Search

CN-121988360-A - Catalyst with silicon carbide as carrier and preparation method and application thereof

CN121988360ACN 121988360 ACN121988360 ACN 121988360ACN-121988360-A

Abstract

The invention belongs to the technical field of catalysts, and discloses a catalyst taking silicon carbide as a carrier, a preparation method and application thereof, wherein the catalyst contains a silicon carbide carrier and active components uniformly loaded on the silicon carbide carrier, and the active components are nano La 2 O 3 or nano Ni-La 2 O 3 . The preparation method of the catalyst comprises the steps of (a) dispersing nano La 2 O 3 or nano Ni-La 2 O 3 in a solvent to form a suspension, optionally mixing 3-6wt% of polyvinyl alcohol aqueous solution with the suspension to prepare an impregnating solution, and (b) impregnating a silicon carbide carrier by using the impregnating solution, and then carrying out heat treatment to obtain the catalyst. The catalyst of the invention can avoid the formation of local hot spots on the catalytic bed layer and reduce side reactions or carbon deposition.

Inventors

  • DING CHENGZHE
  • LI WEI
  • BAI JIE
  • WU JIEHUA
  • WANG XUE
  • FENG JING

Assignees

  • 中国石油化工股份有限公司
  • 中石化(北京)化工研究院有限公司

Dates

Publication Date
20260508
Application Date
20241107

Claims (10)

  1. 1. The catalyst taking silicon carbide as a carrier is characterized by comprising a silicon carbide carrier and active components uniformly loaded on the silicon carbide carrier, wherein the active components are nano La 2 O 3 or nano Ni-La 2 O 3 .
  2. 2. The silicon carbide supported catalyst according to claim 1, wherein the silicon carbide support has a particle size of 50 to 500 μm; The nanometer La 2 O 3 is a mixture of olive-shaped particles and spherical particles, wherein the length of the short axis of the olive-shaped particles is 40-80nm, the length of the long axis is 100-200nm, and the diameter of the spherical particles is 50-90nm.
  3. 3. The silicon carbide supported catalyst of claim 1, wherein the nano La 2 O 3 or nano Ni-La 2 O 3 loading is 10-30% based on the weight of the catalyst.
  4. 4. A silicon carbide supported catalyst according to any of claims 1 to 3 wherein nano Ni-La 2 O 3 is nano La 2 O 3 supported Ni, the Ni loading being 5-15%, preferably 8-12% based on the weight of Ni-La 2 O 3 .
  5. 5. The method for preparing a silicon carbide supported catalyst according to any one of claims 1 to 4, comprising the steps of: (a) Dispersing nano La 2 O 3 or nano Ni-La 2 O 3 in a solvent to form a suspension, optionally mixing 3-6wt% of polyvinyl alcohol aqueous solution with the suspension to prepare an impregnating solution; (b) The silicon carbide carrier is impregnated with the impregnating solution, and then heat-treated, to obtain the catalyst.
  6. 6. The method for preparing a silicon carbide supported catalyst according to claim 5, wherein the solvent is at least one selected from the group consisting of water, acetone, ethanol, isopropanol, tetrahydrofuran and hexane; preferably, the dispersion uses ultrasonic dispersion for 10-60 minutes; Preferably, the aqueous polyvinyl alcohol solution is mixed with the suspension in a volume ratio of 0:2 to 1:2.
  7. 7. The method for preparing a silicon carbide supported catalyst according to claim 5, wherein the impregnation is performed by an over-volume impregnation method or an isovolumetric impregnation method; Preferably, the excess volume impregnation method comprises immersing the silicon carbide carrier in the solution, stirring for 1-6 hours, and then adopting rotary evaporation drying at 40-160rpm; Preferably, the isovolumetric impregnation method adopts a mode of adding the impregnating solution into the silicon carbide carrier in a divided manner, more preferably, the silicon carbide carrier is placed on filter paper, and the impregnating solution is added dropwise onto the silicon carbide carrier under baking of an infrared lamp.
  8. 8. The method for preparing a silicon carbide supported catalyst according to claim 5, wherein the heat treatment is a heat treatment in an oven or a muffle furnace at 100-600 ℃ for 2-16 hours.
  9. 9. Use of the catalyst taking silicon carbide as a carrier in the reaction of preparing ethane and ethylene by oxidative coupling of methane, wherein the active component of the catalyst is nano La 2 O 3 ; Preferably, the reaction conditions comprise a volume space velocity of the raw material gas of 50000-200000h- 1 , a reaction temperature of 650-750 ℃, a volume flow ratio of methane to oxygen of 4-7:1, and the reaction is carried out under normal pressure.
  10. 10. Use of the catalyst taking silicon carbide as a carrier in the reaction of preparing synthesis gas by methane dry reforming according to any one of claims 1-4, wherein the active component of the catalyst is nano Ni-La 2 O 3 ; preferably, the reaction conditions include a space velocity of the feed gas of 30000-100000h -1 , a reaction temperature of 700-800 ℃, and a reduction of the catalyst with hydrogen at 550-700 ℃ for 0.5-2 hours before the reaction starts.

