Search

DE-102024133043-A1 - Enrichment of ethene in olefin mixtures by heterogeneously catalyzed, selective co-oligomerization of C3+ olefins

DE102024133043A1DE 102024133043 A1DE102024133043 A1DE 102024133043A1DE-102024133043-A1

Abstract

The present invention relates to a process for the enrichment of ethene in olefin mixtures with simultaneous co-oligomerization of C 3+ olefins in a fixed-bed reactor under mild reaction conditions using a heterogeneous amorphous silicon oxide-aluminum oxide catalyst having a mild acidity.

Inventors

  • Constantin Fuchs
  • Ulrich Arnold
  • Jörg Sauer

Assignees

  • Karlsruher Institut für Technologie, Körperschaft des öffentlichen Rechts

Dates

Publication Date
20260513
Application Date
20241112

Claims (15)

  1. A process for the enrichment of ethene and for the selective co-oligomerization of C³⁺ olefins in olefin mixtures comprising the following steps: A) Preparing a calcined amorphous silicon dioxide-aluminum dioxide catalyst with a specific surface area of 280–550 m² /g, a pore volume of 0.5–2 ml/g, a pore diameter of 5–15 nm, a particle size of 250–500 µm, and a SiO₂ / Al₂O₃ ratio in the range of 20:80 to 70:30 wt %; B) Inerting a fixed-bed reactor by heating at 250–350 °C and passing an inert gas through the reactor; C) Cooling the reactor to 110–160 °C; D) Introducing a gaseous or liquid olefin mixture into a first reactor section of the baked-out fixed-bed reactor under inert gas; E) Optionally, vaporizing the olefin mixture from step D) in the first reactor section; F) Introducing the olefin-gas mixture into a second reactor section containing an inert material with a particle size of 250–500 µm and preheating the olefin-gas mixture to 110–160 °C; G) Passing the olefin-gas mixture into a reaction zone heated to 110–160 °C containing a mixture of the silicon oxide-aluminum oxide catalyst from step A) and an inert material with a particle size of 250–500 µm; H) Setting a total pressure of 40 bar in the reaction zone with an olefin partial pressure of 28 - 38 bar and a corresponding inert gas partial pressure of 2 - 12 bar; I) Dwelling the olefin-gas mixture in the reaction zone; J) Decompressing the reaction products to ambient pressure in a plant area downstream of the reactor, whereby the oligomers with chain lengths from C 5 and the gaseous olefins containing the enriched ethene fraction are condensed out and separated in the gas phase.
  2. Procedure according to Claim 1 , wherein two functionally identical fixed-bed reactors are connected in series and the method is carried out according to Claim 1 also carried out in the second fixed-bed reactor downstream of the first fixed-bed reactor, wherein the short-chain product gas mixture from the first fixed-bed reactor is fed into the second fixed-bed reactor after the separation of ethene, and the olefin partial pressure in the second fixed-bed reactor is set to 28.4 bar and the inert gas partial pressure to 11.6 bar in step H).
  3. Procedure according to Claim 1 , wherein three functionally identical fixed-bed reactors are connected in series and the process is carried out according to Claim 1 This process is also carried out in the fixed-bed reactors downstream of the first fixed-bed reactor, wherein the short-chain product gas mixture from the upstream fixed-bed reactor is fed into the downstream fixed-bed reactor after the separation of ethene, and the olefin partial pressure in the second fixed-bed reactor downstream of the first reactor is 28.4 bar and the inert gas partial pressure is 11.6 bar in step H), and the olefin partial pressure in the fixed-bed reactor downstream of the second fixed-bed reactor is set to 17.8 bar and the inert gas partial pressure to 22.2 bar in step H).
  4. Method according to any of the preceding claims, wherein the inert material in steps F) and G) is silicon carbide, quartz glass, α-aluminum oxide or a technical ceramic.
  5. Method according to one of the preceding claims, wherein the mixture of the silicon oxide-aluminum oxide catalyst and the inert material in step G) is present in a volume ratio of catalyst to inert material of 0.1 - 0.2.
  6. Method according to any of the preceding claims, wherein the catalyst is in the form of pellets or extrudates.
  7. Method according to one of the preceding claims, wherein a temperature of 120 °C is set in steps C), F) and G).
  8. Method according to one of the preceding claims, wherein a weight-related hourly space velocity (WHSV) of 2 - 8 h -1 is set in the reactor.
  9. Method according to one of the preceding claims, wherein the reactant-olefin mixture contains ethene, propene and butene in the stated order in a molar ratio of 2:2:1.
  10. Procedure according to Claim 9 , where the WHSV is 2 h -1 and the olefin partial pressure in step H) is 36 bar.
  11. Method according to one of the preceding claims, wherein at least a partial stream of the product gas mixture is diverted to an online-connected gas chromatograph (11) for the continuous determination of the content of gaseous olefins.
  12. Method according to one of the preceding claims, characterized in that at least a part of the liquid product phase is analyzed for the continuous determination of the C 5+ olefin content (oligomers with chain lengths from C 5 ) using an external downstream gas chromatograph.
  13. Method according to one of the preceding claims, wherein the product gas enriched with ethene is purified after separation by molecular sieves, membranes or by means of absorption columns.
  14. Method according to one of the preceding claims, wherein the liquid product phase is hydrogenated after separation from the product gas mixture.
  15. Use according to the procedure Claim 14 produced paraffinic highly branched hydrocarbons for the production of blend components in gasoline or kerosene mixtures.

