Search

US-20260129720-A1 - CATALYTICALLY ACTIVE HEATING ELEMENTS, PRODUCTION AND USE THEREOF

US20260129720A1US 20260129720 A1US20260129720 A1US 20260129720A1US-20260129720-A1

Abstract

The invention relates to catalytically active heating elements, and to the production and use thereof in the production of hydrogen cyanide (HCN). The problem addressed by the invention is that of providing thermally stable and catalytically active heating elements with which a BMA process can be simultaneously electrically heated and chemically catalysed. In particular, the heating elements should be thermally and mechanically stable in continuous industrial operation and retain their catalytic activity. The heating element according to the invention has a layered structure (A, B, C) formed from (A) silicon carbide (SiC), (B) aluminium nitride (AlN) and (C) platinum (Pt). The silicon carbide (SiC) serves as an electric heating resistor. The platinum (Pt) serves as catalyst. Aluminium nitride (AIN) is arranged as a protective layer between platinum (Pt) and silicon carbide (SiC). It prevents platinum (Pt) and silicon carbide (SiC) from alloying during ongoing operation.

Inventors

  • Ulf BINDERNAGEL
  • Catrin Dorothee BECKER
  • Thomas Müller
  • Martin Köstner

Assignees

  • EVONIK OPERATIONS GMBH

Dates

Publication Date
20260507
Application Date
20230914
Priority Date
20221007

Claims (13)

  1. 1 . A heating element at least comprising: a) a first electrical connection; b) a second electrical connection; c) a solid or hollow core containing silicon carbide, wherein the solid or hollow core electrically connects the first electrical connection at least to the second electrical connection; d) a protective coating applied to the solid or hollow core; e) a catalyst system applied to the protective coating, wherein the catalyst system contains platinum, wherein the protective coating contains aluminum nitride.
  2. 2 . The heating element according to claim 1 , wherein the catalyst system is applied exclusively to the protective coating .
  3. 3 . The heating element according to claim 1 , wherein a volume v 1 of the protective coating and/or a volume v 2 of the catalyst system is smaller than a volume v 0 of the solid or hollow core.
  4. 4 . A process for producing a heating element, the process comprising at least: a) providing a solid or hollow core containing silicon carbide; b) providing a coating composition containing aluminum and nitrogen; c) providing a catalyst system containing platinum; d) coating the solid or hollow core with the coating composition to obtain a protective coating containing aluminum nitride adhering to the solid or hollow core; e) coating the protective coating with the catalyst system so that the catalyst system adheres to the protective coating.
  5. 5 . The process according to claim 4 , wherein the coating composition is a dispersion containing a dispersion medium and aluminum nitride dispersed therein.
  6. 6 . The process according to claim 5 , comprising: spraying the dispersion onto the solid or hollow core and subsequently drying the dispersion.
  7. 7 . The process according to claim 5 , comprising: immersing the solid or hollow core in the dispersion and subsequently drying the solid or hollow core.
  8. 8 . The process according to claim 4 , wherein the coating composition is a system comprising two components, namely a first component containing aluminum and a second component containing nitrogen and wherein the aluminum and the nitrogen are reacted to afford aluminum nitride in presence of the solid or hollow core.
  9. 9 . A process, comprising: employing a heating element according to claim 1 in the production of nitriles.
  10. 10 .- 11 . (canceled)
  11. 12 . A process for producing nitriles, the process comprising: a) providing a reactor containing at least one heating element; b) supplying the reactor with a reactant gas mixture containing at least ammonia and methane, wherein the reactant gas mixture has an oxygen content of less than 2% by volume or wherein the reactant gas mixture is free from oxygen; c) supplying the heating element with electrical current; d) withdrawing a product gas mixture containing at least hydrocyanic acid from the reactor; wherein the provided heating element is a heating element according to claim 1 .
  12. 13 . The process according to claim 12 , wherein the produced nitrile is hydrocyanic acid.
  13. 14 . The process according to claim 12 , comprising: providing heat energy and catalyzing of an endothermic reaction with the heating element.

