Catalytic Complexes for the Production of Butadiene and Para-xylene

Transition metal catalysed transformations are an important synthetic tool in modern organic chemistry, because of their high efficiency, selectivity, and an economical use of the reactants. The metal complexes are reused in many catalytic cycles, and therefore a metal catalyst is able to selectively convert a large number of substrate molecules to products. Pincer complexes are remarkably stabile species, because of their terdentate chelating structure and stable carbonmetal sigma bond. The high stability of the complexes and the tight metal ligand interaction make pincer complexes particularly suitable for immobilization to solid or dendrimeric support creating robust recyclable catalysts. In our present proposal it is planned to use pincer complex for industrially important petrochemical synthesis such as p-xylene from 1-hexene and butadiene from butane. The main source of olefins is steam cracking, and fluid-catalytic-cracking, and catalytic dehydrogenation. The abundance and lower cost of light alkanes in Saudi Arabia has generated interest in oxidative catalytic conversion of light alkanes to olefins, oxygenates or nitriles in the petroleum and petrochemical industries. The demand for petrochemicals such as p-xylene and butadiene is expected to increase significantly in the near future. Oxidation of light alkanes such as ethane is an effective process. However, when higher feedstocks are used, controlling the oxidation to form olefins can be difficult. In order to handle this situation, ethylene can be used as oxidizing agent for higher alkanes through a hydrogen transfer reaction. The butadiene production by metathesis process is exothermic and therefore a shift in the equilibrium to form butenes and ethane is expected. In the case of excess ethylene, a mixture of ethylene, ethane and butenes are expected products. The selective formation of p-xylene is an important process as high purity of p-xylene is required for the production of the dimethyl ester of terephthalic acid, which is copolymerized with ethylene glycol to produce polyethylene terephthalate (PET). In our current approach 1-hexene dehydrogenation to hexadiens and the dienes produced underwent a subsequent Diels-Alder reaction with ethylene in-situ to produce p-xyelene. The study will be conducted at the Center for Refining & Petrochemicals, Research Institute (RI), KFUPM in collaboration with Caltech. The KFUPM-Caltech research program will be headed by Prof. Robert Grubbs with Prof. Sulaiman S. Al-Khattaf, CRP, KFUPM. The tasks include literature review, catalyst preparation, characterization, and catalyst evaluation. The catalytic evaluation will be done in a fully integrated, fixed bed continuous flow reactor system (BELCAT, Japan) or batch type reactor. The catalysts with highest activity and best selectivity for olefins will be tested for long time period. An international consultant with wide experience in the catalysis of aromatics reactions will render his services specifically in catalyst formulation task.