Featured Research

from universities, journals, and other organizations

Unexpected behaviour of well-known catalysts

Date:
June 19, 2013
Source:
Institute of Physical Chemistry of the Polish Academy of Sciences
Summary:
Industrial palladium-copper catalysts change their structures before they get to work, already during the activation process. As a result, the reaction is catalysed by a catalyst that is different from the one originally prepared for it.

Dr. Magdalena Bonarowska from the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) in Warsaw puts a weighted amount of Pd-Cu/SiO2 catalyst into an experimental setup for studying catalytic hydrogen-assisted dechlorination of tetrachloromethane.
Credit: IPC PAS / Grzegorz Krzyżewski

Industrial palladium-copper catalysts change their structures before they get to work, already during the activation process. As a result, the reaction is catalysed by a catalyst that is different from the one originally prepared for it. This surprising discovery was made by researchers from the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw.

Related Articles


Removing of nitrates from ground water or chlorine from dry cleaning wastes are important environmental protection operations that require the use of appropriate catalysts. Popular catalysts include well-known silica-supported palladium-copper catalysts. A team of researchers led by Prof. Zbigniew Karpiński from the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) in Warsaw has shown that these catalysts behave differently than assumed to date.

Catalyst is a chemical that speeds up a chemical reaction by participating in it and is regenerated after the reaction is completed. Apart from profiting from shorter reaction time, the use of a catalyst may result in increased reaction selectivity, i.e., a higher yield of the target product as compared with the by-products.

Selective catalysts are usually systems composed of more than one metal. Palladium catalysts are often modified with copper. Active catalyst nanoparticles are deposited on a silica (SiO2) support. Before reaction, so prepared palladium-copper (Pd-Cu) catalyst is heated at high temperature in the presence of hydrogen. The purpose of the operation is to activate the catalyst, which means to provide the catalyst's atoms with energy allowing them for participation in the final reaction.

The ratio of amounts of both metals used in the catalyst has a substantial effect on the operational efficiency of a bimetallic catalyst. "With x-ray measurements we discovered something the researchers were not aware of to date," says Dr Magdalena Bonarowska (IPC PAS). Analytical results indicated that during the activation process in the hydrogen atmosphere at temperatures above 400 °C palladium interacts with silica in the support -- and so escapes from active catalyst's nanoparticles. "A catalyst originally composed of, say, 75% palladium and 25% copper can have the ratio of metals strongly disturbed, for instance 50% to 50%. Moreover, its crystal structure changes. This means that the reaction will be catalysed by a catalyst that is different from the one originally prepared!," states Dr Bonarowska.

Palladium losses from the active catalyst's nanoparticles lead to faster catalyst deactivation. Practically, it translates into additional, substantial costs related to unloading of a chemical reactor and regeneration or even replacement of the catalyst inside the reactor.

"It's not uncommon that silica-supported palladium-copper catalysts must be activated at temperatures as high as 500 °C. The operation aims at possibly ideal mixing of both metals dispersed on the surface of the support. It is, however, worth to consider if -- provided the target reaction allows for that -- the activation of the catalyst at lower temperatures, but for instance for a longer time, wouldn't be a better solution," notices Prof. Karpiński.

Palladium-copper catalysts on various supports, including silica, are used for removal of nitrates from ground water, and for selective reduction of numerous organic chemicals, including the reduction of nitro compounds to amines, and unsaturated hydrocarbons (e.g., acetylene to ethylene or butadiene to butene). They are also used for electrocatalytic oxidation of methanol and hydrogen-assisted dechlorination, i.e., chlorine removal from harmful organic chemicals with hydrogen.


Story Source:

The above story is based on materials provided by Institute of Physical Chemistry of the Polish Academy of Sciences. Note: Materials may be edited for content and length.


Journal Reference:

  1. M. Bonarowska, W. Juszczyk, Z. Karpiński. Phase transformations in silica-supported Pd–Cu catalysts during reduction in hydrogen. Journal of Catalysis, 2013; 301: 112 DOI: 10.1016/j.jcat.2013.02.008

Cite This Page:

Institute of Physical Chemistry of the Polish Academy of Sciences. "Unexpected behaviour of well-known catalysts." ScienceDaily. ScienceDaily, 19 June 2013. <www.sciencedaily.com/releases/2013/06/130619101523.htm>.
Institute of Physical Chemistry of the Polish Academy of Sciences. (2013, June 19). Unexpected behaviour of well-known catalysts. ScienceDaily. Retrieved October 31, 2014 from www.sciencedaily.com/releases/2013/06/130619101523.htm
Institute of Physical Chemistry of the Polish Academy of Sciences. "Unexpected behaviour of well-known catalysts." ScienceDaily. www.sciencedaily.com/releases/2013/06/130619101523.htm (accessed October 31, 2014).

Share This



More Matter & Energy News

Friday, October 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Jaguar Land Rover Opens $800 Million Factory in Britain

Jaguar Land Rover Opens $800 Million Factory in Britain

AFP (Oct. 30, 2014) — British luxury car manufacturer Jaguar Land Rover opened a $800 million engine manufacturing centre in western England, creating 1,400 jobs. Duration: 00:45 Video provided by AFP
Powered by NewsLook.com
SkyCruiser Concept Claims to Solve Problem With Flying Cars

SkyCruiser Concept Claims to Solve Problem With Flying Cars

Buzz60 (Oct. 30, 2014) — A start-up company called Krossblade says its SkyCruiser concept flying car solves the problem with most flying car concepts. Mara Montalbano (@maramontalbano) explains. Video provided by Buzz60
Powered by NewsLook.com
Mind-Controlled Prosthetic Arm Restores Amputee Dexterity

Mind-Controlled Prosthetic Arm Restores Amputee Dexterity

Reuters - Innovations Video Online (Oct. 29, 2014) — A Swedish amputee who became the first person to ever receive a brain controlled prosthetic arm is able to manipulate and handle delicate objects with an unprecedented level of dexterity. The device is connected directly to his bone, nerves and muscles, giving him the ability to control it with his thoughts. Matthew Stock reports. Video provided by Reuters
Powered by NewsLook.com
Robots Get Funky on the Dance Floor

Robots Get Funky on the Dance Floor

AP (Oct. 29, 2014) — Dancing, spinning and fighting robots are showing off their agility at "Robocomp" in Krakow. (Oct. 29) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins