Investigation on MTO catalyst morphology and its coke amount by fiber-optic endoscope image method

doi:10.11949/0438-1157.20220080

Abstract

Abstract:

The multi-scale phenomenon in catalytic reaction process has been a hot research topic in the field of particle science in recent years, among which particle morphology and coke deposition are the key parameters that affect the catalyst flow and activity. In order to investigate coke influence on catalysts morphology,we have made five types of sample catalysts with different coke amount from the second generation zeolite SAPO-34 catalyst in DMTO process in our pilot fixed fluidized bed reactor under the condition of their residence in the reactor such as 0, 30, 60, 90 and 120 min separately. Particle size, sphericity, ellipse ratio, chroma and their distribution etc. were measured by image processing integrated with deep learning algorithm. The high-resolution images of the five samples were snapped by using an optical fiber endoscopic micro-scale imaging platform. The experimental results show that there exists the strong coke influence on catalysts size and its distribution. However, this effect on catalysts spherical or elliptical ratio is weak. Compared with the coke data measured by a thermogravimetric instrument, we have developed a coke-chromaticity method, which is a mathematical linear model between coke amount and the chromaticity of five catalysts samples. Two verification samples were chosen from the industrial catalysts used in a DMTO plant. The measurement relative error is less than 10% with a good consistency according to the coke data obtained by thermogravimetric device and that predicated by the coke-chromaticity method. This will provide a potential method for monitoring catalyst state in DMTO reactor and guiding its processing optimum operation.

Key words: catalyst coke, particle morphology, image chromaticity

摘要：

催化反应过程中的多尺度现象一直是近年来颗粒学领域研究的热点，其中颗粒形貌、积炭都是影响催化剂流态及活性的关键参数。为了从颗粒尺度深入探究积炭对催化剂颗粒表观形貌的影响，选取了DMTO工艺中第二代分子筛SAPO-34催化剂，在实验室微型固定流化床反应器中制备了停留时间分别为0、30、60、90、120 min等多种催化剂样品。使用课题组研制的光纤内窥显微成像平台，拍摄了催化剂样品的微尺度图像，并以此构建了基于深度学习的样本形貌图像库，实现批量统计催化剂颗粒表观特性（包括粒径、球形度、椭圆比、色度等参数及其分布）的功能。测量结果表明：积炭会明显改变催化剂的粒径及其分布，但是对催化剂的球形度或椭圆比等参数的影响较小。通过比较这些催化剂样本图像的色度信息与其对应的热重法测得的积炭量数据，建立了催化剂色度信息与其积炭量之间的定量关系，并预测了两种来自某企业DMTO生产装置反应器内催化剂的平均积炭量。实验数据表明：图像色度法与热重法测量结果的相对误差小于10%，具有较好的一致性。这将有助于发展基于图像色度法测量催化剂积炭量的工业仪表，为工业过程从颗粒尺度认识反应器内催化剂的状态提供便携的观测手段，进而指导操作人员对DMTO工艺进行优化调控。

关键词: 催化剂积炭, 颗粒形貌, 图像色度

CLC Number:

TQ 075

Yong LU, Duiping LIU, Chenyang LI, Jibin ZHOU, Mao YE. Investigation on MTO catalyst morphology and its coke amount by fiber-optic endoscope image method[J]. CIESC Journal, 2022, 73(6): 2662-2668.

陆勇, 刘对平, 李晨阳, 周吉彬, 叶茂. 光纤内窥图像法测量MTO催化剂表观形貌及其积炭量的实验研究[J]. 化工学报, 2022, 73(6): 2662-2668.

Figures/Tables 8

Fig.1 Experimental image device for measuring DMTO catalyst particles

Fig.2 Video/image processing chart

Table 1 Physical properties of SAPO-34 catalyst

比表面积/(cm²/g)	孔体积/(cm³/g)	粒度分布/%
比表面积/(cm²/g)	孔体积/(cm³/g)	≤20 μm	20~40 μm	40~80 μm	80~110 μm	110~150 μm	≥150 μm
≥180	≥0.15	≤5	≤10	30~50	10~30	10~30	≤20

Fig.3 Images of five catalyst samples produced in laboratory condition

Fig.4 The size distribution of five catalyst samples

Fig.5 The sphericity and ellipse distribution of five catalyst samples

Fig.6 The relationship between the coke amount of five catalyst samples and their chroma

Fig.7 Comparison between the coke data of two DMTO catalyst samples measured by thermal gravity instrument and image chroma method

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