BIL 01 • NOVEMBER 2015 • IIUM CHEMISTRY PUBLISHING
CATALYST TODAY
CATALYST TODA Y
Edition No 01 (November 2015) Published by IIUM Chemistry Publishing Catalyst Today is a science-based bulletin which focuses on industrial catalysis. It is produced by the first batch students of Bachelor of Science (Applied Chemistry) of International Islamic University Malaysia (IIUM).
The production was supervised by Dr Rosliza Salim who currently teaches the students for Industrial Catalysis subject (SCH3053) in semester 1, 2015/2016 session.
EDITORIAL BOARD
FOREWORD ENGINEERS OF ORGANISMS METAL SALT CATALYST PHOTOCATALYSIS COMIC: ENZYMES IN ACTION ZEOLITE POSTER MONSANTO PROCESS
HYDROFORMYLATION THE RED STIMULANT THE WACKER PROCESS
THE WRITERS PEARL OF WISDOM
FOREWORD Assalamualaikum w.b.t. I gratefully acknowledge my indebtness to my third year students from Department of Chemistry for their input in this project. These students from Applied Chemistry have worked a lot on the drafts, observations, and discussions to the topic of “homogeneous catalysis�, which eventually condensed in this bulletin. The material presented in this bulletin was selected based on the syllabus which includes eight topics of homogeneous catalytic reactions with proven industrial applications and well-established mechanism. Besides getting deeper understanding on industrial catalysis subject, this bulletin serves as the assignment which seeks cooperation and teamwork of each group member to accomplish the task given. I am very thankful and pleased with the commitment I received right from the start from the editorial board members which did their best in designing, correcting and improving the contents of this bulletin. More than anything else, I really hope that this bulletin would give a clear view on the homogeneous catalysis and be a source of knowledge for the students and also the readers. Thank You.
Asst. Prof. Dr. Rosliza Mohd Salim Advisor, Catalysis Today.
CATALYST T O D A Y
ENGINEERS Of organism By Izni, Atiqah, Khai, Anis Hamizah & Afiq Luqman
ENZYMES
are famously known as the “engineers� of an organism. Their roles and applications are highly varied and yet its mechanistic concepts are essentially similar.
The Chemical Equation of hydrolysis of lactose by lactase
CATALYST T O D A Y
METAL SALTS
CATALYST
CATALYST T O D A Y
AgTPA CH3CN
80째C
R 1 = aryl, cyclohexyl R 2 , R 3 = dialkyl, dibenzyl R 4 = alkyl, phenyl
Friedel-Crafts acylation (above) and alkylation (below)
CATALYST T O D A Y
PHOTOCATALYSI By Huda, Sakinah, Hafiza, Fazleen & Fatin Nadiah
Have you ever heard of photocatalysis? What is photocatalysis?
IS
CATALYST T O D A Y
,
Titanium dioxide is one of the chemicals added in paint and coating system.
It ensures the longevity of the paint. This catalyst also has excellent light-scattering properties which produce the light colored paints that can provides an impression of openness and spacy room.
Titanium dioxide is used in cosmetics industry.
Titanium dioxide has been well accepted in food industry as additive in various food products that mainly for whitening and texture.
It also applicable in oral pharmaceutical formulations
Titanium oxide included as protection of skin from harmful effects of solar ultraviolet radiation.
It is widely use on most surfaces and items that are white in color. This proved that titanium dioxide is harmless.
Nano-sized titanium dioxide is considered as a nonirritant and non-toxic excipient. This is supported by Pharmaceutical Excipients handbook.
• •
CATALYST T O D A Y
YAYY!!
CATALYST T O D A Y
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By Hannan
Stellerit
Stellerit
Edinband, Scotland
Rudny, Kazakhstan
Natrolite
Bombay, India
Stilbite
Aurangabad, India
A Zeolite acting an a molecular sieve and a catalyst during the formation of 1,4-dimethylbenzene from methylbenzene.
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Structure The basic chemical structure of Zeolite
n, Jazmi, Syafini, Nadia Aimi & Atif CATALYST T O D A Y
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CATALYST T O D A Y
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CATALYST T O D A Y
By Nur Hidayah, Nur Shafina, Farah Hani, Nafisah & Dayang Fatin Nadhirah
What is hydroformylation? It is a type of
is derived from addition of the C-H bond of
oxo process which involves the catalyzed
formaldehyde across the carbon-carbon
conversion of olefins into aldehydes
double bond of the olefin. So far, the most
through the addition of synthesis gases,
commonly used catalysts are cobalt
carbon monoxide (CO) and hydrogen (H2).
