The nature and distribution of Cu species in Cu-SSZ-13 play a vital role in selective catalytic reduction of NO by NH3(NH3-SCR),but existing methods for adjusting the Cu distribution are complex and difficult to contr...The nature and distribution of Cu species in Cu-SSZ-13 play a vital role in selective catalytic reduction of NO by NH3(NH3-SCR),but existing methods for adjusting the Cu distribution are complex and difficult to control.Herein,we report a simple and effective ion-exchange approach to regulate the Cu distribution in the one-pot synthesized Cu-SSZ-13 that possesses sufficient initial Cu species and thus provides a“natural environment”for adjusting Cu distribution precisely.By using this proposed strategy,a series of Cu-SSZ-13x zeolites with different Cu contents and distributions were obtained.It is shown that the dealumination of the as-synthesized Cu-SSZ-13 during the ion-exchange generates abundant vacant sites in the double six-membered-rings of the SSZ-13 zeolite for relocating Cu2+species and thus allows the redistribution of the Cu species.The catalytic results showed that the ion-exchanged Cu-SSZ-13 zeolites exhibit quite different catalytic performance in NH3-SCR reaction but superior to the parent counterpart.The structure–activity relationship analysis indicates that the redistribution of Cu species rather than other factors(e.g.,crystallinity,chemical composition,and porous structure)is responsible for the improved NH3-SCR performance and SO_(2) and H_(2)O resistance.Our work offers an effective method to precisely adjust the Cu distribution in preparing the industrial SCR catalysts.展开更多
Five Cu-ZSM-5 catalysts were obtained by treating Na-ZSM-5(Si/Al ratio = 15) with aqueous solutions of different Cu precursors(CuCl_2, Cu(NO_3)_2, CuSO_4, Cu(CH_3COO)_2, and ammoniacal copper(II) complex ion). After b...Five Cu-ZSM-5 catalysts were obtained by treating Na-ZSM-5(Si/Al ratio = 15) with aqueous solutions of different Cu precursors(CuCl_2, Cu(NO_3)_2, CuSO_4, Cu(CH_3COO)_2, and ammoniacal copper(II) complex ion). After being pretreated in flowing He at 500 ℃ to form active Cu+, these catalysts exhibited quite different activities in catalytic decomposition of N_2O. CZM-AC(II)(prepared by ammoniacal copper(Ⅱ) complex ion) with 9.4 wt% Cu content was the most active among these Cu-ZSM-5 catalysts, achieving almost complete N_2O conversion at 400 ℃.CZM-CA(prepared using Cu(CH_3COO)_2 as the Cu precursor) with 2.8 wt% Cu content was the second most active catalyst among these Cu-ZSM-5 catalysts, achieving almost complete N_2O conversion at 425 ℃. CZM-CC, CZMCN, and CZM-CS prepared by using Cu Cl_2, Cu(NO_3)_2, or CuSO_4 as the Cu precursor with similar Cu contents(≈ 1.7 wt%) were the least active among these Cu-ZSM-5 catalysts, achieving ca. 90% N_2O conversion at 500 ℃.XRD, ICP, SEM, TEM, EDX-mapping, and CO-IR experiments were conducted to characterize relevant samples.The superior activity of CZM-AC(Ⅱ) can be attributed to the high contents of total Cu+and dimeric Cu+among these samples. The influence of co-fed O_2 or H_2O on the catalytic performance of typical samples was also studied.展开更多
A large specific surface area perovskite-type mixed oxide PbTiO3 supported cupric oxide was synthesized as a catalyst for NO decomposition and characterized by techniques such as XPS, XRD, H2-TPR before and after NO d...A large specific surface area perovskite-type mixed oxide PbTiO3 supported cupric oxide was synthesized as a catalyst for NO decomposition and characterized by techniques such as XPS, XRD, H2-TPR before and after NO decomposition reactions. The catalytic properties were tested with a fix-bed micro-reactor. The results showed that the PbTiO3 was inactive for the reactions, but 1wt % Cu/PbTiO3 catalyst gave fairly good activities for NO decomposition at temperature as low as 473 K. Copper species were found well-dispersed but weakly interacted with the support before NO decomposition, and the NO decomposition caused significant change in the environment of the copper species, which became Cu(Ⅰ)and most probably incorporated into surface crystal lattice of the nano-sized PbTiO3. In NO reaction, a large amount of oxygen atoms from the decomposition of NO penetrated into the nano-sized PbTiO3 support and caused small expansion of crystal lattice. The transport of oxygen between the copper species and the catalyst support may be helpful to speed up the kinetic regeneration of active metal sites from oxygen occupancy and resulted in good catalytic performance.展开更多
基金supports from National Natural Science Foundation of China(Nos.22178059 and 91934301)Natural Science Foundation of Fujian Province,China(2020J01513)+1 种基金Sinochem Quanzhou Energy Technology Co.,Ltd.(ZHQZKJ-19-F-ZS-0076)Qingyuan Innovation Laboratory(No.00121002),and Fujian Hundred Talent Program.
文摘The nature and distribution of Cu species in Cu-SSZ-13 play a vital role in selective catalytic reduction of NO by NH3(NH3-SCR),but existing methods for adjusting the Cu distribution are complex and difficult to control.Herein,we report a simple and effective ion-exchange approach to regulate the Cu distribution in the one-pot synthesized Cu-SSZ-13 that possesses sufficient initial Cu species and thus provides a“natural environment”for adjusting Cu distribution precisely.By using this proposed strategy,a series of Cu-SSZ-13x zeolites with different Cu contents and distributions were obtained.It is shown that the dealumination of the as-synthesized Cu-SSZ-13 during the ion-exchange generates abundant vacant sites in the double six-membered-rings of the SSZ-13 zeolite for relocating Cu2+species and thus allows the redistribution of the Cu species.The catalytic results showed that the ion-exchanged Cu-SSZ-13 zeolites exhibit quite different catalytic performance in NH3-SCR reaction but superior to the parent counterpart.The structure–activity relationship analysis indicates that the redistribution of Cu species rather than other factors(e.g.,crystallinity,chemical composition,and porous structure)is responsible for the improved NH3-SCR performance and SO_(2) and H_(2)O resistance.Our work offers an effective method to precisely adjust the Cu distribution in preparing the industrial SCR catalysts.
