(617a) "Ni-MFI As a Potential Zeolitic Catalyst for Olefins Hydrogenation at Low Pressures"

The Elimination of Olefins from Processed Light Oil Fractions Is a Necessity. These Deleterious Molecules Can Form Gum Deposits on Equipment and Polymerize in Pipelines over Time during These Streams Transportation, Resulting in the Fouling of Heat Exchangers and Possible Formation of Coke. Most of the Catalysts Used so Far in Olefins Hydrogenation, Are Expensive Noble Metals, Such As Pt, Pd and Ru. Ni Catalysts Supported on Zeolite Carriers Have Been Previously Used in Hydrogenation Reactions.¹ However, in Order to Obtain a Good Hydrogenation Activity and Selectivity, Metallic Ni Species Have to be Well Dispersed on the Surface of the Zeolite Carrier. Hence, the Method of Ni Incorporation on the Support Surface Plays a Key Role in Obtaining an Active and Selective Catalyst. the Aim of This Work Is to Develop Novel Catalysts for Reducing Olefins Content without Affecting Octane Numbers of Light Distillates (no hydrogenation of aromatics). Ni-Doped Siliceous MFI Materials Have Thus Far Shown Interesting Performances As It Is Here Presented. the Ni Was Added during the Zeolite Formation Step and Anchored during the Crystallization Process.² Ni-MFI Catalysts Were Prepared with Various Metal Loadings. All Catalysts Were Characterized By XRD, TPR, ICP, FTIR and BET. Activity Tests for Toluene and 1-Octene Hydrogenation Were Conducted at Low Pressures (< 100 psi) in a Bench Scale Packed Bed Reactor. the Hydrogenated Products Were then Analyzed By a Gas Chromatograph (GC) Equipped with a Flame-Ionization Detector (FID). the Spent Catalysts Were Characterized By XRD, BET, DSC, TGA and DTA. When Using 1 Wt% Ni-MFI the Hydrogenation of Toluene Was Zero below 200 °C but Negligible at 200 ^o C (1 wt %). However, Increasing the Ni Content to 2 % Resulted in a Moderate Activity of the Catalyst with 100 % Selectivity Towards Methyl-Cyclohexane (MCH). Increasing the Ni to 3 % Resulted in the Complete Conversion of Toluene to MCH at Very Low Pressures. This Directed Our Attention to the Possibility of Hydrogenating Olefins at Milder Conditions. 1-Octene Was Selected As a Model Molecule for the Hydrogenation Tests. the Conversion of 1-Octene to n-Octane Was Observed after a Very Short Time (~ 20 min) with All the Ni-MFI Catalysts Tested.  When Using 1 Wt. % Ni-MFI Isomerization of 1-Octene Began to be Observed after 13 h on Stream. Increasing the Ni to 2 Wt. % Increased the Time at Which Isomerization Occurred, to 40 h. DSC Data in air Showed a Small Exothermic Peak of Coke at ~ 300 ^o C. Isomerization of 1-Octene on Ni-MFI Might be Attributed to the Formation of Some New Acid-Sites Promoted By the Formed C-Layer.  the Catalyst with 1 % Ni-MFI Can be Used for Reducing Olefins Content in Upgraded Feedstocks without Hydrogenation of Aromatics and Retaining High Octane Numbers of the Processed Feedstock.  

References

(1)  A. Masalska, J. Appl. Catal. A 2005, 294, 260-272.  

(2)   G. Vitale, H. Molero, E. Hernandez, S. Aquino, V. Birss, P. Pereira-Almao J. Appl. Catal. A: Gen 2013, 452, 75-87