In autocatalysis, the reaction is catalysed by one of its products. One of the simplest examples of this is in the oxidation of a solution of ethanedioic acid (oxalic acid) by an acidified solution of potassium manganate(VII) (potassium permanganate).

The reaction is very slow at room temperature. It is used as a titration to find the concentration of potassium manganate(VII) solution and is usually carried out at a temperature of about 60°C. Even so, it is quite slow to start with.

The reaction is catalysed by manganese(II) ions. There obviously aren't any of those present before the reaction starts, and so it starts off extremely slowly at room temperature. 

NUR SYAHIRAH BINTI JAAPAR
55214115028

By using chiral catalysts or asymmetric catalysts the single active enantiomer can be produced. In the 1970s William Knowles found that rhodium bonded to chiral phosphine ligands could perform asymmetric catalytic hydrogenation. The method was soon developed for the commercial production of the anti-Parkinson drug, l-dopa. 

One of the example of chiral catalysts is (R,R)-N,N′-Bis(3,5-di-tert-butylsalicylidene)-1,2- cyclohexanediaminoaluminum chloride. This catalyst is used for Asymmetric iodolactonizations, Cyanosilylation reactions and Phospho-aldol catalysis.

 
Today, with the huge expansion of the pharmaceutical industry, there is demand for chiral compounds and other chiral catalysts are now being developed.

ABDUL RAHMAN B MOHD SAUFIAN
55211115321

 

The cage-like structure of zeolites makes them useful in all sorts of ways. One of the biggest everyday uses for zeolites is in water softeners and water filters. In ion-exchange water softeners, for example, hard water (rich in calcium and magnesium ions) is piped through a column filled with sodium-containing zeolites. The zeolites trap the calcium and magnesium ions and release sodium ions in their place, so the water becomes softer but richer in sodium. Many everyday laundry and dishwasher detergents contain zeolites to remove calcium and magnesium and soften water so they work more effectively.

AMEERA NURUL SARAH BINTI AZMAN

55214115287

(WGS) reaction:

CO + H₂O ↔ H₂ + CO₂ |   |   | 
  | (1)

The reaction refers to carbon monoxide (CO) that reacts with water (H₂O) to form carbon dioxide (CO₂) and hydrogen (H₂). The reaction is exothermic with ΔH= -41.1 kJ/mol and have an adiabatic temperature rise of 8–10 °C per percent CO converted to CO₂ and H₂.

The most common catalysts used in the water-gas shift reaction are the high temperature shift (HTS) catalyst and the low temperature shift (LTS) catalyst. The HTS catalyst consists of iron oxide stabilized by chromium oxide, while the LTS catalyst is based on copper. The main purpose of the LTS catalyst is to reduce CO content in the reformate which is especially important in the ammonia production for high yield of H₂. Both catalysts are necessary for thermal stability, since using the LTS reactor alone increases exit-stream temperatures to unacceptable levels.

The equilibrium constant for the reaction is given as:

K_p=(p_H2 x p_CO2)/ (p_CO x p_H2O) |   |   | 
  | (2)

K_p=e^{((4577.8K/T-4.22))} |   |   | 
  | (3)

Low temperatures will therefore shift the reaction to the right, and more products will be produced. The equilibrium constant is extremely dependent on the reaction temperature, for example is the Kp equal to 228 at 200 °C, but only 11.8 at 400 °C. The WGS reaction can be performed both homogenously and heterogeneously, but only the heterogeneously way is used commercially.

The important use of vanadium(V) oxide is in the manufacture of sulfuric acid , an important industrial chemical with an annual worldwide production of 165 million metric tons in 2001, with an approximate value of US$8 billion. Vanadium(V) oxide serves the crucial purpose of catalysing the mildly exothermic oxidationof sulphur dioxide to sulphur trioxide by air in the contact process:

2 SO₂ + O₂ ⇌ 2 SO₃

The discovery of this simple reaction, for which V₂O₅ is the most effective catalyst, allowed sulfuric acid to become the cheap commodity chemical it is today. The reaction is performed between 400 and 620 °C; below 400 °C the V₂O₅ is inactive as a catalyst, and above 620 °C it begins to break down. Since it is known that V₂O₅ can be reduced to VO₂ by SO₂, one likely catalytic cycle is as follows:

SO₂ + V₂O₅ → SO₃ + 2VO₂

followed by

2VO₂ +½O₂ → V₂O₅

It is also used as catalyst in the selective catalyst reduction(SCR) of NO_x emissions in some power plants. Due to its effectiveness in converting sulfur dioxide into sulfur trioxide, and thereby sulfuric acid, special care must be taken with the operating temperatures and placement of a power plant's SCR unit when firing sulfur-containing fuels.

