乙烷氧化脱氢制乙烯催化剂颗粒外形设计

doi:10.16085/j.issn.1000-6613.2024-0704

摘要/Abstract

摘要：

“双碳”目标下，乙烷催化脱氢制乙烯作为一条低成本、环境友好型的非石油化工路径，具有广阔的发展前景。本文通过建立床层-颗粒耦合模型和颗粒分辨的反应器模型分别进行反应操作条件的优化和催化剂颗粒外形的设计。结果表明，提高入口温度、减小空速和增加入口压力都有利于提高乙烷转化率，但同时会导致床层温升的增加而降低乙烯的选择性，最优的操作条件为633K的入口温度、2000h^-1的空速及1.25bar（1bar=10⁵Pa）的入口压力。基于优化后的反应操作条件对四种不同的堆积结构（球形、圆柱、拉西环和三叶草）进行比较，发现球形和拉西环堆积结构分别有着最高和最低的反应器温升（31K和12K），最高和最低的乙烯收率（48.6%和43.6%），其中三叶草堆积结构因其能在维持较高乙烯收率的同时有效控制反应器温升，最适合乙烷氧化脱氢反应。

关键词: 乙烷氧化脱氢, 固定床, 传递过程, 数值模拟, 选择性, 颗粒外形设计

Abstract:

In the pursuit of dual carbon targets, catalytic dehydrogenation of ethane to ethylene emerges as a cost-efficient and eco-friendly non-petrochemical industry path, holding immense promise for future development. In this work, reactor-pellet coupled model and particle-resolved model had been established to optimize operating conditions and catalyst particle shapes, respectively. The results indicated that increasing inlet temperature, reducing space velocity, and elevating inlet pressure all contributed to high ethane conversion, but concurrently led to increased reactor temperature rise, which in turn inhibited the selectivity of ethylene. Optimal operating conditions had been determined as follows: inlet temperature of 633K, gas hourly space velocity of 2000h^-1 and inlet pressure of 1.25bar (1bar=10⁵Pa). Among the four types of packings sphere, cylinder, Raschig ring and trilobe), the sphere and Raschig ring packing structures exhibited respectively the highest and lowest reactor temperature rises (31K and 12K), as well as the corresponding highest and lowest ethylene yields (48.6% and 43.6%). The trilobe packing which maintained a tradeoff between ethylene yield and temperature rise, was the optimal particle shape for oxidative dehydrogenation of ethane.

Key words: oxidative dehydrogenation of ethane, fixed-bed, transport process, numerical simulation, selectivity, particle shape design

中图分类号:

TQ203.2

贺逸健, 刘祥坤, 施尧, 段学志. 乙烷氧化脱氢制乙烯催化剂颗粒外形设计[J]. 化工进展, 2025, 44(6): 3497-3508.

HE Yijian, LIU Xiangkun, SHI Yao, DUAN Xuezhi. Catalyst particle shape design for ethane oxidative dehydrogenation to ethylene[J]. Chemical Industry and Engineering Progress, 2025, 44(6): 3497-3508.

图/表 20

表1 乙烷氧化脱氢反应网络

反应步骤	反应焓变	反应速率
$R 1 : C 2 H 6 + 0.5 O 2 → C 2 H 4 + H 2 O$	$Δ H 298 K 0 = - 105 k J / m o l$	$r 1 = k 1 P C 2 H 6 / 1 + k 1 P C 2 H 6 2 k 0 P O 2 2$
$R 2 : C 2 H 6 + 2.5 O 2 → 2 C O + 3 H 2 O$	$Δ H 298 K 0 = - 862 k J / m o l$	$r 2 = k 2 P C 2 H 6 P O 2 0.5$
$R 3 : C 2 H 6 + 3.5 O 2 → 2 C O 2 + 3 H 2 O$	$Δ H 298 K 0 = - 1428 k J / m o l$	$r 3 = k 3 P C 2 H 6 P O 2 0.5$
$R 4 : C 2 H 4 + 2 O 2 → 2 C O + 2 H 2 O$	$Δ H 298 K 0 = - 757 k J / m o l$	$r 4 = k 4 P C 2 H 4 P O 2 0.5$
$R 5 : C 2 H 4 + 3 O 2 → 2 C O 2 + 2 H 2 O$	- $Δ H 298 K 0 = - 1323 k J / m o l$	$r 5 = k 5 P C 2 H 4 P O 2 0.5$
$R 6 : C O + 0.5 O 2 → C O 2$	$Δ H 298 K 0 = - 283 k J / m o l$	$r 6 = k 6 P C O P O 2 0.5$

