Catalytic permeable membrane reactor for producing hydrogen from ammonia-containing tail gas in MOCVDprocess as well as preparation method and application of the catalytic permeable membrane reactor

Abstract

The invention discloses a catalytic permeable membrane reactor for producing hydrogen from ammonia-containing tail gas in an MOCVD process. In the membrane reactor, a porous gamma-aluminum oxide ceramic circular tube containing 5-10% (w / w, similarly hereinafter) of metal palladium is dispersed is used as a support body; an inorganic carbon nano-membrane, which contains 10-30% of cobalt and 5-20% of molybdenum as active components, 1-10% of lanthanum serving as an auxiliary catalytic component and 1-5% of potassium serving as an accelerant, is embedded into pretreated carbon nanotubes (CNTs) and coats the inner wall of an alumina ceramic round tube, has thickness of 10 nm to 1 [mu]m and pore diameter of 0.20 to 10 nm; thus forming the catalytic permeable membrane reactor which simultaneously has catalytic activity and separation selectivity. Ammonia-containing tail gas in the MOCVD process is pretreated and then enters a membrane reactor; at the reaction temperature of 400-600 DEG C, an ammonia thermal cracking catalytic reaction is performed under the reaction pressure of 2.0-5.0 MPa; and hydrogen-rich gas generated by the reaction is subjected to adsorption refining deamination,pressure swing adsorption purification and metal getter purification to obtain a hydrogen product with the purity of more than 6-7 N, and the hydrogen product is returned to the MOCVD process to be recycled, thereby filling the blank for green and circular economy development of the LED industry.

Description

technical field [0001] The invention belongs to ammonia-containing (NH 3 ) The field of hydrogen preparation technology for comprehensive utilization of waste gas, in particular to a catalytic permeable membrane reactor and its application for hydrogen production from tail gas containing ammonia by MOCVD (metal oxide chemical vapor deposition). Background technique [0002] MOCVD (Metal Oxide Chemical Vapor Deposition) process (equipment) is a modern method and means for the research and production of compound semiconductor materials, especially as a method and equipment for the industrial production of new light-emitting materials-light-emitting diodes (LEDs). The main methods and means of optoelectronic devices and microwave device materials, in addition to LEDs, also include lasers, detectors, high-efficiency solar cells, photocathode, etc., which are indispensable methods and equipment for the optoelectronics industry, including typical LED GaN For the production of epi...

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Problems solved by technology

[0005] However, the catalysts and fixed-bed shell-and-tube reactors used in the traditional catalytic thermal cracking of ammonia for hydrogen production face the following problems: First, the ammonia gas or liquid ammonia raw materials used are basically pure ammonia

Since there are a large amount of nitrogen and hydrogen in the MOCVD epitaxy tail gas besides ammonia, NH 3 The corresponding concentration or partial pressure is low and the partial pressure of nitrogen and hydrogen is high. Therefore, the conversion rate of catalytic decomposition of ammonia to hydrogen production from MOCVD epitaxial tail gas is very low by direct use of traditional ammonia decomposition catalysts, and the selectivity of hydrogen production is relatively poor. Catalyst Neither the processing capacity nor the space velocity of the decomposition reaction can reach the production scale and technical indicators of hydrogen production from pure ammonia decomposition; During the reaction process, the raw material gas and the reaction gas need to be circulated to make the ammonia decompose completely, the energy consumption increases, and the hydrogen gas cannot be removed in time in the reaction system, and the hydrogen concentration accumulates in the cycle, which makes the hydrogen partial pressure continue to increase, further suppressing the Decomposition of ammonia; third, in the mixed gas generated by the reaction, in order to avoid the amount of circulation, it is necessary to remove the reactor in time after the reaction reaches a certain period of time, and there are still a large amount of nitrogen and a small amount of undecomposed ammonia in the reaction gas The existence of gas increases the load and cost of subsequent PSA hydrogen extraction; fourth, the traditional pure ammonia decomposition hydrogen production process mostly obtains higher conversion rate and hydrogen yield at higher temperature, and the general reaction temperature is 600- 800°C, relatively high energy consumption

Therefore, for the MOCVD epitaxial tail gas with low ammonia concentration and high hydrogen concentration, the catalytic pyrolysis reaction should be carried out at a lower temperature, so that the ammonia conversion rate and hydrogen selectivity are high, or the space velocity on the unit catalyst can reach at least The processing scale and technical indicators of pure ammonia decomposition hydrogen production are very difficult; fifth, if the ammonia decomposition conversion rate in the MOCVD epitaxy tail gas is low, or the obtained hydrogen cannot be removed in time, the undecomposed ammonia content will be in the reaction gas If it is too high, the cost of tail gas separation and extraction of hydrogen or hydrogen reuse will increase, and traditional methods such as washing ammonia with water have to be used to purify and remove it, resulting in poor technical and economic benefits

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