Method for producing polyoxymethylene dimethyl ethers

摘要

A method for producing polyoxymethylene dimethyl ethers using fluidized bed reactor is provided. The fluidized bed reactor gives high conversion of feedstock during synthesis of polyoxymethylene dimethyl ethers. The product separation process includes pre-rectification, extractive rectification and vacuum rectification in series. In the pre-rectification process, the side-draw fraction PODE2 is recycled into the fluidized bed reactor, thus product distribution and selectivity to target components in the reactor can be improved. The extractive rectification process realizes coupling of neutralization, extraction, recovery of unconverted feedstock and products separation, thus significantly simplifies the process. The method for preparation of polyoxymethylene dimethyl ethers in this invention is simple, and has high conversion of feedstock, low energy cost and high selectivity to products.

主权项

1. A method for producing polyoxymethylene dimethyl ethers, the method comprising:
conducting a synthetic reaction process including:
feeding dimethoxymethane and paraformaldehyde into a fluidized bed reactor, andcontacting the dimethoxymethane and paraformaldehyde with a solid acid catalyst to produce a reaction mixture of PODEk, wherein k is an integer bigger than 1; conducting a product separation process including: a pre-rectification, an extractive rectification and a vacuum rectification; during pre-rectification:
feeding the reaction mixture from the fluidized bed reactor into a pre-rectifying column and separating the reaction mixture into an overhead fraction of dimethoxymethane, a side-draw fraction of PODE2 and a heavy fraction of PODEn>2, unconverted formaldehyde and by-products, recycling a first portion of the overhead fraction of dimethoxymethane into the fluidized bed reactor,refluxing a second portion of the overhead fraction of dimethoxymethane into the pre-rectifying column, and recycling the side-draw fraction of PODE2 into the fluidized bed reactor; during the extractive rectification:
feeding the heavy fraction of PODEn>2 into the top of an extractive rectifying column,contacting the heavy fraction of PODEn>2 with an extraction solvent,entering the unconverted formaldehyde and by-products into an extract phase, andregenerating the extract phase to separate the extraction solvent and the unconverted formaldehyde for recycling; and during the vacuum rectification:
feeding a raffinate phase from the bottom of the extractive rectifying column into the vacuum rectifying column, andseparating the raffinate phase into an overhead fraction of PODE3˜m and a heavy fraction of PODE(m+1)˜n, wherein m is an integer bigger than 3 and n is an integer bigger than m+1.