Patent GB-368291-A (GB)
Title: Improvements in the conversion of hydrocarbons at higher temperatures
IPC: B01J19/00
Filed: 1930-10-24
Abstract: <PICT:0368291/III/1> The thermal treatment of hydrocarbons substantially free from acetylene is effected by passing them in the vaporous state into a space maintained at an elevated temperature and confined by a surface comprising free elementary silicon.  The parts of the apparatus concerned are preferably constructed of moulded parts prepared from elementary silicon by casting, if desired with the addition of fluxes or slagforming materials, or by the methods usual in the ceramic industry, if desired with the addition of binding agents such as low-melting silicates, or high-melting materials such as clay and cements.  Tubes comprising silicon embedded in other gastight tubes or coated with a suitable gastight glaze may be used.  Metals, especially chromium nickel steels, may be used for the outer protective tubes if an intermediate layer of lead, a cement of equal parts of silica and alumina, or other suitable material not forming alloys with either the metal or the silicon be employed.  Apparatus constructed of plates or bricks containing silicon may be used instead of tubes. Not only the reaction chambers but preheaters and other parts of the apparatus subjected to temperatures above 200 DEG  C. may be made with or coated with silicon.  In parts of the apparatus where temperatures from 200-500 DEG  C. only occur, coatings of enamels containing elementary silicon may be used.  The invention is applicable to the conversion of hydrocarbons of high molecular weight into those of low molecular weight, to the distillation of hydrocarbons, hydrogenating treatments, and the dehydrogenation or cracking of hydrocarbons at temperatures from 300-1200 DEG  C. Examples are given, in one of which a German mineral oil is distilled through a silicon tube embedded in a copper tube heated to 700 DEG  C. in such a way that the undecomposed oil flows back to the still, liquid aliphatic hydrocarbons and a gas containing paraffins and olefines being obtained.  In another example a Cowper apparatus is filled with pieces of silicon 1.  The pressure resistant wall 2 of suitable metal such as V2A steel is provided with cooling tubes 3 and surrounds a wall of fireclay 9 coated with plates of silicon 10.  Hydraulically operated means 5, 4 enable the space to be closed at the top and bottom respectively.  After heating the reaction space by means of a burner 6 to about 650 DEG  C. a brown coal tar distillate preheated to 550 DEG  C. is pumped in through a pipe 7 until the pressure is raised to 25 atmospheres, and the reaction gases are then led off at 8 while supplying oil to maintain this pressure.  By cooling the reaction product and absorption with active charcoal a condensate containing benzene and a gas containing paraffins and olefines is obtained.  In a further example a mixture of 90 per cent methane and steam preheated to 200 DEG  C. is passed at 900-950 DEG  C. through a tube prepared from material containing 80 per cent free silicon coated externally with an aluminium silicate glaze, and filled with pieces of a catalyst consisting of chromic anhydride and nickel nitrate.  After separating the steam from the reaction products a gas containing 75 per cent of hydrogen is obtained.ALSO:The thermal treatment of hydrocarbons substantially free from acetylene is effected by passing them in the vaporous state into a space maintained at any elevated temperature and confined by a surface comprising free elementary silicon.  The parts of the apparatus concerned are preferably constructed of moulded parts prepared from elementary silicon by casting, if desired with the addition of fluxes or slag-forming materials, or by the methods usual in the ceramic industry, if desired with the addition of binding agents such as low-melting silicates, or high-melting materials such as clay and cements.  Processes to which the invention is applicable include the continuous conversion of lower olefines into higher gaseous olefines, the production of liquid aliphatic or aromatic hydrocarbons from olefines, the conversion of homologues of methane into gaseous olefines or liquid hydrocarbons, and the production of low-molecular hydrocarbons from high-molecular hydrocarbons.  Tubes made from silicon powder with a binding agent containing silicates and clay are especially suitable for the preparation of liquid hydrocarbons particularly of benzene from methane or gases containing methane at temperatures above <PICT:0368291/IV/1> <PICT:0368291/IV/2> <PICT:0368291/IV/3> 950 DEG  C.  Tubes comprising silicon may be used embedded in other gastight tubes, or may be coated externally with a gastight glaze, and heated electrically, the cross section of the tubes being preferably enlarged at the entry end; or such glazed tubes may be heated directly.  Shafts lined with plates prepared from silicon powder may also be used as reaction chambers.  