Abstract
Nobel metallic Pt/ZSM-22 and Pt/ZSM-23 catalysts were prepared for hydroisomerization of normal dodecane and hydrodewaxing of heavy waxy lube base oil. The hydroisomerization performance of n-dodecane indicated that the Pt/ZSM-23 catalyst preferred to crack the C–C bond near the middle of n-dodecane chain, while the Pt/ZSM-22 catalyst was favorable for breaking the carbon chain near the end of n-dodecane. As a result, more than 2% of light products (gas plus naphtha) and 3% more of heavy lube base oil with low-pour point and high viscosity index were produced on Pt/ZSM-22 than those on Pt/ZSM-23 while using the heavy waxy vacuum distillate oil as feedstock.
Highlights
Hydroisomerization of long-chain hydrocarbons to branched isomers plays an essential role in many processes in the petroleum refining industry (Gerasimov et al 2013; Liu et al 2009)
The results suggested that high conversion, high iso-dodecane selectivity, and low cracking were achieved for Pt/ZSM-22 catalyst treated by the combination of NH4+ ion-exchange and ( NH4)2SiF6
The catalytic performance for the isomerization and cracking of n-dodecane on Pt/ ZSM-22 and Pt/ZSM-23 indicated that the distribution of cracked products, either gas phase products or liquid phase products, was different
Summary
Hydroisomerization of long-chain hydrocarbons (normalparaffins) to branched isomers (isoparaffins) plays an essential role in many processes in the petroleum refining industry (Gerasimov et al 2013; Liu et al 2009). Monodimensional medium-pore molecular sieves would be the ideal catalytic materials for higher isomerization selectivity in hydroisomerization of n-octane regardless of acid strength, such as ZSM-22 and ZSM-23. Crystallized ZSM-23 zeolite which synthesized by pyrrolidine and isopropylamine and the bifunctional catalysts showed excellent catalytic performance (Chen et al 2018a, b) They (Chen et al 2017) reported the seed-assisted synthesis of ZSM-23 zeolite in the absence of alkali metal ions, and that the catalyst possesses an appropriate acid site distribution and smaller crystal size. For one-dimensional channel molecular sieves such as ZSM-22 and ZSM-23, the reported research works are more about the modification of materials, and the performance of hydroisomerization, but less research work on the shape selectivity of hydrocracking in the process of hydroisomerization (Zhang et al 2016). The reaction behaviors over both catalysts with heavy waxy vacuum distillate oil as the feedstock are analyzed systematically
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