Login In
2018 Volume 46 Issue 7
2018, 46(7): 769-777
Abstract:
Naomaohu sub-bituminous (NS) with weak reducibility and Buliangou sub-bituminous (BS) with strong reducibility were extracted in isometric carbon disulfide/acetone mixed solvent to get extracts and extraction residues (ERs). The ERs were thermal dissolved in cyclohexane and methanol to get soluble portions (SPs). The yields of the extracts from NS (ENS) and BS (EBS) are 10.6% and 8.0%, respectively, and the total yields of the SPs from NS and BS at 300℃ are 36.3% and 11.5%, respectively, indicating the solubility of the organic species in NS are better than that in BS. Arenes are the dominated compounds both in ENS and EBS. The relative contents of aliphatic hydrocarbons and phenols in the SPs of NS are obvious higher than those of BS. The molecular weight distribution of the compounds in ENS is wider than that in EBS, while the molecular weight distribution of the compounds in the SPs from NS is narrower than that from BS.
Naomaohu sub-bituminous (NS) with weak reducibility and Buliangou sub-bituminous (BS) with strong reducibility were extracted in isometric carbon disulfide/acetone mixed solvent to get extracts and extraction residues (ERs). The ERs were thermal dissolved in cyclohexane and methanol to get soluble portions (SPs). The yields of the extracts from NS (ENS) and BS (EBS) are 10.6% and 8.0%, respectively, and the total yields of the SPs from NS and BS at 300℃ are 36.3% and 11.5%, respectively, indicating the solubility of the organic species in NS are better than that in BS. Arenes are the dominated compounds both in ENS and EBS. The relative contents of aliphatic hydrocarbons and phenols in the SPs of NS are obvious higher than those of BS. The molecular weight distribution of the compounds in ENS is wider than that in EBS, while the molecular weight distribution of the compounds in the SPs from NS is narrower than that from BS.
2018, 46(7): 778-786
Abstract:
In order to understand the effects of solvent pretreatment on the inherent macromolecular structure of low rank coal, Xilinguole lignite (XLL) and Shenfu sub-bituminous coal (SFC) were extracted by tetrahydrofuran (THF) soxhlet extraction, carbon disulfide/N-methyl-2-pyrrolidone (CS2/NMP) mixed solvent extraction and thermal dissolution, respectively. The extracted coals were characterized by diffuse reflection FT-IR spectroscopy (DRIFT), thermogravimetric analysis (TGA), mercury intrusion method (MI) and swelling ratio determination. The results indicated that the extraction resulted in the arrangement and reassociation of coal inherent macromolecules. THF Soxhlet extraction and CS2/NMP mixed solvent extraction can relax the macromolecular structure of coal to varying degrees by changing the non-covalent bond cross-linking, especially the distribution of hydrogen bond interactions. However, thermal dissolutions at high temperature mainly increased the covalent cross linking of coal macromolecules, especially for XLL. Swelling of all extracted coals was limited by Fickian diffusion, and the extracted coal showed lower swelling activation energy than the corresponding raw coals.
In order to understand the effects of solvent pretreatment on the inherent macromolecular structure of low rank coal, Xilinguole lignite (XLL) and Shenfu sub-bituminous coal (SFC) were extracted by tetrahydrofuran (THF) soxhlet extraction, carbon disulfide/N-methyl-2-pyrrolidone (CS2/NMP) mixed solvent extraction and thermal dissolution, respectively. The extracted coals were characterized by diffuse reflection FT-IR spectroscopy (DRIFT), thermogravimetric analysis (TGA), mercury intrusion method (MI) and swelling ratio determination. The results indicated that the extraction resulted in the arrangement and reassociation of coal inherent macromolecules. THF Soxhlet extraction and CS2/NMP mixed solvent extraction can relax the macromolecular structure of coal to varying degrees by changing the non-covalent bond cross-linking, especially the distribution of hydrogen bond interactions. However, thermal dissolutions at high temperature mainly increased the covalent cross linking of coal macromolecules, especially for XLL. Swelling of all extracted coals was limited by Fickian diffusion, and the extracted coal showed lower swelling activation energy than the corresponding raw coals.
