetic nanometer-sized solid superacids, composite solids, and tin oxide (SnO) loaded on activated carbon fiber. These catalysts don’t participate directly in the reaction—they facilitate the chemistry without being consumed.
The reaction mixture gets heated to 130–140°C. At these temperatures, the catalyst becomes active, and the adipic acid and isononyl alcohol begin combining. The process typically requires 3 hours of heating to drive the reaction substantially forward.
Step-by-Step Process
Loading the Reactor
You start by loading the reactor with adipic acid and isononyl alcohol in a carefully controlled ratio. Most industrial processes use a molar ratio of adipic acid to isononyl alcohol somewhere between 1:1 and 1:3, depending on desired product purity and conversion efficiency. The catalyst gets added at roughly 1–5% by weight of your total substrate. Some processes add a solvent at this stage, though modern approaches increasingly work without solvents to reduce waste.
The First Heating Phase
Once loaded, you heat the mixture for about 1 hour at 130–140°C. During this phase, the catalyst activates, and the esterification reaction begins producing small amounts of water. You’ll notice the mixture’s viscosity slowly increasing as the ester forms.
Mid-Process Adjustments
After the initial hour, many processes introduce additional components—like phenoxyethanol—to optimize product properties. Heating continues for another 2+ hours while temperature remains constant. The goal here is to drive the conversion as high as possible before you begin purification.
Monitoring Progress
Throughout this heating phase, you’re tracking conversion percentage. The reaction naturally produces water, which escapes as vapor at these temperatures. By monitoring weight loss and viscosity changes, you can estimate how much of your starting material has converted to DINA. Typical processes achieve 85–99% conversion depending on how aggressively you optimize conditions.
Purification and Product Recovery
After the heating phase completes, you move to purification. This is where you separate pure DINA from unreacted materials and catalyst residue.
Filtration removes solid catalyst particles. Then you typically employ distillation to separate DINA from any remaining unreacted adipic acid or isononyl alcohol. If you used an acid-based catalyst, you may neutralize the mixture to remove residual acid before distillation.
The result: pure DINA at ≥99.5% purity, meeting commercial specifications.
The Modern Enzymatic Synthesis Method
A more recent approach harnesses biological catalysts—specifically, lipase enzymes—to accomplish the same synthesis at dramatically lower temperatures. This method represents a significant shift toward sustainability and efficiency.
Why Enzymatic Catalysis Differs
Enzymes are biological proteins that catalyze reactions with remarkable specificity. The enzyme used in modern DINA synthesis is Eversa lipase, sourced from the fungus Thermomyces lanuginosus. It was originally developed for biodiesel production but has proven exceptionally effective for ester synthesis.
The critical difference: enzymes work at temperatures around 50°C instead of 130–140°C. That’s an 80°C reduction, which translates directly to lower energy consumption. The enzymatic reaction also requires no solvent—adipic acid and isononyl alcohol combine directly in the presence of immobilized enzyme and water is removed under mild vacuum.
Step-by-Step Enzymatic Process
Enzyme Preparation
The lipase enzyme needs to be immobilized—attached to a solid support—to make it reusable and easier to separate from the product. Eversa lipase typically gets immobilized onto Lewatit VP OC 1600, a specially designed carrier material. This immobilization doesn’t damage the enzyme. Instead, it preserves its catalytic activity while making it practical for repeated use.
Setting Up the Solvent-Free System
You load adipic acid and isononyl alcohol directly into the reactor in a 1:3 molar ratio (adipic acid to isononyl alcohol). The immobilized enzyme enters next. Importantly, no organic solvent gets added. This solvent-free approach dramatically simplifies product isolation and eliminates solvent waste.
Establishing Optimal Conditions
Now you control five critical parameters simultaneously:
The temperature must sit at precisely 50°C—not higher, not lower. Enzymes are sensitive to temperature, and exceeding 50°C reduces their activity. The enzyme requires a specific water activity (measure of moisture) of 0.75. This might sound precise, but it’s actually well-established in biocatalysis and easily maintained through controlled humidity or water addition.
Vacuum application matters immensely. You apply 13.3 kPa vacuum—not atmospheric pressure. This vacuum pulls water vapor from the reaction mixture continuously, driving the equilibrium forward without actually reaching boiling temperatures. The enzyme loading typically runs at 10% by weight of your total substrate.
Reaching Completion
Under these optimized conditions, the reaction reaches 100% conversion in 6 hours. That’s complete transformation of starting materials into product—something the chemical method sometimes struggles to achieve at high efficiency.
Product Isolation and Enzyme Reuse
Once the reaction finishes, separating pure DINA becomes remarkably simple. The immobilized enzyme sits in the reactor as a solid. You can remove it directly, either washing it for reuse or setting it aside. The liquid DINA product flows out cleanly, requiring minimal additional purification compared to the chemical method.
This enzyme reusability represents a major economic and environmental advantage. One batch of immobilized enzyme can perform multiple synthesis cycles, dramatically reducing per-unit enzyme costs.
Choosing Between Synthesis Methods
Both methods work. Your choice depends on several factors.
If you prioritize established infrastructure and proven reliability, the chemical catalyst method makes sense. Equipment is available everywhere. Supply chains are mature. You’ll find extensive troubleshooting experience in the industry.
If energy efficiency and environmental impact drive your decisions, enzymatic synthesis offers compelling advantages. It cuts energy consumption dramatically. It eliminates waste streams. It aligns with modern sustainability commitments that increasingly matter to customers and regulators.
If you’re scaling production, consider economics carefully. Chemical catalysts have lower initial investment but higher ongoing operational costs. Enzymatic systems have higher upfront infrastructure but lower operational costs and potentially better profit margins on high volumes.
A direct comparison reveals the trade-offs:
Temperature Requirements: Chemical methods demand 130–140°C. Enzymatic methods operate at 50°C—that’s 62% less thermal energy required.
Catalyst Cost and Availability: Solid superacid catalysts cost less per unit than enzymes, but enzymes get reused repeatedly, amortizing their cost across multiple synthesis cycles.
Environmental Impact: Chemical methods generate acid waste and produce byproducts requiring disposal. Enzymatic methods run solvent-free with minimal waste.
Conversion Efficiency: Chemical methods achieve 85–99% conversion. Enzymatic methods achieve 100% conversion under optimal conditions.
Processing Time: Both methods complete in similar timeframes (3–6 hours), though enzymatic methods involve lower temperatures throughout.
Waste Generation: Chemical methods create solid catalyst residue and acid neutralization waste. Enzymatic methods produce immobilized enzyme (easily recycled) and essentially nothing else.
Ease of Scale-up: Chemical methods scale readily using proven equipment designs. Enzymatic methods scale well but require more specialized bioreactor expertise.
Enzyme Reusability: This is enzymatic synthesis’s unique advantage. You can reuse the same immobilized enzyme 20+ times, significantly improving economics at volume.