表1 乙烷氧化脱氢反应网络

反应步骤	反应焓变	反应速率
$R 1 : C 2 H 6 + 0.5 O 2 → C 2 H 4 + H 2 O$	$Δ H 298 K 0 = - 105 k J / m o l$	$r 1 = k 1 P C 2 H 6 / 1 + k 1 P C 2 H 6 2 k 0 P O 2 2$
$R 2 : C 2 H 6 + 2.5 O 2 → 2 C O + 3 H 2 O$	$Δ H 298 K 0 = - 862 k J / m o l$	$r 2 = k 2 P C 2 H 6 P O 2 0.5$
$R 3 : C 2 H 6 + 3.5 O 2 → 2 C O 2 + 3 H 2 O$	$Δ H 298 K 0 = - 1428 k J / m o l$	$r 3 = k 3 P C 2 H 6 P O 2 0.5$
$R 4 : C 2 H 4 + 2 O 2 → 2 C O + 2 H 2 O$	$Δ H 298 K 0 = - 757 k J / m o l$	$r 4 = k 4 P C 2 H 4 P O 2 0.5$
$R 5 : C 2 H 4 + 3 O 2 → 2 C O 2 + 2 H 2 O$	- $Δ H 298 K 0 = - 1323 k J / m o l$	$r 5 = k 5 P C 2 H 4 P O 2 0.5$
$R 6 : C O + 0.5 O 2 → C O 2$	$Δ H 298 K 0 = - 283 k J / m o l$	$r 6 = k 6 P C O P O 2 0.5$

表2 动力学参数值

参数	数值	参数	数值
A₀/mol·s^-1·g $c a t - 1$ ·kPa^-1	490.4	E₀/kJ·mol^-1	101.6
A₁/mol·s^-1·g $c a t - 1$ ·kPa^-1	3.59	E₁/kJ·mol^-1	92.5
A₂/mol·s^-1·g $c a t - 1$ ·kPa^-1.5	39.37	E₂/kJ·mol^-1	138.4
A₃/mol·s^-1·g $c a t - 1$ ·kPa^-1.5	17.59	E₃/kJ·mol^-1	130.7
A₄/mol·s^-1·g $c a t - 1$ ·kPa^-1.5	7.31	E₄/kJ·mol^-1	116
A₅/mol·s^-1·g $c a t - 1$ ·kPa^-1.5	3.69	E₅/kJ·mol^-1	122.1
A₆/mol·s^-1·g $c a t - 1$ ·kPa^-1.5	7.36e-5	E₆/kJ·mol^-1	52.8

表2 动力学参数值

参数	数值	参数	数值
A₀/mol·s^-1·g $c a t - 1$ ·kPa^-1	490.4	E₀/kJ·mol^-1	101.6
A₁/mol·s^-1·g $c a t - 1$ ·kPa^-1	3.59	E₁/kJ·mol^-1	92.5
A₂/mol·s^-1·g $c a t - 1$ ·kPa^-1.5	39.37	E₂/kJ·mol^-1	138.4
A₃/mol·s^-1·g $c a t - 1$ ·kPa^-1.5	17.59	E₃/kJ·mol^-1	130.7
A₄/mol·s^-1·g $c a t - 1$ ·kPa^-1.5	7.31	E₄/kJ·mol^-1	116
A₅/mol·s^-1·g $c a t - 1$ ·kPa^-1.5	3.69	E₅/kJ·mol^-1	122.1
A₆/mol·s^-1·g $c a t - 1$ ·kPa^-1.5	7.36e-5	E₆/kJ·mol^-1	52.8

图1 床层-颗粒耦合模型示意图

表3 床层-颗粒耦合模型的边界条件

位置	温度条件	浓度条件
反应器入口（z=0）	$T = T 0$	$c i = c i, 0$
反应器出口（z=h_t）	$∂ T ∂ z = 0$	$∂ c i ∂ z = 0$
反应器中心（r=0）	$∂ T ∂ r = 0$	$∂ c i ∂ r = 0$
反应器壁面（r=d_t/2）	$T = T w$	$∂ c p e, i ∂ ζ = 0$
颗粒中心（ $ζ = 0$ ）	$∂ T ∂ ζ = 0$	$∂ c p e, i ∂ ζ = 0$
颗粒表面（ $ζ = 1$ ）	$T = T b u l k$	$c = c i, b u l k$

