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2020 Volume 48 Issue 8
2020, 48(8): 897-907
Abstract:
The interaction between coal and biomass has been widely investigated. However, the mechanism is always proposed based on physicochemical structure and reactivity of char mixture. In this work, char mixture after co-pyrolysis of anthracite and biomass was separated based on different shape and size, and then structure and reactivity of the coal char were analyzed to reveal mechanism of coal-biomass interaction. Anthracite char samples with different corn straw (CS) blending ratios were prepared by pyrolysis in a fixed bed reactor at 600 and 900℃. The AAEM concentration and microcrystalline structures of coal char were examined by inductively coupled plasma-optical emission spectrometry (ICP-OES) system and X-ray diffraction (XRD). The gasification reactivity of char sample after separation was analyzed by TGA under CO2. The results show that concentration of active K and Mg in coal char samples gradually increased and more disordered carbon structure formed as the CS proportion in the blending increased from 0 to 80%. The coal char in the blending captured more AAEM species by volatile-char interactions instead of escaping with volatile from biomass during co-pyrolysis process. Meanwhile, higher pyrolysis temperature led to volatilization and inactivation of K and Na, and also decrease in graphitization degree. Moreover, both addition of CS and low pyrolysis temperature could promote gasification reactivity of coal char sample. Furthermore, a satisfactory linear correlation (R2=0.9009) between alkali index AI and R0.5 of the char samples was established. This indicated that AAEMs performed the dominate effect to enhance gasification reactivity of coal char during co-gasification of coal and biomass.
The interaction between coal and biomass has been widely investigated. However, the mechanism is always proposed based on physicochemical structure and reactivity of char mixture. In this work, char mixture after co-pyrolysis of anthracite and biomass was separated based on different shape and size, and then structure and reactivity of the coal char were analyzed to reveal mechanism of coal-biomass interaction. Anthracite char samples with different corn straw (CS) blending ratios were prepared by pyrolysis in a fixed bed reactor at 600 and 900℃. The AAEM concentration and microcrystalline structures of coal char were examined by inductively coupled plasma-optical emission spectrometry (ICP-OES) system and X-ray diffraction (XRD). The gasification reactivity of char sample after separation was analyzed by TGA under CO2. The results show that concentration of active K and Mg in coal char samples gradually increased and more disordered carbon structure formed as the CS proportion in the blending increased from 0 to 80%. The coal char in the blending captured more AAEM species by volatile-char interactions instead of escaping with volatile from biomass during co-pyrolysis process. Meanwhile, higher pyrolysis temperature led to volatilization and inactivation of K and Na, and also decrease in graphitization degree. Moreover, both addition of CS and low pyrolysis temperature could promote gasification reactivity of coal char sample. Furthermore, a satisfactory linear correlation (R2=0.9009) between alkali index AI and R0.5 of the char samples was established. This indicated that AAEMs performed the dominate effect to enhance gasification reactivity of coal char during co-gasification of coal and biomass.
2020, 48(8): 960-969
Abstract:
The dimethyl ether (DME) carbonylation reaction over mordenite is greatly affected by the mass transfer process. In this research, hierarchical mordenite catalysts were synthesized and characterized to investigate the influence of mesopores on the structure, mass transfer and catalytic performance. The results show that the medium-strong acid sites decrease while strong acid sites increase over the hierarchical samples. The introduced mesopores can significantly improve the mass transfer efficiency and the carbonylation performances are markedly improved on the hierarchical samples. In addition, the polymerization degree of coke deposition on the deactivated samples decreases although the coke amount increases. Excessive usage of mesopore templates can damage the structure of the MOR catalysts, thus leading to the loss of acid sites and the decrease in catalytic performance.
