Introduction of Refined Naphthalene

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.

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%).

 **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).