DE-102024132817-A1 - Process for the selective dehydrocyclization and aromatization of hydrocarbons in the SAF range to aromatic compounds with the same total carbon number

Abstract

The present invention relates to a process for the selective dehydrocyclization and aromatization of linear or branched hydrocarbons in the SAF range to aromatics in the SAF range.

Inventors

• Florent Jules Dubray
• Jeroen Van Bokhoven
• Jorge A. Gonzales

Assignees

• METAFUELS AG
• PAUL SCHERRER INSTITUT

Dates

Publication Date

20260513

Application Date

20241111

Claims (15)

1. A process for the selective dehydrocyclization and aromatization of linear or branched hydrocarbons in the SAF range to aromatics in the SAF range, wherein the hydrocarbons comprise alkanes, olefins, or mixtures thereof, wherein the hydrocarbons have a number of C _E of carbon atoms, wherein E = 8–18, preferably E = 9–17, more preferably E = 10–16, wherein the aromatics have a number of C_P of carbon atoms, wherein P = 8–18, more preferably P = 9–17, more preferably P = 10–16, and wherein the dehydrocyclization and aromatization are catalyzed by the use of a supported metal catalyst comprising: a support and a metal active for the hydrogenation or dehydrogenation of hydrocarbons, which is loaded onto the support.
2. Procedure according to Claim 1 , wherein the dehydrocyclization and aromatization are carried out at a reaction temperature of 400 °C to 600 °C, preferably 450 °C to 550 °C, and at a pressure of 0.1-10 bar, preferably between 1-3 bar, more preferably at atmospheric pressure.
3. Procedure according to Claim 1 or 2 , whereby the carrier is not angry.
4. Procedure according to one of the Claims 1 until 3 , wherein the support is mesoporous, microporous or non-porous, preferably mesoporous.
5. Procedure according to one of the Claims 1 until 4 , wherein the support is selected from SiO 2 , Al 2 O 3 , M(AlO 2 )(SiO 2 ) x (H 2 O) y , CeO 2 , TiO 2 , SBA-15, MCM-42 or ZSM-5 and the support is preferably Al 2 O 3 .
6. Procedure according to one of the Claims 1 until 5 , wherein the carrier is neutralized with a neutralizing agent before the metal loading.
7. Procedure according to one of the Claims 1 until 6 , wherein the metal is selected from Pt, Re, Pd, Ni, Ir, Cu, Cr, Te, V, Mo or W and it is preferably Pt.
8. Procedure according to one of the Claims 1 until 7 , wherein the metal is loaded onto the carrier by dry impregnation or co-precipitation, preferably by co-precipitation.
9. Procedure according to one of the Claims 1 until 8 , wherein the metal that is loaded onto the support has a particle size of 0.5 to 15.0 nm, preferably 0.5 to 5.0 nm.
10. Procedure according to one of the Claims 1 until 9 , wherein the metal is preferably strongly anchored to the support.
11. Procedure according to one of the Claims 1 until 10 , wherein the catalyst has a metal loading per mass of the catalyst of 0.1 to 25 wt.%, preferably 0.5 to 10 wt.%, more preferably 0.5 to 5 wt.%.
12. Procedure according to one of the Claims 1 until 5 or 7 until 11 , wherein the catalyst is neutralized with a neutralizing agent after the metal loading onto the support and before the catalyst is used for dehydrocyclization and aromatization.
13. Procedure according to one of the Claims 1 until 12 , wherein the catalyst is reduced prior to its use for dehydrocyclization and aromatization.
14. Procedure according to Claim 13 , wherein the catalyst is reduced by molecular hydrogen at a temperature of 300 °C or below.
15. Procedure according to one of the Claims 1 until 14 , wherein the catalyst is regenerated after its use for dehydrocyclization and aromatization by the following steps: (a) burning off coke, (b) oxidation, (c) removal of water and (d) reduction.