ID NUM: 55214115228

REACTION: Manufacture of epoxyethane from ethane

CATALYST: Silver

This manufactured is occurred when ethane is reacting with a limited amount of oxygen in the presence of silver as a catalyst. The reaction happened at 250-300 degree Celsius and pressure less than 15 Atm. The solid silver is catalyzing the gas reaction. It is also known as heterogeneous catalysis. The reaction need to be controlled carefully to prevent further oxidation of the ethane to carbon dioxide and water.

The next step is to feed the sulphur dioxide into a converter in order to produce sulphur trioxide in the reaction;

2SO₂(g) + 0₂(g) -> 2SO₃(g)

The sulphur dioxide is oxidized to sulphur trioxide by the use of vanadium (V) oxide as the catalyst. In the process the vanadium (V) oxide is reduced vanadium (IV) oxide. The vanadium (IV) oxide, V₂O₄ is then re-oxidized by the oxygen.

For example, in reforming naphtha (a mixture of straight chain alkanes, with 6-10 carbon atoms) a bifunctional catalyst is used. The most well known one is platinum impregnated on the surface of alumina and both the metal and the oxide play their parts in the process. As can be seen (Figure 10), the first step is the dehydrogenation of the alkanes to alkenes, catalysed by the metal, followed eventually by adsorption of the alkene molecules on alumina. Because platinum is involved, the reforming is sometimes called platforming. The hydrogen ensures that the resulting alkenes and cycloalkenes subsequently react with hydrogen to form saturated compounds.

In this example butane is dehydrogenated to butene.

The branched alkene molecule is desorbed into the gas phase until it is readsorbed on to a metal site where it is hydrogenated to form a branched alkane, 2-methylpropane (isobutane), which is then desorbed into the gas phase.

In the industrial process, naphtha vapour is passed over platinum and rhenium (ca 0.3% each) which are finely dispersed over aluminium oxide. The rhenium is thought to play an interesting role. If a sulfur compound is allowed to pass over the surface of the catalyst, it is preferentially adsorbed by the rhenium. If sulfur compounds are not removed, reactions occur leading eventually to the formation of carbon which causes the activity of the catalyst to be markedly reduced.

Equation : Making Naphtha

This formation and breaking up of ozone is going on all the time. Taken together, these reactions stop a lot of harmful ultraviolet radiation penetrating the atmosphere to reach the surface of the Earth.

The catalytic reaction in destroys the ozone and stops it absorb the UV:

Chlorofluorocarbons (CFCs) like CF₂Cl₂, for example, were used extensively in aerosols and as refrigerants. Their slow breakdown in the atmosphere produces chlorine atoms - chlorine free radicals. These catalyse the destruction of the ozone.

This happens in two stages. In the first, the ozone is broken up and a new free radical is produced.

The chlorine radical catalyst is regenerated by a second reaction. This can happen in two ways depending on whether the ClO radical hits an ozone molecule or an oxygen radical.

If it hits an oxygen radical (produced from one of the reactions):

Or if it hits an ozone molecule:

Because the chlorine radical keeps on being regenerated, each one can destroy thousands of ozone molecules.

 

 

 

 

 

This is a fairly pointless reaction because ethene is a far more useful compound than ethane! However, what is true of the reaction of the carbon-carbon double bond in ethene is equally true of it in much more complicated cases.

Catalysts can be divided into two main types - heterogeneous and homogeneous. In a heterogeneous reaction, the catalyst is in a different phase from the reactants. In a homogeneous reaction, the catalyst is in the same phase as the reactants.

 Amorphous silica are used for a multitude of different purposes [3]. They serve as reinforcers/fillers in the indiarubber industry and as additives in varnishes, paints and glues. In addition, amorphous silica are used in the production of free-flowing powders for foodstuffs, animal feeds, pharmaceuticals and cosmetics. Adsorbents and insulation materials are more recent applications. The ability of amorphous silicas to modify flow properties (thixotropism) is put to use in paint production. Paints should be as easy as possible to apply, which requires a low viscosity, and once applied should remain on the painted surface without dripping or forming runs, for which a high viscosity is necessary. The properties of amorphous silicas have led to their wide distribution as technical additives, e.g. in resins. Silicas are added to unsaturated polyester resins (UP resins) and epoxide resins to adjust their viscosity for industrial applications involving laminar processes. The rheological properties play a role in mixtures with PVC plastisols for the production of imitation leather and of underbody protective coatings. Other areas of application include pharmaceuticals and cosmetics. Amorphous silicas serve to adjust the viscosity of creams, ointments, suppositories and pastes. Finally they are used in the production of moulds.