(HCo(CO)4)
Hydroformylation process is important in
modifications such as cobalt phosphine
industries since the end products are
modified catalyst (HCo(CO)3(PR3)3), rho-
commercially used mainly in the plastics
dium phosphine catalyst (HRh(CO)(PPh3)3)
and detergents manufacture.
and
and
rhodium
with
some
triphenylphosphinetrisulfonate
(TPPTS). Now let’s take a look on the first
Discovered in 1938 by Otto Roelen,
catalyst employed for hydroformylation
this process developed special significance
which is cobalt. This was based on Roelen's
to industries since it produces a highly
original research whereby cobalt, under
versatile chemical intermediates, alde-
H2/CO pressure of 200-300 bar and at 110-
hydes that can be further transformed into
180°C, produced HCo(CO)4 as an active
many other functional groups. It is called
homogenous catalyst. The frequently use
as hydroformylation because the product
starting material for HCo(CO)4 catalyzed CATALYST T O D A Y
Bimetallic pathway; general mechanism of hydroformylation
hydroformylation, Co2(CO)8 reacts with hydrogen gas under catalysis reaction conditions to form two equivalents HCo(CO)4. However, HCo(CO)4 is only stable under certain minimum CO partial pressures at a given temperature. When CO pressure increases, the reaction rate decreases and give a high ratio of linear to branched product. On the contrary, when CO pressure decrease, the reaction rate will increase, hence, more branched alkyl through reverse ß-elimination will be yielded. Therefore, scientists had discovered COBALT CATALYST, HCo(Co)4
another transition metal that is suitable to yield more aldehyde and gives high regioselectivity of the expected product, which is rhodium. In 2004, about 75% of all hydroformylation processes are based on rhodium triarylphosphine catalysts, which excel with C8 or lower alkenes. The initial catalyst system was derived from Wilkinson's catalyst, RhCl(PPh3)3, but it was rapidly discovered that halides were inhibitors for hydroformylation. Hence, HRh(CO)(PPh3)3 and Rh(acac)(CO)2 are two common starting materials used as they were halide-free materials. RHODIUM CATALYST, HRh(CO)(PPh3)3
Decompose to metallic cobalt at high temperature and low CO pressure
Very selective in preferred linear aldehyde products due to higher activity under milder condition
One advantage of the HCo(CO)4 technology is that catalyst separation and recycling is well established
Very high linear to branched aldehyde selectivities of 20:1 for a variety of 1-alkenes could be obtained under ambient conditions (25° C, 1 bar 1:1 H2/CO)
The reaction conditions for HCo(CO)4 hydroformylation are largely governed by the thermal instability of HCo(CO)4, which produces metallic cobalt if the CO partial pressure is not kept high enough
In reaction, loss of PPh3 from HRh(CO)(PPh3)2 generates considerably more active, but less regioselective hydroformylation catalysts. Addition of excess phosphine ligand shifts the phosphine dissociation equilibrium back towards the more selective HRh(CO)(PPh3)2 catalyst.
CATALYST T O D A Y
By Akmal, Hakimah, Hanis Azizan, Hafizah & Syahirah Chlorotris(triphenylphosphine)rhodium (I) is known as Wilkinson’s Catalyst. It is a type of homogeneous catalyst used in hydrogenation of olefins. Rhodium in Wilkinson’s with +1 oxidation number has 16-electron configuration. Due to the presence of vacant coordination site, Wilkinson’s catalyst can accommodate an olefin molecule to form six-coordination square planar molecular geometry. Application of Wilkinson’s catalyst Used in selective hydrogenation of alkene and alkyne without affecting the functional groups C=O, CN, NO2 and aryl CO2R
Preparation of Wilkinson’s Catalyst Wilkinson’s catalyst can be prepared by reacting rhodium chloride hydrate (RhCl3.H2O) with excess triphenylphosphine (PPh3) in ethanol (EtOH). Shown below is the balance chemical equation of the reaction: RhCl3•3H2O + P(C6H5)3 ⟶ RhCl[P(C6H5)3]3
CATALYST T O D A Y
Preparation of Wilkinson’s catalyst Place 5 mL of ethanol in a 10 mL roundbottom flask equipped with a magnetic stirring bar.
Collect the product crystals by suction filtration on a Hirsch funnel and dry the crystals on the filter by continuous suction.
Attach a water condenser and place the apparatus on a heating block on a stirrer hot plate.
