•A novel fault diagnosis scheme was proposed based on optimization methods.•Nonstationary and nonlinear multivariate chemical processes were analyzed.•NSGAII was utilized for feature selection and t-SNE method was used as feature extraction and visualization method.•DBSCAN, k-means, CURE methods were utilized for non- automatic unsupervised learning investigation.•GA, ABC, DE, HS, and PSO, in combination with DB and CS clustering measures were utilized as automatic unsupervised learning investigation.•The proposed method performed well for fault detection and diagnosis of chemical processes. Fault detection and diagnosis (FDD) is crucial for ensuring process safety and product quality in the chemical industry. Despite the large amounts of process data recorded and stored in chemical plants, most of them are not well-labeled, and their conditions are not adequately specified. In this study, an optimized data-driven FDD model was developed for a chemical process based on automatic clustering algorithms. Due to data preprocessing importance, feature selection was performed by a non-dominated sorting genetic algorithm (NSGAII) based on k-means clustering. The optimal subset of features is selected by comparing clustering results for each subset. The performance of the proposed feature selection method was compared with the Fisher discriminant ratio (FDR), and XGBoost methods. The t-distributed stochastic neighbor embedding (t-SNE), Isomap, and KPCA dimension reduction methods were also employed for feature extraction. Finally, automatic clustering was performed based on metaheuristic algorithms for fault detection and diagnosis. Results were compared with non-automatic clustering methods. The performance of the proposed method was evaluated by examining the Tennessee Eastman and four water tank processes as case studies. The results showed that the proposed method is reliable and capable of online and offline chemical process fault detection and diagnosis. As a result, the findings of this study can be used to stabilize the operation of chemical processes. Display omitted