Analytical Instrumentation & Environmental Monitoring

Alkylation processes in petroleum refineries

April 2021 Analytical Instrumentation & Environmental Monitoring

Motor fuel alkylation using liquid hydrofluoric (HF) or sulphuric (H2SO4) acids is a catalytic process used in petroleum refinery operations. The purpose of the alkylation is to improve fuel properties to achieve higher octane for lower emissions which is an important process in petrochemical alkylation operations.

While the H2SO4 alkylation scores points with safety and environmental protection aspects, the HF alkylation typically shows efficient acid recycling. Olefins and the isoalkanes from raw oil resulting from fluid catalytic cracking (FCC) constitute the starting materials. Together with HF and/or H2SO4 as catalyst, high-grade alkylates are formed. Due to their high octane rating, few aromatic compounds and comparably environmentally friendly properties, they are perfectly suitable for petrol blending from both an economic and an ecologic point of view.

The most important requirement for the alkylation system is error-free operation to prevent e.g. an ‘acid runaway’, which can occur when the acid strength goes below 85-87%. In this case the reactions between the olefins and the iso-butane turn into reactions of olefins only, producing polymers known as acid sludge, red oil or ASO (acid soluble oil). To prevent this, control of the acid, water and ASO quantity is of particular importance.

Traditional sampling is potentially very dangerous, time intensive and the results only arrive after some hours of laboratory testing. Here the LiquiSonic scores points with immediate inline analysis and data recording as well as increased system productivity and safety.

The robust LiquiSonic measuring technology has set benchmarks in three-component analysis for years. Using select specialty materials, it effectively prevents corrosion, abrasion and drift, even under difficult conditions. The LiquiSonic immersion sensors can be easily installed directly into the pipeline and are ATEX-, IECEx- and FM-certified.

Possible installation locations include upstream and downstream of the acid separator and at the alkylate outlet of the iso stripper. Despite difficult, corrosive process conditions, utilising materials such as Hastelloy C-276 or Monel, long-term system stability is possible.

The LiquiSonic controller is connected to the sonic velocity sensor and a density measuring device. In the main menu, the controller displays the concentration values of the HF/acid and the ASOs.

For more information contact Morton Controls, 0861 000 393,


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