Hydrotreated Naphtha is a full-range naphtha stream recovered as a byproduct from a diesel hydrotreater operating in mild hydrocracking mode (MHC), in which a fraction of the diesel-range feed (typically straight-run gas oil) undergoes limited conversion into lighter, highly saturated naphtha-range hydrocarbons. Unlike conventionally processed naphtha, this stream is typically not fractionated into separate light and heavy naphtha cuts, and is instead routed directly as an unsplit, full-range feedstock to the steam cracker.
Origin and production
In a mild hydrocracking configuration, the DHDT operates at severities beyond conventional desulfurization, achieving typically 10–40% conversion of the gas oil feed into lower-boiling products. The reactor effluent fractionation yields:
- A naphtha fraction (typically boiling in the C₅–180 °C range),
- The main product: ultra-low-sulfur diesel,
- And minor off-gases (C₁–C₄), which join the refinery gas/LPG recovery system.
The naphtha cut, being already deeply hydrogenated in the high-pressure hydrogen environment, emerges as a premium-quality stream requiring no further treatment.
Characteristics
- Highly paraffinic: Rich in normal and iso-paraffins formed by hydrocracking — the ideal cracker feed components for high ethylene yields.
- Very low contaminants: Sulfur and nitrogen are reduced to < 1 ppm levels; olefins and aromatics are minimal, since hydrocracking saturates unsaturates and hydrocracks aromatic rings to paraffins/naphthenes.
- Full-range composition: Retains both the light (C₅–C₇) and heavy (C₈–C₁₀+) portions in one unsplit stream — acceptable as cracker feed because the steam cracker furnace and its downstream separation train can accommodate the full boiling range without the pre-splitting required for, e.g., catalytic reformer feed preparation.
- Consistent quality: Composition is stable and predictable, set by the MHC operating severity rather than crude slate variations.
Why unsplit for cracker feed
Splitting naphtha into light and heavy fractions is normally done to segregate feedstocks by end use — light naphtha to isomerization or cracker, heavy naphtha to the catalytic reformer for aromatics/gasoline. When the sole destination is the steam cracker, however, both fractions are equally valuable feed, and the splitter is unnecessary — avoiding capital cost, energy consumption, and intermediate tankage.
Here are suggested entries for the Hydrotreated Naphtha (Full-Range, from Mild Hydrocracking) product record. As a petroleum refining stream (UVCB substance), it falls under the standard regulatory category for hydrotreated light/middle distillate naphthas:
Chemical Data
| Field |
Entry |
| Chemical Formula |
Mixture: predominantly C₅–C₁₁ paraffins and naphthenes (representative: C₇H₁₆–C₁₀H₂₂) |
| Molecular Weight (g/mol) |
~95–115 (average ~105 for full-range cut) |
| Freezing Point (°C) |
< −60 (typically −70 to −90, depending on n-paraffin content; not a practical concern) |
| Boiling Point (°C) |
Range: ~35–180 °C (IBP–FBP of full-range naphtha, C₅–180 °C) |
| Melting Point (°C) |
Not applicable (liquid mixture; same as freezing range) |
| Sulfur Content (wt%) |
< 0.0001 wt% (< 1 ppm) — hydrocracked naphtha is essentially sulfur-free; typical 0.1–0.5 ppm |
| Specific Gravity |
~0.72–0.76 at 15 °C (API gravity ~55–65°) |
| PIONA composition |
~70–85% paraffins (high n- + iso-paraffin content), 10–20% naphthenes, < 5% aromatics, olefins < 1% |
| Nitrogen |
< 0.5 ppm |
