Microwave‐Assisted Rapid Preparation of Vermiculite‐Loaded Nano‐Nickel Oxide As a Highly Efficient Catalyst for Acetylene Carbonylation to Synthesize Acrylic Acid

Abstract

With CuBr2 as a co‐catalyst, the nickel‐supported two‐dimensional layered vermiculite (2D‐VT)‐based composite [Ni(NO3)2•6H2O/2D‐VT] was used as a precursor and applied to various calcination methods to produce catalysts. These catalysts were used in the acetylene carbonylation reaction to synthesize acrylic acid (AA). The catalysts were characterized and evaluated by scanning electron microscope (SEM), transmission electron microscope (TEM), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), inductively coupled plasma (ICP), hydrogen temperature‐programmed reduction (H2‐TPR), nitrogen adsorption desorption analyzer (BET) and thermogravimetric analysis (TG). We found that the microwave (MW) radiation calcined catalyst (MW‐NiO/2D‐VT) exhibited better catalytic performance than the muffle furnace (MF) calcination catalyst (MF‐NiO/2D‐VT). This difference is observed owing to the fast speed of microwave radiation heating, short baking time, and the instantaneous formation of nano‐NiO particles that have better dispersibility and uniformity, which is more conducive to the performance expression of nickel oxide. Under the optimal reaction conditions, the yield of AA is 86.3%. During the reaction, the MW‐NiO/2D‐VT catalyst is more stable and produces less by‐deposits than the MF‐NiO/2D‐VT catalyst. Thus, MW‐NiO/2D‐VT is more conducive to improving the selectivity of AA. In addition, theoretical calculations show that the MW‐NiO/2D‐VT catalyst has a lower apparent activation energy, which kinetically explains why MW‐NiO/2D‐VT is an excellent catalyst.

Supported nanocatalysts: recent developments in microwave synthesis for application in heterogeneous catalysis

“…There is also report on preparation of TiO 2 /G from GrpO, titanium isopropoxide, TTIP (variable) in isopropyl alcohol and N 2 H 4 via MW irradiation in a closed pyrex glass bottle. 161 The obtained dried precipitate was finally calcined at 400 °C for 4 h. 164 The overall size distribution and crystallinity again confirmed that MW method is superior for producing smaller grained highly crystalline NiO.…”

“…206 MW-NiO/2D-Vmt catalyst performed better activity than the MF-NiO/2D-Vmt catalyst for acetylene carbonylation in a constant volume sealed container for synthesizing acrylic acid (AA). 164 Again, smaller NiO grains in the MW-NiO/2D-Vmt catalyst produced higher yield of AA (86 %), whereas, the MF-NiO/2D-Vmt catalyst produced 68 % yield. However, the MW-NiO/2D-Vmt catalyst was unstable, demonstrated drastic change in morphology and disappearance of NiO siganl after the first cycle.…”

“…Fair number of attempts have also been made to prepare supported simple metal oxide (CoO x , Co 3 O 4 , NiO, Fe 3 O 4 , SnO 2 , CeO 2 , TiO 2 ) nanocatalysts for application in petrochemical industry. 75,[160][161][162][163][164][165][166] In order to improve the catalytic activity as well as versatility in application potential of simple metal or metal oxide nanocatalysts, investigations on supported bimetal, [171][172][173][174][175][177][178][179][180][181][182][183][184][185][186][187] mixed metal oxide [188][189][190][191][192][193]196,197 and ternary metal 198,199 nanocatalysts are also available. MW assisted synthesis has been claimed to be economically viable short green method to produce supported nanocatalyst.…”

“…In some instances even better recycle stability was observed for MW assisted synthesized supported nanocatalysts. 118,164,174 Though the data on stability and recyclability of MW synthesized nanocatalyst is encouraging but much effort is necessary to further improve the performance, as in some cases the activity decreased significantly after few reaction cycles. 85,86,95,98,99,107,116,133,174 The decrease in activity during recycle in either case occurred mostly due to change in morphology, aggregation, graphitization and loss of active catalyst via leaching of metal ions.…”

“…85,86,95,98,99,107,116,133,174 The decrease in activity during recycle in either case occurred mostly due to change in morphology, aggregation, graphitization and loss of active catalyst via leaching of metal ions. 84,86,118,133,134,155,164 In this regard, one pot synthesis of supported nanocatalyst under mild MW condition without additional calcination and use of functional support for strong fixation can be tried to further improve the recycle stability so that both aggregation and leaching of metal ions is reduced. It is noteworthy to mention that in batch catalysis reaction in constant volume reactor, the activity of nanocatalyst decreased sharply compared to that under continuous flow reaction conditions in flow tube reactor (Table S1).…”