*3.3. Catalyst Preparation*

Mixed oxide catalysts were synthesized via wet impregnation of a Zn(NO3)2 · 6H2O solution on Zr(OH)4 as described elsewhere [22]. The Zr(OH)4 was initially dried overnight at 105 ◦C to remove any excess water on the surface before impregnation. After impregnation, the catalysts were dried overnight at room temperature and then for 4 h at 105 ◦C prior to calcination. The catalysts then were calcined via a 3 ◦C min−<sup>1</sup> ramp to 400 ◦C for 2 h, followed by a 5 ◦C min−<sup>1</sup> ramp to the final calcination temperature of 550 ◦C for 3 h. Extensive details of the catalyst characteristics have been published previously and are not reproduced here [19–22].

### *3.4. Reactor and Reaction Conditions*

Olefin production reactions were performed in a 1 2 " inch outer-diameter, fixed-bed alumina reactor. Alumina reactors were used to minimize potential side reactions that might occur with stainless steel reactors. Typically, 0.70 g of Zn1Zr2.5O was loaded undiluted. Prior to testing, catalysts were degassed under N2 at 450 ◦C for 8 h.

The catalysts were tested at atmospheric pressure and at a reaction temperature of 450 ◦C. The liquid feed was fed via HPLC pump to a vaporizer held at 150 ◦C. A N2 gas flow rate (typically ~50 mol% in the feed) was introduced into the system to serve as the carrier gas and internal reference standard. Both liquid and gas feed were adjusted accordingly to achieve desired GHSV. On-line gas products were tracked via four-channel MicroGC ® and condensable products were analyzed o ff line via LC analysis, as described previously [13]. The reported conversion is based on the ratio of feed carboxylic acids to carboxylic acids remaining after reaction. For all reactions total carbon balance was >95% and measurement errors in composition are <1%.
