ethane, and ethyne at its equator than it does at its poles
HDPE is produced by three types of process. All operate at relatively low pressures (10-80 atm) in the presence of a Ziegler-Natta or inorganic catalyst. Typical temperatures range between 350-420 K. In all three processes hydrogen is mixed with the ethene to control the chain length of the polymer.
The diagram shows the apparatus used to prepare ethane
Used in baking powders containing citric acid or tartaric acid, they react together to form carbon dioxide gas which produces the rising action in the bread dough or cake mix etc.
Well over 80 million tonnes of poly(ethene), often known as polyethylene and polythene, is manufactured each year making it the world's most important plastic. This accounts for over 60% of the ethene manufactured each year.
Properties Uses and Production of Ethene Chemistry Tutorial
Ethene (purity in excess of 99.9%) is compressed and passed into a reactor together with the initiator. The molten poly(ethene) is removed, extruded and cut into granules. Unreacted ethene is recycled. The average polymer molecule contains 4000-40 000 carbon atoms, with many short branches.
The maximum yield of ethyne was found to ..
There are about 20 branches per 1000 carbon atoms. The relative molecular mass, and the branching, influence the physical properties of LDPE. The branching affects the degree of crystallinity which in turn affects the density of the material. LDPE is generally amorphous and transparent with about 50% crystallinity. The branches prevent the molecules fitting closely together and so it has low density.
Compounds that contain more than two double bonds are called polyenes
The catalyst, as granules, is mixed with a liquid hydrocarbon (for example, 2-methylpropane (isobutane) or hexane), which simply acts as a diluent. A mixture of hydrogen and ethene is passed under pressure into the slurry and ethene is polymerized to HDPE. The reaction takes place in a large loop reactor with the mixture constantly stirred (Figure 4). On opening a valve, the product is released and the solvent is evaporated to leave the polymer, still containing the catalyst. Water vapour, on flowing with nitrogen through the polymer, reacts with the catalytic sites, destroying their activity. The residue of the catalyst, titanium(IV) and aluminium oxides, remains mixed, in minute amounts, in the polymer.
Polyenes and dienes share many of their properties
The second method involves passing ethene and hydrogen under pressure into a solution of the catalyst in a hydrocarbon (a C10 or C12 alkane). The polymer is obtained in a similar way to the slurry method.
Chemical reactions - Encyclopedia Britannica | …
This poly(ethene), known as mLLDPE, is produced by a new family of catalysts, the . Another name for this family is single site catalyst. The benefit is that the mLLDPE is much more homogenous in terms of molecular structure than classical LLDPE produced by Ziegler-Natta catalysts. Each catalyst is a single site catalyst which produces the same PE chain. Chemists have compared the structure of metallocenes to that of a sandwich. There is a transition metal (often zirconium or titanium) 'filling' a hole between layers of organic compounds.