The Study On CH₄/CO₂/H₂O Bi-reforming For Ethylene Glycol Synthesis

The process of CH₄/CO₂/H₂ O bi-reforming to syn-gas combined steam and carbon dioxide reforming of methane,the essence of which are dramatic endothermic reactions.Thermodynamically,high temperature facilitates both the conversion of CH₄ and CO₂ and the carbon deposition.As a reactant,H₂ O plays the role to modulate the H₂/CO ratio and inhibit the carbon formation.The CH₄/CO₂/H₂ O bi-reforming can make a material contribution to sequestering carbon dioxide,an important step toward utilizing the greenhouse gas as a energy resource.Thermodynamic simulation results for the CH₄/CO₂/H₂ O bi-reforming show that a value of H₂/CO ratio 1.9².1 with the effective gas content?H₂+CO?/% beyond 90%,CH₄ conversion exceeds 90%,the content of methane in syn-gas under 1% desired for ethylene glycol?EG?synthesis is achieved at 950 ?,2.0 MPa,the feed composition CO₂/CH₄=0.4⁰.8,H₂O/CH₄=0.8¹.2.Under these conditions,a series of catalysts for the CH₄/CO₂/H₂ O bi-reforming prepared with the impregnating method and based on the previous studies of our laboratory were investigated to meet the requirements for EG synthesis.The activity tests were conducted on a fix-bed stainless steel reactor,Gas chromatography?GC?is used for the product analyzing.Then,a stability experiment of 1000 hours was made to evaluate the selected catalyst's performance with time on stream.Moreover,O₂-TPO,CO₂-TPD,XRD and TPSR were used to Micro-structure analysis.The results of 1000 hours CH₄/CO₂/H₂ O bi-reforming stability experiment illustrate that the conversion of methane exceeds 93%,the conversion of carbon dioxide surpasses 53%,the content of the syngas production of?H₂+CO?approximates 90% and H₂/CO molar ratio is 1.89².08.However,the average carbon deposition is about 2500 ppm?O₂-TPO?.Assistant X was adopted into the catalyst to improve the coke situation,a 50 hours of CH₄/CO₂/H₂ O bi-reforming stability experiment and united temperature programming surface reaction with O₂-TPO were done to test the X modified catalyst.It is evident that assistant X promote the carbon resistance of the catalyst,there always existing carbon deposition under 600 ? and 700 ?.The mechanism of bi-reforming is investigated by steady state isotopic transient mechanismic analysis?SSITA?.The results show that H₂ O molecular would break down to H₂ and surface NiO in high temperature when there existing enough Ni.CO₂ could exchage oxygen atom with surface NiO while CH₄ could react directly with the oxygen atom in the surface NiO.