Merging OBJ tiles for export to LumenRT

I have created a 3d model in contextcapture in 3mx format and OBJ format. Because of the RAM usage per job, I made tiles for the production. I want to export this model to LumenRT. When i try to export the 3mx from Microstation to LumenRt, it does not include textures. The mesh is white. How can I solve this?

I can export OBJ files to LumenRT with succes, but I do not have a complete OBJ file of the entire model, because I had to produce tiles. Is there a way to merge the OBJ files with textures?