Technical articles
Experimental Selection and Outcome Assessment of Heterogeneous Metal Catalysts in Organic Synthesis
Experimental Selection and Outcome Assessment of Heterogeneous Metal Catalysts in Organic Synthesis
1. Basic Meaning of Supported Inorganic Heterogeneous Catalysts
The supported heterogeneous metal catalysts discussed in this article mainly refer to catalytic systems formed by dispersing palladium, platinum, ruthenium, rhodium, and other metals or metal-related active species on solid supports. Common supports include activated carbon, silica, alumina, calcium carbonate, and barium sulfate. During the reaction, the catalyst is usually a solid, while the substrates and products are mostly in the liquid or gas phase. The reaction mainly occurs at accessible active sites on the solid surface.
The core of this type of catalyst is a surface reaction system jointly formed by the metal, support, loading state, and reaction conditions. Even for supported palladium catalysts, differences in metal loading, support type, particle dispersion, water content, and surface treatment can lead to significantly different experimental results. Supported palladium, platinum, ruthenium, and rhodium catalysts are common heterogeneous catalysts in organic synthesis. They are often used for hydrogenation, hydrogenolysis, nitro reduction, reductive amination, selective reduction, and some carbon–carbon coupling reactions. Anhydrous platinum oxide and Raney nickel are not strictly supported precious-metal catalysts, but they are often used as reference systems in screening heterogeneous hydrogenation and hydrogenolysis conditions.
Component | Main Role | What Needs to Be Assessed During Selection |
Active metal | Responsible for adsorption, activation, and transformation of the substrate | Which type of metal is suitable as the starting direction for screening |
Solid support | Disperses the metal and affects the surface environment | Whether the support affects selectivity, reaction rate, and stopping-point control |
Loading state | Reflected in metal content, particle size, dispersion, and surface state | Whether different products containing the same metal may show different reaction behavior |
Reaction interface | Determines the contact efficiency between the substrate and the catalyst surface | Whether stirring, mass transfer, solvent, and wetting state are appropriate |
2. What Organic Synthesis Tasks Are Suitable for Supported Inorganic Heterogeneous Catalysts?
The common applications of supported inorganic heterogeneous catalysts are mainly concentrated in reduction and hydrogenolysis reactions. Their value lies in the wide availability of commercial products, suitability for small-scale initial screening, and the fact that the solid catalyst can usually be separated by filtration or centrifugation after the reaction. Many systems also provide a basis for further scale-up and process evaluation.
Reaction Task | Target Transformation | Common Assessment Focus |
Hydrogenation of alkenes and alkynes | Reduce unsaturated bonds to saturated bonds, or stop alkyne reduction at the alkene stage | Whether over-reduction occurs and whether the endpoint can be controlled |
Nitro reduction | Convert nitro compounds into amines or hydroxylamine intermediates | Whether dehalogenation occurs and whether azo by-products are formed |
Carbonyl hydrogenation | Convert aldehydes and ketones into alcohols or further reduced products | Whether double bonds, aromatic rings, or other reducible sites are affected |
Reductive amination | Form the target amine from a carbonyl compound and an amine | Whether alcohol by-products or over-alkylated products are generated |
Hydrogenolytic deprotection | Remove benzyl, benzyloxycarbonyl, and related protecting groups | Whether only the protecting group is removed, and whether other sensitive groups are also affected |
Selective reduction of acyl chlorides | Reduce acyl chlorides to aldehydes | Whether the aldehyde is further reduced to the alcohol |
Carbon–carbon coupling | Use supported palladium to catalyze Heck reactions, Suzuki couplings, etc. | Activity, palladium leaching, and recycling stability |
3. Selection Sequence: Define the Reaction Task First, Then Determine the Metal and Support
The selection of supported inorganic heterogeneous catalysts should proceed step by step according to the experimental problem.
Sequence | Question to Answer First | What It Determines |
1 | What type of transformation is the current reaction? | Determines whether the direction is hydrogenation, hydrogenolysis, nitro reduction, reductive amination, or coupling |
2 | Which functional groups in the substrate need to be preserved? | Assesses the risk of over-reduction, dehalogenation, deprotection, or side reactions |
3 | Which type of metal is suitable as the starting point? | Determines whether palladium, platinum, ruthenium, rhodium, nickel, or another metal should be screened |
4 | Should the support be treated as a variable? | Determines whether activated carbon, calcium carbonate, alumina, silica, and other supports should be compared |
5 | How should the conditions be matched with the catalyst? | Sets the solvent, temperature, hydrogen pressure, catalyst loading, reaction time, and stirring conditions |
6 | Do the results support further optimization? | Determines the next direction based on conversion, selectivity, by-products, filtration, and residual metal |
4. Determine the Catalyst Screening Direction According to the Reaction Task
4.1 Hydrogenation of Alkenes and Alkynes
For alkene and alkyne hydrogenation, two objectives should first be distinguished: complete hydrogenation and selective semi-hydrogenation.
