Introduction To Refined Naphthalene Products

Refined naphthalene is a high-purity naphthalene (C₁₀H₈) product, typically obtained by further purifying industrial naphthalene, with a purity of over 99%. Its CAS number is 91-20-3, and its molecular formula is C₁₀H₈. It appears as white or slightly reddish plate-like crystals and has a mild aromatic odor (while crude naphthalene has a coal tar smell). As an important organic chemical raw material, refined naphthalene is widely used in the fields of dyes, pharmaceuticals, and synthetic resins.

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Physical and Chemical Properties

The physical and chemical characteristics of pure naphthalene are as follows:

- **Melting Point**: 80.1°C

- **Boiling Point**: 217.9°C

- **Flash Point**: 80°C (open cup)

- **Density**: 1.16 g/cm³ (water = 1)

- **Solubility**: Insoluble in water, readily soluble in organic solvents such as ethanol, ether, and benzene.

- **Hazard**: It is a flammable solid (Class 8 hazard label), and when mixed with air, it can form an explosive mixture (explosion limit 0.9% - 5.9%).

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 **Production Process**

The production of refined naphthalene mainly falls into two categories:

1. **Tar Naphthalene**

- The raw material comes from coal tar, in which the naphthalene content is approximately 8% to 12%. The naphthalene oil fraction (210 to 230°C) is separated through distillation and then purified by processes such as dephenolization, desulfurization, and acid washing, ultimately yielding refined naphthalene with a purity of ≥99%.

2. **Petroleum Naphthalene**

- The raw material is a by-product of petroleum processing such as catalytic reforming and cracking. Through a hydrogenation dealkylation reaction (with Cr₂O₃-Al₂O₃ as the catalyst) to remove impurities like methyl groups, followed by distillation purification, the purity can reach 99.73%.

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 **Quality Indicators**

According to the national standard "GB/T 6699-1998", refined naphthalene is classified into premium grade, first grade, and qualified grade. The main indicators are as follows:

| Item         | Premium Grade | First Grade | Qualified Grade | |--------------|--------------|--------------|--------------|

| Appearance | White flaky crystals | Slightly pinkish white | Slightly yellowish white crystals |

| Purity (%) | ≥99.3 | ≥98.95 | ≥98.5 |

| Melting point (℃) | ≥79.8 | ≥79.5 | ≥79.3 |

| Ash content (%) | ≤0.006 | ≤0.008 | ≤0.01 |

 **Application Areas**

1. **Dyes and Intermediates**

- Used in the synthesis of dye intermediates such as 2-naphthol, 1-naphthol, and methylnaphthylamine.

2. **Pharmaceuticals and Pesticides**

- Serves as a raw material for the synthesis of antibiotics, insecticides, and camphor.

3. **Synthetic Materials**

- Involved in the production of phthalic anhydride (PA), plasticizers, rubber antioxidants, and naphthalene-based water reducers.

4. **Other Uses**

- Wood preservatives, moth repellents (such as mothballs), and surfactants.

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**Packaging and Storage**

- **Packaging Specifications**: 25kg/bag or 50kg/bag (lined with polyethylene bags and covered with woven bags), liquid products can be transported by tank trucks.

- **Storage Conditions**: Cool and well-ventilated place, away from fire sources and strong oxidants (such as potassium permanganate), avoid direct sunlight.

- **Shelf Life**: 36 months (unopened).

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**Safety and Environmental Protection**

1. **Health Risks**

- Inhaling high concentrations of naphthalene vapor can cause headaches and nausea. Long-term exposure may damage liver and kidney functions.

2. **Leakage Handling**

- Use explosion-proof tools to collect the leaked material, avoid creating dust, and isolate and ventilate the contaminated area.

3. **Firefighting Measures**

- Carbon dioxide or water in a fine spray are recommended as extinguishing agents. Do not directly aim at molten material to prevent splashing.