エタノールからの選択的な1,3-ブタジエン生成におけるMgOの触媒作用とタルク触媒でのZn²⁺の役割

Abstract

1,3-Butadiene is produced as a by-product during ethylene production from steam crackers. Increasing demand for sustainable chemicals has driven the search for substitute petrochemicals from renewable biomassderived chemical resources. 1,3-Butadiene is an important commodity chemical and an alternative route for its production, from ethanol, was developed about a hundred years ago. In the current climate, the development of a new high-performance catalyst for the bio-based synthesis of 1,3-butadiene is an important challenge. This paper reviews our recent studies into the synthesis of 1,3-butadiene from ethanol using MgO alone, and Zn-containing talc (Zn-Talc) that has not previously been used as a catalyst for this reaction. In particular, we focus on catalysis by MgO and the role that Zn 2 in the Zn-Talc catalyst plays in the selective production of 1,3-butadiene. The reaction mechanism for the formation of 1,3-butadiene from ethanol over MgO, and the effect of Zn 2 on the rate of ethanol conversion are discussed.

Ethanol-to-butadiene: the reaction and its catalysts

“…Undoubtedly, ethanol enables the conversion of crotonaldehyde to butadiene, but so does hydrogen, 137 propanol, 34,138 which yields C 3 and C 5 Scheme 6 Mechanisms of crotonaldehyde reduction to crotyl alcohol and its dehydration to butadiene on different catalysts. 99,116,141 96,139,142 Catalysis Science & Technology Mini review byproducts, or even crotyl alcohol itself. 34 Therefore, its role has been the subject of debate.…”

“…[143][144][145] Recently, Baba et al reiterated that ethanol is not the sole reducing agent of crotonaldehyde in the ethanol-to-butadiene reaction. This claim stems from the fact that the reaction can proceed on MgO, 96,139,142 but not CaO, despite both being alkaline-earth metal oxides with basic properties. According to the authors, contrary to MgO, CaO cannot perform the heterolytic dissociation of hydrogen.…”

Recent Advances in Catalysts for the Conversion of Ethanol to Butadiene

“…[63] Baba's group synthesized Zn and Ge-talc, a 1 : 2 layered magnesium silicate, where one MgO octahedral sheet is sandwiched between two SiO 2 tetrahedral sheets. [69,70] Despite a modest selectivity of 48%, the productivity for Zn-talc was 1.1 g BD g cat À 1 h À 1 , which puts it amongst the most active catalysts. [69] Kinetic studies indicated that Zn promoted the rate of acetaldehyde formation but did not affect the subsequent aldol condensation step.…”

“…[69,70] Despite a modest selectivity of 48%, the productivity for Zn-talc was 1.1 g BD g cat À 1 h À 1 , which puts it amongst the most active catalysts. [69] Kinetic studies indicated that Zn promoted the rate of acetaldehyde formation but did not affect the subsequent aldol condensation step. In contrast, the Ge-talc had higher BD selectivity, 71%, but a slightly lower activity than Zn-talc.…”

Synthesis of 1,3-Butadiene and Its 2-Substituted Monomers for Synthetic Rubbers

“…Benefiting from an understanding of the reaction pathway, a more efficient two-step process employing acetaldehyde/ethanol as feedstock was developed ( Figure 2), but there is still a lot of work to do to realize a BD production process with a yield higher than 90%. Although extensive studies have been performed over the past 3 years [36][37][38][39][40][41][42][43][44][45][46][47] (Table 1), as well as several published reviews [17,[48][49][50][51][52][53], the development of efficient processes and robust catalysts still remains a challenge and issues related to carbon efficiency, catalyst cost, toxicity, feedstock tolerance and backend optimization need further investigation [49]. The general reaction mechanism and major by-products of 1,3-butadiene (BD) production from ethanol [19,[23][24][25][26][27][28][29][30][31][32][33][34][35].…”