The dimethyl ether (DME) carbonylation reaction over mordenite is greatly affected by the mass transfer process. In this research, hierarchical mordenite catalysts were synthesized and characterized to investigate the influence of mesopores on the structure, mass transfer and catalytic performance. The results show that the medium-strong acid sites decrease while strong acid sites increase over the hierarchical samples. The introduced mesopores can significantly improve the mass transfer efficiency and the carbonylation performances are markedly improved on the hierarchical samples. In addition, the polymerization degree of coke deposition on the deactivated samples decreases although the coke amount increases. Excessive usage of mesopore templates can damage the structure of the MOR catalysts, thus leading to the loss of acid sites and the decrease in catalytic performance.
2020, 48(8): 1015-1024
Abstract:
Platinum-silver alloy nanoparticles (PtxAgy NPs) were synthesized in a molten salt system without using any organic surfactants or solvents; the catalytic role of Ag in the methanol electrooxidation reaction (MOR) in alkaline electrolyte over PtxAgy NPs was investigated. The TEM images suggest that Pt52Ag48 nanotubes (NTs) can be obtained when the Pt/Ag ratio in the molten salt precursor reaches 1. The methanol electrooxidation reaction test results indicate that the Pt52Ag48 NTs with a clean surface exhibits a much better catalytic performance than the conventional Pt black in MOR. Meanwhile, the catalytic activity of the Pt52Ag48 NTs is greatly related to the positive potential limit; the peak current of MOR reaches 1.61 mA/μgPt with a positive potential limit from -1.0 to 0.5 V (vs. SCE), which is 1.92 times higher than that with a positive potential limit from -1.0 to 0.1 V (vs. SCE). The Ag element in the surface layer of PtxAgy alloy may promote the MOR through a redox process during the electrochemical cycle. The insight shown in work should be beneficial to the application of PtxAgy alloy in the direct methanol fuel cells (DMFCs).
Platinum-silver alloy nanoparticles (PtxAgy NPs) were synthesized in a molten salt system without using any organic surfactants or solvents; the catalytic role of Ag in the methanol electrooxidation reaction (MOR) in alkaline electrolyte over PtxAgy NPs was investigated. The TEM images suggest that Pt52Ag48 nanotubes (NTs) can be obtained when the Pt/Ag ratio in the molten salt precursor reaches 1. The methanol electrooxidation reaction test results indicate that the Pt52Ag48 NTs with a clean surface exhibits a much better catalytic performance than the conventional Pt black in MOR. Meanwhile, the catalytic activity of the Pt52Ag48 NTs is greatly related to the positive potential limit; the peak current of MOR reaches 1.61 mA/μgPt with a positive potential limit from -1.0 to 0.5 V (vs. SCE), which is 1.92 times higher than that with a positive potential limit from -1.0 to 0.1 V (vs. SCE). The Ag element in the surface layer of PtxAgy alloy may promote the MOR through a redox process during the electrochemical cycle. The insight shown in work should be beneficial to the application of PtxAgy alloy in the direct methanol fuel cells (DMFCs).
2020, 48(8): 908-919
Abstract:
Flue gas desulphurized slag was collected as the raw material and purified using the multiple steps of sour purification procedures, which was further prepared as CaSO4 oxygen carrier (OC). Reaction characteristics of the purified desulphurized slag OC with the selected lignite as well as release of the different gaseous sulfur species from the CaSO4 side reactions were investigated on in a lab-scale fixed bed reactor. Several main influencing factors, including reaction temperature, OC excess number Φ and the cycle numbers, were focused. The experimental results indicated that the purified CaSO4 OC was of high reactivity and promising to be applied in the coal-fueled chemical looping combustion process as OC. Furthermore, according to the pros and cons of the three influencing factors on the carbon conversion versus the gaseous sulfur release, the optimized reaction conditions were determined as 900℃ and the OC excess number around 1.0. Finally, under this optimized reaction condition, the effect of the cycle numbers was evaluated and found that the continuous release of gaseous sulfur from the CaSO4 side reactions deteriorated the reactivity of the purified CaSO4 OC and its reaction stability was diminished with the five cycles.
