A process for ammoxidation of 2, 4-dichlorotoluene to prepare 2, 4-dichlorobenzonitrile which is a key intermediate of organic synthesis was studied. Having appraised and screened catalysts on an apparatus of umicrore...A process for ammoxidation of 2, 4-dichlorotoluene to prepare 2, 4-dichlorobenzonitrile which is a key intermediate of organic synthesis was studied. Having appraised and screened catalysts on an apparatus of umicroreactor-chromatograghy', the further experiments confirming the catalyst and find-ing the optimum technological conditions were carried out by using a fixed-bed reactor made of quartz (30mm inside diameter). The influence of temperature, the ratio of ammonia, the ratio of air and the space velocity of catalyst upon the conversion, molar yield and selectivity of the reaction were observed, respec-tively. Using catalyst of DC124, on the suitable conditions, the highest conversion is 98. 1 %, molar yield is 89. 5%. The 2, 4-dichlorobenzonitrile obtained is white sheet or needle crystal with the purity hlgher than 99%. The effect of two chlorine atoms at 2, 6 or 2,4 position on the reaction is discussed based on the research of the ammoxidation of 2, 6-dichlorotoluene and 2,4-dichlorotoluene.展开更多
The selective hydrogenation of dimethyl toluene-2,4-dicarbamate(TDC)to methyl cyclohexyl-2,4-dicarbamate(also called hydrogenated TDC,HTDC)is an essential process for non-phosgene synthesis of methylcyclohexane-2,4-di...The selective hydrogenation of dimethyl toluene-2,4-dicarbamate(TDC)to methyl cyclohexyl-2,4-dicarbamate(also called hydrogenated TDC,HTDC)is an essential process for non-phosgene synthesis of methylcyclohexane-2,4-diisocyanate.Herein,we prepared a series of supported Rh-based catalysts by the excessive impregnation method and investigated their catalytic performance for the selective hydrogenation of TDC.The emphasis was put on the influence of support properties on the catalytic performance.Among the prepared catalysts,Rh/g-Al_(2)O_(3)performed the best:a HTDC yield of 88.4%was achieved with a 100%conversion of TDC under the conditions of 100℃,3 MPa and 1 h.Furthermore,Rh/γ-Al_(2)O_(3)could be repetitively used for 4 times without a significant loss of its catalytic activity.TEM,XRD,N_(2)adsorption-desorption,H_(2)-TPR,NH_(3)/CO_(2)-TPD,XPS and ICP characterizations were employed to distinguish the properties of the prepared catalysts and the results were correlated with their catalytic performance.It is indicated that the yield of HTDC shows a positive relevance with the percentage of moderate-to-strong acid sites and the content of Rh^(n+)(n≥3)in the catalysts.High values of the percentage and the content can promote a strong interaction between Rh nanoparticles and the supports,facilitating both the transfer of electrons from Rh to the support and the formation of Rh^(n+)species.This is conducive to activating the benzene ring of TDC and thereby improving the yield of HTDC.展开更多
文摘A process for ammoxidation of 2, 4-dichlorotoluene to prepare 2, 4-dichlorobenzonitrile which is a key intermediate of organic synthesis was studied. Having appraised and screened catalysts on an apparatus of umicroreactor-chromatograghy', the further experiments confirming the catalyst and find-ing the optimum technological conditions were carried out by using a fixed-bed reactor made of quartz (30mm inside diameter). The influence of temperature, the ratio of ammonia, the ratio of air and the space velocity of catalyst upon the conversion, molar yield and selectivity of the reaction were observed, respec-tively. Using catalyst of DC124, on the suitable conditions, the highest conversion is 98. 1 %, molar yield is 89. 5%. The 2, 4-dichlorobenzonitrile obtained is white sheet or needle crystal with the purity hlgher than 99%. The effect of two chlorine atoms at 2, 6 or 2,4 position on the reaction is discussed based on the research of the ammoxidation of 2, 6-dichlorotoluene and 2,4-dichlorotoluene.
基金financially supported by National Natural Science Foundation of China(U21A20306,21978066)Hebei Province Fig.7.Reaction mechanism of selective hydrogenation of TDC over Rh-based catalysts.Graduate Innovation Funding Project(CXZZBS2023033).
文摘The selective hydrogenation of dimethyl toluene-2,4-dicarbamate(TDC)to methyl cyclohexyl-2,4-dicarbamate(also called hydrogenated TDC,HTDC)is an essential process for non-phosgene synthesis of methylcyclohexane-2,4-diisocyanate.Herein,we prepared a series of supported Rh-based catalysts by the excessive impregnation method and investigated their catalytic performance for the selective hydrogenation of TDC.The emphasis was put on the influence of support properties on the catalytic performance.Among the prepared catalysts,Rh/g-Al_(2)O_(3)performed the best:a HTDC yield of 88.4%was achieved with a 100%conversion of TDC under the conditions of 100℃,3 MPa and 1 h.Furthermore,Rh/γ-Al_(2)O_(3)could be repetitively used for 4 times without a significant loss of its catalytic activity.TEM,XRD,N_(2)adsorption-desorption,H_(2)-TPR,NH_(3)/CO_(2)-TPD,XPS and ICP characterizations were employed to distinguish the properties of the prepared catalysts and the results were correlated with their catalytic performance.It is indicated that the yield of HTDC shows a positive relevance with the percentage of moderate-to-strong acid sites and the content of Rh^(n+)(n≥3)in the catalysts.High values of the percentage and the content can promote a strong interaction between Rh nanoparticles and the supports,facilitating both the transfer of electrons from Rh to the support and the formation of Rh^(n+)species.This is conducive to activating the benzene ring of TDC and thereby improving the yield of HTDC.
