Unfortunately, Mental ray® Standalone is a commercial application developed by Autodesk and there is no trial version available. If you want, you can purchase the application from the official web page. In general, Mental ray® Standalone works with Autodesk 3DS Max and Autodesk Maya. If you have issues importing the .vrml file in one of these programs, try to change its extension from .vrml to .wrl or .wrz.
