Study On Methanol To Olefins With High Selectivity

Light olefins like Ethylene and Propylene are important organic raw materials for the petrochemical industry, however, the traditional route of producing light olefins is Naphtha Cracking, that is, the oil route, the disadvantage of which is over-depending on the oil/petroleum. With the reduction of oil reserves and the rise of oil price, it is desirable and exigent to find the oil substitute, that is, the non-oil route, to reduce the stress from the scarcity of light olefins. Methanol to olefins from coal or natural gas via syngas is a significant chemical technology that is remarkable and promising.This study is aim to contribute a series of multi-component catalysts Na/ZSM-5、Na-K/ZSM-5、Na-Li/ZSM-5、Na-K-Li/ZSM-5、Na-Li-Ca-Mg/ZSM-5with high catalytic performance used for Methanol to olefins process, adopting ZSM-5as the carrier and made by the immersion method. Research and comparison showed that, among the prepared multi-component catalysts consisting of alkali metals or alkaline-earth metals or their combination, 340Na+50K/ZSM-5catalyst showed the optimum catalytic performance, under the condition of360℃～375℃, atmospheric pressure, liquid hourly space velocity of Methanol2h-1,the one-way conversion of Methanol can be up to96.61%, the selectivity to C2=～C4=can be up to89.45%, accordingly, the selectivity to C2=～C3=was about74.75%.XRD spectrum shows that, the multi-component catalysts still maintain the characteristic peaks of carrier, moreover, the added metals are highly scattered on carrier in the form of single layer within the existing amounts of loaded metals. BET characterization showed that the addition of metals modified the pore structure or narrowed the pore size, thereby increased the selectivity to C2=～C4=. Diffuse reflectance infrared (IR) of adsorbed ammonia spectra showed that the acidity sites in the surface of catalysts are not uniform, existing two category of acidity sites:Bronsted type and Lewis type; moreover, with the increase of amount of metals, the total acidic density was decreased, accordingly, the activity of Methanol trended to decrease, whereas, the selectivity to light olefins was increased. Besides that, the Material Balance Method was introduced and illustrated using a specific catalyst as an example.