Oils, molecular weight reduction

Given that biomass can be converted to a liquid product that is primarily phenolic, then oxygen removal and molecular weight reduction are necessary to produce usable hydrocarbon fuels. Upgrading biomass-derived oils differs from processing petroleum fractions or coal liquids because of the importance of deoxygenation. This topic has received only limited attention in the literature (6-11). 

Polymers are first broken down in an internal mixer where, in addition to the polymer, a peptizer may also be added. This stage is essentially a polymer molecular weight reduction phase. After initial breakdown of the polymer, carbon black, rubber chemicals, and oils can be added to the polymer at intervals to complete the compound formulation. Polymer breakdown and mixing generally occur at a high temperature, up to 180°C. 

The reduction in molecular weight of various fractions of crude oil is an important operation in petroleum chemistry. The process is called cracking. Catalytic cracking is usually achieved by passing the hydrocarbons over a metallic or acidic catalyst, such as crystalline zeolites at about 400-600 °C. The molecular-weight reduction involves carbocationic intermediates and the mechanism is based on the )8-scission of carbenium ions (equation 28). 

Several types of reactions occur on residual oil hydrocracking catalysts(1], molecular weight reduction (hydrogenation and bond cleavage), hydrodemetallization (Ni and V), and heteroatom removal (S, N, and 0). These DESIRABLE REACTIONS can all be generalized as a reaction between a carbonaceous molecule, CM, and hydrogen, as follows ... 

NR requires a certain degree of mastication (reduction in molecular weight) to facilitate processing, although the advent of constant viscosity grades, and oil extended grades has substantially reduced the need for mastication. 

Fractionation of silicone and fluoro fluids. Since solubility depends on molecular weight and temperature/pressure it is possible, particularly with products such as silicone oils and fluorinated liquids" to separate fractions by solubilization and then pressure-reduction steps. 

Cairns JA, Gill J, Morton B, Roberts R, Gent M, Hirsh J, Holder D, Finnie K, Marquis JF, Naqvi S, Cohen E. Fish oils and low-molecular-weight heparin for the reduction of restenosis after percutaneous transluminal coronary angioplasty. The EMPAR Study. Circulation 1996 94(7) 1553-60. 

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