Understanding the spatial organization and dynamics of physicochemical processes in operating catalytic reactors is essential for optimizing their performance. Unfortunately, the power of NMR-based techniques is impaired in such studies due to severe broadening and distortions of NMR signals caused by the heterogeneity of granular catalyst. To surmount this critical obstacle, we utilized for the first time hollow spheres used as catalyst supports. Granular beds of the catalyst comprising Rh nanoparticles supported on hollow alumina spheres provided an excellent magnetic field homogeneity within the NMR detection volume. This enabled acquisition of 1H NMR spectra of reacting gases with linewidths up to 0.1 ppm under flow conditions. Consequently, operando magnetic resonance spectroscopy (MRS) of heterogeneous propene hydrogenation allowed quantitative monitoring of substrate-to-product conversion profiles along the catalyst bed with 1.25 mm spatial resolution for short time. The reaction zone was further visualized by infrared thermography, correlating the localization of heat release with chemical conversion in this exothermic reaction. Chemical shift-selective 3D magnetic resonance imaging (MRI) enabled separate spatial visualization of the reactant and product distributions within the heterogeneous catalytic system. MRS experiments using parahydrogen for signal enhancement conclusively confirmed high magnetic field homogeneity by resolving the antiphase shape of the NMR signals of hyper-polarized propane and enabling spatially resolved detection of hyperpolarization buildup and decay within the granular catalyst layer. Overall, the results demonstrate that the combination of hollow catalyst supports with advanced NMR techniques enables non-invasive operando analysis of gas-phase catalytic processes with high spatial and spectral resolution, and offers new opportunities for studying reaction mechanisms and hyperpolarization dynamics in heterogeneous systems.

New bimetallic Pd–Mn catalysts supported on the carbon material Sibunit have been obtained and studied for the process of producing ethylene by acetylene hydrogenation. The composition, structure, morphology and electronic state of the active phase have been studied in detail depending on the temperature of treatment in hydrogen and the Pd/Mn ratio by XRD, XANES, EXAFS, TEM, XPS. It has been found that the active species are the nanoparticles of intermetallic tetragonal structure Pd3Mn2 that formed during the treatment of Pd–Mn/Sibunit in H2 at 500 °C. Increasing the reduction temperature to 600–700 °C provides an increase in the proportion of the Pd3Mn2 phase due to more complete involvement of palladium in the interaction with manganese. Pd3Mn2 nanoparticles are less active but more selective than Pd nanoparticles due to changes in the geometry of active sites and their electronic state. It is shown that catalysts containing a twofold molar excess of Mn relative to Pd are characterized by the presence of more dispersed bimetallic particles than samples containing less manganese, due to which they are characterized by higher activity. Pd–Mn/Sibunit catalysts provide a high ethylene yield (up to 75

Nuclear magnetic resonance is extremely attractive for operando studies of chemical reactors. However, the heterogeneous catalyst particles placed inside an NMR probe greatly affect the uniformity of the magnetic field. This problem is especially acute when studying heterogeneous hydrogenation processes using parahydrogen. Despite the increased sensitivity due to hyperpolarization, under conditions of a strong heterogeneity of the magnetic field, the antiphase nature of the NMR signals leads to a partial or even a complete loss of spectroscopic information due to significant NMR signal broadening. The use of intramolecular multiple-quantum coherences in 2D NMR allows one to circumvent this problem. We used the COSY pulse sequence to acquire 2D NMR spectra of the reaction mixture upon propene hydrogenation with parahydrogen. The selection of double-quantum coherences in the resulting 2D NMR spectrum allowed us to obtain a highly resolved NMR spectrum under conditions of severe inhomogeneity of the magnetic field caused by the presence of catalyst granules.

