Effects of Zn Addition into ZSM-5 Zeolite on Dehydrocyclization-Cracking of Soybean Oil Using Hierarchical Zeolite-Al₂O₃ Composite-Supported Pt/NiMo Sulfided Catalysts

Abstract

Zn-exchanged ZSM-5-Al2O3 (ZA) composite-supported Pt/NiMo (NM) sulfided catalysts were prepared using the conventional kneading method and were tested for dehydrocyclization-cracking of soybean oil. The effects of Zn addition on the activity and selectivity of products were investigated under moderate-pressure conditions of 0.5 and 1.0 MPa H2 in the temperature range of 420–580 °C. At the temperature 500 °C and higher, most of the sample soybean oil was converted at both the pressures of 0.5 and 1.0 MPa. At 1.0 MPa and 500 °C, the effects of Zn addition appeared and increased the yields of aromatics, while the catalyst without Zn produced larger amounts of products with more than C18. Further, at 0.5 MPa and 580 °C, the gas formation was inhibited in comparison to the cases of 1.0 MPa and the effects of the Zn addition also appeared and increased the yields of aromatics, while the catalyst without Zn produced larger amounts of products with more than C18. The Pt/NM/Zn(122)­ZA test catalyst produced more than 63% of liquid fuels in the range C5–C18, and the yield of aromatics was 13%, the maximum value in the present study. The following reaction routes were proposed. The structure of triglyceride is converted by hydrocracking to three molecules of aliphatic acids and propane on the surface PtNiMo sulfide on Al2O3 support. The converted aliphatic acids are decomposed through decarboxylation to hydrocarbon fragments, which are further decomposed by cracking on the acid sites of the catalyst, the surface of NiMo sulfide, Al2O3, or ZSM-5. Finally, the formed C3 and C4 olefins are transformed to aromatics through the Diels–Alder reaction on the Zn species of ZnZSM-5. On the other hand, although gases were relatively small in amount, aromatic compounds were formed significantly, suggesting that cyclization might directly occur without conversion to gaseous hydrocarbons to some extent.

Dehydrocyclization–cracking of methyl oleate by Pt catalysts supported on a ZnZSM-5–Al2O3 hierarchical composite

“…At 500 C and lower, and without the addition of Pt metal to the composite-supported NiMo catalysts, the aromatics yields were rather low. 4,32 In the present study, IO-PtZnZA and IM-Pt/ZnZA catalysts could be used for the conversion of methyl oleate and gave signicant amounts of aromatics. The selectivity of C5-C18 fractions for IO1-PtZn( 13)ZA was the highest at 62% at 500 C. For other temperatures than 500 C, the aromatics yields at 450 C were somewhat lower, while those at 550 C were higher than 15% for most the catalysts.…”

“…35 Our group reported the dehydrocyclization-cracking of soybean oil for aromatics production catalyzed by Pt/NiMo/zeolite-Al 2 O 3 hierarchical composite systems. 4,6,32 In order to treat soybean oil at as low a pressure as 1 MPa, not only NiMo suldes but also Pt metal were needed. On the other hand, methyl oleate could be treated using only NiMo suldes without Pt at as low a pressure as 0.5 MPa.…”

“…† These results are consistent with the previous results from the catalysts used in the methyl oleate, fat, and aromatics conversions. 4,6,[27][28][29][30][31][32] The pore structures of fresh IO-PtZnZSM-5-Al 2 O 3 and IM-Pt/ ZnZSM-5-Al 2 O 3 catalysts were estimated by N 2 adsorption and desorption measurements as shown in Table 1. Zn( 13)ZA, a ZnZSM-5-Al 2 O 3 composite support, had a BET-surface area (SA) of 283 m 2 g À1 , total pore volume (TPV) of 0.62 cm 3 g À1 , BJH-SA of 292 m 2 g À1 , BJH-PV of 0.61 cm 3 g À1 , and BJH-pore diameter (PD) of 11 nm.…”

Selective Decarboxylation of Fatty Acids Catalyzed by Pd-Supported Hierarchical ZSM-5 Zeolite

“…Moreover, as far as we know, this is the first time in which ZSM-5 zeolite is reported as a catalyst component for the DC of fatty acids proceeding with both high activity and selectivity. Previous works, showing that the occurrence of ZSM-5 in the makeup of several catalysts facilitated the formation first of C 17 fragments from soybean oil and methyl oleate at 500 °C, − were really aimed to promote dehydrocyclization–cracking reactions instead of just fatty acid DC.…”

Catalytic Pyrolysis of Nonedible Oils for the Production of Renewable Aromatics Using Metal-Modified HZSM-5 Catalysts

“…The dehydrocyclization cracking of soybean oil was tested using Zn-exchanged ZSM-5–Al 2 O 3 composite-supported Pt/NiMo sulfide catalysts, where the addition of zinc promoted the formation of aromatics; however, leaching of sulfur may reduce the catalyst activity and cause contamination of products. 39 The transformation of jatropha oil into aromatics using a bimetallic ZSM-5 catalyst was investigated in a continuous downflow reactor; the 10Zn5Co5Ce/ZSM-5 catalyst showed an 87.6% oil conversion with 81.9% total aromatics. 40 These results provide a practical way to prepare catalysts with a high catalytic performance in biomass-derived oil aromatization.…”