Effect of C3-Alcohol Impurities on Alumina-Catalyzed Bioethanol Dehydration to Ethylene: Experimental Study and Reactor Modeling

Abstract

The impact of feedstock impurities on catalytic process is among the crucial issues for processing real raw materials. A real and model 92%-bioethanol contaminated with 0.03–0.3% mol 1-propanol or 2-propanol were used to make ethylene on a proprietary alumina catalyst in isothermal flow reactor. We proposed a formal kinetic model to describe the impure bioethanol conversion to ethylene and byproducts and used it to evaluate the multi-tubular reactor (MTR) for 60 KTPA ethylene production. The simulated data agree well with experimental results. Under reaction-controlled conditions, C3-alcohols strongly suppress the formation of by-products and ethylene-from-ethanol, and slightly inhibit the formation of ethylene-via-ether. It is the suppression of the ethylene-via-ether route that causes a decrease in ethanol conversion. The predominant formation of ethylene-via-ether results in an increased ethylene yield but doubling the catalyst load is required to achieve conversion as for pure feedstock. 2-Propanol has a stronger effect on dehydration than 1-propanol. Diffusion inside the grain’s levels out the effect of C3-alcohols on the process in MTR, giving an ethylene yield as high as ~98% while dehydrating a contaminated 92% ethanol. However, impurities dilute ethanol and generate propylene (which contaminates target product), and these worsen feedstock consumption and ethylene productivity in MTR.

In-Depth Understanding of Highly Active Silicotungstic Acid Catalysts for Ethanol Dehydration to Ethylene under Industrially Favorable Conditions

“…4−6 Compared with the high singletrain capacity (>1500 kt/a) of steam cracking technology, the ETE process is more flexible, satisfying the needs of small and medium sized scale. 7,8 Besides, the ETE process can be conducted in fixed-bed reactor, operating at mild temperatures and pressures, achieving highly purified ethylene. 9 Ethanol can be obtained by thermochemical conversion of coal/solid waste and microbial fermentation of biomass such as sugar canes, molasses, corns, and tapioca.…”

“…Ethylene is an important commodity, with a number of key derivatives, such as polyethylene, vinyl chloride, ethylene oxide, ethylbenzene, and poly­(ethylene terephthalate). , Nowadays, ethylene is primarily produced by steam cracking of ethane, liquefied petroleum gas, naphtha, and other petroleum-based feedstocks . With the depletion of oil resource, the ethanol dehydration to ethylene (ETE) process provides an alternative route to produce ethylene beyond the conventional hydrocarbon-cracking process. − Compared with the high single-train capacity (>1500 kt/a) of steam cracking technology, the ETE process is more flexible, satisfying the needs of small and medium sized scale. , Besides, the ETE process can be conducted in fixed-bed reactor, operating at mild temperatures and pressures, achieving highly purified ethylene …”