Applied Catalysis A, General
One-pot synthesis of 2-alkyl cycloketones on bifunctional Pd/ZrO catalyst
2
a
,
b
a
,
a,
b
a,
b
c
a
Weiyang Xue , Bin Gu *, Huiling Wu , Mengyang Liu , Songbo He , Jingmei Li ,
a
a,
Xin Rong , Chenglin Sun *
a
Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 116023 Dalian, China
b
University of Chinese Academy of Sciences, 100049 Beijing, China
c
Green Chemical Reaction Engineering, University of Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands
A R T I C L E I N F O
A B S T R A C T
Keywords:
2-Alkyl cycloketones are essential chemicals and intermediates for synthetic perfumes and pesticides, which are
conventionally produced by multistep process including aldol condensation, separation and hydrogenation. In
present work, a batch one-pot cascade approach using aldehydes and cycloketones as the raw materials, and a
One-pot cascade approach
Bifunctional catalyst
Aldol condensation
Hydrogenation
2
bifunctional Pd/ZrO catalyst was developed for the synthesis of 2-alkyl cycloketones, e.g., cyclohexanone and
cycloheptanone. Very high aldehydes (except for paraldehyde with large steric hindrance) conversion and high
Pd/ZrO
2
yields for 2-alkyl cycloketones (e.g., 99 % of conversion for n-butanal and 76 wt.% of yield for 2-butyl cyclo-
2
-Alkyl cycloketone
◦
hexanone) were obtained at mild temperature of 140 C. After 10 cycles of reuse, Pd/ZrO
2
catalyst showed slight
deactivation (ca. 5 % conversion and 10 % yield losses), due to the coke on the catalyst. However, the perfor-
mance of the catalyst was completely recovered after an oxidative regeneration.
1
. Introduction
[4,18–20], 2-heptyl cyclopentanone [21] and biofuel [22–24]. In these
processes, ZrO , Al O , aluminum silicates, and zeolites are the most
2 2 3
Heterogeneous catalysis has several advantages compared to ho-
popular supports due to their suitable acid-base property for aldol
condensation and interaction with noble metals for hydrogenation [19,
25–27].
mogenous catalysis in terms of product separation, catalyst recycle,
equipment corrosion, and environment pollution, etc [1,2]. It is attrac-
tive to develop novel heterogenous processes and catalysts for chemicals
traditionally produced through homogenous processes. Besides, the
application of multifunctional catalysts makes it possible to integrate
those sophisticated multistep reactions into one-pot cascade processes,
which eliminates intermediates separation and other tedious operations
2-Alkyl cycloketones are essential products or intermediates for
synthetic perfumes and pesticides, which are traditionally produced
through multistep method including aldol condensation, separation and
hydrogenation. For example, 2-Butylcyclohexanone (2BCH) is the
essential intermediate for synthesis of 5(6)-decenoic acid, a widely used
milk-like spice in cream, yogurt, strawberry, etc., through the successive
Baeyer-Villiger oxidation, saponification and dehydration (Route I,
Scheme 1) [28,29]. Aldol condensation between n-butanal and cyclo-
hexanone is firstly catalyzed by NaOH aqueous. After acidification,
extraction, and distillation, the separated 2-butenylcyclohexone
[
3–6]. Although it is difficult to optimize efficient multifunctional
groups that selectively or cooperatively work at specific steps onto single
catalyst, as so far, fruitful one-pot processes have been developed in bulk
chemistry, fine chemistry and biochemistry [4,7–10].
Aldol condensation is a fundamental pathway for C = C bond for-
mation, which conventionally applies liquid acid-base catalysts.
Recently, attentions have been drawn by using heterogenous catalysts,
such as solid alkali hydroxide, carbonates, metal oxides, metal-organic
framework and supported KF [11–15]. Unsaturated C = C hydrogena-
tion is also an important reaction in petrochemistry and fine chemistry,
which is mainly catalyzed by e.g., Pd, Pt, Ru, and Ni supported catalysts
=
(2BCH ) is sequentially hydrogenated by Pd/C catalyst to produce
2BCH. The disadvantages of this process, such as vast wastewater
emission (about 15 tons wastewater per ton of 2BCH), severe equipment
corrosion, sophisticated operation, and low conversion and yield, have
afflicted enterprises for a long time. Therefore, the development of green
and simplified synthesis of 2BCH, e.g., by using the one-pot heteroge-
nous system, is necessary.
[
16,17]. One-pot process cascading aldol condensation and hydroge-
nation have been applied to synthesize methyl isobutyl ketone (MIBK)
2
Herein, a bifunctional heterogeneous Pd/ZrO catalyst was prepared
*
Received 9 February 2021; Received in revised form 10 March 2021; Accepted 12 March 2021
Available online 16 March 2021
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