Flue gas desulphurized slag was collected as the raw material and purified using the multiple steps of sour purification procedures, which was further prepared as CaSO4 oxygen carrier (OC). Reaction characteristics of the purified desulphurized slag OC with the selected lignite as well as release of the different gaseous sulfur species from the CaSO4 side reactions were investigated on in a lab-scale fixed bed reactor. Several main influencing factors, including reaction temperature, OC excess number Φ and the cycle numbers, were focused. The experimental results indicated that the purified CaSO4 OC was of high reactivity and promising to be applied in the coal-fueled chemical looping combustion process as OC. Furthermore, according to the pros and cons of the three influencing factors on the carbon conversion versus the gaseous sulfur release, the optimized reaction conditions were determined as 900℃ and the OC excess number around 1.0. Finally, under this optimized reaction condition, the effect of the cycle numbers was evaluated and found that the continuous release of gaseous sulfur from the CaSO4 side reactions deteriorated the reactivity of the purified CaSO4 OC and its reaction stability was diminished with the five cycles.
2020, 48(8): 920-928
Abstract:
The migration and transformation of N in zigzag char-N with the presence of high concentration NO in the reduction zone is investigated by quantum chemistry method. Transformation characteristics of N in lean oxygen environment are systematically calculated from the molecular level by constructing a char-N model containing a hydroxyl group. The results show that NO in the reduction zone can combine with N in the char to form N2; and the presence of oxygen enhances the char chemical activity and further promotes the release of N in the char. The co-existence of oxygen and NO in the reduction zone makes the release of N and the combustion of C occur simultaneously, which is manifested by NO and N in the char combining to form N2, and at the same time oxygen and C in the char formation CO2 or CO. The kinetic calculations of the rate-limiting step rate constants of the C combustion products show that C is easily oxidized to CO under low temperature and lean oxygen conditions, and with the temperature rise the CO2 generation rate increases significantly and the high temperature is conducive to CO2 formation.
The migration and transformation of N in zigzag char-N with the presence of high concentration NO in the reduction zone is investigated by quantum chemistry method. Transformation characteristics of N in lean oxygen environment are systematically calculated from the molecular level by constructing a char-N model containing a hydroxyl group. The results show that NO in the reduction zone can combine with N in the char to form N2; and the presence of oxygen enhances the char chemical activity and further promotes the release of N in the char. The co-existence of oxygen and NO in the reduction zone makes the release of N and the combustion of C occur simultaneously, which is manifested by NO and N in the char combining to form N2, and at the same time oxygen and C in the char formation CO2 or CO. The kinetic calculations of the rate-limiting step rate constants of the C combustion products show that C is easily oxidized to CO under low temperature and lean oxygen conditions, and with the temperature rise the CO2 generation rate increases significantly and the high temperature is conducive to CO2 formation.
2020, 48(8): 929-936
Abstract:
The effects of combustion temperature and biomass blending ratio on the release of K, the occurrence form of K in the ash and the change of mineral matter were studied. It is found that combustion temperature has a significant effect on the release of K. At 600-750℃, with an increase in temperature, water-soluble K and NH4Ac-soluble K are released to the gas phase, which makes the release ratio of K fast; while at 750-850℃, water-soluble K and NH4Ac-soluble K begin to convert into other forms of K and are fixed in the ash sample, which makes the release rate of K slow; when the temperature is higher than 850℃, as the temperature increases, the decomposition of HCl-soluble K causes the release rate of K increase again. Through XRD analysis, it is found that the water-soluble K in ash mainly exists in the form of KCl. The production of K2SO4 is affected by both the K content in the raw material and the S/Cl ratio, the higher the content of K in raw materials, and the greater the ratio of S/Cl, the more it will promote the formation of K2SO4. At the same time, it is also found that there is a synergistic effect between biomass and coal combustion. The elements such as Al, Si in coal may react with K in biomass to generate alkaline aluminosilicate, resulting in more K remaining in the ash.
