Effects of Rare Earth Metal Promotion over Zeolite-Supported Fe-Cu-Based Catalysts on the Light Olefin Production Performance in Fischer-Tropsch Synthesis.

Fischer-Tropsch synthesis (FTS), a significant reaction for effective H2 utilization, is a promising approach for direct production of light olefins from syngas (H2 + CO). For the FT-Olefin process, an efficient catalyst restricting the product distribution of FTS to light olefins is required. Aligned with this goal, we synthesized 24 catalysts comprising Fe and Cu in combination with rare earth metals (La, Ce, Nd, Ho, Er) and zeolite supports (ultrastable Y and mordenite). FT-Olefin performances of these catalysts were screened using a high-throughput test system at atmospheric pressure, and then promising catalysts were tested under high pressure in a conventional test system. Results show that Nd increases selectivity to light olefins and Ho suppresses C5+ and coke formation. It is also demonstrated that zeolite-metal interaction, leading to a mixture of both acidic and basic sites, is significant in increasing light olefin production. The mordenite-supported 20 wt % Fe, 0.5 wt % Cu, and 0.5 wt % Ho catalyst provides the highest light olefin yield with the lowest coke and heavier hydrocarbon selectivity.

High-throughput synthesis and screening of new catalytic materials for the direct epoxidation of propylene.

Nanoparticles of 35 individual metals as well as their binary combinations were synthesized using High Throughput pulsed laser ablation (PLA), and collected on Al(2)O(3), CeO(2), SiO(2), TiO(2), and ZrO(2) pellets. These materials were then screened for their catalytic activities and selectivities for the partial oxidation of propylene, in particular for propylene oxide (PO), using array channel microreactors. Reaction conditions were the following: 1 atm pressure, gas hourly space velocity (GHSV) of 20,000 h-1, temperature 300 degrees C, 333 degrees C, and 367 degrees C, and feed gas composition 20 vol% O(2), 20 vol% C(3)H(6) and balance He. Initial screening experiments resulted in the discovery of SiO(2) supported Cr, Mn, Cu, Ru, Pd, Ag, Sn, and Ir as the most promising leads for PO synthesis. Subsequent experiments pointed to bimetallic Cu-on-Mn/SiO(2), for which the PO yields increased several fold over single metal catalysts. For multimetallic materials, the sequence of deposition of the active metals was shown to have a significant effect on the resulting catalytic activity and selectivity.

High-throughput nanoparticle catalysis: partial oxidation of propylene.

Partial oxidation of propylene was investigated at 1 atm pressure over Rh/TiO(2) catalysts as a function of reaction temperature, metal loading and particle size using high-throughput methods. Catalysts were prepared by ablating thin sheets of pure rhodium metal using an excimer laser and by collecting the nanoparticles created on the external surfaces of TiO(2) pellets that were placed inside the ablation plume. Rh nanoparticles before the experiments were characterized by transmission electron microscopy (TEM) by collecting them on carbon film. Catalyst evaluations were performed using a high-throughput array channel microreactor system coupled to quadrupole mass spectrometry (MS) and gas chromatography (GC). The reaction conditions were 23% C(3)H(6), 20% O(2) and the balance helium in the feed, 20,000 h(-1) GHSV and a temperature range of 250-325 degrees C. The reaction products included primarily acetone (AT) and to a lesser degree propionaldehyde (PaL) as the C(3) products, together with deep oxidation products COx.

Combinatorial Heterogeneous Catalysis-A New Path in an Old Field.

Combinatorial catalysis is the systematic preparation, processing, and testing of large diversities of chemically and physically different materials libraries in a high-throughput fashion. It also embodies microfabrication, robotics, automation, instrumentation, computational chemistry, and large-scale information management (informatics), and as such carries the promise of a renaissance in catalytic reaction engineering. Significant progress has already been made in demonstrating the speed and economic advantage of combinatorial approaches by the discovery of superior catalytic materials in a matter of hours and days, as opposed to the months and years required using traditional methods. Combinatorial methods can also significantly contribute to our understanding of catalytic function by increasing our chances of discovering totally new and unexpected catalytic materials, and by expediting the recognition of trends and patterns of structure-activity relations, from which new catalytic materials can be designed more efficiently. Combinatorial catalysis undoubtedly will be the new paradigm of catalysis research as the industry faces increasing global competition and pressure for the development of environmentally friendly processes at a time when resources for research are diminishing.

Discovery and Optimization of Heterogeneous Catalysts by Using Combinatorial Chemistry.

A novel ceramic array microreactor system has been designed and, in conjunction with resonance-enhanced multiphoton ionization (REMPI), used for the discovery of an optimum ternary catalyst composition for the dehydrogenation of cyclohexane to benzene. The catalyst library consisted of 66 ternary combinations of Pt, Pd, and In loaded on γ-Al2 O3 pellets. The optimum catalyst for the production of benzene had the composition 0.8 % Pt, 0.1 % Pd, and 0.1 % In (see diagram). The preparation and screening of the library of 66 catalysts took about 2.5 days to complete-with conventional methods this would have taken several months!