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Author: Subject: Replacement of Pd/C by powdered catalytic converter for hydrogenation reactions.
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[*] posted on 17-6-2022 at 13:39
Replacement of Pd/C by powdered catalytic converter for hydrogenation reactions.


Hi guys !!
I've been working on the replacement of palladium on carbon by powdered catalytic converter.
Testing 3 reactions, Methylene blue reduction, nitrobenzene reduction to aniline and cinnamyl alcohol hydrogenation.

I uploaded a PDF with the experimental report, with images.
I appreciate corrections and recommendations :) hope you like my work :D

Attachment: Replacement of Palladium on Carbon by Powdered Catalytic Converter for Hydrogenation Reactions (1.1MB)
This file has been downloaded 417 times

[Edited on 18-6-2022 by Chem Science]
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[*] posted on 18-6-2022 at 05:55


good work!
Did you use used cat. converter or new one?
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[*] posted on 18-6-2022 at 06:54


Quote: Originally posted by Bonee  
good work!
Did you use used cat. converter or new one?


It was an Old, used catalyst. With low palladium content.
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[*] posted on 19-6-2022 at 09:29


Interesting.

How was the catalyst powder harvested from the converter?
Just crushing the chunks of honeycomb like catalyst material and then preparation as in your pdf?

Edit
Also, do you know if a new and maybe higher palladium converter would preform much better?

[Edited on 2022-6-19 by Mateo_swe]
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[*] posted on 19-6-2022 at 14:33


Quote: Originally posted by Mateo_swe  
Interesting.

How was the catalyst powder harvested from the converter?
Just crushing the chunks of honeycomb like catalyst material and then preparation as in your pdf?

Edit
Also, do you know if a new and maybe higher palladium converter would preform much better?

[Edited on 2022-6-19 by Mateo_swe]


Hi !!
Yes i got 3 samples of Half catalyst, weigh approx. 350g each. All of them arrived just cutted in half [The provider claims to have cutted the converter with a grinder, and the catalyst them self were extracted complete, and cut in half with the grinder to], and i crushed them manually and pulverized in a morter.
2 of them were processed for precios metal extraction, yielding about 150 mg each. (Low palladium content).

Despite the activation procedure being done to preserve palladium, the comparison of activated Vs inactivated suggest that diminishing palladium content is bad.
A newer, higher palladium containing catalyst, should work better.
Mine was really bad.
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[*] posted on 21-2-2023 at 07:29


Replacement of Palladium on carbon by powdered catalytic converter for hydrogenation reactions.

By:Chemistry Science
17/06/2022

INTRODUCTION

Catalytic hydrogenation is a useful and relatively common chemical reaction in organic synthesis, usually used to hydrogenate alkenes. The catalyst of excellence for these reactions is 5% palladium on carbon. These catalysts are usually not difficult to buy or make, and it’s reasonable accessible for the amateur, however in some cases palladium on carbon can be hard to obtain. Personally, in Argentina is not something easy to obtain. The goal of these post is to report on the efficacy on the replacement of palladium on carbon by powdered catalytic converters from cars for 3 reactions.

EXPERIMENTAL PART

Reagents

_Methylene Blue [Cicarelli]
_Nitrobenzene [Lab grade, distilled]
_Aniline [Synthesized]
_Hydrogen Peroxide 250v [Tech. Grade]
_Sodium Hydroxide 98% [Tech. Grade]
_Ethanol 96% [Pharmacological]
_Isopropanol [Todo Droga Lot: 2020081701] (density: 0.783 g/mL)
_Hydrochloric acid (10.0± 0.1) M [Tech. Grade, colorless]
_Beta-Naphthol [Sigma Lot: 80H3402]
_Sodium Nitrite [Pura Química lot: 89163824uo]
_Double-Distilled Water [Pura Química Lot:18-12]
_Methanol [Tech. Grade]
_Cinnamyl Alcohol [Lab. Grade]
_Petroleum Ether [Cicarelli Lot:73314] (Recycled)
_Elemental Bromine [Synthesized]

Apparatus and procedures

Photo colorimeter [Crudo Caamaño]
Attachment: Photocolorimeter (35kB)
This file has been downloaded 120 times


Methods

Catalyst Activation
Catalytic converters from cars are in charge of destruction of nitrogen oxides and left gasoline from the motor exhaust, so they become contaminated with gasoline, oil, and some iron. These contaminants can slow the catalyst action, and or contaminate the reaction, so a couple of washings were made to remove as much as these contaminants as possible.
To an arbitrary amount of powdered catalyst in an Erlenmeyer flask, methanol was added to completely cover the catalyst and have an excess of methanol, these was left to sit for 12hs.
After 12hs the catalyst was filtered, and washed with little portions of methanol. These operations were repeated for 6hs instead of 12, and the catalyst dried on a hotplate.

