Ethanol is heated with excess concentrated $\mathrm{H}{}_2\mathrm{SO}{}_4$ at 443 K. The main organic product is

Concentrated $\mathrm{H}{}_2\mathrm{SO}{}_4$ in excess at 443 K dehydrates ethanol by elimination of water (via ethyl hydrogen sulphate), giving ethene. Diethyl ether forms with excess alcohol at about 413 K, not at 443 K.