The Study Of Mercury-free Catalysts For The Acetylene Hydrochlorination Reaction

Vinyl chloride is an important raw material for the synthesis of polyvinyl chloride.Its production technology is mainly hydrochlorination of acetylene and ethylene oxychlorination.Because China’s energy structure is multi-coal、less gas and lean oil,Using acetylene to synthesize vinyl chloride monomer has become the mainstream technology in China.At present,Producing vinyl chloride in the reaction of hydrochlorination of acetylene still highly depends on mercury catalyst.But mercury is highly toxic and easy to sublime loss,which has brought great harm to the environment.So,The development of mercury-free catalysts still requires constant efforts.Although the study about mercury-free catalyst has been many years,the research on how to maintain the high activity and stability of the catalyst and how to prolong the service life of the catalyst is still unsatisfactory.So the research about mercury-free catalyst has a strong practical value.Our research group has researched mercury-free catalyst for many years.It was prepared by impregnation method which using activated carbon as the carrier and using transition metal chlorides as active components.On the basis of this,this paper use impregnation method to prepare the mercury-free catalyst by modifying the carrier in advance and selecting different metal chlorides as the active components.Then studying the changes of pore structure and surface chemical properties after the carrier is being modified by nitric acid,citric acid and phosphoric acid.As well as studying the effect of the modification time,the modified concentration,the modifying agent on the catalytic activity of the catalyst.At the same time,we also researched the effect of the types and content of the active components on the catalytic activity of the catalyst.The main conclusions as follows:（1）the catalytic activity of the catalyst is the best while the modified carbon was treated with 5 mol/L nitric acid for 6 h in the progress of modification using different acidic reagents such as nitric acid,citric acid and phosphoric acid.Due to the introduction of a strong polarity of the acidic oxygen-containing functional groups;the conversion can be up to 77%.The activity of CuCl-BiCl₃-M/C catalyst was higher than CeCl₃、NaCl、KCl、CoCl₂ and ZnCl₂ when BaCl₂ was used as additive.When using the basic formula of12wt%CuCl,16wt%BiCl₃,4wt%BaCl₂ as the mercury-free catalyst,the catalytic activity is better and the average conversion of acetylene can reach 66.4%.（2）When adding PdCl₂、RuCl₃、Ag Cl and other precious metals to the catalyst,only ruthenium chloride can significantly increase the activity of the catalyst.silver chloride can only increase the stability of the catalyst,and can not improve the activity.（3）After the optimization of the carrier、the active components、the reaction conditions step by step,while the reaction conditions were carried out under the optimum conditions of pretreatment with 5 mol/L nitric acid for 6 h、Under the reaction temperature of 160℃,space velocity 60 h^-1,V（HCl）/V（C₂H₂）=1.05,The new supported ruthenium composite catalyst prepared by using 12wt%CuCl,16wt%BiCl₃,4wt%BaCl2,1wt%RuCl3 not only reduces the loading of precious metals,but also make the best of its catalytic efficiency.Although the stability is not as good as mercury catalyst,But it can achieve the activity of industrial mercury catalyst about 89.5%.