Methanol Washes [Fist on left, last on right]
Attachment: Methanol Washes (539kB)
This file has been downloaded 133 times

The methanol washed catalyst was covered with an excess of approx. 8M hydrochloric acid, and left to sit for 12hs, after which it was filtered and washed with Double-distilled water. [Filtered acid was yellow]
The damp catalysts was mixed with 500mL of double-distilled water and 10ml of 10M HCl, and was boiled until 200mL of volume were lost, after which it was filtered and washed with double-distilled water and ethanol.

Filtering after boiling with water
Attachment: Filtering after boling with water (531kB)
This file has been downloaded 154 times

The catalyst was heated in a beaker over a hotplate to 120ºC overnight.

Catalyst drying on hotplate.
Attachment: Activated catalyst (525kB)
This file has been downloaded 152 times

After these procedures the catalyst was saved and labeled as “Activated Catalyst”

Activated Catalyst [left] Vs Crude Catalyst [right]
Attachment: Activated catalyst Vs Crud (353kB)
This file has been downloaded 137 times

Hydrogen Generator
Hydrogen was generated by the reaction of aluminum with aqueous sodium hydroxide, is a 1L RBF connected to vacuum and a balloon, as shown in the following images.

Hydrogen generator apparatus
Attachment: Hydrogen Generator [V1] (561kB)
This file has been downloaded 163 times
Attachment: Hydrogen Generator [V1] (512kB)
This file has been downloaded 124 times

After NaOH is added to the RBF, vacuum is applied, and then the apparatus isolated and hydrogen is collected in the balloon until approx. 1L of hydrogen is collected.

Hydrogenation-Reduction reactions.

Methylene blue Reduction.

First, 2 solutions of Methylene blue (MB) were prepared.
Solution 1: Consisting of (11±2) mg of MB in (250,0±0,2) mL od double-distilled water.
Solution 2: Consisting of (25,00±0,06) mL of Solution 1 in (250,0±0,2) mL of double distilled water.
In a 250mL Schlenk RBF, (100±1) mL of Solution 2 were mixed with (2,5±0,2) g of inactivated catalyst, a stir bar and connected to the hydrogen balloon and vacuum.
A control reaction was made with (50±1) mL of solution 2 and (1,2±0.2) g of inactivated catalyst.


Apparatus for Methylene Blue reduction.
Attachment: Catalytic Hydrogenation (488kB)
This file has been downloaded 158 times

The RBF was connected to vacuum for 2 min, filled with hydrogen, pull vacuum again and finally left with hydrogen and stirring was started.
The reaction only took 10 minutes to go colorless. After these the absorbance was measured.

Reaction[left] and control [Right]
Attachment: Catalytic hydrogenation [Aprox. 10 min] Vs Control (652kB)
This file has been downloaded 140 times

Nitrobenzene to aniline

In a 250mL Schlenk RBF (50±1) mL of isopropanol were mixed with (1,5±0,4) mL of nitrobenzene and (4,0±0,2) g of inactivated catalyst along with a stir bar.
The RBF was connected to vacuum and a hydrogen balloon.
A control reaction consisting of (50±1) mL of isopropanol, (1,5±0,4) mL of nitrobenzene and (4,0±0,2) g of inactivated catalyst in a Erlenmeyer flask.

Reaction [left] and Control [Right]
Attachment: Hydrogenation of Nitrobenzene [Reaction Setup and Control] (590kB)
This file has been downloaded 151 times

The reaction flask was connected to vacuum for 2-3 min, filed with hydrogen, set to vacuum and finally let with hydrogen and stirring was started.
The reaction started 02/02 at 18:40hs., and stopped 06/06 at 10:30hs.


Both reaction and control were filtered and tested for the presence of Aniline.

