Hydropyrolysis yields

Process development of the use of hydrogen as a radical quenching agent for the primary pyrolysis was conducted (37). This process was carried out in a fluidized-bed reactor at pressures from 3.7 to 6.9 MPa (540—1000 psi), and a temperature of 566°C. The pyrolysis reactor was designed to minimize vapor residence time in order to prevent cracking of coal volatiles, thus maximizing yield of tars. Average residence times for gas and soHds were quoted as 25 seconds and 5—10 rninutes. A typical yield stmcture for hydropyrolysis of a subbiturninous coal at 6.9 MPa (1000 psi) total pressure was char 38.4, oil... 

In this paper we have looked firstly at the effect that the catalyst concentration, secondly at the effect that the reactor temperature and finally at the effect that the residence time at temperature have on the chemical structure of the oils (hexane soluble product) produced on hydropyrolysis (dry hydrogenation) of a high volatile bituminous coal. Generally, the hydropyrolysis conditions used in this study resulted in oil yields that were considerably higher than the asphaltene yields and this study has been limited to the effects that the three reaction conditions have on the chemical nature of the oils produced. 

For a so-called "advanced process of flash hydropyrolysis, (14), a paper by Rockwell International and Cities Service Research and Development reported a 1977 minimum high Btu gas price of 2.36/MMBtu from western subbituminous coal using "AGA/ERDA cost guidelines" with utility financing under conditions yielding significant quantities of by-product BTX liquids. For details, reference was made to contractual reports. 

To test these hypotheses, a tar sand bitumen containing 20 wt % pentane asphaltenes was characterized and processed by hydropyrolysis before and after removal of asphaltenes. Product yields and structure were determined and the influence of asphaltenes on results was determined by inferrence. Feedstocks and products were characterized according to elemental analysis, physical properties, simulated distillation, and carbon-type analysis. Inferences made in this study are discussed in the context of the reported literature. 

Table II and Figures 1-4 summarize the change in product composition from hydropyrolysis of 1 as a function of temperature (between 525°-600°C), keeping a constant hydrogen pressure (500 psig). As seen from Table II, the conversion of 1 increases from 33.8% at 525°C to about 100% at 600°C. Further, the relative yield of gas products increases while that of liquid products decreases with an increase in temperature.

Results and Discussion. Table V summarizes the composition of products obtained by hydropyrolysis and by thermal cracking of 2 at two different temperatures (550° and 600°C). Conversion of 2 is markedly higher in hydropyrolysis than in thermal cracking at both temperatures. At 550°C, the conversion in the hydropyrolysis run (Experiment 23) is higher by a factor of about 3 compared with that in the thermal-cracking run (Experiment 24). Further, a major difference is observed between the two types of reaction at 550°C, viz. hydropyrolysis of 2 yields mainly (76.6%) liquid products, whereas thermal cracking produces mostly (56.3%) gaseous products. However, the difference becomes less pronounced at 600°C. Ci-C3 hydrocarbons are the major constituents of the... 

The observed constancy in the relative yields of liquid and gas products from hydropyrolysis of 2 as a function of pressure (Table VII) shows that hydropyrolysis of polycyclic naphthenes can be carried out... 

Love G. D., Snape C. E., Carr A. D., and Houghton R. C. (1995) Release of covalently-bound alkane biomarkers in high yields from kerogen via catalytic hydropyrolysis. Org. Geochem. 23, 981—986. 

Hydropyrolysis process gives the higher degree of mixture conversion and higher yield of light liquids as compare to pyrolysis in an inert atmosphere. Observed in some cases non-additive effects indicate that the interaction between wood and plastic derived products takes place during mixture thermal treatment. The more pronounced synergistic effects were detected for hydropyrolysis process. Iron catalysts promote the formation of liquid hydrocarbons from biomass/plastic mixtures and influence on their coit sition. 

In co-hydropyrolysis experiments without catalysts the degree of pine wood/ polyethylene mixture (1 1 weight ratio) conversion was 80% wt. and yield of the light liquid fraction - 23% wt. The addition of iron ore catalyst activated by mechanochemical treatment increased the degree of mixture conversion by 5-13%. This increase was mainly due to light liquid fraction formation. The variation of catalyst nature (pyrite, pyrrhotite, haematite) influences on the product composition. Pyirhotite catalyst yields the highest amount of the light fraction (about 40% wt.). 

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. 

Fig. 3. Influence of temperature of pine wood / PE mixtures (1 1) hydropyrolysis in the presence of activated haematite catalyst on the mixture conversion (I) and the yields of light (2), heavy (3) liquid fractions and gas (4).

Fig.4 Influence of polyethylene / pine-wood ratio on the degree of mixture conversion at 390 C and initial pressure H2 5 MPa (1), 3 MPa (2) and on yields of light (3), heavy (4) liquid fractions and gaseous products (5) at hydropyrolysis time 1 h.

According to GC data the gaseous products of polyethylene catalytic hydropyrolysis contain only alkanes. In the runs with polyethylene / biomass mixture at similar conditions carbons oxides were detected in gaseous products and the lower yields of Cj - C4 alkanes was observed,... 

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. 

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