This invention describes the preparation of porous metal-organic frameworks (MOFs), consisting of organic compounds coordinated to metal ions, for use as efficient heterogeneous catalysts for olefin oligomerization.
Although homogenous catalysts currently dominate commercial processes for olefin oligomerization, it has been of great industrial interest to find heterogeneous alternatives to extend catalyst lifetime by preventing biomolecular decomposition. A wide variety of materials have been examined as heterogeneous catalysts for ethylene oligomerization including nickel oxide and larger pore materials such as nickel-exchanged mesoporous silica, but these materials exhibit poor activity and low oligomer selectivity. Recent attempts to develop heterogeneous catalysts have sought to graft known homogeneous units onto metal-organic frameworks. However, this method exhibits poor catalyst loading and severely reduces the porosity of the material, which limits its commercial viability.
The inventors combine an organic compound containing N-heterocyclic ligating groups and metal ions to generate porous MOFs. The metal ions at the nodes of the MOF function as active sites for olefin oligomerization, making them efficient heterogeneous catalysts. Azolate-based metal-organic frameworks are used as catalysts for olefin oligomerization. A particular framework MFU-41 is soaked in a nickel nitrate hydrate solution to afford the nickel-exchanged material Ni-MFU-41. This compound is treated with methylaluminoxane (MAO) to generate a material that is active for ethylene dimerization. The catalyst is loaded into a suitable slurry reactor and olefins of choice are oligomerized when introduced directly into the reactor. This potential slurry reactor may include at least one organic solvent, the olefin to be reacted, and an alkylaluminum species in amounts suitable for the catalyst. This reaction is run at a controlled temperature and pressure for a period of time to yield the desired olefin oligomer.
surpass all other heterogeneous catalysts in terms of maximizing
activity/selectivity for olefin oligomerization
Method presents high
catalytic turnover, high selectivity of catalysts, long catalyst lifetime and
catalyst reusability for efficient olefin oligomerization