A method and system for producing light olefins from oxygen-containing compounds

Abstract

The invention discloses a method and a system for preparing low-carbon olefin from an oxygenated compound. The method comprises steps as follows: a, a raw material comprising the oxygenated compound is sent to a reactor to be contacted with a mixed catalyst from a catalyst tank, a dehydration and olefin preparation reaction is performed, and oil gas containing rich low-carbon olefin and a spent catalyst are produced; b, the spent catalyst is led out of the reactor and conveyed to the catalyst tank to be mixed with a regenerated catalyst from a regenerator, and the mixed catalyst is obtained; c, one part of the mixed catalyst obtained in the step b is conveyed to the reactor to be contacted with the raw material comprising the oxygenated compound for a dehydration and olefin preparation reaction, the other part of the mixed catalyst obtained in the step b is conveyed to the regenerator to be subjected to coke-burning regeneration in an atmosphere containing oxygen, and the regenerated catalyst and regenerated flue gas are obtained through separation; d, the regenerated catalyst obtained in the step c is conveyed to the catalyst tank. According to the method and the system, the required catalyst with carbon deposits can be provided for the reaction for preparing the low-carbon olefin from the oxygenated compound.

Description

technical field [0001] The present invention relates to a method and system for preparing light olefins from oxygen-containing compounds. Background technique [0002] Low carbon olefins (C 2 -C 4 Olefins) as basic organic chemical raw materials play a pivotal role in modern petroleum and chemical industries, especially ethylene and propylene. The methods for preparing low-carbon olefins can be roughly divided into two categories, namely traditional petroleum routes and emerging non-petroleum routes. The traditional methods of producing light olefins from petroleum are mainly steam cracking and catalytic cracking processes. Since the 10s of the 20th century, countries around the world have been devoting themselves to the research and development of routes to produce low-carbon olefins from non-petroleum resources, and some progress has been made. [0003] At present, catalysts for producing light olefins from oxygenates generally contain molecular sieves such as ZSM-5 an...

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Problems solved by technology

However, due to the slow heat transfer of the fixed-bed reactor, the reaction of methanol to light olefins is a strong exothermic reaction, which is prone to hot spots, causing damage to the device

[0005] Chinese patent CN101318868A discloses a method and device for generating low-carbon olefins from oxygen-containing compounds, which solves the problem that the reactor temperature cannot be flexibly controlled in the prior art

[0006] Chinese patent CN101270020A discloses a method for producing low-carbon olefins from methanol, which mainly solves the problem of low selectivity of target products in the process of producing low-carbon olefins from methanol

[0009] Chinese patent CN101544529A discloses a pretreatment method and equipment for reaction gas produced by oxygenate-to-olefins process to solve the shortcomings of high temperature and small amount of catalyst in the prior art

The dense-phase fluidized bed reactor belongs to the category of bubbling bed and turbulent bed, and its superficial linear velocity is generally 0.2-1.5m / s, and its space velocity is 2-10h -1 , so the reaction residence time is generally relatively long. Due to the low linear velocity of the dense phase fluidized bed reactor, there is often back mixing, which affects product distribution and quality. On the other hand, the diameter of the reactor is relatively large

It is generally believed that the reaction of oxygen-containing compounds to produce low-carbon olefins is a reaction in which the number of molecules increases, and low reaction pressure is conducive to the direction of chemical equilibrium to produce low-carbon olefins. Considering engineering factors, domestic and foreign MTO technologies still use similar catalytic cracking processes Process, the reactor adopts a dense-phase fluidized bed reactor, and the reaction pressure is similar to that of the catalytic cracking process, that is, 0.1-0.3Mpa (gauge pressure), but the problem is that the size of the reactor is too large

For example, because the existing MTO unit adopts a cyclone separator similar to that of catalytic cracking, the natural loss of the catalyst during the production process is unavoidable, especially when the catalyst fine powder with a particle size of ≦20 μm increases, which will affect the follow-up The product separation has adverse effects, and it is also unfavorable to the reuse of the catalyst

In addition, the generated olefins stay in the reactor for a long time, and the hydrogen transfer reaction increases, which is also very unfavorable for the production of low-carbon olefins

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