custom post type, hide or disable the trash button in publish meta box

You can hide move to trash button via adding css in the admin area. Try following code in functions.php file:

function my_custom_admin_styles() {
?>
    <style type="text/css">
      .post-type-inhoud form #delete-action{
           display:none;
       }
     </style>
<?php
}
add_action('admin_head', 'my_custom_admin_styles');