A series of Zn–Ca–Al oxides with different CaO and ZnO contents have been prepared and evaluated in the synthesis of propylene carbonate(PC) from 1,2-propylene glycol(PG) and urea in a batch reactor. The effect of c...A series of Zn–Ca–Al oxides with different CaO and ZnO contents have been prepared and evaluated in the synthesis of propylene carbonate(PC) from 1,2-propylene glycol(PG) and urea in a batch reactor. The effect of catalyst composition, basicity and reaction process parameters such as temperature, catalyst dose, molar ratio of PG to urea, purge gas flow and reaction time has been studied to find suitable reaction conditions for the PC synthesis. The PC selectivity and yield under the desired conditions could reach 98.4% and 90.8%, respectively. The best performing catalyst also exhibited a good reusability without appreciable loss in the PC selectivity and yield after five consecutive reaction runs. In addition, a stepwise reaction pathway involving a 2-hydroxypropyl carbamate intermediate was proposed for the urea alcoholysis to PC in the presence of Zn–Ca–Al catalysts, according to the time dependences of reaction intermediates and products.展开更多
Vanillin 1, 2-propylene glycol acetal was synthesized from vanillin and 1, 2-propylene glycol using H3PMo6W6O40·nH2O as catalyst, The factors influencing the synthesis were discussed and the better reaction condi...Vanillin 1, 2-propylene glycol acetal was synthesized from vanillin and 1, 2-propylene glycol using H3PMo6W6O40·nH2O as catalyst, The factors influencing the synthesis were discussed and the better reaction conditions were found as follows: The amount of vanillin was 3.8 g, the molar ratio of vanillin was 1, 2-propylene glycol 1.0 to 2.4, the amount of catalyst was 1.6% in proportion to the total reacting materials, the volume ofcyclohexane as the water-carrying agent 4 mL, the refluxing time was 2 h at 88-96℃ and thus the product yield reached over 87%. The results show that the catalyst's activity is high and the reaction time is short.展开更多
The directly selective hydrogenolysis of xylitol to ethylene glycol(EG) and 1,2-propylene glycol(1,2-PDO)was performed on Cu–Ni–ZrO_2 catalysts prepared by a co-precipitation method. Upon optimizing the reaction con...The directly selective hydrogenolysis of xylitol to ethylene glycol(EG) and 1,2-propylene glycol(1,2-PDO)was performed on Cu–Ni–ZrO_2 catalysts prepared by a co-precipitation method. Upon optimizing the reaction conditions(518 K, 4.0 MPaH_2 and 3 h), 97.0% conversion of xylitol and 63.1% yield of glycols were obtained in water without extra inorganic base. The catalyst still remained stable activity after six cycles and above 80% total selectivity of glycols was obtained when using 20.0% xylitol concentration. XRD, TEM and ICP results indicated that Cu–Ni–ZrO_2 catalysts possess favorable stability. Cu and Ni are beneficial to the cleavage of C–O and C–H bond, respectively. To reduce the hydrogen consumption, isopropanol was added as in-situ hydrogen source and 96.4% conversion of xylitol with 43.6% yield of glycols were realized.展开更多
New supported Raney-Cu catalyst was prepared from pseudo-boehmite powder and copper aluminum alloy powder. It could be used in a continuous-flow fixed-bed reactor and it was also a good catalyst for hydrogenolysis of ...New supported Raney-Cu catalyst was prepared from pseudo-boehmite powder and copper aluminum alloy powder. It could be used in a continuous-flow fixed-bed reactor and it was also a good catalyst for hydrogenolysis of glycerol to propylene glycol after the two raw materials were processed by the following procedures: molding, drying, calcination, and leaching. XRD, H2-TPR, as well as SEM technique were employed to study the physicochemical properties of the catalysts, and the hydrogenolysis of glycerol to 1,2-propylene glycol (1,2-PDO) was used as a probe to evaluate the performance of supported skeletal copper catalysts. The test result indicated that CuAl2 was the main crystal phase of precursor after the dried strips were calcined at 850 °C in air. A part of CuAl2 was oxidized to α-Al2O3, which was the main contributor to the strength of Raney-Cu/Al2O3, while the remaining CuAl2 was converted to active skeletal copper after the leaching process. The effects of reaction temperature, hydrogen pressure, LHSV, hydrogen-oil ratio, glycerol concentration, and alkaline additives on the catalytic performance were studied in water or ethanol, respectively. Conversion of glycerol and selectivity of 1,2-PDO were 30.9% and 91.4% in water, or 99.0% and 73.6% in the ethanol system, respectively, when the reaction was performed at a temperature of 215 °C, a H2 pressure of 3 MPa, a LHSV of 1.0 h-1, a hydrogen-oil ratio of 500, and a glycerol concentration of 20%(ethyl alcohol solution).展开更多
基金Supported by the Changcheng Scholars Program of Beijing(CIT&TCD 20150316)
文摘A series of Zn–Ca–Al oxides with different CaO and ZnO contents have been prepared and evaluated in the synthesis of propylene carbonate(PC) from 1,2-propylene glycol(PG) and urea in a batch reactor. The effect of catalyst composition, basicity and reaction process parameters such as temperature, catalyst dose, molar ratio of PG to urea, purge gas flow and reaction time has been studied to find suitable reaction conditions for the PC synthesis. The PC selectivity and yield under the desired conditions could reach 98.4% and 90.8%, respectively. The best performing catalyst also exhibited a good reusability without appreciable loss in the PC selectivity and yield after five consecutive reaction runs. In addition, a stepwise reaction pathway involving a 2-hydroxypropyl carbamate intermediate was proposed for the urea alcoholysis to PC in the presence of Zn–Ca–Al catalysts, according to the time dependences of reaction intermediates and products.