The Ir–P@SiO2 catalyst was prepared by immobilizing a dimeric Ir complex via interaction with –PPh2 groups of 2-diphenylphosphinoethyl-functionalized silica gel. The catalyst was tested in hydrogenations of butynes (1-butyne and 2-butyne) with parahydrogen. The experimentally observed 1H NMR spectra of hyperpolarized products are well-fitted with theoretical PASADENA spectra simulated with the use of spin density matrix formalism. The analysis of 1H NMR spectral lines of the products reveals that the catalyst is stereoselective in such reactions and the syn-addition of p-H2 takes place. Moreover, we demonstrate that the lineshape of hyperpolarized NMR signals of cis-2-butene is indicative of the mechanism of its formation. It was found that 2-butene produced during 1-butyne hydrogenation is formed from hyperpolarized 1-butene via isomerization. The maximum observed 1H polarization levels for 1-butene were 5.2 ± 0.5

Hyperpolarization (HP) techniques, such as Parahydrogen-Induced Polarization (PHIP), Signal Amplification by Reversible Exchange (SABRE), and dissolution Dynamic Nuclear Polarization (d-DNP), significantly enhance the sensitivity of nuclear magnetic resonance (NMR) spectroscopy for chemical analysis and metabolic imaging. However, the high cost of equipment, ranging from tens of thousands to millions of dollars, limits accessibility of hyperpolarization for the broad scientific community. In this work, we aim to mitigate some of the challenges by developing a cost-effective solution for parahydrogen (pH2)-based PHIP and SABRE HP methods. A custom coil-winding machine was designed to fabricate solenoid magnet coils, which were then evaluated for their magnetic field profiles, demonstrating a high degree of magnetic field homogeneity. A model 1H SABRE experiment successfully implemented the constructed solenoid, achieving efficient hyperpolarization. Additionally, the solenoid magnet can be utilized for in situ detection of hyperpolarization when integrated with a low-field NMR spectrometer, reducing the total setup cost to a few thousand dollars. These findings suggest that our approach makes HP technology more affordable and accessible, potentially broadening its applications in chemical and biomedical research, as well as educational settings involving undergraduate student researchers. This work provides a practical pathway to lower the financial barriers associated with pH2 HP setups.

The modifying effect of cobalt on palladium in novel bimetallic Pd-Co catalysts supported on alpha-alumina was studied, and the catalytic properties of Pd-Co/alpha-Al2O3 samples in the direct selective hydrogenation of acetylene to ethylene were carefully investigated. It was shown that the temperature of catalyst treatment in hydrogen and the Pd/Co ratio are effective tools for varying nanoparticles composition of the Pd(1-x)Cox solid solution formed in the catalysts. Increasing the reduction temperature and decreasing the Pd/Co molar ratio leads to a gradual increase in the Co content in the Pd(1-x)Cox particles, which provides a slight decrease in activity, but an improvement in ethylene selectivity and the yield of the target product. Using XRD, XPS, HR TEM, TPD-C2H4 and TPR-H-2 it was found that an increase in the cobalt concentration in Pd(1-x)Cox nanoparticles suppresses the ability of the active component to activate hydrogen, enhances the electron interaction between Pd and Co and ensures rapid desorption of ethylene from the catalyst surface. The highest selectivity was demonstrated on supported Pd(1-x)Cox nanoparticles with the value of x > 0.4. It was also established that Pd-Co/alpha-Al2O3 samples with Pd:Co = 1:3 and 1:4 reduced in H-2 at 700 degrees C provide a high and stable ethylene yield at a level of 68 % due to the enhanced influence of cobalt on the electronic and geometric properties of palladium in Co-rich PdCo nanoparticles.

