Liquid pyrolysis products (LPP) are large-tonnage by-products of the pyrolysis of hydrocarbons - the main process of modern petrochemistry. The main olefins of the pyrolysis of hydrocarbons are ethylene and propylene. Currently, ethylene production is booming, its production capacity is increasing every year. There are 11 ethylene plants operating in Russia with a total ethylene production capacity of about 3 million tons per year, while the share of LPP is 20-25%.
LPP are a complex mixture of hydrocarbons of various structures and is a valuable and inexpensive raw material for producing a large number of substances.
Integrated processing of LPP significantly improves the economic efficiency and profitability of the entire ethylene production.
WE HAVE DEVELOPED a new concept for the integrated processing of liquid pyrolysis products to produce high-margin commercial products.
THE MAIN IDEA OF THE CONCEPT is the combination of selective chemical reactions with mass exchange processes, which will allow creating almost waste-free processing technologies for LPP.
The main advantage of the developed approach is the absence of expensive stages of preliminary cleaning of raw materials for the production of final products.
SCHEME OF LPP COMPLEX PROCESSING
COMPLEX PROCESSING OF C5 FRACTION
Fraction C5, separated by distillation from LPP in the range from the beginning of boiling to 70°C (10-25% of LPP), contains on average up to 60% of dienes (isoprene, cyclopentadien, piperylene), 15-16% of olefins and alkanes.
We have developed a practically waste-free scheme for processing the C5 fraction to produce popular products — PVC plasticizers, monomers to produce new polymeric materials, a hardener of epoxy resins, a high-octane fuel additive, high-quality solvent for paints and varnishes.
The scheme includes, at the first stage, the removal of dienes from the fraction. At the second stage, the interaction of the olefins remaining in the fraction with benzene and the preparation of a mixture of alkyl benzenes and then the isolation of the light fraction of saturated hydrocarbons.
At the first stage, two variants of processing the C5 fraction are possible.
In the first variant, the C5 fraction is treated with maleic anhydride for selectively removing of 1,3-dienes (isoprene, piperylene and cyclopentadiene) to obtain a mixture of anhydrides, which, after distilling off unreacted components of the fraction, remain cubed. The melting point of the mixture of anhydrides is 62-65 ° C.
The mixture of anhydrides can be used as a hardener of epoxy resins or can be reacted with aliphatic alcohols, for example 2-ethylhexanol, to produce a non-toxic phthalate-free plasticizer for PVC. As an alcohol component in addition to pure 2-ethylhexanol, you can use the by-products of the production of butyl or 2-ethylhexyl alcohols (Application for invention No. 2018116976).
In the second variant, the C5 fraction is first treated with a diester of fumaric acid (for example, di-2-ethylhexylfumarate). In this case only cyclopentadiene (CPD) selectively reacts with fumarate to form the diester of norbornene dicarboxylic (endic) acid, which is easily separated from the reaction mass. The resulting diester can be used as a non-toxic plasticizer for PVC (Patent RU 2625788).
In addition, endic acid diesters after additional purification can be used as monomers for metathesis ring-opening polymerization in the production of modern polymeric materials.
The isoprene and piperylene remaining in the fraction after CPD removal then react with maleic anhydride to form a mixture of two anhydrides, which can also be used as a hardener of epoxy resins or as a raw material for the production of PVC plasticizer.
Olefins and alkanes remain in the C5 fraction after removal of 1,3-dienes. Olefins may be involved in the reaction of liquid-phase alkylation of benzene, obtained from the C6 fraction. As a result, a mixture of alkyl benzenes and cycloalkanes is formed, which remains cubed after distillation of light compounds and excess benzene.
A mixture of alkyl benzenes and cycloalkanes can be used as a high-octane fuel additive or a good low toxic solvent in the paint industry.
The distillate of light compounds after the alkylation process is a mixture of alkanes (paraffins), isoalkanes (isoparaffins) and cycloalkanes (naphthenes). It is, in fact, light gasoline, which can be sent to re-pyrolysis or used as a solvent.
Distilled excess benzene is recycled.
PROCESSING OF THE C6 BENZENE FRACTION
The benzene fraction of C6 with a benzene content of ~ 95%, in addition to traditional use for the isolation of pure benzene, can be used to produce maleic anhydride by the known method of vapor-phase heterogeneous-catalytic oxidation of benzene.
The process takes place at 350-400 ° C, catalyzed by a mixture of vanadium and molybdenum oxides, which is usually applied to wide-porous Al2O3. The yield of maleic anhydride is 70-75%. Since the process is supposed to be conducted without prior isolation of pure benzene, the resulting maleic anhydride will have a significantly lower cost. It can be used to obtain the above products from the C5 fraction or petroleum resins (PS) from the C9 fraction.