基于不同Cu-CHA催化剂方案的NH3-SCR性能及氨存储特性研究

doi:10.19964/j.issn.1006-4990.2024-0089

Abstract

Abstract:

To investigate the effects of coating silicon aluminum ratio（SAR），loading amount，cell density of substrate scheme，and ammonia/nitrogen oxide molar ratio（ANR） on transient NO _x conversion efficiency and ammonia storage characteristics of SCR catalysts，Cu-CHA coatings with SAR=12 and 22 were prepared by ion exchange method.Four coating catalyst schemes were prepared by combining loading amounts of 140 g/L and 160 g/L，62 pores/cm² and 93 pores/cm² mesh size carriers.Through NH₃-TPD/H₂-TPR characterization of the material，it was found that the SAR=12 coating had more active Cu²⁺ and more acidic sites.The transient single point performance and operating condition emissions of SCR were studied using a fixed bed reactor and an engine bench，respectively.Single point performance studies showed that the low-temperature NO _x reaction rates of each scheme were 12-160-93，12-160-62，12-140-62，22-160-62.Under the 12-160-93 scheme，the average single point reaction rates at 180 ℃，200 ℃，and 250 ℃ could reach 2.24 ×10^-6 mol/s，4.37×10^-6mol/s and 1.48×10^-5 mol/s，respectively.Low SAR，high load，and high cell density schemes could improve the transient NO _x conversion rate at a single point，reduce the transient ammonia storage capacity.Improving ANR could simultaneously enhance transient NO _x conversion rate and transient ammonia storage capacity.The NO _x emissions under different operating conditions were consistent with the low-temperature single point performance，but the high load scheme enhanced the NH₃ leakage under changing operating conditions，which was opposite to the trend of NH₃ leakage at a single point performance.

Key words: Cu-CHA zeolite, selective catalytic reduction, NO _x reaction rate, ammonia storage characteristics, NH₃ slip

CLC Number:

TQ131.21

LAI Huilong, YU fei, YANG Dongxia, MA Jiangli, YIN Xuemei, CHANG Shiying. Research on NH₃-SCR performance and ammonia storage characteristics based on different Cu-CHA catalyst schemes[J]. Inorganic Chemicals Industry, 2024, 56(12): 159-166.

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References 14

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分子筛方案	比表面积/（m²·g^-1）	平均孔径/nm	SAR	w（铜）/ %
H-CHA（SAR=12）	723.16	2.17	12.13
Cu-CHA（SAR=12）	697.03	2.03	12.47	4.71
H-CHA（SAR=22）	708.71	1.95	21.94
Cu-CHA（SAR=22）	688.03	1.82	21.65	3.18

温度/ ℃	NO _x 转化率增量/%
温度/ ℃	22-160-62VS12-160-62	12-140-62 VS12-160-62	12-160-62 VS12-160-93	12-160-62 ANR=1.0 VS0.8
180	2.92	2.52	10.62	1.44
200	5.18	2.38	16.16	0.36
250	5.18	3.36	2.87	10.70
300	0.31	0.08	0.28	14.18
400	0.54	0.42	0.17	16.79
500	4.22	-0.03	-1.27	17.20
550	7.33	-1.64	-2.43	15.73

方案	180 ℃平均反应速率/ （10^-6 mol·s^-1）	200 ℃平均反应速率/ （10^-6 mol·s^-1）	250 ℃平均反应速率/ （10^-6 mol·s^-1）
12-160-62	2.24	4.37	14.82
22-160-62	1.59	3.56	13.70
12-140-62	1.95	4.02	13.77
12-160-93	3.68	6.73	15.48
12-160-62-ANR=0.8	2.01	4.12	13.44

温度/℃	12-160-62		22-160-62			12-140-62		12-160-93			12-160-62-ANR=0.8
温度/℃	饱和时间/s	饱和储量/g	饱和时间/s	饱和储量/g		饱和时间/s	饱和储量/g	饱和时间/s	饱和储量/g		饱和时间/s	饱和储量/g
180	177.67	1.63	152.33	1.47	159.33		1.50	223.67	1.90	244.67		1.77
200	212.66	1.69	191.20	1.60	186.10		1.55	320.00	2.16	328.34		1.92
250	810.54	1.57	641.43	1.69	547.00		1.41	1 440.99	1.81	1 925.00		1.39

方案	NO _x 的排放量/（g·kW^-1·h^-1）				NH₃质量浓度/（mg·m^-3）
方案	WHSC	WHTC-c	WHTC-h	WHTC加权	WHSC	WHTC-c	WHTC-h	WHTC加权
12-160-62	0.10	0.55	0.17	0.22	139.0	83.49	63.50	66.00
22-160-62	0.19	0.63	0.24	0.29	151.7	90.55	83.28	84.19
12-140-62	0.13	0.58	0.20	0.25	123.9	78.46	56.55	59.29
12-160-93	0.08	0.46	0.09	0.14	115.8	76.58	55.93	58.51

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Research on NH₃-SCR performance and ammonia storage characteristics based on different Cu-CHA catalyst schemes

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Research on NH3-SCR performance and ammonia storage characteristics based on different Cu-CHA catalyst schemes