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All Florida Biodiesel, Inc. Equipment Is Compatible With Enzyme Transesterification

Written by admin on March 07, 2025

Below is an outline of the transesterification process using Candida antarctica lipase B (CALB) as the catalyst to produce biodiesel. This process converts triglycerides (from oils or fats) into fatty acid methyl esters (FAME, i.e., biodiesel) and glycerol, leveraging CALB’s enzymatic prowess under mild, eco-friendly conditions.

Transesterification Process Using CALB as Catalyst

1. Preparation of Raw Materials

  • Feedstock: Select an oil or fat source (e.g., vegetable oil, waste cooking oil, or animal fat). CALB handles high free fatty acid (FFA) content (up to 15–20%), so minimal pretreatment is needed compared to chemical catalysts.
    • Example: Used cooking oil with 10% FFA.
  • Alcohol: Typically methanol, though ethanol can be used. Methanol is preferred for its low cost and faster reaction with CALB. Ratio: 3:1 to 6:1 molar ratio of methanol to triglycerides (stoichiometric need is 3:1, but excess drives completion).
  • Catalyst: Immobilized CALB (e.g., Novozym 435), dosed at 1–5% (w/w) of the oil weight. Immobilization on resin or silica enhances stability and reusability.

2. Reaction Setup

  • Reactor: Batch or continuous stirred-tank reactor, often with temperature control and mixing.
  • Conditions:
    • Temperature: 30–50°C (optimal for CALB activity; higher risks denaturation).
    • Pressure: Atmospheric (no high-pressure equipment needed, unlike some chemical processes).
    • Mixing: Gentle agitation to ensure contact between oil, methanol, and enzyme without damaging immobilized CALB.
  • Methanol Addition: Stepwise dosing (e.g., 1/3 of total methanol added every 2–4 hours) to avoid enzyme inhibition, as CALB is sensitive to high methanol concentrations.

3. Transesterification Reaction

  • Mechanism:
    1. CALB’s active site binds the triglyceride, cleaving ester bonds.
    2. Methanol reacts with the liberated fatty acid chains, forming FAME.
    3. Glycerol is released as a by-product.
  • Chemical Equation:
    Triglyceride + 3 Methanol → 3 FAME (biodiesel) + Glycerol
    (Catalyzed by CALB)
  • Duration: 6–24 hours, depending on feedstock, methanol dosing, and enzyme loading. Waste oils may take longer due to impurities.
  • Yield: Typically 90–98% FAME with optimized conditions.

4. Product Separation

  • Phase Separation: Stop mixing; the mixture settles into two layers:
    • Top: Biodiesel (FAME) with some excess methanol.
    • Bottom: Glycerol with water, methanol traces, and minor impurities.
  • Catalyst Recovery: If immobilized, CALB is filtered or centrifuged out for reuse (up to 10–50 cycles with minimal activity loss).
  • Washing: Biodiesel layer is washed with water to remove residual methanol and glycerol. CALB’s clean reaction minimizes soap formation, simplifying this step compared to chemical catalysis.

5. Purification and Finishing

  • Distillation: Excess methanol is distilled from both biodiesel and glycerol phases for recovery and reuse.
  • Drying: Biodiesel is dried (e.g., via vacuum or molecular sieves) to meet standards like ASTM D6751 (water content <0.05%).
  • Glycerol Refining: Glycerol can be purified for industrial use (e.g., cosmetics, pharmaceuticals).
  • Quality Check: Biodiesel is tested for ester content (>96.5%), viscosity, and impurities.

6. Process Outputs

  • Biodiesel: Primary product, ready for use in diesel engines or blending (e.g., B20).
  • Glycerol: Marketable by-product, typically 10% of oil mass.
  • Recycled Inputs: Methanol and CALB (if immobilized) reused, boosting cost-efficiency.

Key Features of CALB in This Process

  • Mild Conditions: Low temperature and pressure reduce energy costs vs. chemical catalysts (60–80°C, sometimes pressurized).
  • FFA Tolerance: Directly esterifies FFAs into biodiesel alongside transesterification, ideal for waste oils.
  • Clean Reaction: No soap formation, less wastewater than NaOH-based methods.
  • Trade-Offs: Slower than chemical catalysts (hours vs. minutes) and higher enzyme cost, offset by reusability and sustainability gains.

Example Workflow

  • Input: 1 kg waste cooking oil (10% FFA), 200 g methanol (6:1 molar ratio), 30 g Novozym 435.
  • Process: Mix at 40°C, add methanol in three steps over 12 hours, stir at 200 rpm.
  • Output: ~950 g biodiesel (95% yield), 100 g glycerol, recovered CALB for next batch.

This outline reflects CALB’s practical application in lab and pilot-scale settings—scalable with tweaks like continuous reactors or methanol control systems.