Catalytic Activity of Pt Loaded Zeolites for Hydroisomerization of n-Hexane Using Supercritical CO₂

Abstract

The present study investigates the synthesis of novel strontium (Sr) and barium (Ba) modified crystalline zeolites including Zeolite Socony Mobil-5 (ZSM-5) and Mordenite (MOR) utilizing a batchwise ion-exchange method with an appropriate chloride solution of 3 N at pH 7.2 and 50 °C. Modified zeolites (Ba-ZSM-5 and Ba-MOR, Sr-ZSM-5 and Sr-MOR) were coated with an inert metal (Pt) by a novel supercritical CO 2 method using PtMe 2 COD as a precursor for n-hexane hydroisomerization in a microreactor unit at different temperatures (250−325 °C), H 2 /HC ratios of 3, 6, and 9, and a pressure of 5 bar. The acidic and physical features of Pt loaded zeolites were systematically characterized using FT-IR, XRD, BET surface area measurements, TGA, and TEM techniques. It is found that the metal loading in scCO 2 results in more uniform and very small metal nanoparticle (1.37 nm) dispersion with high stability after reduction. It is also revealed that high loading pressure in scCO 2 (280−300 bar) results in higher catalytic activity and surface area. The maximum conversion and selectivity of about 80 and 90% were achieved for n-hexane isomerization at 275 °C and a H 2 /HC ratio of 6 for Pt/Sr-ZSM-5 catalyst. Results reported that Pt loaded over all zeolites (H-MOR, Sr-MOR, Ba-MOR, H-ZSM-5, Ba-ZSM-5, and Sr-ZSM-5) by the scCO 2 method showed the minimum production of cracking products (C 1 −C 5 ) and maximum isomeric products including iso-C 6 isomers (2,2-DMB, 2,3-DMB, 2-MP, and 3-MP). Furthermore, the overall results of the rate of reaction revealed that Pt/Sr-ZSM-5 and Pt/Ba-ZSM-5 catalysts showed a better rate of isomerization (46.44%) and conversion (47%) for n-hexane at 300 °C and a H 2 /HC ratio of 9 with a minimum rate of cracking. However, it is concluded that the small, pored size Pt loaded ZSM-5 zeolite showed the highest catalytical activity compared to large pored MOR zeolite making it of great interest for diesel and gasoline formation in the oil refining industry.

Covalent Organic Frameworks for Simultaneous CO2 Capture and Selective Catalytic Transformation

“…However, difficult recycle of homogeneous catalysts limits their practical application. To this end, a variety of heterogeneous catalysts have been developed in the last ten years [14][15][16][17][18][19]. For instance, Ahmed and Sakthivel synthesized a series of amine functionalized silicoaluminophosphate (SAPO-34) materials that exhibited promising catalytic capability with high epichlorohydrin conversion (>80%) and selectivity to cyclic carbonate (>94%) [20].…”

Anchoring Water Soluble Phosphotungstic Acid by Hybrid Fillers to Construct Three-Dimensional Proton Transport Networks

“…XRD analysis was conducted by a diffractometer (D/Max-III C, Rigaku, Japan) with CuKa radiation operating at 40 kV and 200 mA [ 33 , 34 , 35 ] with a scan rate of 5.00°·min −1 .…”

Isomerization of Oleic Acid over Acid Zeolites: Design of Experiments and Proposal of a Novel Kinetic Mechanism

“…4 This type of isomerization is widely used for alkanes to increase the octane number of gasoline. 9,10 Nevertheless, carboxylic acids are known as poisons for the isomerization process, making their applicability in the synthesis of bc-FA challenging. 7 Other catalysts such as metal−organic frameworks have also been employed to convert fatty acids to liquid fuels.…”