Traditional chemical reactions primarily activate reactants through heating, providing energy to overcome thermodynamic barriers and facilitating the conversion of reactants into products. In a thermal catalytic system, reactant molecules are adsorbed and activated on the surface of the catalyst, changing the chemical reaction pathway and thereby lowering the activation energy to make the reaction proceed more easily. In contrast, photocatalysis utilizes photon energy to catalyze reactions, with mechanisms and pathways that are fundamentally different from thermal catalysis, operating under mild conditions and being easy to manipulate.
In recent years, as catalytic research has deepened, scientists have discovered that photothermal co-catalysis can not only enhance the efficiency of catalytic reactions but also convert low-density solar energy into high-density chemical energy. The effective combination of these two approaches can surpass the results achievable by thermal or photocatalysis alone, and by altering reaction conditions, one can modulate the activity and selectivity of the reactions. This has immeasurable value in the fields of energy and environment, making it a focal point in the research of new catalytic technologies.
However, in traditional tubular furnace thermal catalytic reaction devices, the catalyst is loaded in the core position of the furnace, and light is mainly introduced from the side through openings made in the core. There are primarily three reaction modes:
Figure 1. Three Reaction Modes
Although these reaction modes achieve photothermal co-catalysis, the side openings disrupt the heating structure of the furnace, causing uneven heating of the catalyst. Additionally, to minimize thermal losses, the diameter of the light window is typically 1-2 cm, which is much smaller than the diameter of the light source's spot (50 cm), resulting in low utilization efficiency of the light output and negatively affecting the photothermal co-catalysis effect.
There are four main ways to improve the light energy utilization efficiency from the light source output:
There are two strategies to increase the light energy input from the light source into the device:
① Increase the light power of the source;
② Increase the light-absorbing area of the device.
PLS-SME300E H1 Xenon Lamp Source employs a brand new efficiency-enhancing light guiding structure that reduces light transmission losses while focusing most of the energy output from the light source in the center area of the light spot, effectively increasing the light power in that central region. Coupled with the PLR-RP Series Photothermal Catalytic Reaction Evaluation Device, the diameter of the light window at the light inlet has been increased from the traditional 1 cm to 3 cm, increasing the light-absorbing area to 9 times that of the traditional design. This achieves efficient transmission and maximization of the light energy output without changing the structure of the traditional thermal catalytic reactor.
Figure 2. (a) PLS-SME300E H1 Xenon Lamp Source; (b) Schematic of the Internal Efficiency-Enhancing Light Guiding Structure of PLS-SME300E H1 Xenon Lamp Source.
To avoid damaging the structure of traditional thermal catalytic reactor devices and to ensure uniformity and stability of temperature in the thermal catalytic device, the PLR-RP Series Photothermal Catalytic Reaction Evaluation Device has abandoned the existing side-opening structure on the market and adopted a new top-opening structure, introducing light from the top into the reaction device. Additionally, to prevent light losses due to the longer optical path caused by top illumination, the PLR-RP Series Photothermal Catalytic Reaction Evaluation Device has introduced a quartz light guiding column for light transmission. The introduction of the quartz light guiding column significantly improves light transmission efficiency, with a measured efficiency as high as 82%, effectively avoiding light transmission losses due to long optical paths, and outperforming reactors with shorter optical paths and side-opening structures. (Consultation Phone: 400-1161-365)
Figure 3. (a) Traditional Side Illumination; (b) Innovative Top Illumination.
Due to the poor light transmittance of solid catalysts, when the catalyst bed is too thick, the lower layer of the catalyst cannot absorb photons, which reduces the catalyst's photon absorption rate. The PLR-RP Series Photothermal Catalytic Reaction Evaluation Device innovatively adopts a top-illumination method, with two selectable lighting modes: planar illumination and ring illumination.
If a planar illumination reactor is selected, the recommended maximum bed thickness of the catalyst is 3 mm, with a maximum catalyst loading of 0.9 mL. Compared to slant and side illumination modes, the planar illumination mode offers a larger light-absorbing area for the catalyst, better uniformity in light absorption, and allows the reactants to penetrate through the catalyst for reaction, optimizing both the catalyst's light absorption efficiency and the substrate's adsorption efficiency, making it suitable for small-scale experiments.
When the catalyst loading exceeds 0.9 mL, you can also opt for a ring illumination reactor, which, paired with specially designed side-emitting quartz light columns, allows for a catalyst loading thickness of ≤3 mm while maximizing the catalyst loading up to 9 mL. In this case, the light-absorbing area of the catalyst can increase from 0.3 cm² in planar illumination to approximately 20 cm², enhancing the catalyst's light-absorbing area by nearly 70 times, significantly improving the catalyst's photon utilization efficiency.
The ring illumination reactor not only increases light utilization efficiency but also significantly enhances substrate adsorption and conversion rates, making it easy to scale up production.
Figure 4. Unique Innovative Ring Illumination Reactor of PLR-RP Series Photothermal Catalytic Reaction Evaluation Device.
To ensure uniformity in side illumination, Polifly Technology has also conducted simulation design for the structure of the light guiding column in the PLR-RP Series Photothermal Catalytic Reaction Evaluation Device, ultimately achieving a measured light emission uniformity of up to 73%, superior to the light emission uniformity of traditional xenon lamp sources, ensuring the uniform activity of catalysts at different loading positions.
Figure 5. Simulation of Light Emission Uniformity in a 50 mm Area Before (left) and After (right) Optimization.
After increasing the light energy input from the light source into the device, it is also necessary to enhance the catalyst's absorption efficiency of the light source. As illustrated in the figure below, using planar illumination as an example, if the distance between the light source and the catalyst is too great, some of the light from the source cannot reach the catalyst surface, resulting in wasted light energy; conversely, if the light source is too close to the catalyst, the light spot cannot fully cover the catalyst, causing some catalysts to remain unexcited by photons, reducing the apparent catalytic efficiency. The PLR-RP Series Photothermal Catalytic Reaction Evaluation Device has precisely calculated the distance between the quartz light guiding column and the catalyst based on the emission angle of the light and the area of the catalyst bed, ensuring maximum input light utilization efficiency and catalyst utilization efficiency.
Polifly Technology has fully leveraged its 18 years of experience in the design of photocatalytic reaction devices, conducting extensive simulations and measurements in four aspects: light source introduction, light transmission in the reactor, light contact with the catalyst, and matching the light spot area with the catalyst area. By abandoning the existing side-emitting reactor structures on the market and innovatively adopting a top-opening design combined with quartz light guiding columns, the PLR-RP Series Photothermal Catalytic Reaction Evaluation Device has been developed to create the most efficient photothermal co-catalytic reaction device.
