The feasibility of using a microtubular reactor for heterogeneous polymerization of ethylene was investigated experimentally. Chemically inert polymer tubing of 800-2300m in inner diameter was fabricated and used as a polymerization reactor. Nonporous silica nanoparticles with a diameter of 400nm were synthesized and used as support for the high-activity rac-ethylene(indenyl)(2)ZrCl2 catalyst with methylaluminoxane as cocatalyst and toluene as diluent. Large-diameter microtubular reactors were also successfully used to conduct heterogeneous polymerization of ethylene in continuous reaction operations. High initial catalyst activity was obtained and the overall polymerization activity per volume or reactor length was quite high. No particle fragmentation occurred and the polymer particles were covered with small subgrains or nanofibrils with a diameter of 30nm.