A Comprehensive Study of Coke Deposits on a Pt-Sn/SBA-16 Catalyst during the Dehydrogenation of Propane

Abstract

Catalytic propane dehydrogenation is an attractive method to produce propylene while avoiding the issues of its traditional synthesis via naphtha steam cracking of naphtha. In this contribution, a series of Pt-Sn/SBA-16 catalysts were synthesized and evaluated for this purpose. Bimetallic Pt-Sn catalysts were more active than catalysts containing only Pt. The catalyst with the best performance was assessed at different reaction times of 0, 60, 180, and 300 min. The evolution of coke deposits was also studied. Thermogravimetric analysis demonstrated the presence of two types of coke on the catalyst surface at low and high temperature, respectively. Raman results showed an increased coke’s crystal size from 60 to 180 min on stream, and from 180 to 300 min under reaction, Raman suggested a reduction in the crystal size of coke. Also transmission electron microscopy confirmed a more evident agglomeration of metallic particles with reaction times higher than 180 min. These results are consistent with the phenomena called “coke migration” and the cause is often explained by coke movement near the particle to the support; it can also be explained due to sintering of the metallic particle, which we propose as a more suitable explanation.

Advanced design and development of catalysts in propane dehydrogenation

“…60 In brief, Sn is deemed as an excellent additive when used in supported bimetallic Pt–Sn catalysts with thoroughly improved catalytic activity, stability, and strong anti-coking ability. 35,61–63…”

“…8 Several kinds of materials (Al 2 O 3 , CeO 2 , ZrO 2 , Ga 2 O 3 , SiO 2 , MgAl 2 O 4 /ZnAl 2 O 4 , zeolite, and carbon materials) have been utilized as supports in heterogeneous catalysis of alkane dehydrogenation. [30][31][32][33][34][35][36][37][38] The categories of supports are simply classified as oxides and other materials.…”

“…60 In brief, Sn is deemed as an excellent additive when used in supported bimetallic Pt-Sn catalysts with thoroughly improved catalytic activity, stability, and strong anti-coking ability. 35,[61][62][63] Besides the metallic Sn, other metallic additives were also reported to promote the selectivity and activity of Pt-based catalysts in the PDH process. Cai et al designed a catalyst with a Pt surface and abundant transition metals under the surface.…”

Propylene Synthesis: Recent Advances in the Use of Pt-Based Catalysts for Propane Dehydrogenation Reaction

“…It has been suggested that the coke formed on PtSn-based catalysts in PDH reaction mainly consists of three kinds of species: aliphatics, aromatics and pregraphite, with the aliphatic one constituting most of the deposit, with the C/H ratio of around 1.5 [95]. Raman studies on exhausted Pt-Sn/SBA-16 catalysts have shown an increase in coke crystal size from 60 to 180 min on stream and from 180 to 300 min under reaction [96]. These results are consistent with the so-called "coke migration phenomenon", attributed to the coke movement near the particle to the support, or to the sintering of the metallic particle.…”

Mesoporous Silica SBA-15 Supported Pt–Ga Nanoalloys as an Active and Stable Catalyst for Propane Dehydrogenation

“…Isolation of Pt atoms is an efficient strategy to inhibit the undesirable side reactions of PDH. Pt–Pt ensembles can be diluted, and propylene selectivity and catalyst stability can be enhanced when alloyed with certain inactive metals such as Sn, − Ga, − Zn, , In, , Cu, , Ni, and Ge. , These bimetallic catalysts have been studied to improve catalytic performance, among which Pt–Sn catalyst is the most classic example.…”