Cinnamyl alcohol hydrogenation

Inactivated Catalyst:

In a 250mL Schlenk RBF, (5,0±0,2) g of cinnamyl alcohol were mixed with (2,5±0,2) g of inactivated catalyst, and 50 mL of ethanol as solvent.
The RBF was connected to vacuum and hydrogen as in previous examples.
The reaction flask was connected to vacuum for 2-3 min, filed with hydrogen, set to vacuum and finally let with hydrogen and stirring.
The reaction was started on 08/06 at 23:30hs and stopped on 09/06 at 21:20 hs
After which the mixture was filtered, and diluted with ethanol to a final volume of (100,0 ±0,2) mL.
These was analyzed by TLC and titrated with aqueous bromine.

Activated Catalyst:

In a 250mL Schlenk RBF, (2,5,0±0,2) g of cinnamyl alcohol were mixed with (2,5±0,2) g of inactivated catalyst, and 50 mL of ethanol as solvent.
The RBF was connected to vacuum and hydrogen as in previous examples.
The reaction flask was connected to vacuum for 2-3 min, filed with hydrogen, set to vacuum and finally let with hydrogen and stirring.
Total reaction time was 31hs 30min.
After which the mixture was filtered, and diluted with ethanol to a final volume of (100,0 ±0,2) mL.
These was analyzed by TLC and titrated with aqueous bromine.

Cinnamyl alcohol hydrogenation with activated catalyst.
Attachment: Reaction (472kB)
This file has been downloaded 146 times


RESULTS AND DISCUSSION

Methylene Blue Reduction
The idea of using methylene blue, was to test if the catalytic converter was useful as a Hydrogenation Catalyst, since methylene blue is a blue color in the oxidized form, and colorless in the leuco reduced form. The idea was inspired from the paper “Hydrogenation/Oxidation induced efficient reversible color switching between methylene blue and leuco-methylene blue.” [1].
On the example of these report, methylene blue was reduced to colorless in less than 10 minutes.

Reduced Methylene blue [left] and control [Right]
Attachment: Reaction and Control (with catalyst) (547kB)
This file has been downloaded 167 times

Addition of hydrogen peroxide to the reduced methylene blue gave back the blue color.
Given the low concentration of Palladium on the catalyst (From other work with these catalyst) , the reaction was expected to be slow, and hence the set of the photo colorimeter.
It was quite the surprise when the reaction went colorless in just less than 10 minutes. Non the less the absorbance was measured at λ=670nm, after filtering the reaction and control.
Reaction: Abs= 0,07

Control: Abs= 0,11
Solution 2: Abs=0,24
The set of a control reaction was made to discard effect’s like, contaminant’s, adsorption on the catalyst, and unexpected interferences. The difference in absorbance between the Control and Solution 2 seems to confirm these was a good thing to have.

Nitrobenzene
The reduction of nitrobenzene to aniline with the use of palladium catalyst is mentioned in “Palladium nano-catalysts encapsulated on porous

silica @ magnetic carbon-coated cobalt nanoparticles for sustainable
hydrogenations of nitroarenes, alkenes and alkynes” [2].
After the 87hs of reaction, hydrogen adsorption was not observed, and the reaction was stopped and filtered.
To test the presence of aniline a Azo-coupling reaction was done with beta-naphthol in the following manner.
Solution A: HCl [0,50±0.01]M
Solution B: Beta-naphthol: approx. 100mg.
Sodium Hydroxide: 2,1g
Double-Distilled water: 100mL (Final Volume)
Solution C: Sodium Nitrite: approx. 100mg
Double-distilled water: 100mL (Final Volume)
Test step’s:
1] 3 mL of solution A is mixed with 1 mL of solution C, and 1 or 2 drops of the substance under test on a test tube at 0ºC and left it for 2-3 min.
2] To the previous cold mixture, 2mL of solution B Is added


Aniline-beta naphthol azo dye reaction scheme. Doi: [10.1021/acssuschemeng.8b03486]
Attachment: Aniline Azo reaction Scheme and Spectra (156kB)
This file has been downloaded 127 times

Results:

If aniline is presence a vivid orange precipitate is observed.

Results of Aniline test.
Attachment: Aniline Rest (Day 1) (I) (383kB)
This file has been downloaded 124 times

Unfortunately, TLC plates were not available when these reactions was done. However, this reaction was not expected to work on the first place, and this analysis was enuf to not pursue this reaction anymore.
A consequence of the hardness of the catalyst and the long reaction time was the loss of the stir bar.

