Button center

[snoidev]

Hi, my name is Juan, I speak to you from Argentina; my problem is when centering a botton with bootstrap shortcodes 3

[container xclass="portada"]
[row]
[column md="12" xclass="principal"]
h1 class="title_principal">
Mercado express
/h1>
p class="text_principal">
Loremp ipsum
/p>
[button type="default" size="lg" link="http://localhost/index.php/tienda/" xclass="boton_principal"]
Ir a tienda
[/button]
[/column]
[/row]
[/container]

this is my code, and that button I need to be centered with the text, but when applying the text-align: center in css; it does not work. I would greatly appreciate your help; a big hug from Argentina