For a graduate chemical engineer, should he opt for masters in Chemical/Environmental/Petroleum?

Do an MBA my friend. Also, Pick up NEBOSH and OHS and Environmental Auditing Skills. As you grow they help you to become a Manager in Canada or Australia as these are the countries most professionals are migrating to. Best of luck.

1. chemical engineering is best for as master for graduate in chemical engineer

Specialization desirable to continue to study and get a master's Hoamajal who want to work with him or domain in which they operate degree if you are an employee

It is advisable to seek a job for 3 years and then to do post graduation as it will make you learn in better way practically. Also it shall not let that opportunity go; of getting a job after engineering and missing it. It will keep that chance of coming back to industries in a easy way. However some people may find it difficult to seek post graduation after 3 years break. You have to take your call.

Munsif, As a new engineer, the advanced degree is important and will be valuable to gain meaningful employment in the future. You will be well swrved to get your Masters.