Downstream
Why Do Refineries Use HF?
With the dangers associated with Hydrofluoric acid (HF), the basic assumption that refineries could and should convert their HF processes to the only alternative, Sulfuric Acid is uninformed, and overly simplified.
Though refineries can produce a variety of fuel and oil derived products, any refinery’s ultimate goal is to increase octane. (see explainer – “Octane”) Separate production units take different fractions (distilled oil components) ferried from distillation and other processes to treat those fractions, in large part, for the purpose of increasing their octane rating before introducing the altered fraction into the treating and blending final stages of gasoline production.
One of those units which operates on the lightest fractions cut from the petroleum feedstock is the Alkylation Unit. Raw natural gases stripped out of the petroleum (largely by the Distillation Unit) are processed and separated into homogenous gas mixtures – ie, butane, propane, ethane (referred to collectively as Olefins, or Alkenes). Some of these gases contain “a high-octane number blending components” that when added via blending to the general gasoline pool will increase total octane rating.
The Alklation Unit typically takes two of these gases (referred to as C3-C4), propylene and Butylene, and combines them with isobutane (which in basic terms is a molecularly reconfigured version of butane) to produce alkylate. Alkylate is the resulting high-octane blending component for gasoline.
In order to produce these high octane alkylates, strong acids (either sulfuric acid or hydrofluoric acid) are used as catalysts in being added to the feedstock gases to bring about a chemical reaction that takes these low density gases and produces a higher density product. It does this by altering the chemical structures of the feedstocks and bonding them together.
Though Sulfuric Acid is the more commonly used acid in this process, HF can be more easily regenerated on-site (essentially, recycling spent acid to be used again) and is less sensitive to temperature fluctuations than Sulfuric Acid. And though HF is more expensive, much less is needed in the Alkylation process. Converting an HF operation to Sulfuric Acid is estimated to cost $100 million dollars.
Quotes from https://www.e-education.psu.edu/fsc432/content/alkylation
Though refineries can produce a variety of fuel and oil derived products, any refinery’s ultimate goal is to increase octane. (see explainer – “Octane”) Separate production units take different fractions (distilled oil components) ferried from distillation and other processes to treat those fractions, in large part, for the purpose of increasing their octane rating before introducing the altered fraction into the treating and blending final stages of gasoline production.
One of those units which operates on the lightest fractions cut from the petroleum feedstock is the Alkylation Unit. Raw natural gases stripped out of the petroleum (largely by the Distillation Unit) are processed and separated into homogenous gas mixtures – ie, butane, propane, ethane (referred to collectively as Olefins, or Alkenes). Some of these gases contain “a high-octane number blending components” that when added via blending to the general gasoline pool will increase total octane rating.
The Alklation Unit typically takes two of these gases (referred to as C3-C4), propylene and Butylene, and combines them with isobutane (which in basic terms is a molecularly reconfigured version of butane) to produce alkylate. Alkylate is the resulting high-octane blending component for gasoline.
In order to produce these high octane alkylates, strong acids (either sulfuric acid or hydrofluoric acid) are used as catalysts in being added to the feedstock gases to bring about a chemical reaction that takes these low density gases and produces a higher density product. It does this by altering the chemical structures of the feedstocks and bonding them together.
Though Sulfuric Acid is the more commonly used acid in this process, HF can be more easily regenerated on-site (essentially, recycling spent acid to be used again) and is less sensitive to temperature fluctuations than Sulfuric Acid. And though HF is more expensive, much less is needed in the Alkylation process. Converting an HF operation to Sulfuric Acid is estimated to cost $100 million dollars.
Quotes from https://www.e-education.psu.edu/fsc432/content/alkylation