表3 床层-颗粒耦合模型的边界条件

位置	温度条件	浓度条件
反应器入口（z=0）	$T = T 0$	$c i = c i, 0$
反应器出口（z=h_t）	$∂ T ∂ z = 0$	$∂ c i ∂ z = 0$
反应器中心（r=0）	$∂ T ∂ r = 0$	$∂ c i ∂ r = 0$
反应器壁面（r=d_t/2）	$T = T w$	$∂ c p e, i ∂ ζ = 0$
颗粒中心（ $ζ = 0$ ）	$∂ T ∂ ζ = 0$	$∂ c p e, i ∂ ζ = 0$
颗粒表面（ $ζ = 1$ ）	$T = T b u l k$	$c = c i, b u l k$

表4 固定床反应器的模拟参数

参数	数值
进料温度T₀/K	633
壁面温度T_w/K	633
体积空速GHSV/h^-1	2000
入口压力P₀/bar	1.25
进料中C₂H₆摩尔分数 $X C 2 H 6, i n$	0.25
进料中O₂摩尔分数 $X O 2, i n$	0.1365
进料中H₂O摩尔分数 $X H 2 O, i n$	0.1
进料中N₂摩尔分数 $X N 2, i n$	0.5135
反应器直径d_t/mm	25.4
催化剂颗粒直径d_p/mm	5
催化剂颗粒孔隙率ε_pe	0.37
催化剂颗粒曲折因子τ_pe	2.7
催化剂颗粒密度ρ_pe/kg·m^-3	2400
催化剂颗粒热导率λ_pe/W·m^-1·K^-1	94.5

表4 固定床反应器的模拟参数

参数	数值
进料温度T₀/K	633
壁面温度T_w/K	633
体积空速GHSV/h^-1	2000
入口压力P₀/bar	1.25
进料中C₂H₆摩尔分数 $X C 2 H 6, i n$	0.25
进料中O₂摩尔分数 $X O 2, i n$	0.1365
进料中H₂O摩尔分数 $X H 2 O, i n$	0.1
进料中N₂摩尔分数 $X N 2, i n$	0.5135
反应器直径d_t/mm	25.4
催化剂颗粒直径d_p/mm	5
催化剂颗粒孔隙率ε_pe	0.37
催化剂颗粒曲折因子τ_pe	2.7
催化剂颗粒密度ρ_pe/kg·m^-3	2400
催化剂颗粒热导率λ_pe/W·m^-1·K^-1	94.5

图2 颗粒分辨的反应器模型示意图

表5 四种不同颗粒的几何参数

几何结构	外径/mm	内径/mm	高度/mm	表面积/mm²	体积/mm³	反应器高度/mm
球形	5.00	—	—	78.50	65.42	50
圆柱形	5.00	—	5.00	117.45	98.13	50
拉西环形	5.00	3.00	5.00	150.72	62.80	50
三叶草形	5.00	—	5.00	120.07	62.80	50

表6 颗粒分辨的反应器模型的边界条件

位置	温度条件	浓度条件
反应器入口（z=0）	$T = T 0$	$c i = c i, 0$
反应器出口（z=h_t）	$∂ T ∂ z = 0$	$∂ c i ∂ z = 0$
颗粒中心( $ζ = 0$ )	$∂ T ∂ ζ = 0$	$∂ c i ∂ ζ = 0$
颗粒表面( $ζ = 1$ )	$T = T b u l k$	$c = c i, b u l k$

表6 颗粒分辨的反应器模型的边界条件

位置	温度条件	浓度条件
反应器入口（z=0）	$T = T 0$	$c i = c i, 0$
反应器出口（z=h_t）	$∂ T ∂ z = 0$	$∂ c i ∂ z = 0$
颗粒中心( $ζ = 0$ )	$∂ T ∂ ζ = 0$	$∂ c i ∂ ζ = 0$
颗粒表面( $ζ = 1$ )	$T = T b u l k$	$c = c i, b u l k$

图3 出口乙烷转化率和网格单元数量的关系

图4 文献[28]实验结果与床层-颗粒耦合模型结果对比

图5 文献[28]实验结果与颗粒分辨的反应器模型结果对比

图6 入口温度对温度分布和反应器性能的影响

图7 不同入口温度下热点处颗粒内乙烯浓度分布及乙烯与CO x 浓度之比

图8 空速对温度分布和反应器性能的影响

图9 不同空速下热点处颗粒内乙烯浓度分布及乙烯与CO x 浓度之比

图10 入口压力对温度分布和反应器性能的影响

图11 不同入口压力下热点处颗粒内乙烯浓度分布及乙烯与CO x 浓度之比

图12 固定床反应器中的温度分布与反应器温升

图13 固定床反应器中的乙烷浓度分布与颗粒效率因子

图14 四种堆积结构的颗粒平均乙烷反应速率、乙烯生成速率、乙烷转化率、乙烯选择性和收率

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