2018, 46(7): 871-878
Abstract:
Various graphitic carbon nitride (g-C3N4) materials having nitrogen defects were synthesized by adding NaHCO3 during the thermal polymerization of melamine. The as-prepared g-C3N4 samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), nitrogen adsorption-desorption, X-ray photoelectron spectroscopy (XPS), UV-visual diffuse reflectance spectroscopy (UV-vis DRS) and photoluminescence spectroscopy (PL); their photocatalytic activity in the degradation of Rhodamine B (RhB) under visible light irradiation was investigated. The results demonstrated that the unique nitrogen defects in g-C3N4 play an important role in broadening the absorption of visible light and enhancing the separation of electron-hole pairs. The photocatalytic activity of g-C3N4 with nitrogen defects is enhanced greatly; the RhB removal rates over the CNK0.005, CNK0.01, and CNK0.05 photocatalysts in 30 min reach 79.8%, 100.0% and 87.6%, respectively. In contrast, the pristine g-C3N4 free of nitrogen defects only gives an RhB degration rate of 59.8% under the same reaction conditions.
Various graphitic carbon nitride (g-C3N4) materials having nitrogen defects were synthesized by adding NaHCO3 during the thermal polymerization of melamine. The as-prepared g-C3N4 samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), nitrogen adsorption-desorption, X-ray photoelectron spectroscopy (XPS), UV-visual diffuse reflectance spectroscopy (UV-vis DRS) and photoluminescence spectroscopy (PL); their photocatalytic activity in the degradation of Rhodamine B (RhB) under visible light irradiation was investigated. The results demonstrated that the unique nitrogen defects in g-C3N4 play an important role in broadening the absorption of visible light and enhancing the separation of electron-hole pairs. The photocatalytic activity of g-C3N4 with nitrogen defects is enhanced greatly; the RhB removal rates over the CNK0.005, CNK0.01, and CNK0.05 photocatalysts in 30 min reach 79.8%, 100.0% and 87.6%, respectively. In contrast, the pristine g-C3N4 free of nitrogen defects only gives an RhB degration rate of 59.8% under the same reaction conditions.
2018, 46(7): 787-795
Abstract:
High temperature stage microscope was applied to observe morphology evolution of flaky char particles during gasification. Raman spectroscopy was used to analyze crystalline structures of gasification semicoke. Effect of gasification temperature (1000-1200℃) and initial equivalent diameter (1.00-1.60 mm) on morphology and structure evolution were examined. The results show that particle shrinkage in later stage of gasification is more intense than that in early stage. Within tested gasification temperature, the particle ASR (area shrinkage ratio) and VSR (volumetric shrinkage ratio) decrease with increasing temperature. The initial particle size of char has a significant effect on particle shrinkage. At 1100℃ the shrinkage trend of particle marks a turning point at initial diameter of 1.30 mm. The variation of char apparent density is dominated by carbon consumption. When the carbon conversion reaches 80%, the apparent density ratio linearly decreases below 0.4. At the same gasification temperature, with increasing carbon conversion the graphitization of char reduces first and then increases, while the amorphous carbon is opposite.
High temperature stage microscope was applied to observe morphology evolution of flaky char particles during gasification. Raman spectroscopy was used to analyze crystalline structures of gasification semicoke. Effect of gasification temperature (1000-1200℃) and initial equivalent diameter (1.00-1.60 mm) on morphology and structure evolution were examined. The results show that particle shrinkage in later stage of gasification is more intense than that in early stage. Within tested gasification temperature, the particle ASR (area shrinkage ratio) and VSR (volumetric shrinkage ratio) decrease with increasing temperature. The initial particle size of char has a significant effect on particle shrinkage. At 1100℃ the shrinkage trend of particle marks a turning point at initial diameter of 1.30 mm. The variation of char apparent density is dominated by carbon consumption. When the carbon conversion reaches 80%, the apparent density ratio linearly decreases below 0.4. At the same gasification temperature, with increasing carbon conversion the graphitization of char reduces first and then increases, while the amorphous carbon is opposite.
