Selective Dehydration of Alkanediols into Unsaturated Alcohols over Rare Earth Oxide Catalysts

Abstract

Syntheses of unsaturated alcohols in the vaporphase catalytic dehydration of alkanediols over rare earth oxides are reviewed. CeO 2 effectively catalyzes the dehydration of 1,3-butanediol to produce 3-buten-2-ol and trans-2-buten-1ol. Heavy rare earth oxides such as Er 2 O 3 , Yb 2 O 3 , and Lu 2 O 3 selectively catalyze the dehydration of 1,4-butanediol to produce 3-buten-1-ol. In the dehydration of 1,5-pentanediol, Yb 2 O 3 , Lu 2 O 3 , and Sc 0.5 Yb 1.5 O 3 catalysts efficiently work to produce 4-penten-1-ol. The active and selective oxides are composed of large particles with well-crystallized fluorite or bixbyite structure. Small oxide particles with poor crystallinity decrease the selectivity to unsaturated alcohols because of their dehydrogenation ability. In the reactions of different alkanediols, the reactivity of alkanediol depends on the length between the OH groups as well as on the geometry of the catalyst surface, which is affected by the distance between rare earth cations. For example, over CeO 2 , the reactivity order of the alkanediols is 1,3-butanediol > 1,4-butanediol > 1,5-pentanediol > 1,6-hexanediol. Quantum calculations support a probable reaction mechanism: OH groups and the H of the position-2 methylene group of 1,3butanediol are interacted with the surface Ce 4+ to form a tridentate coordination, and the abstraction of the position-2 H by Ce 4+ is the initial step of 1,3-butanediol dehydration in the formation of unsaturated alcohols.

Vapor-phase Catalytic Dehydration of 2,3-Butanediol into 3-Buten-2-ol over Sc2O3

“…In our previous work, we found that REO with small ionic diameter of rare earth metal cation is effective in the formation of unsaturated alcohols from diols. 13 In the present work, the highest formation rate of 3B2OL was obtained at the smallest ionic radius of Sc 3+ , although the rate for Sc 2 O 3 at 325°C was underestimated due to the high conversion. This indicates that an active site may generate on surface adsorption sites of a compact size over Sc 2 O 3 catalyst.…”

“…13 Catalytic activity of REOs depends on the position of OH groups of reactant diols: 1,3-diols are effectively dehydrated into 3B2OL and 2-buten-1-ol by CeO 2 ; 1,4-butanediol can be dehydrated to 3-buten-1-ol by Er 2 O 3 , Yb 2 O 3 , and Lu 2 O 3 ; 13 1,5-pentanediol to 4-penten-1-ol by Sc 0.5 Yb 1.5 O 3 .…”

“…13 Catalytic activity of REOs depends on the position of OH groups of reactant diols: 1,3-diols are effectively dehydrated into 3B2OL and 2-buten-1-ol by 14 Lattice parameters of the cubic REOs seem to affect the adsorption and activation of alkanediols.…”

Future Prospect of the Production of 1,3-Butadiene from Butanediols

“…111,114 Dehydration of 1,3-BDO into UOLs such as 3B1OL, 2B1OL, and 3B2OL have been investigated over ZrO 2 , 81 solid acid metal oxides, 81 CeO 2 -ZrO 2 , 115 and all of the rare earth metal oxide catalysts. 116,117 In the rare earth oxides, CeO 2 is the most active and selective catalyst. CeO 2 with weak basic sites shows the highest 1,3-BDO conversion at 325°C as well as the sum of selectivity of 2B1OL and 3B2OL over 99%.…”

“…The catalytic activity is Changes in the formation rate of the total corresponding UOLs with ionic radius of rare earth cations. 96,117 strongly dependent on the calcination temperature of the catalyst. In particular, the sample calcined at 800°C gave the highest 2,3-BDO conversion and 3B2OL selectivity.…”