Description

The present invention relates to a process for enriching ethene in olefin mixtures by means of heterogeneously catalyzed, selective co-oligomerization of C 3+ olefins. Short-chain olefins with carbon chain lengths in the C2-4 range are important building blocks of the chemical industry and have a broad and steadily growing range of applications. For example, ethene and propene are indispensable for the plastics industry. Furthermore, disinfectants, insulating materials, or surfactants for detergents and cleaning agents can be produced from derivatives such as ethylene oxide. On an industrial scale, olefins are produced in refineries by steam cracking fossil naphtha. Olefins can also be produced via methanol or dimethyl ether (DME) using the methanol-to-olefins (MTO) or DME-to-olefins (DTO) processes, respectively. For further processing of the olefins, the olefin mixture must be separated. Currently, a highly complex cryogenic distillation process is used for this purpose. The origin of the olefin mixture, whether fossil or from renewable sources, is irrelevant. The required process conditions for the distillative separation of the olefins involve several process steps with varying temperature and pressure requirements. Furthermore, the material and equipment costs are enormous, requiring up to 200 trays per distillation column, resulting in high investment and operating costs for the entire process. In the EP0683146A1 The separation of ethene from an olefin mixture is carried out by cryogenic distillation at temperatures as low as -43 °C and pressures as high as 36 bar. These conditions are achieved through multi-stage compression processes followed by cooling. While higher olefins from C3 upwards condense under these conditions, ethene remains gaseous and can therefore be separated using rectification columns with column heights of up to 50 m. This olefin separation process is extremely energy-intensive, particularly the provision of the necessary cooling and pressure. Another possibility for olefin separation is the use of adsorptive methods, e.g., using crystalline molecular sieves or metal-organic frameworks. As, for example, in the US6200366B1 As described, the separation of molecules of different sizes is possible through the targeted adjustment of the pore diameters of zeolites. In the US6517611B1 For the separation of ethene or propene from paraffins, a crystalline titanium silicate molecular sieve with adjustable pore diameters in the range of 0.3 to 0.4 nm is used. Adsorptive processes, however, typically exhibit lower capacities and selectivities. Furthermore, the required pressure fluctuations are demanding in terms of equipment and energy consumption, resulting in high costs for plant technology and ongoing operation. In addition, continuous operation leads to a reduction in the separation efficiency of the adsorbents, for example, due to pore blockage, necessitating material regeneration. Alternatively, research is being conducted in the field of membrane technology on separation processes. Membranes are used in the separation of olefins and paraffins in the form of facilitated transport membranes (FTMs), whereby the transport of the olefins takes place via carrier molecules that react with the olefins. Such a process is used in the EP1552875A1 described. Membranes are not yet sufficiently developed for large-scale industrial applications of this kind. Their production is complex, as the underlying materials must be adapted to the requirements, e.g., by modification with metals or porous structural elements. Furthermore, blockages can occur, leading to reduced separation efficiency. To separate substances of high purity, low permeability is necessary, which represents another weakness of membranes. This could be demonstrated in the US5670051A The introduction of metal-doped transport membranes improved performance; however, this reduced long-term stability by deactivating the active components (mostly silver or copper) on the membrane, leading to performance losses. Finally, absorptive separation processes should also be mentioned. In the US4479812A A rather complex absorptive process is described in which higher olefins from C3 upwards are washed out in a large-volume absorption column, yielding an ethene-rich gas stream. Higher hydrocarbons from C6 upwards are used as solvents. The required gas-liquid The ratio limits the throughput and affects the dimensions of the separation process. Furthermore, the permissible proportions of ethene and higher olefins in the input stream are regulated. In absorptive processes, the solvents must be regenerated, e.g., by degassing through temperature increase or pressure changes. An energy- and cost-efficient method for the enrichment and separation of ethene from any olefin mixtures with simultaneous selective co-oligomerization of C 3+ olefins without high equipment costs has not yet been described. The present invention is therefore based on the objecti