2018, 46(7): 796-801
Abstract:
Direct coal liquefaction residue (DCLR) is deashed by hydrochloric acid and hydrofluoric acid to obtain ACLR. The ACLR was extracted with n-hexane, toluene and tetrahydrofuran to obtain n-hexane insoluble matter (HCLR), toluene insoluble matter (TCLR), tetrahydrofuran insoluble (FCLR). The surface properties of ACLR, HCLR, TCLR and FCLR were characterized by inverse gas chromatography (IGC). Based on net residual volume Vn of the non-polar probe, surface dispersion free energy were calculated by Dorris-Gray and Schultz method respectively. The adsorption enthalpy △Hsp of the polar probe on surface of the 4 insoluble solids was obtained by Vn of the polar probe, and the acid constant Ka and the base constant Kb of the 4 insoluble solids were calculated by △Hsp. The results show that the surface dispersion free energy of ACLR are obviously changed after solvent extraction, and the dispersion free energy on surface of the 4 insoluble solids is decreasing from 60 to 100℃. By Kb/Ka> 1 and △Hsp analysis, 4 insoluble solids surfaces are both amphoteric and the alkaline effect is stronger than that of the acid effect. As a kinetic adsorption technique, IGC can quickly and accurately characterize change of surface properties of DCLR during fractionated extraction. At the same temperature the surface dispersion free energy obtained by the Dorris-Gray method is slightly higher than that by the Schultz method.
Direct coal liquefaction residue (DCLR) is deashed by hydrochloric acid and hydrofluoric acid to obtain ACLR. The ACLR was extracted with n-hexane, toluene and tetrahydrofuran to obtain n-hexane insoluble matter (HCLR), toluene insoluble matter (TCLR), tetrahydrofuran insoluble (FCLR). The surface properties of ACLR, HCLR, TCLR and FCLR were characterized by inverse gas chromatography (IGC). Based on net residual volume Vn of the non-polar probe, surface dispersion free energy were calculated by Dorris-Gray and Schultz method respectively. The adsorption enthalpy △Hsp of the polar probe on surface of the 4 insoluble solids was obtained by Vn of the polar probe, and the acid constant Ka and the base constant Kb of the 4 insoluble solids were calculated by △Hsp. The results show that the surface dispersion free energy of ACLR are obviously changed after solvent extraction, and the dispersion free energy on surface of the 4 insoluble solids is decreasing from 60 to 100℃. By Kb/Ka> 1 and △Hsp analysis, 4 insoluble solids surfaces are both amphoteric and the alkaline effect is stronger than that of the acid effect. As a kinetic adsorption technique, IGC can quickly and accurately characterize change of surface properties of DCLR during fractionated extraction. At the same temperature the surface dispersion free energy obtained by the Dorris-Gray method is slightly higher than that by the Schultz method.
2018, 46(7): 802-808
Abstract:
Both Cu/SiO2-sol and Cu/SiO2-aer catalysts were prepared by the ammonia evaporation method using silicon sol and aerosil as silicon sources, respectively. The catalysts were characterized by N2 adsorption-desorption, XRD, FT-IR, TEM, N2O-H2 titration, H2-TPR, NH3-TPD and XPS. The catalytic performances of Cu/SiO2 catalysts for hydrogenation of furfural to produce 2-methylfuran were investigated in a fixed bed reactor. Compared with Cu/SiO2-aer catalyst, the Cu/SiO2-sol catalyst exhibits a higher catalytic performance. The conversion of furfural is 100% and the selectivity of 2-methylfuran is above 91% during the reaction of 150 h. CuO/SiO2-sol catalyst favors the formation of rich copper phyllosilicate phase, which could provide more weak acid sites and better Cu dispersion on the surface of Cu/SiO2-sol catalyst. Besides, the larger pore size of Cu/SiO2-sol contributes to reducing the carbon deposition, which is beneficial to long service life of the catalyst.
Both Cu/SiO2-sol and Cu/SiO2-aer catalysts were prepared by the ammonia evaporation method using silicon sol and aerosil as silicon sources, respectively. The catalysts were characterized by N2 adsorption-desorption, XRD, FT-IR, TEM, N2O-H2 titration, H2-TPR, NH3-TPD and XPS. The catalytic performances of Cu/SiO2 catalysts for hydrogenation of furfural to produce 2-methylfuran were investigated in a fixed bed reactor. Compared with Cu/SiO2-aer catalyst, the Cu/SiO2-sol catalyst exhibits a higher catalytic performance. The conversion of furfural is 100% and the selectivity of 2-methylfuran is above 91% during the reaction of 150 h. CuO/SiO2-sol catalyst favors the formation of rich copper phyllosilicate phase, which could provide more weak acid sites and better Cu dispersion on the surface of Cu/SiO2-sol catalyst. Besides, the larger pore size of Cu/SiO2-sol contributes to reducing the carbon deposition, which is beneficial to long service life of the catalyst.
