Methanation resisting active carbon ruthenium carrying catalyst for ammonia synthesis with high intensity

Abstract

The present invention discloses one kind of ammonia-synthesizing Ru-carrying active carbon catalyst with high strength and high methanation resistance. The catalyst consists of Ru 3-12 (in weight of the active carbon, the same below); Ba+Ln 3-7 with Ln being RE metal La, Ce, Pr, Nd or Sm and Ba / Ln=1-25; and K 8-20. The catalyst is prepared through extruding the material with inorganic adhesive and is shaped in cylinder of 3-10 mm diameter and 3-20 mm length or ball. It has pressure strength higher than 50 N / cm (cylinder) or 30 N (ball), wear rate less than 0.6 % and methanation resistance 0.35-4 times that of Ru / AC ammonia-synthesizing catalyst.

Description

technical field [0001] The invention relates to a novel ammonia synthesis catalyst technology for ammonia synthesis from hydrogen and nitrogen in the ammonia synthesis industry, specifically, a method for preparing an activated carbon-supported ruthenium ammonia synthesis catalyst with anti-methanation and high mechanical strength. Background technique [0002] The traditional molten iron ammonia synthesis catalyst has been used in the ammonia synthesis industry for more than 90 years. Although iron catalysts have the advantages of low price and good stability, when iron catalysts are used, the ammonia synthesis reaction must be carried out under high temperature and high pressure conditions, and the production process requires harsh equipment, large investment, and high energy consumption. [0003] In recent years, an activated carbon-supported ruthenium-based ammonia synthesis catalyst has been developed and used abroad, which can convert H 2 , N 2 It catalyzes the synth...

AI Technical Summary

Problems solved by technology

However, the activated carbon carrier of activated carbon supported ruthenium-based ammonia synthesis catalyst is easily methanated under the high temperature and hydrogen-containing conditions of ammonia synthesis, so it is very unstable; at the same time, due to the poor mechanical strength of activated carbon itself, such as the average compressive strength of amorphous coconut shell activated carbon It is about 40N, but the wear rate is as high as more than 4%, and its industrial use as a catalyst carrier is more risky. In order to improve the stability of activated carbon against methanation under high temperature and hydrogen-containing conditions, people usually carry out high-temperature graphitization treatment on ordinary activated carbon .PCT patent WO03 / 048045A2 discloses a BET surface area greater than 280m after 2000°C high temperature treatment and redox treatment 2 / g of graphite as carrier, with Ba(NO 3 ) 2 , CsOH+KOH as additives, ruthenium content of 1 ~ 10wt% ammonia synthesis catalyst, compared with the activated carbon as the carrier only after 1500 ℃ treatment and 425 ℃ redox treatment, its anti-methanation ability is about 20 times higher times

[0004] Our practice shows that even the catalyst prepared by using activated carbon that has been graphitized at a high temperature of 1900°C as the ruthenium catalyst carrier, at 15MPa, 450°C, 30000h -1 , under the condition that the hydrogen-nitrogen ratio is 3, the methane content in the reactor outlet gas can still reach 0.0049%, which will seriously affect the long-term use of the catalyst

[0005] Retrieval of relevant materials including Chinese patents shows that there is no high mechanical strength, suitable specific surface and pore structure, ruthenium as the main active agent, and oxides or hydroxides of alkali metals, rare earth metals and alkaline earth metals. Relevant reports on the formulation and preparation method of activated carbon-supported ruthenium-based ammonia synthesis catalysts that are additives, methanation-resistant, and high-mechanical strength