I've checked the software and its official website and these are the official system requirements:
Windows 7, Windows 8, Windows 10, OS X 10.9 Mavericks, OS X 10.10 Yosemite or OS X 10.11 El Capitan
64-bit operating system
1 GB free hard disk space for installation
Internet connection required for online activation and web services
Intel Core i3, Core i5, Core i7 or Intel Xeon (Nehalem) processor or AMD equivalent
4GB RAM
OpenGL 2.0 capable hardware with at least 512 MB video memory (NVIDIA GeForce 9 series, Radeon HD 5000 series, Intel HD 4000)
As you can see, 32bit is not supported, and I believe it's because the software needs to work with more than 4GB of RAM due to its complexity, while the 32bit only supports 3.2 GB of RAM.
For additional info, consult the following page: https://hitfilm.com/store/hitfilm-4-express#requirements
