Carbonylation Of Acetylene To Acrylic Acid And Acrylic Esters By Heterogeneous Ni-Based Catalyst

Acrylic acid and acrylic esters, as the most important chemical raw materials and polymer monomers, are produced mainly via partial oxidation of propene in industry at present. With the gradual exhaustion of the natural gas and petroleum in the world, coal to acetylene became an important feedstock for the synthesis of commodity chemicals again. The development of oxygen thermal process technology producing calcium carbide from coal further promoted the research of acetylene downstream products. Carbon monoxide produced as a byproduct from the calcium carbide production can be used as the carbonyl source for carboxylation of acetylene to acrylic acid and acrylic esters, and this can remarkably reduce the emissions of exhaust gas, improve the effective use of resources and reduce the environmental pollution. Currently, the acetylene carbonylation reaction is mainly preceeding in homogeneous catalysts, but this process has many problems such as the separation of the catalysts and products, formation of carbon deposit and the corrosion of the equipment caused by acid additives. Hence, these problems associated with the homogeneous catalyst prompted more researches to the development of heterogeneous catalysts. In this paper, different forms of nickel-based catalysts were prepared by incipient wetness impregnation. The catalytic activities for acetylene carboxylation were investigated in 50 ml Parr autoclave and the catalysts were characterized by H2-TPR and BET. In addition, the reaction conditions were optimized. The main conclusions are shown as follows.(1)The active component of the catalyst is metallic nickel. The catalytic activity depents on the precusors and the catalytic activity follows the order: Ni(NO3)2>Ni(AC)2>Ni(Cl)2?Ni(Br)2.Catalyst supports also affect the catalytic activity of metallic nickel with different catalyst dispersion. the catalytic activities of different catalyst supports follows the order: TiO2>SiO2>Al2O3. With the increases of Ni loading amount from 1 to 7 wt.%, the dispersion of active component decreases that shifts the reduction temperature to lower temperatures in H2-TPR. and the catalytic activity firstly increased and then decreased with a maximum at the loading amount of 5 wt.%. The decline of catalytic activity with high Ni loading amount due to the aggregation of nickel atoms on the catalyst support.(2)The addition of triphenylphosphine (PPh3) significantly improved the yield and selectivity of acrylic acid, and the optimal amount is nni:nPPh3=1:2; the addition of HC1 also could improve the yield of methyl acrylate, and the optimal volume of HCl is 0.3 ml.(3)The optimal conditions for acetylene carboxylation to acrylic acid is shown as follows:nni=0.201 mmol, T=200 ?; P0=7.0 MPa, nH2O:nC2H2=2.5,the corresponding results at reaction time of 2 h are obtained:YAA=69.27%, SAA=87.56%,STY=89.39(mol AA)(mol Ni·h)-1.(4)The optimal conditions for acetylene carboxylation to methyl acrylate: nni=0.402 mmol,T=225?; P0=6.0 MPa, the corresponding results at reaction time of 0.5 h are obtained:YMA=23.04%, SMA=73.37%, STY=59.46 (mol MA) (mol Ni·h)-1.