I think the thought of Russia breaking up or losing thier fellow dictator in crime is too much of a worry for China.
Just like Russia, they can't afford to have a democracy next door born from the ashes of a fallen corrupted regime/ dictator that they praised.
The US will definitely hit hard with sanctions and they will bite china hard, question is how will the EU member states act individually, if they all follow the US then China will be losing thier two most important markets for selling to, will Xi cope with the social unrest this could cause?
Some big gambling to be had by China here.