For complete hydrogenation, supported catalysts such as palladium on activated carbon, platinum on activated carbon, ruthenium on activated carbon, and rhodium on activated carbon can usually be considered first. When the substrate contains aromatic rings, carbonyl groups, halogens, nitro groups, or benzylic structures, it is also necessary to check whether these sites are reduced or undergo hydrogenolysis. When selectively reducing alkynes to alkenes, the key is to stop the reaction at the alkene stage. Lindlar catalyst is a typical semi-hydrogenation catalyst. It is usually a palladium/calcium carbonate system deactivated by lead and other components. It is commonly used to selectively semi-hydrogenate alkynes to cis-alkenes and reduce the risk of further hydrogenation to alkanes.
Reaction Objective | Catalysts to Consider First | Key Observations During Initial Screening |
Complete hydrogenation of alkenes | Palladium on activated carbon, platinum on activated carbon, ruthenium on activated carbon | Whether other reducible groups are also affected |
Complete hydrogenation of alkynes | Palladium on activated carbon, platinum on activated carbon | Whether reduction to the alkane proceeds smoothly |
Semi-hydrogenation of alkynes | Lindlar catalyst, palladium/calcium carbonate systems | Whether the alkene continues to convert into the alkane after formation |
Hydrogenation of multifunctional substrates | Milder or deactivated systems | The reaction sequence of the target site and other functional sites |
For semi-hydrogenation reactions, the final yield alone is not sufficient. It is necessary to record when the target alkene begins to appear, when further hydrogenation by-products begin to appear, and the time range during which the target alkene can remain at a relatively high proportion.
4.2 Nitro Reduction
The usual goal of nitro reduction is to convert the nitro group into an amine. In a small number of studies, the transient accumulation or controlled formation of hydroxylamine intermediates may also be of interest. However, hydroxylamines usually continue to be reduced to amines, so denser sampling and milder conditions are required. The more complex the substrate, the more important selectivity becomes. Common starting directions include palladium on activated carbon, platinum on activated carbon, palladium on calcium carbonate, palladium on alumina, and Raney nickel. Carbon-supported palladium hydroxide is also often used in screening related to hydrogenation and hydrogenolysis. Raney nickel is a nickel-based heterogeneous hydrogenation catalyst. It is not a typical supported precious-metal catalyst, but it is often used as a screening reference in nitro reduction and routine hydrogenation.
Substrate Feature | Main Risk | Key Records Needed |
Halogenated nitroarenes | Dehalogenation | Whether the halogen is retained and whether the amine product is clean |
Polynitro substrates | Partial reduction or over-reduction | The transformation sequence of each nitro group |
Substrates containing alkenes or alkynes | Hydrogenation of the unsaturated bond | The sequence of nitro reduction and unsaturated-bond hydrogenation |
Hydroxylamine intermediate as the target | Further reduction to the amine | When the hydroxylamine reaches its peak and how quickly it disappears |
Substrates containing strongly coordinating sulfur or nitrogen groups | Decreased catalyst activity | Whether the reaction shows obvious slowdown or stalling |
4.3 Carbonyl Hydrogenation
Carbonyl hydrogenation mainly involves the conversion of aldehydes and ketones into alcohols, and it also includes cases of further deoxygenative reduction. Common screening directions include palladium on activated carbon, platinum on activated carbon, ruthenium on activated carbon, rhodium on activated carbon, and Adams catalyst. Adams catalyst is a platinum oxide catalyst. Although it is not a supported catalyst, it is often used as a platinum-based heterogeneous catalytic reference in hydrogenation and hydrogenolysis screening. Palladium on carbon can be used as a comparative direction in carbonyl hydrogenation screening, but for substrates containing benzyl groups, halogens, unsaturated bonds, or nitro groups, special attention should be paid to hydrogenolysis, dehalogenation, and competitive reduction.
