Preparation And Research Of Mercury-free Low Ruthenium Catalysts Modified By Several Nitrogen-containing Compounds

It is meaningful to design and develop eco-friendly and efficient catalysts to replace traditional Hg catalysts in the vinyl chloride industry,which is because of the the sublimation and the loss of mercuric chloride,causing serious environmental pollution in acetylene hydrochlorination to produce vinyl chloride.In this paper,a series of low Ru catalysts（the mass of Ru is 0.25 wt%）were developed by impregnation method,which were further modified by ammonium oxalate,ammonium oxalate and phosphoric acid,ammonium persulfate,N,N-dimethylformamide.Characterizations like XRD,BET,TG,SEM,TEM,TPR,XPS were also conducted in this paper and the comprehensive analysis results are as follows:（1）A series of low Ru catalysts modified by ammonium oxalate were developed and used for acetylene hydrochlorination process under T=150℃,GHSV=1122 h^-1,V_HCl:V_C2H2=1.15.The conversion of acetylene was 38%over Ru/AC,but the conversion of acetylene can increase 52%over the catalyst modified by 10%ammonium oxalate（Ru-10%NCO/AC）,and there was a 90%acetylene conversion,which is higher than commercial high and low Hg catalyst.Ru-10%NCO/AC also had the highest TOF value(84.53 min^-1).The results of ventilation order testing showed that catalytic with excellent performance when HCl is pretreated.The results of characterizations indicated that the anti-carbon deposition,the disparity of Ru on the catalyst surface,the amount of active specie Ru⁴⁺could enhance,the formation of metal Ru could be reduced after modifying with ammonium oxalate.Additionally,quaterary N as the active N specie also played an important role.What’s more,Ru-10%NCO/AC was further modified by adding phosphoric acid and changing the coconut carbon in coal-based carbon,which was developed as a lower Ru containing catalyst（0.08%Ru-10%NCO 4%P/C）.After 500h sideline single tube test in the real world,it also shows an excellent catalytic performance.（2）The low Ru catalyst was further modified by different masses of ammonium persulfate.Among them,when the mass of ammonium persulfate was 7 wt%（Ru-7%SN/AC）,the catalyst showed the optimal catalytic performance and there was an 87%acetylene conversion,which was 49%higher than that of Ru/AC.The characterizations showed that the ammonium persulfate could enhance the holes on the surface of active carbon and active specie Ru⁴⁺,and reduced the anti-carbon deposition and formation of metal Ru.Moreover,the pyridinic N、quaternary N and oxidized sulfur groups（-C-SOx-C-）in the catalyst also played important roles during the process.（3）N,N-dimethylformamide was also used to modify Ru/AC,and catalyst modified by 5%of N,N-dimethylformamide（Ru-5%N,N/AC）exhibited the most excellent catalytic performance,and the acetylene conversion could reach up to 85%,which was 47%higher than that of Ru/AC.The results of characterizations indicated that the enhancement of catalytic performance ascribed to the increase of active specie Ru⁴⁺and inhabitants of carbon deposition and metal Ru formation.Additionally,pyrrolic N as the active N specie also played an important role.