Hyperpolarized (HP) MRI provides enhanced signals over conventional MRI due to the increase in nuclear spin polarization by orders of magnitude compared to thermal polarization. Therefore, HP MRI can be successfully utilized toward imaging of low-density gases in void spaces, such as human lungs. Specifically, in clinical pulmonary imaging, HP MRI employs a gaseous contrast agent that fills the lungs during inhalation under physiologically relevant conditions prior to imaging. FDA-approved HP 129Xe gas can now be used as the first HP inhalable gaseous contrast agent for functional lung imaging in adults and pediatric patients above 12 years for diagnosis and monitoring responses to the treatment of many pulmonary diseases. However, despite the substantial success of HP 129Xe in research settings, the production and MRI of this novel contrast agent remain expensive and not universally available on clinical MRI scanners. An alternative approach is to deploy a proton-hyperpolarized gas that is cheap and fast to produce and can be detected on any clinical MRI scanner without any modification. Hyperpolarized propane gas has recently emerged as a potential next-generation hyperpolarized inhalable contrast agent. Here, the relaxation dynamics of two deuterated hyperpolarized propane isotopologues have been explored at clinically relevant conditions of 1 atm gas pressure and 0.35 and 1.4 T magnetic fields using pairwise addition of parahydrogen to a corresponding unsaturated precursor over the heterogeneous Rh/TiO2 catalyst. The T1 relaxation time of HP propane-d6 gas (0.91±0.03 s) at 1.4 T was found to be similar to that of HP propane gas (0.81±0.06 s) because the dominating relaxation mechanism is due to the coupling of the nuclear spins to the molecular rotation of these two propane gas isotopologues. Moreover, the effective polarization decay constant increases for HP propane-d6 to 1.35±0.05 s (and for HP propane to 1.35±0.10 s) at 0.35 T, pointing to the likely "partial" presence of the long-lived spin states (LLSS) at this clinically relevant field, corresponding to the intermediate spin-spin coupling regime of the two parahydrogen-derived hyperpolarized sites. Furthermore, the pilot feasibility of rapid lung ventilation imaging with 1 × 1 × 9 mm2 voxel-size spatial resolution using a clinical 0.35 T open MRI scanner was demonstrated by inflating HP propane-d6 gas in excised rabbit lungs, despite the reduction of the HP gas relaxation constant to 0.78 ± 0.02 s in the lungs.

The Signal Amplification By Reversible Exchange (SABRE) technique provides enhancement of Nuclear Magnetic Resonance (NMR) signals up to several orders of magnitude using chemical exchange of a substrate and parahydrogen on an iridium complex. Therefore, the availability of such a catalytic complex to a broader community is an absolutely vital step for dissemination of the groundbreaking SABRE methodology. The most common SABRE catalyst, which is activated in situ, is based on Ir-IMes system (IMes = 1,3-Bis(2,4,6-trimethylphenyl)imidazol-2-ylidene). Earlier approaches for the synthesis of this catalyst often relied on specialized equipment and were limited to a comparatively small scale. This, in turn, increased the barrier of entry for new scientists to the area of SABRE hyperpolarization. Here, we present a robust, inexpensive, and easy to reproduce synthetic procedure for the preparation of this SABRE catalyst, which does not require specialized inert atmosphere equipment like a glove box or Schlenk line. The synthesis was validated on the scale of several grams vs. tens of milligrams scale in the reported approaches. The resulting SABRE catalyst, [Ir(IMes)(COD)Cl], was activated in situ and further evaluated in hyperpolarization experiments resulting in signal enhancements comparable to (or higher than) those for the catalyst prepared using Schlenk line equipment.

The universal, user-friendly online iOk Platform for automatic recognition of any type of objects in images based on deep machine learning is presented. Services aggregated in the iOk Platform significantly reduce the time spent on quantitative image analysis, decrease the influence of the subjective factor and increase the accuracy of the analysis by expanding the set of data that can be analyzed automatically. It is shown how the services can be used to analyze scanning transmission electron microscopy images obtained in heterogeneous catalysis studies, allowing for measurements of thousands of objects in an image, as well as simultaneous analysis of objects of different types, namely: nanoparticles and single sites.

