Usage of Steam as a Carrier Gas

As it is both inexpensive and easy to handle, steam is a potential candidate carrier gas for waste plastic recycling in chemical plants. Furthermore, as mentioned in Section 2.1, the degradation temperatures for polyester resins are remarkably shifted to low-temperature regions, and the amount of carbonaceous residue produced in the degradation process is reduced in a steam atmosphere, as compared with that in a nitrogen atmosphere. Accordingly, the preparation of a catalyst that could demonstrate both stable activity for the catalytic cracking of PE-derived heavy oil, but that would also remain stable in a steam atmosphere, was examined [16], 

Nickel is a well-known catalyst component and is thought to play an important role in the transformation of the hydrogen of steam to hydrocarbons. Hence, a part of the rare earth metal in REY is exchanged with Ni to become prepared Ni and the rare earth metal-exchanged Y-type zeolite catalyst (Ni-REY) [14, 15]. The physical and chemical properties of the catalysts are listed in Table 6.8. The polyethylene plastics-derived heavy oil shown in Table 6.2 was used as the feed oil. 

A continuous-flow, fixed-bed reactor was utilized for the catalytic cracking of the heavy oil. Reactions were conducted under temperature conditions ranging from 300 to 600°C, at a catalyst weight W of about 1.0 x 10 kg and a feed oil mass flow rate F of about 1.0 X 10 kg h In order to examine the catalysis of Ni in Ni-REY for hydrogenation, experiments using hydrogen as the carrier gas were also conducted. 

---