2018, 46(7): 809-817
Abstract:
Ni2P/ZrO2-SBA-15(n) and Ni2P/ZrO2-SBA-15(m) catalysts were prepared from n-propoxide zirconium (n) and Zr(SO4)2(m) as zirconium sources. The catalysts were characterized by X-ray diffraction (XRD), N2 adsorption specific surface area measurements (BET), CO uptake, X-ray photoelectron spectroscopy (XPS) and NH3 temperature programmed desorption (NH3-TPD). The results show that after Zr modification, a new layered structure of ZrP is formed. The introduction of Zr helps to generate more Ni2P active phase with smaller crystal size, and increase both the acid strength and acid amount of the catalyst. Compared with zirconium n-propoxide, the catalyst prepared from Zr(SO4)2 has larger specific surface area, more acid amount, stronger acidity, more ZrP phases, smaller Ni2P crystal grains and more Ni active sites. The product yields of benzofuran hydrodeoxygenation (BF HDO) given by Ni2P/ZrO2-SBA-15(n) and Ni2P/ZrO2-SBA-15(m) were 71.5% and 85.9% respectively, which were increased by 14.0% and 28.4% respectively compared with Ni2P/SBA-15. The BF HDO activity, selectivity and yield of the BF HDO products decreased in the order of Ni2P/ZrO2-SBA-15(m) > Ni2P/ZrO2-SBA-15(n) > Ni2P/SBA-15.
Ni2P/ZrO2-SBA-15(n) and Ni2P/ZrO2-SBA-15(m) catalysts were prepared from n-propoxide zirconium (n) and Zr(SO4)2(m) as zirconium sources. The catalysts were characterized by X-ray diffraction (XRD), N2 adsorption specific surface area measurements (BET), CO uptake, X-ray photoelectron spectroscopy (XPS) and NH3 temperature programmed desorption (NH3-TPD). The results show that after Zr modification, a new layered structure of ZrP is formed. The introduction of Zr helps to generate more Ni2P active phase with smaller crystal size, and increase both the acid strength and acid amount of the catalyst. Compared with zirconium n-propoxide, the catalyst prepared from Zr(SO4)2 has larger specific surface area, more acid amount, stronger acidity, more ZrP phases, smaller Ni2P crystal grains and more Ni active sites. The product yields of benzofuran hydrodeoxygenation (BF HDO) given by Ni2P/ZrO2-SBA-15(n) and Ni2P/ZrO2-SBA-15(m) were 71.5% and 85.9% respectively, which were increased by 14.0% and 28.4% respectively compared with Ni2P/SBA-15. The BF HDO activity, selectivity and yield of the BF HDO products decreased in the order of Ni2P/ZrO2-SBA-15(m) > Ni2P/ZrO2-SBA-15(n) > Ni2P/SBA-15.
2018, 46(7): 818-825
Abstract:
The adsorption and the mechanism for selective hydrogenation of cinnamaldehyde (CAL) on Pt (111) surface and Pt14 cluster were investigated by using density functional theory (DFT). The results illustrate that the synergistic adsorption of CAL molecule on Pt (111) surface with C=O and C=C bonds is most stable at the Hcp position, whereas most stable adsorption of CAL appears on the Pt14 cluster with C=C bond; the adsorption of CAL on the Pt14 cluster is stronger than that on Pt(111) surface. The reaction barriers for each elementary reaction were determined from the transition state search and the results suggest that CAL was preferentially hydrogenated at C=O on the Pt(111) surface and Pt14 cluster, forming cinnamyl alcohol (COL); the hydrogenation of O atom takes the priority. Both Pt plate and cluster have good selectivity for hydrogenation of CAL to COL. The reaction barrier of CAL hydrogenation on Pt(111) surface is lower than that on Pt14 cluster, indicating that the catalytic activity and selectivity of CAL hydrogenation are closely related to the structure of Pt catalysts; Pt(111) surface is more favorable for catalyzing the hydrogenation of CAL to COL.
The adsorption and the mechanism for selective hydrogenation of cinnamaldehyde (CAL) on Pt (111) surface and Pt14 cluster were investigated by using density functional theory (DFT). The results illustrate that the synergistic adsorption of CAL molecule on Pt (111) surface with C=O and C=C bonds is most stable at the Hcp position, whereas most stable adsorption of CAL appears on the Pt14 cluster with C=C bond; the adsorption of CAL on the Pt14 cluster is stronger than that on Pt(111) surface. The reaction barriers for each elementary reaction were determined from the transition state search and the results suggest that CAL was preferentially hydrogenated at C=O on the Pt(111) surface and Pt14 cluster, forming cinnamyl alcohol (COL); the hydrogenation of O atom takes the priority. Both Pt plate and cluster have good selectivity for hydrogenation of CAL to COL. The reaction barrier of CAL hydrogenation on Pt(111) surface is lower than that on Pt14 cluster, indicating that the catalytic activity and selectivity of CAL hydrogenation are closely related to the structure of Pt catalysts; Pt(111) surface is more favorable for catalyzing the hydrogenation of CAL to COL.