Worn stir bar.
Attachment: Stirr Bar After Reaction (511kB)
This file has been downloaded 125 times

Cinnamyl Alcohol

To check the progress of the cinnamyl alcohol hydrogenation TLC was performed.
The Solvent system was a mixture of petroleum ether and isopropanol. The fist 3 TLC runs were used to find the best eluent mixture.

TLC test to find the best eluent mixture.
Attachment: TLC plates (430kB)
This file has been downloaded 114 times

The eluent mixture of choice was Pet.Ether/IPR (90:10).
The TLC for both reactions are shown below.

TLC of Reactions.
A: Activated Catalyst.; C: Crude Catalyst.
Attachment: Final Result (500kB)
This file has been downloaded 128 times

The TLC shows a new product forming, but it’s not conclusive. The eluent seems to have some impurity, and the cinnamyl alcohol is not pure.
A crude Bromine titration was performed to compare results.

Bromine Titration:

A solution of (3,0±0,2) g of elemental bromine, with some Sodium Bromide was dissolved in (100,0±0,1) mL of double-distilled water (Bromine Water Solution)
A Reference solution was made by dissolving (262±2) mg of cinnamyl alcohol in (25,00±0,06) mL of ethanol. (Reference Solution)
Results:
(5,00±0,04) mL of reference solution reacts with (1,9±0,2) mL of Bromine water solution.
(2,00±0,02) mL of Crude catalyst reaction reacts with (2,7±0,2) mL of bromine water solution.
(2,00±0,02) mL of Activated catalyst reaction reacts with /1,2±0,2) mL of bromine water solution.

Reference solution [Left] Bromine Water [Right]
Attachment: Bromine and Cynamil alcohol standard (376kB)
This file has been downloaded 155 times

Using these results, it’s possible to extrapolate the cinnamyl alcohol content in the reactions, for the Crude catalyst reaction the content of cinnamyl alcohol is (3,7±0,4) g which represents a conversion of 1,3g of the 5g.
The Activated catalyst contains (1,6±0,5) g of cinnamyl alcohol, which represents a conversion of only 0,4g.
These results suggest that in these cases, catalyst activation was not beneficial, the palladium content was probably reduced and there fore the reaction speed reduced to.
The particular catalytic converters used were known to have small palladium content, and the activation procedure while it did get rid of

contaminants, it also reduced the palladium content on the particularly bad catalyst I had access to.
CONCLUSIONS:

The use of Powdered catalytic converter as a substituent of palladium on carbon seems to be possible in some cases, however the palladium content of the catalyst should be check.
Also, the wear on the glassware and stir bar should be taken to account.

BIBLIOGRAPHY

[1] “Hydrogenation/Oxidation induced efficient reversible color switching between methylene blue and leuco-methylene blue” [doi: 10.1039/c7ra04498d]

[2] “Palladium nanocatalysts encapsulated on porous silica @ magnetic carbon-coated cobalt nanoparticles for sustainable hydrogenations of nitroarenes, alkenes and alkynes” [doi: 10.1002/cctc.201901371]
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[*] posted on 21-2-2023 at 11:30


Thank you for sharing this detailed write-up! It is always nice to see experimental results documented thoroughly, even if the results are not as great as you may have hoped. We can't learn anything or build off of results not documented. I hope to see more work on this in the future!

One suggestion I have regarding the cinnamyl alcohol reaction: it would be nice to see a bromine titration done on crude catalyst in ethanol with no cinnamyl alcohol present. This would determine if the anomalous reactivity you observed is actually because some unsaturated hydrocarbon tar from the inactivated catalyst was oxidized by the bromine.




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[*] posted on 21-2-2023 at 14:58


Thank's Texium.
Ahh .. Your right, i did not include the catalyst :(. Damn .... That's embarrassing, Sorry for that.
If i ever do experiments again with these method, i'll make sure to inform these appropriately :)
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[*] posted on 21-2-2023 at 22:14


Excellent post, and great approach to a question we have all been wondering about and now that someone has done it we have an answer finally.

[Edited on 22-2-2023 by draculic acid69]
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[*] posted on 22-2-2023 at 08:23


Very nice write up Chem Science, we need more like these here. ;):);):)



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