Question

The correct statements about Zeolites are: 
1. They are good shape selective catalysts
2. They contain Al-O-Si framework
3. They are not found in nature
4. They are used as catalysts for cracking hydrocarbons in the petrochemical industry.

• A. I & II only
• B. II & III only
• C. I, II & IV only
• D. I, II, III & IV

Hint:

Key properties of zeolites: 1. Microporous aluminosilicate minerals 2. Act as molecular sieves due to uniform pore size 3. Both natural and synthetic forms exist 4. Important in petroleum refining and water softening

Answer 1

The Correct Option is C

Statement I: Correct. Zeolites are widely used as shape-selective catalysts due to their porous structure.
Statement II: Correct. Zeolites have a three-dimensional Al-O-Si framework with well-defined pores and cavities.
Statement III: Incorrect. Zeolites \textit{are} found in nature (e.g., volcanic rocks) and can also be synthesized artificially.
Statement IV: Correct. Zeolites (especially ZSM-5) are extensively used in petroleum refining for catalytic cracking of hydrocarbons.
Thus, the correct combination is I, II, and IV only, making option (3) correct.

Answer 2

Step 1: Understand the structure of Zeolites.
Zeolites are crystalline aluminosilicates composed of a three-dimensional framework of \(\text{Al-O-Si}\) tetrahedra.
This framework creates pores and cavities, giving zeolites their unique properties.

Step 2: Analyze the given statements.
1. Zeolites are good shape selective catalysts.
- Correct. Their porous structure allows selective catalysis based on molecular size.

2. They contain Al-O-Si framework.
- Correct. The fundamental structure of zeolites is an aluminosilicate framework.

3. They are not found in nature.
- Incorrect. Zeolites occur naturally as minerals, though synthetic versions are also widely used.

4. They are used as catalysts for cracking hydrocarbons in the petrochemical industry.
- Correct. Zeolites are extensively used as catalysts in fluid catalytic cracking due to their acidity and shape selectivity.

Step 3: Conclusion.
The correct statements are I, II & IV only.