Reaction Objective | Catalysts to Consider First | Key Observations |
Reduction of aldehydes and ketones to alcohols | Platinum on activated carbon, ruthenium on activated carbon, palladium on activated carbon, or nickel-based catalysts | Whether double bonds, aromatic rings, halogens, nitro groups, or benzyl structures are affected |
Reduction of aromatic carbonyl compounds | Palladium on activated carbon, platinum on activated carbon | Whether further deoxygenation or aromatic-ring hydrogenation occurs |
Difficult-to-reduce carbonyl substrates | Ruthenium- or platinum-based directions | Whether higher temperature, higher pressure, or a different solvent is needed |
In carbonyl hydrogenation, substrate solubility and surface adsorption directly affect the conversion rate. If conversion is slow, it is not advisable to simply increase the catalyst amount. The solvent, stirring, and substrate adsorption state on the metal surface should also be checked.
4.4 Reductive Amination
Reductive amination is not a single-step hydrogenation. The reaction usually first forms an imine or related intermediate from an aldehyde or ketone and ammonia, a primary amine, or a secondary amine, followed by hydrogenation to give the amine. When molecular hydrogen is used for reductive amination, the selectivity for the target amine, direct reduction of the carbonyl compound to the alcohol, over-alkylation, and intermediate equilibrium are all key issues.
Question to Assess | Experimental Records |
Whether the imine forms smoothly | Proportions of the substrate, imine intermediate, and unreacted amine |
Whether the carbonyl compound is directly reduced | Content of the alcohol by-product |
Whether over-alkylation occurs | Ratio of the target amine to secondary and tertiary amine by-products |
Whether the catalyst is inhibited by the amine | Whether the reaction becomes noticeably slower or stalls |
Whether the hydrogenation step is matched | Whether the hydrogenation rate is coordinated with the rate of intermediate formation |
Catalyst directions that can be screened include palladium on activated carbon, platinum on activated carbon, rhodium on activated carbon, ruthenium on activated carbon, and Raney nickel. When the substrate contains sulfur, strongly coordinating nitrogen heterocycles, or polyamine structures, small-scale screening should be performed first to observe whether catalyst activity is inhibited.
4.5 Hydrogenolytic Deprotection
Hydrogenolytic deprotection is commonly used to remove benzyl, benzyloxycarbonyl, and related protecting groups. Palladium on activated carbon is a common starting direction, and carbon-supported palladium hydroxide is also often used in screening hydrogenolysis and deprotection of benzyl-type structures.
Target Task | Catalysts to Consider First | Main Risk |
Debenzylation | Palladium on activated carbon, carbon-supported palladium hydroxide | Double bonds, nitro groups, or halogens may be reduced at the same time |
Removal of benzyloxycarbonyl protecting groups | Palladium on activated carbon, carbon-supported palladium hydroxide | Other benzylic or unsaturated sites in the substrate may also be affected |
Deprotection of multifunctional substrates | Milder palladium-based systems | The target deprotection and side reactions may be difficult to separate |
The key judgment in hydrogenolytic deprotection is not whether the protecting group can be removed, but whether only the target protecting group can be removed. For complex substrates, the deprotection rate, changes in other sensitive sites, and reaction endpoint should all be recorded.
4.6 Selective Reduction of Acyl Chlorides
When selectively reducing acyl chlorides to aldehydes, a common representative system is a palladium/barium sulfate Rosenmund catalyst. The main difficulty of this type of reaction is preventing the aldehyde from being further reduced to the alcohol. Palladium/barium sulfate systems help control the reduction depth by lowering the surface activity of palladium and are commonly used in screening related to Rosenmund reduction of acyl chlorides to aldehydes. For highly active or sensitive substrates, the use of inhibitors, temperature, solvent, and hydrogen introduction method still need to be further controlled to prevent the aldehyde from being further reduced to the alcohol.
Reaction Objective | Catalysts to Consider First | Key Observations During Initial Screening |
Reduction of acyl chlorides to aldehydes | Palladium/barium sulfate systems | Whether the aldehyde continues to convert into the alcohol |
Selective reduction of sensitive substrates | Deactivated palladium systems | Whether dehalogenation, hydrogenolysis, or over-reduction occurs |
For this type of reaction, the peak time of the aldehyde product should be recorded carefully. If the aldehyde rapidly continues to transform, the reduction depth of the current system is difficult to control.
