Module 11 – Process Chemistry & Raw Materials

Objective:
By the end of this module, a trainee will be able to:

1. Understand the basic chemistry behind butadiene production.

2. Identify common feedstocks and their properties.

3. Understand the main reactions involved in the process.

4. Recognize separation principles used to purify products.

5. Appreciate how feedstock quality affects process performance and product quality.

11.1 – Introduction to Butadiene Chemistry

Definition:

• Butadiene (C4H6) is a conjugated diene used mainly in synthetic rubber production.

• Its chemistry involves dehydrogenation, cracking, and separation.

Operator Relevance:

• Operators do not need to perform chemistry calculations, but understanding reactions helps in troubleshooting and monitoring.

Analogy:

• Butadiene production = “cooking recipe”: proper ingredients, heat, and timing produce desired product.

11.2 – Common Feedstocks

1. C4 Raffinate / Cracked Gas:

• Derived from naphtha or butane/steam cracking.

• Contains: butadiene, butenes, butanes, and trace impurities.

2. Butane / Butenes (Optional Feed):

• May be used in dehydrogenation units.

Key Operator Points:

• Feedstock quality affects reaction efficiency.

• Contaminants (sulfur, oxygenates) can poison catalysts.

• Flow rate, pressure, and temperature must be monitored.

Analogy:

• Feedstock = “ingredients in a cake”: quality affects final taste/product.

11.3 – Main Reactions (Conceptual)

1. Dehydrogenation Reaction:

• Converts butenes → butadiene by removing hydrogen.

• Endothermic: requires heat.

• Operator relevance: monitor temperature, pressure, and reactor feed.

2. Cracking Reactions:

• Converts larger hydrocarbons → smaller ones, including butadiene.

• Temperature and residence time control product distribution.

3. Side Reactions:

• Polymerization of butadiene

• Formation of other C4 hydrocarbons

• Operator relevance: ensure cooling, inhibitors, and proper residence time

Analogy:

• Dehydrogenation = “removing water from wet clothes to dry them”

• Cracking = “breaking big chocolate chunks into smaller pieces for candy mix”

11.4 – Separation & Purification

Purpose:

• Remove impurities and isolate high-purity butadiene.

Methods (Conceptual):

1. Distillation Columns: separate components based on boiling point differences.

2. Absorption / Extraction: remove polar or undesirable compounds.

3. Drying / Scrubbing: remove water or acid gases.

Operator Relevance:

• Monitor temperature, pressure, and level in distillation and absorption units.

• Ensure cooling, feed, and reflux are within operational limits.

• Troubleshoot off-spec product by checking feed and separation conditions.

Analogy:

• Separation = “filtering sand from sugar”: pure sugar is obtained after removing impurities.

11.5 – Product Quality Considerations

Key Parameters:

• Butadiene purity (affects polymer quality)

• Hydrocarbon impurities (affects downstream processing)

• Moisture and acid traces (affects stability)

Operator Role:

• Monitor process variables that influence product quality.

• Log deviations in feedstock, temperature, or separation conditions.

• Alert supervisor or lab for product sampling and analysis.

Analogy:

• Product quality = “cake texture and taste”: depends on ingredients, oven temperature, and baking time.

11.6 – Conceptual Operator Tips

1. Feedstock Control: maintain consistent flow and quality.

2. Temperature Monitoring: critical for reaction selectivity and safety.

3. Pressure Control: ensures proper residence time and separation efficiency.

4. Separation Units: monitor column levels, reflux ratio, and cooling.

5. Communication: coordinate with lab for product testing and quality assurance.

11.7 – Quiz / Knowledge Check

1. What is the main chemical reaction to produce butadiene?

2. Name two common feedstocks for butadiene production.

3. Why is feedstock quality important?

4. Name two methods used to separate butadiene from C4 mixture.

5. What process variables affect product purity?

6. Give an analogy for separation/purification in everyday life.

11.8 – Suggested Media for Google Sites Integration

• Videos:

  • Conceptual animation of dehydrogenation reaction

  • C4 feedstock processing and separation overview

  • Distillation column operation animation

• Diagrams / Infographics:

  • Feedstock → reaction → separation → product diagram

  • Main reactions vs side reactions

  • Conceptual product quality flowchart

• PDF Downloads:

  • Feedstock quality checklist

  • Separation unit monitoring template

  • Operator reaction monitoring guide

• Interactive:

  • Embedded quizzes

  • Scenario exercises: troubleshoot feed or separation issue

11.9 – Summary & Key Takeaways

1. Butadiene production involves dehydrogenation and cracking reactions from C4 feedstocks.

2. Feedstock quality directly affects reaction efficiency and product purity.

3. Separation and purification ensure high-purity butadiene for downstream use.

4. Operators monitor feed, reactor, and separation units, maintaining safe and efficient operation.

5. Understanding basic chemistry helps troubleshoot issues and ensure consistent product quality.