The effects of combustion temperature and biomass blending ratio on the release of K, the occurrence form of K in the ash and the change of mineral matter were studied. It is found that combustion temperature has a significant effect on the release of K. At 600-750℃, with an increase in temperature, water-soluble K and NH4Ac-soluble K are released to the gas phase, which makes the release ratio of K fast; while at 750-850℃, water-soluble K and NH4Ac-soluble K begin to convert into other forms of K and are fixed in the ash sample, which makes the release rate of K slow; when the temperature is higher than 850℃, as the temperature increases, the decomposition of HCl-soluble K causes the release rate of K increase again. Through XRD analysis, it is found that the water-soluble K in ash mainly exists in the form of KCl. The production of K2SO4 is affected by both the K content in the raw material and the S/Cl ratio, the higher the content of K in raw materials, and the greater the ratio of S/Cl, the more it will promote the formation of K2SO4. At the same time, it is also found that there is a synergistic effect between biomass and coal combustion. The elements such as Al, Si in coal may react with K in biomass to generate alkaline aluminosilicate, resulting in more K remaining in the ash.
2020, 48(8): 937-941
Abstract:
The physical properties and structure composition of FCC slurry and its extraction products were analyzed and characterized using light Daqing FCC slurry as feedstock and complex extraction solvent prepared by N, N-dimethylformamide (DMF) and anti-extractant. The results show that FCC slurry can be better separated into extract oil mainly composed of aromatics and raffinate oil mainly composed of saturates by complex solvent. The aromatics content of extract oil is 80.5% and the aromatic-carbon ratio is 73.82% under extract oil yield 58.5%. The extract oil can be used as raw materials for rubber filling oil and plasticizer, which mainly are composed of aromatics with bicyclic, tricyclic and tetracyclic. The raffinate oil can be used as FCC feedstock, which contains more than 90% saturates and almost without heteroatoms. Solvent extraction can efficiently use the low additional value FCC slurry.
The physical properties and structure composition of FCC slurry and its extraction products were analyzed and characterized using light Daqing FCC slurry as feedstock and complex extraction solvent prepared by N, N-dimethylformamide (DMF) and anti-extractant. The results show that FCC slurry can be better separated into extract oil mainly composed of aromatics and raffinate oil mainly composed of saturates by complex solvent. The aromatics content of extract oil is 80.5% and the aromatic-carbon ratio is 73.82% under extract oil yield 58.5%. The extract oil can be used as raw materials for rubber filling oil and plasticizer, which mainly are composed of aromatics with bicyclic, tricyclic and tetracyclic. The raffinate oil can be used as FCC feedstock, which contains more than 90% saturates and almost without heteroatoms. Solvent extraction can efficiently use the low additional value FCC slurry.
2020, 48(8): 942-948
Abstract:
A series of Ce-modified Ru/HAP catalysts with different loadings were prepared by impregnation method, which were applied to the one-step preparation of 2, 5-furandicarboxylic acid with fructose. The catalysts were characterized by XRD, TEM, NH3-TPD and XPS. The results showed that Ce was highly dispersed on the HAP, and the addition of Ce affected little on the structure of HAP. Ce mainly exists in the form of Ce3+ and Ce4+. The presence of the Ce3+ makes a large amount of oxygen holes on the surface of the catalyst, and the electron transfer between Ce3+ and Ce4+ is conducive to the formation of oxygen holes, improves the oxygen storage capacity and the surface catalytic activity. The catalyst is rich in weak acid sites, which inhibits the side reactions. Among the catalysts evaluated, the sample of Ce (8%, mass ratio) -Ru/HAP showed satisfied performance with the 2, 5-FDCA yield of 34.2% at 160℃ for 4 h reaction under a pressure of 2 MPa and a catalyst dosage of 0.1 g. Therefore, the introduction of Ce has greatly improved the catalytic activity of traditional precious metal composite catalysts, and also provided new ideas for the one-step preparation of fructose 2, 5-FDCA.
