(544d) Controlled Synthesis of Pt-Sn/Al2O3 catalysts and Their Application in the Hydrodeoxygenation of Bio-Based Succinic Acid

Patrick M. Howe¹, Joshua Gopeesingh¹, Jesse Q. Bond^1,*

Department of Biomedical and Chemical Engineering, Syracuse University, Syracuse, NY 13244, United States

Bio-based succinic acid is a promising building block for downstream commodities. Specifically, it can serve as a renewable alternative to petrochemically sourced maleic anhydride in most or all of its industrial applications. In order for succinic acid to be economically competitive with (butane-derived) maleic anhydride, it is vital that it be converted with exceptionally high selectivity. Our aim is to accomplish this goal through a combination of efforts in catalyst design and reaction engineering.

The addition of oxophilic secondary metals, such as Sn or Cu, to primary noble metals, such as Pt or Ru, can have important impacts on the stability and selectivity of reactions catalyzed on these metal surfaces^1,2. Kinetic analysis is only truly meaningful when performed on a well-characterized surface; accordingly, a major hurdle in understanding the kinetic effects of oxophilic promoters is the difficulty in synthesizing technical catalysts comprised of nanoscale, bimetallic clusters that have uniform size and composition and are stable under reaction conditions. For example, traditional methods of bimetallic catalyst synthesis (e.g. incipient wetness impregnation) create supported nanoparticles that have a heterogenous distribution of particle sizes and metal compositions; therefore, our kinetic observations of these systems in laboratory reactors reflect an average rate and selectivity of the wide distribution of sites that are no doubt present in the typical working catalyst. The goal of our project is to leverage the surface charges of metal oxides when they are placed in solution for creating supported catalysts with homogenous bimetallic sites. The strong electrostatic adsorption (SEA) method utilizes the fact that metal oxides, when placed in solution, will develop a net surface charge that is a function of the pH of solution^3,4. When the pH of the solution is at the oxide’s point of zero charge (PZC) the net surface charge is neutral^3,4. Above the PZC the surface will be deprotonated giving a net negative charge and the opposite is true below the PZC^3,4. We propose that synthesizing catalysts via SEA will allow Sn complexes to be selectively adsorbed to Pt nanonparticles supported on γ-alumina by taking advantage of the difference in surface charges of the metal oxides⁵. The project explores different approaches to the SEA method and will utilize tools, such as TEM, XRD, and XPS, in conjunction with Brookhaven National Laboratory, to characterize catalyst structures. Synthesized catalysts are used in hydrodeoxygenation of propionic acid and methanation of carbon monoxide, which provide a clearer picture of how Sn addition impacts selectivity and activity of the catalyst. It is our goal to create a realistic, low cost and scalable synthesis of Pt-Sn catalysts that will be useful in targeting the desired downstream products of succinic acid and increasing its viability as a green building block in industry.

References:

[1] S.G. Wettstein, J.Q. Bond, D.M. Alonso, H.N. Pham, A.K. Datye, J.A. Dumesic, Appl. Catal.

B: Environ. 117-118 (2012) 321-329.

[2] R.D. Adams, E. Trufan, Philos. T. Roy. Soc. A 368 (2010) 1473-1493.

[3] J. Park, J.R. Regalbuto, J. Colloid Interface Sci. 175 (1995) 239-252.

[4] M. Schreier, J.R. Regalbuto, J. Catal. 225 (2004) 190-202.

[3] H.-R. Cho, J.R. Regalbuto, Catal. Today 246 (2015) 143-153