Pyrolysis gasoline (PyGas) is an unstable byproduct of the pyrolysis of naphtha and other hydrocarbons for the production of olefins. PyGas is stabilized by hydrogenation at mild conditions. The hydrogenation of styrene to ethylbenzene is considered a model test reaction for studying the selectivity of the catalysts because it has the slowest rate of conversion. The catalytic activity and selectivity of two bimetallic co-impregnated Pd–Ni catalysts supported on γ-alumina were assessed and compared to those of a commercial monometallic Pd catalyst (AXENS LD265). The laboratory-prepared catalysts had different metal content and Pd:Ni atomic ratios (1:1 and 1:7). Catalytic tests of selective hydrogenation of styrene to ethylbenzene were made in a batch stirred tank reactor and in a continuous fixed bed trickle bed reactor. The sulfur resistance of the bimetallic catalysts in semicontinuous condition, was assessed by means of the same operational conditions using thiophene as a model poison compound. The support, Pd–Ni co-impregnated catalysts and LD265 commercial catalysts were further characterized by N₂ chemisorption, EPMA, OM, ICP elemental analysis, temperature programmed reduction, XPS and X-Ray diffraction. The results indicated the presence of different metal species: Pd⁰, Pd^δ+, Ni⁰ and NiO. The lab-prepared bimetallic catalysts were found to be active for the selective hydrogenation of styrene (both in the batch and continuous system). During the continuous evaluations, the commercial LD265 catalyst had an intermediate activity level that lied between the values corresponding to the Pd–Ni bimetallic catalysts: PdNi(1:1) \( \gg \) LD265 > PdNi(1:7). During the poison free semicontinuous evaluations, the pattern of conversion as a function of contact time of co-impregnated Pd–Ni catalysts are quite similar to that of commercial LD265 catalyst, though the catalytic activity is slightly better for PdNi(1:1). After 90 min of contact time the order of conversion was: PdNi(1:1) > LD265 > PdNi(1:7). On the other hand, during the poison semicontinuous tests (with 300 pp of thiophene), the initial reaction rates of the co-impregnated catalysts decreased, pointing a poisoning of the active sites by thiophene. PdNi(1:1) had higher initial reaction rate than PdNi(1:7) during poison free or poisoned in both conditions. PdNi(1:7) was more sulfur resistant than PdNi(1:1). The higher activity of the PdNi(1:1) catalyst was attributed to the presence of Pd⁰ and Pdⁿ⁺/Ni^m+ species that favored respectively, the homolytic cleavage of the H–H bond and the adsorption of styrene. The higher sulfur resistance of the PdNi(1:7) catalyst would be associated with the higher Cl/Al surface atomic ratio in this catalyst (electronic effect) and the presence of electrodeficient species of Pd (Pd_x^δ+O_yCl_z) that prevented the adsorption of thiophene by steric hindrance (geometrical effect of the large species) or by electronic effects.

热解汽油（PyGas）是石脑油和其他碳氢化合物热解生成烯烃的不稳定副产物。PyGas通过在温和条件下氢化而稳定。苯乙烯加氢成乙苯被认为是用于研究催化剂选择性的模型测试反应，因为它具有最慢的转化率。评估了负载在γ-氧化铝上的两种双金属共浸渍的Pd-Ni催化剂的催化活性和选择性，并将其与商业单金属Pd催化剂（AXENS LD265）进行了比较。实验室制备的催化剂具有不同的金属含量和Pd：Ni原子比（1：1和1：7）。在间歇搅拌釜反应器和连续固定床滴流床反应器中进行苯乙烯选择性加氢成乙苯的催化试验。使用噻吩作为模型毒物，通过相同的操作条件评估了半连续条件下双金属催化剂的抗硫性。载体，Pd-Ni共浸催化剂和LD265商业催化剂的特征还在于N₂化学吸附，EPMA，OM，ICP元素分析，程序升温还原，XPS和X射线衍射。结果表明存在不同的金属种类：Pd ⁰，Pdδ ⁺，Ni ⁰和NiO。发现实验室制备的双金属催化剂对苯乙烯的选择性加氢（间歇和连续系统均具有活性）。在连续评估过程中，商用LD265催化剂的中间活性水平介于对应于Pd-Ni双金属催化剂的值之间：PdNi（1：1）  \（\ gg \） LD265> PdNi（1：7）。在无毒半连续评估过程中，共浸渍的Pd-Ni催化剂的转化模式随接触时间的变化与商用LD265催化剂非常相似，尽管对PdNi（1：1）的催化活性稍好。接触时间90分钟后，转化顺序为：PdNi（1：1）> LD265> PdNi（1：7）。另一方面，在毒物半连续试验（含300 pp噻吩）中，共浸渍催化剂的初始反应速率降低，表明噻吩对活性位点有毒作用。在两种条件下无毒或中毒期间，PdNi（1：1）的初始反应速率均高于PdNi（1：7）。PdNi（1：7）比PdNi（1：1）更耐硫。PdNi（1：1）催化剂的较高活性归因于Pd ⁰的存在和Pd ^{n +} / Ni ^{m +}物种分别有利于氢键的均裂和苯乙烯的吸附。的钯镍的较高耐硫性（1：7）催化剂将具有较高CL /铝表面的原子在该催化剂比（电子效应）和Pd（钯electrodeficient物种的存在相关联_X ^δ+ ö _ý氯_Ž）通过空间位阻（大分子的几何效应）或电子效应阻止了噻吩的吸附。