Error with XML-INTO caused by non-printable characters

Runnin on V7.1

We receive from a SAP environment xml documents which are stored as a CLOB in a PF on our system.

To process those xml documents we extract those documetns from that file, store it on the IFS and then read the IFS file in with XML-INTO.

Some of those xml documents crash on the XML-INTO opcode. It appears those xml documents contain non-printable charaters (less than x'40')

So, we have to remove those non-printable charaters.

I looked at QSH -tr command, but could not gget it to work.

Another option is using SQL when retrieving the CLOB from the PF before writing to the IFS.
Itried the following syntax:

exec sql
select REPLACE(CLOB_in_PF, x'0102 ... 3E3F', '') into :SQLCLOB_field from Our_PF ;  (thus all hex values with the exception of NULL).

This doesnot work.

Question:
How can we remove those non-printable characters from an xml document stored in our PF?

TIA

Kind regards,
Carel Teijgeler