RSC Advances View Article Online PAPER View Journal | View Issue A recyclable heterogeneous–homogeneous– heterogeneous NiO/AlOOH catalysis system for Cite this: RSC Adv., 2020, 10,1634 hydrocarboxylation of acetylene to acrylic acid† Yakun Li, ab Lifang Yan,a Qiaofei Zhang,c Binhang Yan*a and Yi Cheng *a Concerns about the high-valued utilization of coal- and natural gas-based acetylene has provided particular impetus for exploration of acrylic acid (AA) production via one-step hydrocarboxylation reaction. Motivated by simple recovery, recycling and reuse of the catalyst, we report a high-performance NiO/AlOOH catalyst À1 À1 with AA space-time-yield of 412 gAA gcat. h , obtainable by a simple incipient wetness impregnation method. Detailed kinetic and controlled experiments confirmed that nickel species on such a solid Received 21st November 2019 catalyst provide a heterogeneous–homogeneous–heterogeneous catalytic cycle where the chelates Accepted 28th December 2019 formed between CO and leached nickel act as the active species. The thorough recovery of leached DOI: 10.1039/c9ra09737f nickel species improves the catalyst stability greatly. These preliminary findings indicate further prospects Creative Commons Attribution-NonCommercial 3.0 Unported Licence. rsc.li/rsc-advances for new heterogeneous catalyst design in traditional homogeneous catalytic systems. 1. Introduction investigated the acetylene carbonylation reaction with the aid of metal halide/silica gel catalysts in detail, but unfortunately, With the depletion of petroleum reserves, it is highly desired to these supported catalysts showed very low AA yield (only 14.2%) study sustainable alternatives. Meanwhile, due to the discovery even under optimal conditions.8 Recently, Shi and coworkers of huge reserves of shale gas by fracking techniques as well as studied the synthesis of AA via hydrocarboxylation of acetylene the breakthrough development of coal- and natural gas-based over Ni- and Cu-exchanged Y-zeolite with the presence of cupric 3,9 This article is licensed under a acetylene, the diverse utilization of acetylene to produce high salt and nickel salt as promoter respectively. They found that value-added chemicals has received renewed interest.1,2 As an the catalytic activity showed a pronounced dependence of the ideal atom economy reaction, the one-step hydrocarboxylation reaction conditions and Ni2+ and Cu+ ions in the zeolites were of acetylene to acrylic acid (C H +CO+HO / C H O ) responsible for the catalytic activity, being similar to the Open Access Article. Published on 08 January 2020. Downloaded 9/26/2021 4:59:29 PM. 2 2 2 3 4 2 provides a promising and alternative route to replace the partial homogeneous catalysts. oxidation of propene method, especially in coal- or gas-rich Signicantly, question arises simultaneously when using areas.2,3 However, the commercial production of AA using the solid catalysts in the liquid phase (liquid–solid or gas–liquid– homogeneous NiBr2–CuBr2 catalyst system developed by BASF solid system) because the active transition metals may leach Co. remains problematic due to the difficulty in product-catalyst from the catalysts surface into the liquid.10,11 As a consequence, separation, usage of expensive and sensitive ligands, and cor- it is very difficult to clarify the catalytically active species rosivity of acid assistants. Tremendous efforts were made in whether homogeneous or heterogeneous, even if there is only – recent years to solve these problems, such as new nickel or trance amount of active metals in the liquid.12 14 For example, palladium complexes,4,5 water-soluble ligands6 and even ligand the argument about the actual active species (palladium atoms free catalyst,7 but the outcomes were still in controversy. Nor- or complexes in solution,15 or palladium nanoparticles16,17)in mally, heterogeneous catalysis is an effective and efficient heterogeneous Heck and Suzuki coupling reactions has still method to overcome the above problems due to the facial been going on. Up to now, however, there are no data con- separation and recovery of catalysts. Bhattacharyya rstly cerning the problem of leaching about heterogeneous catalysts for the hydrocarboxylation of acetylene and thereby not clear whether this reaction is homogeneous or heterogeneous. aDepartment of Chemical Engineering, Tsinghua University, Beijing 100084, PR China. Correspondingly, it is highly desired not only to develop new E-mail: [email protected]; [email protected] heterogeneous catalysts with excellent performance but also to bDepartment of Material and Chemical Engineering, Zhengzhou University of Light clarify the actual active species whether homogeneous or Industry, Zhengzhou, Henan 450001, PR China heterogeneous. cCollege of Chemistry, Chemical and Environmental Engineering, Henan University of In this work, a pseudoboehmite (AlOOH) supported nickel- Technology, Zhengzhou, Henan 450001, PR China † Electronic supplementary information (ESI) available. See DOI: based catalyst (denoted as NiO/AlOOH) synthesized by 10.1039/c9ra09737f