A series of Ce-modified Ru/HAP catalysts with different loadings were prepared by impregnation method, which were applied to the one-step preparation of 2, 5-furandicarboxylic acid with fructose. The catalysts were characterized by XRD, TEM, NH3-TPD and XPS. The results showed that Ce was highly dispersed on the HAP, and the addition of Ce affected little on the structure of HAP. Ce mainly exists in the form of Ce3+ and Ce4+. The presence of the Ce3+ makes a large amount of oxygen holes on the surface of the catalyst, and the electron transfer between Ce3+ and Ce4+ is conducive to the formation of oxygen holes, improves the oxygen storage capacity and the surface catalytic activity. The catalyst is rich in weak acid sites, which inhibits the side reactions. Among the catalysts evaluated, the sample of Ce (8%, mass ratio) -Ru/HAP showed satisfied performance with the 2, 5-FDCA yield of 34.2% at 160℃ for 4 h reaction under a pressure of 2 MPa and a catalyst dosage of 0.1 g. Therefore, the introduction of Ce has greatly improved the catalytic activity of traditional precious metal composite catalysts, and also provided new ideas for the one-step preparation of fructose 2, 5-FDCA.
2020, 48(8): 949-959
Abstract:
La2Zr2O7 catalyst was prepared using co-precipitation method and then calcined at different temperatures to obtain a series of catalysts with different phase structures. Their catalytic performances for oxidative coupling of methane were evaluated in a fixed bed micro-reactor. Meanwhile, the changes of phase structure, surface base sites and surface oxygen species upon these samples were characterized with XRD, Raman, CO2-TPD, and XPS. With the increase of the calcination temperature from 700 to 1200℃, the crystallinity of La2Zr2O7 catalysts increased continuously and the crystal phase changed obviously. The structure of the catalysts gradually changed from amorphous to disordered defective fluorite structure, and ultimately to phrochlore structure. Both the number of medium basic sites and the electrophilic oxygen species, such as O22- and O2-, on the catalysts decreased with the phase transition caused by the temperature raising, resulting in the decrease of CH4 conversion and C2+ selectivity. The amorphous LZO-CP-700 catalyst showed the best performance in methane oxidation coupling reaction.
La2Zr2O7 catalyst was prepared using co-precipitation method and then calcined at different temperatures to obtain a series of catalysts with different phase structures. Their catalytic performances for oxidative coupling of methane were evaluated in a fixed bed micro-reactor. Meanwhile, the changes of phase structure, surface base sites and surface oxygen species upon these samples were characterized with XRD, Raman, CO2-TPD, and XPS. With the increase of the calcination temperature from 700 to 1200℃, the crystallinity of La2Zr2O7 catalysts increased continuously and the crystal phase changed obviously. The structure of the catalysts gradually changed from amorphous to disordered defective fluorite structure, and ultimately to phrochlore structure. Both the number of medium basic sites and the electrophilic oxygen species, such as O22- and O2-, on the catalysts decreased with the phase transition caused by the temperature raising, resulting in the decrease of CH4 conversion and C2+ selectivity. The amorphous LZO-CP-700 catalyst showed the best performance in methane oxidation coupling reaction.
