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Study On Non-mercury Catalytic Acetylene Hydrochlorination To Produce Vinyl Chloride Monomer (VCM)

Posted on:2011-04-26Degree:DoctorType:Dissertation
Country:ChinaCandidate:S J WangFull Text:PDF
GTID:1101360305969134Subject:Chemical processes
Abstract/Summary:PDF Full Text Request
Vinyl chloride monomer (VCM) is mainly used for synthesis of polyvinyl chloride (PVC), one of the five engineering plastics, which is widely used in all walks of life. Currently, there are mainly two synthesis methods for vinyl chloride monomer, which are acetylene hydrochlorination and ethylene oxychlorination. In our country, about 70% of vinyl chloride monomer products are produced from the acetylene hydrochlorination. This is determined by our special energy structure. In China, petroleum resources are scarce, while coal resources are relatively rich, which provide adequate acetylene materials for the acetylene hydrochlorination. However, poisonous activated carbon supported HgCl2 catalyst has been used in this process. The toxicity and volatility of the catalyst causes serious damage to the workers and environment. It is a great challenge for the whole chlor-alkali industry to eliminate or reduce the pollution caused by the catalyst.In this paper, our research is oriented with the development of a green catalytic process, aiming to develop an efficient non-mercury catalyst. Combining with various characterization and simulation calculation methods, a green catalytic process of the acetylene hydrochlorination based on non-mercury catalyst to produce vinyl chloride monomer is developed successfully.PdCl2, CuCl2 and AuCl3 are discovered to be active to the acetylene hydrochlorination. Catalytic performance and deactivation of monocomponent PdCl2, CuCl2 and AuCl3 catalysts are studied in detail using several characterization methods. The results showed that monocomponent catalysts are not favorable for the catalytic acetylene hydrochlorination reaction. With the aim to improve the catalytic performance, two-component catalysts of PdCl2-CuCl2/C, PdCl2-AuCl3/C and AuCl3-CuCl2/C are prepared and their activities for the acetylene hydrochlorination are investigated. It was indicated that activated carbon supported AuCl3-CuCl2 catalyst with Au/Cu=1:6 is not only highly active but also fairly stable. Its microscopic property is characterized using several analysis methods.The thermodynamics of acetylene hydrochlorination was studied. The thermodynamic characteristics the acetylene hydrochlorination were discussed. The equilibrium conversion and favorable reaction temperature were obtained. On the basis of the results of thermodynamics calculation, the catalytic performance of AuCl3-CuCl2/C catalyst under various temperatures, feed ratios, space velocities and reation atmospheres were investigated in detail. The optimized reaction conditions were obtained: temperature is no less than 140-170℃, feed ratio of HCl/C2H2 is around 1.15, total gas hourly space velocity is in the range of 100-150h-1.The mechanism of the acetylene hydrochlorination was explored using the DFT theoretical calculation. The optimized strucutures of reactants, transition complexes, intermediate products and products were obtained and the possible reaction mechamism was proposed. Moreover, the interation between CuCl2 and AuCl3 was explored by the calculation of molecular orbital.Kinetic model of the acetylene hydrochlorination based on the AuCl3-CUCl2/C catalyst was studied in a fixed-bed integral reactor. On the basis of the results of DFT theoretical calculation, the acetylene hydrochlorination was proposed to follow the Eley-Rideal reaction mechanism mode. The kinetics equation was derived based on the Langmuir adsorption model. After the internal and external diffusion were eliminated, the change of conversion with the space velocity under different reaction temperature point was investigated. The reaction kinetic equation was finally obtained by fitting kinetic data. The acetylene hydrochlorination in a fixed-bed microreactor was simulated using Pseudo-homogeneous modal and the distribution of concentration and temperature were investigated.The stability of AuCl3-CUCl2/C catalyst under various condition disturbances were studied in detail. The life of AuCl3-CUCl2/C catalyst was tested under the optimized reaction conditions. The results obtained indicated that the AuCl3-CUCl2/C catalyst was stable with the disturbance of temperature (15-180℃) and space velocity (120-480h"1), but sensitive to feed ratio of HCl/C2H2 and the purity of acetylene. Under the reaction conditions of T=160℃, P=0.1 MPa, GHSV=110h"1, C2H2/HC1=1:1.15, the life of the catalyst is more than 1200h. After 1200h reaction, further deactivation test under a big space velocity (3000h-1) was carried out. The deactivation and regeneration of AuCl3-CuCl2/C catalyst was studied in detail and a practical regeneration method was proposed. In the end, the cost of the acetylene hydrochlorination based on the AuCl3-CUCl2/C catalyst was evaluated.
Keywords/Search Tags:Acetylene hydrochlorination, Non-mercury catalyst, Kinetics, Stability, Deactivation
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