The modification of HZSM-5 zeolite with phosphorus and steam has been studied. Results show that 1% phosphorus and steam modified HZSM-5 has the highest catalytic activity for n-heptane. Physicochemical and catalytic ...The modification of HZSM-5 zeolite with phosphorus and steam has been studied. Results show that 1% phosphorus and steam modified HZSM-5 has the highest catalytic activity for n-heptane. Physicochemical and catalytic properties of 1% phosphorus and steam modified HZSM-5 zeolites have been investigated. The X-ray diffraction （XRD） results exhibit that there is considerable variation in the relative intensity of the individual diffraction peaks. The acidity of the samples decreases with an increase in the steaming temperature, which is determined by the IR of adsorbed pyridine and temperature programmed desorption （TPD） of ammonia. The oxidation state of phosphorus shown by XPS is ＋5, and a model for surface structure modification is proposed. The nitrogen adsorption isotherm for all samples is a combination of type I and type IV, all hysteresis loops resemble the H4-type. The density functional and cluster model methods have been invoked to select the phosphorus grafting model, and it was found that the phosphorus grafting model were more probable in the form of the terminal oxygen coordinating with aluminum.展开更多
The deactivation of catalyst is a significant reason for its limited application during the catalytic fast pyrolysis(CFP)process.To reduce the coke formation,binary compound impregnation(BCI)and chemical liquid deposi...The deactivation of catalyst is a significant reason for its limited application during the catalytic fast pyrolysis(CFP)process.To reduce the coke formation,binary compound impregnation(BCI)and chemical liquid deposition(CLD)were used to modify HZSM-5 catalysts.At the same time,the self-designed microwave reactor separated the pyrolysis of bamboo and catalytic upgrading of primary vapor,which made the catalytic effect more thorough.Experimental results indicated that CLD used TiO 2 deposition to cover external acid sites,while BCI by phosphorus-nickel could cover and partly destroy superficial acid sites through two different ways.Within the scope of the loaded amount studied,the yield of aromatic hydrocarbons in the oil phase increased at first and then decreased,while the coke formation reduced continuously.BTX(benzene,toluene and xylene),the most valuable product in bio-oil,drastically increased by 39.1%and 22.6%respectively over the CLD and BCI modified catalysts.Considering the catalytic performance as well as cost,CLD over HZSM-5 has more advantages in the CFP process to upgrade bio-oil.展开更多
A series of HZSM-5 zeolites modified with different amounts of phosphoric acid（P/HZSM-5） was prepared. The physicochemical features of the P/HZSM-5 catalysts were characterized via X-ray diffraction（XRD）, N2 adsor...A series of HZSM-5 zeolites modified with different amounts of phosphoric acid（P/HZSM-5） was prepared. The physicochemical features of the P/HZSM-5 catalysts were characterized via X-ray diffraction（XRD）, N2 adsorption-desorption, NH3-temperatttre programmed desorption（NH3-TPD） and Fourier tranform infrared（FTIR） spectra of the adsorbed pyridine, and the performances of the catalysts for Prins condensation to isoprene from isobutylene and formaldehyde were investigated. The maximum isobutene conversion and isoprene selectivity were 10.3% and 94.6% on the HZSM-5 catalyst with a Si/A1 molar ratio of 600 using 5%（mass fraction） phosphoric acid. The phosphoric acid modification not only modulated the amount of acidic sites but also regulated the acid type. An appropriate amount of weak Lewis and Bronsted acid sites served as the active sites for the condensation of isobutene with formaldehyde, and the strong acid sites could cause side reactions and coke deposition.展开更多
文摘The modification of HZSM-5 zeolite with phosphorus and steam has been studied. Results show that 1% phosphorus and steam modified HZSM-5 has the highest catalytic activity for n-heptane. Physicochemical and catalytic properties of 1% phosphorus and steam modified HZSM-5 zeolites have been investigated. The X-ray diffraction （XRD） results exhibit that there is considerable variation in the relative intensity of the individual diffraction peaks. The acidity of the samples decreases with an increase in the steaming temperature, which is determined by the IR of adsorbed pyridine and temperature programmed desorption （TPD） of ammonia. The oxidation state of phosphorus shown by XPS is ＋5, and a model for surface structure modification is proposed. The nitrogen adsorption isotherm for all samples is a combination of type I and type IV, all hysteresis loops resemble the H4-type. The density functional and cluster model methods have been invoked to select the phosphorus grafting model, and it was found that the phosphorus grafting model were more probable in the form of the terminal oxygen coordinating with aluminum.
基金This work was supported by the National Key R&D Program of China(No.2018YFB1501405)the National Natural Science Fund Program of China(No.51776042).
文摘The deactivation of catalyst is a significant reason for its limited application during the catalytic fast pyrolysis(CFP)process.To reduce the coke formation,binary compound impregnation(BCI)and chemical liquid deposition(CLD)were used to modify HZSM-5 catalysts.At the same time,the self-designed microwave reactor separated the pyrolysis of bamboo and catalytic upgrading of primary vapor,which made the catalytic effect more thorough.Experimental results indicated that CLD used TiO 2 deposition to cover external acid sites,while BCI by phosphorus-nickel could cover and partly destroy superficial acid sites through two different ways.Within the scope of the loaded amount studied,the yield of aromatic hydrocarbons in the oil phase increased at first and then decreased,while the coke formation reduced continuously.BTX(benzene,toluene and xylene),the most valuable product in bio-oil,drastically increased by 39.1%and 22.6%respectively over the CLD and BCI modified catalysts.Considering the catalytic performance as well as cost,CLD over HZSM-5 has more advantages in the CFP process to upgrade bio-oil.
文摘A series of HZSM-5 zeolites modified with different amounts of phosphoric acid（P/HZSM-5） was prepared. The physicochemical features of the P/HZSM-5 catalysts were characterized via X-ray diffraction（XRD）, N2 adsorption-desorption, NH3-temperatttre programmed desorption（NH3-TPD） and Fourier tranform infrared（FTIR） spectra of the adsorbed pyridine, and the performances of the catalysts for Prins condensation to isoprene from isobutylene and formaldehyde were investigated. The maximum isobutene conversion and isoprene selectivity were 10.3% and 94.6% on the HZSM-5 catalyst with a Si/A1 molar ratio of 600 using 5%（mass fraction） phosphoric acid. The phosphoric acid modification not only modulated the amount of acidic sites but also regulated the acid type. An appropriate amount of weak Lewis and Bronsted acid sites served as the active sites for the condensation of isobutene with formaldehyde, and the strong acid sites could cause side reactions and coke deposition.
