TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Catalyst: The zeolite catalyst is selected from (i) and has faujasite (FAU), or BEA structure (preferably zeolite Y, zeolite X, or zeolite Beta); or is selected from (ii) and has MWW structure (preferably MCM-22). The zeolite catalyst comprises non-framework metal ions. The zeolite catalyst is an aluminosilicate. The zeolite catalyst comprises heteroatom selected from at least one phosphorus, gallium, titanium, germanium, vanadium, iron and cobalt at a loading of up to 10 mol% based on the number of non-oxygen framework atoms in the framework. The catalyst is preferably selected from at least one zeolite having frameworks comprising silicon and aluminum atoms and which have a framework ring comprising greater than or equal to 12 non-oxygen-atoms accessible on the surface of the zeolite and a pore structure in which all of the channels have a ring-size of less than 12 non-oxygen atoms. Preferred Components: The non-framework metal ions are present at a loading of 1-10 mol%, based on the negative charge of the framework. The non-framework metal ions are selected from at least one silver, barium, bismuth, calcium, cerium, copper, cesium, indium, lanthanum, lithium, rhodium, palladium, platinum or zinc. In the case of type (i), the non-framework metal ion used is preferably silver, copper or cesium (especially silver or copper). In the case of (ii), the non-framework metal ion used is preferably cesium, and is present at a loading of greater than or equal to 1 (preferably 1-10) mol% relative to the T-element content of the zeolite.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The process is operated at a temperature of 200-350 degrees C, and a gas hourly space velocity (GHSV) of less than or equal to 5000 h-1 (preferably greater than or equal to 500 h-1). Preferred Components: The reaction composition comprises methanol and/or dimethyl ether. The reaction composition comprises at least one further oxygen-containing carbon compound selected from 2-6C alcohols and/or their derivatives. The olefins are selected from 2-6C olefins (preferably 2,3-dimethyl-2-butene). EXAMPLE - Mixture of methanol and 2,3-dimethyl-2-butene (2,3-DMB) in a 20:1 molar ratio was diluted in nitrogen at a nitrogen:(methanol+2,3-DMB) molar ratio of 4:1. The feedstock was fed over aluminosilicate zeolite (MCM-22) at a pressure of 0.1 MPa, a temperature of 275 degrees C, and a total gas hourly space velocity (GHSV) of 2000 h-1 to give triptyl yields of greater than or equal to 0.8% and triptyl fractions of greater than 5% of 7C hydrocarbons.