custom post type make featured image box full width

I think you are trying to move Featured Image meta box to left column. Add this code to your plugin or functions.php file of your active theme.

add_action( 'do_meta_boxes', 'wpse_269370_move_featured_image_meta_box' );

function wpse_269370_move_featured_image_meta_box() {
    remove_meta_box( 'postimagediv', 'portfolio_post_type', 'side' ); // remove meta box of featured image from current location - 'side'

    add_meta_box( 'postimagediv', __('Featured Image'), 'post_thumbnail_meta_box', 'portfolio_post_type', 'normal', 'high' ); // add meta box of featured image again, at new location - 'normal'
}