4.7 Carbon–Carbon Coupling
Supported palladium catalysts can be used for carbon–carbon bond-forming reactions such as Heck reactions and Suzuki couplings. Unlike hydrogenation reactions, supported palladium coupling reactions require particular attention to palladium leaching. Studies have shown that temperature, solvent, base, substrate, and additives can all affect palladium leaching in supported palladium systems. Palladium species in solution may participate in catalysis, and after the reaction they may redeposit onto the support.
Check Item | Assessment Purpose |
Whether the filtrate continues to react after filtration | To determine whether active palladium species are present in solution |
Whether palladium residue in the product is acceptable | To assess the difficulty of workup and purification |
Whether the activity changes after catalyst recovery | To assess surface-state changes and metal loss |
Whether the results are consistent across multiple batches | To assess catalyst stability and process reproducibility |
5. How the Metal, Support, and Loading State Affect the Results
The performance of supported inorganic heterogeneous catalysts is jointly determined by the metal, support, and loading state.
Variable | What It Affects | Experimental Manifestation |
Metal type | Determines the main activity direction | Palladium is often used for hydrogenation and hydrogenolysis; platinum is often used for hydrogenation and some selective reductions; ruthenium and rhodium can be used for specific hydrogenation tasks |
Metal loading | Affects the number of accessible active sites | Changes in loading can alter reaction rate and side reactions |
Metal particle size | Affects surface adsorption and reaction pathways | Small particles, nanoclusters, or single-atom sites may show different behavior |
Support type | Affects dispersion, adsorption, and surface environment | Activated carbon, calcium carbonate, alumina, and silica may lead to different selectivities |
Catalyst water content | Affects safety, dispersion, and weighing | Dry products and wet products should not be substituted on an equal-mass basis without adjustment |
Surface poisoning or inhibition | Reduces certain overly strong activity | Can be used to control semi-hydrogenation or selective reduction |
Supports can change metal dispersion, pore structure, substrate accessibility, and metal stability. Metal size, morphology, composition, metal–support interactions, and interactions between the metal and the reactants or solvent can all affect catalytic properties.
6. Condition Variables and Key Experimental Records
After the catalyst is selected, the reaction conditions determine whether the results are stable. In supported heterogeneous systems, solvent, temperature, hydrogen pressure, stirring intensity, catalyst amount, and reaction time all affect the contact state between the substrate and the catalyst surface.
Condition Variable | What It Affects | Key Records |
Solvent | Affects substrate solubility, catalyst wetting, and surface adsorption | Solvent type, water content, and whether acid/base additives are present |
Temperature | Affects reaction rate and side reactions | Changes in target product and by-products over time |
Hydrogen pressure | Affects hydrogenation strength | Whether it accelerates over-reduction or hydrogenolysis |
Catalyst amount | Affects reaction rate and the time range during which the target product can be maintained | Whether dosing is calculated on a dry basis or as the wet product |
Stirring intensity | Affects solid–liquid or gas–liquid–solid mass transfer | Whether obvious differences appear after scale-up |
Reaction time | Affects stopping-point control | Peak time of the target product and time when by-products appear |
Substrate concentration | Affects adsorption, mass transfer, and side reactions | Whether selectivity decreases at high concentration |
Experimental records should include three types of information:
1. Substrate conversion rate;
2. Time of formation and disappearance of the target product;
3. Sources of the main by-products.
Screening of supported catalysts should record conversion, selectivity, endpoint, filtration behavior, and catalyst recovery performance at the same time.
7. How to Judge Whether the Selected Direction Is Correct from Experimental Results
After the initial screening, the experimental observations should be used to judge whether the current direction is worth further optimization.
Observation | Priority Assessment | Treatment Direction |
Slow conversion | The metal direction may be mismatched, substrate adsorption may be unfavorable, or mass transfer may be insufficient | Compare different metals and supports, then adjust temperature, pressure, and stirring |
Fast conversion but many by-products | The system is too active or lacks selectivity | Lower the reaction intensity, or switch to a milder or inhibited system |
Semi-hydrogenation always leads to over-reduction | In semi-hydrogenation, the target alkene remains available for only a short time and readily continues to convert into the alkane | Change the support or use an inhibited catalyst, and increase sampling frequency |
Nitro reduction is accompanied by dehalogenation | The current system is not mild enough toward the carbon–halogen bond | Change the catalyst direction and reduce the hydrogenation intensity |
Hydrogenolytic deprotection affects other sites | The system lacks sufficient selectivity | Change the catalyst or shorten the reaction time |
The filtrate continues to react after filtration | Metal leaching may be present | Perform hot filtration, blank controls, and residual metal analysis |
Recovered catalyst shows decreased activity | The catalyst surface state may have changed, or metal loss may have occurred | Do not directly treat it as a readily recyclable system |
In selective hydrogenation research, nitrogen- and sulfur-containing organic compounds are often used to regulate selectivity through adsorption on and modification of the metal surface. In real substrates, these functional groups may also inhibit or alter catalyst activity.