Silicon may be used not only as a constructional material or coating for the reaction chambers proper, but also for other parts of the apparatus such as preheaters, and advantageously for all parts exposed to temperatures above 200 DEG  C.  In parts of the apparatus where temperatures of about 200-500 DEG  C. only occur, elementary silicon may be used in the form of enamels.  The invention is further applicable to processes such as the distillation of hydrocarbons, hydrogenating treatments, the dehydrogenation or cracking of hydrocarbons at temperatures from 300 to 1200 DEG  C., the condensation of lower hydrocarbons to form higher gaseous and liquid hydrocarbons at temperatures from 200 to 1200 DEG  C., and processes in which special catalysts are employed.  Metals, especially special steels stable to heat, such as chromium-nickel steels, can be employed as outer tubes protecting the silicon tubes, if an intermediate layer of a substance not forming alloys with either the silicon or the metal be employed.  Suitable materials for the intermediate layer are metals such as lead or ceramic materials which melt slightly over the working temperature, for example, such as melt at 1100-1200 DEG  C. and at 1000 DEG  C. form a glaze impermeable to gases.  The walls of the silicon tube may be provided with a glaze preventing diffusion of silicon vapour to the protecting tube by using a weakly basic cement consisting of equal parts of silica and alumina.  Instead p  of tubes, apparatus constructed of small plates, bricks, or the like may be used.  When using metallic protecting tubes higher pressures may be employed in conjunction with temperatures which may be below 500 DEG  C.  Apparatus lined with silicon is suitable for use when treating hydrocarbon gases or vapours containing impurities such as sulphur compounds which attack metal parts, or when carrying out reactions such as those in which aluminium chloride is used under pressure, in which bye-products injurious to metal apparatus are first formed.  When carrying out endothermic conversion of hydrocarbons in periodically heated chambers, the filling material is preferably also made with silicon, or else coated therewith, for example, by applying the material in a thin layer with or without a binding agent, and forming the coating by sintering it.  According to examples, (1) a gas containing methane is passed through interlocked silicon tubes inserted in a quartz tube heated in an electric furnace to 1030 DEG  C., liquid hydrocarbons containing benzene and toluene and a residual gas containing acetylene being obtained; (2) a tube 20, Fig. 1 (32028/30), made of material containing over 80 per cent free silicon and provided with an aluminium silicate glaze is heated in a furnace 23 with down-flowing gases which enter at 14 at about 1000 DEG  C.  Through the tube 20 a gas containing methane, ethane, propane, butane, ethylene, and propylene is passed from a container 21.  The reaction gases are cooled in a vessel 16, pass through a condenser 18 into an electric separator 19, then through low-temperature condensers 10a, 10b, and are finally conveyed by a pipe 12 to a gas container 13 having an exit pipe 24.  Liquid products collecting in vessels 17, 22, 11 comprise benzene, toluene, xylene, naphthalene, alkylated naphthalene, and higher aromatics.  The residual gases contain ethylene and higher olefines, and may be again treated or used for the production of pure ethylene; (3) vaporized hexahydrobenzene is passed through a silicon tube embedded in a porcelain tube and filled with silicon pieces at a temperature of 750 DEG  C.  Liquid hydrocarbons including butadiene and a gas containing methane, ethane, ethylene, and propylene are obtained; (4) a German mineral oil is distilled through a silicon tube embedded in a copper tube heated to 700 DEG  C., in such a way that the undecomposed oil flows back to the still.  Liquid aliphatic hydrocarbons and a gas containing paraffins and olefines are produced; (5) a gas containing methane together with vapours of an American mineral oil rich in paraffins is passed through a tube constructed as at (2) and heated by combustion gases to 770-910 DEG  C., liquid aliphatic and aromatic hydrocarbons and a residual gas comprising methane, ethylene, and propylene being obtained; (6) the lower part 3 of a reaction chamber, Fig. 2 (33804/30), filled and lined with bricks moulded from elementary silicon is heated to 1100 DEG  C. by means of combustion gases introduced at 6.  The upper part 2 acting as a preheater is heated so that the combustion gases leave at 7 at about 500 DEG  C. After closing 6, 7, 90 per cent methane preheated to about 500 DEG C. in a regenerator 5 is led through 1 with slowly decreasing velocity.  The reaction gases leave at 4 and pass through the regenerator 5 to a cooler and condensing plant.  A condensate containing 60 per cent benzene is obtained.  The combustion gases and air are preheated by the hot gases leaving the reaction chamber; (7) a gas obtained by heating pulveri