2018, 46(7): 826-834
Abstract:
Zn/HZSM-5 zeolites, with zinc contents of 1%, 2%, and 3%, were prepared by impregnation method and characterized by XRD, N2 adsorption, NH3-TPD, Py-FTIR, XPS, and TG-DTA techniques to investigate the deactivation mechanism in ethylene aromatization reaction. It shows that coking is the main reason for catalysts deactivation, which is considerably depressed with the presence of Zn in the HZSM-5 catalysts. The deactivation is slow for the catalysts with low Zn loading. However, high content of Zn in the catalysts brings in problems such as decrease of surface area and microporous volume, and hence accelerates the deactivation. In the reaction, zinc species lose from the catalysts, accompanied with the migration and redistribution of Zn from bulk to surface of zeolite. The losing rate was constant with the time on stream, but influenced by the zinc content of the catalyst. ZnO on the external surface of the catalyst are the main species leaching from zeolite. Zn leaching is accelerated with the increase of zinc content, and has correlation with coking rate to some extent.
Zn/HZSM-5 zeolites, with zinc contents of 1%, 2%, and 3%, were prepared by impregnation method and characterized by XRD, N2 adsorption, NH3-TPD, Py-FTIR, XPS, and TG-DTA techniques to investigate the deactivation mechanism in ethylene aromatization reaction. It shows that coking is the main reason for catalysts deactivation, which is considerably depressed with the presence of Zn in the HZSM-5 catalysts. The deactivation is slow for the catalysts with low Zn loading. However, high content of Zn in the catalysts brings in problems such as decrease of surface area and microporous volume, and hence accelerates the deactivation. In the reaction, zinc species lose from the catalysts, accompanied with the migration and redistribution of Zn from bulk to surface of zeolite. The losing rate was constant with the time on stream, but influenced by the zinc content of the catalyst. ZnO on the external surface of the catalyst are the main species leaching from zeolite. Zn leaching is accelerated with the increase of zinc content, and has correlation with coking rate to some extent.
2018, 46(7): 835-840
Abstract:
Fe2O3 or FeCu catalysts were prepared by co-precipitation method with or without the assistance of polyvinyl alcohol (PVA). The effect of Cu promoter on the structure and catalytic behaviour of the catalysts were investigated. The catalysts were characterized by BET, SEM, XRD, H2-TPR and FT-IR techniques. The results showed that the addition of Cu promoter could enhance the crystal growth of α-Fe2O3, decrease BET surface area and pore volume and increase pore size and promote the reduction of the catalysts in H2. In addition, Cu promoter remarkably influenced the surface morphology. In Fischer-Tropsch synthesis (FTS) reaction, the catalytic activity was increased when Cu promoter was added only. The addition of Cu promoter and PVA decreased the FTS activity, and shifted the hydrocarbon products to lighter molecular weight.
Fe2O3 or FeCu catalysts were prepared by co-precipitation method with or without the assistance of polyvinyl alcohol (PVA). The effect of Cu promoter on the structure and catalytic behaviour of the catalysts were investigated. The catalysts were characterized by BET, SEM, XRD, H2-TPR and FT-IR techniques. The results showed that the addition of Cu promoter could enhance the crystal growth of α-Fe2O3, decrease BET surface area and pore volume and increase pore size and promote the reduction of the catalysts in H2. In addition, Cu promoter remarkably influenced the surface morphology. In Fischer-Tropsch synthesis (FTS) reaction, the catalytic activity was increased when Cu promoter was added only. The addition of Cu promoter and PVA decreased the FTS activity, and shifted the hydrocarbon products to lighter molecular weight.