8. When Should the Catalytic Route Be Changed?
Supported inorganic heterogeneous catalysts are suitable for many reduction and hydrogenolysis tasks, but they are not suitable for every synthetic problem. When the following situations occur, a different catalytic route should be considered.
Situation | Reason for Assessment |
A high level of enantioselective control is required | Chiral ligands, chiral metal complexes, or other specially designed catalytic systems are usually needed |
The substrate contains multiple sensitive sites that are easily reduced | Heterogeneous hydrogenation may have difficulty acting on only one site |
Metal residue requirements are very strict | Solid catalysts may still undergo metal leaching |
The same source of side reactions persists after multiple rounds of screening | The problem may come from the catalytic direction itself, not merely from condition adjustment |
Results drift significantly after scale-up | Mass transfer, stirring, filtration, and catalyst state may be difficult to control reproducibly |
An existing route is more stable in selectivity and scale-up | There is no need to replace a mature route simply for the sake of using a heterogeneous catalyst |
9. Product Navigation Table for Supported Inorganic Heterogeneous Catalysts in Organic Synthesis: Selecting Tables 1–4 by Experimental Task
Research or Experimental Objective | Recommended Table to Consult First | Why Consult This Table First | Recommended Related Table | Navigation Notes |
Understand support effects and surface-regulation factors in supported metal catalysts | Table 1 | Table 1 lists support materials such as activated carbon, silica, alumina, and calcium carbonate, as well as sulfur-containing components that may affect metal surface reactivity. This helps readers understand how supports and surface regulation influence catalytic results | Tables 2 and 3 | Suitable for building a basic understanding of the “metal–support–reaction condition” relationship before moving into palladium-based or platinum, ruthenium, and rhodium systems according to the reaction task |
Compare the influence of different supports on metal-catalyzed results | Table 1 | Table 1 provides carbon supports, oxide supports, and carbonate supports, which can help readers understand how support type, pore structure, and surface properties affect metal dispersion and reaction selectivity | Tables 2 and 3 | Suitable for explaining why reaction rate, stopping point, and side reactions may change when the same supported metal catalyst is switched among activated carbon, alumina, calcium carbonate, or barium sulfate |
Screen alkene hydrogenation, alkyne hydrogenation, and alkyne semi-hydrogenation | Table 2 | Table 2 includes palladium on carbon, palladium on calcium carbonate, palladium on barium sulfate, and lead-poisoned palladium on calcium carbonate, making it suitable for screening hydrogenation strength and semi-hydrogenation stopping-point control | Tables 1 and 3 | If the target is complete hydrogenation, Table 3 can be consulted to compare platinum, ruthenium, and rhodium systems. If the target is to stop an alkyne at the alkene stage, the carbonate-, sulfate-, and poisoned palladium systems in Table 2 should be compared carefully |
Screen hydrogenolytic removal conditions for benzyl, benzyloxycarbonyl, and related protecting groups | Table 2 | Table 2 includes palladium on carbon and carbon-supported palladium hydroxide, which are suitable for exploring benzyl-type deprotection, hydrogenolysis, and deprotection conditions for complex substrates | Table 3 | If the palladium system reacts too quickly, affects other reducible sites, or needs to be compared with platinum, ruthenium, and rhodium systems, Table 3 can be used for comparative screening |
Study nitro reduction and selective reduction of halogenated nitro substrates | Table 2 | Palladium on carbon, palladium on alumina, palladium on calcium carbonate, and palladium on barium sulfate in Table 2 can be used for nitro reduction screening, and are suitable for observing dehalogenation, hydroxylamine intermediate accumulation, and azo by-products | Tables 3 and 4 | If dehalogenation or side reactions occur in palladium systems, Table 3 can be used to compare platinum, ruthenium, and rhodium systems. If cost, activity, and process feasibility need to be compared, Table 4 can be used to evaluate Raney nickel systems |