a simple incipient wetness impregnation was tested. Such 1634 | RSC Adv.,2020,10,1634–1638 This journal is © The Royal Society of Chemistry 2020 View Article Online Paper RSC Advances a catalyst showed a high AA space-time-yield (STY) of 412 gAA several times and subsequently pressurized with acetylene to À1 À1 gcat. h and AA yield of 65.6%. During the hydro- 0.5 MPa and then to 4.5 MPa of initial total pressure with CO carboxylation reaction, the dissolution of nickel species was (both controlled by mass owmeter) at room temperature. The observed due to the induction of CO and CuBr2. The leached molar ratio of CO/C2H2 was 1.75. The reactor was then heated to nickel species underwent a heterogeneous–homogeneous– 250 C and kept for 30 min under constant agitation (800 rpm). heterogeneous catalytic cycle. Aer reaction, the autoclave was quickly cooled to room temperature and the tail gas and liquid were collected, calcu- 2. Experimental section lated and analyzed. For recycling experiments, the catalyst used in the previous run was separated by centrifugation and washed 2.1 Catalysts preparation with acetone for several times and reused aer drying in air. The NiO/AlOOH catalysts were prepared using a simple incip- The qualitative and quantitative analysis of the reactants and ient wetness impregnation by impregnating pseudoboehmite products was performed by a Shimadzu GC 2014 gas chro- – (AlOOH) with an aqueous solution of nickel nitrate (Ni(NO3)2- matograph equipped with a P N packed column for identifying $6H2O) followed by calcining in air at 300 C for 2 h. Both C2H2,C2H4, CO and CO2 and a Stabilwax capillary column for AlOOH (purchased from Zibo Jiu Ru Industrial and Trading Co., C2H2, aldehyde, acrylic acid, acetone and tetrahydrofuran Ltd) and nickel nitrate (purchased from Sinopharm Chemical (THF). The conversion of acetylene, selectivity and yield of Reagent Co., Ltd) were used as received without further puri- acrylic acid and the space time yield (STY) are dened as cation or drying. Notably, nickel nitrate was dissolved in an follows: acetone solution (C3H6O, purchased from Beijing Tong Guang n À n À n Conv: ¼ 0 g l  100% (1) Fine Chemicals Company). n0 For comparison, some other supports with high surface area nAA like silicon dioxide (SiO2, purchased from Sinopharm Chemical Y ¼  100% (2) n0 Creative Commons Attribution-NonCommercial 3.0 Unported Licence. Reagent Co., Ltd), alumina (g-Al2O3, purchased from Sino- pharm Chemical Reagent Co., Ltd), MCM-41 zeolite (purchased from Tianjin Nanhua Catalyst Co., Ltd) and Mg–Al layered S ¼ Y/conv. (3) double hydroxides (Mg–Al LDHs, purchased from Shanghai w STY ¼ AA  100% (4) Macklin Reagent Co., Ltd) were also investigated by same wcat:  t method. where n0, molar content of acetylene for feedstock before reac- tion; n , molar content of acetylene for tail gas aer reaction; n , 2.2 Characterization g l molar content of acetylene for residue aer reaction; nAA, This article is licensed under a The actual nickel content of NiO/AlOOH catalysts and the nickel amount of acrylic acid produced during reaction; WAA, mass of content in residue a er reactions are measured by inductively acrylic acid produced during reaction; Wcat, mass of catalyst for coupled plasma-optical emission spectrometry (ICP-OES, Var- input before reaction; t, reaction time. ian Vista RL spectrometer). Specic surface areas of NiO/AlOOH Open Access Article. Published on 08 January 2020. Downloaded 9/26/2021 4:59:29 PM. catalysts are determined by nitrogen adsorption carried out at 2.4 Kinetic investigation 77 K on a Quantachrome Autosorb-6B analyzer. The data are To explore the nature of catalysis, a detailed kinetic experiment calculated by multipoint BET analysis method in the pressure was carefully conducted. In a typical experiment, known quan- range of P/P ¼ 0.05–0.30. Prior to the measurement, the À 0 tities of catalyst powders (0.1 g), CuBr (0.12 mM L 1), H O (15 samples are degassed in vacuum at 300 C for 2 h. X-ray 2 2 mL), and acetone (150 mL) were charged into the stirred pres- diffraction (XRD) is performed on a Bruker D8 Advance equip- sure reactor. The reactor was rstly ushed with nitrogen for ment with Cu Ka radiation (35 kV and 25 mA). 2q scans are run several times and subsequently pressurized with acetylene to from 20 to 80 at a rate of 0.5 degree per minute. The spectra are 0.5 MPa and then to 4.5 MPa of initial total pressure with CO identied with JCPDS database (Joint Committee of Powder (both controlled by mass owmeter) at room temperature. The Diffraction Standards) and the ICSD database (Inorganic Crystal molar ratio of CO/C H was 1.75. The reactor was then heated to Structure Database). The morphology of NiO/AlOOH catalysts 2 2 set temperature under constant agitation (800 rpm). Then, the are characterized by JEOL JEM2010 high-resolution trans- autoclave was quickly cooled to room temperature and the mission electron microscopy (HR-TEM) equipped with an liquid was collected and the nickel content was analyzed by ICP energy dispersive X-ray uorescence spectrometer (EDX).