2018, 46(7): 841-847
Abstract:
A series of MgAlOx mixed oxides were prepared by calcination of hydrotalcite materials at various temperatures ranging from 400 to 700℃. The physical and chemical properties of the catalysts were characterized by XRD, TG, N2 adsorption/desorption, NH3-TPD, and CO2-TPD techniques. The catalytic activity was evaluated by the condensation of formaldehyde and acetaldehyde. The results show that as the calcination temperatures increase, both the conversion of acetaldehyde and the space time yield of propanal first increase and then decrease, which shows the same trend with the amount of moderate basic sites, and the C-550 catalyst has the maximum of 39.22% and 103.86 g/(kg·h), respectively. Moreover, the yields of by-products including methanol and CO2 are also significantly related to the moderate and strong basic sites.
A series of MgAlOx mixed oxides were prepared by calcination of hydrotalcite materials at various temperatures ranging from 400 to 700℃. The physical and chemical properties of the catalysts were characterized by XRD, TG, N2 adsorption/desorption, NH3-TPD, and CO2-TPD techniques. The catalytic activity was evaluated by the condensation of formaldehyde and acetaldehyde. The results show that as the calcination temperatures increase, both the conversion of acetaldehyde and the space time yield of propanal first increase and then decrease, which shows the same trend with the amount of moderate basic sites, and the C-550 catalyst has the maximum of 39.22% and 103.86 g/(kg·h), respectively. Moreover, the yields of by-products including methanol and CO2 are also significantly related to the moderate and strong basic sites.
2018, 46(7): 848-855
Abstract:
HZSM-35, HZSM-5, HM and Hβ zeolites were used as the catalysts for the skeletal isomerization of 1-hexene; the relationship between their catalytic performance and physicochemical properties was investigated. The results show that in comparison with HZSM-5 and Hβ, HZSM-35 and HM are provided with suitable acid amount and effective pore size between 0.4-0.6 nm, without bug hole and cross channel; as a result, the later two zeolites exhibit better shape selectivity. With a high conversion of 1-hexene (> 95%), the by-products such as C5- and C7+ in the products are about 20% and the yield of iso-hexene reaches 40%-50%. After the acid-base modification treatment, a slight change in the acidity is observed; however, the catalytic performance of one-dimensional HZSM-35 and HM zeolites in pore isomerization is still much better than that of HZSM-5 and Hβ zeolites with multidimensional pore structure, suggesting that the pore structure plays a key role in the isomerization reaction.
HZSM-35, HZSM-5, HM and Hβ zeolites were used as the catalysts for the skeletal isomerization of 1-hexene; the relationship between their catalytic performance and physicochemical properties was investigated. The results show that in comparison with HZSM-5 and Hβ, HZSM-35 and HM are provided with suitable acid amount and effective pore size between 0.4-0.6 nm, without bug hole and cross channel; as a result, the later two zeolites exhibit better shape selectivity. With a high conversion of 1-hexene (> 95%), the by-products such as C5- and C7+ in the products are about 20% and the yield of iso-hexene reaches 40%-50%. After the acid-base modification treatment, a slight change in the acidity is observed; however, the catalytic performance of one-dimensional HZSM-35 and HM zeolites in pore isomerization is still much better than that of HZSM-5 and Hβ zeolites with multidimensional pore structure, suggesting that the pore structure plays a key role in the isomerization reaction.
2018, 46(7): 856-863
Abstract:
The CeUSY zeolites loaded with Ce were prepared by liquid phase ion exchange method, and the Ni contamination was conducted by Mitchell impregnation method. The texture properties were characterized by inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray diffraction (XRD) and N2 adsorption. Moreover, the nickel tolerance was evaluated by the MAT evaluation device. The results show that CeUSY zeolites with different Ce contents possess a nickel tolerance performance varying in a volcano type with the increase of Ce content. Through the H2-TPR and Py-FTIR characterization of CeUSY zeolite before and after Ni contamination, it is evident that the change in Ce species morphology is one of the reasons affecting nickel tolerances. It is thought that the interaction between Ce(OH)2+ and Ni(OH)+ in the SOD cages of the CeUSY zeolite results in a loss of H2O molecule to form a stable Ce3+-O-Ni2+ structure at high temperature, which hinders the combination of Ni species with the framework aluminum to prevent the destruction of the Brønsted acid sites in CeUSY zeolite and effectively inhibits the formation of reducible NiO species. However, with the increase of the content of Ce3+, the part of the introduced Ce would happen to self-assemble in the zeolites as multinuclear hydroxylated species which interacts weakly with Ni2+ species compared to mononuclear species and then reduces the nickel tolerance.
