A two-stage preparation process for propylene

Abstract

The invention discloses two-section preparation process of propylene. Methanol and refinery carbon teterolefin are used as raw materials, water is used as a diluent, and a two-section fixed bed reactor is adopted for preparation. Catalyst in the first section of the fixed bed reactor contains 50%-85% ZSM-5 molecular sieve, and catalyst in the second section of the fixed bed reactor is magnesium element modified ZSM-5 molecular sieve catalyst. By means of the two-section preparation process of the propylene, water amount in the diluent is reduced, operation temperature is reduced, propylene selectivity and P / E ratio are effectively improved, conversion rate of the raw material methanol can reach as high as 100%, conversion rate of the refinery carbon teterolefin can reach above 85%, and one-way selectivity of propylene can reach as high as 50%.

Description

technical field

[0001] The invention relates to a two-stage preparation process of propylene, in particular to a process for preparing propylene by coupling methanol with refinery C4-olefins. Background technique

[0002] In the current prior art, there are mainly two processes for preparing propylene from methanol: MTO technology and MTP technology. Compared with MTO technology, MTP technology uses a fixed-bed reactor, which is easy to scale up, has low risk, and has great confidence in industrialization. At the same time, the by-product market is gasoline, liquefied petroleum gas and fuel gas with a large capacity, which has high economic benefits . However, the preparation of low-carbon olefins by methanol is a strong exothermic reaction, and a large amount of heat of reaction is generated in the process of generating low-carbon olefins. The heat of reaction is difficult to remove, and a large amount of water is required as a diluent, resulting in high operating costs; ...

Examples

Embodiment 1

[0025] A two-stage preparation process for propylene, using methanol and refinery carbon tetraolefins as raw materials, water as a diluent, prepared in a two-stage fixed-bed reactor; the catalyst in the first-stage fixed-bed reactor contains mass fraction It is the catalyst of 70% ZSM-5 molecular sieve, and the catalyst in the second stage fixed bed reactor is the ZSM-5 molecular sieve catalyst modified by magnesium element, containing mass fraction is 70% ZSM-5 molecular sieve, mass fraction is the magnesium of 0.1% element, and the magnesium element is derived from magnesium oxide. Among them, the silicon-aluminum molar ratio of the ZSM-5 molecular sieve is 260, and the grain size is 1.5 μm.

[0026] Specific steps include:

[0027] (1) The mixture of methanol and water is reacted through the first fixed-bed reactor equipped with a catalyst to obtain a reaction mixture flow of dimethyl ether, methanol and water;

[0028] (2) The reaction mixture flow obtained in step (1) i...

Embodiment 2

[0031] A two-stage preparation process for propylene. The catalyst in the second-stage fixed-bed reactor is a magnesium-modified ZSM-5 molecular sieve catalyst containing 2% magnesium by mass fraction. Other process parameters and steps are as described in the examples 1 described.

Embodiment 3

[0033] A two-stage preparation process for propylene. The catalyst in the second-stage fixed-bed reactor is a magnesium-modified ZSM-5 molecular sieve catalyst containing 4% magnesium by mass fraction. Other process parameters and steps are as described in the examples 1 described.

technical field

[0001] The invention relates to a two-stage preparation process of propylene, in particular to a process for preparing propylene by coupling methanol with refinery C4-olefins. Background technique

[0002] In the current prior art, there are mainly two processes for preparing propylene from methanol: MTO technology and MTP technology. Compared with MTO technology, MTP technology uses a fixed-bed reactor, which is easy to scale up, has low risk, and has great confidence in industrialization. At the same time, the by-product market is gasoline, liquefied petroleum gas and fuel gas with a large capacity, which has high economic benefits . However, the preparation of low-carbon olefins by methanol is a strong exothermic reaction, and a large amount of heat of reaction is generated in the process of generating low-carbon olefins. The heat of reaction is difficult to remove, and a large amount of water is required as a diluent, resulting in high operating costs; ...

Examples

Embodiment 1

[0025] A two-stage preparation process for propylene, using methanol and refinery carbon tetraolefins as raw materials, water as a diluent, prepared in a two-stage fixed-bed reactor; the catalyst in the first-stage fixed-bed reactor contains mass fraction It is the catalyst of 70% ZSM-5 molecular sieve, and the catalyst in the second stage fixed bed reactor is the ZSM-5 molecular sieve catalyst modified by magnesium element, containing mass fraction is 70% ZSM-5 molecular sieve, mass fraction is the magnesium of 0.1% element, and the magnesium element is derived from magnesium oxide. Among them, the silicon-aluminum molar ratio of the ZSM-5 molecular sieve is 260, and the grain size is 1.5 μm.

[0026] Specific steps include:

[0027] (1) The mixture of methanol and water is reacted through the first fixed-bed reactor equipped with a catalyst to obtain a reaction mixture flow of dimethyl ether, methanol and water;

[0028] (2) The reaction mixture flow obtained in step (1) i...

Embodiment 2

[0031] A two-stage preparation process for propylene. The catalyst in the second-stage fixed-bed reactor is a magnesium-modified ZSM-5 molecular sieve catalyst containing 2% magnesium by mass fraction. Other process parameters and steps are as described in the examples 1 described.

Embodiment 3

[0033] A two-stage preparation process for propylene. The catalyst in the second-stage fixed-bed reactor is a magnesium-modified ZSM-5 molecular sieve catalyst containing 4% magnesium by mass fraction. Other process parameters and steps are as described in the examples 1 described.