Hi,
Thanks for sending the submission ID.
The invalid character occurs in the title
<title>decomposition of 2-propanol over Alumina supported Thoria and Potassium ion modified catalysts</title>
It’s in between “modi” and "fied’. When I open your xml in a text editor it appears as a question mark, which is a [replacement character](Specials (Unicode block) - Wikipedia. In other contexts, you might see it as a white question mark in a black diamond, or a hollow square, or just a blank space. In other contexts it can be totally invisible.
Since you submitted this metadata using the Web Deposit Form, the invalid character was likely brought over when you copy-pasted some text with formatting.
You will need to resubmit the metadata, but ensure that you paste the text in without formatting. You can use command+shift+V on a Mac, or control+shift+V on Windows, to paste plain text without formatting.
Best,
Shayn