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Kinetics and Mechanisms of hydrogenation of DMO. Li Siming 2012.9.8. C. Perego, S. Peratello, Catalysis Today 1999, 52 , 133-145. Internal Diffusion Effects. 当. 小于 0.1(0.15) 时,可认为无内扩散影响。. External Diffusion Effects. C. Perego, S. Peratello, Catalysis Today 1999, 52 , 133-145. 当.
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Kinetics and Mechanisms of hydrogenation of DMO Li Siming 2012.9.8
C. Perego, S. Peratello, Catalysis Today 1999, 52, 133-145. Internal Diffusion Effects
当 小于0.1(0.15)时,可认为无内扩散影响。
External Diffusion Effects C. Perego, S. Peratello, Catalysis Today 1999, 52, 133-145.
当 小于0.05时,可认为无外扩散影响。
CH3O C C OCH3 + H2 (A) H (MG) (ME) OH (B) H (EG) (E) CH3CH2OH+ H2O Pathway of DMO hydrogenation OH OH O O O OH OH O O OH OH OH OH OH OH O Cu/SiO2 Cu/SiO2 Cu/SiO2 Cu/SiO2 Cu/SiO2 CH3O C C OCH3 + H2 CH3O C CH2+ CH3OH CH3O C CH2 + H2 CH3O C CH2 H2C CH2 + CH3OH CH3O C C OCH3 CH3O C CH2 + H2 H2C CH2 + H2 H OH
ME* ( MG* Et* EG* MG + * ) Et + * ME + * EG + * H2 + 2# 2H # DMO * + 2 H# A* + 2# (1) A* + 2H# + * MG* + 2# + ME* (2) B* +2 # (3) MG* + 2H# B* + 2H# + * EG* + ME* + 2# (4) EG* + 2H# Et* + H2O + 2# (5) Ester un-dissociative adsorption Hydrogen dissociatively adsorb on the active site: DMO * DMO + * #, *: Different active site
Hydrogen un-dissociative adsorption Hydrogen un-dissociatively adsorb on the active site: This way is similar to hydrogen dissociative. The rate control step may be Hydrogen adsorption, surface(1~4) or ester adsorption. Using (1+KHpH) instead of in the rate expression. When the rate is is determined by the un-dissociative adsorption of hydrogen, the rate expression is:
H2 + 2# 2H # CH3OOCC*O +OCH3 * (1) DMO + 2* A B CH3OOCC*O+ 3H# CH3OOCC*H2OH (MG)+ 3# (2) MG + * (3) MG* MG + 2* HOCH2C*O +OCH3 * (4) HOCH2C*H2OH + 3# (5) HOCH2C*O +3H# EG* + 2H# Et* + H2O + 2# (7) OCH3 * + H# ME* + # (6) ME* ME + * EG + * EG* Et* Et + * Pathway of ester dissociative adsorption C #, *: Different active site
H2 + 2# 2H # CH3OOCC*O +OCH3 * (9) DMO + 2* CH3OOCC*OH+ # (1) CH3OOCC*O + H# CH3OOCC*OH+ H# CH3OOCC*HOH+ # (2) CH3OOCC*HOH+ H# CH3OOCC*H2OH(MG)+ # (3) MG + * (7) MG* MG + 2* HOCH2C*O +OCH3 * (8) HOCH2C*OH + # (4) HOCH2C*O +H# HOCH2C*HOH + # (5) HOCH2C*OH +H# EG* + 2H# Et* + H2O + 2# OCH3 * + H# ME* + # (10) ME* ME + * EG + * EG* Et* Et + * The most possible pathway #, *: Different active site HOCH2C*H2OH + # (6) HOCH2C*HOH +H#
Summary of model of DMO hydrogenation Control step ① DMO adsorption DMO dissociative adsorption ② H2 adsorption ③ Surface reaction7 kinds 23 kinds ④adsorption/desorption of intermediate-MG ① ester adsorption H2 molecular adsorption ② H2 adsorption ③ Surface reaction 4 kinds DMO molecular adsorption H2 dissociative adsorption ① ester adsorption ② H2 adsorption ③ Surface reaction 4 kinds
Catalytic performance 表1 25/27日催化剂评价表 表2 设备维修前下催化剂评价表
Work plan 1.Finish the work about elimination of External/ Internal Diffusion effects 2. Measure the intrinsic reaction rate and select the most possible model. ①. Reaction rate and adsorption equilibrium constant must higher than > 0; ② Activation energy can not be below zero. ③ Reaction rate constant and adsorption equilibrium constant must satisfy the Arrhenius and Van’t Hoff equation; ④ A close correlation with experiment data. 3. Think about further verification of mechanism after kinetics experiment.
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