Explore carbonyl hydrogenation, aromatic-system hydrogenation, or reductive amination | Table 3 | Table 3 focuses on platinum, ruthenium, and rhodium catalysts and their carbon or alumina-supported forms, making it suitable for screening hydrogenation reactions related to carbonyl groups, aromatic systems, and reductive amination | Tables 2 and 4 | If comparison with the hydrogenolysis tendency of palladium systems is needed, Table 2 can be consulted. If a nickel-based heterogeneous hydrogenation reference is needed, Table 4 can be used |
Compare activity and selectivity differences among precious-metal catalysts | Table 3 | Table 3 covers platinum on carbon, sulfided platinum on carbon, ruthenium on carbon, ruthenium on alumina, rhodium on carbon, and rhodium on alumina, allowing comparison of how different precious metals and support combinations affect reaction outcomes | Table 2 | Suitable for judging whether reaction failure comes from an unsuitable metal direction, and for establishing parallel screening against the palladium systems in Table 2 |
Evaluate the influence of sulfiding or sulfur-containing components on catalyst selectivity | Tables 1 and 3 | The sulfur-containing diol in Table 1 can serve as a metal surface-regulation component, while sulfided platinum on carbon in Table 3 can be used to examine changes in catalyst activity and selectivity after sulfiding treatment | Table 2 | Suitable for studying semi-hydrogenation, over-reduction control, and regulation of metal surface reactivity, and can also be compared conceptually with the poisoned palladium systems in Table 2 |
Carry out palladium-catalyzed coupling or evaluate recovery and leaching in supported palladium systems | Table 2 | Palladium on alumina and palladium on carbon in Table 2 can be used for screening supported palladium catalytic systems, and are also suitable for observing whether the filtrate continues to react after filtration, palladium residue, and catalyst recovery stability | Table 1 | If the influence of the support on palladium loading state, filtration behavior, and leaching risk needs to be analyzed, the support materials in Table 1 can be used for comparative design |
Compare experimental differences between precious-metal catalysts and nickel-based heterogeneous catalysts | Table 4 | Table 4 lists Raney nickel catalyst, which is suitable as a nickel-based reference for nitro reduction, alkene hydrogenation, and some reduction reactions | Tables 2 and 3 | Suitable as a comparative direction when precious-metal catalysts are unsatisfactory in cost, residue, or selectivity, helping judge whether the metal system should be changed |
Design a small-scale condition-screening plan | Tables 2 and 3 | Table 2 is suitable for palladium-based hydrogenation, hydrogenolysis, semi-hydrogenation, and selective reduction screening. Table 3 is suitable for platinum, ruthenium, and rhodium-based hydrogenation and reductive amination screening | Tables 1 and 4 | Select Table 2 or Table 3 first according to the target reaction, then use Table 1 to understand support differences and Table 4 to establish a nickel-based reference |
Determine where to troubleshoot after reaction failure | Tables 1–4 | Slow conversion, many by-products, over-reduction, dehalogenation, continued reaction after filtration, and decreased activity after recovery often correspond respectively to issues with the metal, support, surface state, mass transfer, or leaching | Link to the corresponding table according to the problem | For support-related issues, consult Table 1 first; for palladium selectivity issues, consult Table 2; for replacement with platinum, ruthenium, or rhodium directions, consult Table 3; for a nickel-based reference, consult Table 4 |
Table 1 | Supports, Support Materials, and Components for Regulating Catalyst Selectivity
Category | CAS No. | Aladdin Catalog No. | Name | Specification or Purity | Product Features and Applications |
Selective hydrogenation-regulating component | 5244-34-8 | 3,6-Dithia-1,8-octanediol | ≥97% | A sulfur-containing diol compound that can be used in studies on regulating metal surface reactivity; suitable for examining the influence of sulfur-coordinating components on hydrogenation selectivity and catalyst surface state | |
Silica support | 7631-86-9 | Silicon dioxide | ≥99.95% metals basis, Particle size: 2 μm | A high-purity inorganic oxide support that can be used for preparing supported metal catalysts, surface adsorption studies, and comparisons of support effects | |
