Here you move the "cut" and "PNA" you read about in the body text. The numbers are concept scores, not measurement predictions, so do not treat them like a real spec sheet.
Entry point: high-school chemistry equations and mole ratios
Terms to know before this page
Normalisation
Converting raw weights into proportions by rescaling them to sum to 1 or 100%. P / N / A character is set by relative ratio, not absolute amounts, so without normalising the totals you cannot compare cases.
Relative indicator
A score that highlights the "up / down" direction rather than predicting measured values.
Preset
A one-click setting that loads a typical combination.
What you are looking at
The cut slider runs from light to heavy. Toward the heavy side, the average carbon number rises.
The P / N / A sliders are raw weights. In the calculation they are normalised into proportions.
The relative indicators are there to help you see "which way is it moving?"
A good first pass is to click through the presets in order — Light paraffinic → Balanced → Reforming-oriented → Aromatic-rich — which makes it easy to separate the cut axis from the composition axis. The reason this preset-first approach matters: beginners typically conflate "cut" and "PNA composition," so isolating each axis up front prevents that mix-up before free exploration begins.
PNA × cut concept simulator
This simulator is not a plant model that predicts real measured values. It is a concept model that shows which indicators move, and in which direction, as light / heavy and PNA change.
55
45
35
20
Normalised composition
P
45%
N
35%
A
20%
Average carbon number and boiling range
Average carbon number
8.0
Boiling start
60.3 °C
Boiling end
152.8 °C
Relative indicators
Relative volatility49
Relative density47
Octane tendency38
Steam-cracking suitability55
Reforming suitability49
Four experiments to try
Click "Light paraffinic" and watch the steam-cracking suitability rise.
Click "Reforming-oriented" and see the reforming suitability and octane tendency both go up.
Keep the same preset and drag only the cut toward the heavy side — relative volatility falls.
Click "Aromatic-rich" and watch relative density and octane tendency move upward.
Self-check
Four questions that check whether the simulator display is lining up with the body text.
Q 5-1 — What runs high under "Light paraffinic"
Which suitability tends to run high when you press the "Light paraffinic" preset?
Steam-cracking suitability.
Reforming suitability.
Density.
Show answer and reasoning
Answer: A
A light cut with a large paraffin share fits the steam-cracking storyline.
Q 5-2 — Centre of the "Reforming-oriented" preset
In the "Reforming-oriented" preset, which molecular family is thickest?
Paraffins.
Naphthenes.
Aromatics.
Show answer and reasoning
Answer: B
The "Reforming-oriented" preset thickens the naphthene share to make the link to reforming easy to see.
Q 5-3 — Holding composition constant, moving the cut heavier
Holding composition fixed and shifting the cut toward the heavy side, what happens to relative volatility?
It rises.
It falls.
It does not change.
Show answer and reasoning
Answer: B
Even at the same composition, pulling in more of the heavy side lowers volatility.
Q 5-4 — What rises under "Aromatic-rich"
Which relative indicator tends to rise under the "Aromatic-rich" preset?
Density.
Volatility.
Steam-cracking suitability.
Show answer and reasoning
Answer: A
More aromatics pushes density and octane tendency up in this concept model.
Chapter 5 summary
Moving the cut toward the heavy side raises the average carbon number and lowers volatility.
A thicker paraffin share emphasises the cracking storyline; a thicker naphthene share emphasises the reforming storyline.
Aromatics push density and octane tendency upward.