The research is devoted to the study of active component formation in the novel Pd-Co catalysts supported on carbon material Sibunit. It was shown that 0.5 %Pd-0.5 %Co/C samples exhibit high ethylene yield in the acetylene hydrogenation process due to the presence of fcc PdxCo(1-x) particles. According to in situ XRD-TPR analysis, solid solution formation begins during the reduction of samples in H2 at T >= 500 degrees C. Using the EXAFS, XRD and EDX it was established that H2-treatment at 500 degrees C leads to the formation of -Pd0.6Co0.4 particles and an increase in the reduction temperature to 600 and 700 degrees C is accompanied by the enrichment of the Pd-Co-phase with cobalt to -Pd0.5Co0.5 and -Pd0.45Co0.55 compositions, respectively. The ethylene yield on Pd-Co/C catalysts reduced at 500, 600 and 700 degrees C is 56, 66 and 68 %, respectively, which significantly exceeds the ethylene quantity obtained on monometallic Pd/C samples (-52 %). It is assumed that the excellent selectivity of Pd-Co/C samples treated in H2 at 600 and 700 degrees C is due to an increase in the amount of palladium atoms surrounded by cobalt and a change in the palladium electronic state (XPS).

Proton-hyperpolarized contrast agents are attractive because they can be imaged on virtually any clinical MRI scanner, which is typically equipped to scan only protons rather than heteronuclei (i.e., anything besides protons, e.g., 13C, 15N, 129Xe, 23Na, etc.). Even though the lifetime of the proton spin hyperpolarization is only a few seconds, it is sufficient for inhalation and scanning of proton-hyperpolarized gas media. We demonstrate the utility of producing hyperpolarized propane gas via heterogeneous parahydrogen-induced polarization for the purpose of ventilation imaging in an excised rabbit lung model. The magnetization of protons in hyperpolarized propane gas is similar to that of tissue water protons, making it possible to rapidly perform lung ventilation imaging with a 0.35 T clinical MRI scanner. Here, we demonstrate the feasibility of rapid (2 s) lung ventilation MRI in excised rabbit lungs using hyperpolarized propane gas with a 1 x 1 mm2 pixel size using a 50 mm slice thickness, and a 1.7 x 1.7 mm2 pixel size using a 9 mm slice thickness.

NMR hyperpolarization dramatically improves the detection sensitivity of magnetic resonance through the increase in nuclear spin polarization. Because of the sensitivity increase by several orders of magnitude, additional applications have been unlocked, including imaging of gases in physiologically relevant conditions. Hyperpolarized 129Xe gas recently received FDA approval as the first inhalable gaseous MRI contrast agent for clinical functional lung imaging of a wide range of pulmonary diseases. However, production and utilization of hyperpolarized 129Xe gas faces a number of translational challenges including the high cost and complexity of contrast agent production and imaging using proton-only (i.e., conventional) clinical MRI scanners, which are typically not suited to scan 129Xe nuclei. As a solution to circumvent the translational challenges of hyperpolarized 129Xe, we have recently demonstrated the feasibility of a simple and cheap process for production of proton-hyperpolarized propane gas contrast agent using ultralow-cost disposable production equipment and demonstrated the feasibility of lung ventilation imaging using hyperpolarized propane gas in excised pig lungs. However, previous pilot studies have concluded that the hyperpolarized state of propane gas decays very fast with an exponential decay T 1 constant of ∼0.8 s at 1 bar (physiologically relevant pressure); moreover, the previously reported production rates were too slow for potential clinical utilization. Here, we investigate the feasibility of high-capacity production of hyperpolarized butane gas via heterogeneous parahydrogen-induced polarization using Rh nanoparticle-based catalyst utilizing butene gas as a precursor for parahydrogen pairwise addition. We demonstrate a remarkable result: the lifetime of the hyperpolarized state can be nearly doubled compared to that of propane (T 1 of ∼1.6 s and long-lived spin-state T S of ∼3.8 s at clinically relevant 1 bar pressure). Moreover, we demonstrate a production speed of up to 0.7 standard liters of hyperpolarized gas per second. These two synergistic developments pave the way to biomedical utilization of proton-hyperpolarized gas media for ventilation imaging. Indeed, here we demonstrate the feasibility of phantom imaging of hyperpolarized butane gas in Tedlar bags and also the feasibility of subsecond 2D ventilation gas imaging in excised rabbit lungs with 1.6 × 1.6 mm2 in-plane resolution using a clinical MRI scanner. The demonstrated results have the potential to revolutionize functional pulmonary imaging with a simple and inexpensive on-demand production of proton-hyperpolarized gas contrast media, followed by visualization on virtually any MRI scanner, including emerging bedside low-field MRI scanner technology.