2020, 48(8): 970-979
Abstract:
A series of H-ZSM-5 zeolites with different morphologies including spherical, hollow, sheet and sponge-strip forms were hydrothermally synthesized through elaborately controlling the synthesis conditions and their crystal structural, textural and acidic properties were characterized by XRD, SEM, Py-FTIR, NH3-TPD, ICP and N2-sorption. The H-ZSM-5 zeolites of different morphologies and a spinel ZnCr2O4 oxide were then used to compose the bifunctional ZnCr2O4/H-ZSM-5 catalysts for the direct conversion of syngas into aromatics (STA). The effect of H-ZSM-5 morphology on the catalytic performance of ZnCr2O4/H-ZSM-5 in STA was then investigated. The results indicate that the morphology of H-ZSM-5 zeolites has significant influences on the catalytic performance of ZnCr2O4/H-ZSM-5 in STA.The selectivity to aromatics over the bifunctional catalysts with different H-ZSM-5 morphologies follows the order of sphere > sponge-strip > hollow > sheet. In particular, the ZnCr2O4/H-ZSM-5(sphere) catalyst composed of ZnCr2O4 and spherical H-ZSM-5 exhibits excellent performance in STA; under 350℃ and 3.0 MPa, a high selectivity of 68.8% to aromatics is achieved, with a CO conversion of 12.6%, whereas the selectivities to CH4, C2-40 alkanes and CO2 decrease to 1.3%, 14.3% and 41.4%, respectively. The isotropic and moderate particle size (about 350 nm) with appropriate pore length of spherical H-ZSM-5 zeolite are capable of avoiding the formation of lower hydrocarbons from early diffusion out of the acid zeolite channels and meanwhile yet conducive to the diffusion of aromatics, which can promote the aromatization of intermediates in STA and enhance the selectivity to aromatic products.
A series of H-ZSM-5 zeolites with different morphologies including spherical, hollow, sheet and sponge-strip forms were hydrothermally synthesized through elaborately controlling the synthesis conditions and their crystal structural, textural and acidic properties were characterized by XRD, SEM, Py-FTIR, NH3-TPD, ICP and N2-sorption. The H-ZSM-5 zeolites of different morphologies and a spinel ZnCr2O4 oxide were then used to compose the bifunctional ZnCr2O4/H-ZSM-5 catalysts for the direct conversion of syngas into aromatics (STA). The effect of H-ZSM-5 morphology on the catalytic performance of ZnCr2O4/H-ZSM-5 in STA was then investigated. The results indicate that the morphology of H-ZSM-5 zeolites has significant influences on the catalytic performance of ZnCr2O4/H-ZSM-5 in STA.The selectivity to aromatics over the bifunctional catalysts with different H-ZSM-5 morphologies follows the order of sphere > sponge-strip > hollow > sheet. In particular, the ZnCr2O4/H-ZSM-5(sphere) catalyst composed of ZnCr2O4 and spherical H-ZSM-5 exhibits excellent performance in STA; under 350℃ and 3.0 MPa, a high selectivity of 68.8% to aromatics is achieved, with a CO conversion of 12.6%, whereas the selectivities to CH4, C2-40 alkanes and CO2 decrease to 1.3%, 14.3% and 41.4%, respectively. The isotropic and moderate particle size (about 350 nm) with appropriate pore length of spherical H-ZSM-5 zeolite are capable of avoiding the formation of lower hydrocarbons from early diffusion out of the acid zeolite channels and meanwhile yet conducive to the diffusion of aromatics, which can promote the aromatization of intermediates in STA and enhance the selectivity to aromatic products.
2020, 48(8): 980-985
Abstract:
The CuAl2O4 catalytic material was in-situ synthesized using γ-Al2O3 as raw material. The catalytic material was characterized by XRF, XRD, BET and H2-TPR. The effect of the copper-aluminum molar ratios on the structure and properties of CuAl2O4 spinel catalytic material and its performance in hydrogen production from methanol steam reforming were investigated. The results show that the copper-aluminum molar ratios affects reduction performance of copper species, which affects its performance in catalyzing methanol steam reforming to produce hydrogen. When the copper-aluminum molar ratios is 1:2, CuAl2O4 catalytic material has better catalytic performance. When the reaction temperature is 260℃, with a water-methanol molar ratio of 1.2 and methanol gas hourly space velocity of 800 h-1, the methanol conversion reaches 100%, the hydrogen production rate is 895 mL/(kg·s).
