Are preemies more susceptible to acid reflux?

Yes. Reflux is more common in premies as the muscle at the lower part of the esophagus that contracts to prevent milk from regurgitating back up from the stomach is less developed (and "weaker") in a premie than a term infant. Positioning the baby upright and burping frequently during feedings helps to control reflux symptoms. Sometimes medications may be helpful, especially if the baby is having pain.
Yes they are.... Virtually all babies have some degree of gastroesophageal reflux, but for premature infants the problem is more ever present than for term infants because the lower esophageal sphincter is less well developed in the former. Moreover, reflux can lead to apnea/bradycardia spells in premature infants, so the consequences can be significant. You should discuss your concerns with your pediatrician.