The CeUSY zeolites loaded with Ce were prepared by liquid phase ion exchange method, and the Ni contamination was conducted by Mitchell impregnation method. The texture properties were characterized by inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray diffraction (XRD) and N2 adsorption. Moreover, the nickel tolerance was evaluated by the MAT evaluation device. The results show that CeUSY zeolites with different Ce contents possess a nickel tolerance performance varying in a volcano type with the increase of Ce content. Through the H2-TPR and Py-FTIR characterization of CeUSY zeolite before and after Ni contamination, it is evident that the change in Ce species morphology is one of the reasons affecting nickel tolerances. It is thought that the interaction between Ce(OH)2+ and Ni(OH)+ in the SOD cages of the CeUSY zeolite results in a loss of H2O molecule to form a stable Ce3+-O-Ni2+ structure at high temperature, which hinders the combination of Ni species with the framework aluminum to prevent the destruction of the Brønsted acid sites in CeUSY zeolite and effectively inhibits the formation of reducible NiO species. However, with the increase of the content of Ce3+, the part of the introduced Ce would happen to self-assemble in the zeolites as multinuclear hydroxylated species which interacts weakly with Ni2+ species compared to mononuclear species and then reduces the nickel tolerance.
2018, 46(7): 864-870
Abstract:
A series of nMoOx·HZSM-5 single-phase complexes were prepared by incipient wetness impregnation, and characterized by XRD, NH3-TPD, Py-FTIR, BET and SEM techniques. The n-butane catalytic cracking performance over nMoOx·HZSM-5 was investigated by using a continuous flowing micro reactor. The results indicate that active component Mo is located in the cross of Z form channel and straight channel of HZSM-5 in the form of MoOx clusters to generate a nMoOx·HZSM-5 single-phase complex, causing the contraction of HZSM-5 lattice cell and the reduction in the lattice parameters and cell volume of HZSM-5 as well as the decrease in specific surface area of HZSM-5. The acidity of nMoOx·HZSM-5 shows an increases firstly and then a decrease with the increasing dosage of active component Mo. The n-butane catalytic cracking conversion over nMoOx·HZSM-5-0.75% is 73.83% at reaction temperature of 625℃ and gas space velocity of 5600 h-1, slightly lower than that over HZSM-5. However, the propylene yield over nMoOx·HZSM-5-0.75% reaches 13.13%, 2 percent points higher than that over HZSM-5, exhibiting a better performance on the promotion of propylene yield.
A series of nMoOx·HZSM-5 single-phase complexes were prepared by incipient wetness impregnation, and characterized by XRD, NH3-TPD, Py-FTIR, BET and SEM techniques. The n-butane catalytic cracking performance over nMoOx·HZSM-5 was investigated by using a continuous flowing micro reactor. The results indicate that active component Mo is located in the cross of Z form channel and straight channel of HZSM-5 in the form of MoOx clusters to generate a nMoOx·HZSM-5 single-phase complex, causing the contraction of HZSM-5 lattice cell and the reduction in the lattice parameters and cell volume of HZSM-5 as well as the decrease in specific surface area of HZSM-5. The acidity of nMoOx·HZSM-5 shows an increases firstly and then a decrease with the increasing dosage of active component Mo. The n-butane catalytic cracking conversion over nMoOx·HZSM-5-0.75% is 73.83% at reaction temperature of 625℃ and gas space velocity of 5600 h-1, slightly lower than that over HZSM-5. However, the propylene yield over nMoOx·HZSM-5-0.75% reaches 13.13%, 2 percent points higher than that over HZSM-5, exhibiting a better performance on the promotion of propylene yield.
2018, 46(7): 879-885
Abstract:
The effect of reaction conditions, including temperature, pressure, space velocity and hydrogen to oil ratio, on the hydrogenation of naphthalene to decalin over Ni/Al2O3 catalyst was investigated in a high pressure fixed bed reactor. The results indicate that the conversion of naphthalene and the selectivity to tran-decalin and cis-decalin are closely related to the reaction conditions. The ratio of tran-decalin to cis-decalin increases with an increase in the hydrogen to oil ratio and reaction temperature, but decreases with an increase in the liquid hourly space velocity (LHSV) and reaction pressure. Under a temperature 260-290℃, 5-7 MPa, a LHSV 1-1.5 h-1, and a hydrogen to oil ratio higher than 250, the conversion of naphthalene is 100% and the selectivity to decalin is close to 100%, with a tran-decalin to cis-decalin ratio of about 4.0. Meanwhile, it was found that the sintering and/or loss of active component are the main factors that cause the deactivation of Ni/Al2O3 catalyst in naphthalene hydrogenation and influence the ratio of tran-decalin to cis-decalin in the products.
