First a disclaimer; conditions of exposure and the presence of other chemicals and trace impurities is important when evaluating the compatibility of a material of construction so each individual situation needs to be examined carefully. I do not have firsthand experience with these chemicals so a good starting point is Schweitzer's Corrosion Resistance Tables and the Chemical Resistance Guide for Metals and Alloys by Pruett (Compass Publications).

Xylene is the most innocuous of the three. Pruett gives an "A" rating for xylene and carbon steel at room temperature; Schweitzer gives it a "Good" rating up to 200° F. Pruett gives 316L stainless steel an "A" rating up to 212° F and Schweitzer says "Good" up to 200° F. For xylene, the choice of an MOC probably depends on your specifications for iron. If low levels of iron are unacceptable, you will need to move to a higher alloy like 316L stainless steel or even a nickel based one like Alloy C-276.

In general, the main issue with glycols is the formation of acids by glycol degradation at elevated temperatures. Whether this is an issue in your case will depend on the specifics of your application. Pruett gives an "A" rating for ethylene glycol and carbon steel up to 200° F; Schweitzer gives it a "Good" rating but only to 100° F. Pruett gives 316L stainless steel an "A" rating up to 392° F and Schweitzer says "Good" up to 200° F. Again, for ethylene glycol, the choice of an MOC probably depends on your specifications for iron.  If low levels of iron are unacceptable, you will need to move to a higher alloy like 316L stainless steel or Alloy C-276. This is consistent with information from Dow that recommends stainless steel if slight colorization cannot be tolerated.

It was more difficult to find information for methylene diphenyl diisocyanate (MDI). It is my understanding that it comes in three forms: "pure" MDI, prepolymers, and polymeric MDI. This is a tricky chemical to handle because it reacts with water and other chemicals and could result in the explosive rupture of restricted lines or closed vessels due to the liberation of heat and/or the generation of carbon dioxide gas. The best information I could find comes from Dow. They recommend stainless steel piping for pure MDI and prepolymeric forms and carbon steel for polymeric MDI.

So to summarize, depending on your tolerance for color and iron, it appears carbon steel might be acceptable for xylene and ethylene glycol. Depending on the form of methylene diphenyl diisocyanate, it looks like a stainless steel may be required.