Description

The invention relates to catalytically active heating elements and to the production and use thereof in hydrocyanic acid production. Hydrocyanic acid (HCN), the simplest nitrile, is an important synthesis unit in organic chemistry. It is traditionally employed in metal extraction and processing. On an industrial scale the production of hydrocyanic acid is usually carried out by the Andrussow process or the BMA process. An introduction to the technology of hydrocyanic acid production may be found in: Gail, E., Gos, S., Kulzer, R., Lorösch, J., Rubo, A., Sauer, M., Kellens, R., Reddy, J., Steier, N. and Hasenpusch, W. (2011). Cyano Compounds, Inorganic. In Ullmann's Encyclopedia of Industrial Chemistry, (Ed.). https://doi.org/10.1002/14356007.a08_159.pub3 In the BMA process (BMA=“Blausäure aus Methan und Ammoniak” [hydrocyanic acid from methane and ammonia]) hydrocyanic acid is produced from methane (CH4) and ammonia (NH3) in a strongly endothermic reaction which requires relatively high reaction temperatures of 1000° C.-1300° C. In contrast to the Andrussow process the BMA process is performed in the absence of oxygen. The energy required in the BMA process is provided in a separate combustion space through combustion of heating gas. Only a portion of the employed heating energy may be utilized for the reaction itself due to the necessary minimum temperatures for the hydrocyanic acid reaction. The necessary use of fossil energy carriers for providing the reaction enthalpy in conjunction with the low energetic yield for the hydrocyanic acid results in significant generation of CO2. As an alternative energy source HCN may be produced with electrical energy instead of with fossil fuels. When using electricity from renewable sources the process is potentially very largely CO2-neutral. An electrically heated BMA process also has further advantages over a BMA process heated with fossil fuel, for example in terms of running costs: By avoiding the entailed energy loss on the fuel gas side due to the high minimum reaction temperature necessary, a better energetic efficiency is to be expected.Since refractory materials for lining the reactor need not be employed, faster startup and shutdown cycles are achieved.A more homogeneous temperature mode makes it possible to achieve higher yields, thus reducing the specific usage amounts of methane and ammonia for hydrocyanic acid production. This is because it is known that homogeneous temperature distribution makes it possible to achieve markedly higher yields coupled with lower byproduct formation. In terms of capital costs too, an electrically heated BMA plant has advantages over a thermally heated plant: The absence of fuel gas and flue gas spaces allows a more compact construction and higher space-time yieldsand cost-effective modular interconnections are likewise possible. Finally, an electrically operated BMA process is more sustainable: The generated hydrogen-containing residual gas may optionally substitute natural gas as heating gas in downstream processes, thus achieving an additional CO2 reduction.The hydrogen in the generated residual gas has a considerably lower CO2 footprint than hydrogen produced from fossil hydrocarbons in the steam reformer and may be used as raw material for further chemical reactions after a potentially required purification. For all these reasons there is an interest in developing a BMA process operated with electrical energy, by which hydrocyanic acid may be produced on an industrial scale. Various concepts for producing HCN in electrically heated reactors are known: Hydrocyanic acid production through the use of electrically heated fixed bed reactors is described, wherein the heating of the catalyst dumped bed may be effected by induction; cf. WO 2017186437 A1. Structured catalyst bodies, so-called monoliths, composed of electrically conductive material as described in DE 10317197A1, WO 2019228798 A1 or WO 2021/063799 A1 are also employed. In the recited publications the reactants are passed through the catalyst-coated channels of an electrically heated structure. Similarly, WO 2022017900 A1 describes catalytically active heating elements produced by additive manufacturing which are to be employed in various endothermic reactions including in hydrocyanic acid production. The heating elements comprise a metallic, electrically conductive core provided with a ceramic coating. A catalytically active layer has in turn been applied to the ceramic coating. In the context of the Andrussow process the catalytically active layer contains Pt, Co or SnCo. However, details about the composition of the ceramic layer in respect of hydrocyanic acid production are lacking. Recited in the context of steam reforming are ceramic layers composed of Al2O3, ZrO2, MgAl2O4, CaAl2O4, to which catalytically active material composed of Ni, Ru, Rh, Ir is applied. A disadvantage of the additively manufactured heating elements is in principle that the choice of mater