If ethanol is your only allowed starting material, then here's a possible sequence.
Step 1. Ethanol to chloroethane
#underbrace("CH"_3"CH"_2"OH")_color(red)("ethanol") stackrelcolor(blue)("SOCl"_2, "Py"color(white)(mm))(→) underbrace("CH"_3"CH"_2"Cl")_color(red)("chloroethane")#
Step 2. Chloroethane to sodium acetylide
#underbrace("CH"_3"CH"_2"Cl")_color(red)("chloroethane") + stackrelcolor(blue)("Alc. KOH, Δ"color(white)(mm))(→) underbrace("CH"_2"=CH"_2)_color(red)("ethene")#
#underbrace("CH"_2"=CH"_2)_color(red)("ethene") + "Br"_2 → underbrace("BrCH"_2"-CH"_2"Br")_color(red)("1,2-dibromoethane")#
#underbrace("BrCH"_2"-CH"_2"Br")_color(red)("1,2-dibromoethane") + "NaNH"_2 stackrelcolor(blue)("Liq. NH"_3color(white)(mm))(→) underbrace("HC≡C"^"-""Na"^"+")_color(red)("sodium acetylide")#
Step 3. Chloroethane + sodium acetylide to but-1-yne
# underbrace("CH"_3"CH"_2"Cl")_color(red)("chloroethane") + underbrace("HC≡C"^"-""Na"^"+")_color(red)("sodium acetylide") → underbrace("CH"_3"CH"_2"C≡CH")_color(red)("but-1-yne")#
If you are allowed to use other organic compounds in your sequence, you can replace Step 2 with this:
#underbrace("HC≡CH")_color(red)("ethyne") + "NaNH"_2 stackrelcolor(blue)("Liq. NH"_3color(white)(m))(→) underbrace("HC≡C"^"-""Na"^"+")_color(red)("sodium acetylide")#
