Is that category or custom taxonomy?

if this is a category, then try this one.

<?php
$loop = new WP_Query(
array(
    'post_type' => 'portfolio',
    'posts_per_page' => 50,
    'category__in' => array('8','9','10'), // your category ids
)
);
while ( $loop->have_posts() ) : $loop->the_post();

?>

<div class="half-column">
<h2><?php the_title(); ?></h2>
</div>

<?php endwhile;
wp_reset_postdata();
?>

Or if this custom taxonomy, try this one

<?php
$loop = new WP_Query(
array(
    'post_type' => 'portfolio',
    'posts_per_page' => 50,
    'tax_query' => array(
        array (
            'taxonomy' => 'yourTaxonomy',
            'field' => 'slug', //type, id or slug
            'terms' => 'yourTermSlug',
        )
    ),
)
);
while ( $loop->have_posts() ) : $loop->the_post();

?>

<div class="half-column">
<h2><?php the_title(); ?></h2>
</div>

<?php endwhile;
wp_reset_postdata();
?>

let me know the update.
Thank You