Heterogeneous catalysts in the aldol condensation of heptanal with cyclopentanone

Abstract

A large number of heterogeneous catalysts were tested in the aldol condensation of heptanal with cyclopentanone. There are many possible products from this aldol condensation, among which the most desired is 2-heptylidenecyclopentanone. As heterogeneous catalysts, the following were tested: caesium modified zeolites, functionalized MCM-41, and single (MgO, CaO, ZnO) and double (Mo–Si, Mg–Al, Zn–Al) metal oxides. The activity of modified zeolites and functionalized zeolites in this aldol condensation was low, whereas single and double metal oxides possessed high activity. The highest selectivity to the desired 2-heptylidenecyclopentanone (52%) was obtained using magnesium oxide as catalyst.

Solvent-free cross aldol condensation of aldehydes and ketones over SrMo1-xNixO3-δ perovskite nanocrystals as heterogeneous catalysts

“…In this aldol condensation, the perovskites, SrMoO 3 and SrNiO 3 , were found to be effective catalysts; however, their activities were enhanced when Ni and Mo, respectively, were incorporated into the perovskite structures. Both Ni and Mo have been used in variants of aldol condensation reaction and were found to be fairly active above 200 °C [ 15 , [64] , [65] , [66] ]. In this work, multicationic perovskites catalysts, SrMo 0.3 Ni 0.7 O 3-δ and SrMo 0.7 Ni 0.3 O 3-δ were used at 80 °C.…”

“…Moreover, they are in homogeneous solution, which makes them hard to recycle. Heterogeneous metal oxide catalysts, such as metals supported on modified silica [ [15] , [16] , [17] , [18] , [19] , [20] ], hydrotalcite [ 15 ], zeolites [ 21 ] and other metal oxides [ [22] , [23] , [24] ], however, the require addition of a co-catalyst and/or scavenger molecules, they are done at high temperatures, and they also require a hefty amount of time to run to completion [ [25] , [26] , [27] , [28] ].…”

Impact of Hydrotalcite’s Basic Sites on the Catalyst Stability and the Branching Selectivity in α-Hydroxyketone Aldolization

“…12 Provided active and stable catalysts, the heterogeneous materials may offer easier product separation options and enable continuous processing. 13 Basic oxides and hydroxides (e.g., CaO, 14 TiO 2 , ZrO 2 ), 15 modified apatite 16 and alumina, 17 mesoporous materials, 18 basic resins, 19−21 and others, 22,23 are abundantly investigated, in both gaseous and condensed phases depending on the boiling point of the compounds. Gas-phase aldolization uses mostly mixed oxides, in which the main challenge is catalyst coking due to sequential surface condensation of strongly adsorbed intermediates, ultimately leading to polymeric deposits.…”

“…Whereas homogeneous bases, such as NaOH, are still employed in the industrial condensation processes, there is a vast literature reporting and studying aldol condensation with heterogeneous catalysis . Provided active and stable catalysts, the heterogeneous materials may offer easier product separation options and enable continuous processing . Basic oxides and hydroxides (e.g., CaO, TiO 2 , ZrO 2 ), modified apatite and alumina, mesoporous materials, basic resins, − and others, , are abundantly investigated, in both gaseous and condensed phases depending on the boiling point of the compounds.…”

Preparation of β‐hydroxy Ketones via High Efficient Aldol Reaction over Nickel Oxide Nanoparticles as a Powerful and Reusable Heterogeneous Catalyst: Central Composite Design

“…[14] In contrast, heterogeneous catalysts brings some advantages such as simple catalyst recovery, reduction of effluent streams and by-products, and high selectivity. [15,16] Various heterogeneous catalysts such as modified zeolite, [17] magnetically retrievable catalyst, [18] metal oxide, [19,20] mixed metal oxides, [21][22][23] and so on have been used in aldol condensations. Among them, metal oxides can cover the most proceedings and catalyst families used in variant industries.…”