Hyperpolarized 129Xe gas was FDA-approved as an inhalable contrast agent for magnetic resonance imaging of a wide range of pulmonary diseases in December 2022. Despite the remarkable success in clinical research settings, the widespread clinical translation of HP 129Xe gas faces two critical challenges: the high cost of the relatively low-throughput hyperpolarization equipment and the lack of 129Xe imaging capability on clinical MRI scanners, which have narrow-bandwidth electronics designed only for proton (1H) imaging. To solve this translational grand challenge of gaseous hyperpolarized MRI contrast agents, here we demonstrate the utility of batch-mode production of proton-hyperpolarized diethyl ether gas via heterogeneous pairwise addition of parahydrogen to ethyl vinyl ether. An approximately 0.1-liter bolus of hyperpolarized diethyl ether gas was produced in 1 second and injected in excised rabbit lungs. Lung ventilation imaging was performed using sub-second 2D MRI with up to 2x2 mm2 in-plane resolution using a clinical 0.35 T MRI scanner without any modifications. This feasibility demonstration paves the way for the use of inhalable diethyl ether as a gaseous contrast agent for pulmonary MRI applications using any clinical MRI scanner. Hyperpolarized diethyl ether gas was produced via heterogeneous pairwise parahydrogen addition to ethyl vinyl ether (a.k.a. vinamar) anesthetic gas and employed for a pilot feasibility demonstration to record sub-second 2D ventilation MRI of excised rabbit lungs on a clinical 0.35 T MRI scanner without any modifications to the scanner's hardware or software. image

The immobilization of dimeric [M2(COD)2(μ–Cl)2] complexes (M – Rh or Ir) by the interaction with -SH groups of 3-mercaptopropyl-functionalized silica gel leads to RhCl–S–SiO2 and IrCl–S–SiO2 catalysts active in hydrogenations of propene and propyne. Nuclear magnetic resonance enhancement in parahydrogen-induced polarization experiments was studied in a wide range of hydrogenations conditions (25–120 °C, 1.0–3.9 bar). The structural transformations were studied using ex situ X-ray photoelectron spectroscopy (XPS). It was established that IrCl–S–SiO2 demonstrated greater thermal stability in the hydrogenation of both propene and propyne in comparison with RhCl–S–SiO2. The beneficial effect of propyne was elucidated for thermal stability of studied catalysts and for the efficiency of the pairwise hydrogen addition. This can be explained by more efficient binding of the C≡C triple bond to an active center. The increase in reaction pressure typically leads to higher conversion in hydrogenations for both catalysts, but also decreases the temperatures sufficient for the reduction of anchored complexes with the formation of metal nanoparticles, which was confirmed by XPS.

Changes in the composition of immobilized [M(COD)Cl]2–NH2–C3H6–SiO2 and [M(COD)Cl]2–P(Ph)2–C2H4–SiO2 (where M = Ir, Rh) catalysts in the gas-phase selective hydrogenation of propylene, propyne, and 1,3-butadiene with parahydrogen (p-H2) have been studied by the XPS method. It has been proposed that the M/Cl atomic ratio should be used as an indicator of the structural stability of the anchored complex both at the sample synthesis stage and in the reaction. Based on comparison of XPS data and results of catalytic tests using parahydrogen-induced nuclear polarization, it has been shown that the stability of the anchored [M(COD)Cl]2–Linker–SiO2 complex during hydrogen activation is a key factor in the catalytic behavior of the systems. The stability of the complex is affected not only by the chosen metal and linker, but also by the nature of the substrate subjected to hydrogenation.