The effect of reaction conditions, including temperature, pressure, space velocity and hydrogen to oil ratio, on the hydrogenation of naphthalene to decalin over Ni/Al2O3 catalyst was investigated in a high pressure fixed bed reactor. The results indicate that the conversion of naphthalene and the selectivity to tran-decalin and cis-decalin are closely related to the reaction conditions. The ratio of tran-decalin to cis-decalin increases with an increase in the hydrogen to oil ratio and reaction temperature, but decreases with an increase in the liquid hourly space velocity (LHSV) and reaction pressure. Under a temperature 260-290℃, 5-7 MPa, a LHSV 1-1.5 h-1, and a hydrogen to oil ratio higher than 250, the conversion of naphthalene is 100% and the selectivity to decalin is close to 100%, with a tran-decalin to cis-decalin ratio of about 4.0. Meanwhile, it was found that the sintering and/or loss of active component are the main factors that cause the deactivation of Ni/Al2O3 catalyst in naphthalene hydrogenation and influence the ratio of tran-decalin to cis-decalin in the products.
2018, 46(7): 886-890
Abstract:
A series of sodium-magnesium double-salt as CO2 absorption materials with controllable morphologies were prepared by simple mixing method using sodium carboxymethyl cellulose as morphology-directing agent, and then characterized by XRD, SEM and TG. Finally, their CO2 absorption capability was evaluated by both saturation absorption tests at fixed temperature and dynamic absorption-desorption cyclic experiments. A uniform nanosheet-assembled absorbent, with 0.3 g sodium carboxymethyl cellulose added during preparation, can be obtained with a saturated absorption capacity of 22.8%. Meanwhile, good recycling capacity has been maintained at about 9.7% without apparent changes even after 20 cycles of dynamic absorption-desorption experiment.
A series of sodium-magnesium double-salt as CO2 absorption materials with controllable morphologies were prepared by simple mixing method using sodium carboxymethyl cellulose as morphology-directing agent, and then characterized by XRD, SEM and TG. Finally, their CO2 absorption capability was evaluated by both saturation absorption tests at fixed temperature and dynamic absorption-desorption cyclic experiments. A uniform nanosheet-assembled absorbent, with 0.3 g sodium carboxymethyl cellulose added during preparation, can be obtained with a saturated absorption capacity of 22.8%. Meanwhile, good recycling capacity has been maintained at about 9.7% without apparent changes even after 20 cycles of dynamic absorption-desorption experiment.
2018, 46(7): 891-896
Abstract:
The MFI (ZSM-5 and silicate-1) membranes with porous α-Al2O3 substrates were synthesized by secondary growth method. The results of scanning electron microscopy (SEM) and X-ray diffraction (XRD) indicate that the membranes with 5 μm thickness are composed of well-intergrown MFI crystals, which completely covers on the α-Al2O3 substrates in random orientation. The gas permeation measurements reveal that the resulting membranes are of high quality with few non-zeolitic pores. In addition, the separation properties of H2S/CH4 through the synthesized MFI membranes were investigated. Under the osmotic pressure of 0.3 and 0.5 MPa, the separation factors of H2S/CH4 by silicate-1 zeolite membrane are 1.99 and 4.44, and the separation factors of CH4/H2S by ZSM-5 zeolite membrane are 6.71 and 12.85, respectively.
The MFI (ZSM-5 and silicate-1) membranes with porous α-Al2O3 substrates were synthesized by secondary growth method. The results of scanning electron microscopy (SEM) and X-ray diffraction (XRD) indicate that the membranes with 5 μm thickness are composed of well-intergrown MFI crystals, which completely covers on the α-Al2O3 substrates in random orientation. The gas permeation measurements reveal that the resulting membranes are of high quality with few non-zeolitic pores. In addition, the separation properties of H2S/CH4 through the synthesized MFI membranes were investigated. Under the osmotic pressure of 0.3 and 0.5 MPa, the separation factors of H2S/CH4 by silicate-1 zeolite membrane are 1.99 and 4.44, and the separation factors of CH4/H2S by ZSM-5 zeolite membrane are 6.71 and 12.85, respectively.
