Highly Active and Selective Zr/MCF Catalyst for Production of 1,3-Butadiene from Ethanol in a Dual Fixed Bed Reactor System

Abstract

Copper and zirconium oxide clusters were highly dispersed on mesocellular siliceous foam (MCF), a mesoporous silica support with ultra large, interconnected nanopores. These catalysts (denoted as Cu/MCF and Zr/MCF) were separately loaded into two fixed bed reactors as catalysts for the conversion of ethanol (EtOH) to 1,3-butadiene (BD). Under optimal conditions, high BD selectivity (up to 73%) and ethanol conversion (up to 96%) were achieved at weight hourly space velocities of 1.5 and 3.7 h −1 . This translates to an unprecedented productivity of 1.4 g BD /g catalyst h −1 (208 g BD /l catalyst h −1 ). The high catalytic performance is attributed to the highly selective and active catalysts. The EtOH dehydrogenation activity of Cu/MCF could be accurately controlled in the first reactor, which delivers a fixed ratio of the acetaldehyde/EtOH mixture to Zr/MCF in the second reactor. The optimal ratio minimizes EtOH dehydration to ethylene by Zr/MCF, while maximizing the selectivity to BD. MCF was found to be superior over commercial porous silica in terms of EtOH conversion, BD selectivity, and tolerance to coking. High BD selectivity was maintained with a slight decrease in EtOH conversion over 42 h, which was readily restored upon regeneration by thermal treatment in air.

Recent Breakthroughs in the Conversion of Ethanol to Butadiene

“…Measuring the activity of gold-modified catalyst without such phase could shed some light on this issue. Silica-supported Cu and Ag where also used as catalysts for the formation of acetaldehyde in the first step of the Ostromislensky process [36,60]. Of the two metals, copper was found to be the highly selective and stable, while silver deactivated and generated some amounts of byproducts [60].…”

“…The most active catalyst was obtained by dispersing zirconium oxide over mesocellular silica foam [36]. The performance of this catalyst was attributed to the high degree of dispersion of ZrO 2 enabled by the great surface area of the support, and to the large, interconnect mesopores of MCF, which diminish the formation of coke and issues relating to the mass-transfer of reagents into the catalyst.…”

“…Another parameter that influences the reaction is the catalyst pre-treatment, usually done under inert atmosphere at high temperature to activate the material. Finally, the ratio of ethanol-to-acetaldehyde being fed in a reactor is a crucial factor of the two-step process, as it can influence the BD productivity and product distribution [18,36,41,47,48]. Since several papers have reported different optimal ratios, it is likely that this factor is governed by the nature of the catalytic system and the other reaction conditions.…”

“…When available, this paper will also indicate the TOS at which the activity was recorded. It has been repeatedly demonstrated that the main culprit behind catalytic deactivation was the formation of coke on the catalytic surface [4,36,47,49,50]. Table 1 highlights the performances of notable catalysts for the one-step process reported in the past hundred years to provide references to the readers (catalysts 1 to 10 in Table 1), as well as the catalytic systems reviewed in this work.…”

“…Lee et al used a connected double fixed reactor system with dedicated functionalities to achieve high butadiene production from ethanol. In the first reactor, a gaseous ethanol feed was converted over a copper-containing catalyst [36]. The second reactor was packed with zirconium-containing catalyst to convert the resulting ethanol-acetaldehyde mixture to butadiene.…”