Carbonylation Of Acetylene To Methyl Acrylate Over Nickel-based Catalyst

Methyl acrylate?MA?is an important chemical raw material with a wide range of uses,generally produced by propylene oxidation.With the continuous development of the economy,the demand for fossil resources is increasing,and a large amount of oil and natural gas needs to be supplemented by imports.The resource characteristics are multi-coal,lean oil,and low gas.Research and development of coal-based chemical production routes can effectively reduce China's dependence on petroleum resources.Another method for synthesizing methyl acrylate in the industry is acetylene carbonylation,which uses acetylene,carbon monoxide and methanol as raw materials to form methyl acrylate.The synthesis of methyl acrylate by acetylene carbonylation is usually carried out under homogeneous conditions.The catalyst and product after the reaction are difficult to separate and recover,which is not conducive to industrial operation.The research and preparation of highly active heterogeneous catalyst can effectively solve this problem.Heterogeneous catalysts for this reaction have been reported less.Most of the research in recent years has focused on the research of synthetic acrylic acid,and little research has been done on methyl acrylate.For these reasons,the paper begins with a homogeneous reaction and liquid phase ion exchange method was used to prepare a highly active heterogeneous catalyst using XRD,N2-BET,NH3-TPD,ICP-AES,XRF,pyridine-infrared and other means for characterization.The content of the paper includes the following three parts:?1?Firstly,based on the homogeneous reaction,the activity of different nickel salt catalysts was investigated and nickel bromide had the highest reactivity.Then,copper auxiliaries,polymerization inhibitors and ligands were investigated.The results show that the addition of a certain amount of copper bromide can significantly increase the activity of the reaction,but copper ions are one of the reasons for the carbon deposition in the reaction.The concentration is about 0.9mmol/L.The polymerization inhibitor hydroquinone can reduce the occurrence of polymerization and increase the selectivity of methyl acrylate;a small amount of acetylacetone can increase the selectivity of methyl acrylate,and excess acetylacetone will cause large particles of black polymer in the reaction.The reaction temperature,reaction pressure and reaction time were investigated.The results show that increasing the temperature can increase the conversion of acetylene,but the selectivity of methyl acrylate is reduced and carbon deposition occurs.The optimum reaction pressure is 5.5MPa and the reaction time is2h.?2?On the basis of homogeneous reaction,we used Y-zeolite as carrier and a series of modified NiY catalysts were prepared by pretreating with different concentrations of sodium hydroxide solution and liquid phase ion exchange.The resulting catalysts were used for synthesizing methyl methacrylate in different conditions and characterized by N₂-BET,NH₃-TPD,ICP-AES,XRF,XRD and pyridine-IR.The results showed that the silica-alumina ratio of the catalysts treated by the alkali solution were slightly decreased,and the specific surface area and pore structure of the catalysts were obviously changed.The pyridine-IR results showed that the amount of total acid and lewis acid were significantly reduced in the catalyst treated with 0.1 mol/L sodium hydroxide solution.The carbonylation reactivity of the catalyst was tested and the results showed when the concentration of the alkali solution was0.1 mol/L,the obtained catalysts had shown the highest activity with 82.33%of selectivity to methyl acrylate and 84.5%of acetylene conversion.?3?Finally,based on the single metal nickel supported molecular sieve,nickel and copper were simultaneously introduced onto the zeolite to prepare a bimetallic supported catalyst.Catalyst characterization results show that the specific surface area and pore volume of the catalyst are significantly reduced after the introduction of copper.The higher the copper content,the smaller the specific surface area of the catalyst.The XRD analysis of the catalyst showed that the introduction of copper ions did not damage the crystal structure of the catalyst itself.The SEM image showed that the addition of copper ions made the block structure on the catalyst surface relatively loose and dispersed;XPS analysis shows that in the nickel-copper bimetallic supported zeolites,nickel ions mainly exist in divalent form,and copper ions mainly exist in zero-valent and monovalent forms.The activity test showed that when the nickel-copper ratio was 1:1/10,the prepared catalyst had the highest activity.Under the optimal reaction conditions,the methyl formate conversion rate was 79.3%,and the methyl acrylate selectivity was 89.54%.