It depends on the specific problem you solved. Obviously, Deep learning is the most popular approach when solving the problems in the filed of Computer Vision, Speech Recognition, and Natural Language Processing. When solving the complicated engineering optimization problems, Evolutionary Algorithms may be the most popular approaches.

For the Chemical Engineering problems, I will say that Artificial neural networks (ANN), Decision tree, Logistic regression, and Support Vector machines are some of the most commonly used machine learning methods.

I feel the answer for this question is not easy, since the application of Artificial Intelligence and Machine Learning methods do not depend on the field of application, but mainly depend on the specific problem/issue under study.