The CuAl2O4 catalytic material was in-situ synthesized using γ-Al2O3 as raw material. The catalytic material was characterized by XRF, XRD, BET and H2-TPR. The effect of the copper-aluminum molar ratios on the structure and properties of CuAl2O4 spinel catalytic material and its performance in hydrogen production from methanol steam reforming were investigated. The results show that the copper-aluminum molar ratios affects reduction performance of copper species, which affects its performance in catalyzing methanol steam reforming to produce hydrogen. When the copper-aluminum molar ratios is 1:2, CuAl2O4 catalytic material has better catalytic performance. When the reaction temperature is 260℃, with a water-methanol molar ratio of 1.2 and methanol gas hourly space velocity of 800 h-1, the methanol conversion reaches 100%, the hydrogen production rate is 895 mL/(kg·s).
2020, 48(8): 986-992
Abstract:
ZSM-5 zeolite was modified by Fenton's reagent, FeSO4 and H2O2 aqueous solutions using impregnation method, respectively. All these catalysts were characterized by XRD, ICP-OES, N2 adsorption-desorption, NH3-TPD, Py-FTIR and evaluated in propene oligomerization process. The results demonstrated that the framework of the parent ZSM-5 was well preserved after modification with Fenton's reagent, FeSO4 or H2O2 solutions. However, the SiO2/Al2O3 ratios for all the modified ZSM-5 samples increased due to the dealumination. Furthermore, Fe was detected in Fenton-ZSM-5 while no Fe was observed for FeSO4-ZSM-5 catalyst. The BET surface areas and total pore volumes of three modified catalysts significantly increased compared with the original ZSM-5 sample. Among them, the BET surface area of the Fenton-ZSM-5 increased by 17.86%.The increase of mesopores was probably caused by the removal of the residual organic template in the catalysts due to the generation of·OH radicals by Fenton's reagent and H2O2. The Fenton-ZSM-5 catalyst formed new acid sites of Brønsted (B) and Lewis (L) with little change in the total calculated amount, which significantly changed the B/L ratio. Compared with the parent ZSM-5, the Fenton-ZSM-5 catalyst exhibited the best activity and stability for propene oligomerization reaction. The initial propene conversion and diesel selectivity were as high as 98.3% and 92.4%, respectively, and kept at >80% and >82% for about 24 h, respectively.
ZSM-5 zeolite was modified by Fenton's reagent, FeSO4 and H2O2 aqueous solutions using impregnation method, respectively. All these catalysts were characterized by XRD, ICP-OES, N2 adsorption-desorption, NH3-TPD, Py-FTIR and evaluated in propene oligomerization process. The results demonstrated that the framework of the parent ZSM-5 was well preserved after modification with Fenton's reagent, FeSO4 or H2O2 solutions. However, the SiO2/Al2O3 ratios for all the modified ZSM-5 samples increased due to the dealumination. Furthermore, Fe was detected in Fenton-ZSM-5 while no Fe was observed for FeSO4-ZSM-5 catalyst. The BET surface areas and total pore volumes of three modified catalysts significantly increased compared with the original ZSM-5 sample. Among them, the BET surface area of the Fenton-ZSM-5 increased by 17.86%.The increase of mesopores was probably caused by the removal of the residual organic template in the catalysts due to the generation of·OH radicals by Fenton's reagent and H2O2. The Fenton-ZSM-5 catalyst formed new acid sites of Brønsted (B) and Lewis (L) with little change in the total calculated amount, which significantly changed the B/L ratio. Compared with the parent ZSM-5, the Fenton-ZSM-5 catalyst exhibited the best activity and stability for propene oligomerization reaction. The initial propene conversion and diesel selectivity were as high as 98.3% and 92.4%, respectively, and kept at >80% and >82% for about 24 h, respectively.
