Promotional Effect of Pd Addition on the Catalytic Activity of Composite Pt-Pd/AlSBA-15–β Catalyst for Enhanced n-Heptane Hydroisomerization

Karolina Jaroszewska,Janusz Trawczyński,Monika Fedyna,Rafał Łużny,Aleksandra Masalska

doi:10.3390/catal11030377

Abstract

Hierarchical AlSBA-15–zeolite materials were utilized as a supports for preparing hydroisomerization catalysts. Detailed consideration was given to: (i) the effect of the zeolite type introduced into AlSBA-15–zeolite composites (where zeolite is β, mordenite or ZSM-5) as well as (ii) the promotion effect of Pd addition. The composites showed higher activity in isomerization as compared to Pt/AlSBA-15. The enhanced isomerization efficiency were explained by the appropriate metallic and acidic function as well as suitable transport properties. The modification of the hydrogenating function by Pd incorporation increases the hydroisomerization efficiency of Pt-Pd/AlSBA-15–β catalyst. Over bimetallic Pt-Pd/AlSBA-15–β, the high yields of isomers (68 wt%) with respect to 50 wt% for a control catalyst. The most promising Pt-Pd/AlSBA-15–β catalyst allows to improve research octane number from 0 to the 74 value.

Highlights

Global environmental concerns and more drastic requirements for advanced vehicle fuels with maximum combustion efficiency and minimum emissions are leading drivers to improve existing processes or to create innovative technologies for their production
It is crucial to confirm the structure of zeolite in AlSBA-15–zeolite supported catalysts since the synthesis of biporous support relies on AlSBA-15 phase crystallisation in the presence of zeolite particles and in consequence the contact of zeolite particles with the acidic environment takes place
In this work we reported the hydroisomerization of n-heptane (n-C7) towards the high octane isomers with by using bifunctional Pt(Pd) catalysts supported over AlSBA-15– zeolite hierarchical composites

Summary

Introduction

Global environmental concerns and more drastic requirements for advanced vehicle fuels with maximum combustion efficiency and minimum emissions are leading drivers to improve existing processes or to create innovative technologies for their production. In the case of gasoline, the requirements for high-quality fractions include, inter alia low aromatics content together with maintaining a sufficiently high octane number (ON). In modern refineries, the branched fractions of C4–C6 alkanes are used to obtain high ON components what makes it possible to reduce the use of harmful aromatics. Fractions containing n-alkanes with carbon numbers more than 6, such as C7–C9, are usually present in the feed stream for catalytic reforming and under the reforming conditions they undergo isomerization and dehydrocyclisation to aromatic compounds. Since the regulations aim to decrease aromatic hydrocarbons, it seems that, as in the case of C4–C6 alkanes, an alternative is their hydroisomerization to environmentally friendly gasoline high ON components. There is still no suitable technology for the conversion of C7–C9 cuts into branched fractions because of several problems with their effective hydroisomerization. Due to the high reactivity of the C7–C9 hydrocarbons, they are prone

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