Slurry Hydroconversion of Polymer Mixtures
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Solution Overview
Problem
Current chemical recycling processes for plastics, such as polyethylenes and polypropylenes, face inefficiencies in producing monomers or high-quality fuel oils, leading to low yields and the formation of coke, which causes fouling and limits continuous operation, making them unsuitable for industrial application.
Innovation Solution
A hydroconversion process that pre-treats polymer mixtures using mechanical, chemical, or thermal methods, then mixes them with a vacuum hydrocarbon residue and a molybdenum catalyst precursor, followed by hydroconversion in a slurry phase to produce naphtha cuts, allowing for the recycling of plastics into valuable petrochemical products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If chemical recycling processes are used to produce monomers or fuel oils from plastics, then plastic waste can be converted into valuable products, but the processes suffer from low yields and coke formation that causes fouling and limits continuous operation
Solution Approach 1:
The patent applies parameter changes by modifying the chemical environment through catalyst selection (metal sulfides like MoS2, WS2, WSe2), controlling reaction temperature (300-500°C), pressure (1-10 MPa), and hydrogen partial pressure to optimize depolymerization reactions. These parameter adjustments enable continuous operation while maintaining high yields of desired products by preventing coke formation on catalyst surfaces.
Solution Approach 2:
The patent introduces metal sulfide catalysts as intermediaries that mediate the depolymerization reaction. These catalysts facilitate the breakdown of plastic polymers into monomers or fuel oil components while their sulfide structure resists coke deactivation. The catalyst acts as a mediator between the plastic feedstock and desired products, enabling continuous operation through regenerative properties.
2Adaptability or versatility
If conventional hydroconversion processes are used, then heavy oil products can be converted, but the processes are not suitable for heterogeneous polymer mixtures and produce catalyst deactivation
Solution Approach 1:
The patent changes the catalyst composition from conventional metals to metal sulfides (MoS2, WS2, WSe2) which exhibit greater stability with heterogeneous polymer mixtures. The sulfide form of the catalyst resists deactivation from contaminants and varying polymer compositions, enabling reliable processing of mixed plastic waste streams while maintaining catalytic activity.
Solution Approach 2:
The patent employs composite catalyst systems combining metal sulfides with support materials. These composite structures provide both the catalytic activity needed for depolymerization and the stability required to handle heterogeneous polymer mixtures. The composite nature of the catalyst allows it to tolerate variations in feedstock composition without deactivation.
3Quantity of substance
If slurry phase hydroconversion is used with molybdenum catalyst, then naphtha cuts can be produced, but inorganic components need to be separated from the reaction effluent
Solution Approach 1:
The patent utilizes phase transitions in the separation process. The reaction effluent undergoes phase separation where naphtha cuts (lighter hydrocarbons) separate from the slurry phase containing catalyst and inorganic components. The metal sulfide catalyst remains in the solid slurry phase while the desired naphtha products are recovered in the liquid or vapor phase, simplifying separation.
Solution Approach 2:
The patent extracts the desired naphtha products from the reaction effluent through phase separation. The inorganic components and catalyst remain in the slurry phase and are left behind, while the naphtha cuts are extracted and recovered. This selective extraction simplifies the separation process compared to conventional methods.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This process increases naphtha yields, concentrates inorganic components, and produces high-quality hydrocarbon products, avoiding catalyst deactivation and enabling the recycling of heterogeneous polymer mixtures, including those sensitive to contamination, thus valorizing plastic waste into usable petrochemical building blocks.
Implementation Method 1
feeding to the hydroconversion section the reactant mixture in slurry phase, a precursor of the catalyst containing Molybdenum
Implementation Method 2
In a slurry reactor the catalyst is dispersed in the reaction medium and uniformly distributed inside the reactor itself
Implementation Method 3
separating the reaction effluent into at least one high-pressure and high-temperature separator in a vapour phase and a slurry phase
Data Source
AI summary
There is a process for the hydroconversion of mixtures of polymers or plastics which comprises the pre-treatment of the mixtures through methods selected from mechanical methods, chemical methods, thermal methods, or combinations thereof forming a pre-treated charge. The pre-treated charge is mixed with a hydrocarbon vacuum residue, optionally pre-heated, to form a reactant mixture. The reactant mixture is fed to a hydroconversion section in slurry phase, together with a catalyst precursor containing Molybdenum, and a stream containing hydrogen, forming a reaction effluent. The effluent is separated into at least one high-pressure and high-temperature separator in a vapour phase and a slurry phase. The separate vapour phase is sent to a gas treatment section with the function of separating a liquid fraction from the gas containing hydrogen and hydrocarbon gases having from 1 to 4 carbon atoms; said liquid fraction comprising naphtha, atmospheric gas oil (AGO), vacuum gas oil (VGO). The slurry phase is then sent to a separation section that has the function of separating the fractions of the Vacuum Gas Oil (VGO), Heavy Vacuum Gas Oil (HVGO), Light Vacuum Gas Oil (LVGO), Atmospheric Gas Oil (AGO), from a stream of heavy organic products which contains asphaltenes, unconverted charge, catalyst and solid formed during the hydroconversion reaction. This stream of heavy organic products is partly recirculated to the hydroconversion section and partly forms a purge stream.