Alumina support | 1344-28-1 | Aluminum oxide | ≥99.9% metals basis, crystal form Y phase 15 nm | A nanoscale alumina support that can be used to study metal dispersion, surface acidity/basicity, and the influence of oxide supports on catalytic activity | |
Activated carbon support | 7440-44-0 | Activated charcoal | AR, ≥200 mesh, in bags | A porous carbon material that can serve as a support for palladium, platinum, ruthenium, rhodium, and other metals; also useful for adsorption, filtration, and catalyst support screening | |
Carbonate support | 471-34-1 | Calcium carbonate | Anhydrous, ACS, ≥99% | A carbonate-type inorganic support that can be used for preparing selective hydrogenation catalysts such as palladium on calcium carbonate and for comparing support effects |
Table 2 | Supported Palladium Catalysts: Screening for Hydrogenation, Semi-Hydrogenation, Hydrogenolysis, and Coupling
Category | CAS No. | Aladdin Catalog No. | Name | Specification or Purity | Product Features and Applications |
Palladium on alumina catalyst | 7440-05-3 | Palladium on alumina | 5 wt. % (dry basis), matrix activated alumina | An alumina-supported palladium catalyst that can be used for screening hydrogenation, hydrogenolysis, and palladium-catalyzed transformations; suitable for comparing the influence of oxide supports and carbon supports on reaction outcomes | |
Palladium on barium sulfate selective hydrogenation catalyst | 7440-05-3 | Palladium on barium sulfate | 5% Pd | A barium sulfate-supported palladium catalyst commonly used for selective reduction and mild hydrogenation condition screening; useful for examining the inhibitory effect of a low-activity support on over-reduction | |
Palladium hydroxide/carbon hydrogenolysis catalyst | 12135-22-7 | Palladium hydroxide on carbon | 20% Pd(OH)₂ | A carbon-supported palladium hydroxide catalyst commonly used for hydrogenolysis of benzyl-type protecting groups, aromatic ring hydrogenation, and reduction reaction screening; suitable for exploring deprotection conditions for complex substrates | |
Low-loading palladium on activated carbon catalyst | 7440-05-3 | Palladium on carbon | 1 wt % loading, activated synthetic carbon powder | A low-loading palladium on carbon catalyst that can be used for initial screening of mild hydrogenation, hydrogenolysis, and palladium-catalyzed reactions; suitable for examining the relationship between catalyst amount and reaction rate | |
Palladium on strontium carbonate catalyst | 7440-05-3 | Palladium on strontium carbonate | 2% Pd basis | A strontium carbonate-supported palladium catalyst that can be used for selective hydrogenation and support-effect studies; suitable for comparison with palladium on calcium carbonate and palladium on barium sulfate systems | |
Palladium on barium sulfate selective reduction catalyst | 7440-05-3 | Palladium on barium sulfate | ≥10% Pd | A barium sulfate-supported palladium catalyst that can be used for selective reduction and condition screening related to Rosenmund reduction; suitable for examining the influence of a low-activity support on reduction depth and over-reduction | |
General-purpose palladium on activated carbon hydrogenation catalyst | 7440-05-3 | Palladium on activated charcoal | 10% Pd, contains 40–60% H₂O | A commonly used wet palladium on carbon catalyst that can be used for alkene hydrogenation, nitro reduction, benzyl hydrogenolytic deprotection, and small-molecule synthesis condition screening | |
Lead-poisoned palladium on calcium carbonate semi-hydrogenation catalyst | 7440-05-3 | Palladium on calcium carbonate | Pd 5%, poisoned with lead | A lead-poisoned palladium on calcium carbonate catalyst suitable for selective semi-hydrogenation of alkynes; useful for controlling the stopping point at the alkene stage and reducing the risk of further hydrogenation |
Table 3 | Platinum, Ruthenium, Rhodium, and Related Heterogeneous Catalysts: Screening for Hydrogenation, Reduction, and Support Effects
Category | CAS No. | Aladdin Catalog No. | Name | Specification or Purity | Product Features and Applications |
Platinum oxide hydrogenation catalyst | 1314-15-4 | Platinum oxide | Pt ≥84.4% | A platinum oxide catalyst that can be used for screening hydrogenation, hydrogenolysis, and reduction reactions; suitable for comparing activity with supported platinum catalysts | |