Symmetric molecules exist as distinct nuclear spin isomers (NSIMs). A deeper understanding of their properties, including interconversion, requires efficient techniques for NSIMs enrichment. Selective hydrogenation of acetylene with parahydrogen (p-H2) was used to achieve the enrichment of ethylene NSIMs and to study their equilibration processes. The effect of stereoselectivity of H2 addition to acetylene on the imbalance of ethylene NSIMs was experimentally demonstrated by using different heterogeneous catalysts (an immobilized Ir complex and two supported Pd catalysts). The interconversion of NSIMs with time during ethylene storage was studied with NMR spectroscopy by reacting ethylene with bromine water which renders the p-H2-derived protons in the produced 2-bromoethan(2H)ol (BrEtOD) magnetically inequivalent, thereby revealing the non-equilibrium nuclear spin order of ethylene. A thorough analysis of the shape and transformation of the 1H NMR spectra of hyperpolarized BrEtOD allowed us to reveal the initial distribution of produced ethylene NSIMs and their equilibration processes. Comparison of the results obtained with different catalysts was key to properly attributing the derived characteristic time constants to different NSIMs interconversion processes: ~ 3-6 s for interconversion between NSIMs with the same inversion symmetry (i.e., within g or u manifolds) and ~ 1700-2200 s between NSIMs with different inversion symmetries.

A protocol has been proposed for modifying a porous alumina support by NO treatment to increase the resistance of metal particles on the support to sintering. The stabilization effect by forming AlNxOy species has been clearly demonstrated for supported platinum catalysts.

Magnetic resonance imaging (MRI) is a unique tool for operando studies owing to its non-invasive manner of signal detection. MRI can provide information about structure of the reactor, distribution of the reagents and products in the reactor, and heat and mass transport processes. However, the heterogeneous solid phase of a catalyst in a reactor largely distorts the static magnetic field of an MRI instrument, which leads to a major loss in spectroscopic resolution and measurement sensitivity. On top of that, many chemical reactions involve gases, so that the reduced spin density compared to liquids is yet another complication in such studies. To overcome these challenges, a proper choice of model catalytic reactors for NMR-based experiments is required. In this study, the configuration of model catalytic reactors was varied to explore its effect on the spatially resolved 1 H NMR spectra acquired during heterogeneous hydrogenation of propene to propane with parahydrogen over several supported metal catalysts. The results demonstrate that a judicial choice of a reactor geometry in combination with signal enhancement provided by parahydrogen makes such studies feasible and informative.

Parahydrogen Induced Polarization (PHIP) is NMR hyperpolarization technique that has matured from fundamental science to a biomedical tool for production of hyperpolarized MRI contrast agents. The spin order of nascent parahydrogen-derived protons can be employed directly for enhancement of their NMR signals or for polarization transfer to other nuclei in the hydrogenation product. In this work, we study the process of pairwise parahydrogen addition to propylene, which results in symmetric propane molecule with substantially enhanced methyl and methylene NMR signals. Specifically, we have synthesized site-selectively isotopically labeled 3-D-propylene molecule to study polarization dynamics in the resulting mono-deuterated propane after pairwise parahydrogen addition. The deuterium presence in the hyperpolarized propane product results in a minute isotope chemical shift effect allowing to distinguish the proton resonances of CH3 and CH2D groups at 600 MHz. Pairwise parahydrogen 1,2-addition to 3-D-propylene was first confirmed by performing the reaction inside a 600 MHz NMR spectrometer, i.e., in the weakly-coupled regime at 14 T, where proton polarization dynamics is restricted to the molecular sites of parahydrogen addition. However, when the pairwise parahydrogen addition is performed in the strongly-coupled regime, i.e., at the Earth's magnetic field, efficient polarization transfer to CH2D protons is readily observed, leading to polarization redistribution between the three inequivalent sites. This finding is important as it sheds light on polarization dynamics in the strongly coupled symmetric spin systems such as propane studied here—the presented results are expected to be applicable to other spin systems such as butane.