2020, 48(8): 993-1003
Abstract:
With the goal of conversion of alkylphenols to light aromatics (benzene and toluene), Cr2O3/Al2O3 catalysts were prepared and their hydrogenation performance was investigated using 4-ethylphenol as a model compound. With the increase of LHSV, H2/oil, reaction pressure and temperature, the dealkylation rate, the total selectivity of aromatics, and the selectivity of light aromatics first rose and then dropped. The conversion of 4-ethylphenol was obviously influenced by the reaction temperature. Cr2O3/Al2O3 was modified with different concentrations of phosphoric acid. As the increase of the amount of phosphoric acid, the general amount of weak and medium acids on the catalyst increased, and the strength of acid was first enhanced and then weakened. The amount of weak acid increased significantly under a high value of the amount of phosphoric acid. Compared with the unmodified catalyst, the conversion of 4-ethylphenol on the catalysts modified by 8% phosphoric acid is higher than 99.5%, while the dealkylation rate of 4-ethylphenol increased by 9.4%, reaching to 74.4%, and the selectivity to light aromatics (benzene and toluene) increased by 4.0%, reaching to 57.0%. Conversion of 4-ethylphenol to light aromatics was achieved in high selectivity. Furthermore, the total selectivity of aromatics was as high as 80.4%, which meant that most of the aromatic rings was not broken. The path of hydrogenation reaction of 4-ethylphenol on Cr2O3/Al2O3 was proposed and the reaction mechanism was discussed.
With the goal of conversion of alkylphenols to light aromatics (benzene and toluene), Cr2O3/Al2O3 catalysts were prepared and their hydrogenation performance was investigated using 4-ethylphenol as a model compound. With the increase of LHSV, H2/oil, reaction pressure and temperature, the dealkylation rate, the total selectivity of aromatics, and the selectivity of light aromatics first rose and then dropped. The conversion of 4-ethylphenol was obviously influenced by the reaction temperature. Cr2O3/Al2O3 was modified with different concentrations of phosphoric acid. As the increase of the amount of phosphoric acid, the general amount of weak and medium acids on the catalyst increased, and the strength of acid was first enhanced and then weakened. The amount of weak acid increased significantly under a high value of the amount of phosphoric acid. Compared with the unmodified catalyst, the conversion of 4-ethylphenol on the catalysts modified by 8% phosphoric acid is higher than 99.5%, while the dealkylation rate of 4-ethylphenol increased by 9.4%, reaching to 74.4%, and the selectivity to light aromatics (benzene and toluene) increased by 4.0%, reaching to 57.0%. Conversion of 4-ethylphenol to light aromatics was achieved in high selectivity. Furthermore, the total selectivity of aromatics was as high as 80.4%, which meant that most of the aromatic rings was not broken. The path of hydrogenation reaction of 4-ethylphenol on Cr2O3/Al2O3 was proposed and the reaction mechanism was discussed.
2020, 48(8): 1004-1014
Abstract:
A series of boron doped reduced graphene oxide catalysts were prepared and applied to anthracene hydrogenation. The results show that, with the change of the treatment temperature of the catalyst, the ordered carbon structure in the catalyst changed and boron replaced the carbon in the material skeleton, which affected the adsorption and activation of anthracene and hydrogen. After boron doping, the catalyst showed higher activity for anthracene hydrogenation reaction, the highest conversion of anthracene was up to 97%, and the highest selectivity of deep hydrogenation product octahydroanthracene was up to 19%.
A series of boron doped reduced graphene oxide catalysts were prepared and applied to anthracene hydrogenation. The results show that, with the change of the treatment temperature of the catalyst, the ordered carbon structure in the catalyst changed and boron replaced the carbon in the material skeleton, which affected the adsorption and activation of anthracene and hydrogen. After boron doping, the catalyst showed higher activity for anthracene hydrogenation reaction, the highest conversion of anthracene was up to 97%, and the highest selectivity of deep hydrogenation product octahydroanthracene was up to 19%.