Description

Catalyst with silicon carbide as carrier and preparation method and application thereof Technical Field The invention belongs to the technical field of catalysts, and particularly relates to a catalyst taking silicon carbide as a carrier, a preparation method of the catalyst and application of the catalyst. Background Catalytic conversion of methane as the major component of natural gas to more valuable chemicals and fuels is a challenge for the 21 st century. As chemical raw materials, the utilization way of methane mainly has two directions, namely, the methane is indirectly utilized to produce synthesis gas and then is further converted into alcohols, and the methane is directly converted to obtain high-value chemical products such as ethylene. The method for preparing ethane and ethylene by Oxidative Coupling of Methane (OCM) has obvious advantages in the aspect of atomic utilization rate according to a reaction equation (1), and has wide application prospect in the future. Since Keller and Bhasin reported OCM for the first time in 1982, the related studies have never been stopped, however the catalyst performance has not yet reached the standards for industrial use. Because of the chemical inertness of methane, high temperatures (600-900 ℃) are required to activate methane for OCM reactions, and under these conditions methane and C 2 hydrocarbon products are susceptible to deep oxidation to carbon dioxide, reducing catalyst selectivity. Meanwhile, OCM reaction is a strong exothermic reaction, the local temperature of the bed layer in the reaction process can be 150-300 ℃ higher than the external temperature (CATALYSIS TODAY,2000,63,165-174), and the hot spot of the bed layer can easily lead to the deactivation of the catalyst, and the excessive temperature can further aggravate the deep oxidation. Mn-Na 2WO4/SiO2 catalyst is reported to have higher OCM activity, but the reaction temperature is higher (750-900 ℃), and SiO 2 has poorer heat conduction performance, which is easy to cause the temperature of a catalytic bed layer to fly. While SiO 2 is used as a catalyst carrier, the W-O-Si bond is also an active site, so that the SiO 2 carrier cannot be easily replaced. Lanthanum-based metal oxides (La 2O2CO3、La2O3, etc.) can catalyze OCM reactions at relatively mild conditions of less than 700 ℃ compared to sodium tungsten manganese systems, which conditions are more economical and safer for industrial scale-up of OCM. However, lanthanum-based metal oxides also have the problem of low OCM activity, high oxygen concentration (low alkoxide ratio), and excessive oxidation at high temperatures. To ensure hydrocarbon selectivity in OCM, the alkoxide ratio is typically controlled to be around 5-7, which greatly limits methane conversion. The high-thermal-conductivity material is used as a carrier of active components such as La 2O3 and the like, and is an effective means for controlling the temperature of a reaction bed layer and relieving deep oxidation. Meanwhile, the OCM reaction outlet gas contains a certain concentration of carbon dioxide and a large amount of methane recycle gas except for C 2 and above, and the carbon dioxide and methane can be converted into synthesis gas by using the dry reforming reaction (DRM) of methane, so as to reduce carbon emission. Because of the characteristic of strong heat absorption of DRM, the material with high heat conductivity is also of great significance as a carrier for controlling the temperature difference of a bed layer to avoid carbon deposition. Meanwhile, the DRM active component is often Ni impregnated on a basic oxide (La 2O3, etc.), so OCM has a certain similarity with DRM on a catalyst. Research on the high-heat-conductivity supported OCM catalyst also has important reference value for DRM. Disclosure of Invention Based on the above circumstances, the present invention aims to provide a catalyst using silicon carbide as a carrier, a preparation method and application thereof, the catalyst of the present invention uses silicon carbide as a carrier, the silicon carbide has high thermal conductivity and chemical stability, can promote the removal of hot spots in the bed, effectively control the temperature of the reaction bed, and reduce the occurrence of side reactions or carbon deposition. The first aspect of the invention provides a catalyst taking silicon carbide as a carrier, which comprises the silicon carbide carrier and active components uniformly loaded on the silicon carbide carrier, wherein the active components are nano La 2O3 or nano Ni-La 2O3. The second aspect of the present invention provides a method for preparing the catalyst using silicon carbide as a carrier, which comprises the following steps: (a) Dispersing nano La 2O3 or nano Ni-La 2O3 in a solvent to form a suspension, optionally mixing 3-6wt% of polyvinyl alcohol aqueous solution with the suspension to prepare an impregnating solution; (b) The silicon carbide carrier is impregnated wi