Investigation Of The Adsorbent Purifying Olefins Made Of Coal To Polymer Grade Propylene

Methanol to olefin (MTO) process technology is to use methanol made of coal as raw material, through the molecular sieve catalyst technology to prepare light olefins. Due to the characteristics of the raw material, the products of olefins inevitably contain trace amount of oxygen-containing compounds such as methanol, DME and others, which should be removed, otherwise, the products of olefins could not reach the polymer grade requirement.Based on trace analysis technique, this article first investigated active components of the adsorbent, then to study the forming additives. With high purity nitrogen gas or ethylene gas used as the background, several potential different active adsorbent components were evaluated respectively. Compared with other components,13X type molecular sieve had the highest adsorption capacity. On the other hand, the adsorbent forming additives were also investigated respectively, the results showed that activated alumina had a larger adsorption capacity compared to other forming agents, but much less than13X type molecular sieve. Then the shaped adsorbent was tested in the scale of small amount and medium amount, the results showed that the shaping adsorbent ball with13X molecular sieve as active component, and activated alumina as forming agent in the ball forming preparation process, could remove the trace oxygen-containing impurities such as methanol, DME etc. in liquid propylene from10ppm(w) content to less than lppm(w), which meet the polymer grade propylene requirements.In this article, the ion exchange property of molecular sieve was used to study the effect of the ions. The13X molecule sieve was modified with Ca2+ion or Zn2+ion in the single factor or uniform experiments to investigate the different degrees of ion exchange, then by BET, SEM, XRD analysis, and adsorption experiment in gas phase, the structure properties and application information was connected. It was found that the larger volume of molecular sieve, the better adsorbability of oxygen-containing compounds, and that13X molecular sieve and activated alumina may have different role in the adsorbent due to its different micro, mesoporous structure characteristics respectively. To achieve the purpose of purifying olefins, the two components should be combined reasonably to meet not only the diffusion demand of the liquid olefins, but also the demand of selective adsorption of polar oxygenated compounds from the olefins.