基金Supported by the National Natural Science Foundation of China(Grant No.21477022)
文摘Five Cu-ZSM-5 catalysts were obtained by treating Na-ZSM-5(Si/Al ratio = 15) with aqueous solutions of different Cu precursors(CuCl_2, Cu(NO_3)_2, CuSO_4, Cu(CH_3COO)_2, and ammoniacal copper(II) complex ion). After being pretreated in flowing He at 500 ℃ to form active Cu+, these catalysts exhibited quite different activities in catalytic decomposition of N_2O. CZM-AC(II)(prepared by ammoniacal copper(Ⅱ) complex ion) with 9.4 wt% Cu content was the most active among these Cu-ZSM-5 catalysts, achieving almost complete N_2O conversion at 400 ℃.CZM-CA(prepared using Cu(CH_3COO)_2 as the Cu precursor) with 2.8 wt% Cu content was the second most active catalyst among these Cu-ZSM-5 catalysts, achieving almost complete N_2O conversion at 425 ℃. CZM-CC, CZMCN, and CZM-CS prepared by using Cu Cl_2, Cu(NO_3)_2, or CuSO_4 as the Cu precursor with similar Cu contents(≈ 1.7 wt%) were the least active among these Cu-ZSM-5 catalysts, achieving ca. 90% N_2O conversion at 500 ℃.XRD, ICP, SEM, TEM, EDX-mapping, and CO-IR experiments were conducted to characterize relevant samples.The superior activity of CZM-AC(Ⅱ) can be attributed to the high contents of total Cu+and dimeric Cu+among these samples. The influence of co-fed O_2 or H_2O on the catalytic performance of typical samples was also studied.
基金supported by the National Natural Science Foundation of China(21872072,21573113)Municipal Natural Science Foundation of Tianjin(18JCZDJC37400)Sinopec(417012)~~
文摘生物乙醇作为一种绿色原料,常用于制备具有更高附加值的化学品,如乙烯、丙烯、丁二烯、1-丁醇和乙醛等.其中,乙醛作为重要的化学原料又可以进一步转化生成乙酸,乙酸酯和季戊四醇等。因此,由生物乙醇脱氢制乙醛的可持续路线受到了研究者的广泛关注.在众多催化体系中,Cu基催化剂表现出较高的活性和乙醛选择性,但Cu物种的烧结又会导致催化剂的快速失活.因此,抑制Cu物种的烧结是提高Cu基催化剂稳定性的常用手段.本文通过后合成路线构筑了具有限域效应的Cu/Beta分子筛催化剂,并成功应用于乙醇脱氢制乙醛反应.我们首先考察了Cu的负载量、反应温度和Cu的前驱体对反应的影响,发现以醋酸铜为前驱体的5%Cu/Beta催化剂在乙醇脱氢制乙醛反应中表现出最佳催化性能:催化剂寿命达到100 h,乙醛收率稳定在70%左右(反应条件:300℃,WHSV=1.0 h^-1).XRD,TEM,DRIFT,1H MAS NMR,UV-Vis以及H2-TPR等结果表明以醋酸铜为前驱体的Cu/Beta分子筛上的主要活性中心为CuO物种,并且该物种以高度分散的形式限域在分子筛脱铝产生的硅羟基缺陷位上.因此,在乙醇脱氢制乙醛反应中,限域的Cu/Beta分子筛催化剂与孤立的CuO催化剂相比,具有优异的抗烧结能力.然而,当反应至180 h时,催化剂会有明显的失活现象.再生后,尽管催化剂的初始活性能较好的恢复,但催化剂的寿命却大大下降.我们利用TEM,TGA以及CO-DRIFTS对反应后的催化剂进行表征,发现失活的Cu/Beta催化剂上存在Cu+和Cu0物种,并且伴有大块烧结现象.这表明随着反应的进行,Cu/Beta催化剂上的CuO物种会逐渐还原成Cu+和Cu0物种,而Cu0物种的出现又会诱导烧结现象的发生,进而导致催化剂的失活.
文摘A large specific surface area perovskite-type mixed oxide PbTiO3 supported cupric oxide was synthesized as a catalyst for NO decomposition and characterized by techniques such as XPS, XRD, H2-TPR before and after NO decomposition reactions. The catalytic properties were tested with a fix-bed micro-reactor. The results showed that the PbTiO3 was inactive for the reactions, but 1wt % Cu/PbTiO3 catalyst gave fairly good activities for NO decomposition at temperature as low as 473 K. Copper species were found well-dispersed but weakly interacted with the support before NO decomposition, and the NO decomposition caused significant change in the environment of the copper species, which became Cu(Ⅰ)and most probably incorporated into surface crystal lattice of the nano-sized PbTiO3. In NO reaction, a large amount of oxygen atoms from the decomposition of NO penetrated into the nano-sized PbTiO3 support and caused small expansion of crystal lattice. The transport of oxygen between the copper species and the catalyst support may be helpful to speed up the kinetic regeneration of active metal sites from oxygen occupancy and resulted in good catalytic performance.
