Research on the process of naphtha hydrocracking to chemical materials

• On ZSM-5, paraffin and cycloalkane in naphtha are mainly convertible hydrocarbons. • As C 5+ conversion rate rises, aromatic in naphtha remain almost unchanged. • C 5+ i -paraffin has a lower conversion rate compared to C 5+ n -paraffin. • C 5 -ring CRC is more likely undergoing RO reaction than that of C 6 -ring CRC. To systematically study the conversion process of paraffin, cycloalkane, and aromatic on ZSM-5 molecular sieve in naphtha hydrocracking, a series of related experiments were carried out based on the prepared hydrocracking catalyst, Catalyst-HC. Ni and ZSM-5 molecular sieve were selected as the hydrogenation active component and the cracking component of Catalyst-HC, respectively. The results obtained through this work indicate that on ZSM-5 molecular sieve, the paraffin and cycloalkane in naphtha are mainly convertible hydrocarbons. The higher the content of convertible hydrocarbons in naphtha, the easier it is for the conversion reaction to occur. As C 5+ conversion rate rises, the yields of paraffin and cycloalkane decline, and the yields of aromatic and aromatic-carbon in product-naphtha remain almost unchanged. The aromatic-average carbon-number (CN) in product-naphtha changes very little, decreasing from 8.3 to 8.2. This means that almost no aromatic undergoes the saturation reaction or conversion reaction on Catalyst-HC. Due to the small pore size of ZSM-5, C 5+ i -paraffin has a lower conversion rate and a higher average CN compared to C 5+ n -paraffin. Meanwhile, as C 5+ conversion rate gradually rises from 0 to 23 %, the average CN drop-values of C 5+ n -paraffin and C 5+ i -paraffin are 1.3 and 0.14, respectively. C 5 -ring cycloalkane-ring-carbon (C 5 -ring CRC) is more likely undergoing ring-opening (RO) reaction than that of C 6 -ring cycloalkane-ring-carbon (C 6 -ring CRC). The conversion rate of C 5 -C 7 cycloalkane is higher than that of C 8+ cycloalkane, and the former bears a higher jump-value compared to the latter with the increase of C 5+ conversion rate. Unlike paraffin and aromatic, the average CN of cycloalkane gradually rises with the increase of C 5+ conversion rate.