TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Materials: Suitable membrane materials comprise (a) compounds with the fluorite structure (A)2+F2 or (A)4+O2 in which A = Ca, Zr, Bi, La, a lanthanoid, W or Nb, or a combination of these, (b) Perovskite of formula A1-xA1xB1-yB1yO3-d in which A and A1 are not the same; B and B1 are not the same;A, A1 = Group 2 elements, La or lanthanoids;B, B1 = Ce, Ti, Zr, Sn, Tb, Pr, Th, Y, Gd, Nb, Bi, Nd, Sc, Mn, Fe, Co, Ni and/or Cu;x, y = 0-1;d = 0-3, (c) Brownmillerite of formula AxA1qA22-x-qByB1wB22-y-wO5+z in whichA is not = A1 and A2;A = La or a lanthanoid;A1, A2 = La, lanthanoids or Group 2 elements;B is not = B1 and B2;B, B1, B2 = magnesium or Group 3-12 elemments;x, q = 0-2;(x+q) = not more than 2;y, w = 0-2;(y+w) = not more than 2;z = xasteriskW(A) + x1asteriskW(A1) + (2-x-q)asteriskW(A2) + yasteriskW(B) + y1asteriskW(B1) + (2-y-w)asteriskW(B2) - 5;W = the charge on A, A1, A2, B, B1 and B2 in each case, (d) compounds of formula (AA1)(BB1)2O4 in which A, A1, B, B1 = as defined for (c), or (e) compounds of formula (AA1)2(BB1)O4 in which A, A1, B, B1 = as in (c). Preferred membranes are Perovskites as above in whichA = Ba;A1 = Fe;B = Co;B1 = Zr. The catalyst contains an oxide of an element selected from alkaline earth metals, lanthanoids, La, Pb, Zn, Mn, W and mixtures of these; it may also contain a support containing one or more elements selected from Al, Si, Ti, Zr, Y, Ce, La and Mg, and it may be doped with alkali or alkaline earth metals, lanthanoids, La, Mn, Sn, Co, Fe, Ni and/or Al. Preferred catalysts contain Na, W and Mn.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: Reaction in (a) a tubular reactor or a tube bank reactor (using a porous inert tube between catalyst and membrane) or in (b) a plate reactor (with a porous inert plate between catalyst and membrane), preferably in a tubular reactor (a or b) containing spun hollow fibre as the membrane. Gas (B) is air or oxygen- enriched air and gas (A) contains up to 5 mol% nitrogen, helium and/or argon. Reaction is carried out at 600-1000 degrees C, with (B) inside the tubes and (A) on the outside in the case of tubular reactors (a or b). The difference in partial pressure between the side of the membrane facing (B) and the reaction zone (RZ) is at least 0.2 bar and the residence time for (A) and (B) is 0.09-46 l/hour. The membrane may or may not consist of a substance which also acts as a catalyst for the oxidative coupling of methane; in the former case, an additional oxidative coupling catalyst may also be present in the RZ. EXAMPLE - Tests were carried out in a tubular reactor with a perovskite membrane of the type BaFeCoZrO3-d in the form of a wet-spun hollow fibre.An aqueous solution containing 6.27 g manganese(II) nitrate tetrahydrate and 1.59 g sodium tungstate dihydrate was added to a stirred suspension of silica gel (Grade 40) at room temperature (RT), homogenised at 80 degrees C and evaporated slowly to give a slurry which was then dried overnight at 100 degrees C, heated in stages to 170 degrees C and then calcined for 8 hours at 900 degrees C. A suspension of the resulting catalyst (100 mg) in 2 ml water was coated onto a 6-cm porous alumina tube (with a larger i.d. than the o.d. of the fibre membrane) and dried for 1 hour at 90 degrees C. The hollow fibre membrane was placed in the middle of the reactor tube and the catalyst-coated tube was pushed over the fibre, forming a reaction zone 6 cm long with a volume of 6.8 cm3 between the hollow fibre and the reactor wall. After preheating the reactor to 850 degrees C at 10 degrees C/min, air was passed through the hollow fibre at 150 ml/min and 2 bar, while methane (99.995%) was passed between the fibre and the reactor wall at a pressure of 1 bar. With a methane flow rate of 3 ml/min and an oxygen concentration of 0 micro-M at the reactor outlet, the process gave selectivities of 84 (71) % for conversion to ethane and ethene or 89 (77) % for total 2-3C hydrocarbons, with an unreacted methane level of 11 (12) % and an ethane/ethene yield of 9.2 (8.5) % based on total methane used. Values in brackets are for a residual oxygen content of 30 micro-M with the same methane input. If the amount of residual oxygen was increased to 55 micro-M with a methane flow rate of 50 ml/min, corresponding values were 78%, 81%, 2.2% and 1.7%.; overall, selectivity for 2C hydrocarbons decreased from 84% for an outlet oxygen concentration of zero to 60% at 205 micro-M.