Ruthenium on alumina catalyst | 7440-18-8 | Ruthenium on alumina | 5% loading, powder | An alumina-supported ruthenium catalyst that can be used in studies of carbonyl, aromatic-ring, and other hydrogenation reactions; suitable for evaluating the catalytic performance of the ruthenium metal/alumina support combination | |
Low-loading platinum on activated carbon catalyst | 7440-06-4 | Platinum on carbon (Evonik Noblyst® P8078) | 1% Pt, ~60% water | A low-loading wet platinum on carbon catalyst that can be used for screening mild hydrogenation and selective reduction conditions; suitable for assessing reaction activity at low platinum loading | |
Ruthenium on activated carbon catalyst | 7440-18-8 | Ruthenium on carbon | Ru 5%, about 50% water | A wet ruthenium on carbon catalyst that can be used in hydrogenation, reductive amination, and partial aromatic-system hydrogenation studies; suitable for comparison with palladium on carbon and platinum on carbon systems | |
General-purpose platinum on activated carbon hydrogenation catalyst | 7440-06-4 | Platinum on carbon | Pt 10%, water content ≤60% | A commonly used platinum on carbon catalyst that can be used for hydrogenation and reduction screening of alkenes, nitro groups, carbonyl groups, and related substrates; also useful for comparing platinum-based and palladium-based catalytic behavior | |
Sulfided platinum on carbon selective catalyst | 7440-06-4 | Platinum, sulfided, on carbon | extent of labeling: 5 wt. % loading, dry, matrix carbon, reduced support | A sulfided carbon-supported platinum catalyst that can be used in selective hydrogenation and metal surface-regulation studies; suitable for examining the influence of sulfiding treatment on side reactions and reduction depth | |
Rhodium on activated carbon catalyst | 7440-16-6 | Rhodium on carbon | Rh 5%, contains 55–60% water stabilizer | A wet rhodium on carbon catalyst that can be used for hydrogenation screening of alkenes, aromatic rings, and some carbonyl-related substrates; suitable for comparison with ruthenium on carbon and platinum on carbon catalysts | |
Rhodium on alumina catalyst | 7440-16-6 | Rhodium (on alumina) | 5 wt. % loading, matrix alumina support | An alumina-supported rhodium catalyst that can be used in hydrogenation and support-effect studies; suitable for comparing the catalytic performance of rhodium on carbon and rhodium on alumina |
Table 4 | Nickel-Based Heterogeneous Hydrogenation Catalyst
Category | CAS No. | Aladdin Catalog No. | Name | Specification or Purity | Product Features and Applications |
Nickel-based heterogeneous hydrogenation catalyst | 7440-02-0 | Raney Nickel | 20–40 mesh, low molybdenum, dispersed in water | A porous nickel-based hydrogenation catalyst that can be used for screening nitro reduction, alkene hydrogenation, and nitrile- and carbonyl-related reductions; suitable for comparison with supported precious-metal catalysts in terms of cost and activity |
Note: The above products are representative Aladdin products. More product specifications can be searched on the Aladdin website by “product name/CAS/catalog number.”
References
[1] Merck Sigma-Aldrich. Heterogeneous Catalysts for Synthetic Applications.
[2] Merck Sigma-Aldrich. Inorganic Catalysts.
[3] Nishimura S. Handbook of Heterogeneous Catalytic Hydrogenation for Organic Synthesis. New York: John Wiley & Sons, 2001.
[4] Liu L, Corma A. Metal Catalysts for Heterogeneous Catalysis: From Single Atoms to Nanoclusters and Nanoparticles. Chemical Reviews, 2018, 118(10): 4981–5079.
[5] Zhang L, Zhou M, Wang A, Zhang T. Selective Hydrogenation over Supported Metal Catalysts: From Nanoparticles to Single Atoms. Chemical Reviews, 2020, 120(2): 683–733.
[6] Murugesan K, Senthamarai T, Chandrashekhar V. G., Natte K, Kamer P. C. J., Beller M, Jagadeesh R. V. Catalytic Reductive Aminations Using Molecular Hydrogen for Synthesis of Different Kinds of Amines. Chemical Society Reviews, 2020, 49(17): 6273–6328.
[7] Biffis A, Centomo P, Del Zotto A, Zecca M. Pd Metal Catalysts for Cross-Couplings and Related Reactions in the 21st Century: A Critical Review. Chemical Reviews, 2018, 118(4): 2249–2295.
[8] Soomro S. S., Ansari F. L., Chatziapostolou K., Köhler K. Palladium Leaching Dependent on Reaction Parameters in Suzuki-Miyaura Coupling Reactions Catalyzed by Palladium Supported on Alumina under Mild Reaction Conditions. Journal of Catalysis, 2010, 273(2): 138–146.
For more related articles, see below: