超稳Y型分子筛的骨架硅铝比对甘油气相脱水反应的影响
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摘要
以铵交换和高温水热处理法制备了不同硅铝比的超稳Y型分子筛(USY),利用X射线衍射、扫描电镜、氮气吸附脱附和吡啶红外等技术对USY进行了表征。以USY为催化剂,考察了USY的骨架硅铝比对气相甘油脱水制丙烯醛的影响。X射线衍射和扫描电镜结果表明,铵交换和高温水热处理只是提高USY的硅铝比,相对结晶度略有降低,而对Y型分子筛的结构和形貌没有影响。氮气吸附-脱附和吡啶红外结果表明,随USY骨架SiO_2/Al_2O_3比提高,总酸量和B酸酸量逐渐降低,L酸酸量有所增多,介孔孔体积和平均孔径有所增大。气相甘油脱水反应结果表明,催化剂织构性质对甘油转化率和丙烯醛选择性的影响大于酸性的影响,因而SiO_2/Al_2O_3比为29的USY催化剂的反应性能最好,甘油转化率和丙烯醛收率分别达到了84.5%和51.8%。
The USY zeolites with different SiO_2/Al_2O_3 ratios were prepared from commercial USY zeolites via the ammonium exchange and hydrothermal treatment and then were characterized by XRD, SEM, N2 adsorption and desorption isotherms and py-IR. The influence of SiO_2/Al_2O_3 ratio on the performance of USY zeolites for the gas-phase dehydration of glycerol to acrolein was investigated. The results of XRD and SEM showed that the ammonium exchange and hydrothermal treatment only increased the SiO_2/Al_2O_3 ratio and decreased the relative crystallinity of USY but had no effect on the structure and morphology of USY. The analysis of N2 adsorption and desorption isotherms and py-IR demonstrated that the total and B acid content of the USY gradually decreased, L acid content, mesoporous volume and mean pore size increased with the increase of framework SiO_2/Al_2O_3 ratio. Activity evaluation results revealed that the textural property had more important effect on glycerol conversion and acrolein selectivity than the acid property. Therefore, USY with a SiO_2/Al_2O_3 ratio of 29 displayed the best catalytic performance, giving an acrolein yield of 51.8% and glycerol conversion of 84.5%.
The USY zeolites with different SiO_2/Al_2O_3 ratios were prepared from commercial USY zeolites via the ammonium exchange and hydrothermal treatment and then were characterized by XRD, SEM, N2 adsorption and desorption isotherms and py-IR. The influence of SiO_2/Al_2O_3 ratio on the performance of USY zeolites for the gas-phase dehydration of glycerol to acrolein was investigated. The results of XRD and SEM showed that the ammonium exchange and hydrothermal treatment only increased the SiO_2/Al_2O_3 ratio and decreased the relative crystallinity of USY but had no effect on the structure and morphology of USY. The analysis of N2 adsorption and desorption isotherms and py-IR demonstrated that the total and B acid content of the USY gradually decreased, L acid content, mesoporous volume and mean pore size increased with the increase of framework SiO_2/Al_2O_3 ratio. Activity evaluation results revealed that the textural property had more important effect on glycerol conversion and acrolein selectivity than the acid property. Therefore, USY with a SiO_2/Al_2O_3 ratio of 29 displayed the best catalytic performance, giving an acrolein yield of 51.8% and glycerol conversion of 84.5%.
引文
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[2]张业,周梅,魏文珑,等.丙烯醛合成工艺及催化剂研究进展[J].天然气化工, 2008,33(2):54-59.ZHANG Ye,ZHOU Mei,WEI Wenlong,et al. Research progress on technology and catalysts of the synthesis of acrolein[J]. Natural Gas Chemical Industry, 2008,33(2):54-59.
[3] PATHAK K,REDDY K M,BAKHSHI N N,et al. Catalytic conversion of glycerol to value added liquid products[J]. Applied Catalysis A:General, 2010,372(2):224-238.
[4]张跃,丁海亮,刘建武,等.金属氧化物对H3PW12O40/γ-Al2O3在甘油制丙烯醛过程中性能的影响[J].天然气化工, 2011,36(5):13-16.ZHANG Yue,DING Hailiang,LIU Jianwu,et al. Study on catalytic properties of H3PW12O40/γ-Al2O3catalysts modified with metal oxides for preparation of acrolein from glycerol[J]. Natural Gas Chemical Industry, 2011,36(5):13-16.
[5] GALADIMA A,MURAZA O. A review on glycerol valorization to acrolein over solid acid catalysts[J]. Journal of the Taiwan Institute of Chemical Engineers, 2016,67:29-44.
[6] DECOLATTI H P,DALLA COSTA B O,QUERINI C A. Dehydration of glycerol to acrolein using H-ZSM5 zeolite modified by alkali treatment with NaOH[J]. Microporous and Mesoporous Materials,2015,204:180-189.
[7] SáNCHEZ G,DLUGOGORSKI B Z,KENNEDY E M,et al. Zeolitesupported iron catalysts for allyl alcohol synthesis from glycerol[J].Applied Catalysis A:General, 2016,509:130-142.
[8] GU Y,CUI N,YU Q,et al. Study on the influence of channel structure properties in the dehydration of glycerol to acrolein over H-zeolite catalysts[J]. Applied Catalysis A:General, 2012,429/430(25):9-16.
[9] BRECK D A. Zeolite molecular sieves—structure, chemistry and use[M]. New York:Wiley-lnterscience, 1974.
[10] EMEIS C A. Determination of integrated molar extinction coefficients for infrared absorption bands of pyridine adsorbed on solid acid catalysts[J]. Journal of Catalysis, 1993,141:347-354.
[11] TREACY M M J,HIGGINS JB,HIGGINS J B. Collection of simulated XRD powder patterns for zeolites[M]. Amsterdam:Elsevier, 2001.
[12] LUTZ W,L?FFLER E,FECHTELKORD M,et al. Non-framework aluminium in highly dealuminated Y zeolites generated by steaming or substitution[J]. Studies in Surface Science and Catalysis, 1997,105:439-446.
[13]张继德.影响合成Y型分子筛硅铝比因素的初步探讨[J].石油炼制, 1978,11/12:26-30.ZHANG Jide. Preliminary study on the factors of SiO2/Al2O3ratio in the synthesis of Y zeolites[J]. Petroleum Processing, 1978,11/12:26-30.
[14] PROUZET E,COT F,NABIAS G,et al. Assembly of mesoporous silica molecular sieves based on nonionic ethoxylated sorbitan esters as structure directors[J]. Chemical of Materials, 1999,11:1498-1503.
[15]王红霞,傅吉全,宋为民,等.改性Y型沸石的结构及酸性质的研究[J].石油化工, 1997, 26(5):26-29.WANG Hongxia,FU Jiquan,SONG Weimin,et al. Structure and acidic properties of modified Y-zeolites[J]. Petrochemical Technology,1997,26(5):26-29.
[16] ULGEN A,HOELDERICH W. Conversion of glycerol to acrolein in the presence of WO3/ZrO2catalysts[J]. Catalysis Letters, 2009,131:122-128.