Heat the ethanol to just below its boiling point (78 ºC).
Remove the condenser momentarily, add 150 mg of triphenylphosphine to the hot ethanol and stir until the solid is dissolved.
Heat the solution to a gentle reflux for ~30 minutes.
Remove the condenser once again, add 25 mg of hydrated rhodium(III) chloride to the solution and continue to stir.
A small amount of solid may remain at this point.
Reaction of Wilkinson’s Catalyst Wilkinson’s catalyst is mainly used in selective hydrogenation of alkene. The examples of the reaction are: 1. Reaction of sterically less hindered and less substituted double bonds is more prefered.
5. Terminal alkynes are hydrogenated faster than terminal alkenes. Acidic alcoholic co-solvents can be used to enhance the selectivity.
2. Exocyclic double bonds will be hydrogenated compared to endocyclic double bonds.
6. Functional groups like C=O, C=N, CO2R, aryl, NO2, are unaffected.
3. Cis alkenes will undergo compared to trans alkenes.
hydrogenation
7. Unsaturated substrates containing functionality are hydrogenated faster.
4. Isolated double bonds will be hydrogenated rapidly over conjugated dienes.
Wilkinson’s catalyst powder
CATALYST T O D A Y
polar
THE PROCESS
By Fatin Nadzirah, Noor Raihan, Munirah, Noor Fatinie & Ashikin
The development of the Wacker process began in 1956 at Wacker Chemie. At that time, the production of acetaldehyde is from acetylene. As time passed by, they discovered that ethylene would be a cheaper raw-material, thus some investigation about its potential uses have been carried out. As the research proceeded, the reaction between ethylene and oxygen over palladium on carbon in a quest for ethylene oxide unexpectedly resulted on formation of acetaldehyde. More research about this reaction takes place resulted in a gas-phase reaction using a heterogeneous catalyst and lastly the previous reaction was replaced by the water-based homogeneous system for the better results. Wacker process is a homogeneous olefin oxidation by tetrachloropalladate(II) catalysts. Specifically, it is an industrial process for the conversion of ethylene into acetaldehyde. The favorable economics of the process is due to the abundance of ethylene present. The discovery and development of Wacker process have been a great contribution to the industrial process of synthesizing aldehyde from alkene. The modification of industrial Wacker process to laboratory scale that is the Tsuji-Wacker Oxidation has led to the synthesis of various kind of ketone. This process has shown an important process driven by transition metal in the catalysis of organic compound. Catalyst is an ihsan towards human being as it helps in the production of compound in a more convenient way. One of the properties of a catalyst is to speed up the chemical reaction. This is also what a human should be until he returns to Allah SWT to be questioned. A person should strive for the best and manage their time wisely to be a productive and effective Muslim as the responsibility of being a khalifah has been given by Allah SWT to the mankind. CATALYST T O D A Y
The first step of this process involves the formation of the olefin complex [Cl3Pd(C2H4)]- . The metal activated olefin is now ready for the nucleophilic attack by water and this step will generate the complex [Cl3Pd-CH2-CH2-OH]2-. β–hydrogen transfer leads to the second olefin complex. Alkyl complex with a hydroxyl group as the substituent is then formed, and this alkyl complex undergoes reductive elimination to produce the desired aldehyde and Pd(0). The presence of copper(II) chloride in the reaction will regenerate or reoxidise the Pd(0) to Pd2+. If there is no oxidising agent to carry out this step, the Pd(0) will be precipitated and the reaction will stop after only one cycle. Later, the Wacker Process was modified for the use in experimental condition. It is called Wacker- Tsuji oxidation. Variety of
ketones and aldehydes is synthesized by using copper as redox co-catalyst as well as palladium-catalyzed oxidation and molecular oxygen as the oxidant. 10 % mol PdCl2, stoichiometric CuCl, organic cosolvent (often DMF), and 1 atmosphere of oxygen gas is mixed with water. When high oxygen pressure and sensible choice of solvent is used, this process can undergo without using co-catalyst, which is copper. If copper is used, Copper(I) is rapidly oxidized to Copper(II) by dissolving in oxygen for 30 minutes in order to complete the oxidation process. Copper(II) minimize concentration of chloride in solution which will induce syn-hydroxypalladation. Besides water, peroxides also can be used as the source of oxygen, in which the co-catalyst is not needed. If the conditions fail, vast modifications of reactions can be applied. CATALYST T O D A Y
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VERILY WITH THE HARDSHIP THERE IS RELIEF [Qur’an 94:6]