Description

The present invention relates to a process for the selective dehydrocyclization and aromatization of linear or branched hydrocarbons in the SAF range to aromatics in the SAF range. The transport sector is facing increasing demands for the use of sustainable fuels. In the aviation industry, these are referred to as sustainable aviation fuels (SAF). New solutions are needed to achieve the corresponding goals. Currently, the industry mandates aromatic compounds, or aromatics for short, as a compulsory component of aviation fuel because they possess seal-expanding properties necessary for the proper functioning of jet engine seals. However, the combustion of aromatic compounds has been identified as a major cause of aircraft contrails and their significant negative contribution to climate change. Therefore, one of the industry's longer-term goals is to replace these aromatic compounds in the SAF (Standard Air Fuel) range with cycloparaffins, which are cyclic alkanes with a total number of carbon atoms per molecule (carbon number) generally in the range of Cs to C18 . The cycloparaffins intended to replace the aromatics are expected to exhibit comparable seal-expanding properties, while their combustion is much cleaner than that of aromatics. In general, cycloparaffins can be obtained from linear alkanes, also called paraffins, and alkenes, also called olefins in petrochemistry, by thermochemical conversion. This conversion involves successive dehydrogenation and ring-closing reaction steps, which can be catalyzed by metals that are active in the hydrogenation and/or dehydrogenation of hydrocarbons, or by acidic sites. One possible route for the production of cycloparaffins from linear olefins and/or alkanes involves the dehydrocyclization of linear (or branched) olefins and/or alkanes, which (usually) leads to cyclic aromatic compounds, followed by hydrogenation of the aromatic compounds to obtain cycloparaffins. The present invention focuses on the first of these two reaction steps. Dehydrocyclization is defined as the process of closing the carbon ring in combination with dehydrogenation. The formation of aromatic compounds according to the first reaction step described above involves further dehydrogenation steps that enable complete conjugation of the resulting double bonds. Since the invention aims at the production of aromatic compounds, dehydrocyclization and aromatization are usually referred to together in the context of this application. Current dehydrocyclization technologies focus on the production of benzene, toluene, and xylene (BTX) for applications in fuels and the petrochemical industry. The carbon number of these products ranges from C6 for benzene, through C7 for toluene, to C8 for xylene. Known dehydrocyclization processes for BTX formation are carried out using a catalytic reforming unit. The dehydrocyclization and aromatization of linear or branched olefins and/or alkanes to BTX products can be carried out by using catalytically active acid sites for the equilibrium production of BTX products or by using metals that are catalytically active in hydrogenation or dehydrogenation reactions for the selective dehydrocyclization and aromatization reaction. The combined use of catalytically active acid sites and metal sites (bifunctional catalysis) is also known from the prior art. For example, the scientific article "Dehydrocyclization of Alkanes via Zeolite-Supported Metal Catalysts: Monofunctional or Bifunctional Route" by Mériaudeau & Naccache deals with the aromatization of BTX products. The conversion of n-hexane (C 6 ), n-heptane (C 7 ) and n-octane (C 8 ) via supported platinum (Pt) catalysts, in particular via Pt-zeolite catalysts, is discussed in detail. The aromatization of lighter hydrocarbons with a carbon number of C2 to C5 is also well known in the art. Commercially available aromatization technologies exist, for example, Mobil's M2-Forming, BP-UOP's Cyclar, and IFP-Saluted's Aromatization. However, dehydrocyclization and aromatization of hydrocarbons with carbon chain lengths exceeding a carbon number of C8 have not yet been reported or demonstrated with satisfactory results. A total carbon number in the range of C8 to C18 , preferably C9 to C17 , and more preferably C10 to C16 , is However, this is necessary to achieve the chemical and physical properties prescribed for aviation fuel – in particular the boiling point distribution. Therefore, only aromatics in the SAF range, i.e., with a carbon number between C 8 and C 18 , preferably between C 9 and C 17 , and more preferably between C 10 and C 16 , are of interest for direct use as a component of SAF or, preferably, for the production of cycloalkanes that replace the aromatics in SAF, thus resulting in an aromatic-free aviation fuel. The object of the present invention is therefore to provide a process for the selective dehydrocyclization and aromatization of linear or branched hydrocarbons in the SAF range (i.e., with a number o