Try this script as it's newer than the one posted above.
https://github.com/JAMFSupport/FileVault2_Scripts/blob/master/reissueKey.sh
#!/bin/bash
####################################################################################################
#
# Copyright (c) 2013, JAMF Software, LLC. All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
# * Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# * Redistributions in binary form must reproduce the above copyright
# notice, this list of conditions and the following disclaimer in the
# documentation and/or other materials provided with the distribution.
# * Neither the name of the JAMF Software, LLC nor the
# names of its contributors may be used to endorse or promote products
# derived from this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY JAMF SOFTWARE, LLC "AS IS" AND ANY
# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL JAMF SOFTWARE, LLC BE LIABLE FOR ANY
# DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
# (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#
####################################################################################################
#
# Description
#
# The purpose of this script is to allow a new individual recovery key to be issued
# if the current key is invalid and the management account is not enabled for FV2,
# or if the machine was encrypted outside of the JSS.
#
# First put a configuration profile for FV2 recovery key redirection in place.
# Ensure keys are being redirected to your JSS.
#
# This script will prompt the user for their password so a new FV2 individual
# recovery key can be issued and redirected to the JSS.
#
####################################################################################################
#
# HISTORY
#
# -Created by Sam Fortuna on Sept. 5, 2014
# -Updated by Sam Fortuna on Nov. 18, 2014
# -Added support for 10.10
# -Updated by Sam Fortuna on June 23, 2015
# -Properly escapes special characters in user passwords
# -Updated by Bram Cohen on May 27, 2016
# -Pipe FV key and password to /dev/null
# -Updated by Jordan Wisniewski on Dec 5, 2016
# -Removed quotes for 'send {${userPass}}' so
# passwords with spaces work.
#
####################################################################################################
#
## Get the logged in user's name
userName=$(/usr/bin/stat -f%Su /dev/console)
## Get the OS version
OS=`/usr/bin/sw_vers -productVersion | awk -F. {'print $2'}`
## This first user check sees if the logged in account is already authorized with FileVault 2
userCheck=`fdesetup list | awk -v usrN="$userName" -F, 'index($0, usrN) {print $1}'`
if [ "${userCheck}" != "${userName}" ]; then
echo "This user is not a FileVault 2 enabled user."
exit 3
fi
## Check to see if the encryption process is complete
encryptCheck=`fdesetup status`
statusCheck=$(echo "${encryptCheck}" | grep "FileVault is On.")
expectedStatus="FileVault is On."
if [ "${statusCheck}" != "${expectedStatus}" ]; then
echo "The encryption process has not completed."
echo "${encryptCheck}"
exit 4
fi
## Get the logged in user's password via a prompt
echo "Prompting ${userName} for their login password."
userPass="$(/usr/bin/osascript -e 'Tell application "System Events" to display dialog "Please enter your login password:" default answer "" with title "Login Password" with text buttons {"Ok"} default button 1 with hidden answer' -e 'text returned of result')"
echo "Issuing new recovery key"
if [[ $OS -ge 9 ]]; then
## This "expect" block will populate answers for the fdesetup prompts that normally occur while hiding them from output
expect -c "
log_user 0
spawn fdesetup changerecovery -personal
expect "Enter a password for '/', or the recovery key:"
send {${userPass}}
send
log_user 1
expect eof
" >> /dev/null
else
echo "OS version not 10.9+ or OS version unrecognized"
echo "$(/usr/bin/sw_vers -productVersion)"
exit 5
fi
exit 0
