From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Article discussing the processes of converting heavy crude oil into petrol, including distillation and cracking.
| Identifier | ExFiles\Box 32\1\ Scan022 | |
| Date | 8th March 1913 | |
| MARCH 8, 1913. THE AUTO -MOTOR JOURNAL. they have a convenient outlet in this direction. Trinidad is another oilfield of great promise, which is at present under development, but it will take time before these centres seriously affect the world's supply even if they do prove equal to anticipations. Neither the Californian nor the Mexican petroleum is naturally rich in light hydrocarbons, and from the motorists' standpoint it is, of course, these products that count most. There thus attaches a very great interest and importance to any process that can succeed in accomplishing what ordinarily is performed under ground by nature in the way of converting heavy oil into spirit. It is the light hydrocarbons thus produced that may appropriately be termed synthetic petrol. It has been explained that the crude oil as it comes from the earth contains a range of light hydrocarbons that collectively are called “petrol” on the English market. They are separated from the crude petroleum by distillation—that is to say, they are evaporated and recondensed. By any straightforward process of distillation it is impossible to increase the amount of petrol beyond the quantity originally contained in the crude oil. This quantity varies widely in different localities, being in the order of 10 per cent. for the oilfields that produce the Shell spirit as it has hitherto been supplied. An experiment of great interest and importance, made in 1871 by Thorpe and Young, resulted in the discovery that the repeated redistillation of a heavy hydrocarbon under a temperature in excess of its boiling point, and under a pressure greater than atmospheric, resulted in its conversion into lighter fractions. Paraffin wax was, in fact, by this means converted into spirit. In the experiment, it was distilled and redistilled from one end to the other of a bent, sealed tube, which afforded a simple means of obtaining the requisite temperature and pressure. The term “cracking” is applied to this operation in order to distinguish it from ordinary distillation. The story is also told of the independent discovery in America of the same effect, which was noticed as occurring on an occasion when the process of distillation was proceeding so slowly that the lighter fractions were allowed to condense on the roof of the still and to fall back into the hot oil, which had a temperature in excess of the boiling point of these lighter fractions themselves. It was found that the quantity of spirit so produced from a given quantity of crude oil was somewhat increased by allowing this cracking action to take place. It will be apparent that cracking is properly to be regarded as a process related to the synthesis of petrol, but more recent developments, which are still in an experimental stage, now draw attention to possible advantages from a process that cannot adequately be described as ordinary “cracking.” This process, briefly, consists in feeding oil and water simultaneously into a heated retort that contains a suitable catalyst such as nickel or iron. The retort is maintained at a temperature in the order of 600° C., and in some processes is also under high pressure, but the high pressure is clearly a disadvantage in any apparatus that is simultaneously subjected to great heat. The catalyst, which in one process with which we are acquainted, consists of iron turnings, while another apparatus uses nickel rods, has the effect of accelerating the conversion of the heavy oil into lighter fractions, but is in itself unaffected by the change. Precisely what happens inside the retort is not clearly known, although theories on the subject are not lacking. For the moment, however, it is more important to know whether such a process is or is not of such a character as may be commercially useful. That it is of great interest is apparent on the face of it, and that it is of potential importance is equally self-evident, but it has not yet been developed to a point at which it is possible to say more than that the broad principle is one of promise. By this we do not mean to say that any such process is capable of effecting an immediate reduction in the price of petrol, for we have made it very clear already that we see no reason to anticipate other than an increase in the price of motor spirit under present circumstances. It would, however, be of the utmost utility to have satisfactory means of increasing the proportion of petrol available from crude petroleum, because the demand for the lighter hydrocarbons would probably make it worth while working such a process provided it could be operated at a reasonable figure. The estimated cost of producing “petrol” from fuel oil, for example, is, we understand, in the order of 1½d.{John DeLooze - Company Secretary} to 2d. a gallon, but everything naturally depends on the market value of the residue. While a process of this sort will doubtless interest large individual users who might be able to acquire sufficient supplies of fuel oil such as they might already be using in stationary Diesel engines and part of which they could convert into cheap petrol for their own purposes, it is not from the wholesale conversion of some already existing group of heavy fractions that one must look for the solution of the world's liquid fuel problem, for such conversion would, after all, merely be robbing Peter to pay Paul. Fuel oil, in common with the other petroleum products, has its own particular market, and were it to be converted wholesale into petrol it would equally produce a famine in a field of industry that is just as important to those engaged in it as is automobilism to the motorist. (To be continued.) | ||