Gaseous hydrocarbons plastics

In the Veba process [31], a mixture of vacuum residue, lignite and waste plastics is pyrolyzed under conditions similar to the case of crude oil hydrogenation. The main products include gaseous hydrocarbons, alkanes, cyclanes and aromatics. 

In yet another analysis, Swain found plastic pipes to be about twice as permeable to hydrogen as to natural gas. Even so, the risks were still negligibly small from a safety standpoint. Swain also found that lean hydrogen flames are not visible in the presence of other light sources, but rich hydrogen flames are quite visible, and that the addition of small quantities of gaseous hydrocarbons increases the flame visibility of hydrogen substantially. ... 

This is very similar to pyrolysis, but in this process the mixed plastic waste (MPW) is heated with hydrogen. As the molecules are cracked (the process is often termed hydrocracking), they are saturated with the hydrogen molecules to produce a saturated liquid and gaseous hydrocarbons. The synthetic crude oil produced is of a very high quality. It is necessary to keep the pressure of the hydrogen sufficient to suppress repolymerisation or the generation of undesirable by-products. 

There are liquid PBAs that are volatile and change from a liquid to a gaseous state when heated to the plastic processing temperatures. They are short-chain chlorinated and fluorinated aliphatic hydrocarbons (CFCs). Although they can be used over a wide temperature range and at low (atmospheric) pressures, they have been gradually discontinued due to their role in the reduction of stratospheric ozone.249 Other PBAs are reviewed in Table 8.2. 

Carbon black [1333-86-4] is virtually pure elemental carbon (diamond and graphite are other forms of nearly pure carbon) in the form of near-spherical colloidal particles that are produced by incomplete combustion or thermal decomposition of gaseous or Uquid hydrocarbons. Its physical appearance is that of a black, finely divided pellet or powder, the latter sometimes small enough to be invisible to the naked eye. Its use in tires, mbber and plastic products, printing inks and coatings is related to the properties of specific surface area, particle size and structure, conductivity and color. 

The influence of the process temperature on catalytic hydropyrolysis of biomass/plastic mixture was studied in the range 360 - 460 C. Fig. 3 shows that the highest conversion (91% wt.) of the pine wood / polyethylene mixture (1 1 weight ratio) was observed at 390 C - 430 C in the presence of activated haematite catalyst. Higher tenqieratures promote increased yields of char and gaseous products. At lower temperatures a reduced yield of distillate fraction was observed. In comparison with pyrolysis in inert atmosphere the increased yields of light hydrocarbon fractions (by 1.6 - 1.8 times) and increased degree of mixture conversion (by 1,2 time) were observed for hydropyrolysis process. 

The difference in the composition of gaseous and liquid products of hydropyrolysis of plastic and biomass / plastic mixtures indicates the interaction between intermediate products of natural and synthetic polymers thenrnl conversion. The iron ore catalysts increase the yields of light liquid products and olefinic hydrocarbons. Producing of... 

Iron ore catalysts, modified by mechanical treatment were found to show a catalytic activity in the process of hydropyrolysis of biomas / plastic mixtures. Some synergistic effects were observed in this process resulting in the increase of conversion degree and yield of light liquid fraction and in the decrease of hydrocarbons content in gaseous products. 

A new version of MCFC technology - the direct carbon fuel cell (DCFC) - is under development at the Lawrence Livermore National Laboratory in the USA. Instead of using gaseous fuel, a slurry of finely divided carbon particles dispersed in molten alkali metal carbonates is fed to the cell. The carbon is made by the pyrolysis of almost any waste hydrocarbon e.g., petroleum coke), a process that is already carried out industrially on a large scale to produce carbon black for use in the manufacture of tyres, inks, plastic fillers, etc. The pyrolysis reaction yields hydrogen that can itself be utilized in another fuel cell ... 

---