文摘Vanillin 1, 2-propylene glycol acetal was synthesized from vanillin and 1, 2-propylene glycol using H3PMo6W6O40·nH2O as catalyst, The factors influencing the synthesis were discussed and the better reaction conditions were found as follows: The amount of vanillin was 3.8 g, the molar ratio of vanillin was 1, 2-propylene glycol 1.0 to 2.4, the amount of catalyst was 1.6% in proportion to the total reacting materials, the volume ofcyclohexane as the water-carrying agent 4 mL, the refluxing time was 2 h at 88-96℃ and thus the product yield reached over 87%. The results show that the catalyst's activity is high and the reaction time is short.
基金financial supports provided by the National Natural Science Foundation of China (21406255)the Shanghai Science and Technology Committee (16dz1207200)the Youth Innovation Promotion Association CAS (2015231)
文摘The directly selective hydrogenolysis of xylitol to ethylene glycol(EG) and 1,2-propylene glycol(1,2-PDO)was performed on Cu–Ni–ZrO_2 catalysts prepared by a co-precipitation method. Upon optimizing the reaction conditions(518 K, 4.0 MPaH_2 and 3 h), 97.0% conversion of xylitol and 63.1% yield of glycols were obtained in water without extra inorganic base. The catalyst still remained stable activity after six cycles and above 80% total selectivity of glycols was obtained when using 20.0% xylitol concentration. XRD, TEM and ICP results indicated that Cu–Ni–ZrO_2 catalysts possess favorable stability. Cu and Ni are beneficial to the cleavage of C–O and C–H bond, respectively. To reduce the hydrogen consumption, isopropanol was added as in-situ hydrogen source and 96.4% conversion of xylitol with 43.6% yield of glycols were realized.
基金financially supported by the Importation and Development of High-Caliber Talents Project of Beijing Municipal Institutions(CIT&TCD20130325)the Project of Construction of Innovative Teams and Teacher Career Development for Universities and Colleges under Beijing Municipality (IDHT20180508)
文摘New supported Raney-Cu catalyst was prepared from pseudo-boehmite powder and copper aluminum alloy powder. It could be used in a continuous-flow fixed-bed reactor and it was also a good catalyst for hydrogenolysis of glycerol to propylene glycol after the two raw materials were processed by the following procedures: molding, drying, calcination, and leaching. XRD, H2-TPR, as well as SEM technique were employed to study the physicochemical properties of the catalysts, and the hydrogenolysis of glycerol to 1,2-propylene glycol (1,2-PDO) was used as a probe to evaluate the performance of supported skeletal copper catalysts. The test result indicated that CuAl2 was the main crystal phase of precursor after the dried strips were calcined at 850 °C in air. A part of CuAl2 was oxidized to α-Al2O3, which was the main contributor to the strength of Raney-Cu/Al2O3, while the remaining CuAl2 was converted to active skeletal copper after the leaching process. The effects of reaction temperature, hydrogen pressure, LHSV, hydrogen-oil ratio, glycerol concentration, and alkaline additives on the catalytic performance were studied in water or ethanol, respectively. Conversion of glycerol and selectivity of 1,2-PDO were 30.9% and 91.4% in water, or 99.0% and 73.6% in the ethanol system, respectively, when the reaction was performed at a temperature of 215 °C, a H2 pressure of 3 MPa, a LHSV of 1.0 h-1, a hydrogen-oil ratio of 500, and a glycerol concentration of 20%(ethyl alcohol solution).