Influence of pore structure of alumina on the adsorption, diffusion and reactivity of hydrocarbon molecules in catalytic cracking

doi:10.16085/j.issn.1000-6613.2025-0231

Abstract

Abstract:

The pore structure and acid properties of four alumina substrates were analyzed by XRD, N₂ adsorption-desorption method and NH₃-TPD, and the adsorption, diffusion and cracking properties of the samples were investigated by gratings (IGA), zero-length column (ZLC) and catalytic cracking reaction performance evaluation experiments. The results showed that the four samples all possessed abundant mesoporous structures, and had close acid content. In adsorption and diffusion experiments, the adsorption capacity of toluene increased with the gradual increase of pore volume and pore size, while the increase of mesoporous structure promoted the diffusion of 1,3,5-trimethylbenzene in the samples, and the presence of micropores limited the molecular diffusion. The performance evaluation results of catalytic cracking reaction showed that the side chain breaking reaction of aromatic hydrocarbons was the main reaction of 1,3,5-triisopropylbenzene on alumina matrix, and the addition of more mesoporous promoted the cracking reaction of 1,3,5-triisopropylbenzene molecules in the channel, which was beneficial to the production of more light hydrocarbon products and to the catalytic cracking performance of the matrix.

Key words: catalysts, alumina, pore structure, adsorption, diffusion

摘要：

采用X射线衍射（XRD）、N₂吸附-脱附法和NH₃程序升温脱附（NH₃-TPD）等手段分析了4种氧化铝基质的孔结构和酸性质等特点，并选用不同的模型化合物分子，通过重量法（IGA）、零长柱法（ZLC）和催化裂化反应性能评价实验重点考察了样品的吸附扩散和裂化性能。分析结果表明，4种样品均具有丰富的介孔结构，样品的酸量接近。吸附和扩散实验结果表明，随着孔容孔径逐渐增大，甲苯的吸附量增大，吸附质与氧化铝基质的相互作用强度减弱，同时介孔结构增多促进1,3,5-三甲基苯在样品中的扩散，而微孔的存在会对分子的扩散起限制作用。反应性能评价结果表明，1,3,5-三异丙基苯在氧化铝基质上主要发生芳烃断侧链反应，另外介孔的增多促进更多的1,3,5-三异丙基苯分子在孔道中进行裂化反应，有利于生成更多的轻烃产物，提高基质的催化裂化性能。

关键词: 催化剂, 氧化铝, 孔结构, 吸附, 扩散

CLC Number:

O643.36

ZHAO Yulong, CAI Kai, YU Shanqing. Influence of pore structure of alumina on the adsorption, diffusion and reactivity of hydrocarbon molecules in catalytic cracking[J]. Chemical Industry and Engineering Progress, 2025, 44(S1): 213-221.

赵雨龙, 蔡凯, 于善青. 氧化铝孔结构对催化裂化烃类分子吸附扩散及反应性能的影响[J]. 化工进展, 2025, 44(S1): 213-221.

Figures/Tables 11

References 24

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样品	Al-0	Al-6	Al-9	Al-11
Al₂O₃质量分数/%	98.6	98.1	97.6	97.8
比表面积/m²·g^-1	231.3	226.6	254.9	348.8
微孔比表面积/m²·g^-1	—	10.4	24.3	32.4
介孔比表面积/m²·g^-1	231.3	216.1	230.6	316.3
总孔体积/cm³·g^-1	0.424	0.757	0.944	1.164
微孔体积/cm³·g^-1	—	0.019	0.026	0.03
介孔体积/cm³·g^-1	0.424	0.738	0.918	1.134
总酸量/mmol·g^-1	0.61	0.65	0.64	0.63

样品	Al-0	Al-6	Al-9	Al-11
Al₂O₃质量分数/%	98.6	98.1	97.6	97.8
比表面积/m²·g^-1	231.3	226.6	254.9	348.8
微孔比表面积/m²·g^-1	—	10.4	24.3	32.4
介孔比表面积/m²·g^-1	231.3	216.1	230.6	316.3
总孔体积/cm³·g^-1	0.424	0.757	0.944	1.164
微孔体积/cm³·g^-1	—	0.019	0.026	0.03
介孔体积/cm³·g^-1	0.424	0.738	0.918	1.134
总酸量/mmol·g^-1	0.61	0.65	0.64	0.63

样品	温度/K	q_s,1/mmol·g^-1	b₁/mbar^-1	n₁	q_s,2/mmol·g^-1	b₂/mbar^-1	n₂	K_H/mmol·g^-1·mbar^-1	Q_st/kJ·mol^-1
Al-0	298	—	—	—	2.48	0.32	0.68	1.54	39.82
	308	—	—	—	2.13	0.29	0.63	1.43
	318	—	—	—	2.02	0.17	0.76	1.30
Al-6	298	0.80	0.07	0.22	3.09	0.17	1.38	1.43	31.75
	308	0.73	0.03	0.04	3.03	0.09	1.20	1.38
	318	0.65	0.02	0.04	2.97	0.08	1.40	1.05
Al-9	298	1.12	0.04	0.02	3.25	0.13	1.41	1.32	26.63
	308	1.05	0.03	0.18	3.05	0.04	1.80	1.22
	318	0.99	0.02	0.13	3.01	0.04	1.59	1.05
Al-11	298	1.32	0.04	0.12	3.47	0.09	1.38	0.85	18.18
	308	1.25	0.03	0.14	3.40	0.04	1.57	0.73
	318	1.11	0.02	0.23	3.30	0.03	1.95	0.62

样品	温度/K	q_s,1/mmol·g^-1	b₁/mbar^-1	n₁	q_s,2/mmol·g^-1	b₂/mbar^-1	n₂	K_H/mmol·g^-1·mbar^-1	Q_st/kJ·mol^-1
Al-0	298	—	—	—	2.48	0.32	0.68	1.54	39.82
	308	—	—	—	2.13	0.29	0.63	1.43
	318	—	—	—	2.02	0.17	0.76	1.30
Al-6	298	0.80	0.07	0.22	3.09	0.17	1.38	1.43	31.75
	308	0.73	0.03	0.04	3.03	0.09	1.20	1.38
	318	0.65	0.02	0.04	2.97	0.08	1.40	1.05
Al-9	298	1.12	0.04	0.02	3.25	0.13	1.41	1.32	26.63
	308	1.05	0.03	0.18	3.05	0.04	1.80	1.22
	318	0.99	0.02	0.13	3.01	0.04	1.59	1.05
Al-11	298	1.32	0.04	0.12	3.47	0.09	1.38	0.85	18.18
	308	1.25	0.03	0.14	3.40	0.04	1.57	0.73
	318	1.11	0.02	0.23	3.30	0.03	1.95	0.62

样品	流速/mL·min^-1	温度/K	(D_eff/R²)/s^-1
Al-0	120	393	7.35×10^-5
	120	413	1.52×10^-4
	120	433	2.52×10^-4
	120	453	4.30×10^-4
Al-6	120	393	4.21×10^-5
	120	413	7.34×10^-5
	120	433	1.22×10^-4
	120	453	1.91×10^-4
Al-9	120	393	1.02×10^-4
	120	413	1.16×10^-4
	120	433	2.73×10^-4
	120	453	7.38×10^-4
Al-11	120	393	1.84×10^-4
	120	413	3.25×10^-4
	120	433	4.22×10^-4
	120	453	6.00×10^-4