Insight into the mechanism of the key step for the production of 1,4-butanediol on Ni(111) surface: A DFT study

The reaction mechanism for 2-butyne-1,4-diol (BYD) hydrogenation to 1,4-butanediol (BDO) and related side reactions on Ni(111) surface was studied by density functional theory (DFT) calculation. BYD hydrogenation is more likely to generate cis-2-butene-1,4-diol (cis-BED) than trans-2-butene-1,4-diol (trans-BED), and the isomerization of cis-BED to trans-BED is difficult to occur. BDO is mainly derived from cis-BED hydrogenation. 4-hydroxybutanal (γ-HALD) is mainly from cis-BED isomerization with high reaction energy barriers. Compared with hydrogenation to BDO, γ-HALD is more prone to isomerization to 2-hydroxytetrahydrofuran (HTHF). However, the high reaction barrier of cis-BED to γ-HALD limits its cyclization to the HTHF. Cis-crotyl alcohol (cis-CROL) is easier to generate than trans-crotyl alcohol (trans-CROL) on Ni(111) surface. N-butyraldehyde (BAL) is mainly derived from the isomerization of cis-CROL with high reaction energy barriers. Compared with isomerization to BAL, cis-CROL and trans-CROL are more prone to hydrogenation to n-butanol (BOL). The by-product BOL is mainly derived from the hydrogenation of cis-CROL.